UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 14A INFORMATION

PROXY STATEMENT PURSUANT TO SECTION 14(a) OF
THE SECURITIES EXCHANGE ACT OF 1934

Dear Sonus Stockholders:

        On behalf of the Board of Directors of Sonus Pharmaceuticals, Inc., we are pleased to deliver this proxy statement and cordially invite you to attend a special meeting of stockholders of Sonus in relation to the proposed acquisition of Synt:em S.A., a company incorporated in France, to be held on                        , 2005.

        The purpose of the special meeting will be the approval of the issuance of that number of shares of our common stock necessary to consummate our proposed acquisition of Synt:em S.A. Sonus is offering to purchase all of the issued and outstanding capital stock of Synt:em S.A. in exchange for shares of our common stock. The acquisition would be effected pursuant to the terms of an Amended and Restated Stock Purchase Agreement executed on December 27, 2004, by and among Sonus, and the stockholders of Synt:em S.A., and certain warrant holders and option holders of Synt:em S.A. The consummation of the transaction will require the issuance of 5,425,000 shares of our common stock deliverable to the stockholders of Synt:em S.A., subject to satisfaction of the conditions described in the Amended and Restated Stock Purchase Agreement.

        We believe this acquisition will help build upon the foundation that we have established with TOCOSOL® Paclitaxel, our lead cancer product, and will help us expand our platform as a pharmaceutical development company. We anticipate the combination of Sonus and Synt:em S.A. will result in a stronger company with a broader product pipeline, expanded drug discovery and development capabilities and increased scientific expertise and resources, all of which we believe will enhance value for our shareholders. This is a milestone step in our ongoing effort to build a company that can generate sustainable value over the long-term with multiple product opportunities. The proposed acquisition reaffirms our confidence in our current product development pipeline, and positions us to take advantage of additional opportunities for future success.

        Approval of the issuance of our common stock requires the affirmative vote of a majority of the shares of our common stock present in person or by proxy at the special meeting and voting thereon, provided that a quorum consisting of a majority of the shares of our common stock entitled to vote is present in person or by proxy.

        This booklet includes notice of the special meeting and the proxy statement. The proxy statement describes the business to be transacted at the special meeting and provides information about us and Synt:em S.A. and our proposed acquisition of Synt:em S.A. that you should consider when you vote your shares. We encourage you to read this proxy statement, which includes important information about the proposed acquisition. The section entitled "Risk Factors" beginning on page    of this proxy statement contains a description of some of the risks that you should consider in evaluating our proposed acquisition of Synt:em S.A.

        Sonus' Board of Directors has unanimously approved the Amended and Restated Stock Purchase Agreement and the issuance of 5,425,000 shares of our common stock, subject to satisfaction of the conditions described in the Amended and Restated Stock Purchase Agreement. ACCORDINGLY, YOUR BOARD OF DIRECTORS UNANIMOUSLY RECOMMENDS THAT YOU VOTE "FOR" APPROVAL OF THE ISSUANCE OF 5,425,000 SHARES OF OUR COMMON STOCK PURSUANT TO THE AMENDED AND RESTATED STOCK PURCHASE AGREEMENT.

        Whether or not you plan to attend the meeting, your vote is very important. Please sign and submit your proxy as soon as possible so that your shares can be voted at the special meeting in accordance with your instructions. You can vote your shares via the Internet, by telephone, or by mailing the enclosed proxy card. Instructions for using these convenient services appear on the instructions on the enclosed proxy card. On behalf of Sonus, we look forward to seeing you at the special meeting and we thank your for your support.

NOTICE OF SPECIAL MEETING OF STOCKHOLDERS
TO BE HELD ON                        , 2005

To the Stockholders of Sonus Pharmaceuticals, Inc.:

        NOTICE IS HEREBY GIVEN that a special meeting of stockholders of Sonus Pharmaceuticals, Inc. will be held at the Hyatt Regency Bellevue, 900 Bellevue Way Northeast, Bellevue, Washington 98004 on                        , 2005, at             a.m. local time.

        The purpose of the Special Meeting will be:

1.

to approve the issuance of 5,425,000 shares of Sonus common stock representing the maximum number of shares issuable in connection our proposed acquisition of Synt:em S.A. pursuant to an Amended and Restated Stock Purchase Agreement executed on December 27, 2004, by and among Sonus, the stockholders of Synt:em S.A. and certain warrant holders and option holders of Synt:em S.A.; and



2.

to transact such other business as may properly come before the special meeting or any adjournment or postponement of the meeting, including, if submitted to a vote of our stockholders, a motion to adjourn or postpone the meeting to another time or place for the purpose of soliciting additional proxies or satisfying the conditions to closing the transaction.

        Please refer to the attached proxy statement, which forms a part of this notice and is incorporated herein by reference, for further information with respect to the business to be transacted at the special meeting.

        Only stockholders of record of Sonus common stock at the close of business on January 27, 2005, referred to as the record date for the Sonus special meeting, or their proxies are entitled to notice of and to vote at this special meeting or any adjournment or postponement of the special meeting. The presence, in person or by proxy, of a majority of the outstanding shares of Sonus common stock will be required to establish a quorum at the special meeting. The affirmative vote of a majority of the votes cast at the meeting (a quorum being present) is required to approve the issuance of Sonus common stock in the transaction.

        Your vote is important. Whether or not you expect to attend the special meeting in person, please complete, sign, date and return the enclosed proxy card as soon as possible to make sure that your shares are represented at the special meeting. Returning the proxy card does not deprive you of your right to attend the special meeting and to vote your shares in person. You may revoke your proxy at any time before it is actually voted at the meeting by; delivering written notice of revocation to Sonus' Secretary at 22026 20^th Avenue SE, Bothell, Washington 98021; submitting a later dated proxy; or attending the special meeting and voting in person. For specific instructions on voting procedures and revocation of proxies, please refer to the section entitled "The Special Meeting" beginning on page    of this proxy statement and the instructions on the proxy card.

        The Sonus board of directors unanimously approved the Amended and Restated Stock Purchase Agreement and the transactions contemplated thereby and unanimously recommends that Sonus stockholders vote "FOR" the issuance of Sonus common stock in the transaction.

Table of Contents

SONUS PHARMACEUTICALS, INC.
22026 20th Avenue S.E.
Bothell, Washington 98021

PROXY STATEMENT

INTRODUCTION

        This proxy statement is being furnished in connection with the solicitation of proxies by the Board of Directors of Sonus Pharmaceuticals, Inc., a Delaware corporation ("Sonus" or the "Company"), for use at its Special Meeting of Stockholders ("Special Meeting") to be held on                        , 2005, at             a.m. local time, at the Hyatt Regency Bellevue, 900 Bellevue Way NE, Bellevue, Washington 98004. This proxy statement and the accompanying proxy are being mailed to stockholders on or about                        , 2005. The Company has engaged the proxy advisory group of Strategic Stock Surveillance, LLC, to assist in the solicitation of proxies and provide related informational support, for a services fee and the reimbursement of customary out-of-pocket expenses that are not expected to exceed $15,000 in the aggregate and will be borne by the Company. It is contemplated that this solicitation of proxies will be made primarily by mail; however, if it should appear desirable to do so in order to ensure adequate representation at the meeting, directors, officers and employees of the Company may communicate with stockholders, brokerage houses and others by telephone, telegraph or in person to request that proxies be furnished and may reimburse banks, brokerage houses, custodians, nominees and fiduciaries for their reasonable expenses in forwarding proxy materials to the beneficial owners of the shares held by them. All expenses incurred in connection with this solicitation shall be borne by the Company. Representatives from Ernst & Young, LLP, the Company's independent registered public accounting firm, are expected to be present at the meeting, will be given the opportunity to make a statement if they wish to do so, and will be able to respond to appropriate questions.

        Stockholders who execute proxies retain the right to revoke them at any time before they are voted. Any proxy given by a stockholder may be revoked or superseded by executing a later dated proxy, by giving notice of revocation to the Secretary, Sonus Pharmaceuticals, Inc., 22026 20^th Avenue SE, Bothell, Washington 98021 in writing prior to or at the meeting or by attending the meeting and voting in person. A proxy, when executed and not so revoked, will be voted in accordance with the instructions given in the proxy. If a choice is not specified in the proxy, the proxy will be voted "FOR" the issuance of common stock.

VOTING SECURITIES

        The shares of common stock, $.001 par value, constitute the only outstanding class of voting securities of the Company. Only the stockholders of the Company of record as of the close of business on January 27, 2005 (referred to as the "Record Date") will be entitled to vote at the meeting or any adjournment or postponement thereof. As of the Record Date, there were            shares of common stock outstanding and entitled to vote. No shares of the Company's preferred stock, $0.001 par value, were outstanding. A majority of shares entitled to vote represented in person or by proxy will constitute a quorum at the meeting. Each stockholder is entitled to one vote for each share of common stock held as of the Record Date. The approval of the issuance of common stock in the acquisition requires the affirmative vote of a majority of the votes cast at the special meeting. Abstentions and broker non-votes are each included in the determination of the number of shares present and voting for the purpose of determining whether a quorum is present, but they will not be voted at the special meeting. Because abstentions and broker non-votes will not be considered votes cast, they will have no effect on the outcome of the proposal.

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SUMMARY

        The following is a summary of information contained in this proxy statement. This summary may not contain all of the information about the acquisition that is important to you. For a more complete description of the acquisition, we encourage you to read carefully this entire proxy statement, including the attached appendices. In addition, we encourage you to read the information incorporated by reference into this proxy statement, which includes important business and financial information about Sonus. You may obtain the information incorporated by reference into this proxy statement without charge by following the instructions in the section entitled "Where You Can Find More Information."

The Companies (see page 70 and 72)

Sonus Pharmaceuticals, Inc.
22026 20^th Avenue SE
Bothell, Washington 98021
(425) 487-9500

        Sonus Pharmaceuticals is focused on the development of novel drugs for the oncology and related markets that may offer improved administration, tolerability, safety and effectiveness. Our business strategy is to (1) develop novel, proprietary formulations of therapeutic drugs utilizing the TOCOSOL drug delivery technology; (2) apply the TOCOSOL® technology platform to additional oncology products and (3) identify and in-license new therapeutic opportunities for the treatment of cancer or related indications to expand the existing pipeline of Sonus. The lead product of Sonus is TOCOSOL Paclitaxel, a novel formulation of the anti-cancer drug paclitaxel.

Synt:em S.A.
Parc Scientifique
Georges Besse
30035 Nimes Cedex 1 France
33 (0) 466-048-666

        Synt:em S.A., based in Nimes, France, is a drug discovery company that uses its proprietary drug design technologies to discover and develop drug transport conjugates for the treatment of pain, cancer and diseases of the central nervous system. Synt:em S.A.'s primary focus is to create new chemical entities by re-engineering existing compounds and improving their pharmacological behavior. Synt:em S.A. uses its technology platform to design short peptide sequences, known as Pep:trans peptides, that are conjugated with clinically validated and other compounds in order to improve the transport of pharmaceutical agents to specific organs and enhance cellular uptake.

The Acquisition (see page 43)

        Sonus and the stockholders of Synt:em S.A. have agreed to the combination of Sonus and Synt:em S.A. under the terms of an Amended and Restated Stock Purchase Agreement as described in this proxy statement. We have attached the Amended and Restated Stock Purchase Agreement as Appendix A to this proxy statement. We encourage you to read the Amended and Restated Stock Purchase Agreement in its entirety.

        Under the terms of the Amended and Restated Stock Purchase Agreement Sonus will purchase all of the outstanding shares of capital stock of Synt:em S.A., as well as all of the shares of capital stock of Synt:em S.A. which are issued pursuant to the exercise of outstanding Synt:em S.A. options or warrants on or before the closing of the acquisition. Upon completion of the acquisition, Synt:em S.A. will become a wholly owned subsidiary of Sonus.

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        According to the Amended and Restated Stock Purchase Agreement, Sonus agreed that it will issue 5,425,000 shares of Sonus common stock and deliver the shares into escrow at the closing, to be released at various times and upon certain conditions as described below to the stockholders of Synt:em S.A. The full amount of the shares will only be delivered if all of the contingent and earn-out consideration is paid. At closing, Sonus will issue shares of Sonus common stock having a value equal to the sum of $8.75 million, plus 864,454 Euros, plus the amount of cash and cash equivalents less debt for borrowed money as of December 31, 2004 of Synt:em S.A., and less the amount of any transaction expenses of Synt:em S.A. paid or payable or reimbursed or reimbursable by Sonus after December 31, 2004. It is estimated that the shares issuable at the closing will have an aggregate market value of approximately $13.8 million. The number of shares of Sonus common stock payable at the closing will be based on the average closing price of Sonus common stock for the 20 consecutive trading days ending two days before the closing date.

        Shares of Sonus common stock payable at the closing will be deposited into an escrow account and will be subject to reduction in the event of an increase in the market price of Sonus common stock after the announcement of one or both of two specified value events relating to TOCOSOL Paclitaxel. If such an event occurs, the number of shares reduced from the shares of Sonus common stock payable at closing will be added to the shares of Sonus common stock comprising the earn-out consideration that may be earned upon the achievement of specified milestones by Synt:em S.A. This reallocation of shares from the closing consideration to the earn-out consideration will be measured by comparing the value of the closing consideration, as calculated using the average closing price for the 20 trading days ending two days prior to closing, to the value of such shares using the average closing price for the 20 trading days after the first public announcement of the material terms of a value event relating to TOCOSOL Paclitaxel. For this purpose, a value event means the public announcement of reaching an agreement with the FDA of the material parameters for Phase 3 testing of TOCOSOL Paclitaxel, or the public announcement of entering into a corporate collaboration agreement relating to TOCOSOL Paclitaxel that includes the payment of material consideration to Sonus. If more than one value event occurs prior to September 30, 2005, the average closing price for the 20 trading days after the announcement of the last event to occur will be used to reallocate shares. If no value event occurs prior to September 30, 2005, then no reallocation will take place. Promptly following the final determination of the number of shares constituting the closing consideration, such shares of Sonus common stock comprising the closing consideration will be distributed to the stockholders of Synt:em S.A.

        An additional issuance of Sonus shares having a value of $500,000 is payable on the date that is 45 business days following the filing of the consolidated audited financial statements of Sonus for the fiscal year ended December 31, 2005 with the SEC, provided no claims for indemnification have been made by Sonus prior to such date.

        The remaining portion of the stock purchase consideration that is not included in the closing consideration or the $500,000 payment described above is payable only upon the achievement of specified milestones on or before eight years following the closing.

Sonus' Reasons for the Acquisition; Recommendation of the Board of Directors (see page 49)

        In reaching its determination to approve the acquisition of Synt:em S.A., and to recommend that the Sonus stockholders vote to approve the issuance of shares of Sonus common stock pursuant to the terms of the Amended and Restated Stock Purchase Agreement, the Sonus Board of Directors identified a number of potential benefits of the proposed acquisition for Sonus and its stockholders, including the combined company's ability to increase its technical platform and pipeline of drug development candidates and broaden the combined company's potential customer base. Synt:em S.A. has a highly efficient discovery program that utilizes a proprietary computer screening process (Acti:map) that effectively reduces time and risk factors. The Synt:em S.A. technology platform is

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synergistic with Sonus' and adds novel approaches to changing the bioavailability of drugs as well as the potential ability to enable selective drug uptake into certain cells and organs. The combined company's product focus will extend beyond oncology into related areas, providing the opportunity to address additional large markets. The acquisition also enhances Sonus' preclinical and discovery expertise, adding a substantial number of Ph.D.'s to the staff. The acquisition also provides Sonus with a European presence that will assist in future and ongoing clinical trial management. The Sonus Board of Directors consulted with the management of Sonus and the legal counsel of Sonus regarding the legal terms of the acquisition, and the financial advisors of Sonus regarding the financial aspects of the acquisition and the fairness, from a financial point of view, of the consideration to be paid by Sonus to the stockholders of Sonus.

        The Sonus Board of Directors unanimously approved the acquisition and recommends that Sonus stockholders vote "FOR" the proposal to issue Sonus common stock pursuant to the Amended and Restated Stock Purchase Agreement.

Stockholders Entitled to Vote; Vote Required (see page 16)

        You can vote at the special meeting if you owned Sonus common stock at the close of business on January 27, 2005, the Record Date for the special meeting. On that date, there were                        shares of Sonus common stock outstanding and entitled to vote. You can cast one vote for each share of Sonus common stock that you owned on that date. Approval of the proposal to issue shares of Sonus common stock pursuant to the Amended and Restated Stock Purchase Agreement requires the affirmative vote of a majority of the total votes cast at the special meeting by holders of Sonus common stock outstanding as of the Record Date provided a quorum is present.

Stockholders Agreement (see page 67)

        Pursuant to the Amended and Restated Stock Purchase Agreement, Synt:em S.A. stockholders who will receive Sonus common stock in the acquisition will be required to enter into a Stockholders Agreement. This agreement will provide certain transfer and other restrictions on the Sonus common stock that will be issued to the Synt:em S.A. stockholders and also provides the Synt:em S.A. stockholders with certain registration rights following the closing. This Stockholders Agreement is attached to this proxy statement as Appendix B.

Employment Agreements (see page 67)

        Pursuant to the Amended and Restated Stock Purchase Agreement, Sonus or Synt:em S.A., as applicable, will enter into employment agreements or modify existing agreements with certain significant employees of Synt:em S.A. which provide for restrictions on competitive activities for a period of 24 months following the consummation of the acquisition and the payment by Synt:em S.A. of a success bonus upon the consummation of the acquisition of Synt:em S.A. by Sonus in the amount of from six to 12 months base salary.

Opinion of the Financial Advisor to Sonus (see page 51)

        On October 22, 2004, Needham & Company, Inc. rendered an oral opinion to the Sonus Board of Directors, subsequently confirmed in writing as of October 22, 2004, that, as of the date of its opinion and based upon and subject to the various considerations set forth in its opinion, the consideration to be issued by Sonus in the acquisition pursuant to the terms and provisions of the original Stock Purchase Agreement entered into on November 3, 2004 was fair, from a financial point of view, to the stockholders of Sonus.

        The full text of the Needham & Company opinion, which sets forth, among other things, assumptions made, procedures followed, matters considered and limitations on the scope of the review

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under taken by Needham & Company in rendering its opinion, is attached as Appendix C to this proxy statement. Sonus stockholders are urged to, and should, read the Needham & Company opinion carefully and in its entirety. The Needham & Company opinion addresses only the fairness, from a financial point of view to the stockholders of Sonus, of the consideration to be paid by Sonus in connection with the transaction as of the date of the Needham & Company opinion, and does not constitute a recommendation to any stockholder as to how such stockholder should vote or act on any matter relating to the acquisition. The Board of Directors of Sonus did not obtain an updated fairness opinion from Needham & Company with respect to the Amended and Restated Stock Purchase Agreement because the Board concluded that the revised terms of the transaction were superior from the standpoint of Sonus as compared to the terms of the original Stock Purchase Agreement.

Escrow and Indemnification (see page 60 and 64)

        Sonus will be entitled to indemnification or a partial reduction in the stock purchase consideration for damages arising from any breach of the representations or warranties or the failure by the stockholders of Synt:em S.A. or the managers, to perform any covenants made by such stockholders or managers. In addition, Sonus has agreed to indemnify the stockholders of Synt:em S.A. for certain damages that arise from any breach by Sonus of its representations or warranties or any failure by Sonus to perform its covenants. Claims for indemnification or reductions of stock purchase consideration are subject to certain limitations of time and amount. If claims are submitted more than 45 business days following the filing of the consolidated audited financial statements of Sonus for the fiscal year ended December 31, 2005 with the SEC, recoverable amounts are limited further. Generally, claims for damages or reduction of stock purchase consideration must be submitted prior to the date that is 18 months following the closing date of the proposed stock purchase.

        The parties have agreed that a portion of the stock purchase consideration will be deposited into a third-party escrow to secure obligations under the Amended and Restated Stock Purchase Agreement. Portions of the stock purchase consideration deposited into escrow will include shares of Sonus common stock securing claims for indemnification, shares of Sonus common stock representing the value of a research tax credit payable by the French tax authorities in the first half of 2005 in the amount of 864,454 Euros, and shares of Sonus common stock that may be issued under the terms of the Amended and Restated Stock Purchase Agreement upon the achievement of specified milestones.

Listing of Sonus Common Stock (see page 57)

        Sonus common stock is currently traded on the Nasdaq National Market under the symbol "SNUS." Pursuant to the Amended and Restated Stock Purchase Agreement, Sonus will prepare and file, within five business days following the closing of the acquisition, a Registration Statement on Form S-3 with respect to the resale of the shares issued by Sonus in connection with the acquisition.

        However, pursuant to the Amended and Restated Stock Purchase Agreement, Synt:em S.A. stockholders who will receive Sonus common stock in the acquisition will be required to enter into a Stockholders Agreement that will provide certain transfer and other restrictions on the Sonus common stock issued to them.

No Appraisal Rights (see page 77)

        Sonus stockholders are not entitled to dissenters' or appraisal rights in connection with the acquisition.

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Conditions to Completion of the Acquisition (see page 63)

        In order to complete the acquisition, Sonus and Synt:em S.A. must satisfy a number of conditions, including, but not limited to, the following:

•

no governmental agency or court must have issued any order, decree, judgment or injunction that prevents or prohibits the completion of the acquisition or any other transaction contemplated by the Amended and Restated Stock Purchase Agreement;



•

Sonus stockholders must approve the issuance of Sonus common stock pursuant to the Amended and Restated Stock Purchase Agreement;



•

Sonus and Synt:em S.A. must enter into an Escrow Agreement pursuant to the terms of the Amended and Restated Stock Purchase Agreement; and



•

since the date of the Amended and Restated Stock Purchase Agreement, no event must have occurred that has a material adverse effect on Sonus or Synt:em S.A.

No Solicitation by Synt:em S.A. (see page 64)

        The stockholders of Synt:em S.A. have agreed that neither they nor Synt:em S.A. will solicit, encourage, negotiate or accept any other acquisition proposal for Synt:em S.A. and that they will notify Sonus of any inquiry, indication of interest or proposal that constitutes, or could reasonably be expected to lead to, such an acquisition proposal. The stockholders of Synt:em S.A. have agreed they will not permit the officers, directors, employees, agents, and other representatives of Synt:em S.A. to supply any third-party with any information which could reasonably be expected to lead to an acquisition proposal, nor initiate, solicit, encourage negotiate, accept or discuss any transaction that could reasonably be expected to impede, interfere with, prevent or materially delay the acquisition of Synt:em S.A. by Sonus.

Termination of the Amended and Restated Stock Purchase Agreement (see page 65)

        Sonus and the sellers' agent appointed by the stockholders of Synt:em S.A. can jointly agree to terminate the Amended and Restated Stock Purchase Agreement at any time by mutual agreement. Either company may also terminate the Amended and Restated Stock Purchase Agreement if the acquisition is not completed by February 28, 2005.

Transaction Expenses (see page 61)

        Subject to the limitation described below, Sonus has agreed to pay all of the transaction expenses incurred by Synt:em S.A. and the Synt:em S.A. stockholders, including fees and expenses of legal advisors, accountants, investment bankers, financial advisors, valuation firms or similar professionals, as well as all bonuses, success fees and severance payments to employees of Synt:em S.A. that are payable as a result of the stock purchase, in addition to the stock purchase consideration. However, the amount of the transaction expenses of Synt:em S.A. and the Synt:em S.A. stockholders paid or reimbursed by Sonus will reduce the amount of the closing consideration to be paid by Sonus, and will increase, by a corresponding amount, the contingent earn-out amounts payable by Sonus based upon achievement of the milestone events. In addition, the transaction expenses paid or reimbursed by Sonus will have the effect of reducing the amount of cash held by Sonus. In no event will the transaction expenses payable by Sonus exceed 1.72 million Euros.

United States Federal Income Tax Consequences of the Acquisition (see page 56)

        There are no material U.S. federal income tax consequences to our current stockholders that will result from our issuance of additional shares of our common stock in the acquisition.

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Anticipated Accounting Treatment (see page 56)

        The acquisition will be accounted for as a "purchase" transaction for accounting and financial reporting purposes, in accordance with accounting principles generally accepted in the United States. After the transaction, the results of operations of Synt:em S.A. will be included in the consolidated financial statements of Sonus. The purchase price will be allocated based on the fair values of the assets acquired and the liabilities assumed. Pursuant to Statements of Financial Accounting Standards No. 141, "Business Combinations" and No. 142, "Goodwill and Other Intangible Assets," goodwill will be subject to at least annual assessment for impairment based on a fair value test. Identified intangible assets with finite lives are amortized over those lives. A final determination of the intangible asset values and required purchase accounting adjustments, including the allocation of the purchase price to the assets acquired and liabilities assumed based on their respective fair values, has not yet been made. Sonus will determine the fair value of assets and liabilities and will make appropriate business combination accounting adjustments. However, for purposes of disclosing unaudited pro forma information in this proxy statement, Sonus has made a preliminary determination of the purchase price and the purchase price allocation, based upon current estimates and assumptions, which is subject to revision upon consummation of the transaction.

Governmental and Regulatory Matters (see page 56)

        Sonus and Synt:em S.A. will comply with applicable federal and state securities laws in connection with the issuance of the Sonus common stock pursuant to the acquisition, and with applicable provisions of Delaware law. Except for applicable filings with the U.S. Securities and Exchange Commission and the approval of our stockholders as described in this proxy statement, no federal or state or French regulatory filings, consents or approvals will be required to consummate the acquisition.

Forward Looking Statements May Prove Inaccurate

        Sonus has made forward-looking statements in this document (and in documents that are incorporated herein by reference) that are subject to risks and uncertainties. Forward-looking statements include expectations concerning matters that are not historical facts. Also, when we use words such as "believe," "expect," "anticipate" or similar expressions, we are making forward-looking statements. For more information regarding factors that could cause actual results to differ from these expectations, you should refer to the specific risks described under "Risk Factors" beginning on page 31 and to the documents referred to under "Documents Incorporated by Reference" on page 80.

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QUESTIONS AND ANSWERS ABOUT THE
ACQUISITION AND THE SPECIAL MEETING

        This section highlights selected information from this proxy statement and may not contain all of the information that is important to you. To better understand the proposed transactions, you should read this entire proxy statement carefully, as well as those additional documents to which we refer you. You may obtain more information by following the instructions in the section captioned "Where You Can Find More Information" on page 79. We have included page references to direct you to more complete descriptions of the topics presented in this section.

QUESTIONS AND ANSWERS ABOUT THE ACQUISITION

Why am I receiving this proxy statement?

        Sonus and the stockholders of Synt:em S.A. have agreed to combine the businesses of the two companies in a strategic transaction under which Sonus will acquire all of the outstanding shares of Synt:em S.A. This transaction will be effected through the purchase of all of Synt:em S.A.'s shares pursuant to an Amended and Restated Stock Purchase Agreement, entered into on December 27, 2004, by and among Sonus and the stockholders of Synt:em S.A. and certain warrant holders and option holders of Synt:em S.A. The Amended and Restated Stock Purchase Agreement supersedes in its entirety the Stock Purchase Agreement entered into by the same parties on November 3, 2004.

Why are Sonus and Synt:em S.A. proposing this transaction?

        Sonus and the stockholders of Synt:em S.A. believe the acquisition will provide substantial strategic benefits to the stockholders of both companies. Sonus and Synt:em S.A. believe the combination will enhance the combined company's technical platform and pipeline of drug development candidates and will broaden the combined company's potential customer base. For a more detailed description of the reasons of Sonus for the acquisition, please see the section captioned "The Acquisition—Sonus Reasons for the Acquisition" on page 49 of this proxy statement.

What information is contained in these materials?

        The information included in this proxy statement relates to the proposal to be voted on at the special meeting of stockholders of Sonus related to the issuance of shares for the proposed acquisition of Synt:em S.A., along with information on the voting process and where to find additional information. Also included are audited financial statements of Synt:em S.A., pro forma condensed combined financial information for Sonus and Synt:em S.A. related to the proposed acquisition, a proxy card and a return envelope.

Why are Sonus stockholders being asked to approve the issuance of shares of common stock?

        We are proposing to combine with Synt:em S.A. by offering to purchase, all of the outstanding shares of Synt:em S.A. with the consideration comprised of shares of our common stock. We will issue 5,425,000 shares of our common stock, or approximately 25% of our total shares of common stock outstanding on the date of the Amended and Restated Stock Purchase Agreement, to Synt:em S.A. stockholders. The total number of shares issued and delivered will be contingent on certain adjustments and earn-out payments provided for under the terms of the Amended and Restated Stock Purchase Agreement.

        The Nasdaq Marketplace Rules require the approval of our stockholders prior to the issuance of additional shares of our common stock in any transaction if (1) the common stock has, or will have upon issuance, voting power in excess of 20% of the voting power outstanding before the issuance of such common stock or of securities convertible into or exercisable for common stock or (2) the number

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of shares of common stock to be issued is, or will be upon issuance, in excess of 20% of the number of shares of common stock outstanding before the issuance of the common stock or of securities convertible into or exercisable for common stock. In calculating shares outstanding, we have assumed the issuance of all shares contemplated by the Amended and Restated Stock Purchase Agreement, including shares issued as a result of contingent milestone payments being paid. Therefore, your approval is required.

What are the terms of the Acquisition to Synt:em S.A. stockholders?

        According to the Amended and Restated Stock Purchase Agreement, Sonus agreed that it will issue 5,425,000 shares of Sonus common stock into escrow for the benefit of the stockholders of Synt:em S.A. Sonus shares issuable in connection with the transaction are deliverable to the stockholders of Synt:em S.A. in three installments, the first of which is payable at the closing, subject to the reallocation mechanism described in further detail below, the second of which is payable after filing of Sonus' audited financial statements with the SEC for fiscal year 2005 and the third of which is payable upon the achievement of certain milestones by Synt:em S.A. The maximum number of shares will only be issued and delivered if the earn-out milestones are achieved. Euro denominated values will be converted into U.S. Dollars at the applicable exchange rate on the day immediately prior to the date of closing.

        Shares of Sonus common stock payable at closing will be deposited into an escrow account and will be subject to reduction and reallocation to the common stock comprising the earn-out consideration in the event of an increase in the market price of Sonus common stock after the announcement of one or both of two specified value events relating to TOCOSOL Paclitaxel. For a more detailed description of the terms of the consideration to be paid to Synt:em S.A. stockholders, please see the section captioned "The Amended and Restated Stock Purchase Agreement—Stock Purchase Consideration" on page 58 of this proxy statement.

Are there any conditions to this proposed transaction?

        The consummation of the acquisition is conditioned, among other things, upon the following: (1) approval by our stockholders of the issuance of 5,425,000 shares of our common stock to Synt:em S.A. stockholders, subject to satisfaction of the conditions described in the Amended and Restated Stock Purchase Agreement, and (2) there has been no material adverse change in the condition of Sonus or Synt:em S.A. For a more detailed description of the conditions to the Acquisition, please see the section captioned "The Amended and Restated Stock Purchase Agreement—Conditions to the Acquisition."

Are there risks associated with this proposed transaction?

        Yes. The combined company may not achieve the expected benefits of this transaction because of the risks and uncertainties discussed in the section entitled "Risk Factors" beginning on page 31 of this proxy statement. In deciding whether to approve the issuance of additional shares of our common stock in connection with acquisition, we urge you to carefully read and consider the risk factors contained in the section captioned "Risk Factors."

How much of Sonus will current Synt:em S.A. stockholders own upon completion of the Acquisition?

        Following the completion of the acquisition, we estimate that Synt:em S.A. stockholders will hold approximately 20% of our outstanding common stock, based on shares outstanding as of the Record Date. The maximum number of shares issuable under the terms of the Amended and Restated Stock Purchase Agreement will only be issued if the earn-out milestones are achieved.

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How does the Board of Directors of Sonus recommend that I vote?

        The Board of Directors of Sonus unanimously recommends that all stockholders vote "FOR" the proposal to approve the issuance of 5,425,000 shares of Sonus common stock to Synt:em S.A. stockholders, subject to satisfaction of the conditions described in the Amended and Restated Stock Purchase Agreement, in connection with the proposed acquisition of Synt:em S.A.

Why is the Board of Directors recommending that I vote for the issuance?

        To review the background of and reasons for the acquisition and the issuance of shares in connection with the acquisition, please see the section captioned "The Acquisition—Background of the Acquisition" on page 43, and "Reasons for the Acquisition" on page 49.

Was there a Fairness Opinion delivered to Sonus in connection with this transaction?

        In connection with the proposed transaction, the financial advisor of Sonus, Needham and Company, Inc. delivered a written opinion to the Board of Directors of Sonus as to the fairness to the stockholders of Sonus, from a financial point of view, of the consideration provided for in the Stock Purchase Agreement dated as of November 3, 2004 regarding the acquisition of Synt:em S.A. The full text of Needham's written opinion, dated October 22, 2004, is attached to this proxy statement as Appendix C. We encourage you to read this opinion carefully in its entirety for a description of the procedures followed, assumptions made, matters considered and limitations on the review undertaken. The Board of Directors of Sonus did not obtain an updated fairness opinion from Needham & Company with respect to the Amended and Restated Stock Purchase Agreement because the Board concluded that the revised terms of the transaction were superior from the standpoint of Sonus as compared to the terms of the original Stock Purchase Agreement.

        NEEDHAM'S OPINION IS ADDRESSED TO THE BOARD OF DIRECTORS OF SONUS AND DOES NOT CONSTITUTE A RECOMMENDATION TO ANY STOCKHOLDER AS TO HOW SUCH STOCKHOLDER SHOULD VOTE WITH RESPECT TO THE ISSUANCE OF THE ADDITIONAL SHARES OF OUR COMMON STOCK RELATED TO THE ACQUISITION OR ANY OTHER MATTER.

Are there any material United States federal income tax consequences to Sonus' stockholders from the stock issuance or the proposed Acquisition?

        There are no material U.S. federal income tax consequences to our current stockholders that will result from our issuance of additional shares of our common stock in the acquisition.

How will the proposed acquisition of Synt:em S.A. be accounted for?

        The proposed acquisition of Synt:em S.A. will be accounted for using the purchase method of accounting following accounting principles generally accepted in the United States. For a more detailed discussion of the anticipated accounting treatment, please see the section captioned "The Acquisition—Anticipated Accounting Treatment" on page 56 of this proxy statement.

Are there any regulatory approvals required in connection with proposed acquisition?

        The issuance of shares of our common stock are subject to the approval of our stockholders as described in this proxy statement. No other regulatory approvals are required in connection with the proposed acquisition.

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When do you expect the Acquisition to be completed?

        We currently anticipate that the acquisition will be completed on or about                             , 2005. However, the exact timing of the completion of the acquisition cannot be predicted because it is subject to stockholder approval and other conditions described in this proxy statement.

Are the stockholders of Sonus entitled to dissenters' rights?

        No. Under Delaware law and our Amended and Restated Certificate of Incorporation, holders of shares of Sonus, common stock are not entitled to any dissenters' rights to seek appraisal of their shares, or to any preemptive rights, in connection with the proposed acquisition.

QUESTIONS AND ANSWERS ABOUT THE SPECIAL MEETING

When and where will the special meeting be held and what business will occur at the meeting?

        Our special meeting of stockholders will be held at the Hyatt Regency Bellevue, 900 Bellevue Way Northeast, Bellevue, Washington, 98004, on                         , 2005, at         a.m. local time. At the special meeting, stockholders will consider and vote upon the issuance of 5,425,000 shares of our common stock in connection with the proposed acquisition of all the outstanding shares of Synt:em S.A. You do not need to be present at the special meeting to have your vote counted. By utilizing any one of the various voting procedures described in this proxy statement prior to the date of the special meeting, your vote will be counted and included in the final results.

Who may vote at the special meeting?

        The shares of common stock of Sonus constitute the only class of securities entitled to notice of, to attend and to vote at the special meeting of stockholders. Only stockholders of record at the close of business on January 27, 2005, the Record Date for the meeting, are entitled to receive notice of and to participate in the special meeting. As of January 27, 2005 there were                        shares of common stock issued and outstanding. If you were a stockholder of record on that date, you will be entitled to vote all of the shares that you held on that date at the meeting, or any postponements or adjournments of the meeting. Each outstanding share of Sonus common stock will be entitled to one vote on each matter.

        As of the Record Date, the directors, executive officers and affiliates of Sonus held            shares of Sonus common stock.

What is the difference between holding shares as a stockholder of record or as a beneficial owner?

        Most stockholders of Sonus hold their shares through a stockbroker, bank or other nominee rather than directly in their own name. As summarized below, there are some distinctions between shares held of record and those owned beneficially.

Stockholder of Record

        If your shares are registered directly in your name with the transfer agent of Sonus, U.S. Stock Transfer Corporation, you are considered, with respect to those shares, the stockholder of record, and these proxy materials are being sent directly to you by Sonus. As the stockholder of record, you have the right to grant your voting proxy directly to Sonus or to vote in person at the special meeting. Sonus has enclosed a proxy card for you to use.

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Beneficial Owner

        If your shares are held in a stock brokerage account or by a bank or other nominee, you are considered the beneficial owner of shares held in street name, and these proxy materials are being forwarded to you by your broker or nominee who is considered, with respect to those shares, the stockholder of record. As the beneficial owner, you have the right to direct your broker on how to vote and are also invited to attend the special meeting. Your broker or nominee has enclosed a voting instruction card for you to use in directing the broker or nominee regarding how to vote your shares. The voting instruction card provides various alternative voting methods, such as via the Internet, by telephone or by mail.

How many votes may a stockholder cast?

        At the special meeting, each stockholder will be entitled to one vote per share of common stock owned by such stockholder as of the record date.

How can I vote my shares in person at the special meeting?

        Shares held directly in your name as the stockholder of record may be voted in person at the special meeting. If you choose to do so, please bring the enclosed proxy card and proof of identification. Even if you plan to attend the special meeting, we recommend that you also submit your proxy as described below so that your vote will be counted if you later decide not to attend the special meeting. Shares held in street name may be voted in person by you only if you obtain a signed proxy from the record holder giving you the right to vote the shares in person.

How can I vote my shares without attending the special meeting?

        Whether you hold shares directly as the stockholder of record or beneficially in street name, you may direct your vote without attending the special meeting. You may vote your directly held shares by granting a proxy or, for shares held in street name, by submitting voting instructions to your broker, bank or nominee following the instructions on the form included with this package.

What vote is required to approve the proposal?

        In order to conduct business at the special meeting, a quorum must be present. The holders of a majority of the shares of common stock entitled to vote at the special meeting, either present in person or represented by proxy, constitutes a quorum under the bylaws of Sonus and Delaware law. We will treat shares of our common stock represented by a properly signed and returned proxy, including abstentions and broker non-votes, as present at the special meeting for the purposes of determining the existence of a quorum. If a quorum is not present, it is expected that the special meeting will be adjourned or postponed to solicit additional proxies.

        The approval of the issuance of common stock in the acquisition requires the affirmative vote of a majority of the votes cast at the special meeting, provided a quorum is present. Although abstentions and broker non-votes will be counted for the purpose of determining whether a quorum is present, they will not be counted as votes cast at the special meeting. Broker non-votes refer to unvoted proxies submitted by brokers who are not able to vote on a proposal absent instructions from the applicable beneficial owner. Because abstentions and broker non-votes will not be considered votes cast, they will have no effect on the outcome of the proposal.

What does it mean if I receive more than one proxy or voting instruction card?

        It means that your shares are registered differently or are in more than one account. Please provide voting instructions for all proxy and voting instruction cards you receive.

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May I change my vote after I have given it?

        You may change your proxy instructions (and your vote) at any time prior to the vote at the special meeting. For shares held directly in your name, you may accomplish this by granting a new proxy bearing a later date (which automatically revokes the earlier proxy) and delivering such new proxy to the Secretary of Sonus either by mail or by calling the phone number or accessing the Internet address listed on the proxy card or by attending the special meeting and voting in person. Attendance at the special meeting will not cause your previously granted proxy to be revoked unless you specifically request to do so. For shares held beneficially by you, you may accomplish this by submitting new voting instructions to your broker, bank or nominee.

Who bears the cost of soliciting proxies?

        We will pay the entire cost of preparing, assembling, printing, mailing and distributing these proxy materials. In addition to the mailing of these proxy materials, the solicitation of proxies or votes may be made in person, by telephone or by electronic communication by our directors, officers, and employees, who will not receive any additional compensation for such solicitation activities. We have retained the services of Strategic Stock Surveillance, LLC, to aid in the solicitation of proxies from banks, brokers, nominees and intermediaries. We estimate that we will pay Strategic Stock Surveillance a fee not expected to exceed $15,000 for its services, plus out of pocket expenses. We will also reimburse brokerage firms and other persons representing beneficial owners of shares for their expenses in forwarding solicitation material to such beneficial owners.

How are votes counted?

        You may vote "FOR", "AGAINST" or "ABSTAIN." If you sign your proxy card or broker voting instruction card with no further instructions, your shares will be voted in accordance with the recommendations of the Board of Directors of Sonus described in this proxy statement. Unless you give other instructions on your proxy card, the persons named as proxy holders on the proxy card will vote in accordance with the recommendations of the Board of Directors. With respect to any other matter that properly comes before the meeting, the proxy holders will vote as recommended by the Board of Directors or, if no recommendation is given, in their own discretion.

If my shares are held in "street name" by my broker, will my broker vote my shares for me?

        Your broker will vote your shares only if you provide instructions on how to vote. Included with this package, you should have received from your broker a voting instruction card with instructions on how to vote your shares and how to provide instructions to your broker on how you want your shares voted. If you have any questions regarding the procedures necessary for your broker to vote your shares, you should contact your broker directly. Please instruct your broker as to how you would like him or her to vote your shares following the procedures on the instruction card. If you do not instruct your broker how to vote your shares, your shares will not be voted by your broker.

What do Sonus stockholders need to do now?

        After carefully reading and considering the information contained in this proxy statement, you should either complete, sign and date your proxy card and voting instructions and return them in the enclosed postage-paid envelope, by phone or by the Internet as provided for on the voting instruction card included in this package, or vote in person at the special meeting. You can simplify your voting and save Sonus expense by either voting via the Internet or calling the toll-free number listed on the proxy card. Please vote your shares as soon as possible so that your shares will be represented at the special meeting.

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Where can I find the voting results of the special meeting?

        We will announce preliminary voting results at the special meeting and we will issue a press release with the final results after the special meeting is completed. In addition, we will publish the final results in a current report filed on Form 8-K following the special meeting.

What will happen if the proposal is not approved?

        If the proposal is not approved, the acquisition of Synt:em S.A. cannot proceed because we cannot issue the requisite number of shares of our common stock under applicable Nasdaq Marketplace Rules to complete the acquisition.

Who can help answer my questions?

        If you have any questions about the acquisition of Synt:em S.A. or how to vote or revote your proxy, or if you need additional copies of this proxy statement, you should contact Alan Fuhrman, the Chief Financial Officer of Sonus, at 22026 20th Avenue SE, Bothell, Washington 98021, or by telephone at (425) 487-9500.

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THE SPECIAL MEETING

Date, Time, Place and Purpose of the Special Meeting

The special meeting will be held as follows:

The special meeting will be held for the following purposes:

1.

to approve the issuance of 5,425,000 shares of Sonus common stock representing the maximum number of shares issuable in connection with our proposed acquisition of the outstanding shares of Synt:em S.A. pursuant to an Amended and Restated Stock Purchase Agreement, entered into on December 27, 2004, by and among Sonus, the stockholders of Synt:em S.A. and certain warrant holders and option holders of Synt:em S.A.; and



2.

to transact such other business as may properly come before the special meeting or any adjournment or postponement of the meeting, including, if submitted to a vote of our stockholders, a motion to adjourn or postpone the meeting to another time or place for the purpose of soliciting additional proxies or satisfying the conditions to closing the transaction.

        A copy of the Amended and Restated Stock Purchase Agreement is attached to this proxy statement as Appendix A.

Recommendation of the Board of Directors

        Our Board of Directors believes that the proposed issuance of common stock in connection with the acquisition of Synt:em S.A. is advisable and fair to, and in the best interests of, Sonus and its stockholders, and unanimously recommends that stockholders vote "FOR" the proposal.

Voting Procedures and Revocations of Proxies

        A proxy card is enclosed for your use. We ask that you sign, date and return the proxy card in the accompanying envelope, which is postage prepaid if you mail it in the United States. Unless there are different instructions on the proxy, all shares represented by valid proxies (and not revoked before they are voted) will be voted at the special meeting "FOR" the approval of the issuance of common stock pursuant to the Amended and Restated Stock Purchase Agreement. With respect to any other business that may properly come before the special meeting and be submitted to a vote of stockholders, proxies will be voted in accordance with the best judgment of the designated proxy holders.

        Stockholders of record may vote by completing and returning the enclosed proxy card or calling the phone number or accessing the Internet address listed on the proxy card prior to the special meeting, voting in person at the special meeting, or submitting a signed proxy card at the special meeting. Your vote is important. Accordingly, please sign, date and return the accompanying proxy card whether or not you plan to attend the special meeting in person.

        You may revoke your proxy at any time before it is actually voted at the meeting by:

•

delivering written notice to our Secretary at 22026 20th Avenue SE, Bothell, Washington 98021,



•

calling the phone number or accessing the Internet address listed on the proxy card with instructions to revoke your proxy,

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•

submitting a later dated proxy, or



•

attending the special meeting and voting in person.

        Your attendance at the special meeting will not, by itself, constitute revocation of your proxy. You may also be represented by another person present at the special meeting by executing a form of proxy designating that person to act on your behalf. Shares may only be voted by or on behalf of the record holder of shares as indicated in our stock transfer records. If you are a beneficial owner but your shares are held of record by another person, such as a stock brokerage firm or a bank, that person must vote the shares as the record holder in accordance with the beneficial holder's instructions. All votes cast at the special meeting will be tabulated by the persons appointed by us to act as inspectors of election for the special meeting.

Record Date and Shares Entitled to Vote

        Each stockholder of record at the close of business on January 27, 2005 (the "Record Date"), will be entitled to one vote for each share of common stock. On the Record Date, there were                        shares of common stock issued and outstanding. These stockholders are entitled to cast one vote for each share of common stock held as of the Record Date on all matters properly submitted for the vote of stockholders at the special meeting.

Quorum and Vote Required

        A quorum of stockholders is necessary to hold a valid special meeting. The presence, in person or by proxy of the holders of a majority of the shares of common stock issued and outstanding and entitled to be voted at the special meeting is necessary to constitute a quorum at the special meeting. The approval of the issuance of common stock in the acquisition requires the affirmative vote of the majority of the votes cast at the special meeting assuming a quorum is present.

Abstentions and Broker Non-Votes

        Abstentions and broker non-votes will be counted for the purpose of determining whether a quorum is present, but they will not be voted at the special meeting. Broker non-votes refer to unvoted proxies submitted by brokers who are not able to vote on a proposal absent instructions form the applicable beneficial owner. Because abstentions and broker non-votes will not be considered votes cast, they will have no effect on the outcome of the proposal.

Solicitations of Proxies and Expenses

        This solicitation is made on behalf of our Board of Directors and we will pay the costs of soliciting and obtaining the proxies, including the costs of reimbursing banks and brokers for forwarding proxy materials to their principals. Strategic Stock Surveillance, LLC, has been engaged to assist in the distribution and solicitation of proxies, and will be paid reasonable fees and expenses for its services. Proxies may be solicited, without extra compensation, by the our directors, officers and employees by mail, telephone, fax, personal interviews or other methods of communication. We will not pay any additional compensation to directors, officers or other employees for such services, but may reimburse them for reasonable out-of-pocket expenses in connection with the solicitation.

Admission to the Special Meeting

        Only stockholders as of the close of business on the Record Date and other persons holding valid proxies for the special meeting are entitled to attend the special meeting. Stockholders and their proxies should be prepared to present valid government issued photo identification. Stockholders who are not record holders but hold shares through a broker or nominee (i.e., in street name) should

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provide proof of beneficial ownership on the Record Date for the special meeting, such as their most recent account statement prior to the Record Date, or other similar evidence of ownership. Anyone who does not provide valid government issued photo identification or comply with the other procedures outlined above upon request may not be admitted to the special meeting.

Other Business

        As of the date of this proxy statement, our Board of Directors does not know of any matter that will be presented for consideration at the special meting other than as described in this proxy statement. However, if any matters are properly presented at the special meeting or any adjournment or postponement of the special meeting, including, if submitted to a vote of our stockholders, a motion to adjourn or postpone the meeting to another time or place for the purpose of soliciting additional proxies or satisfying the conditions to closing the acquisition, the persons named as proxies will be granted discretionary authority with respect to such matter.

Assistance

        If you need assistance in completing your proxy card or have questions regarding the special meeting please contact Alan Furhman, our Chief Financial Officer, at 22026 20th Avenue SE, Bothell, Washington 98021 or by telephone at (425) 487-9500.

        YOUR VOTE IS IMPORTANT. WHETHER OR NOT YOUR PLAN TO ATTEND THE SPECIAL MEETING IN PERSON, PLEASE SIGN, DATE AND RETURN THE ACCOMPANYING PROXY CARD.

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SELECTED HISTORICAL FINANCIAL DATA OF SONUS

        The following table sets forth a summary of selected historical consolidated financial data of Sonus for the periods indicated. This information is derived from, and should be read in conjunction with, the audited consolidated financial statements of Sonus. The operating results for the periods indicated are not necessarily indicative of the results for any future period. See the section "Where You Can Find More Information" on page 79.

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SELECTED HISTORICAL FINANCIAL DATA OF SYNT:EM S.A.

        The following tables set forth a summary of selected historical financial data of Synt:em S.A. presented in Euros, for the periods indicated. This information is derived from, and should be read in conjunction with, the audited financial statements of Synt:em S.A. This information has been prepared in accordance with generally accepted accounting principles in France, or "French GAAP". The tables also set forth for the two year period ended December 31, 2003 and for the unaudited nine month periods ended September 30, 2003 and September 30, 2004, a summary of selected historical financial data of Synt:em S.A. presented in conformance with U.S. GAAP. For a quantitative reconciliation of net (loss) and stockholders' equity to U.S. GAAP, and a discussion of significant differences between French GAAP and U.S. GAAP as they relate to the Synt:em S.A. financial statements, please refer to Note 20 of the notes to the Synt:em S.A. financial statements for the year ended December 31, 2003 included elsewhere in this proxy statement. The accompanying financial statments have been prepared assuming Synt:em S.A. will continue as a going concern. We draw your attention to the significant uncertainty described in note 1 of the notes to the Synt:em S.A. financial statments, which raises substantial doubt about Synt:em S.A.'s ability to continue as a going concern. The operating results for the periods indicated are not necessarily indicative of the results for any future period.

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EXCHANGE RATE INFORMATION

        Unless otherwise indicated, all dollar amounts in this proxy statement are expressed in U.S. Dollars. The following table shows the rates of exchange for one Euro per U.S. Dollar in effect at the end of certain periods. At January 19, 2005, the exchange rate was 1.3036 Euros for one U.S. Dollar. The high and low rates of exchange for the periods and the average rate of exchange for the periods are also shown.

        In this proxy statement, amounts stated in U.S. Dollars and derived from Euros and amounts stated in Euros and derived from U.S. Dollars, unless otherwise indicated, have been translated at a fixed rate, solely for convenience. These translations should not be construed as a representation by Sonus that Euro amounts actually represent these U.S. Dollar amounts, or vice versa, or that a conversion could be made at the rate indicated, or any other rate, or at all. Certain amounts and percentages included in this proxy statement have been rounded and accordingly may not add up to the totals.

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SELECTED UNAUDITED PRO FORMA CONDENSED COMBINED FINANCIAL DATA

        The following selected unaudited pro forma combined financial data of Sonus and Synt:em S.A. were derived from the financial statements of Sonus and Synt:em S.A. and should be read in conjunction with these financial statements and the unaudited pro forma condensed combined financial statements and related notes thereto included or incorporated by reference in this proxy statement. For purposes of the selected unaudited pro forma combined financial data, Synt:em S.A. financial information has been translated into U.S. Dollars and is based on U.S. GAAP. The Synt:em S.A. amounts combined in the pro forma combined financial statements were translated to U.S. Dollars using a spot rate of 1.24174 as of September 30, 2004 and an average rate of 1.22284 and 1.11926 for the nine months ended September 30, 2004 and the year ended December 31, 2003, respectively.

        The selected unaudited pro forma combined operations data for the year ended December 31, 2003 gives effect to the acquisition as if it occurred on January 1, 2003, the first day of the period. The selected unaudited pro forma combined operations data for the nine month period ended September 30, 2004 gives effect to the acquisition as if it occurred on January 1, 2004, the first day of the period. The selected unaudited pro forma combined balance sheet data gives effect to the acquisition as if it occurred on September 30, 2004. The selected unaudited pro forma combined financial data is based on estimates and assumptions that are preliminary and does not purport to represent what the results of operations or financial position of Sonus actually would have been if the acquisition had been consummated on the date or for the period indicated or what such results will be for any future date or period. Investors are cautioned not to place undue reliance on this unaudited pro forma financial information.

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MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND
RESULTS OF OPERATIONS—SYNT:EM S.A.

        The following discussion should be read in conjunction with the financial statements of Synt:em S.A. and the notes thereto included elsewhere in this proxy statement. Synt:em S.A.'s financial statements and the financial information discussed herein have been prepared in accordance with French GAAP, which differs in certain material respects from U.S. GAAP. For a discussion of the principle differences between French GAAP and U.S. GAAP, see note 20 of the notes to the financial statements of Synt:em S.A. for the year ended December 31, 2003. The financial statements referred to in the preceding sentence also refer to Synt:em S.A.'s ability to continue as a going concern; please refer to Note 1.

Business Overview

        Synt:em S.A. is a drug discovery company developing novel drugs using its proprietary drug design technologies to discover and develop drug transport conjugates. Synt:em S.A.'s principal focus is to create new chemical entities by re-engineering existing compounds and improving their pharmacological behavior in order to improve the transport of pharmaceutical agents to specific organs and enhance cellular uptake.

        Synt:em S.A. utilizes two proprietary technologies to pursue the discovery and development of new chemical entities (NCEs): Pep:trans and Acti:map.

Pep:trans

        Pep:trans is a family of rationally designed, proprietary, peptides that can enable the transport of drugs across biological membranes and bring them more efficiently to their site of pharmacological action. Synt:em S.A. creates small proprietary peptides that are designed to transport drugs across targeted membranes or into particular cells including cancer cells.

Acti:map

        Acti:map is an activity-driven, knowledge-based, computational discovery process, which consists of mapping, in a relevant multi-dimensional property space, molecules sharing a given activity to identify and optimize novel drug candidates. Acti:map is Synt:em S.A.'s design and optimization process that includes proprietary algorithms, software, know-how and analysis coupled with commercially available software and tools.

        Synt:em S.A.'s market focus is in the areas of pain, cancer, and diseases of the central nervous system. Synt:em S.A. has two compounds in pre-clinical trials and is conducting Phase 1 studies on a third compound.

Results of Operations

Period ending September 30, 2004 (unaudited) and September 30, 2003 (unaudited)

        Revenues for the nine month period ending September 30, 2004 were €0.1 million. Revenues for the nine month period ending September 30, 2003 were €0.4 million. The decrease in 2004 was due to the anticipated end of a three year, third party service contract that was signed in 2001.

        Historically, Synt:em S.A. has generated revenues by providing services to third parties. The Act:map technology is primarily used in-house to optimize Pep:trans molecules but the Company has also signed service contracts with three American biotechnology companies and three European companies for discovery, optimization and other applications using Acti:map. Pep:trans has also been used in early stage research contracts with third parties.

        Capitalized research and development expenses were €3.7 million for the nine month period ending September 30, 2004 compared to €4.1 million in the prior year.

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        The decrease in capitalized research and development expenses was primarily due to a difference in timing and composition of capitalized research expenses. Under French GAAP, Synt:em S.A. capitalizes certain research and development expenses corresponding to distinct customized projects. Capitalized R&D costs include the direct costs of employees assigned to each project. Time spent by research staff is tracked using timesheets, then valued by taking into account each employee's fully charged salary rate multiplied by the number of hours actually devoted by the employee to each project. These costs may also include certain other expenses, which are directly imputable to each project such as active ingredients, chemical, synthetic, and consumable products, subcontracting costs (outside laboratories), and prototype costs. General overhead is not allocated to these projects.

        In line with the Company's internal project plans, manufacturing costs for the Syn1001 project were higher in 2003 than in 2004. The subcontracted preclinical work for Syn1002 was largely performed in 2004. The net of these two factors results in a higher capitalized research and development amount for the 2003 fiscal year compared to 2004. It is important to note that capitalized research and development under French GAAP does not include all R&D costs incurred. It only includes certain expenses relating directly to clearly defined projects (see Note 2 and Note 20 of the Synt:em S.A. Financial Statements included elsewhere in this document).

        Total expenses were €7.4 million for the nine month period ended September 30, 2004 compared to €7.3 million in the prior year. These expenses include the capitalized research and development amounts noted above along with other research and development costs that are not capitalized under French GAAP. Net of capitalized research and development, total expenses were €3.8 million for the nine months ended September 30, 2004 compared to €3.2 million in the prior period. This is due to significantly higher charges for amortization of capitalized research and development in 2004 due to the increase in capitalized research and development in 2003 compared to 2002, along with an increase in professional fees due to the Sonus transaction.

        Interest income, net of interest expense, was €0.1 million for the nine month period ended September 30, 2004 compared to €0.2 million for the prior period. The decrease in interest income was due to lower interest rates and lower levels of invested cash during 2004.

        Extraordinary income was €5,098 for the nine month period ended September 30, 2004 compared to €79,295 for the prior period. The company initiated a restructuring of operations in late 2002 which resulted in the termination of 7 employees (1 administrative assistant, 1 marketing manager, 1 IP portfolio manager and 4 scientists). Each terminated employee received standard termination benefits (as defined by our collective bargaining agreement) however, a portion of the costs (unworked notice period and standard ex-gratia payments) were paid in early 2003. A provision for restructuring of €85,124 was booked at year end 2002 to account for these payments due. This provision was then reversed in early 2003 as the payments were made and recorded in the 2003 accounts.

        Another extraordinary income difference between the period ended September 30, 2004 and the same period in 2003 relates to accruals for French Professional Tax rebate allowance. Synt:em S.A. generally qualifies for a partial rebate on the French Professional Tax ("Taxe Professionnelle") since the company is not profitable. This rebate is estimated at year end then reversed when the final tax declarations are filed and the rebate request is accepted in the following period.

        There were several immaterial extraordinary charges for the period ended September 30, 2004 amounting to €1,575 compared to €4,679 for the prior period. The variance is due to certain payments of employee fringe benefit taxes.

        As a non profitable entity, Synt:em S.A. had no corporate income tax liability in either the nine month period ended September 30, 2004 or ended September 30, 2003. However, there was a liability for the annual minimum tax ("impot forfaitaire annuelle") of approximately €3,000 which is due each year. Synt:em S.A. does qualify and does file for French research tax credits on an annual basis. The research tax credit figure for September 30, 2004 was €0.4 million compared to €0.5 million in the prior year. Under French GAAP, the research tax credit is booked to the income tax line of the balance

24

sheet. Under U.S. GAAP, it is booked as a reduction to research and development period expenses as it is considered a "subsidy" rather than a tax credit. The total income tax benefit (research tax credit and annual minimum tax) under French GAAP was €420,819 for the nine month period ended September 30, 2004 and €484,524 for the nine month period ended September 30, 2003.

Years Ended December 31, 2003 and December 31, 2002

        Revenues for the year ended December 31, 2003 were €0.4 million compared to €0.9 million in the prior year. Revenues in 2002 were derived from four short-term tactical contracts and one longer-term relationship with Sangstat. In 2003, the short-term contracts gradually drew to a close with Sangstat continuing.

        Synt:em S.A. first worked with Sangstat in 1996 and 1997. At that time, using Acti:map, Synt:em S.A. participated in the discovery and optimization of RDP58 (rationally designed peptide 58). This molecule has since progressed through phase II trials at Sangstat and is now being developed by Proctor & Gamble.

        Capitalized research and development expenses were €5.5 million for the year ended December 31, 2003 compared to €3.6 million in the prior year. The increase in capitalized research and development was due to the entry into clinical phase I trials for Syn1001.

        Total expenses were €11.0 million for the year ended December 31, 2003 which is greater than the prior year expense of €9.5 million. Net of capitalized research and development, total expenses were €5.6 million for the year ended December 31, 2003 compared to €5.9 million in the prior year. This reduction was primarily attributable to lower headcount and a rigorous focusing of research and development efforts on specific strategic projects following a restructuring that occurred in 2002.

        Interest income, net of interest expense, was €0.3 million for the year ended December 31, 2003 compared to €0.6 million for the prior year. The decrease in interest income was due to lower interest rates and lower levels of invested cash during 2003.

        Extraordinary income was €153,354 for the twelve month period ended December 31, 2003 compared to €45,661 for the prior period. The provision for restructuring of €85,124 was utilized in early 2003 (which is why it is noted in both the interim and annual period MD&A for 2003). Other differences include the amount of the professional tax refund allowance accrual which totaled €39,815 in 2003 and €33,481 in 2002. This rebate is based on fixed asset values, salary payments and other items which vary year by year.

        Extraordinary charges were €2,175 for the twelve month period ended December 31, 2003 compared to €87,370 for the prior period. The accrual for restructuring for €85,124 was entered in late 2002.

        Income taxes (other than the minor minimum tax due) were income of €0.6 million of research tax credits for the year ended December 31, 2003 compared to €0.9 million for the prior year. Research tax credits are calculated primarily on the increase in research and development expenditures in the year compared to the average of the prior two years. The mix of costs between amounts paid to French research organizations and amounts incurred as depreciation of capitalized research and development also has an effect on the credit amount obtained.

Years Ended December 31, 2002 and December 31, 2001

        Revenues for the year ended December 31, 2002 were €0.9 million compared to €1.1 million in the prior year. Revenues in these periods were derived from business development efforts to secure external collaborations and fee for service revenues. These opportunistic approaches provided some income but also competed with internal projects for available people and equipment resources which generated proportionately high sales and marketing costs. The Company has since decided to focus more of its resources on building an internal product pipeline.

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        Capitalized research and development expenses were €3.6 million for the year ended December 31, 2002 compared to €2.9 million in the prior year. This planned increase reflected the greater level of activity in the maturing internal product pipeline as Syn1001 advanced through regulatory preclinical trials.

        Total expenses were €9.5 million for the year ended December 31, 2002, which is greater than the prior year expense of €8.0 million. Net of capitalized research and development, total expenses were €5.9 million for the year ended December 31, 2002 compared to €5.0 million in the prior year. This increase was largely due to significantly higher charges for amortization of capitalized research and development in 2002. In 2001, the Company made a transition from a technology platform company to a product pipeline company. This significantly increased research and development costs which in turn led to an increase in capitalized research and development and amortization over the following three year period. A number of additional scientists were also employed during 2001. The annualized cost impact of this recruitment can be seen in the 2002 fiscal year. These new scientists, with expertise in preclinical, bioanalytical and clinical programs, were essential to the future development of the pipeline as the Company evolved from technology platform development to product development. Since the Company could not afford to incrementally increase overall headcount as it changed the profile mix of its research staff, certain other scientists were terminated in a restructuring that occurred in 2002.

        Interest income, net of interest expense, was €0.6 million for the year ended December 31, 2002 compared to €1.0 million for the prior year. The decrease in interest income was due to lower levels of invested cash during 2002.

        Extraordinary income for the year ended December 31, 2002 was €45,661 compared to €298,486 in the prior period. In 2001, Synt:em S.A. signed a technology transfer agreement whereby the company's know-how and expertise in peptide synthesis was provided to Epytop, a start-up company in Nimes. Epytop agreed to pay a fee of €243,918 for this technology transfer. Since Epytop had very little start up equity financing and the visibility on its ability to generate sufficient revenues through custom peptide synthesis for third parties was unclear, Synt:em S.A. recorded a contingency reserve for the entire amount of this technology transfer in 2001. The Epytop contract included a payment schedule which allocated the collection of the fee from September 2001 through December 2003. When payments are received, the reserve is reversed for an amount corresponding to the cash receipt (see note 11 of the notes to the financial statements of Synt:em S.A. for the year ended December 31, 2003). Epytop has been unable to make all payments according to this schedule.

        Extra ordinary charges for the year ended December 31, 2002 were €87,370. Extraordinary charges for the prior period were €35,147. The charge for 2002 includes the restructuring reserve.

        Income taxes (other than the minor minimum tax due) were €0.9 million of research tax credits for the year ended December 31, 2002 which is in line with the €0.9 million for the prior year.

Liquidity and Capital Resources

        Synt:em S.A. has historically financed operations with proceeds from equity financings and to a much lesser extent with subsidies, ANVAR conditional advances and revenue receipts under contractual agreements with third parties.

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        The various private equity financings and amounts raised are listed below (note that this table does not include amounts raised through the sale or exercise of warrants):

        At September 30, 2004 Synt:em S.A. had cash and cash equivalents of €6.4 million compared to €12.4 million at September 30, 2003. (Synt:em S.A. considers highly liquid investments with an original maturity of three months or less to be cash equivalents.)

        Management expects that cash requirements will increase in the future periods due to development costs associated with the pipeline of candidate molecules. Based on the current operating plan, Synt:em S.A. believes that existing cash and marketable securities along with loans that it intends to take against the research tax credit receivable on the balance sheet, will be sufficient to meet cash requirements through early 2005 based on current expense levels. Synt:em S.A. will need substantial additional funding to complete further preclinical and clinical trials of the candidate molecules in its portfolio.

        In France, a portion of annual expenses dedicated to research and development activities can generate a "research tax credit". This amount can be deducted from corporate income taxes due within a three year period. Should the company not have income taxes due, the amount is reimbursed by the French government at the end of the three year period following the filing of a research tax credit declaration. French GAAP classifies this credit (or "receivable") as a negative tax liability. For a company such as Synt:em S.A. that does not have income, it is equivalent to a subsidy as the credit is refunded directly to the company at the end of the three year period following the tax filing. The research tax credit received can also be used as a guarantee for a bank loan during the three year period prior to payment.

        Management can not give assurance that additional financing will be available on acceptable terms, if at all. Management can also not give assurance that the research tax credit receivable will be approved as a loan guarantee. If Synt:em S.A. is unable to raise additional financing, it will be financially at risk and required to curtail or delay the development of its products and new product research and development, which could seriously harm its business.

        Synt:em S.A. also has off balance sheet commitments in the form of scientific collaborations, software use, purchase order commitments, capital leases, operating leases and office rental arrangements.

        At September 30, 2004, Synt:em S.A. had approximately €1.2 million in ANVAR conditional advances, which are interest free. These are due to be repaid during the period from mid 2005 through 2008.

        Synt:em S.A. relies on external contract research organisations for certain regulatory preclinical and clinical studies which require commitments to reserve "research resource slots" in advance. As a result, there is often between €0.5 million and €1.3 million in off balance sheet purchase order commitments outstanding at any particular moment. This primarily reflects planned subcontracted research work and planned manufacturing of preclinical and clinical product batches.

        Synt:em S.A. has contractual contingent obligations to pay milestones and royalties to third parties should certain candidate molecules currently in research and development continue into later phases of development or some of the patents currently in international filing phases be confirmed.

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        Synt:em S.A.'s primary milestone and royalty obligations involve the Syn1002 compound that Synt:em S.A. licensed from a partner. Synt:em S.A. will make milestone payments to this partner should the compound progress successfully through development. For 2004, the milestone amount due was €50,000. All milestone costs are recognized when incurred, no accruals are made for these events in advance.

        As part of a joint inventive contribution, the company has committed to pay certain co-inventors a combined total of:

•

€167,000 for the year 2001 (payments already made and expensed)



•

€137,000 payable in the future contingent upon issuance of the corresponding patent in two different geographic areas



•

Royalties of 3 to 6% payable in the future on Synt:em S.A. service or product revenue realized as a result of these patents, and



•

Royalties of 1 to 2% on net sales of products directly commercialized by Synt:em S.A.

        Synt:em S.A. has remaining contractual obligations through 2005 under certain capital leases and contractual obligations through 2009 under operating lease agreements. The office rental agreement represents a remaining contractual obligation through 2009 (with a break option in June 2006). The following table summarizes the off balance sheet contractual obligations as of December 31, 2003:

Critical Accounting Policies and Estimates

        The preparation of the financial statements requires management to make estimates and assumptions that affect the reported amounts of liabilities at the date of the financial statements and the reported amounts of revenue and expenses during the reporting period. On an on-going basis, management evaluates its estimates and judgements including those related to revenue recognition and research and development costs. Management bases its estimates and judgements on historical experience and on various other factors that are believed to be reasonable under the circumstances. Actual results may differ from these estimates under different assumptions or conditions.

Research and Development Capitalization

        In the French GAAP accounts, certain research and development expenses are capitalized. Management determines the capitalization amount on a project by project basis. Only individual, clearly identified projects which Synt:em S.A.'s management believes could potentially reach commercial profitability have been capitalized. Should a project not perform as anticipated and the decision be made that the project has no potential, Company policy is stop research and development activities on that particular project and write off the associated capitalized research and development expenses. Note that all capitalized projects involve significant forward looking estimations. The accuracy of these predictions and the actual profitability of these projects can only be demonstrated in the future.

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Deferred Taxes

        Synt:em S.A. has accumulated certain tax loss carryforwards (see note 13). These losses result in deferred tax assets. However due to the loss making history of the Company, a full valuation allowance has offset any such tax effects.

Revenue Recognition

        Synt:em S.A.'s cumulative revenue is made up of fee for services, technology access fees, license option fees, technology licence fees, technology transfer fees and minimum annual royalty payments. All service-based revenues are recognized linearly over the period during which the services are provided. Technology access fees are recognized over the duration of the period upon which services using the technology were provided. License option fees are recognized over the duration of the option period. Technology license fees are recognized upon payment of fees during the license period. Technology transfer fees are recognized at the moment of know-how transfer. Minimum annual royalty payments are invoiced and recognized at the date they become due.

Restructuring Costs

        At times, Synt:em S.A. records restructuring provisions as a result of programs that are implemented within its operations. These provisions are recorded in order for Synt:em S.A. to summarize the impacts of the programs and separate these costs from recurring operations. When the decisions are made to undertake restructuring activities, management develops a formal plan and presents this to the Supervisory Board for approval. Once the plan is approved, management raises a valid expectation in those affected that it will carry out the restructuring by starting to implement that plan or announcing its main features to those affected by it. The costs included in a provision for restructuring are only those costs that are either incremental and incurred as a direct result of the plan, or are the result of a continuing contractual obligation with no continuing economic benefit to the Company, or a penalty incurred to cancel the contractual obligation. These costs are estimated based on numerous significant assumptions including, but not limited to, the following assumptions:

(1)

Estimated number of employees to be terminated in order to carry out management's plans; and

(2)

Approximate termination costs for specific contracts, leases, etc.;

        Under U.S. GAAP, a liability for a cost associated with an exit or disposal activity is recognized when the liability is incurred, and can be measured at fair value. These costs include, but are not limited to, one-time benefits provided to current employees who are involuntarily terminated and costs to terminate contracts that are not capital leases. If employees are required to render service until they are terminated in order to receive the termination benefits, the cost under U.S. GAAP is recognized rateably over the future service period.

Retirement Liability

        Under French GAAP, no retirement accrual has been made. Under U.S. GAAP, a liability has been recorded using the projected unit credit method. In accordance with U.S. GAAP, Synt:em S.A. determines its retirement liability based on actuarial assumptions. The actuarial experience that differs from our assumptions and changes in management's assumptions can result in gains and losses that are not yet recognized in Synt:em S.A.'s consolidated financial statements.

Recent Accounting Pronouncements

        In December 2004, the Financial Accounting Standards Board (FASB) issued its final standard on accounting for share-based payments, FASB Statement No. 123R (revised 2004), Share-Based Payment (FAS 123R), that requires companies to expense the value of employee stock options and similar awards. The Company is currently determining the effect, if any, this pronouncement will have on our balance sheet, income statement, and cash flows.

QUANTITATIVE AND QUALITATIVE DISCLOSURES ABOUT MARKET RISK

        The market risk inherent in the cash equivalent portfolio of Synt:em S.A. represents the potential loss arising from adverse changes in interest rates. If market rates hypothetically increase immediately and uniformly by 100 basis points from levels at September 30, 2004, the decline in the fair value of the cash equivalent portfolio would not be material. Synt:em does not expect its operating results or cash flows to be affected to any significant degree by a sudden change in market interest rates.

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SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

        This proxy statement includes certain "forward-looking" statements as defined within Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended, relating to the benefits of the proposed acquisition, integration plans, anticipated future financial and operating performance and results, including estimates for growth, time to market for new products, satisfaction of conditions to closing and expectations for our products and plans for development and expansion. These statements reflect management's current expectations based upon information currently available to them and are subject to various risks, uncertainties and assumptions. Any other statements contained herein (including without limitation statements to the effect that Sonus or management "estimates," "expects," "anticipates," "plans," "believes," "projects," "continues," "may," "could" or "would" or statements concerning "potential" or "opportunity" or variations thereof or comparable terminology or the negative thereof) that are not statements of historical fact are also forward-looking statements. There are a number of risks and uncertainties that could cause actual results to differ materially. For example, we may be unable to obtain stockholder approval required for the acquisition; problems may arise in successfully integrating our businesses; the acquisition may involve unexpected costs; and our businesses may suffer as a result of uncertainty surrounding the acquisition. For additional risk factors, please refer to the section of this proxy statement entitled "Risk Factors" beginning on page 31 of this proxy statement. Sonus also notes that its reported financial performance and period to period comparisons are not necessarily indicative of the results that may be expected in the future and Sonus believes that such comparisons cannot be relied upon as indicators of future performance. Sonus also notes that the market price of its common stock has exhibited high levels of volatility and therefore may not be suitable for all investors. More detailed information on these and additional factors which could affect the operating and financial results of Sonus are described in the Form 10-K of Sonus for the fiscal year ended December 31, 2003, which was filed with the SEC on March 12, 2004, the Form 10-Q of Sonus for the quarter ended September 30, 2004, which was filed with the SEC on November 15, 2004 and other risks detailed from time to time in reports of Sonus filed with the SEC. Sonus urges all interested parties to read these reports to gain a better understanding of the many business and other risks that Sonus faces. Additionally, Sonus undertakes no obligation to publicly release the results of any revisions to these forward-looking statements which may be made to reflect events or circumstances occurring after the date hereof or to reflect the occurrence of unanticipated events.

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RISK FACTORS

        In deciding how to vote your Sonus shares on the matters described in this proxy statement, you should carefully consider the risks set forth below in addition to other information contained in this proxy statement.

Risks Relating to the Acquisition

We may not be able to achieve the anticipated strategic benefits of our proposed combination with Synt:em S.A.

        Among the factors considered by our Board of Directors in connection its approval of the Amended and Restated Stock Purchase Agreement were the anticipated strategic benefits of the combination of Sonus and Synt:em S.A. We are not able to guarantee that the combination of Sonus and Synt:em S.A. will result in the realization of the full benefits anticipated by the companies.

We may not be able to successfully integrate our business with the business of Synt:em S.A.

        This transaction involves the integration of two companies based in different countries that previously have operated independently, which is a complex, costly and time consuming process. Following the combination of Sonus and Synt:em S.A., we may encounter difficulties in integrating our operations, technology and personnel with those of Synt:em S.A. and this may continue for some time. The combined company may not successfully integrate the operations of Sonus and Synt:em S.A. in a timely manner, if at all. The failure to successfully integrate two companies' operations could undermine the anticipated benefits and synergies of the combination, which could adversely affect our business, financial condition and results of operations. These anticipated benefits and synergies are based on projections and assumptions, not actual experience, and assume a successful integration.

The market price of our common stock may decline as a result of the acquisition.

        In connection with the acquisition, we will issue and could deliver as many as 5,425,000 shares of our common stock to Synt:em S.A. stockholders, subject to satisfaction of the conditions described in the Amended and Restated Stock Purchase Agreement. The acquisition of our shares by Synt:em S.A. stockholders who may not wish to hold shares in a U.S. company, as well as the increase in the outstanding number of shares of our common stock, may lead to sales of such shares or the perception that such sales may occur, either of which may adversely affect the market for, and the market price of, our common stock. In addition, the market price of our common stock may decline following the closing of the acquisition for a number of reasons, including if the integration of Synt:em S.A.'s business is unsuccessful or we do not achieve the anticipated financial and strategic benefits or our combination with Synt:em S.A. as rapidly or to the extent anticipated by stock market analysts or investors. The closing price of our common stock was $2.65 on November 2, 2004, the last day of trading prior to the announcement of the proposed acquisition. Since that date, our stock has fluctuated from a low of $2.18 to a high of $            . In addition, the closing price of our common stock was $3.10 on December 27, 2004, the last day of trading prior to the announcement of the revised terms of the proposed acquisition. On                        , 2005, the closing price of our common stock was $            .

Our stockholders will suffer immediate dilution to their equity and voting interests as a result of the issuance of our common stock to the Synt:em S.A. stockholders.

        In connection with the acquisition, we will issue and could deliver as many as 5,425,000 shares of our common stock should all milestones be met. This means that Synt:em S.A. stockholders may own approximately 20% of the total number of shares of our outstanding common stock following the completion of the acquisition. Accordingly, the issuance of our common stock to the Synt:em S.A.

31

stockholders will have the effect of reducing the percentage of equity and voting interest held by each of our current stockholders.

The Synt:em S.A. stockholders may be able to influence our company significantly following the acquisition.

        After the acquisition, and if milestones are achieved, former Synt:em S.A. stockholders could own approximately 20% of the total number of shares of our outstanding common stock, based on shares outstanding as of the Record Date. While no single former Synt:em S.A. stockholder or affiliated group of Synt:em S.A. stockholders will own more than 5% or more of the total outstanding shares of Sonus after completion of the acquisition, Synt:em S.A. stockholders as a group may be able to exercise substantial influence on the election of directors and other matters submitted for approval by our stockholders. The potential concentration of ownership of our common stock could make it difficult for our other stockholders to successfully approve or defeat matters submitted for stockholder action. Such concentrated ownership may also have the effect of delaying, deterring or preventing a change in control of Sonus without the consent of the former Synt:em S.A. stockholders.

Unanticipated costs relating to the acquisition and resulting combination of Sonus and Synt:em S.A. could reduce our future earnings.

        We believe that we have reasonably estimated the likely costs of the acquisition and integration of our operations with the operations of Synt:em S.A. and that such costs will range from $            to $            . It is possible that unexpected future operating expenses, such as increased personnel costs or unexpected severance costs, as well as other types of unanticipated developments, could adversely impact our business and reduce our cash and underlying capital.

The uncertainties associated with our acquisition of Synt:em S.A. may cause Synt:em S.A. or us to lose key personnel.

        Current and prospective Sonus and Synt:em S.A. employees may experience uncertainty about their future roles with the combined company until or after strategies with regard to the combined company are announced or executed. In the case of Synt:em S.A. employees, this is a particular concern since they will be subject to U.S.-based management following the acquisition. This uncertainty may adversely affect Sonus' and Synt:em S.A.'s ability to attract and retain key personnel. In addition, our ability to successfully integrate the two companies may be adversely affected if a significant number of key personnel depart before the completion of the acquisition or during the integration period following the acquisition.

Acquisition-related accounting charges may delay or reduce our profitability.

        We are accounting for the acquisition of Synt:em S.A. as a purchase following accounting principles generally accepted in the United States. Under the purchase method of accounting, the purchase price of Synt:em S.A. will be allocated to the fair value of the identifiable tangible and intangible assets and liabilities that we acquire from Synt:em S.A. The excess of the purchase price over Synt:em S.A.'s tangible assets will be allocated to goodwill and intangible assets. We are required to perform periodic impairment tests on goodwill and certain intangibles to evaluate whether the intangible assets and goodwill that we acquire from Synt:em S.A. continue to have fair values that meet or exceed the amounts recorded on our balance sheet. If the fair values of such assets decline below their carrying value on our balance sheet, we may be required to recognize an impairment charge related to such decline. We cannot predict whether or when there will be an impairment charge, or the amount of such charge, if any. However, if the charge is significant, it could cause the market price of our common stock to decline.

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Assumption of unknown liabilities as a result of the acquisition with limited recovery to the escrow may reduce our future earnings.

        It is possible that unknown liabilities of Synt:em S.A. will be assumed in the acquisition. Although Sonus may be entitled to recover damages for such liabilities from the escrow account established as part of the acquisition, recovery from the escrow may be insufficient to cover such liabilities, and any excess liabilities which become the obligation of Sonus could adversely impact our business and reduce our cash and underlying capital.

We will incur substantial costs whether or not the acquisition is completed.

        We will incur substantial costs related to the acquisition whether or not the acquisition is completed. These costs include fees for financial advisors, attorneys and accountants, filing fees and financial printing costs. We currently expect to incur approximately from $            to $            in total costs, excluding contingent fees payable to our financial advisors.

Risks Relating to the Combined Company After the Acquisition

If we fail to develop products, then we may never realize revenue from product commercialization.

        A key element of our business strategy is to utilize our technologies for the development and commercialization of products that utilize our drug delivery technology. Most of our attention and resources are directed to the development of TOCOSOL, a drug delivery technology that provides a novel approach to the formulation of water insoluble compounds for therapeutic applications. Significant expenditures in additional research and development, clinical testing, regulatory, manufacturing, and sales and marketing activities will be necessary in order for us to demonstrate the efficacy of our products, or commercialize any products developed with our technology. There can be no assurance that TOCOSOL Paclitaxel or any of our other current products under development or any future products will be safe or efficacious. If TOCOSOL or any of our other current products under development are ultimately ineffective in treating specific medical conditions, do not receive the necessary regulatory approvals or do not obtain commercial acceptance, we will be materially adversely affected.

        Similarly, Synt:em S.A. has focused much of its attention and resources on the development of its Pep:trans technology, or more specifically, the development of peptide-based technologies for transporting drugs across complex biological membranes and across the blood brain barrier. It is not possible to predict with any reasonable degree of certainty whether the conjugation of any particular drug to Synt:em S.A.'s Pep:trans peptide will result in a better, safer or more efficacious new drug. In addition there is no evidence that positive results observed in animals in vivo will correlate with results in humans, including safety or efficacy in transporting drugs across complex biological membranes such as the blood brain barrier. Pep:trans technology has been validated in animals, but there is no evidence that the technology will be effective or safe for use by humans, or that the technology can be successfully commercialized. Significant expenditures in additional research and development, clinical testing, regulatory, manufacturing and sales and marketing activities will be necessary in order for the combined company to demonstrate the efficacy of and to commercialize the Pep:trans technology, and there can be no assurance that prior positive results observed by Synt:em S.A. will result in safe or efficacious products for humans or that such products will obtain commercial acceptance.

        Even if we are successful in developing our products, there is no assurance that such products will receive regulatory approval or that a commercially viable market will develop. While it is our strategy to develop additional products under our drug delivery technology by entering into feasibility study agreements with companies who own active compounds, there can be no assurance that we will enter into any feasibility studies. Moreover, there can be no assurance that these feasibility studies will result in development or license agreements. Without feasibility studies or development or license agreements,

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we may need to scale back or terminate our efforts to develop other products using our drug delivery technology.

Peptide based pharmaceutical products show particular behavior which may adversely impact their commercialization.

        Most peptide based products suffer a short half-life in vivo and are usually restricted to a systemic (either sc or iv) route of administration. The consequence of a parenteral systemic administration restricts application of the technology to acute indications or severe or life threatening chronic diseases or indications where there is a strong medical need. There is no evidence that for our peptide based drugs we will be able to develop alternative routes of administration such as nasal, sub-lingual or intradermal which could broaden markets and improve our ability to commercialize such products. Failure to develop an acceptable formulation could adversely impact our business, operations and financial condition.

As a result of the acquisition, we will conduct more of our business internationally, which will expose us to additional and increased risks.

        We will significantly increase our international operations as a result of the acquisition, particularly in Europe. There are many risks that will impact our international business and multinational operations. These risks include the following:

•

compliance with multiple and potentially conflicting regulations in Europe and the United States, including export requirements, tariffs, import duties, and other trade barriers, health and safety requirements and requisite regulatory approvals;



•

potential labor strikes, lockouts, work slowdowns and work stoppages at U.S. and international ports;



•

differences in intellectual property protections in Europe and the U.S.;



•

difficulties in staffing and managing foreign operations in Europe;



•

restrictions on downsizing foreign operations in Europe and expenses and delays associated with such activities;



•

currency fluctuations and resulting losses on currency translations;



•

terrorists attacks on U.S. companies;



•

competition for foreign-based suppliers in Europe;



•

overlapping or differing tax structures;



•

cultural and language differences between the U.S. and Europe;



•

longer accounts receivable collection cycles in Europe; and



•

political or civil turmoil.

        A failure on our part to manage these risks effectively could adversely impact our business.

Upon completion of the acquisition, we will be a larger and broader organization and we may not be able to effectively integrate the business and operations of Synt:em S.A., which may cause our operating results to suffer.

        As a result of our acquisition of Synt:em S.A., we will face challenges inherent in efficiently managing an increased number of employees over a large geographic distance, including the need to implement appropriate systems, policies, benefits and compliance programs. Our inability to successfully

34

manage the geographically more diverse and larger combined organization, or any significant delay in achieving successful management, could have a material adverse effect on our results of operations after the acquisition and, as a result, on the market price of our common stock. The integration of Synt:em S.A. with our operations involves substantial risks, including:

•

our ability to finance the increased costs associated with development of the Synt:em S.A. operations and product development;



•

our ability to integrate the products of Synt:em S.A. so they complement our own;



•

our ability to continue the production and development of the Synt:em S.A. products and underlying technology;



•

our ability to manufacture and pursue the development of the Synt:em S.A. products;



•

our ability to integrate the international operations of Synt:em S.A.;



•

our ability to expand our financial and management controls and reporting systems and procedures including those related to the Sarbanes-Oxley Act of 2002, necessary for the integration and management of Synt:em S.A.;



•

diversion of management's time and attention; and



•

administrative integration.

        We may choose in the future not to pursue the development of certain product candidates of Synt:em S.A., which could require us to record losses relating to the termination of such programs. Any of the foregoing risks could materially harm our business, financial conditions and results of operations.

We have a history of operating losses which we expect will continue and we may never become profitable.

        We have experienced significant accumulated losses since our inception, and are expected to incur additional losses for the foreseeable future. These losses have resulted primarily from expenses associated with our research and development activities, including nonclinical and clinical trials, and general and administrative expenses. As of September 30, 2004, our accumulated deficit totaled $61.7 million. We anticipate that our operating losses will continue as we further invest in research and development for our products. Similarly, Synt:em S.A. has experienced significant accumulated losses since its inception, resulting primarily from expenses associated with research and development, preclinical, manufacturing and clinical activities relating to the development of its Pep:trans technology. As of September 30, 2004, Synt:em S.A.'s accumulated deficit was approximately $25.1 million. We will incur additional costs and expenses in connection with the acquisition and continuing operations of Synt:em S.A. We will not generate any product revenues unless and until we receive regulatory approval, which is not likely to occur in the near future. Even if we generate significant product revenues, there can be no assurance that we will be able to achieve or sustain profitability. Our results of operations have varied and will continue to vary significantly and depend on, among other factors:

•

timing and costs of preclinical development, clinical trials and regulatory approvals;



•

entering into new collaborative or product license agreements;



•

timing and costs of technology transfer associated with manufacturing and supply agreements;



•

our ability to obtain and timing of payments, if any, under collaborative partner agreements; and



•

costs related to obtaining, defending and enforcing patents.

        In addition, Synt:em S.A. relies on an annual research and development tax credit provided for under French law that is estimated to be approximately $700,000 in 2004. Changes to French tax law that would eliminate or substantially reduce this credit could have an adverse impact on the combined company's financial condition.

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Governmental regulatory requirements are lengthy and expensive and failure to obtain necessary approvals will prevent us or our partners from commercializing a product.

        We are subject to governmental regulatory requirements and a lengthy approval process for our products prior to any commercial sales of our products. The development and commercial use of our products are regulated by the U.S. Food and Drug Administration, or FDA, the European Medicines Evaluation Agency, or EMEA, and comparable regulatory agencies in other countries. The regulatory approval process for new products is lengthy and expensive. Before we can file an application with the FDA and comparable international agencies, a product candidate must undergo extensive testing, including animal studies and human clinical trials that can take many years and require substantial expenditures. Data obtained from such testing may be susceptible to varying interpretations, which could delay, limit or prevent regulatory approval. In addition, changes in regulatory policy for product approval may cause additional costs in our efforts to secure necessary approvals.

        Our drug delivery products are in the early to middle stages of development. The results of pre-clinical and clinical testing of our products are uncertain and regulatory approval of our products may take longer or be more expensive than anticipated, which could have a material adverse effect on our business, financial condition and results of operations. While the FDA has informally indicated that it is appropriate for Sonus to submit a TOCOSOL Paclitaxel New Drug Application under a 505(b)(2) regulatory mechanism, there can be no assurance that the FDA will agree to our proposed 505(b)(2) regulatory strategy. In addition, there is pending litigation attacking the utilization of the 505(b)(2) regulatory strategy generally. There can be no assurance that such litigation will not be successful. A 505(b)(2) application permits us to rely upon the FDA's findings of safety and efficacy for a previously approved drug product without requiring us to obtain a right of reference from the original applicant. In addition to permitting reliance upon the FDA's prior findings of safety and effectiveness for previously approved drugs, section 505(b)(2) continues to allow reliance on third-party data that is available in published literature and which establishes the safety and effectiveness of a drug. However, we are required to provide any additional clinical data necessary to demonstrate the safety and effectiveness of differences between the original drug and the 505(b)(2) drug, so while unnecessary duplication of preclinical and certain human studies is avoided, specific studies may be required to establish the relevance and applicability of prior findings for our particular product formulation. We cannot predict if or when any of our products under development will be commercialized.

Future U.S. or international legislative or administrative actions also could prevent or delay regulatory approval of our products.

        Even if regulatory approvals are obtained, they may include significant limitations on the indicated uses for which a product may be marketed. A marketed product also is subject to continual FDA, EMEA and other regulatory agency review and regulation. Later discovery of previously unknown problems or failure to comply with the applicable regulatory requirements may result in restrictions on the marketing of a product or withdrawal of the product from the market, as well as possible civil or criminal sanctions. In addition, if marketing approval is obtained, the FDA, EMEA or other regulatory agency may require post-marketing testing and surveillance programs to monitor the product's efficacy and side effects. Results of these post-marketing programs may prevent or limit the further marketing of a product.

We will need additional capital in the future, and if it is not available on terms acceptable to us, or at all, we may need to scale back our development and commercialization activities.

        Our development efforts to date have consumed and will continue to require substantial amounts of cash. Based on our current operating plan, including planned clinical trials, other product development costs, and operations of Synt:em S.A., we estimate that existing cash, cash equivalents and short-term investments will be sufficient to meet our cash requirements for at least the next nine

36

months. Our current operating plans include obtaining additional equity financing this fiscal year, which if successful, will provide us with a minimum of 12 months of cash. If we are unable to raise additional cash this fiscal year through either an equity financing or business partnerships, we have the ability to scale back operations such that we should have at least 12 months of cash. We will need additional capital to complete the development of TOCOSOL Paclitaxel and other product candidates as well as any product candidates based on Synt:em S.A.'s Pep:trans technology. Our future capital requirements depend on many factors including:

•

timing and costs of preclinical development, the scope and timing of clinical trials, and regulatory approvals;



•

entering into new collaborative or product license agreements;



•

timing and costs of technology transfer associated with manufacturing and supply agreements;



•

our ability to obtain and timing of payments, if any, under collaborative partner agreements; and



•

costs related to obtaining, defending and enforcing patents.

        Any future equity financing, if available, may result in substantial dilution to existing stockholders, and debt financing, if available, may include restrictive covenants. If we are unable to raise additional financing, we will have to substantially reduce our expenditures, scale back the development of our products and new product research and development, or license to others products that we otherwise would seek to commercialize ourselves, which could seriously harm our business, and explore other strategic alternatives.

We depend on third parties for funding, clinical development, manufacturing and distribution.

        We are dependent, and may in the future be dependent, on third parties for funding or performance of a variety of key activities including research, clinical development, manufacturing, marketing, sales and distribution of our products. Our current business strategy is to enter into agreements with third parties both to license rights to our potential products and to develop and commercialize new products. We currently do not have any arrangements with third parties in place, which will provide any funding to us. If we are unable to establish these arrangements with third parties, if they are terminated or the collaborations are not successful, we will be required to identify alternative partners to fund or perform research, clinical development, manufacturing, marketing, sales and/or distribution, which could have a material adverse effect on our business, financial condition and results of operations. Our success depends in part upon the performance by these collaborators of their responsibilities under these arrangements. We have no control over the resources that any potential partner may devote to the development and commercialization of products under these collaborations and our partners may fail to conduct their collaborative activities successfully or in a timely manner.

The development of pharmaceutical products in general, and the development of paclitaxel reformulations and peptide-based drugs in particular, is extremely competitive, and if we fail to compete effectively, it would negatively impact our business.

        Competition in the development of pharmaceutical products is intense and expected to increase. We also believe that other medical and pharmaceutical companies will compete with us in the areas of research and development, acquisition of products and technology licenses, and the manufacturing and marketing of our products. Success of products in these fields will be based primarily on:

•

obtaining, defending and enforcing patents.



•

safety;



•

price;

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•

ease of administration;



•

breadth of approved indications; and



•

physician, healthcare payor and patient acceptance.

        Several other companies are developing paclitaxel reformulations with a goal of delivering a more effective and tolerable therapy than the approved paclitaxel products. Some of these products are further along in development than TOCOSOL Paclitaxel and may achieve regulatory approval before our product. The FDA recently approved Abraxane™, a taxane product developed by American Pharmaceutical Partners, Inc., for the treatment of metastatic breast cancer. In addition, Aventis has a taxane product, Taxotere®, which is similar to paclitaxel and is marketed for the treatment of breast and non-small cell lung cancers.

        Similarly, several other companies are developing peptide-based drugs for the treatment of inflammatory and neuropathic pain, and competition in the development of brain delivery technologies is expected to increase. Some of these products are further along in development and may achieve regulatory approval before Synt:em S.A.'s products. There can be no assurance that the Synt:em S.A. products will be more effective or safer than existing drugs and even so there is no evidence that they will be able to successfully commercialize their products.

        Many of our competitors and potential competitors, including large pharmaceutical, chemical and biotechnology concerns and universities and other research institutions, have substantially greater financial, technical and human resources than we do and have substantially greater experience in developing products, obtaining regulatory approvals and marketing and manufacturing medical products. Accordingly, these competitors may succeed in obtaining FDA approval for their products more rapidly than us. In addition, other technologies or products may be developed that have an entirely different approach that would render our technology and products noncompetitive or obsolete. If we fail to compete effectively, it would have a material adverse effect on our business, financial condition and results of operations.

We rely on third-party suppliers and manufacturers to produce products that we develop and failure to retain such suppliers and manufacturers would adversely impact our ability to commercialize our products.

        We currently rely on third parties to supply the chemical ingredients necessary for our drug delivery products. We have entered into supply agreements for the supply of GMP, or good manufacturing practices, grade paclitaxel, which is the active pharmaceutical ingredient in TOCOSOL Paclitaxel. The chemical ingredients for our products are manufactured by a limited number of vendors. The inability of these vendors to supply medical-grade materials to us could delay the manufacturing of, or cause us to cease the manufacturing of our products. We also rely on third parties to manufacture our products for research and development and clinical trials. SICOR Pharmaceuticals, Inc. is our primary manufacturer of TOCOSOL Paclitaxel for clinical studies and has also agreed to manufacture TOCOSOL Paclitaxel for commercialization. We previously manufactured clinical supplies of TOCOSOL Paclitaxel at other GMP certified contract laboratories. Suppliers and manufacturers of our products must operate under GMP regulations, as required by the FDA, and there are a limited number of contract manufacturers that operate under GMP regulations. Our reliance on independent manufacturers involves a number of other risks, including the absence of adequate capacity, the unavailability of, or interruptions in, access to necessary manufacturing processes and reduced control over delivery schedules. If our manufacturers are unable or unwilling to continue manufacturing our products in required volumes or have problems with commercial scale-up, we will have to identify acceptable alternative manufacturers. The use of a new manufacturer may cause significant interruptions in supply if the new manufacturer has difficulty manufacturing products to our

38

specifications. Further, the introduction of a new manufacturer may increase the variation in the quality of our products.

        Similarly, Synt:em S.A. relies on third parties to supply all of Synt:em S.A.'s pre-clinical and clinical supplies, including the supply of M6G, the active pharmaceutical ingredient necessary for the development and manufacture of several Synt:em S.A. products. The M6G manufacturing process is covered by patents either held by or licensed to certain third-party companies. Synt:em S.A. has supply agreements with [several] suppliers and Synt:em S.A. believes that each of Synt:em S.A.'s suppliers manufactures in accordance with Synt:em S.A.'s specifications and GMP guidelines. However there are few sources of supply for the M6G necessary for Synt:em S.A.'s products and the inability of Synt:em S.A. to obtain sufficient quantities of M6G from one of these suppliers could have a material adverse effect on our business.

        In addition, Synt:em S.A. has evaluated and selected appropriate contract manufacturing organizations (CMOs) for key manufacturing activities. Agreements have been established with each CMO in order to secure Synt:em S.A.'s materials requirements; however, Synt:em S.A. has no direct control over the resources devoted to its projects and reliance on such third parties involves a number of risks, including the possibility that such third parties may fail their development work, may fail to perform on an effective or timely basis or may terminate the contracts. Synt:em S.A. believes that its existing agreements are sufficient to satisfy its current needs for preclinical and clinical requirements for peptide based compounds. However, to Synt:em S.A.'s knowledge, therapeutic products based on peptides coupled to organic compounds have never been manufactured on a commercial scale. There can be no assurance that Synt:em S.A.'s partners will be able to manufacture sufficient quantities of M6G in a timely manner and at an acceptable price and quality.

If we fail to secure adequate intellectual property protection or become involved in an intellectual property dispute, it could significantly harm our financial results and ability to compete.

        Our success will depend, in part, on our ability to obtain and defend patents and protect trade secrets. As of September 30, 2004, six United States patents have been issued pertaining to our TOCOSOL drug delivery platform and other technologies. A patent covering our TOCOSOL drug delivery platform has also been issued in Taiwan. Additional patent applications are pending in the United States and counterpart filings have been made in Europe and key countries in Asia and Latin America. Similarly, Synt:em S.A. has patents issued in Europe and Australia. Synt:em S.A. also has patent applications pending in Europe, Australia, the United States, Canada and Japan. The patent position of medical and pharmaceutical companies is highly uncertain and involves complex legal and factual questions. There can be no assurance that any claims which are included in pending or future patent applications will be issued, that any issued patents will provide us with competitive advantages or will not be challenged by third parties, or that the existing or future patents of third parties will not have an adverse effect on our ability to commercialize our products. Furthermore, there can be no assurance that other companies will not independently develop similar products, duplicate any of our products or design around patents that may be issued to us. Litigation may be necessary to enforce any patents issued to us or to determine the scope and validity of others' proprietary rights in court or administrative proceedings. Any litigation or administrative proceeding could result in substantial costs to us and distraction of our management. An adverse ruling in any litigation or administrative proceeding could have a material adverse effect on our business, financial condition and results of operations.

Our commercial success will depend in part on not infringing patents issued to competitors.

        There can be no assurance that patents belonging to competitors will not require us to alter our products or processes, pay licensing fees or cease development of our current or future products. Any litigation regarding infringement could result in substantial costs to us and distraction of our

39

management, and any adverse ruling in any litigation could have a material adverse effect on our business, financial condition and results of operations. Further, there can be no assurance that we will be able to license other technology that we may require at a reasonable cost or at all. Failure by us to obtain a license to any technology that we may require to commercialize our products would have a material adverse effect on our business, financial condition and results of operations. In addition, to determine the priority of inventions and the ultimate ownership of patents, we may participate in interference, reissue or re-examination proceedings conducted by the U.S. Patent and Trademark Office or in proceedings before international agencies with respect to any of our existing patents or patent applications or any future patents or applications, any of which could result in loss of ownership of existing, issued patents, substantial costs to us and distraction of our management.

Reimbursement procedures and future healthcare reform measures are uncertain and may adversely impact our ability to successfully sell pharmaceutical products.

        Our ability to successfully sell any pharmaceutical products will depend in part on the extent to which government health administration authorities, private health insurers and other organizations will reimburse patients for the costs of future pharmaceutical products and related treatments. In the United States, government and other third-party payers have sought to contain healthcare costs by limiting both coverage and the level of reimbursement for new pharmaceutical products approved for marketing by the FDA. In some cases, these payers may refuse to provide any coverage for uses of approved products to treat medical conditions even though the FDA has granted marketing approval. Healthcare reform may increase these cost containment efforts. We believe that managed care organizations may seek to restrict the use of new products, delay authorization to use new products or limit coverage and the level of reimbursement for new products. Internationally, where national healthcare systems are prevalent, little if any funding may be available for new products, and cost containment and cost reduction efforts can be more pronounced than in the United States.

If our products are not accepted by the medical community our business will suffer.

        Commercial sales of our proposed products will substantially depend upon the products' efficacy and on their acceptance by the medical community. Widespread acceptance of our products will require educating the medical community as to the benefits and reliability of the products. Our proposed products may not be accepted, and, even if accepted, we are unable to estimate the length of time it would take to gain such acceptance.

If we lose our key personnel or are unable to attract and retain qualified scientific and management personnel, we may be unable to become profitable.

        We are highly dependent on our key executives. The loss of any of these key executives or the inability to recruit and retain qualified scientific personnel to perform research and development and qualified management personnel could have a material adverse effect on our business, financial condition and results of operations. There can be no assurance that we will be able to attract and retain such personnel on acceptable terms, if at all, given the competition for experienced scientists and other personnel among numerous medical and pharmaceutical companies, universities and research institutions.

The businesses in which we engage have a risk of product liability, and in the event of a successful suit against us, our business could be severely harmed.

        The testing, marketing and sale of pharmaceutical products entails a risk of product liability claims by consumers and others. While we currently maintain product liability insurance, which we believe to be adequate for current applications of our products, such insurance may not continue to be available at a reasonable cost or may not be sufficient to fully cover any potential claims. In the event of a

40

successful suit against us, the lack or insufficiency of insurance coverage could have a material adverse effect on our business and financial condition.

Since we use hazardous materials in our business, we may be subject to claims relating to improper handling, storage or disposal of these materials.

        Our research and development activities involve the controlled use of hazardous materials, chemicals and various radioactive compounds. We are subject to foreign, federal, state and local laws and regulations governing the use, manufacture, storage, handling and disposal of such materials and certain waste products. Although we believe that our safety procedures for handling and disposing of such materials comply with the standards prescribed by state and federal regulations, the risk of accidental contamination or injury from these materials cannot be eliminated completely. In the event of such an accident, we could be held liable for any damages that result and any such liability not covered by insurance could exceed our resources. Compliance with environmental laws and regulations may be expensive, and current or future environmental regulations may impair our research, development or production efforts.

Failure to satisfy Nasdaq National Market Listing requirements may result in our common stock being delisted from The Nasdaq National Market.

        Our common stock is currently listed on the Nasdaq National Market under the symbol "SNUS." For continued inclusion on the Nasdaq National Market, we must maintain among other requirements stockholders' equity of at least $10.0 million, a minimum bid price of $1.00 per share and a market value of our public float of at least $5.0 million; or market capitalization of at least $50 million, a minimum bid price of $3.00 per share and a market value of our public float of at least $15.0 million. As of September 30, 2004, we had stockholders' equity of approximately $24.4 million. In the event that we fail to satisfy the listing standards on a continuous basis, our common stock may be removed from listing on the Nasdaq National Market. If our common stock were delisted from the Nasdaq National Market, our common stock may be transferred to the Nasdaq SmallCap Market if we satisfy the listing criteria for the Nasdaq SmallCap Market or trading of our common stock, if any, may be conducted in the over-the-counter market in the so-called "pink sheets" or, if available, the National Association of Securities Dealer's "Electronic Bulletin Board." In addition, delisting from Nasdaq may subject our common stock to so-called "penny stock" rules. These rules impose additional sales practice and market making requirements on broker-dealers who sell and/or make a market in such securities. Consequently, broker-dealers may be less willing or able to sell and/or make a market in our common stock. Additionally, an investor would find it more difficult to dispose of, or to obtain accurate quotations for the price of, our common stock. As a result of a delisting, it may become more difficult for us to raise funds through the sale of our securities.

Market volatility may affect our stock price and the value of an investment in our common stock may be subject to sudden decreases.

        The trading price for our common stock has been, and we expect it to continue to be, volatile. The price at which our common stock trades depends upon a number of factors, including our historical and anticipated operating results, preclinical and clinical trial results, market perception of the prospects for biotechnology companies as an industry sector and general market and economic conditions, some of which are beyond our control. Factors such as fluctuations in our financial and operating results, changes in government regulations affecting product approvals, reimbursement or other aspects of our or our competitors' businesses, FDA review of our product development activities, the results of preclinical studies and clinical trials, announcements of technological innovations or new commercial products by us or our competitors, developments concerning key personnel and our intellectual property rights, significant collaborations or strategic alliances and publicity regarding actual or

41

potential performance of products under development by us or our competitors could also cause the market price of our common stock to fluctuate substantially. In addition, the stock market has from time to time experienced extreme price and volume fluctuations. These broad market fluctuations may lower the market price of our common stock. Moreover, during periods of stock market price volatility, share prices of many biotechnology companies have often fluctuated in a manner not necessarily related to the companies' operating performance. Also, biotechnology stocks may be volatile even during periods of relative market stability. Accordingly, our common stock may be subject to greater price volatility than the stock market as a whole.

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PROPOSAL ONE

APPROVAL OF THE ISSUANCE OF COMMON STOCK IN CONNECTION WITH THE
ACQUISITION OF SYNT:EM S.A., S.A.

General

        Sonus seeks your approval pursuant to Nasdaq Marketplace Rule 4350(i)(1)(D) which requires Nasdaq-listed companies to obtain shareholder approval before issuing 20% or more of their common stock or 20% or more of their voting power, in connection with an acquisition of the stock or assets of another company, other than in a public offering for cash. For purposes of the Nasdaq Marketplace Rules the percentage of outstanding shares is calculated before giving effect to the issuance of the shares in question.

        Sonus entered into an Amended and Restated Stock Purchase Agreement on December 27, 2004, with the stockholders of Synt:em S.A., and certain option and warrant holders of Synt:em S.A. The Amended and Restated Stock Purchase Agreement supercedes in its entirety a Stock Purchase Agreement entered into by the same parties on November 3, 2004. The Amended and Restated Stock Purchase Agreement provides for the purchase by Sonus of all the issued and outstanding shares of capital stock of Synt:em S.A. directly from the stockholders of Synt:em S.A. According to the Amended and Restated Stock Purchase Agreement, Sonus agreed that it will issue 5,425,000 shares of Sonus common stock to the stockholders of Synt:em S.A. if all of the contingent consideration is earned. You are being asked to approve the issuance by Sonus of shares of common stock as the consideration in the acquisition of Synt:em S.A. If the issuance of the common stock is not approved by you, the acquisition cannot occur. The actual terms of the acquisition of Synt:em S.A. are contained in the Amended and Restated Stock Purchase Agreement, which Sonus has filed with the SEC as an exhibit to Form 8-K on December 28, 2004. You can review this Form 8-K and the Amended and Restated Stock Purchase Agreement on the SEC's website, www.sec.gov. The Amended and Restated Stock Purchase Agreement is also attached to this proxy statement as Appendix A.

THE ACQUISITION

        This section of the proxy statement describes the material aspects of the proposed acquisition of Synt:em S.A., including the Amended and Restated Stock Purchase Agreement. While we believe that the description covers the material terms of the acquisition and the Amended and Restated Stock Purchase Agreement, this summary may not contain all of the information that is important to you. You should read carefully this entire document and the other documents to which we refer, including the Amended and Restated Stock Purchase Agreement that is attached as Appendix A for a more complete understanding of the acquisition and the Amended and Restated Stock Purchase Agreement.

Background of the Acquisition

        The Board of Directors and senior management of Sonus regularly assess the competitive position of our products, technologies, workforce, manufacturing and distribution capabilities, and markets. Sonus has a strategic goal of expanding its approach to the development of drugs for the oncology and complementary markets, and as a result, Sonus continuously explores strategic opportunities to strengthen our business.

        In January 2004, at an investor conference in San Francisco, George Dunbar, a member of the Board of Directors of Sonus, was introduced to Michel Kaczorek, Chief Executive Officer of Synt:em S.A., Gordon Waldron, Vice President and Chief Financial Officer and Laurent Ganem, President of the Supervisory Board, by a former advisor to a Synt:em S.A. shareholder. The former advisor recommended an informal discussion between the companies to discuss the strategic benefits of a possible transaction between the two companies.

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        On February 2, 2004, Sonus and Synt:em S.A. executed a mutual confidentiality agreement and on February 16, 2004, the parties held an initial teleconference to discuss a possible business combination of Synt:em S.A. with Sonus. Representatives of Synt:em S.A. on the call included Michel Kaczorek, Gordon Waldron, Jamal Temsamani, Synt:em S.A.'s Vice President of Preclinical Research and Development and Luc-Andre' Granier, Synt:em S.A.'s Vice President of Clinical Development and Medical Director. Representatives of Sonus on the call included Lynn Collins-Gold, Vice President of Research and Process Development for Sonus, Neile Grayson, Sonus' Vice President of Business Development, and Dean Kessler, Sonus' Vice President for Pre-clinical Development. The Synt:em S.A. representatives provided the Sonus team with a brief history of the Synt:em S.A. business and discussed current financials. The parties also discussed at length Synt:em S.A.'s Pep:trans and Acti:map technology platforms, as well as current preclinical and clinical candidates.

        On March 11, 2004, the parties conducted an in-person meeting in Basel, Switzerland. Representatives of Sonus included Neile Grayson, and Mark Low, Vice President of Business and Market Development for Sonus and Dr. Kaczorek represented Synt:em S.A. Several hours were spent discussing the TOCOSOL technology of Sonus and the most advanced product of Sonus, TOCOSOL Paclitaxel. A confidential presentation on TOCOSOL Paclitaxel was provided to Dr. Kaczorek.

        On April 4, 2004, Michael Martino, President and Chief Executive Officer of Sonus, and Pam Dull, the Director of Investor Relations for Sonus, attended a meeting in Boston with representatives of Adams, Harkness & Hill, financial advisor to Synt:em S.A., to discuss whether Sonus had an interest in pursuing a potential business combination between Sonus and Synt:em S.A.

        On April 8, 2004, the parties conducted a teleconference attended by Mr. Martino and Dr. Grayson of Sonus, a representative of Adams, Harkness & Hill and Dr. Kaczorek and Mr. Waldron of Synt:em S.A. The parties discussed certain procedural aspects for moving forward with discussions regarding a potential combination of the companies, as well as certain process and timing issues for due diligence efforts. The parties agreed to conduct an in-person meeting in London in May, 2004, as it was determined that representatives from each company would be present in London during that time for other business reasons.

        From April 9 through May 5, 2004, representatives of the parties conducted a series of due diligence discussions via teleconference and email focusing on technical issues concerning the parties' respective products and technologies and intellectual property.

        At a regularly scheduled meeting of the Board of Directors of Sonus held on May 5, 2004, Mr. Martino presented Synt:em S.A. as a candidate for a possible strategic combination. The Board of Directors authorized management to continue to pursue discussions with Synt:em S.A. regarding a possible acquisition of Synt:em S.A. by Sonus.

        On May 12, 2004, Mr. Martino and Dr. Grayson met with Dr. Kaczorek and Mr. Waldron in London to continue discussions concerning a possible transaction between the two companies. The parties also discussed Synt:em S.A.'s progress with Syn1001 and Syn1002 development. Adams, Harkness & Hill then presented proposed company comparables for Synt:em S.A. in a first discussion of valuation.

        On May 18, 2004, a teleconference was attended by Mr. Martino and Dr. Grayson of Sonus and representatives of Adams, Harkness & Hill. Adams, Harkness & Hill representatives advised that Synt:em S.A. was progressing in its discussions with other companies concerning a potential strategic combination with Synt:em S.A. and the need for Sonus to engage representation of a financial advisor to assist in negotiations. Dr. Grayson requested additional Synt:em S.A. financial and sales information.

        From May 21 through June 2, 2004, additional technical, business and financial due diligence information was provided by each of the parties to the other party.

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        On June 8 and 9, 2004, Dr. Temsamani, Dr. Kaczorek, and Mr. Waldron of Synt:em S.A. toured the Sonus headquarters in Bothell, Washington and met with Mr. Martino, Dr. Grayson, Dr. Collins-Gold, Elaine Waller, Dean Kessler and Mark Low of Sonus. The purpose of the meeting was to review the Sonus product development pipeline. A number of break-out due diligence meetings were also conducted.

        On July 8, 2004, the parties conducted a teleconference attended by Mr. Martino, Mr. Eudy, and Dr. Grayson of Sonus, Dr. Kaczorek and Mr. Waldron of Synt:em S.A., and representatives of Adams, Harkness & Hill. Also participating in the call were representatives of Needham & Company, the recently engaged financial advisor to Sonus. The parties agreed that Sonus would prepare a draft of an initial term sheet setting forth proposed material terms of an acquisition of Synt:em S.A. by Sonus. The parties also had preliminary valuation and structure discussions.

        On July 15 and 16, 2004, Dr. Collins-Gold and Mr. Kessler of Sonus, together with a representative of Needham & Company, made an initial technical due diligence visit to Synt:em S.A.'s facilities in Nimes, France. Meetings were conducted with Dr. Granier, Dr. Temsamani, and Dr. Lahana and Caroline Roussel, Vice President and Director of Operations of Synt:em S.A., with discussions focused on the Synt:em S.A. clinical, preclinical and discovery product candidate pipeline, and the Pep:trans and Acti:map technologies. Manufacturing practices and current out-sourced processes were also reviewed, and the discussion concerning a combination of the companies' technology platforms also occurred.

        On August 11, 2004, the Board of Directors of Sonus ratified the engagement of Needham & Company.

        On August 17, 2004, a meeting among the parties was held at the offices of Adams, Harkness & Hill in Boston. Attendees at the meeting were representatives of Needham & Company, Dr. Kaczorek and Mr. Waldron of Synt:em S.A. and Mr. Martino and Dr. Grayson of Sonus. Discussions ensued concerning progress of the Synt:em S.A. pipeline. Further detail of the Synt:em S.A. pro forma financials was also reviewed and the parties discussed the expectation of a letter of interest from Sonus to be delivered within two weeks of the meeting.

        On August 24, 2004, Sonus delivered a non-binding letter of intent to Synt:em S.A. and Adams, Harkness & Hill for the purchase of 100% of the outstanding capital stock of Synt:em S.A. Proposed terms included an initial payment of $8 million of Sonus common stock followed by two subsequent milestone payments of up to $2.8 million each, payable in either Sonus common stock or cash, upon treatment of a first patient in Phase 1 clinical trials for Syn1001 or Syn1002. An additional $8.4 million payment in Sonus common stock or cash, at Sonus' discretion, would be payable upon signing of a partnership agreement for further clinical trials with a qualified commercial entity for either Syn1001 or Syn1002, with mutually agreeable minimum parameters. Share re-sale restrictions on the initial payment and the milestone payments were proposed.

        On August 27, 2004, Dr. Kaczorek sent an e-mail to Mr. Martino indicating that the letter of intent provided by Sonus was not acceptable to the Synt:em S.A. shareholders. In particular, Dr. Kaczorek indicated that the Synt:em S.A. shareholders did not agree with the overall valuation and the concept of earn-out milestones.

        During the next several days, several conversations occurred between representatives of Needham & Company and Adams, Harkness & Hill concerning the deal structure and valuation.

        On August 31, 2004, during a telephone conversation between Mr. Waldron and Dr. Grayson, Mr. Waldron emphasized that total valuation was important to the Synt:em S.A. shareholders and that ownership of one-third of the combined entity would be appropriate. Mr. Waldron again stressed that the concept of earn-out milestones was not acceptable to the Synt:em S.A. shareholders and he

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indicated that Sonus would receive a letter of response from Synt:em S.A. management within 24 hours.

        On September 1, 2004, a written response was received by Mr. Martino from Dr. Kaczorek which indicated that valuation and milestone earn-out payments were the biggest concern for Synt:em S.A.'s shareholders.

        On September 9 and 10, 2004, Mr. Martino and Dr. Grayson attended a meeting of the Supervisory Board of Synt:em S.A. in Paris to deliver a presentation on the technology of Sonus and the product potential of TOCOSOL Paclitaxel. Following the Supervisory Board meeting, Mr. Martino and Dr. Grayson met with Dr. Kaczorek and Mr. Waldron to discuss a draft term sheet prepared by Stradling Yocca Carlson & Rauth, Sonus' outside counsel. Several issues were raised by the Synt:em S.A. representatives, including the concept of representations and warranties to be made by Synt:em S.A. shareholders and the amount of Synt:em S.A. net cash required at the closing of a transaction. Neither concern was satisfactorily resolved at this meeting.

        On September 14 and 16, 2004, discussions were held by representatives of Sonus and Synt:em S.A. regarding financial and accounting matters.

        On September 20, 2004, Sonus delivered a proposed term sheet to Synt:em S.A. The proposal included a total consideration of $30 million of Sonus common stock for the purchase of 100% of the outstanding capital stock of Synt:em S.A., subject to upper and lower collars of 29% and 26% of the outstanding shares of Sonus, payable in an upfront payment consisting of $8 million plus Synt:em S.A. net cash at closing, followed by two equal earn-out milestone payments for the remainder of the consideration, on the initiation of the first human dosing in a Phase 1 clinical trial under a U.S. Investigational New Drug Application of any currently identified Synt:em S.A. product candidate. In addition, share resale restrictions were proposed for all shares of Sonus common stock delivered in the transaction.

        On September 21, 2004, Sonus provided Synt:em S.A. with a revised term sheet containing additional language suggested by Adams, Harkness & Hill clarifying that the earn-out milestones do not need to be based solely upon a U.S. Investigational New Drug Application, but could also be earned upon approval by an appropriate ministry of health as Sonus in its discretion determines is appropriate. The non-binding term sheet was executed by Sonus and Synt:em S.A. on September 22, 2004.

        From September 28 through October 8, 2004, the parties continued due diligence activities including on-site visits by representatives of each party and review of all material contracts, and other written information of the other party. In addition, representatives of the parties engaged in several discussions concerning the integration of the two companies.

        On October 7, 2004, a draft Stock Purchase Agreement was delivered by Stradling Yocca Carlson & Rauth to Brown Rudnick Berlack Israels, LLP, U.S. counsel for Synt:em S.A. The parties' legal representatives had numerous discussions concerning the provisions of the Stock Purchase Agreement, and on October 15, 2004, a revised version of the Stock Purchase Agreement was delivered by Stradling Yocca Carlson & Rauth and shared with the major Synt:em S.A. shareholders for review and comment.

        On October 20, 2004, a memo was sent from Stradling Yocca Carlson & Rauth to Brown Rudnick Berlack Israels, LLP, outlining certain open issues to be resolved between the parties in order to finalize the Stock Purchase Agreement, including, among other things, issues regarding the indemnification escrow, earn-out payments, Synt:em S.A. outstanding options and warrants, payment of Synt:em S.A.'s transaction expenses, timing of the issuance of the earn-out shares, the date of calculation of cash at closing, termination date of the Stock Purchase Agreement and governing law.

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        On October 21, 2004, a letter was sent from Dr. Ganem, the President of Synt:em S.A.'s Supervisory Board and a representative of a major Synt:em S.A. shareholder, to Mr. Martino regarding major unresolved issues from the point of view of Synt:em S.A. These included: representations and warranties to be made by Synt:em S.A. shareholders, termination date of the Stock Purchase Agreement, and Synt:em S.A. management compensation post-transaction. Dr. Ganem's letter led to a telephone conversation later the same day between Dr. Ganem and Mr. Martino regarding these issues as well as the earn-out payments and terms and conditions for arbitration and mediation. The amount and time limit of the indemnification escrow was also a point of discussion.

        On October 22, 2004, a second letter was sent by Dr. Ganem to Mr. Martino regarding additional unresolved issues from the point of view of Synt:em S.A., including structure of the earn-out payments, termination date of the Stock Purchase Agreement, management benefits, and the indemnification escrow. Later that same day, a special meeting of the Board of Directors of Sonus was held to discuss the proposed transaction. The Board spent considerable time discussing results of Sonus' due diligence investigation of Synt:em S.A., including intellectual property protection of the Synt:em S.A. product candidates which would trigger the earn-out payments, as well as to other criteria relating to the product candidates such as technical merit, potential market, and economic viability. Representatives of Needham & Company provided the Board of Directors of Sonus with an analysis of the financial implications of the terms of the proposed acquisition. Representatives of Needham & Company also delivered to the Sonus Board of Directors Needham & Company's oral opinion, subsequently confirmed in writing on October 22, 2004, that the consideration to be paid by Sonus under the terms of the draft Stock Purchase Agreement dated October 19, 2004, was fair, from a financial point of view, to the stockholders of Sonus. Following discussion, the Board of Directors of Sonus voted to conditionally approve the transaction, pending satisfactory resolution of certain open issues identified by Dr. Ganem to Mr. Martino.

        On October 24, 2004, a revised version of the Stock Purchase Agreement was delivered by Stradling Yocca Carlson & Rauth to Synt:em S.A. management and counsel for review and comment.

        On October 25, 2004, a teleconference was attended by Mr. Martino, Dr. Ganem and outside legal counsel for each party to discuss the registration process for shares to be issued to Synt:em S.A. shareholders in the acquisition. The content and extent of Synt:em S.A. shareholder representations and warranties was also reviewed.

        On October 26, 2004, a telephone conversation was held between Dr. Ganem and Mr. Martino regarding the upcoming Synt:em S.A. shareholders meeting. Later that day, a revised version of the Stock Purchase Agreement was delivered by Stradling Yocca Carlson & Rauth.

        On October 27, 2004, a special telephonic meeting of the Board of Directors of Sonus was held to discuss the resolution of outstanding issues, including the indemnification escrow, earn-out provisions, treatment of Synt:em S.A. options and warrants, and termination date of the Stock Purchase Agreement. After discussion, the Board unanimously voted to approve the transaction as negotiated by management.

        On October 29, 2004, a special meeting of the Supervisory Board of Synt:em S.A. was held, during which the Synt:em S.A. Supervisory Board discussed the transaction.

        On October 29, 2004, a final version of the Stock Purchase Agreement was delivered to the parties by Stradling Yocca Carlson & Rauth. Later that day, at a special meeting of the Synt:em S.A. stockholders, the Stock Purchase Agreement was unanimously endorsed by all Synt:em S.A. stockholders and their legal representatives. On November 3, 2004, the Stock Purchase Agreement was executed by Sonus, all of the stockholders of Synt:em S.A. and certain option holders and warrant holders of Synt:em S.A. and Sonus issued a press release in connection with its quarterly earnings conference call announcing the transaction.

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        From November 4, 2004 through November 10, 2004, representatives of Sonus, including Michael Martino, Alan Fuhrman, Senior Vice President and Chief Financial Officer of Sonus, and Pamela Dull had meetings with a number of institutional stockholders of Sonus. At these meetings, a substantial majority of the stockholders indicated that they were not in favor of the terms of the proposed acquisition and would not vote in favor of it at a stockholders meeting to be convened to consider the matter. Factors noted by such stockholders were the overall valuation of Synt:em S.A., in light of the upper and lower collars on the shares of Sonus common stock to be delivered, the timing of the transaction in relation to the current market price of Sonus common stock and the milestone metrics that triggered the earn-out payments. Following these meetings, Sonus management concluded that it was unlikely that stockholders holding a majority of the votes cast at a meeting of the stockholders of Sonus would approve the proposed acquisition.

        On November 23, 2004, Mr. Martino informed Dr. Ganem of Sonus' need to revise the terms of the acquisition in order to address concerns expressed by the stockholders of Sonus. The main areas of discussion included the timing of certain earn-out payments and the nature of the events triggering such payments, the total percentage ownership that Synt:em S.A. stockholders would have in Sonus at the closing of the acquisition, and the need for Sonus stockholders to retain any increases in the value of Sonus' stock resulting from achievement of certain near-term Sonus milestones.

        On November 30 and December 1, 2004, Mr. Martino, Mr. Fuhrman, and Dr. Grayson from Sonus, Dr. Kaczorek and Mr. Waldron from Synt:em S.A., Dr. Ganem and outside counsel and financial advisors for the parties, met in Paris to discuss the proposed revisions to the terms of the Stock Purchase Agreement.

        From December 4 through December 7, 2004, Mr. Martino and Dr. Ganem engaged in numerous telephonic discussions regarding the proposed revisions to the terms of the acquisition including the structure of lock-up provisions and payment of transaction fees.

        On December 8, 2004, at a regularly scheduled meeting, the Board of Directors of Sonus discussed and considered the proposed revisions to the Stock Purchase Agreement and unanimously authorized management to pursue the negotiation of an Amended and Restated Stock Purchase Agreement.

        On December 13, 2004, the Board of Directors of Sonus held a telephonic meeting where the proposed revised terms were further discussed and management was unanimously authorized to finalize negotiations.

        On December 14, 2004, Stradling Yocca Carlson & Rauth circulated to all parties a proposed Summary of Terms of Amendment to Stock Purchase Agreement for discussion and comment. The proposed Summary of Terms provided among other things, that the maximum aggregate consideration to be received by the Synt:em S.A. stockholders would be 20% of the fully diluted (based on the treasury stock method) outstanding common stock of Sonus and the elimination of any lower or upper collars of the shares of common stock to be delivered by Sonus.

        On December 14, 2004, the Synt:em S.A. Board of Directors discussed the most recent proposal from Sonus.

        On December 17, 2004, the Board of Directors of Sonus held a telephonic conference meeting to consider the final terms of the proposed amendment to the Stock Purchase Agreement. The Board discussed the changes to the existing Stock Purchase Agreement proposed by the amended terms, including the revised consideration, the elimination of upper and lower collars, the change of earn-out milestones from Phase 1 to Phase 2 clinical trials for qualified Synt:em S.A. products, the reallocation of closing consideration to contingent earn-out consideration of any appreciation of the shares of Sonus common stock resulting from the announcement of FDA agreement to Phase 3 clinical trials of TOCOSOL Paclitaxel or a corporate partnership, and changes to the lock-up periods for the shares to be delivered to the Synt:em S.A. shareholders. Representatives of Stradling Yocca Carlson & Rauth

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and Needham & Company reviewed the proposed terms in comparison to the original Stock Purchase Agreement. Following discussions with legal and financial advisors, the Board concluded that the revised terms of the transaction, both in terms of value and structure, were superior from the standpoint of Sonus as compared to the terms of the Stock Purchase Agreement dated as of November 2, 2004. In light of the foregoing, and in the absence of any material changes to the factors considered and relied upon by Needham & Company in rendering a fairness opinion on October 22, 2004 with respect to the November 3, 2004 Stock Purchase Agreement, the Board concluded that there would not be any significant benefit in obtaining an updated fairness opinion from Needham & Company with respect to the Amended and Restated Stock Purchase Agreement. Following that discussion, the Sonus Board unanimously approved the terms of the Amended and Restated Stock Purchase Agreement.

        On December 20, 2004, Dr. Kaczorek and Mr. Waldron presented to Synt:em S.A. stockholders the Amended and Restated Stock Purchase Agreement.

        On December 22, 2004, the Synt:em S.A. Supervisory Board held a meeting to discuss the transaction. Later the same day, there was a meeting of the stockholders of Synt:em S.A. in Paris, France to discuss the final Amended and Restated Stock Purchase Agreement.

        By December 27, 2004, the Amended and Restated Stock Purchase Agreement was executed by Sonus, by all of the stockholders of Synt:em S.A. and certain option holders and warrant holders of Synt:em S.A. and on December 28, 2004, Sonus issued a press release announcing the amended terms of the acquisition and the execution of the Amended and Restated Stock Purchase Agreement.

Sonus' Reasons for the Acquisition

        In reaching its determination to approve the acquisition of Synt:em S.A., and to recommend that the Sonus stockholders vote to approve the issuance of shares of Sonus common stock pursuant to the terms of the Amended and Restated Stock Purchase Agreement, the Board of Directors of Sonus identified several potential benefits of the proposed acquisition for Sonus and its stockholders. These potential benefits include the following:

•

the belief that the expanded product portfolio of the combined company will provide an improved platform for future growth;



•

the strengthening of Sonus' pipeline and capabilities in oncology and extension to other related, large markets;



•

the ability to leverage Synt:em S.A.'s highly efficient discovery program that utilizes a proprietary computer screening process (Acti:map) that effectively reduces time and many risk factors generally associated with drug discovery;



•

the addition of the Synt:em S.A. technology platform which will add novel approaches to changing the bioavailability of drugs, as well as the potential ability to enable selective drug uptake into certain cells and organs;



•

the expectation that the complementary nature of the technologies and products of Sonus and Synt:em S.A. would enhance the combined company's ability to increase its pipeline of drug development candidates; and



•

the ability of Sonus to leverage the knowledge and skills of the experienced scientific personnel of Synt:em S.A., adding a substantial number of Ph.D.'s to the Sonus staff.

        In reaching its decision to approve the Amended and Restated Stock Purchase Agreement and the share issuance, the Board of Directors of Sonus consulted with management of Sonus, legal counsel of Sonus regarding the legal terms of the acquisition, and financial advisors of Sonus regarding the

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financial aspects of the acquisition and the fairness, from a financial point of view, of the consideration to be paid by Sonus, to the stockholders of Synt:em S.A. The factors that the Board of Directors of Sonus considered in its deliberations included the following:

•

the strategic and other expected benefits of the acquisition described above;



•

information and presentations by Sonus management and legal and financial advisors concerning the business, technology, products, operations, financial condition, organizational structure and competitive position of Sonus and Synt:em S.A., on both an historical and prospective basis;



•

Sonus management's view of the business and prospects of Sonus and Synt:em S.A. as stand-alone companies and as a combined company;



•

Sonus management's view of the financial condition, results of operations and businesses of Sonus and Synt:em S.A. before and after giving effect to the acquisition;



•

other strategic alternatives for Sonus, including the potential to enter into strategic relationships with third parties or acquire or combine with third parties;



•

the belief that the terms of the acquisition agreement are reasonable; and



•

the presentation by Needham & Company and its oral opinion presented on October 22, 2004, subsequently confirmed by delivery of its written opinion dated as of October 22, 2004, to the effect that, as of such date, and based upon and subject to the factors and assumptions set forth therein, the consideration to be paid by Sonus under the original Stock Purchase Agreement dated November 3, 2004 was fair from a financial point of view to the stockholders of Sonus.

        The Board of Directors of Sonus also identified and considered a variety of potentially negative factors in its deliberations concerning the Amended and Restated Stock Purchase Agreement, including the following:

•

the risk that the potential benefits sought in the acquisition may not be fully realized;



•

the risk that integration of the businesses, products and personnel of the two companies may not be successfully implemented in a timely and efficient manner, or at all;



•

the possibility that the acquisition might not be approved by the stockholders of Sonus, or otherwise not be consummated;



•

the risk that as a result of the announcement of the acquisition, existing relationships with suppliers and investors of Sonus could be impaired;



•

the possibility that the market price of Sonus common stock could decrease sharply if the acquisition was not viewed favorably by stockholders, financial analysts and the press, generally;



•

the significant costs incurred by Sonus or the combined company as a result of the acquisition, including costs of integrating the businesses and transaction expenses arising from the acquisition;



•

the diversion of management's time and attention from the existing business of Sonus;



•

the perception of Sonus as a viable, independent company may be damaged;



•

the risks associated with owning a French company, including being subject to French regulations and laws that differ from those applicable in the United States, and the difficulty of managing the business of Synt:em S.A. due to geographic locations;

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•

the risk of the potential loss of key employees; and



•

various other risks associated with the acquisition and the businesses of Sonus, Synt:em S.A. and the combined company described in this proxy statement under "Risk Factors" and in the corresponding section in documents incorporated by reference into this proxy statement.

        After due consideration, the Board of Directors of Sonus concluded, however, that overall, the potential benefits to Sonus and its stockholders of the acquisition outweighed the risks associated with the acquisition.

        The above discussion of the factors considered by the Board of Directors of Sonus is not intended to be exhaustive, but is believed to set forth the principal factors considered by the Board of Directors of Sonus. The Board of Directors of Sonus collectively reached the conclusion, by unanimous vote, to approve the Amended and Restated Stock Purchase Agreement in light of the various factors described above and other factors that each member of the Board of Directors of Sonus felt were appropriate. In view of the wide variety of factors considered by the Board of Directors of Sonus in connection with its evaluation of the acquisition and the complexity of these matters, the Board of Directors of Sonus did not consider it practical, and did not attempt, to quantify, rank or otherwise assign relative weights to the specific factors it considered in reaching its decision. Rather, the Board of Directors of Sonus made its recommendation based on the totality of information presented to and the investigation conducted by it. In considering the factors discussed above, individual directors may have given different weights to different factors.

        After careful consideration of all of the information and factors discussed in this section, the Board of Directors of Sonus, by unanimous vote, approved the acquisition, the Amended and Restated Stock Purchase Agreement and the other transactions contemplated by the Amended and Restated Stock Purchase Agreement. The Board of Directors of Sonus unanimously recommends that Sonus stockholders vote "FOR" the proposal to issue shares of Sonus common stock to the Synt:em S.A. stockholders pursuant to the terms of the Amended and Restated Stock Purchase Agreement.

Opinion of Financial Advisor to Sonus

        Sonus and Needham & Company, Inc. entered into an engagement letter dated as of July 7, 2004, pursuant to which Sonus retained Needham & Company to (i) act as its financial advisor in connection with the acquisition of all of the outstanding securities of Synt:em S.A. (the "Transaction"), and (ii) render an opinion to the Board of Directors of Sonus as to the fairness, from a financial point of view, to the stockholders of Sonus of the total consideration payable by Sonus pursuant to the terms of the draft Stock Purchase Agreement dated October 14, 2004 (the "October Purchase Agreement"). Needham & Company was selected by the Board of Directors of Sonus to render an opinion to the Board of Directors of Sonus because Needham & Company is an internationally recognized investment banking firm and because, as part of its investment banking business, Needham & Company is continually engaged in the valuation of businesses and their securities in connection with mergers and acquisitions, negotiated underwritings, secondary distributions of listed and unlisted securities, private placements and valuations for corporate and other purposes.

        On October 22, 2004, Needham & Company delivered its oral opinion (which was followed up by its written opinion dated as of October 22, 2004) to the Board of Directors of Sonus, to the effect that, as of that date and based upon and subject to the assumptions and other matters described in the opinion, the total consideration of up to $30 million to be paid by Sonus in connection with the Transaction in accordance with the terms of the October Purchase Agreement was fair to the Sonus shareholders from a financial point of view. In connection with rendering its opinion, Needham & Company assumed that the Transaction, including each of the two earn-out events described in the October Purchase Agreement would be consummated upon the terms and conditions set forth in the October Purchase Agreement. The Needham & Company opinion is addressed to the Board of

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Directors of Sonus, is directed only to the financial terms of the October Purchase Agreement and does not constitute a recommendation to any Sonus stockholder as to how that stockholder should vote on, or take any other action relating to, the combination. The amount and form of consideration to be paid in the combination was determined through arm's length negotiations between Sonus and Synt:em S.A. and not by Needham & Company. Needham & Company expressed no opinion as to what the value of Sonus common stock will be when issued to the securityholders of Synt:em S.A. pursuant to the October Purchase Agreement or the prices at which the Sonus common stock will actually trade at any time. In addition, Needham & Company was not asked to consider, and the Needham & Company opinion does not address the underlying business decision of Sonus to engage in the combination, the relative merits of the combination as compared to other business strategies that might exist for Sonus, or the effect of any other transaction in which Sonus might engage. Needham & Company expressed no opinion or recommendation as to whether or not stockholders of Synt:em S.A. should vote in favor of the Transaction.

        The complete text of the Needham & Company opinion, which sets forth the assumptions made, matters considered, limitations on and scope of the review undertaken by Needham & Company, is attached to this proxy statement as Appendix C and is incorporated herein by reference. The summary of the Needham & Company opinion set forth in this proxy statement is qualified in its entirety by reference to the Needham & Company opinion. Sonus stockholders are urged to read the Needham & Company opinion carefully and in its entirety for a description of the procedures followed, the factors considered, and the assumptions made by Needham & Company.

        In arriving at its opinion, Needham & Company, considered and reviewed such financial and other matters as it deemed relevant, including, among other things:

        (1)   publicly available business and financial information relating to Sonus and Synt:em S.A. that Needham & Company deemed to be relevant;

        (2)   financial forecasts and other information relating to the business, earnings, cash flow, cash and other resource requirements, assets, liabilities and financing and other prospects of Sonus and Synt:em S.A. furnished to Needham & Company by Sonus and Synt:em S.A.;

        (3)   discussions with members of senior management and representatives of Sonus concerning the current and future business prospects of Sonus and the joint prospects for the combined company, including synergies that may be achieved by the combined company;

        (4)   the trading characteristics and historical and current market prices of Sonus and certain publicly traded companies that Needham & Company deemed to be relevant;

        (5)   the proposed financial terms of the Transaction and the financial terms of other transactions that Needham & Company deemed to be relevant;

        (6)   discussions and negotiations among representatives of Sonus and Synt:em S.A. and their respective financial and legal advisors;

        (7)   a draft of the October Purchase Agreement dated October 19, 2004; and

        (8)   other financial studies and analyses and other matters as Needham & Company deemed necessary, including Needham & Company's assessment of general economic, market and monetary conditions.

        In conducting its review and arriving at its opinion, Needham & Company, with the consent of Sonus, assumed and relied, without independent investigation, upon the accuracy and completeness of all financial and other information provided to it by Sonus and Synt:em S.A., respectively, or which was publicly available. Needham & Company did not undertake any responsibility for the accuracy, completeness or reasonableness of, or independently verify, this information. Needham & Company

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further relied upon the assurance of the managements of Sonus and Synt:em S.A. that they were unaware of any facts that would make the information provided to Needham & Company incomplete or misleading in any material respect. Needham & Company, with the consent of Sonus, assumed that the forecasts and the description of the expected synergies which Needham & Company examined were reasonably prepared by the managements of Sonus and Synt:em S.A. on bases reflecting the best currently available estimates and good faith judgments of such managements as to the future performance of Sonus and Synt:em S.A. and that such projections, and the combined company forecasts used in Needham & Company's analyses, provide a reasonable basis for its opinion.

        Needham & Company did not make or obtain any independent evaluations, valuations or appraisals of the assets or liabilities of Sonus or Synt:em S.A., nor was Needham & Company furnished with these materials. With respect to all legal matters relating to Sonus, Needham & Company relied on the advice of legal counsel to Sonus; however, counsel for Sonus was not asked to, nor did it, provide any legal advice to Needham & Company. Needham & Company's services to Sonus in connection with the combination consisted of rendering an opinion from a financial point of view of the total consideration to be paid by Sonus in connection with the Transaction as described in the October Purchase Agreement. Needham & Company's opinion was necessarily based upon economic and market conditions and other circumstances as they existed and could be evaluated by Needham & Company on the date of its opinion. It should be understood that although subsequent developments may affect its opinion, Needham & Company does not have any obligation to update, revise or reaffirm its opinion and Needham & Company expressly disclaims any responsibility to do so. Needham & Company was not asked by the Board of Directors of Sonus to update, revise or reaffirm its opinion dated October 22, 2004 as a result of or in connection with the execution of the Amended and Restated Stock Purchase Agreement, and Needham & Company's opinion and its analyses related thereto are not based on the Amended and Restated Stock Purchase Agreement or the transactions contemplated thereby.

        In rendering its opinion on October 22, 2004, Needham & Company assumed, in all respects material to its analysis, that the representations and warranties of each party contained in the October Purchase Agreement were true and correct, that each party would perform all of the covenants and agreements required to be performed by it under the October Purchase Agreement and that all conditions to the consummation of the combination would be satisfied without any material waiver, amendment or modification thereof. Needham & Company assumed that the final form of the Stock Purchase Agreement would be substantially similar to the October Purchase Agreement. Needham & Company also assumed that all governmental, regulatory and other consents and approvals contemplated by the October Purchase Agreement would be obtained and that, in the course of obtaining any of those consents, no restrictions would be imposed or waivers made that would have an adverse effect on the contemplated benefits of the combination.

        The following is a summary of the principal financial analyses performed by Needham & Company to arrive at its opinion. Some of the summaries of financial analyses include information presented in tabular format. In order to fully understand the financial analyses, the tables must be read together with the text of each summary. The tables alone do not constitute a complete description of the financial analyses. Considering the data set forth in the tables without considering the full narrative description of the financial analyses, including the methodologies and assumptions underlying the analyses, could create a misleading or incomplete view of the financial analyses. Needham & Company performed certain procedures, including each of the financial analyses described below, and reviewed with the management of Sonus the assumptions on which such analyses were based and other factors, including the historical and projected financial results of Sonus and Synt:em S.A. No limitations were imposed by the Sonus Board of Directors with respect to the investigations made or procedures followed by Needham & Company in rendering its opinion.

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        The implied equity values set forth in the following sections compare to the Transaction's total consideration of up to $30 million to be paid by Sonus pursuant to the terms of the October Purchase Agreement, which included an initial payment at closing of approximately $10.4 million, which is the sum of $8 million and Synt:em S.A.'s net cash at closing, estimated to be approximately $2.4 million. The balance of the consideration was based on the achievement of the two earn-out events described in the October Purchase Agreement. For purposes of its analysis and in arriving at its opinion, Needham & Company assumed that the Transaction, including each of the earn-out events, would be consummated upon the terms and subject to the conditions set forth in the October Purchase Agreement. Based on the foregoing, the implied equity value for the Transaction described in the October Purchase Agreement was $30 million and the implied enterprise value was $27.6 million.

Selected Comparable Public Companies Analysis.

        Using publicly available information, Needham & Company compared selected financial and other data of Synt:em S.A. to corresponding data for selected publicly traded companies with operations that for purposes of this analysis may be considered reasonably comparable to the operations of Synt:em S.A., based on the stage of development of their pharmaceutical compounds. Needham & Company compared Synt:em S.A. with the companies listed below.

•

Alnylam Pharmaceuticals, Inc.



•

Arena Pharmaceuticals, Inc.



•

ArQule, Inc.



•

Array Biopharma, Inc.



•

Avigen, Inc.



•

Compugen, Ltd.



•

Curis, Inc.



•

Ecopia Biosciences, Inc.



•

Memory Pharmaceuticals Corp.



•

Momenta Pharmaceuticals, Inc.



•

Pro-Pharmaceuticals, Inc.



•

StemCells, Inc.



•

Tapestry Pharmaceuticals, Inc.

        For each of these comparable companies, Needham & Company calculated equity value and the enterprise value, based on closing stock prices on October 18, 2004. The following table sets forth information concerning the valuations resulting from Needham & Company's analysis.

        Although the analysis of the selected comparable public companies was used for comparison purposes, none of the companies is directly comparable to Synt:em S.A.

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Selected Merger Transactions Analysis.

        Using publicly available information, Needham & Company reviewed and analyzed certain financial and operating data relating to selected biotechnology acquisition transactions in which the target was at a similar development stage to Synt:em S.A. These transactions were (listed as acquirer / target):

Genta, Inc. / Salus Therapeutics, Inc.
GenVec, Inc. / Diacrin, Inc.
Incyte Genomics, Inc. / Maxia Pharmaceuticals, Inc.
Protein Design Labs, Inc. / Eos Biotechnology, Inc.
Sangamo BioSciences, Inc. / Gendaq Ltd.

        The following table sets forth information concerning the equity value and enterprise value at closing with and without additional consideration paid upon the assumed achievement of disclosed milestones.

        Although the analysis in the selected transactions were used for comparison purposes, none of those transactions is directly comparable to the Transaction, and none of the companies in those transactions is directly comparable to Sonus or Synt:em S.A. Accordingly, an analysis of the results of such a comparison is not purely mathematical, but instead involves complex considerations and judgments concerning differences in historical financial and operating characteristics of the companies involved and other factors that could affect the acquisition value of such companies or Synt:em S.A. to which they are being compared. Needham & Company noted that, as of October 22, 2004, based on the implied enterprise value of Synt:em S.A. in the Transaction and the then current fully-diluted market value of Sonus, and assuming that all earn-out events were achieved, Synt:em S.A. securityholders would own approximately 28.2% of the combined company.

        The summary set forth above does not purport to be a complete description of the analyses performed by Needham & Company in connection with the rendering of its opinion. The preparation of a fairness opinion involves various determinations as to the most appropriate and relevant quantitative and qualitative methods of financial analyses and the application of those methods to the particular circumstances, and, therefore, such an opinion is not readily susceptible to partial analysis or summary description. Needham & Company did not attribute any particular weight to any analysis or factor considered by it, but rather made qualitative judgments as to the significance and relevance of each analysis and factor. Accordingly, Needham & Company believes, and has advised the Board of Directors of Sonus, that its analyses must be considered as a whole and that selecting portions of its analyses or the factors it considered, without considering all analyses and factors, could create a misleading or incomplete view of the process underlying its opinion. In its analyses, Needham & Company made numerous assumptions with respect to industry performance, general business and economic conditions and other matters, many of which are beyond the control of Sonus and Synt:em S.A. These analyses performed by Needham & Company are not necessarily indicative of actual values or predictive of future results or values, which may be significantly more or less favorable. Additionally, analyses relating to the values of businesses or assets do not purport to be appraisals or necessarily reflect the prices at which businesses or assets may actually be sold. Accordingly, these analyses and

55

estimates are inherently subject to substantial uncertainty, being based upon numerous factors or events beyond the control of Sonus or Synt:em S.A. or their respective advisors. None of Sonus, Synt:em S.A., Needham & Company or any other person assumes responsibility if future results are materially different from those projected. Needham & Company's opinion and its related analyses were only one of many factors considered by the Board of Directors of Sonus in its evaluation of the Transaction as described in the October Purchase Agreement and should not be viewed as determinative of the views of the Board of Directors with respect to the fairness of the total consideration to Synt:em S.A. securityholders.

        In the ordinary course of its business, Needham & Company and its affiliates trade the equity securities of Sonus for their own accounts and for the accounts of their customers, and, accordingly, may at any time hold a long or short position in such securities. Needham & Company and its affiliates in the ordinary course of business have from time to time provided, and in the future may continue to provide, commercial and investment banking services to Sonus, including serving as a financial advisor on potential acquisitions and as an underwriter on equity offerings, and have received and may in the future receive fees for the rendering of such services.

        If the combination as described in the Amended and Restated Stock Purchase Agreement is completed during the period Needham & Company is retained by Sonus, or within twelve months thereafter, Sonus will pay Needham & Company a total of $650,000 for its services as the financial advisor of Sonus. If the combination is not completed during that period, Sonus will pay Needham $300,000 for rendering its opinion as to fairness of the consideration payable by Sonus in connection with the Transaction, from a financial point of view, to the stockholders of Sonus. Sonus also will reimburse Needham for its reasonable out-of-pocket expenses. Additionally, Sonus agrees to indemnify Needham & Company against certain liabilities, including liabilities under the federal securities laws. The terms of the fee arrangement with Needham & Company, which are customary in transactions of this nature, were negotiated at arm's length between Sonus and Needham & Company, and the Board of Directors of Sonus was aware of the arrangement, including the fact that a significant portion of the fee payable to Needham & Company is contingent upon the completion of the Transaction.

Governmental and Regulatory Matters

        Sonus and Synt:em S.A. will comply with applicable federal and state securities laws in connection with the issuance of the Sonus common stock pursuant to the acquisition, and with applicable provisions of Delaware law. Except for applicable filings with the U.S. Securities and Exchange Commission and the approval of our stockholders as described in this proxy statement, no federal, state or French regulatory filings, consents or approvals will be required to consummate the acquisition.

Federal Income Tax Considerations

        There are no material U.S. federal income tax consequences to our current stockholders that will result from our issuance of additional shares of our common stock in the acquisition.

Anticipated Accounting Treatment

        The acquisition will be accounted for as a "purchase" transaction for accounting and financial reporting purposes, in accordance with accounting principles generally accepted in the United States. After the transaction, the results of operations of Synt:em S.A. will be included in the consolidated financial statements of Sonus. The purchase price will be allocated based on the fair values of the assets acquired and the liabilities assumed. Pursuant to Statements of Financial Accounting Standards No. 141, "Business Combinations" and No. 142, "Goodwill and Other Intangible Assets," goodwill will be subject to at least annual assessments for impairment based on a fair value test. Identified intangible assets with finite lives are amortized over those lives. A final determination of the intangible asset

56

values and required purchase accounting adjustments, including the allocation of the purchase price to the assets acquired and liabilities assumed based on their respective fair values, has not yet been made. Sonus will determine the fair value of assets and liabilities and will make appropriate business combination accounting adjustments. However, for purposes of disclosing unaudited pro forma information in this proxy statement, Sonus has made a preliminary determination of the purchase price and purchase price allocation, based upon current estimates and assumptions, which is subject to revision upon consummation of the transaction.

Listing of Sonus Common Stock to Be Issued in the Acquisition

        The shares of common stock issued to Synt:em S.A. stockholders in the acquisition will be listed on the Nasdaq National Market. Pursuant to the Stockholders Agreement, Sonus will agree to register for resale the shares of the Sonus common stock issuable under the Amended and Restated Stock Purchase Agreement on a registration statement on Form S-3 to be filed with the SEC within five business days following the closing date.

Restriction on Resale of Sonus Common Stock

        The shares of Sonus common stock issued under the Amended and Restated Stock Purchase Agreement have not been registered under the Securities Act of 1933, as amended (the "Act"), and the Synt:em S.A. stockholders may not sell or transfer such shares except pursuant to an exemption from registration under the Act. Pursuant to the Stockholders Agreement, Sonus will agree to register for resale the shares of the Sonus common stock issuable under the Amended and Restated Stock Purchase Agreement on a registration statement on Form S-3 to be filed with the SEC within five business days following the closing date. In addition, certain stockholders of Synt:em S.A. who are "affiliates" of Synt:em S.A. may be subject to additional resale restrictions pursuant to Rule 145 of the Act.

        The Stockholders Agreement also includes a lock-up provision, pursuant to which each stockholder of Synt:em S.A. will agree not to sell or otherwise transfer shares of Sonus common stock received under the Amended and Restated Stock Purchase Agreement. The restrictions on transfer will lapse on December 31, 2005.

        If Sonus does not register the shares of Sonus common stock issued under the Amended and Restated Stock Purchase Agreement for resale or the registration statement is not declared effective by the SEC within nine months following the closing date, the restrictions on transfer imposed by the lock-up shall terminate on the date that is nine months following the closing date.

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THE AMENDED AND RESTATED STOCK PURCHASE AGREEMENT

        The following summary describes aspects of the proposed stock purchase, including material provisions of the Amended and Restated Stock Purchase Agreement. This summary may not contain all of the information that is important to you. To understand the stock purchase fully, and for a more complete description of the legal terms of the stock purchase, you are urged to read the Amended and Restated Stock Purchase Agreement carefully. A copy of the Amended and Restated Stock Purchase Agreement is attached as Appendix A.

Structure of the Acquisition

        The Amended and Restated Stock Purchase Agreement provides for the purchase by Sonus of all of the shares of capital stock of Synt:em S.A. owned by each of the stockholders of Synt:em S.A. The Amended and Restated Stock Purchase Agreement was entered into on December 27, 2004 by Sonus as the buyer, stockholders of Synt:em S.A. as the sellers, Michel Kaczorek and Caroline Roussel, each of whom is an officer and stockholder of Synt:em S.A., as managers, certain option holders and warrant holders of Synt:em S.A. and                    , as the sellers' agent. The Amended and Restated Stock Purchase Agreement supercedes in its entirety a Stock Purchase Agreement entered into by the same parties on November 3, 2004. Upon consummation of the stock purchase, Synt:em S.A. will become a wholly owned subsidiary of Sonus. The stock purchase will be effected promptly following approval of the issuance of shares of Sonus common stock under the Amended and Restated Stock Purchase Agreement by the stockholders of Sonus. It is anticipated that the stockholders meeting will be held and the stock purchase will be consummated in                        , 2005.

Stock Purchase Consideration

        According to the Amended and Restated Stock Purchase Agreement, Sonus agreed that it will issue 5,425,000 shares of Sonus common stock to the stockholders of Synt:em S.A. and deliver the shares into escrow at the closing, to be released at various times and upon certain conditions as described below. The full amount of the shares will only be delivered upon the achievement of specified milestones. Sonus shares issuable in connection with the transaction are payable in three installments, the first of which is payable at the closing (subject to the reallocation mechanism described below), the second of which is payable after receipt of audited financial statements for fiscal year 2005 and the third of which is payable upon the achievement of specified milestones. The maximum number of shares will only be delivered if the earn-out milestones are achieved. Euro denominated values will be converted into U.S. Dollars at the applicable exchange rate on the day immediately prior to the date of closing.

        Closing Consideration.    At closing, Sonus will issue shares of Sonus common stock having a value of $8.75 million, plus 864,454 Euros, plus the amount of cash and cash equivalents less debt for borrowed money as of December 31, 2004 of Synt:em S.A., and less the amount of any transaction expenses of Synt:em S.A. paid or payable, reimbursed or reimbursable by Sonus after December 31, 2004. It is estimated that the shares issuable at the closing will have an aggregate market value of approximately $12 million. The number of shares of Sonus common stock payable at the closing will be based upon the average closing price of Sonus common stock for the 20 consecutive trading days ending two days before the closing date.

        Shares of Sonus common stock payable at the closing will be deposited into an escrow account and will be subject to reduction in the event of an increase in the market price of Sonus common stock after the announcement of one or both of two specified value events relating to TOCOSOL Paclitaxel. If such an event occurs, the number of shares reduced from the shares of Sonus common stock payable at closing will be added to the shares of Sonus common stock comprising the earn-out consideration that may be earned upon the achievement of specified milestones. This reallocation of shares from the

58

closing consideration to the earn-out consideration will be measured by comparing the value of the closing consideration, as calculated using the average closing price for the 20 trading days ending two days prior to closing, to the value of such shares using the average closing price for the 20 trading days after the first public announcement of the material terms of a value event relating to TOCOSOL Paclitaxel. For this purpose, a value event means the public announcement of reaching an agreement with the FDA of the material parameters for Phase 3 testing of TOCOSOL Paclitaxel, or the public announcement of entering into a corporate collaboration agreement relating to TOCOSOL Paclitaxel that includes the payment of material consideration to Sonus. If more than one value event occurs prior to September 30, 2005, the average closing price for the 20 trading days after the announcement of the latest to occur of the events will be used to reallocate shares. If no value event occurs prior to September 30, 2005, then no reallocation will take place. Promptly following the final determination of the number of shares constituting the closing consideration, such shares of Sonus common stock comprising the closing consideration will be distributed to the stockholders of Synt:em S.A.

        Contingent Consideration.    An additional issuance of Sonus shares having a value of $500,000 is payable on the date that is 45 business days following the receipt of the consolidated audited financial statements of Sonus from its independent auditor for the fiscal year ended December 31, 2005. At the closing these shares will be deposited into an escrow account and will be subject to claims for indemnification by Sonus under the terms of the Amended and Restated Stock Purchase Agreement. If no claims are made prior to the payment date of such payment, then 100% of such shares will be distributed to the stockholders of Synt:em S.A.

        Earn-out Consideration.    The remaining portion of the stock purchase consideration that is not included in the closing consideration or the contingent consideration is payable only upon the achievement of specified earn-out events on or before eight years following the closing. Half of the earn-out consideration is payable on the date of initiation of the first human dosing in a Phase 2 clinical trial of a qualified Synt:em S.A. product candidate under a U.S. Investigational New Drug application or such other drug application, approvable by the applicable ministry of health as Sonus, in its discretion, determines. The remaining portion of the earn-out consideration will be paid upon the occurrence of any of the following events:

•

initiation of the first human dosing in a Phase 2 clinical trial of a second qualified Synt:em S.A. product candidate under a U.S. Investigational New Drug application or such other drug application approvable by the applicable ministry of health as Sonus determines; or



•

initiation of Phase 3 clinical trials of a Synt:em S.A. qualified product candidate.

        Regardless of a whether a qualified Synt:em S.A. product candidate becomes the subject of Phase 2 or Phase 3 clinical trials, the total amount of the earn-out consideration will be paid upon entering into a definitive collaboration agreement with respect to the development or commercialization of any Synt:em S.A. qualified product candidate that includes the payment of material consideration to Sonus or Synt:em S.A.

        To facilitate achievement of the earn-out events, Sonus agreed that for a period of up to five years, or until all earn-out payments have been made, Sonus will fund and support at least two regulatory pre-clinical programs of Sonus and Synt:em S.A. running continuously. The decision of which pre-clinical programs to pursue will be made by the Board of Directors of Sonus and strategic and project committees to be established by Sonus. In making a determination, the Board of Directors of Sonus and strategic and project committees of Sonus will evaluate scientific viability, market

59

opportunity and economic feasibility of product candidates. Additionally, an earn-out event will be deemed to occur if any of the following occurs:

•

with respect to half of the earn-out consideration, Sonus terminates the clinical, pre-clinical or development program for a product candidate that has been determined to satisfy the scientific viability, market opportunity and economic feasibility tests;



•

with respect to half of the earn-out consideration, Sonus sells, assigns or licenses a product candidate and such sale, assignment or license would result in Sonus losing control over the clinical and development program of the product candidate; or



•

with respect to the total amount of the earn-out consideration or any remaining portion not yet paid, Sonus liquidates Synt:em S.A. or substantially reduces its activities and work force.

        However, Sonus can reduce the funding or support of a pre-clinical program for a product candidate, without causing an earn-out event, if the Board of Directors of Sonus determines that it is in the best interests of Sonus and its stockholders to reduce such funding or support and that the failure to take such action could reasonably be determined to result in a breach of the fiduciary duties of the Board of Directors of Sonus. Any period of time during which Sonus reduces or suspends funding or support shall extend the earn-out period for the period of reduction or suspension.

        Holders of Synt:em S.A. options and warrants who are a party to the Amended and Restated Stock Purchase Agreement will be required to deliver to Sonus an irrevocable waiver of their right to exercise outstanding options or warrants held by them. In addition, the parties have agreed to use commercially reasonable efforts prior to the closing of the acquisition to obtain agreement from holders of options and warrants who are not a party to the Amended and Restated Stock Purchase Agreement to waive their right to exercise and terminate any outstanding options and warrants held by them.

Escrow Deposits

        In order to secure the indemnification obligations of the Synt:em S.A. stockholders, as described below, portions of the stock purchase consideration will be deposited into a third-party escrow account. Portions of the escrow deposits will be released to Sonus in the event Sonus prevails on a claim for indemnification from the Synt:em S.A. stockholders and any remaining balance in the escrow deposits not distributed to Sonus, and not subject to a claim for indemnification prior to the expiration of the escrow, will be distributed to the stockholders of Synt:em S.A. The escrow deposits include a deposit account for a portion of the closing consideration, a deposit account for the amount of the research tax credit payable in the first quarter of 2005 and a deposit account for consideration payable upon achievement of the earn-out events described above.

Indemnification Escrow.

        At the closing, Sonus will deposit into an escrow account shares of Sonus common stock having a value of $500,000. Such shares will be subject to claims for indemnification by Sonus under the terms of the Amended and Restated Stock Purchase Agreement. If no claims are made prior to the date that is 45 business days following the filing of the consolidated audited financial statements of Sonus for the fiscal year ended December 31, 2005 with the SEC, then 100% of such shares will be distributed to the stockholders of Synt:em S.A. If Sonus prevails on a claim for indemnification under the Amended and Restated Stock Purchase Agreement, shares of Sonus having a value equal to the indemnification claim, based upon the average closing price of Sonus common stock for the 20 consecutive trading days ending two days before the closing date, will be returned to Sonus and any remaining shares of Sonus will be distributed to the stockholders of Synt:em S.A.

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Research Tax Credit Escrow.

        At the closing, Sonus will deposit into an escrow account shares of Sonus common stock having a value of 864,454 Euros. Such shares will be held by an escrow agent pending the receipt by Synt:em S.A. of an equal amount from the French tax authorities in the first quarter of 2005. In the event that the amount of the research tax credit paid to Synt:em S.A. is less that 864,454 Euros, then shares of Sonus common stock having a value equal to the deficiency, based on the average trading price of Sonus common stock for the 20 days ending two days prior to the closing date, will be returned to Sonus. For purposes of calculating the value of the deficiency, Euro denominated values will be converted into U.S. Dollars at the applicable exchange rate on the day immediately prior to the date of closing.

Earn-Out Consideration Escrow.

        At the closing, Sonus will deposit into an escrow account the maximum number of shares of Sonus common stock payable upon achievement of the earn-out payments described above. Subject to claims for indemnification made by Sonus described below, shares deposited into this escrow account will be distributed to the stockholders of Synt:em S.A. upon the occurrence of the earn-out events described above. In the event the earn-out events do not occur within eight years following the closing date, all such shares will be returned to Sonus for cancellation.

Transaction Expenses

        Subject to the limitation described below, Sonus will pay or reimburse all of the transaction expenses incurred by Synt:em S.A. and the Synt:em S.A. stockholders, including fees and expenses of legal advisors, accountants, investment bankers, financial advisors, valuation firms or similar professionals, as well as all bonuses, success fees and severance payments to employees of Synt:em S.A. that are payable as a result of the stock purchase; however, in no event will the transaction expenses payable by Sonus exceed 1.72 million Euros. The amount of the transaction expenses of Synt:em S.A. and the Synt:em S.A. stockholders will reduce the closing consideration, but will not reduce the total number of shares of Sonus common stock that may be paid to Synt:em S.A. stockholders. Therefore, the transaction expenses of Synt:em S.A. and the Synt:em S.A. stockholders have the effect of reallocating shares of Sonus common stock from the closing consideration to the earn-out consideration, but do not reduce the aggregate purchase price if all earn-out consideration is earned.

Restricted Shares of Sonus Common Stock

        All shares of Sonus common stock issued pursuant to the Amended and Restated Stock Purchase Agreement will be restricted shares and will not be available for public resale unless such shares are registered under the Securities Act or sold pursuant to an exemption from registration under the Securities Act. See "Related Transaction Agreements—The Stockholders Agreement."

Representations and Warranties

        Each of the managers appointed by the stockholders of Synt:em S.A., individually and not severally, made a number of representations and warranties covering each manager's authority to enter into the Amended and Restated Stock Purchase Agreement and to consummate the transactions contemplated thereby and with respect to the following topics as they relate to Synt:em S.A.:

•

due organization and good standing;



•

capital structure and French capital requirements;



•

absence of undisclosed conflicts with organizational documents and material agreements;

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•

necessary regulatory approvals;



•

financial statements;



•

absence of undisclosed liabilities since the date of Synt:em S.A.'s most recent balance sheet;



•

absence of undisclosed litigation or other legal proceedings;



•

compliance with law and governmental authorities;



•

employees and employment benefit matters;



•

filing and payment of taxes;



•

performance under material contracts;



•

interests in real property owned and leased;



•

title to assets;



•

intellectual property rights;



•

absence of certain changes since the date of Synt:em S.A.'s most recent balance sheet;



•

insurance policies;



•

compliance with environmental laws;



•

maintenance of books and records;



•

finders or brokers engaged in connection with the stock purchase;



•

reserves for and collectibility of accounts receivable;



•

relationships with customers and suppliers;



•

condition of inventories;



•

transactions between Synt:em S.A. and officers, directors or affiliates of Synt:em S.A.;



•

absence of improper payments; and



•

absence of undisclosed product liability claims.

        In addition, each of the stockholders of Synt:em S.A., individually and not severally, made a number of representations and warranties in the Amended and Restated Stock Purchase Agreement regarding each stockholder's ownership of shares of Synt:em S.A. being purchased by Sonus, authority to enter into the Amended and Restated Stock Purchase Agreement and to consummate the transactions contemplated thereby, consents required to consummate the stock purchase and the absence of litigation.

        Sonus made a number of representations and warranties covering its authority to enter into the Amended and Restated Stock Purchase Agreement and to consummate the transactions contemplated thereby and with respect to the following topics as they relate to Sonus:

•

due organization and good standing;



•

absence of conflicts with organizational documents and material agreements;



•

necessary regulatory approvals;



•

capital structure;



•

valid issuance of shares of Sonus common stock to be issued pursuant to the Amended and Stated Stock Purchase Agreement;

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•

reports filed by Sonus with the SEC;



•

absence of undisclosed liabilities since the date of the most recent balance sheet of Sonus;



•

absence of certain changes since the date of Sonus' most recent balance sheet;



•

receipt of a fairness opinion from Needham & Company;



•

filing and payment of taxes;



•

absence of undisclosed litigation or legal proceedings;



•

intellectual property rights;



•

finders or brokers engaged in connection with the stock purchase;



•

compliance with law and governmental authorities;



•

compliance with environmental laws;



•

absence of improper payments;



•

insurance policies;



•

absence of triggering events under Sonus' rights agreement;



•

absence of any delisting notice from Nasdaq;



•

maintenance of books and records; and



•

eligibility to register shares for resale on a Form S-3 registration statement.

        The representations and warranties in the Amended and Restated Stock Purchase Agreement are complicated and not easily summarized. You are urged to carefully read the representations and warranties in the Amended and Restated Stock Purchase Agreement.

Conditions to the Stock Purchase

        The obligations of Sonus and the stockholders of Synt:em S.A. under the Amended and Restated Stock Purchase Agreement are subject to the satisfaction or waiver of certain conditions described in the Amended and Restated Stock Purchase Agreement. These conditions include, but are not limited to:

•

the absence of any order, decree or ruling or any statute or regulation which would prohibit the stock purchase, requires the divestiture of certain assets of Sonus or Synt:em S.A. or seeks the payment of material damages;



•

the receipt of all permits or authorizations from any governmental entities having jurisdiction over the transaction;



•

approval by the stockholders of Sonus of the issuance of the shares issuable under the Amended and Restated Stock Purchase Agreement;



•

the accuracy of representations and warranties that are not qualified by materiality in all material respects and the accuracy of representations and warranties that are qualified by materiality in all respects;



•

the performance of and compliance with covenants in all material respects;



•

the absence of litigation that could prevent consummation of the stock purchase or which could reasonably be expected to have a material adverse effect on Synt:em S.A. or Sonus;

63

•

the absence of any material adverse change to the business, financial condition or results of operations of Synt:em S.A. or Sonus or any event that would materially and adversely affect the ability of Sonus to consummate the stock purchase;



•

Sonus and the stockholders of Synt:em S.A. shall have entered into an escrow agreement;



•

Sonus and the stockholders of Synt:em S.A. shall have entered into the Stockholders Agreement in form attached as an exhibit to the Amended and Restated Stock Purchase Agreement;



•

each of the stockholders of Synt:em S.A. shall have executed and delivered an investment representation statement in the form attached as an exhibit to the Amended and Restated Stock Purchase Agreement;



•

the holders of options or warrants to purchase shares of capital stock of Synt:em S.A. who are parties to the Amended and Restated Stock Purchase Agreement shall have executed and delivered irrevocable waivers in the form attached as an exhibit to the Amended and Restated Stock Purchase Agreement;



•

the receipt of all consents required under material contracts of Synt:em S.A.;



•

Sonus and Michel Kaczorek shall have entered into a mutually acceptable employment agreement and Sonus and certain designated key employees of Synt:em S.A. shall have entered into amendments to such key employees' employment agreements and non-competition agreements; and



•

the amount of cash and cash equivalents of Synt:em S.A. shall not be less than 2.5 million Euros if the closing occurs on or before January 31, 2005, 1.4 million Euros if the closing occurs after January 31, 2005 but on or before February 28, 2005, or 700,000 Euros if the closing occurs after February 28, 2005 but on or before March 31, 2005.

Conduct of Business Prior to the Stock Purchase

        Synt:em S.A.    During the period between the date of the Amended and Restated Stock Purchase Agreement and the closing of the stock purchase, Michel Kaczorek and Caroline Roussel, as the designated managers under the Amended and Restated Stock Purchase Agreement, agreed to cause Synt:em S.A. to conduct its business and maintain its business relationships in a manner that is consistent with the ordinary and usual course of business of Synt:em S.A. and to cause Synt:em S.A. to not take certain specified actions that might materially affect Synt:em S.A. or which could reasonably be expected to cause a material breach of the representations or warranties of the stockholders or managers of Synt:em S.A. made in the Amended and Restated Stock Purchase Agreement without the prior written consent of Sonus.

        Sonus.    During the period between the date of the Amended and Restated Stock Purchase Agreement and the closing of the stock purchase, Sonus agreed to conduct its business and maintain its business relationships in a manner that is consistent with the ordinary and usual course of business of Synt:em S.A. and to not take certain specified actions that might materially affect Sonus or which could reasonably be expected to cause a material breach of the representations or warranties of Sonus made in the Amended and Restated Stock Purchase Agreement without the prior written consent of the sellers' agents for the stockholders of Synt:em S.A.

No Solicitation

        Synt:em S.A. has agreed that it will not solicit, encourage or facilitate any other acquisition proposal for Synt:em S.A. and that it will notify Sonus of any inquiry, expression of interest, proposal or offer that constitutes, or could reasonably be expected to lead to, such an acquisition proposal.

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Synt:em S.A. has agreed to cause each of its officers, directors, employees, agents, and other representatives to not solicit, encourage or facilitate any acquisition proposal for Synt:em S.A.

Indemnification

        Claims for Indemnification.    Each of the stockholders of Synt:em S.A. has agreed to indemnify Sonus for all damages that arise from any breach of such stockholder's representations or warranties or the failure by such stockholder to perform any covenants made by such stockholder. In addition, the stock purchase consideration will be reduced by an amount equal to all damages that arise from any breach of the representations or warranties made by the managers appointed by the Synt:em S.A. stockholders under the Amended and Restated Stock Purchase Agreement or the failure by the managers to perform any covenants made by the managers. Further, Sonus has agreed to indemnify the stockholders of Synt:em S.A. for all damages that arise from any breach by Sonus of its representations or warranties or any failure by Sonus to perform its covenants.

        Expiration of Claims.    Any claim for indemnification or reduction of the stock purchase consideration must be made prior the date that is 18 months following the closing date, at which time the right to state a claim for damages will expire, except for claims relating to title of the shares held by the Synt:em S.A. stockholders, claims of fraud or willful breach or claims arising from the failure to pay transaction expenses incurred by or on behalf of Synt:em S.A. or the Synt:em S.A. stockholders, for which there is no expiration date other than limitations imposed under applicable law.

        Limitations on Amount.    The parties to the Amended and Restated Stock Purchase Agreement agreed to certain limitations on the amount of damages that will be subject to claims for indemnification or reduction of consideration. No claim may be made unless the aggregate amount of all damages incurred exceeds $20,000, in which event all damages may be recoverable. In addition, no party will be entitled to indemnification or be able to reduce the consideration by more than the sum of $500,000 plus 12.5% of the earn-out consideration. In the event the first earn-out payment is not earned prior to expiration of the right to make a claim, no portion of such amount will be subject to indemnification. Further, no party will be able to recover damages in excess of 12.5% of the earn-out consideration if the claim for damages is made more than 45 business days following receipt of the consolidated audited financial statements of Sonus from its independent auditor for the fiscal year ended December 31, 2005. Claims for indemnification or reduction in the stock purchase consideration are the exclusive remedies available to the parties, except for claims relating to title of the shares held by the Synt:em S.A. stockholders, claims of fraud or willful breach or claims arising from the failure to pay transaction expenses incurred by or on behalf of Synt:em S.A. or the Synt:em S.A. stockholders, for which the parties may be entitled to other remedies.

Termination Rights

        The Amended and Restated Stock Purchase Agreement may be terminated under certain circumstances, at any time prior to the consummation of the stock purchase, whether prior to or after approval of the issuance of shares of Sonus common stock by the Sonus stockholders, as summarized below:

•

by mutual written consent of Sonus and the sellers' agent;



•

by Sonus if the stockholders of Sonus fail to approve the issuance of shares of Sonus common stock in accordance with the Amended and Restated Stock Purchase Agreement;



•

by the sellers' agent if Sonus fails to file the Sonus proxy statement prior to January 31, 2005, unless such failure is not within the control of Sonus or its advisors;

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•

by the sellers agent if Sonus fails to hold its stockholder meeting at which the transaction described in this proxy statement is submitted for approval on or before February 28, 2005, or April 28, 2005 if the Sonus proxy statement is reviewed by the SEC;



•

by Sonus or the sellers' agent if the stock purchase has not been consummated by February 28, 2005, or March 31, 2005 if the Sonus proxy statement is reviewed by the SEC, other than as a result of a breach by the terminating party; provided, that Sonus may extend the date to April 30, 2005 if the proxy statement is reviewed by the SEC, holding the stockholders meeting prior to March 31, 2005 is not practical as a result of such review and Sonus extends a loan in the amount of 500,000 Euros to Synt:em S.A., which loan will be forgiven if the stock purchase is not consummated by April 30, 2005;



•

by Sonus if any of the stockholders of Synt:em S.A. has breached or failed to perform in any material respect any of its representations, warranties or covenants and such breach or failure to perform has not been cured within 30 days after receiving notice of such breach or failure; or



•

by the sellers' agent if Sonus has breached or failed to perform in any material respect any of its representations, warranties or covenants and such breach or failure to perform has not been cured within 30 days after receiving notice of such breach or failure.

Directors and Officers of Sonus After the Stock Purchase

        The directors and officers of Sonus prior to the stock purchase will continue to be directors and officers of Sonus after the stock purchase. In addition, Michel Kaczorek, the Chief Executive Officer of Synt:em S.A., will be appointed to the Board of Directors of Sonus and will assume the position of Chief Science and Technology Officer of Sonus.

Amendment and Waiver

        The Amended and Restated Stock Purchase Agreement may be amended only be a written agreement duly signed by Sonus and the sellers' agent. Any waiver must be in writing and signed by the party against whom enforcement is sought. The sellers' agent may effect a waiver on behalf of the stockholders of Synt:em S.A.

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RELATED TRANSACTION AGREEMENTS

        The following is a brief summary of certain aspects of a Stockholders Agreement that will be entered into at the closing among Sonus and the stockholders of Synt:em S.A. This summary may not contain all of the information that is important to you. To understand the Stockholders Agreement fully, and for a more complete description of the legal terms of the Stockholders Agreement, you are urged to read the Stockholders Agreement carefully. A copy of the Stockholders Agreement is attached as Appendix B. The following also includes a brief summary of certain aspects of employment and non-competition agreements that will be entered into at the closing between Sonus and certain employees of Synt:em S.A.

Stockholders Agreement

Registration Rights

        As a condition to closing the stock purchase under the Amended and Restated Stock Purchase Agreement, Sonus and the stockholders of Synt:em S.A. will enter into a Stockholders Agreement, a form of which is attached to this proxy statement as Appendix B. Pursuant to the Stockholders Agreement, Sonus will agree to register for resale the shares of the Sonus common stock issuable under the Amended and Restated Stock Purchase Agreement on a registration statement on Form S-3 to be filed with the SEC within five days following the closing date.

        At any time prior to the date that is eight years after the closing of the stock purchase, if Sonus proposes to file a registration statement in an underwritten offering, then each of the holders of Sonus common stock received in the stock purchase may request to have such holder's shares included in the registration statement. Such registration opportunities are unlimited, but the number of shares that can be registered may be eliminated entirely or reduced in certain situations at the request of the underwriters managing the offering of shares being registered.

        The registration rights will terminate on the earlier to occur of such time as all shares issued under the Amended and Restated Stock Purchase Agreement have been sold pursuant to an effective registration statement or in accordance with Rule 144, or such time as all shares issued under the Amended and Restated Stock Purchase Agreement may be sold under Rule 144 without limitations on the number of shares that may be sold.

Lock-Up on Shares of Sonus Common Stock

        The Stockholders Agreement also includes a lock-up provision, pursuant to which each stockholder of Synt:em S.A. will agree not to sell or otherwise transfer shares of Sonus common stock received at the closing under the Amended and Restated Stock Purchase Agreement. The restrictions on transfer will lapse on December 31, 2005.

        If Sonus does not register the shares of Sonus common stock issued under the Amended and Restated Stock Purchase Agreement for resale or the registration statement is not declared effective by the SEC within nine months following the closing date, the restrictions on transfer imposed by the lock-up shall terminate on the date that is nine months following the closing date.

Employment Agreements

        As a condition to closing the stock purchase under the Amended and Restated Stock Purchase Agreement, Sonus or Synt:em S.A. will enter into employment agreements on substantially the following terms with each of the following individuals:

        Michel Kaczorek will be employed as our Senior Vice President and Chief Science and Technology Officer pursuant to an employment letter agreement. Under the employment agreement, Dr. Kaczorek is entitled to receive an annual base salary of 152,068 Euros and is eligible to participate in the bonus

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plan established by our Board of Directors for our executive officers, with a target bonus of 35% of Dr. Kaczorek's base salary. Dr. Kaczorek's base salary will increase to 180,000 Euros upon the successful completion of a qualified financing of Sonus, and this increase will be paid retroactively to the date of the closing of the stock purchase under the Amended and Restated Stock Purchase Agreement. In addition, Dr. Kaczorek is entitled to receive a one-time bonus equal to six-months base salary upon the successful completion of the stock purchase under the Amended and Restated Stock Purchase Agreement. Dr. Kaczorek will also receive options to purchase 165,000 shares of our common stock, subject to approval by our Board of Directors.

        Gordon Waldron will be employed as Synt:em S.A.'s Managing Director pursuant to an employment agreement. Under the employment agreement, Mr. Waldron is entitled to receive an annual base salary of 112,050 Euros and is eligible to participate in the bonus plan established by our Board of Directors for our executive officers, with a target bonus of 25% of Mr. Waldron's base salary. Mr. Waldron's base salary will increase to 135,000 Euros upon the successful completion of a qualified financing of Sonus, and this increase will be paid retroactively to the date of the closing of the stock purchase under the Amended and Restated Stock Purchase Agreement. In addition, Mr. Waldron is entitled to receive a one-time bonus equal to twelve-months base salary upon the successful completion of the stock purchase under the Amended and Restated Stock Purchase Agreement.

        Caroline Roussel will be employed as Synt:em S.A.'s Vice President, Director of Operations, pursuant to an employment agreement. Under the employment agreement, Ms. Roussel is entitled to receive an annual base salary of 81,900 Euros and is eligible to participate in the bonus plan established by our Board of Directors for our executive officers, with a target bonus of 25% of Ms. Roussel's base salary. Ms. Roussel's base salary will increase to 95,000 Euros upon the successful completion of a qualified financing of Sonus, and this increase will be paid retroactively to the date of the closing of the stock purchase under the Amended and Restated Stock Purchase Agreement. In addition, Ms. Roussel is entitled to receive a one-time bonus equal to six-months base salary upon the successful completion of the stock purchase under the Amended and Restated Stock Purchase Agreement.

        Jamal Temsamani will be employed as Synt:em S.A.'s Vice President, Pre-clinical Research and Development, pursuant to an employment agreement. Under the employment agreement, Dr. Temsamani is entitled to receive an annual base salary of 99,244 Euros and is eligible to participate in the bonus plan established by our Board of Directors for our executive officers, with a target bonus of 25% of Dr. Temsamani's base salary. Dr. Temsamani's base salary will increase to 125,000 Euros upon the successful completion of a qualified financing of Sonus, and this increase will be paid retroactively to the date of the closing of the stock purchase under the Amended and Restated Stock Purchase Agreement. In addition, Dr. Temsamani is entitled to receive a one-time bonus equal to six-months base salary upon the successful completion of the stock purchase under the Amended and Restated Stock Purchase Agreement.

        Luc-Andre Granier will be employed as Synt:em S.A.'s Vice President, Clinical Development and Medical Director, pursuant to an employment agreement. Under the employment agreement, Dr. Granier is entitled to receive an annual base salary of 112,050 Euros and is eligible to participate in the bonus plan established by our Board of Directors for our executive officers, with a target bonus of 25% of Dr. Granier's base salary. Dr. Granier's base salary will increase to 130,000 Euros upon the successful completion of a qualified financing of Sonus, and this increase will be paid retroactively to the date of the closing of the stock purchase under the Amended and Restated Stock Purchase Agreement. In addition, Dr. Granier is entitled to receive a one-time bonus equal to six-months base salary upon the successful completion of the stock purchase under the Amended and Restated Stock Purchase Agreement.

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        Roger Lahana will be employed as Synt:em S.A.'s Vice President, Discovery, pursuant to an employment agreement. Under the employment agreement, Dr. Lahana is entitled to receive an annual base salary of 99,244 Euros and is eligible to participate in the bonus plan established by our Board of Directors for our executive officers, with a target bonus of 25% of Dr. Lahana's base salary. Dr. Lahana's base salary will increase to 110,000 Euros upon the successful completion of a qualified financing of Sonus, and this increase will be paid retroactively to the date of the closing of the stock purchase under the Amended and Restated Stock Purchase Agreement. In addition, Dr. Lahana is entitled to receive a one-time bonus equal to six-months base salary upon the successful completion of the stock purchase under the Amended and Restated Stock Purchase Agreement.

        The terms of the employment agreements with each of the above persons are still in the process of being finally negotiated. It is possible that the final terms may vary from those set forth above. Pursuant to the terms of the foregoing employment agreements, each employee is eligible to participate in all plans providing general benefits for Synt:em S.A. employees in France. Each of the foregoing employment agreements also contains non-competition and confidentiality provisions. The non-competition provisions generally provide for restrictions on competitive activities concerning the development of peptide-conjugated drugs for a period of 24 months from the date of termination of employment.

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INFORMATION CONCERNING SONUS

Business

        Sonus Pharmaceuticals, Inc. is focused on the development of novel drugs for the oncology market that may offer improved administration, tolerability, safety and effectiveness. Our business strategy is as follows:

•

develop proprietary formulations of therapeutic drugs utilizing our TOCOSOL® drug delivery technology;



•

apply the TOCOSOL technology platform to additional oncology products; and



•

identify and acquire additional therapies and technologies in oncology and related fields in order to expand our product pipeline and corporate capabilities.

        Our proprietary TOCOSOL technology platform has been designed to address the formulation challenges of therapeutic drugs. Development of drugs with our TOCOSOL technology may result in products with improved preparation and dosing convenience, decreased incidences of side effects and equivalent or better efficacy. The TOCOSOL technology uses vitamin E oil (tocopherol) and tocopherol derivatives to solubilize and stabilize drugs, making them easier to formulate and deliver into the body. While the TOCOSOL technology is particularly suited to injectable drugs that are poorly soluble in water, research continues into the application of new versions of this technology that could prove applicable to oral or other routes of delivery.

        Our lead product, TOCOSOL Paclitaxel, is a novel formulation of paclitaxel, one of the world's most widely prescribed anti-cancer drugs. Paclitaxel, a member of the taxane family of cancer drugs, is the active ingredient in Taxol, which is approved in the United States for the treatment of breast, ovarian and non-small cell lung cancers and Kaposi's sarcoma. Our product, TOCOSOL Paclitaxel, is a ready-to-use, injectable paclitaxel emulsion. We believe that clinical trials to date have demonstrated that TOCOSOL Paclitaxel compares favorably with approved taxane products and other new paclitaxel formulations under development (safety and efficacy remain to be proven); offers the convenience of a ready-to-use formulation that does not require time consuming preparation prior to administration; can be administered to patients by a short 15-minute infusion, compared to the one- to three-hour infusion that is typically required with the currently marketed taxane products; does not require any special intravenous tubing, filters or other apparatus; and does not require dilution, which results in administration of small volumes of 25 to 35 milliliters compared to several hundred milliliters for Taxol.

        We continue to invest in the research and development of new products, including those that could extend the application of our TOCOSOL drug delivery technology. We are currently evaluating a number of early stage therapeutic drug formulations utilizing the TOCOSOL technology, including potential product candidates based on the camptothecin molecule. The camptothecin molecule family is poorly soluble and difficult to formulate for administration to humans. There are currently two marketed hydrophilic (water-based) camptothecin analogs that are based on chemical modifications to the camptothecin molecule. Irinotecan, which is marketed under the name Camptosar, is indicated for treatment of colorectal cancer. Topotecan, which is marketed under the name Hycamtin, is indicated for treatment of ovarian and non-small cell lung cancers. Our research and development efforts on these product candidates are preliminary and we cannot give any assurance that any of these compounds will be successful or that they will progress to clinical trials. Advancing one or more of these potential products into human clinical trials is dependent on several factors including technological feasibility and commercial opportunity.

        We believe that the pending acquisition of Synt:em S.A. offers the opportunity to expand our technology base and product candidate pipeline. In addition to our internal research and development

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efforts, we may consider other acquisitions of complementary products and technologies to expand our product pipeline.

Additional Information

        A detailed description of the business of Sonus and other matters related to Sonus is incorporated by reference in this proxy statement. For additional information, see "Where You Can Find More Information" on page 79.

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INFORMATION CONCERNING SYNT:EM S.A.

        Synt:em S.A. is a drug discovery company developing novel drugs using its proprietary drug design technologies to discover and develop drug transport conjugates. Synt:em S.A.'s principal focus is to create new chemical entities by re-engineering existing compounds and improving their pharmacological behavior. Synt:em S.A. employs its technology platform to design short peptide sequences, known as Pep:trans peptides, that are conjugated with clinically validated and other compounds in order to improve the transport of pharmaceutical agents to specific organs and/or enhance cellular uptake. Synt:em S.A. has initially focused on applying its expertise to the development of novel therapeutics for the treatment of pain, cancer, and diseases of the central nervous system.

        Synt:em S.A. was founded in 1995 initially as a peptide synthesis and molecular modeling company (the former initially known as In Silico Screening, later as Acti:map™). In 1997, a second technology platform known as Pep:trans was initiated. This is a family of proprietary peptides that are able to cross complex biological membranes such as the blood brain barrier or cell membranes. Synt:em S.A.'s approach is to covalently link active moieties like existing or new drugs to Pep:trans in order to improve their pharmacological behavior and create a proprietary new chemical entity (NCE).

        Synt:em S.A. currently has three development projects underway. Syn1001, an analgesic product for acute pain, is in Phase 1 clinical trial to achieve the first human proof of concept of the Pep:trans technology. A second product for inflammatory and neuropathic pain, Syn1002, is in late preclinical development. A third product in early preclinical stage, Syn1003, is in evaluation for chronic and / or acute pain treatment.

        Several other drug candidates are under investigation including an anti-neoplastic agent for brain cancer, an anti-angiogenic molecule for solid tumors and two risk-sharing programs partnered with other biotechnology companies. Synt:em S.A. believes that additional product candidates can be taken through in vitro proof-of-concept and the most promising compounds through further in vivo validation and future clinical development. Synt:em S.A. continues to invest in research and development of other candidates using its Pep:trans technology in oncology to develop new medicines for the treatment of brain and lung cancer.

        Synt:em S.A. is based in Nîmes, France where the company has its headquarters and its leased facilities for research and development in computing, chemistry and synthesis, biochemistry and bio-analysis. Synt:em S.A. has its cell and animal biology units in Montpellier at the Institut de Génétique Moléculaire on the research campus of the CNRS (France's National Scientific Research Center) and the University of Montpellier.

        Synt:em S.A. is aware of a number of competitors developing peptide-based delivery technologies, including large pharmaceutical, chemical and biotechnology concerns and universities and other research institutions. These competitors have substantially greater financial, technical and human resources than Synt:em S.A. and have substantially greater experience in developing products, obtaining regulatory approvals and marketing and manufacturing medical products.

Senior Management

Michel Kaczorek, Ph.D., President & Chief Executive Officer

        Dr. Kaczorek has over 20 years of experience in the biotechnology industry, and was a founder of Synt:em S.A. in 1995. Dr. Kaczorek received a Ph.D. in Microbiology and a Ph.D. in Virology at the University of Paris. In addition, he trained as a post-doctorate at Harvard Medical School and at the Institut Pasteur in Paris. Dr. Kaczorek was in charge of research and development at Pasteur Vaccins in the area of recombinant vaccines. He was also one of the co-founders of Protéine Performance, SA, where he was the scientific director. He has published numerous scientific articles in international journals and has jointly filed 10 patent applications. He is a non-executive director on the board of

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Clinigenetics, a French-based biotech company involved in vascular diseases. He is also a member of the Board of France Biotech, the French professional biotech association.

Gordon Waldron, Vice President, Finance & Chief Financial Officer

        Mr. Waldron joined Synt:em S.A. as Chief Financial Officer in 1997. Mr. Waldron is a graduate of Duke University. Prior to joining Synt:em S.A., Mr. Waldron had 10 years of diversified finance experience in France, the United Kingdom and the United States. He spent four years as Controller (both in France and the United States) with Spie Batignolles, a large French industrial conglomerate. In 1992, he joined Texas Instruments Software (Paris) as Finance Director and then served as Group Finance Manager for Texas Instruments Software EMEA (London) consolidating several entities across Europe, Africa and the Middle East. He has been a team member in various acquisition and sale projects, has negotiated financing and commercial transactions. Mr. Waldron is a non-executive director on the board of Molecular Cytogenetics Laboratories, a private French biotechnology company.

Dr. Jamal Temsamani, Ph.D., Vice President, Pre-clinical Research & Development

        Dr. Temsamani joined Synt:em S.A. in March 1998 and is currently the Vice President of Pre-clinical Research & Development. Dr. Temsamani received his Ph.D. in Molecular Biology in 1989 from The University of Montpellier in France. After completing a post-doctoral fellowship at the Worcester Foundation for Biomedical Research, he joined Hybridon, Inc. (Boston), where he served as Senior Research Scientist, Associate Director, and Director of Discovery Group. In 1997, he was appointed Scientific Director of Hybridon Europe, where he was responsible for supervising and coordinating European collaborations. He has published several scientific articles and is co-inventor of more than 15 patents.

Dr. Roger Lahana, Ph.D., Vice President, Discovery

        Dr. Lahana joined Synt:em S.A. in 1997 and is currently the Vice President of Discovery. Dr. Lahana holds two Ph.D.s, one in molecular chemistry and one in coordination chemistry, both from the Paul Sabatier University, Toulouse, France. Previous posts have been as a senior scientist at the CNRS, head of computational chemistry at Pierre Fabre Medicament and Managing Director at Oxford Molecular (Southern Europe). Dr. Lahana has published several articles in scientific journals or conference proceedings. He has created and developed the Acti:map™ technology and he is a co-inventor of three patents. He is also a scientific adviser to the CNRS, an associate editor of Drug Discovery Today, a member of the American Chemical Society and of the QSAR Society, as well as the President of GGMM (the French Molecular Modeling Society).

Dr. Luc-Andre Granier, M.D., Ph.D., Vice President, Clinical Development and Medical Director

        Dr. Granier joined Synt:em S.A. in 2001 as Vice President, Clinical Development and Medical Director. Dr. Granier has extensive experience in managing the clinical development of central nervous system medicines. He has run a large number of clinical research studies and has led several drug development programs for new medicines for the treatment of neurological disorders including pain, migraine, Parkinson's disease, Alzheimer's disease and depression. Prior to joining Synt:em S.A., Dr. Granier was Senior Clinical Research Physician / Clinical Pharmacologist at Eli Lilly & Co. Dr. Granier received his M.D. and his three Ph.Ds. from the University Louis Pasteur of Strasbourg, France.

Caroline Roussel, Vice President, Director of Operations

        Ms. Roussel is a co-founder of Synt:em S.A. and joined Synt:em S.A. in October 1995. She is currently the Company's Director of Operations. Ms. Roussel was trained as an engineer in industrial

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biology at the University of Compiègne and graduated from the European Institute for Entrepreneurial Activity management school in Montpellier. In 1993, she was sales manager at Protéine Performance interfacing between researchers and partners from industry and academia for recombinant protein expression projects. In addition, she has marketing and sales experience with a variety of biotechnology products. From 1995 to 1999, she acted as Marketing Director for Synt:em S.A. where she was in charge of the custom peptide business unit, setting up the facilities and was strongly involved in research and development project coordination.

Scientific Advisory Board

        Synt:em S.A. also has an international Scientific Advisory Board of seven industry experts who hold M.D. or Ph.D. degrees and who have expertise on drug discovery and development, including preclinical trials and manufacturing and formulation. Experts from both Europe and the United States advise Synt:em S.A. on its primary focus of pain management and oncology.

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SECURITY OWNERSHIP OF PRINCIPAL STOCKHOLDERS, DIRECTORS AND
MANAGEMENT OF SONUS

        Set forth below is certain information as of January 24, 2005 regarding the beneficial ownership of the common stock of Sonus by (i) any person who was known by Sonus to own more than five percent (5%) of the voting securities of Sonus, (ii) all directors and nominees, (iii) the Chief Executive Officer and the other most highly compensated executive officers of Sonus, and (iv) all current directors and executive officers as a group.

*

Less than 1%

(1)

Beneficial ownership is determined in accordance with the rules of the Securities and Exchange Commission and generally includes voting or investment power with respect to securities. Shares of Common Stock subject to options and warrants currently exercisable, or exercisable within 60 days of the Record Date, are deemed outstanding for computing the percentage of the person holding such options but are not deemed outstanding for computing the percentage of any other person. Except as indicated by footnote, and subject to community property laws where applicable, the persons named in the table have sole voting and investment power with respect to all shares of Common Stock shown as beneficially owned by them.

(2)

Includes 1,162,851 shares, 110,475 of which are issuable upon exercise of warrants, held by S.A.C. Capital Associates, LLC ("Associates") and 662,851 shares, 110,475 of which are issuable upon exercise of warrants, held by S.A.C. Healthco Fund, LLC ("Healthco"). The warrants are exercisable only to the extent that the exercise would not cause the aggregate number of shares owned by Associates and Healthco to exceed 9.99% of the outstanding shares of Common Stock of the Company. S.A.C. Capital Advisors, LLC ("Advisors") and S.A.C. Capital Management, LLC ("Management") share voting and investment power with respect to shares held by Associates and

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Healthco. Steven A. Cohen is the managing member of Advisors and the owner of Management. Mr. Cohen disclaims beneficial ownership of the shares held by Associates and Healthco.

(3)

Includes 428,262 warrants exercisable within 60 days of the Record Date.

(4)

Includes 275,638 warrants exercisable within 60 days of the Record Date.

(5)

Consists of 212,199 shares owned directly and 543,506 options exercisable within 60 days of the Record Date.

(6)

Consists of 3,981 shares owned directly and 107,603 options exercisable within 60 days of the Record Date.

(7)

Mr. Fuhrman has no shares exercisable within 60 days of the Record Date.

(8)

Consists of 15,000 options exercisable within 60 days of the Record Date.

(9)

Consists of 1,500 shares owned directly and 105,133 options exercisable within 60 days of the Record Date.

(10)

Consists of 1,700 shares owned directly and 90,133 options exercisable within 60 days of the Record Date.

(11)

Consists of 115,133 options exercisable within 60 days of the Record Date.

(12)

Includes 976,508 options exercisable within 60 days of the Record Date.

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NO DISSENTERS' RIGHTS OF APPRAISAL

        Under Delaware law, the holders of Common Stock are not entitled to dissenters' rights of appraisal in connection with the proposed issuance of shares to the Synt:em S.A. stockholders or the acquisition of Synt:em S.A.

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STOCKHOLDER PROPOSALS

        Sonus stockholders may submit proposals for consideration at future stockholders meetings. The time for Sonus stockholders to submit proposals for the 2005 annual meeting of stockholders has passed. However, with respect to the 2006 annual meeting of stockholders, proposals of stockholders of Sonus that such stockholders desire to have included in Sonus' proxy statement relating to such meeting must be received at Sonus' principal executive offices no later than 120 calendar days prior to the anniversary of the mailing date of the proxy statement for Sonus' 2005 annual meeting. Matters pertaining to such proposals, including the number and length thereof, eligibility of persons entitled to have such proposals included and other aspects are regulated by the Securities Exchange Act of 1934, Rules and Regulations of the Securities and Exchange Commission and other laws and regulations to which interested person should refer. Sonus anticipates that its 2006 annual meeting will be held in April or May 2006.

        Proxies submitted to Sonus will confer discretionary authority to vote on matters proposed by stockholders if a proponent of a proposal fails to notify the Company at least 45 days prior to the anniversary of mailing of the prior year's proxy statement, without any discussion of the matter in the proxy statement. With respect to the Company's 2005 Annual Meeting of Stockholders, if the Company has not been provided with notice of a stockholder proposal by January 31, 2005, the Company will be allowed to use is voting authority as described above.

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WHERE YOU CAN FIND MORE INFORMATION

        We file annual, quarterly and current reports, proxy statement and other information with the SEC. You can read and copy any materials we file with the SEC at the SEC's public reference room at 450 Fifth Street, N.W., Washington, D.C. 20549. You can obtain information about the operation of the SEC's public reference room by calling the SEC at 1-800-SEC-0330. The SEC also maintains a web site that contains information we file electronically with the SEC, which you can access at www.sec.gov. Our electronic SEC filings are also available through our website at www.sonuspharma.com. Information contain on our website is not incorporated into this proxy statement and does not constitute a party of this proxy statement.

        Statements contained in this proxy statement regarding the contents of any contract or other document are not necessarily complete and each such statement is qualified in its entirety by reference to such contract or other document file as an exhibit with the SEC.

        This proxy statement does not constitute the solicitation of a proxy in any jurisdiction to or from any person to whom or from whom it is unlawful to make such proxy solicitation in such jurisdiction. You should rely only on the information we have provided to vote your shares at the special meeting. We have not authorized any person to provide information other than that provided in this proxy statement. We have not authorized anyone to provide you with different information. This proxy statement is dated                        , 2005. You should not assume that the information in this proxy statement is accurate as of any date other than that date or that any information contained in any document we have incorporated by reference is accurate as of any date other than the date of the document incorporated by reference, and the mailing of this proxy statement to stockholders does not create any implication to the contrary.

79

INCORPORATION OF INFORMATION BY REFERENCE

        The following information contained in documents filed by the Company with the United States Securities and Exchange Commission are hereby incorporated by reference in this proxy statement:

        1.     Our Annual Report on Form 10-K, filed on March 12, 2004.

        2.     Our Quarterly Report on Form 10-Q, filed on April 21, 2004.

        3.     Our Quarterly Report on Form 10-Q, filed on August 16, 2004.

        4.     Our Quarterly Report on Form 10-Q, filed on November 15, 2004.

By Order of the Board of Directors

Michael A. Martino
President and Chief Executive Officer

                        , 2005

80

UNAUDITED PRO FORMA CONDENSED COMBINED FINANCIAL STATEMENTS

        The following Unaudited Pro Forma Condensed Combined Balance Sheet as of September 30, 2004 and the Unaudited Pro Forma Condensed Combined Statement of Operations data for the nine months ended September 30, 2004 and the year ended December 31, 2003 are based on the historical financial statements of Sonus and Synt:em S.A. after giving effect to the proposed acquisition using the purchase method of accounting and applying the estimates, assumptions and adjustments described in the accompanying Notes to the Unaudited Pro Forma Condensed Combined Financial Statements. The historical financial information of Synt:em S.A. was prepared in accordance with accounting principles generally accepted in France ("French GAAP") presented in Euros. Accordingly, the Synt:em S.A. amounts have been adjusted to reflect differences between French GAAP and accounting principles generally accepted in the United States (U.S. GAAP), and were translated to U.S. dollars. The unaudited pro forma condensed combined financial data is based on estimates and assumptions which are preliminary. The Unaudited Pro Forma Condensed Combined Financial Statements do not purport to represent what Sonus' financial position or results of operations would actually have been if the proposed acquisition had in fact occurred on the dates indicated or to project Sonus' financial position or results of operations as of any future date or for any future period. Investors are cautioned not to place undue reliance on this unaudited pro forma financial information.

        For pro forma purposes:

•

Sonus' balance sheet as of September 30, 2004 has been combined with Synt:em S.A.'s balance sheet as of September 30, 2004 as if the proposed acquisition had occurred on September 30, 2004;



•

Sonus' unaudited statement of operations for the nine months ended September 30, 2004 has been combined with Synt:em S.A.'s unaudited statement of operations for the nine months ended September 30, 2004 as if the proposed acquisition had occurred on January 1, 2003; and



•

Sonus' statement of operations for the year ended December 31, 2003 has been combined with Synt:em S.A.'s statement of operations for the year ended December 31, 2003 as if the proposed acquisition had occurred on January 1, 2003.

        The Synt:em S.A. amounts combined in the pro forma combined financial statements referred to above were translated to U.S. dollars using a spot rate of 1.24174 as of September 30, 2004 and an average rate of 1.22284 and 1.11926 for the nine months ended September 30, 2004 and the year ended December 31, 2003, respectively, except for property and equipment and stockholders' equity, which have been translated using historical exchange rates.

        Under the purchase method of accounting, the total estimated pro forma purchase price of approximately $15.4 million, calculated as described in Note 1 to these Unaudited Pro Forma Condensed Combined Financial Statements, is allocated to the net tangible and intangible assets acquired in connection with the acquisition, based on their estimated fair values as of September 30, 2004. These amounts, which are based on management's judgment, are estimates of fair values of the net assets reflected in these Unaudited Pro Forma Condensed Combined Financial Statements. A final determination of these fair values will be based on an independent third party's estimate of the fair values of the intangible assets and management's estimates of the fair values of the remaining net assets. This final valuation will be based on the actual net tangible and intangible assets of Synt:em S.A. that exist as of the closing date. In addition, the actual closing consideration will be determined based on certain factors and conditions at closing and then subject to further adjustments through September 30, 2005 if certain milestones are met by Sonus. The effect of the final valuation and the final determination of the closing consideration could cause material differences to the following pro forma information.

F-1

        These Unaudited Pro Forma Condensed Combined Financial Statements and accompanying notes should be read in conjunction with the historical financial statements and the related notes thereto of Synt:em S.A. and "Management's Discussion and Analysis of Financial Condition and Results of Operations of Synt:em S.A.," included in this proxy statement. This data should also be read in conjunction with Sonus' historical financial statements and related notes thereto and "Management's Discussion and Analysis of Financial Condition and Results of Operations," which are incorporated herein by reference to Sonus' Annual Report on Form 10-K for the year ended December 31, 2003 and Quarterly Report on Form 10-Q for the nine months ended September 30, 2004.

F-2

Sonus Pharmaceuticals, Inc.
Unaudited Pro Forma Condensed Combined Balance Sheet
September 30, 2004
(U.S. GAAP basis, in thousands)