EXHIBIT 99


Explanation of Responses:
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(1)  The securities to which this report relates are held by S.A.C. Capital
     Associates, LLC ("Associates") and S.A.C. Healthco Fund, LLC ("Healthco"),
     limited liability companies of which S.A.C. Capital Advisors, LLC
     ("Advisors") and S.A.C. Capital Management, LLC ("Management") are
     investment managers. Pursuant to investment agreements, each of Advisors
     and Management share all investment and voting power with respect to the
     securities held by Associates and Healthco. The Reporting Person controls
     both Advisors and Management. In accordance with Instruction 4(b)(iv) the
     entire amount of the Issuer's securities held by Associates and Healthco is
     reported herein. The transaction reported on herein was consummated by
     Associates. The Reporting Person disclaims any beneficial ownership of any
     of the Issuer's securities to which this report relates for purposes of
     Section 16 of the Securities Exchange Act of 1934, as amended, except to
     the extent of its indirect pecuniary interest therein, and this report
     shall not be deemed an admission that the Reporting Person is the
     beneficial owner of such securities for purposes of Section 16 or for any
     other purposes.