Security	Date	Code	Shares	Price	A/D	Owned after	D/I	Nature of ownership
Common Stock^F1,F3	Jun 22, 2015	A	65,810	—	A	65,810	D
Common Stock^F2,F3	Jun 22, 2015	A	66,153	—	A	66,153	D
Common Stock^F4,F3	Jun 22, 2015	A	94,410	—	A	94,410	I	See Footnote
Common Stock^{F5,F3,F7,F9,F10}	Jun 22, 2015	A	506,165	—	A	506,165	I	See Footnotes
Common Stock^{F6,F3,F8,F9,F10}	Jun 22, 2015	A	6,103,031	—	A	6,103,031	I	See Footnotes

Table II — derivative securities

No Table II lines on this filing.

Explanation of responses

F1Acquisition of 65,810 shares of Common Stock of Alexion Pharmaceuticals, Inc. (the "Issuer") directly held by Felix J. Baker in connection with the Merger Agreement (as defined below).
F10The Adviser serves as the Investment Adviser to 667 and Life Sciences (collectively, the "Funds"). In connection with the services provided by the Adviser, the Adviser receives an asset-based management fee that does not confer any pecuniary interest in the securities held by the Funds. Baker Bros. Advisors (GP) LLC (the "Adviser GP") is the Adviser's sole general partner. Julian C. Baker and Felix J. Baker are principals of the Adviser GP. The Adviser has complete and unlimited discretion and authority with respect to the investment and voting power of the securities held by the Funds. The general partners of the Funds relinquished to the Adviser all discretion and authority with respect to the investment and voting power of the securities held by the Funds. Julian C. Baker, Felix J. Baker, the Adviser GP and the Adviser disclaim beneficial ownership of the securities held directly by the Funds except to the extent of their pecuniary interest therein, and this report shall not be deemed an admission that any of Julian C. Baker, Felix J. Baker, the Adviser GP or the Adviser is a beneficial owner of such securities for purposes of Section 16 or any other purpose.
F2Acquisition of 66,153 shares of Common Stock of the Issuer directly held by Julian C. Baker in connection with the Merger Agreement (as defined below).
F3Acquisition of common shares in connection with the completion of the acquisition of Synageva Biopharma Corp. ("Synageva") by the Issuer pursuant to the Agreement and Plan of Reorganization (the "Merger Agreement") dated May 5, 2015, by and among the Issuer, Synageva, Merger Sub Inc. and Galaxy Merger Sub LLC. Pursuant to the Merger Agreement, each of Synageva's common shares were exchanged for $115 in cash and 0.6581 shares of the Issuers common stock (the "Merger Consideration").
F4Acquisition of 94,410 shares of Common Stock of the Issuer pursuant to the Merger Agreement directly held by FBB Associates. Felix J. Baker and Julian C. Baker are the sole partners of FBB Associates. Felix J. Baker and Julian C. Baker each disclaims beneficial ownership of the securities held directly by FBB Associates except to the extent of their pecuniary interest therein, and this report shall not be deemed an admission that Felix J. Baker or Julian C. Baker is a beneficial owner of such securities for purposes of Section 16 or any other purpose.
F5Acquisition of 506,165 shares of Common Stock of the Issuer pursuant to the Merger Agreement directly held by 667, L.P. ("667"), a limited partnership of which the sole general partner is Baker Biotech Capital, L.P., a limited partnership of which the sole general partner is Baker Biotech Capital (GP), LLC.
F6Acquisition of 6,103,031 shares of Common Stock of the Issuer pursuant to the Merger Agreement directly held by Baker Brothers Life Sciences, L.P. ("Life Sciences"), a limited partnership of which the sole general partner is Baker Brothers Life Sciences Capital, L.P., a limited partnership of which the sole general partner is Baker Brothers Life Sciences Capital (GP), LLC.
F7After giving effect to the transaction reported herein, and as a result of their ownership interest in Baker Biotech Capital (GP), LLC, Felix J. Baker and Julian C. Baker may be deemed to have an indirect pecuniary interest in the Issuer's shares of Common Stock reported in column 5 of Table I directly held by 667, a limited partnership of which the sole general partner is Baker Biotech Capital, L.P., a limited partnership of which the sole general partner is Baker Biotech Capital (GP), LLC, due to Baker Biotech Capital, L.P.'s right to receive an allocation of a portion of the profits from 667.
F8After giving effect to the transaction reported herein, and as a result of their ownership interest in Baker Brothers Life Sciences Capital (GP), LLC, Felix J. Baker and Julian C. Baker may be deemed to have an indirect pecuniary interest in the Issuer's shares of Common Stock reported in column 5 of Table I directly held by Life Sciences, a limited partnership of which the sole general partner is Baker Brothers Life Sciences Capital, L.P., a limited partnership of which the sole general partner is Baker Brothers Life Sciences Capital (GP), LLC, due to Baker Brothers Life Sciences Capital, L.P.'s right to receive an allocation of a portion of the profits from Life Sciences.
F9Includes 12,763, 33,608 and 20,226 shares of Common Stock of the Issuer held directly, respectively by Julian C. Baker, Felix J. Baker and Stephen R. Biggar received from their service on the Board of Directors of Synageva ("Synageva Board") and its predecessor ("Predecessor Board"). Julian C. Baker, a principal of Baker Bros. Advisors LP (the "Adviser"), served on the Board of a predecessor of Synageva as a representative of the Funds (as defined below). Felix J. Baker, a principal of the Adviser, and Stephen R. Biggar, an employee of the Adviser served on the Board of Synageva. Felix J. Baker serves on the Board of the Issuer (the "Board"). Pursuant to the policies of the Adviser, Julian C. Baker, Felix J. Baker and Stephen R. Biggar do not have any right to any of Synageva's or the Issuer's securities issued as part of their service on the Board, the Synageva Board or the Predecessor Board and the Funds (as defined below) are entitled to receive all the pecuniary interest in the securities issued. The Funds (as defined below) each own an indirect proportionate pecuniary interest in the stock options or common shares received for service on the Board, the Synageva Board or the Predecessor Board. Solely as a result of Felix J. Baker's and Julian C. Baker's ownership interest in the general partners of the general partners of the Funds, Felix J. Baker and Julian C. Baker may be deemed to have an indirect pecuniary interest in the stock options and common shares received from their service on the Board, the Synageva Board or the Predecessor Board (i.e. no direct pecuniary interest).

Remarks

The shares originally reported were based on estimates calculated using the ratios in the merger agreement. The below amendments reflect shares actually received, which differ immaterially from the shares originally reported. Felix J. Baker is a director of Alexion Pharmaceuticals, Inc. (the "Issuer"). By virtue of their representation on the Board of Directors of the Issuer, for purposes of Section 16 of the Securities Exchange Act of 1934, as amended, the reporting persons other than Felix J. Baker are deemed directors by deputization of the Issuer.