8-K

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

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                                    FORM 8-K

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                                 CURRENT REPORT
                     PURSUANT TO SECTION 13 OR 15(d) OF THE
                         SECURITIES EXCHANGE ACT OF 1934

Date of Report (Date of earliest event reported) September 12, 2003



                          ALEXION PHARMACEUTICALS, INC.
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             (Exact Name of Registrant as Specified in its Charter)


                                                                             
Delaware                                        0-27756            13-3648318
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(State or Other Jurisdiction                  (Commission    (IRS Employer
of Incorporation)                             File Number)   Identification No.)


352 Knotter Drive, Cheshire, CT                                   06410
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(Address of Principal Executive Offices)                        (Zip Code)





Registrant's telephone number, including area code:       (203) 272-2596
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                                 Not Applicable
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          (Former Name or Former Address, if Changed Since Last Report)




Item 5.  Other Events

         On September 12, 2003, the Company entered into an agreement to sell an
aggregate of 3,600,000 shares of its common stock, $.0001 par value per share,
to a syndicate led by Bear, Stearns & Co. Inc. The sale is made under the
Company's shelf-registration statement (Registration No. 333-47594 filed October
6, 2000) relating to the possible sale from time to time of the Company's
securities. This Form 8-K is filed to incorporate the exhibit hereto into that
registration statement.

Item 7.  Financial Statements, Pro Forma Financial Information and Exhibits.

         (c)  Exhibits.

         5.1      Opinion of Fulbright & Jaworski L.L.P.

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                                   SIGNATURES

         Pursuant to the requirements of the Securities Exchange Act of 1934,
the registrant has duly caused this report to be signed on its behalf by the
undersigned hereunto duly authorized.

                                            ALEXION PHARMACEUTICALS, INC.

Date: September 16, 2003                    By: /s/ David Keiser
                                                ----------------
                                            Name: David Keiser

                                            Title: President



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EX-5.1

                  [LETTERHEAD OF FULBRIGHT & JAWORSKI L.L.P.]



                              September 16, 2003


Alexion Pharmaceuticals, Inc.
352 Knotter Drive
Cheshire, CT 06410

   Re: Alexion Pharmaceuticals, Inc.

Dear Sirs:

   We have acted as counsel to Alexion Pharmaceuticals Inc. (the "Company") in
connection the sale of 3,600,000 shares of common stock of the Company, par
value $0.0001 per share (the "Shares"), pursuant to an Underwriting Agreement
(the "Underwriting Agreement"), dated as of September 12, 2003, by and between
the Company and Bear, Stearns & Co. Inc., as Representative of the several
underwriters named therein. A prospectus supplement, dated September 12, 2003,
has been filed under Rule 424(b)(5) of the Securities Act of 1933, as amended
(the "Act"), on September 16, 2003, with respect to the sale of the Shares, to
the prospectus dated October 16, 2000, which was part of a Registration
Statement on Form S-3 (Registration No. 333-47594), as amended, which became
effective under the Act on October 16, 2000.

   We have examined such corporate records, other documents and questions of
law as we have deemed necessary or appropriate for the purposes of this opinion.

   Upon the basis of such examination, we advise you that, in our opinion, the
Shares have been duly and, when issued and paid for in accordance with the
Underwriting Agreement, will be validly authorized, legally issued, fully paid
and non-assessable.

   We consent to the filing of this opinion as an exhibit to a Current Report
on Form 8-K which is incorporated by reference into the Registration Statement
and to the reference to this firm under the caption "Legal Matters" in the
Supplement contained therein and elsewhere in the Registration Statement and
Supplement. This consent is not to be construed as an admission that we are a
party whose consent is required to be filed with the Registration Statement
under the provisions of the Act.



                                             Very truly yours,


                                             /S/  FULBRIGHT & JAWORSKI L.L.P.