EXHIBIT 99.1


Alexion Pharmaceuticals Reports Preliminary Results Of Its Phase III
PRIMO-CABG Trial

    Conference Call Scheduled for Tuesday, August 5 at 9:00 a.m. Eastern Time

    CHESHIRE, Conn., Aug. 4 /PRNewswire-FirstCall/ -- Alexion
Pharmaceuticals,Inc. (Nasdaq: ALXN) announced today preliminary results of its
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Phase III study in a large, multinational trial consisting of greater than 3,000
patients undergoing coronary artery bypass graft ("CABG") surgery with
cardiopulmonary bypass, a study referred to as "Pexelizumab for Reduction in
Infarction and Mortality in Coronary Artery Bypass Graft Surgery," or
PRIMO-CABG. The primary endpoint in this trial was a composite of the incidence
of death or myocardial infarction, measured at 30 days post-procedure, in
patients undergoing CABG without concomitant valve surgery.

    Although there was reduction in the primary endpoint, it was not achieved
with statistical significance. However, key pre-specified secondary endpoints
consisting of the same composite in the total study population, which included
all patients undergoing CABG with or without concomitant valve surgery, were
achieved. Several other pre-specified secondary endpoints were met as well.

    The company announced that further details of PRIMO-CABG will be provided
after all data analyses are complete, and will be presented by Dr. Verrier in
the Late-Breaking Clinical Trials Session of the 2003 Scientific Sessions
Meeting of the American Heart Association in Orlando, Florida, during the second
week of November. Dr. Edward D. Verrier is William K. Edmark Professor and Chief
of Cardiovascular Surgery at the University of Washington, and Chairman of the
PRIMO-CABG Steering Committee.

    "These preliminary observations are encouraging in that they support the
role of Pexelizumab in potentially further improving patient outcomes in bypass
surgery," noted Dr. Verrier. "I look forward to presenting the exciting
PRIMO-CABG clinical results at the AHA scientific sessions this November."

    "Although our objective to achieve statistical significance in the primary
endpoint was not met, this study has provided us with encouraging clinical
information, which extends important positive results seen in our Phase II
trial," said Dr. Leonard Bell, Chief Executive Officer of Alexion. "The
achievement of the composite of death or myocardial infarction in the total
population reinforces our enthusiasm for progressing pexelizumab development and
we feel that the fully completed analysis will lead to findings that have the
promise of significant clinical, scientific, and commercial merit. We look
forward, in collaboration with Procter & Gamble Pharmaceuticals, to completing
the final data analysis and discussing with the FDA the next steps in going
forward."

    Conference Call Information

    Alexion will host a conference call to discuss matters mentioned in this
release. The call is scheduled for Tuesday, August 5th at 9:00 a.m., Eastern
Time. To participate in this call, dial 913-981-4900, confirmation code 501849,
shortly before 9:00 a.m. A replay of the call will be available for a limited
period following the call, beginning 12:00 p.m., Eastern Time. The replay number
is 719-457-0820, confirmation code 501849.



    Alexion is engaged in the discovery and development of therapeutic products
aimed at treating patients with a wide array of severe disease states, including
cardiovascular and autoimmune disorders, inflammation and cancer. Alexion's two
lead product candidates, pexelizumab and eculizumab, are currently undergoing
evaluation in several clinical development programs. Alexion is developing
pexelizumab, an antibody fragment, in collaboration with Procter & Gamble
Pharmaceuticals. Together the firms have completed a Phase III clinical study
with pexelizumab in CABG patients undergoing cardiopulmonary bypass, and two
large Phase II studies with pexelizumab in acute myocardial infarction patients.
In addition, eculizumab is currently in Phase II clinical trials in rheumatoid
arthritis and membranous nephritis, and has been evaluated in pilot programs for
the treatment of paroxysmal nocturnal hemoglobinuria and dermatomyositis.
Alexion is engaged in discovering and developing a pipeline of additional
antibody therapeutics targeting severe unmet medical needs, through its wholly
owned subsidiary, Alexion Antibody Technologies, Inc. This press release and
further information about Alexion Pharmaceuticals, Inc. can be found on the
World Wide Web at: http://www.alexionpharm.com.
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    This news release contains forward-looking statements. Such statements are
subject to factors that may cause Alexion's results and plans to differ from
those expected, including the results of pre-clinical or clinical
studies(including termination or delay in clinical programs), the need for
additional research and testing, delays in arranging satisfactory manufacturing
capability, inability to acquire funding on timely and satisfactory terms,
delays in developing or adverse changes in commercial relationships, the
possibility that results of earlier clinical trials are not predictive of safety
and efficacy results in later clinical trials, dependence on Procter & Gamble
Pharmaceuticals for development and commercialization of pexelizumab, the risk
that third parties won't agree to license any necessary intellectual property to
us on reasonable terms, and a variety of other risks set forth from time to time
in Alexion's filings with the Securities and Exchange Commission, including but
not limited to the risks discussed in Alexion's Annual Report on Form 10-K for
the year ended July 31, 2002 and Quarterly Report on Form 10-Q for the quarter
ended October 31, 2002. In particular, Alexion is not currently able to predict
the reaction of the United States Food and Drug Administration (FDA) and other
regulatory agencies to the results of the PRIMO-CABG trial. Such reactions may
include, but not be limited to, the view that the results may be sufficient for
filing and approval of a Biologics License Application (BLA), supportive of the
filing and approval of a BLA together with additional studies, or not supportive
of the filing or approval of a BLA. Further, Alexion is not currently able to
predict the reaction of P&GP to the results of the PRIMO-CABG trial, including
how those results may affect P&GP's views of pexelizumab for CABG or other
indications. P&GP retains the development rights and the termination rights
discussed in Alexion's Form 10-K and 10-Q referred to above. Alexion does not
intend to update any of these forward-looking statements to reflect events or
circumstances after the date hereof, except when a duty arises under law.

     Alexion Pharmaceuticals, Inc.     Euro RSCG Life NRP
     Leonard Bell, M.D.                Ernie Knewitz (Media)
     Chief Executive Officer           (212) 845-4253
     (203) 272-2596

     Rx Communications
     Rhonda Chiger (Investor) 917-322-2569