Alexion Pharmaceuticals Inc. Updates Previously Announced Phase III Results For PRIMO-CABG2 Study

CHESHIRE, Conn., March 13 /PRNewswire-FirstCall/ -- Alexion Pharmaceuticals, Inc. today updated results from its Phase III PRIMO-CABG2 clinical trial with pexelizumab at the American College of Cardiology. As previously announced on November 25, 2005, the results show that the drug reduced the primary endpoint, but did not meet the pre-specified threshold for statistical significance. The PRIMO-CABG2 trial enrolled moderate-to-high risk coronary artery bypass graft (CABG) surgery patients and was sponsored jointly by Alexion and Procter and Gamble Pharmaceuticals.

Peter K. Smith M.D., Professor and Chief of Thoracic Surgery, Duke University Medical Center presented the updated results. Pexelizumab reduced the primary endpoint of the combined incidence of death or nonfatal myocardial infarction (heart attack) through postoperative day 30 (POD 30) following CABG surgery (placebo=16.3% vs. pexelizumab=15.2%, 7% relative reduction, p=0.20). Mortality through POD 30 was reduced from 4.6% in the placebo group to 3.8% (17% relative reduction) in the pexelizumab group (p=0.18). Myocardial infarction through POD 30 was reduced modestly with pexelizumab (placebo=13.3% vs. pexelizumab=12.6%, 5% relative reduction, p=0.31). Additionally, pexelizumab appeared to be well tolerated with an adverse event profile comparable to placebo.

In addition to the results from PRIMO-CABG2, Dr. Smith presented the updated results of a pooled mortality analysis that was performed across five placebo controlled trials conducted with pexelizumab in patients undergoing either CABG surgery or in patients experiencing an acute myocardial infarction treated with either thrombolytic therapy or percutaneous intervention (PCI). These analyses showed that in the 9,233 patient ITT cohort, pexelizumab significantly reduced mortality through 30 days (placebo=4.3% vs pexelizumab=3.3%, relative reduction=24%, p=0.009).

Pexelizumab, a terminal complement inhibitor, is a monoclonal antibody fragment that inhibits complement-mediated tissue damage. The Phase III trial titled Pexelizumab for Reduction of Infarction and Mortality in Coronary Artery Bypass Graft Surgery 2 (PRIMO-CABG2), included 4,254 patients and was conducted at 249 U.S. and international study sites.

"The PRIMO-CABG2 study did not replicate the significant reduction in myocardial infarction that was observed previously in PRIMO-CABG1 and therefore did not achieve statistical significance for the co-primary endpoint of death or myocardial infarction through POD 30," said Dr. Smith. "However, we continue to be encouraged by the consistent mortality benefit observed in the overall PRIMO-CABG program that appears to extend across all acute cardiovascular trials performed with pexelizumab to date."

"As originally announced in November 2005, we are disappointed that pexelizumab did not achieve the primary efficacy endpoint in PRIMO-CABG2 of reducing death or heart attack," said Dr. Scott A. Rollins, Senior Vice President of Drug Development at Alexion. "However, pexelizumab continues to be associated with a reduction in overall mortality across cardiac indications, as compared to placebo. We currently await the completion and subsequent analysis of the ongoing APEX-AMI trial that we expect to conclude enrollment in the near future. We expect that the results of the APEX trial will assist in determining the future of pexelizumab therapy in acute cardiovascular disease."

As announced in late January, the APEX-AMI trial has enrolled over 5,000 patients at more than 300 U.S. and international study sites. Enrollment in the APEX-AMI trial is continuing.

About Alexion

Alexion Pharmaceuticals is a biotechnology company working to develop and deliver life-changing drug therapies for patients with serious and life- threatening medical conditions. Alexion is engaged in the discovery and development of therapeutic products aimed at treating patients with a wide array of severe disease states, including hematologic diseases, cancer, cardiovascular diseases and autoimmune disorders. Alexion's two lead product candidates, eculizumab and pexelizumab, are currently undergoing evaluation in several clinical development programs, including two Phase III trials of Soliris(TM) (eculizumab) for the treatment of paroxysmal nocturnal hemoglobinuria (PNH). Under the Special Protocol Assessment (SPA) process, the FDA has agreed to the design of protocols for two trials of Soliris(TM) (eculizumab) in PNH patients that could, if successful, serve as the primary basis of review for approval of a licensing application for eculizumab in the PNH indication. On January 26, 2006, Alexion announced that the first of those two PNH trials achieved its co-primary endpoints with statistical significance. On November 23, 2005, the Company announced that its Phase III trial of pexelizumab in coronary artery bypass graft (CABG) surgery patients undergoing cardiopulmonary bypass (CPB), known as the PRIMO-CABG2 trial did not achieve its co-primary endpoints. Results from the PRIMO-CABG2 trial indicate that the trial is unlikely to be sufficient for filing for licensing approval of pexelizumab in the CABG indication. On February 3, 2006, the Company announced that enrollment in its Phase III trial of pexelizumab in AMI patients, known as APEX-AMI, would be capped at approximately 5,000 patients, ending near the beginning of March. Thereafter, the Company was encouraged by leading academic researchers involved in the APEX-AMI trial to allow enrollment to proceed beyond those numbers. Along with its partner, Procter and Gamble Pharmaceuticals (P&G), Alexion recently agreed to support continued enrollment in APEX-AMI for a limited period of time. The anticipated timing of completion of APEX-AMI will be announced after further discussion with P&G, and after new definitive determinations have been made. Although the APEX-AMI trial is the subject of an SPA, the number of patients actually enrolled may not be sufficient for the FDA to consider the trial compliant with the SPA. In such event, if results of the APEX-AMI trial are successful, we may still seek approval to market pexelizumab in the AMI indication, but the FDA regulatory process may not be subject to any benefits of the SPA process. The pexelizumab trials are conducted in collaboration with P&G. 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 at: http://www.alexionpharm.com.

This news release contains forward-looking statements, including statements related to the results and timing of clinical trials and the potential timing and results of regulatory applications to market he Company's product candidates. Forward-looking statements are subject to factors that may cause Alexion's results and plans to differ from those expected, including delays in completion of ongoing clinical trials, delays in completion of analysis of clinical trial results, timing and evaluation by regulatory agencies of the results of these and other clinical trials, the results of pre-clinical or clinical studies (including termination or delay in clinical programs), the need for additional research and testing, decision of the FDA or other regulatory authorities not to approve (or to materially limit) marketing of one or both of Alexion's two drug candidates, 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 December 31, 2005, and in our other filings with the Securities and Exchange Commission. P&GP retains the development rights and the termination rights discussed in Alexion's Form 10-K 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.

Contacts: Alexion Pharmaceuticals, Inc. Scott A. Rollins, Ph.D. Senior Vice President, Drug Development (203) 272-2596 Rx Communications Patricia Garrison (Scientific Media) (917) 322-2567 Rhonda Chiger (Investors) (917) 322-2569 Noonan/Russo Matt Haines (Business and Financial Media) (212) 845-4235

Alexion Pharmaceuticals, Inc.

CONTACT: Scott A. Rollins, Ph.D., Senior Vice President, Drug Developmentof Alexion Pharmaceuticals, Inc., +1-203-272-2596; Scientific Media -Patricia Garrison, +1-917-322-2567, Investors - Rhonda Chiger, +1-917-322-2569, both of Rx Communications; Business and Financial Media - MattHaines of Noonan/Russo, +1-212-845-4235

Web site: http://www.alexionpharm.com/