PRNewswire - November 5, 2001

"Together with our two advancing C5 inhibitors, pexelizumab and 5G1.1, this pioneering discovery strengthens our position at the forefront of emerging technologies aimed at the treatment of immune related diseases including rheumatoid arthritis, psoriasis, Crohn's disease and diabetes," said Leonard Bell, M.D. President and CEO of Alexion. " In addition to acquiring exclusive rights to a lead monoclonal antibody product candidate, which we will begin to evaluate for its potential utility in treating patients with chronic immune diseases, we look forward to additional therapeutic targets that may emerge from our research alliance."

Dr. Carl Figdor, Professor, Department of Tumor Immunology, University Medical Center St. Radboud, Nijmegen, The Netherlands, and colleagues, have reported the discovery of a novel human dendritic cell receptor that is critical in initiating primary immune responses and also enhancing HIV infection of T-cells. These findings were published last year in two papers appearing in the journal Cell (Vol. 100, March 3, 2000) and an additional publication in Nature Immunology (Vol. 1, No. 4, 2000). Dr. Figdor's discovery, DC-SIGN, is the first specific dendritic cell surface receptor identified. Furthermore, Dr. Figdor's team has developed effective inhibitors, including monoclonal antibodies, of both DC-SIGN and L-SIGN. These identified monoclonal antibodies have shown efficacy in significantly inhibiting T-cell activation, suggesting a role in inhibiting inflammation, and also in blocking HIV infection of T-cells. Alexion and UMC are also cooperating in a research and development alliance to further characterize the functional role of DC-SIGN and L-SIGN with a focus on various models of human autoimmune disease. The collaboration is also expected to utilize Alexion's antibody library technology to identify new proteins unique to human dendritic cells.

"We are excited to be working collaboratively with Alexion to commercialize antibodies to DC-SIGN and L-SIGN for the treatment of various immune disorders and to increase our understanding of dendritic cell biology through a research and discovery collaboration", commented Dr. Figdor. "Although there was significant interest in our discovery by several groups, we chose to work exclusively with Alexion due to the combination of their novel antibody discovery technologies resident in their Alexion Antibody Technologies subsidiary in San Diego and their antibody development capabilities in Connecticut. We look forward to a productive broad-based relationship with Alexion aimed at expediting the commercialization of our discoveries."

Dendritic cells have recently come to be appreciated as critical controllers of the immune system. In order for an immune response against foreign antigens to occur, these antigens must be displayed by so-called antigen-presenting cells. While dendritic cells are an extremely rare immune cell type, they are the most potent of all the antigen presenting cells. Dendritic cells capture antigens in the peripheral tissues, process and display the antigen fragments on their cell surface, and then migrate from the periphery to the T-cell areas of the lymphoid organs. There, they attract resting T-cells, present their antigen load, thus activating the T-cells to begin an immune response. This process appears to be controlled in part by the newly identified molecule DC-SIGN.

Dr. Figdor and colleagues discovered that the initial contact between resting T cells and antigen presenting dendritic cells occurs via the novel dendritic cell specific receptor identified as DC-SIGN (Dendritic Cell-Specific, ICAM-3 Grabbing Non-integrin). Dr. Figdor's team reported that the binding that occurs between the dendritic cells and resting T cells via DC-SIGN allows the T cell receptor to scan the surface of the dendritic cell to identify foreign antigens and initiate the immune response. DC-SIGN also appears critical in mediating the spread of HIV from infected dendritic cells to T cells.

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 5G1.1, are currently in eight clinical development programs. Alexion is developing pexelizumab, an antibody fragment, in collaboration with Procter & Gamble Pharmaceuticals. Together the firms have completed a Phase IIb clinical study with pexelizumab in cardiopulmonary bypass patients, and are currently conducting two large Phase II studies with pexelizumab in acute myocardial infarction patients. Alexion's other lead product candidate, 5G1.1, has completed a Phase II trial for the treatment of rheumatoid arthritis. 5G1.1 is also in Phase II trials for the treatment of membranous nephritis and for lupus nephritis, and in earlier stage clinical trials for the treatment of dermatomyositis and pemphigoid. Additionally, through its wholly owned subsidiary, Alexion Antibody Technologies, Inc., Alexion is engaged in discovering and developing a portfolio of additional antibody therapeutics targeting severe unmet medical needs. This press release and further information about Alexion Pharmaceuticals, Inc. can be found on the World Wide

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

This news release contains forward-looking statements. Such statements are subject to certain factors which may cause Alexion's plans to differ or results to vary from those expected, including the results of pre-clinical or clinical studies (including termination or delay in clinical programs or inability to move forward to the next Phase of clinical development), the need for additional research and testing, delays in developing or arranging satisfactory manufacturing capability, inability to access capital and funding on a timely basis and on favorable terms, delays in development of or adverse changes in status of commercial relationships, the possibility that favorable results of earlier clinical trials are not predictive of safety and efficacy results in larger clinical trials, dependence on Procter & Gamble Pharmaceuticals for performance of development and commercial matters related to pexelizumab ,the risk that third parties won't agree to license us on reasonable terms their intellectual property necessary for us to develop and commercialize our products, 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, 2001. Except in special circumstances in which a duty to update arises under law when prior disclosure becomes materially misleading in light of subsequent events, Alexion does not intend to update any of these forward-looking statements to reflect events or circumstances after the date hereof or to reflect the occurrence of unanticipated events.

011105
PR011105

AEGiS presents published material, reprinted with permission and neither endorses nor opposes any material. All information contained on this website, including information relating to health conditions, products, and treatments, is for informational purposes only. It is often presented in summary or aggregate form. It is not meant to be a substitute for the advice provided by your own physician or other medical professionals. Always discuss treatment options with a doctor who specializes in treating HIV.

Copyright ©1980, 2001. AEGiS. All materials appearing on AEGiS are protected by copyright as a collective work or compilation under U.S. copyright and other laws and are the property of AEGiS, or the party credited as the provider of the content. .