News Release

Yale and Alexion report advance in spinal cord repair

Peer-Reviewed Publication

Noonan/Russo Communications

NAGOYA, JAPAN, Oct. 25, 1999 -- Researchers from the Yale University School of Medicine and Alexion Pharmaceuticals, Inc. (Nasdaq: ALXN) today reported that transplanting genetically modified pig cells into surgically damaged spinal cords of non-human primates can regenerate the myelin sheath around the injured fragment of the spinal cord. Alexion believes that these results represent a critical milestone in progressing its spinal cord product into patient trials.

The report, entitled "Xenotransplantation of Transgenic Pig Myelin Forming Cells Promotes Axonal Regeneration and Restores Conduction Across the Transected Spinal Cord," is based on research conducted in the laboratories of Dr. Jeffrey D. Kocsis of the Department of Neurology, Yale University School of Medicine, and Dr. William L. Fodor, Senior Director of Xenotransplantation at Alexion Pharmaceuticals, Inc. and their colleagues.

"This promising data demonstrates that immunoprotected transgenic pig cells can survive and regenerate myelin sheaths around damaged neurons within the spinal cords of non-human primates," said Stephen Squinto, Senior Vice President and Chief Technology Officer of Alexion. "Together with our findings also presented today which showed that these transgenic pig cells both engraft and restore electrical conductance in rodent models of spinal injury, these data suggest that this approach may lead to the development of a new therapy for spinal cord injury patients."

Specific antibody binding to the surface of a foreign cell initiates a process called the "complement" cascade, which results in the destruction of the foreign cell. Complement-mediated rejection of nerve cell xenografts presents a major obstacle to effectively replacing damaged cells in the central nervous system. Alexion scientists address this problem in two ways. First, they produce pig cells that reduce or eliminate the expression of certain pig sugars which are targeted by the triggering antibodies. Second, the company designs myelin-producing transgenic pig cells that are covered by a protective shield of human complement inhibitor proteins.

"This particular study showed that, following transplantation, these engineered cells survived, restored nerve cell function, produced myelin and ensheathed the damaged nerve fibers," said Dr. Kocsis. "We have seen successful engraftment of Alexion's immunoprotected transgenic pig cells and remyelination of damaged nerve fibers in four out of five primates studied. Furthermore, we are encouraged that our results obtained with transgenic pig cell transplantation into injured primate spinal cords reflect the results we've seen earlier in rodent models of spinal injury."

"The achievement of survival and functioning of our patented transgenic cells after transplantation into the damaged spinal cord of a primate represents a particularly important milestone in view of the high degree of similarity between the primate and human immune systems," said Leonard Bell, M.D., President and Chief Executive Officer of Alexion. "Therefore, we are now focusing our efforts on optimization of product manufacturing and definition of a potential clinical program for the treatment of patients with spinal cord injuries."

According to the National Spinal Cord Injury Association, at least 200,000 patients have suffered a traumatic spinal cord injury, and there are approximately 8,000 new spinal cord injury patients in the U.S. each year. Most spinal cord injury patients are young adults and slightly over half of these patients suffer the most severe form of non-fatal spinal injury, quadriplegia, or loss of use of all four limbs.

Alexion Pharmaceuticals, Inc. was founded in 1992 and is engaged in the development of selective immunotherapeutic drugs that generally are designed to inhibit the disease-causing segments of the immune system while preserving the disease-preventing aspects of the immune system. The Company is developing three technology platforms: C5 Complement Inhibitors and Apogen T-Cell Therapeutics which together target severe cardiovascular and autoimmune disorders; and xenografts for organ transplantation. Xenotransplantation refers to the transplantation of non-human cells, tissues and/or organs into human patients.

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 unexpected pre-clinical or clinical results, the need for additional research and testing, delays in manufacturing, access to capital and funding, delays and adverse changes in development of commercial relationships and a variety of 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, 1998. Alexion undertakes no obligation to publicly release results of any of these forward looking statements which may be made to reflect events or circumstances after the date hereof or to reflect the occurrence of unanticipated events.


Editor's Note:This release is available on the Internet at

Alexion Pharmaceuticals, Inc.
Leonard Bell
President & CEO
203-776-1790 Ext.103

Noonan/Russo Communications, Inc.
Ernie Knewitz
212-696-4455 Ext. 204

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