Biogen Idec to Expand Oncology Pipeline with Acquisition of Conforma Therapeutics

Cambridge, MA and San Diego, CA (May 3, 2006) - Biogen Idec (NASDAQ: BIIB) and Conforma Therapeutics Corporation, a privately held biopharmaceutical company focused on the design and development of novel drugs for the treatment of cancer, today announced that they have signed a definitive merger agreement for the acquisition of Conforma by Biogen Idec.

Conforma, founded in 1999, is focused on the discovery and development of drugs that inhibit heat shock protein 90 (HSP90) molecules, which are involved in protecting and supporting the growth of cancer cells across a range of tumor types, and which also play a role in tumor resistance to a number of leading cancer therapies. The company has advanced two compounds into Phase I clinical trials: CNF1010, a proprietary form of the geldanamycin derivative 17-AAG; and CNF2024, a totally synthetic, orally bioavailable HSP90 inhibitor.

“Global leadership in oncology -- from discovery to development to commercialization -- is a major strategic objective for Biogen Idec,” said James C. Mullen, Biogen Idec’s President and Chief Executive Officer. “Conforma’s platforms in the promising area of HSP90 antagonists provide significant opportunities to develop drugs for a range of solid tumors. Through this transaction, Biogen Idec will also broaden our therapeutic opportunities in the cancer field while adding Conforma’s talented scientific team to our oncology group.”

“Biogen Idec is a premier biotechnology organization that has pioneered important medical advances in areas of high unmet need. Working together will better enable the development of our innovative therapeutics and will open opportunities for further application of our technology platforms,” said Lawrence C. Fritz, Ph.D., President and Chief Executive Officer of Conforma. “Biogen Idec’s global resources and commitment to advancing breakthrough therapies make them an ideal partner for us and we look forward to joining them.”

The transaction is expected to close in the second quarter of 2006. Upon completion, Biogen Idec will acquire all of the issued and outstanding shares of the capital stock of Conforma for $150 million, payable at closing, and up to an additional $100 million upon the achievement of certain development milestones. The transaction, which has been approved by the boards of directors of both companies, is subject to approval by the stockholders of Conforma and satisfaction of other customary closing conditions. Montgomery & Co., LLC was the exclusive financial advisor to Conforma in connection with this transaction.

Following the transaction’s close, Conforma’s operations and employees will be integrated into Biogen Idec’s San Diego campus, the company’s oncology center of excellence. Conforma’s North American and European rights to Amrubicin, an anthracycline anticancer drug that Conforma had licensed from Dainippon Sumitomo Pharma Co., Ltd., will be transferred out of Conforma into a new start-up specialty pharmaceuticals company, Cabrellis Pharmaceuticals Corporation, prior to the close of this transaction.
Conforma’s Technology Platform: Inhibiting HSP90 Chaperones

Cancer occurs when certain signaling proteins, such as kinases and nuclear receptors, mutate or become over expressed. Recent discoveries in cell biology have demonstrated that many of these key signaling proteins require the action of a family of molecular “chaperones” known as the HSP90 chaperone family in order to be properly folded and thus maintain activity. Drugs that bind to HSP90 chaperones may induce these critical signaling proteins to degrade, leading to tumor cell death. Conforma’s drug candidates specifically bind to activated forms of HSP90 and thus attack tumor cells, sparing normal tissues.

In addition to its lead products, Conforma has developed a diverse library of compounds that affect the HSP90 family of molecular chaperones and have the potential to lead to the development of other treatments.

About Conforma Therapeutics

Conforma Therapeutics, a San Diego-based biopharmaceutical company, is focused on the design and development of novel drugs for the treatment of cancer. Conforma’s internal discovery efforts have been focused on drugs that target the cellular HSP90 family of molecular “chaperones” that control protein shape or conformation, including that of key signaling molecules involved in the growth and survival of tumor cells. Further information regarding Conforma is available at www.conformacorp.com.
About Biogen Idec

Biogen Idec creates new standards of care in oncology, neurology and immunology. As a global leader in the development, manufacturing, and commercialization of novel therapies, Biogen Idec transforms scientific discoveries into advances in human healthcare. For product labeling, press releases and additional information about the company, please visit www.biogenidec.com.
Biogen Idec Safe Harbor

This press release contains forward-looking statements regarding the acquisition of Conforma and the development of HSP90 antagonists. These statements are based on the companies’ current beliefs and expectations. Drug development involves a high degree of risk. Factors which could cause actual results to differ materially from the companies’ current expectations include: the risk that unexpected concerns may arise from additional data or analysis, that regulatory authorities may require additional information, further studies, or may fail to approve the drug, or that the company may encounter other unexpected hurdles. For more detailed information on the risks and uncertainties associated with Biogen Idec’s drug development and other activities, see the periodic reports of Biogen Idec Inc. filed with the Securities and Exchange Commission. Biogen Idec assumes no obligation to update any forward-looking statements, whether as a result of new information, future events or otherwise.

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Jose Juves

Director, Public Affairs

Biogen Idec

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