September 30, 2003

News Release: Dyax and MedImmune Enter into Library License Agreement for Discovery of Therapeutic Antibodies

Dyax Corp. (Nasdaq: DYAX) today announced that it has granted a non-exclusive license to its proprietary antibody phage display libraries for the discovery of therapeutic antibodies to MedImmune, Inc. (Nasdaq: MEDI). Under the terms of the agreement, Dyax will receive upfront and annual technology license fees, clinical milestone payments, and royalties on net sales of products that may result from MedImmune's use of the Dyax libraries. The agreement provides MedImmune a license to Dyax's antibody phage display technology and patent rights, as well as sublicenses to relevant third-party antibody phage display patents that may be used with Dyax's antibody phage display technology. 'We are very pleased to enter into this agreement with MedImmune, who is an established leader in the development and marketing of therapeutic antibodies,'commented Jack H. Morgan, Senior Vice President, Corporate Development &Business Operations for Dyax. He added, 'We expect that the Dyax libraries will prove to be of great benefit to MedImmune as they continue to broaden and strengthen their antibody pipeline focused on oncology, immunology, and infectious diseases.'

About Dyax Corp.

Dyax Corp. is a biopharmaceutical company principally focused on the discovery, development and commercialization of therapeutics for inflammatory conditions and in oncology. Dyax currently has two recombinant proteins in clinical development, DX-88 and DX-890. DX-88 is being studied in phase II clinical trials for the treatment of hereditary angioedema in collaboration with Genzyme Corporation. Dyax is also studying DX-88 in a phase I/II clinical trial for use during cardiopulmonary bypass surgery. DX-890 is being studied in phase IIa clinical trials for the treatment of cystic fibrosis in collaboration with Debiopharm, S.A. Dyax utilizes its proprietary phage display technology to rapidly identify a broad range of recombinant protein, peptide, and fully human monoclonal antibody compounds that bind with high affinity and specificity to targets of interest, with the objective of selecting those compounds with the greatest potential for advancement into clinical development. Dyax leverages broadly its phage display technology through revenue generating licenses and collaborations in both its core therapeutics area, as well as in non-core areas of affinity separations, diagnostic imaging, and research reagents. Through its subsidiary, Biotage, Inc., Dyax develops, manufactures and sells chromatography separations systems and products to pharmaceutical companies worldwide for drug discovery and purification. For more information on Dyax Corp., please visit its website at www.dyax.com.

About MedImmune, Inc.

MedImmune is a leading biotechnology company focused on researching, developing and commercializing products to prevent or treat infectious disease, autoimmune disease and cancer. MedImmune actively markets four products, Synagis(R) (palivizumab), FluMist(TM) (Influenza Virus Vaccine Live, Intranasal), Ethyol(R) (amifostine) and CytoGam(R) (cytomegalovirus immune globulin intravenous (human)), and has additional products in clinical testing. MedImmune employs approximately 1,700 people, is headquartered in Gaithersburg, Maryland, and has additional operations in Frederick, Maryland, as well as Pennsylvania, California, the United Kingdom and the Netherlands. For more information on the company, visit MedImmune's website at www.medimmune.com.

For Dyax:

This press release contains forward-looking statements, including statements regarding the expected benefits of Dyax's license to MedImmune. Statements that are not historical facts are based on Dyax's current expectations, beliefs, assumptions, estimates, forecasts and projections about the industry and markets in which Dyax competes. The statements contained in this release are not guarantees of future performance and involve certain risks, uncertainties and assumptions, which are difficult to predict. Therefore, actual outcomes and results may differ materially from what is expressed in such forward-looking statements. Important factors which may affect the expected benefits of Dyax's license to MedImmune include the risks that: Dyax's future benefits from its non-exclusive licensing program depend on the efforts and priorities of its licensees, which may be subject to changes in the licensee's business direction or priorities; others may develop technologies or products superior to Dyax's phage display technologies; Dyax may not be able to obtain and maintain intellectual property protection for its products and technologies; and other risk factors described or referred to in Dyax's most recent Annual Report on Form 10-K and other periodic reports filed with the Securities and Exchange Commission. Dyax cautions investors not to place undue reliance on the forward-looking statements contained in this release. These statements speak only as of the date of this release, and Dyax undertakes no obligations to update or revise these statements, except as may be required by law. Dyax specifically disclaims responsibility for information describing MedImmune and its business other than the license with Dyax. Dyax and the Dyax logo are the registered trademarks of Dyax Corp.

SOURCE: Dyax Corp.

Dyax Corp. Jack Morgan, 617-250-5762 This email address is being protected from spambots. You need JavaScript enabled to view it.

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