Dyax and Genzyme Reaffirm Positive Market Outlook for DX-88 for the Treatment of Hereditary Angioedema; Conference Call Scheduled for 10 am Today

Business Wire, July 19, 2004

CAMBRIDGE, Mass. -- Dyax Corp. (Nasdaq:DYAX) announced that it will host a conference call at 10 am EST today, to expand upon statements made with regard to the market demand for DX-88 for the treatment of hereditary angioedema (HAE) during Genzyme Corporation's July 14 second quarter earnings call. DX-88 is a recombinant protein discovered by Dyax that is in Phase II clinical development in a joint venture with Genzyme.

On hand to address questions related to market demand will be Henry E. Blair, Chairman, President and CEO of Dyax; Anthony H. Williams, MD, FRCP, Senior Vice President of Medical Affairs and Clinical Operations at Dyax; Richard Moscicki, MD, Chief Medical Officer and Senior Vice President at Genzyme; and Paul Merrigan, Vice President, Global Marketing at Genzyme.

Topics open for discussion will be:

--Prevalence of HAE: Based on published data and ongoing market research, Dyax and Genzyme reiterate their estimate that the prevalence of HAE is between 1:10,000 and 1:50,000. Extrapolating from these data, the companies estimate that there are between 13,000 and 66,000 patients with HAE in the United States and Europe.

--Number of attacks: Dyax and Genzyme reiterate past guidance indicating that patients experience an average of 12 attacks per year. In patients with more severe HAE, chronic treatment with anabolic steroids can reduce the number of attacks, but recent interactions with physicians who treat HAE confirm the unsuitability and substantial risks of chronic steroid use, and the strong demand for a non-steroidal alternative. Patients themselves report a higher frequency of attacks. A recent unpublished survey conducted by the U.S. HAE Patient Association involving over 150 patients who manage their HAE with steroids indicates that, even with steroid use, their average number of attacks per year is substantially higher than 12.

--HAE Patient Identification: Pre-launch preparation has led to the identification of 3,000 - 5,000 HAE patients in the United States alone to whom DX-88 would be immediately accessible upon potential launch of the product. This range is derived from the number of patients associated with or in routine communications with the U.S. HAE Patient Association. Early experience with these patients indicates that in most cases, each represents a multiple of patients in his or her family who are also diagnosed with HAE. Excluded from these figures are patients who are unaffiliated with HAE associations in the U.S., and patients in Europe.

"We are particularly pleased with the sizable number of patients immediately accessible upon potential launch of DX-88," stated Paul Merrigan. "To have this large number of patients identified at this stage of development puts us in a strong position for the potential launch of the product."

Henry E. Blair, Chairman, President and CEO of Dyax commented, "My colleagues from Genzyme and I look forward to discussing in greater depth our long-standing guidance related to the demand for a benign and effective treatment for the debilitating and life-threatening symptoms of HAE. Our findings to date reinforce our guidance related to the size of the patient population, and the demand for a better treatment."

The joint development program for DX-88 in HAE is believed to represent the only active clinical trial program for HAE in the United States, where there is no approved treatment for this debilitating and life-threatening acute inflammatory disease.

Conference call details:

Date:              Monday, July 19, 2004
Time:              10:00 a.m. EST
Telephone Access:  Domestic callers, dial 1-800-888-5452
                   International callers, dial 1-719-867-0660
Online Access:     Go to the Investor Relations section of the Dyax
                   website (www.dyax.com) and follow instructions for
                   live webcast. Participants may register in advance.

A replay of the conference call will be available through August 2, 2004 and can be accessed by dialing 1-888-203-1112. International callers should dial 719-457-0820. The replay passcode I.D. for all callers will be 368516. The webcast will be archived on Dyax's website for an indefinite period of time.

About Dyax Corp.

Dyax Corp. is a biopharmaceutical company focused on the discovery, development and commercialization of antibodies, small proteins and peptides as therapeutic products for unmet medical needs, particularly in the areas of inflammation and oncology. Two recombinant small proteins discovered by Dyax are currently in phase II clinical trials. In collaboration with Genzyme Corporation, DX-88 is in phase II trials for the potential treatment of hereditary angioedema (HAE). Dyax has also completed phase I/II trials for the potential use of DX-88 during open-heart surgery, specifically on-pump coronary artery bypass grafting (CABG) procedures. Our collaborator for DX-890, Debiopharm SA, has completed phase IIa clinical trials for the potential treatment of cystic fibrosis.

Both DX-88 and DX-890 were identified using Dyax's patented phage display technology, which rapidly selects compounds that bind with high affinity and specificity to therapeutic targets. This powerful discovery engine is being used to build a pipeline of drug candidates that may be advanced into clinical development by Dyax and/or in partnership with other companies. Dyax leverages its technology broadly with over 75 revenue-generating licenses and collaborations for therapeutic discovery, as well as in non-core areas such as affinity separations, diagnostic imaging, and research reagents. For online information about Dyax Corp., please visit www.dyax.com.