DX-88 for Hereditary Angioedema Meets Primary and Secondary Endpoints in Phase 3 Trial (EDEMA3(R)).

Dyax Corp. to Discuss Results in Webcast Presentation with Investigators

CAMBRIDGE, Mass. -- Dyax Corp. (Nasdaq:DYAX) announced today positive topline results from its Phase 3, placebo-controlled trial, EDEMA3, for its lead product candidate DX-88 (ecallantide), for hereditary angioedema (HAE). A webcast presentation of the EDEMA3 data is scheduled for Tuesday, April 17, 2007 at 12:30 p.m. ET.

DX-88, an internally discovered, recombinant, plasma kallikrein inhibitor, is in clinical trials for the treatment of acute attacks of HAE, a rare genetic disease characterized by episodes of acute swelling and inflammation. Statistically significant results (DX-88-treated patients versus placebo) were achieved for both the primary and secondary endpoints in the EDEMA3 trial.

The primary endpoint, symptom improvement at four hours measured by a Treatment Outcome Score (TOS) developed for HAE attacks, had a p-value of 0.021. The two secondary endpoints also demonstrated statistical significance. The patient reported assessment of individual symptom burden at four hours measured using the Mean Symptom Complex Severity score (MSCS) had a p-value of 0.024. Time to significant improvement in overall response (defined for this trial as the first time post dosing that the patient reported the symptom complex as "a lot better" or "resolved" within the first 4 hours) had a median time of 149 minutes for the DX-88 group versus greater than 4 hours for the placebo group (p=0.044). The overall safety results showed that DX-88 continues to be well tolerated. There were no drug-related serious adverse events. EDEMA3 is the largest successfully completed, placebo-controlled trial for this indication under a United States Investigational New Drug application.

"We are extremely excited about the outcome of this EDEMA3 trial," commented Henry E. Blair, Chairman and Chief Executive Officer of Dyax. "Based on the topline results of this study, the extensive clinical data collected to date, and the pending completion of the EDEMA4 confirmatory trial already underway, we believe we will be well positioned to apply for regulatory approval to bring to market this much needed therapy for the HAE patient community. The results, which will be presented next week in more detail, highlight the potential of DX-88 to be a safe and efficacious therapy. Ultimately, we believe DX-88 will greatly improve the quality of life of HAE patients worldwide."

EDEMA3 Trial

EDEMA3, the 72-patient, placebo-controlled, multi-center, Phase 3 trial, was conducted at 34 sites in the United States, Europe, Canada, and Israel. The primary objective of EDEMA3 was to determine the efficacy and safety of the fixed 30 mg subcutaneous (SC) dose of DX-88 for patients suffering from moderate to severe acute HAE attacks. The trial had two phases: a double-blind, placebo-controlled phase and a repeat dosing phase. In the first phase, HAE patients received either a single 30 mg SC dose of DX-88 or placebo. After patients received one treatment in the placebo-controlled portion of the study, they were eligible for the second, open-label phase of the study, where they receive repeat dosing with SC DX-88 for any subsequent attacks.

Webcast Presentation Details

Dyax Corp. will host a webcast presentation on Tuesday, April 17, 2007, which will include a discussion of the EDEMA3 results and the patient reported outcome methodology in more detail. Henry E. Blair, Chairman and CEO of Dyax, will be joined by senior management and clinical trial investigators from the EDEMA3 trial.

Date: Tuesday, April 17, 2007

Time: 12:30 p.m. ET

Online Access: Go to the Investor Relations section of the Dyax website (www.dyax.com) and follow instructions for accessing the live webcast. Participants may register in advance.

Telephone Access: Domestic callers, dial 1-888-396-2384

International callers, dial 617-847-8711

Passcode 60760258

A replay of the webcast will be available through May 17, 2007 and may be accessed by dialing 1-888-286-8010. International callers should dial 617-801-6888. The replay passcode for all callers is 25344900. The webcast will be archived on the Dyax website for an indefinite period of time.

About Dyax

Dyax is focused on advancing novel biotherapeutics for unmet medical needs, with an emphasis on oncology and inflammatory indications. Dyax utilizes its proprietary drug discovery technology to identify antibody, small protein and peptide compounds for clinical development.

Dyax's lead product candidate is DX-88, a recombinant small protein that is currently in clinical trials for its therapeutic potential in two separate indications. Dyax has successfully completed three Phase 2 trials and a Phase 3 trial of DX-88 for the treatment of hereditary angioedema (HAE). A confirmatory study, known as EDEMA4, is planned and expected to begin in the first quarter of 2007. DX-88 has orphan drug designation in the U.S. and E.U., as well as Fast Track designation in the U.S. for the treatment of acute attacks of HAE.

Additionally, Dyax has successfully completed a Phase 1/2 trial of DX-88 for the prevention of blood loss during on-pump coronary artery bypass graft (CABG) procedures. Dyax is initiating a Phase 2 trial for further development of DX-88 in on-pump cardiothoracic surgery (CTS), including CABG and heart valve replacement or repair procedures.

Dyax identified DX-88 and other compounds in its pipeline using its patented phage display technology, which rapidly selects compounds that bind with high affinity and specificity to therapeutic targets. Dyax leverages this technology broadly with over 70 revenue-generating licenses and collaborations for therapeutic discovery, as well as in non-core areas such as affinity separations, diagnostic imaging, and research reagents.

Dyax is headquartered in Cambridge, Massachusetts, with antibody discovery facilities in Liege, Belgium. For online information about Dyax Corp., please visit www.dyax.com.

Dyax Disclaimer

This press release contains forward-looking statements, including statements regarding clinical trials, the potential administration, dosing, safety and therapeutic benefit of DX-88 for HAE. 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 clinical trials, the potential administration, dosing and therapeutic benefit of DX-88 for HAE, include the risks that: DX-88 may not show sufficient therapeutic effect or an acceptable safety profile in clinical trials or could take a significantly longer time to gain regulatory approval than Dyax expects or may never gain approval; others may develop technologies or products superior to DX-88 or that are on the market before DX-88; DX-88 may not gain market acceptance; Dyax is dependent on the expertise, effort, priorities and contractual obligations of third parties in the clinical trials, manufacture, marketing, sales and distribution of DX-88; and other risk factors described or referred to Item 1A, "Risk Factors" 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.

EDEMA3, Dyax and the Dyax logo are registered trademarks of Dyax Corp. EDEMA4 is a service mark for Dyax Corp.