Dyax Corp. Treats First Patient in Phase 2 Trial for On-Pump Cardiothoracic Surgery.

CAMBRIDGE, Mass. -- Dyax Corp. (Nasdaq:DYAX) announced today that patient treatment has begun in the Phase 2 trial of DX-88 (ecallantide) for the prevention of blood loss during on-pump cardiothoracic surgery (CTS), which includes coronary artery bypass graft (CABG) surgery and heart valve replacement or repair procedures. To date, Dyax has successfully completed a Phase 1/2 trial with DX-88 for the prevention of blood loss during CABG surgery. Dyax is also conducting a second Phase 3 clinical trial of DX-88 for the treatment of acute attacks of hereditary angioedema, a rare genetic disease characterized by episodes of acute swelling and inflammation.

The current Phase 2 trial for CTS is a 160-patient, randomized, placebo-controlled trial that will be conducted at ten major U.S. cardiac surgery centers. The trial will compare a low dose or high dose of DX-88 versus placebo and will investigate various endpoints that include: chest tube drainage, transfusion requirements, and pharmacodynamic measurements. DX-88, which was discovered by Dyax, is a recombinant small protein that has shown to be a high affinity, high specificity inhibitor of human plasma kallikrein, a key enzyme in the inflammatory cascade that is thought to play a role in systemic inflammatory response syndrome and blood loss during on-pump CTS procedures.

"The number and complexity of cardiac surgical cases continues to rise and reducing blood loss during these on-pump procedures can be a challenge," said Alina Grigore, M.D., Associate Professor of Anesthesiology at Baylor College of Medicine and anesthesiologist at the Texas Heart Institute in Houston, who treated the first patient in this trial and was assisted by cardiac surgeon Dr. David Ott. "It is important to participate in studies that seek a solution to this problem."

"We are very pleased about achieving this significant milestone in our CTS program," remarked Henry E. Blair, Chairman, President and Chief Executive Officer of Dyax. "There are nearly half a million on-pump surgical procedures taking place in the United States each year. With limited options currently available for preventing blood loss during these procedures, there is clearly a major market opportunity for an alternative treatment. We believe DX-88 has the potential to offer significant therapeutic benefits to physicians and the patients they treat."

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 ongoing. 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. 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, is ongoing.

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, and has 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 the clinical trials and plans for the development of DX-88 for HAE and CTS. 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 clinical trials and plans for the development of DX-88 for HAE and CTS 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 in HAE or CTS; others may develop technologies or products superior to DX-88 in HAE or CTS or that are on the market before DX-88; DX-88 may not gain market acceptance in HAE or CTS; Dyax is dependent on the expertise, effort, priorities and contractual obligations of third parties in the clinical trials and manufacture of DX-88; and Dyax is subject to 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 and the Dyax logo are registered trademarks of Dyax Corp. EDEMA4 is a service mark for Dyax Corp.