Positive Final Results from EDEMA2 Trial with DX-88 for the Treatment of Hereditary Angioedema Presented at ACAAI Meeting.

CAMBRIDGE, Mass. -- Dyax Corp. (Nasdaq:DYAX) announced that two oral abstracts were presented yesterday highlighting collective results from the Company's Phase II trials of DX-88 (ecallantide), including its most recent results from its EDEMA2 trial, for the treatment of acute attacks in hereditary angioedema (HAE). The abstracts were presented at the American College of Allergy, Asthma & Immunology 2007 Annual Meeting being held in Philadelphia, PA from November 9 through November 15, 2006. The presentations were made on November 13 by the following DX-88 investigators: Dr. William Lumry, M.D., AARA Research Center, Dallas, TX, and Dr. H. Henry Li, M.D., Ph.D., FACAAI, Institute for Asthma and Allergy, Wheaton, MD. The presentations featured overall positive results from three completed Phase II trials highlighting final results from the Phase II, EDEMA2 trial. DX-88 is being developed in a joint venture with Genzyme Corporation for the treatment of HAE, a debilitating and potentially life-threatening inflammatory condition characterized by unpredictable attacks of severe peripheral, abdominal and/or laryngeal pain and swelling.

Dr. William Lumry, M.D. presented on the topic of "Results of a Repeat-Dosing Study of Intravenous and Subcutaneous Administrations of Ecallantide (DX-88), a Recombinant Plasma Kallikrein Inhibitor, in Patients with Hereditary Angioedema", and Dr. H. Henry Li, M.D., Ph.D. presented on the topic of "Dose Response in Intravenous and Subcutaneous Administration of Ecallantide (DX-88), a Potent Inhibitor of Human Plasma Kallikrein, in Patients with Hereditary Angioedema."

The presentations included final results from the EDEMA2 study on 240 HAE attacks in 77 patients using both intravenous (IV) and subcutaneous (SC) routes of administration. The presentations by Dr. Lumry and Dr. Li reported that the data showed the following:

* Clinical response at or before 4 hours for all dose levels, with 92% response at 5 mg/m2 (IV), 85% response at 10 mg/m2 (IV), 87% response at 20 mg/m2(IV), and 92% response at 30 mg flat dose (SC).

* Rapid onset of response was consistent across all dose levels, and median time to response was 29 minutes, which is comparable to the shortest time historically reported for the response times with C1 inhibitors.

* The 30 mg SC dose had a median time to significant improvement of 63 minutes and greatest maintenance of response (no relapse or rebound through 24 hours following treatment) at 80% compared to 46% at 5 mg/m2, 68% at 10 mg/m2, and 60% at 20 mg/m2.

* Response rates were comparable for all attack locations.

* DX-88 was well tolerated at all dose levels, with no increase in severity or frequency of adverse events with multiple doses.

* The majority of adverse events were mild or moderate in severity.

* DX-88 demonstrated substantial therapeutic benefit with rapid onset of action and good tolerability in patients with recurrent, acute HAE attacks.

* DX-88 as a 30 mg SC dose showed comparable safety to the IV dose regimens.

* The 30 mg SC was compared to a combined IV dose group with an average dose level of 22 mg and showed superior response times for both beginning of improvement (26 minutes vs. 30 minutes) and significant improvement (63 minutes vs. 114 minutes) and improved maintenance of response.

Dr. Thomas R. Beck, President and Chief Operating Officer of Dyax Corp., remarked, "I would like to recognize Drs. Lumry and Li for the time and effort they are devoting to the DX-88 HAE program. We are very pleased with the results that were presented yesterday. Dyax and our partner Genzyme remain fully committed to advancing an effective treatment for HAE patients who are suffering from the debilitating effects of this unpredictable condition. With our supportive network of HAE patients and physicians, we are developing a treatment that will ultimately give these patients a better quality of life."

About Dyax

Dyax is focused on advancing novel biotherapeutics for unmet medical needs, with an emphasis on cancer 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, or ecallantide, a recombinant small protein that is currently in clinical trials for its therapeutic potential in two separate indications. In its joint venture with Genzyme Corporation, Dyax has successfully completed three Phase II trials of DX-88 for the treatment of hereditary angioedema (HAE). A Phase III trial is ongoing. Independently, Dyax has successfully completed a Phase I/II trial of DX-88 for the prevention of blood loss during on-pump cardiothoracic surgery (CTS), including CABG procedures, and is planning a Phase IIb trial for further development of DX-88 in this indication. DX-88 has orphan drug designation in the U.S. and E.U. for the treatment of angioedema.

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 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 the potential administration, dosing and therapeutic benefit of DX-88 for HAE include the following risks: 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 risks described or referred to in Item 1A, "Risk Factors" in Dyax's most recent Annual Report on Form 10-K and other periodic reports subsequently 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 the registered trademarks of Dyax Corp. EDEMA2 is a service mark of Dyax Corp.