Dyax Announces Positive Final Results from Phase I Trial of Subcutaneous DX-88; Positive Experience with Subcutaneously Administered DX-88 in the Ongoing, Phase II Open-Label EDEMA2 Trial for Hereditary Angioedema.

CAMBRIDGE, Mass. -- Dyax Corp. (Nasdaq:DYAX) today announced that positive final data from its completed Phase I trial, demonstrating that DX-88 was safe and well tolerated in normal volunteers when administered subcutaneously, were presented by Dr. Thomas R. Beck, Executive Vice President, Business and Product Development of Dyax, at the American Asthma, Allergy and Immunology Conference (ACAAI) in Anaheim, CA. Dr. Beck also reported positive initial experience in 31 attacks treated subcutaneously with DX-88 in the ongoing, Phase II open-label EDEMA2 study. DX-88 is being developed in a joint venture with Genzyme Corporation for the treatment of hereditary angioedema (HAE), a debilitating and life-threatening inflammatory condition characterized by unpredictable attacks of severe peripheral, abdominal and/or laryngeal pain and swelling.

Based on the pharmacokinetic and safety profiles observed in the Phase I trial, Dyax has now converted all clinical sites in the ongoing EDEMA2 trial from intravenous (IV) dosing to the more easily administered subcutaneous (SQ) injection of DX-88. This conversion has provided HAE patient experience with SQ DX-88 prior to the initiation of a pivotal Phase III trial planned to start before year end. Recently, Dyax has sent the Phase III protocol to 47 U.S. and Canadian sites. Dyax expects the IRB approval process to go smoothly and already has sites with identified patients, awaiting enrollment. Dyax, together with Genzyme, remains committed to bringing DX-88 to the marketplace as the first subcutaneously administered treatment for the HAE patient community.

Phase I Final Results

The Phase I study, performed in 18 normal volunteers, was designed to compare bioavailability of IV versus SQ routes of administration. Three dose regimens of DX-88 were compared: IV infusion of 30 mg, SQ injection of 30 mg and SQ injection of 10 mg. As expected, the SQ route of administration led to a reduced maximal concentration (3741 ng/ml versus 586 ng/ml) and a slower time to maximal plasma concentration (2.7 hours versus 0.17 hours) compared to IV administration. When DX-88 was delivered SQ, it was highly bioavailable at 91%. In addition, the duration of time above the theoretical pharmacologically active concentration was doubled with SQ relative to IV infusion. Other pharmacokinetic parameters were comparable for both routes of administration. DX-88 was well tolerated as a 30 mg (IV or SQ) dose. The overall safety profile was favorable for the SQ route of administration and no significant site reactions were observed. There were no reported serious adverse events.

EDEMA2 Interim Subcutaneous Results

EDEMA2 is a dose-ranging, open-label, repeat dosing study designed to evaluate the safety and clinical effect of DX-88 when administered multiple times to individual patients for separate HAE attacks. Clinical results are analyzed after every 60 attacks treated in this ongoing trial.

With respect to preliminary SQ experience in the treatment of acute attacks of HAE, the SQ data continues to expand. To date, 31 attacks have been treated with SQ administration in 19 patients, with six patients treated more than once. All types of attacks have been treated: laryngeal (n=4), abdominal (n=19), and peripheral (n=8). The 19 patients include 8 naive patients to DX-88 and 11 patients who previously received IV DX-88. In patients with prior IV experience, the subcutaneous response has been comparable in terms of time to response and magnitude of clinical effect. All patients responded to the treatment. Only one patient had a mild/moderate short duration hypersensitivity response, which did not affect the clinical response to DX-88. The time to onset of clinical improvement (approximately 30 minutes) was the same in the SQ patient experience as it has been in the overall IV EDEMA2 experience to date.

Dr. Thomas Beck stated, "We continue to be extremely encouraged by the data from the subcutaneous route of administration. The conversion to a 30 mg fixed subcutaneous dose in our ongoing, open-label EDEMA2 trial is preparing us well for our pivotal Phase III trial (EDEMA3). Now that the protocol has been sent out to the 47 North American sites, we expect rapid enrollment of patients into the EDEMA3 trial. Across all of our HAE trials, we have treated a total of 295 HAE attacks in 107 patients, an extensive clinical experience in this rare genetic disease. These data continue to support DX-88 as an important therapeutic option of choice for patients with this debilitating disease."

About Dyax

Dyax Corp. 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.

DX-88 is 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 two Phase II trials of DX-88 for the treatment of hereditary angioedema (HAE). A third Phase II trial is ongoing, and a pivotal Phase III trial is planned before year end. Independently, Dyax has successfully completed a Phase I/II trial of DX-88 for the prevention of blood loss during heart surgery (CABG procedures) and is in partnering discussions for further development of DX-88 in this indication. A second Dyax compound, DX-890, is being developed by Debiopharm S.A., which has completed two Phase IIa trials and is now conducting a Phase IIb trial of DX-890 in Europe for the treatment of cystic fibrosis. Both compounds have orphan drug designation in the US and EU, and DX-88 also has Fast Track designation in the US for the treatment of HAE.

Dyax identified DX-88 and other compounds in its pipeline using Dyax's patented phage display technology, which rapidly selects compounds that bind with high affinity and specificity to therapeutic targets. 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.

Dyax Disclaimer

This press release contains forward-looking statements, including statements regarding the potential administration, dosing and therapeutic benefit of DX-88 for HAE, the planned timetable and enrollment for clinical trials of DX-88, and the requirements and plans for regulatory filings and approvals for DX-88 and its position versus other products in development 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, the planned timetable and enrollment for clinical trials of DX-88, the requirements and plans for regulatory filings and approvals for DX-88 and its position versus other products in development 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 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 the registered trademarks of Dyax Corp. EDEMA0, EDEMA1, EDEMA2 and EDEMA3 are trademarks of Dyax Corp.