Dyax Enters into $50 Million Agreement with Healthcare Royalty Partners

Paul Royalty Interest Repurchased, Resulting in Net Proceeds of Approximately $15 million

Cambridge, MA, August 6, 2008 – Dyax Corp. (NASDAQ: DYAX) announced today that it has entered into a $50 million loan agreement with HealthCare Royalty Partners, L.P. (“HC Royalty”) secured by the Company’s phage display Licensing and Funded Research Program (“LFRP”). The Company used the proceeds from the loan, in part, to repurchase the LFRP revenue interest granted to Paul Capital Partners’ Paul Royalty Fund II, L.P in August 2006, resulting in net proceeds of approximately $15 million, before transaction fees.

The loan, which matures in August 2016, bears interest at an annual rate of 16%, payable quarterly. Dyax may prepay the loan without penalty, in whole or in part, beginning on the third anniversary of the closing date. Dyax retains a substantial interest in the LFRP revenues, including participation in revenues derived from products commercialized by Dyax licensees. The loan agreement does not apply to Dyax’s internal drug development or to any of its co-development programs. Upon repayment of the loan, all rights to the LFRP revenues will revert to Dyax. In connection with the loan, Dyax issued to HC Royalty a warrant to purchase 250,000 shares of the Company’s common stock at a 50% premium over the 30-day average closing price. The warrant has an eight-year term and is exercisable beginning on the one-year anniversary of the closing date.

“This strategic financing agreement reflects the growing value of our proprietary phage display technology and maturing LFRP pipeline,” commented Henry E. Blair, Chairman, President and Chief Executive Officer.  “The net proceeds realized through this financing, together with the larger retained interest in our future LFRP revenues resulting from the repurchase of Paul Royalties’ interest, improve the Company’s cash position in a challenging financial market and support our ongoing efforts to reduce cash burn.”

“This is an exciting and unique investment opportunity for HC Royalty,” commented Gregory B. Brown, M.D., Co-Founder and Managing Director.  “Phage display, a proven and powerful drug discovery tool, has been leveraged broadly through Dyax’s successful Licensing and Funded Research Program.  We believe Dyax is well positioned to capture a substantial share of the growing therapeutic antibody market, which is translating into more valuable LFRP licensing deals, and that the innovative structure of this financing enhances operating flexibility for Dyax while affording attractive investment returns.”

Additional details on the loan agreement can be found in the Current Report on Form 8-K that will be filed by Dyax with the Securities and Exchange Commission on or about the date hereof.

The securities offered in this private placement have not been registered under the Securities Act of 1933, as amended or state securities laws, and cannot be offered or sold in the United States absent registration with the Securities and Exchange Commission or an applicable exemption from the registration requirements.  This press release is neither an offer to sell nor a solicitation of an offer to buy any of the securities discussed herein and shall not constitute an offer, solicitation or sale in any jurisdiction in which such offer, solicitation or sale is unlawful.

About Dyax’s Licensing and Funded Research Program (LFRP)
Dyax provides access to its phage display libraries through various types of collaborations through its LFRP.  In this way, Dyax offers its partners therapeutic discovery capabilities and also extends its reach into non-core areas such as imaging, diagnostics, research reagents and affinity purification.  The LFRP is comprised of a number of top biopharmaceutical companies, including Amgen, Biogen-Idec, ImClone, sanofi-aventis and Wyeth, among others.  To date, Dyax has LFRP agreements with more than 70 licensees and collaborators, resulting in thirteen clinical-stage product candidates and one approved product.

About Dyax
Dyax is focused on advancing novel biotherapeutics for unmet medical needs, with an emphasis in oncology and inflammation.  Dyax utilizes its proprietary drug discovery technology, phage display, to identify antibody, small protein and peptide compounds.  Dyax, on its own or with its partners, has advanced several product candidates from discovery and lead validation into preclinical and clinical development.  The Company’s lead product candidate, DX-88, is a recombinant small protein that is being developed by Dyax for its therapeutic potential for treating hereditary angioedema (HAE).  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 HAE attacks.  In April 2008, Dyax licensed to Cubist Pharmaceuticals the intravenous formulation of DX-88 for surgical indications in North America and Europe.  In addition to using phage display for its internal pipeline, Dyax leverages this technology broadly into revenue generating licenses and collaborations through its Licensing and Funded Research Program (LFRP). Dyax is headquartered in Cambridge, Massachusetts.  For more information about Dyax Corp., please visit www.dyax.com.

About HealthCare Royalty Partners
HealthCare Royalty Partners is a healthcare private equity firm with over $500 million under management. The firm invests principally in commercial-stage biopharmaceutical and medical device companies through the purchase of royalty and Synthetic Royalty(R) interests, debt and equity. HC Royalty’s investment team has over 100 years of healthcare related experience including principal investing, structured finance, healthcare industry senior management, Wall Street research and consulting, scientific and clinical experience. For more information visit www.healthcareroyalty.com.

Dyax Disclaimer
This press release contains forward-looking statements, including statements regarding Dyax’s phage display licensing and funded research program (LFRP), the LFRP’s potential to generate future revenues and the potential for Dyax’s licensees to bring products to market.  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 that may affect the extent of Dyax’s patent portfolio and its potential for the identification of novel compounds include the risks that:  Dyax may not be able to obtain and maintain intellectual property protection for its phage display technology; others may develop technologies superior to Dyax’s phage display technology; and other risks that are 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.