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Revised: Nov 5, 2001

FOR IMMEDIATE RELEASE

BOTHELL, Wash.--(BUSINESS WIRE)--Nov. 5, 2001--ICOS Corporation (Nasdaq:ICOS) and Afferon Corporation, a privately held firm, today announced the signing of an agreement providing ICOS with exclusive worldwide license rights to RTX(TM) (resiniferatoxin) for the treatment of urological disorders.

Under the terms of the agreement, ICOS would pay Afferon an upfront payment, success-based milestone payments and royalties on any marketed products. ICOS will pay the costs to develop and commercialize RTX and analogues.

RTX is a small molecule that can be delivered to the bladder to desensitize specific nerves called afferent neurons. Afferent neurons are believed to play a role in many pathological conditions of the bladder and urinary tract such as interstitial cystitis, a debilitating condition often associated with severe pain as well as urgency and high frequency of urination.

It is estimated that 500,000 patients in the United States suffer from interstitial cystitis. "Current treatment options are inadequate and there exists a significant unmet patient need," stated Michael Chancellor, M.D., of the University of Pittsburgh. "Recent advances in our understanding of afferent neurons and the ability to desensitize them with the therapeutic agent, RTX, offers a novel approach that is medically promising."

Phase 1 and early Phase 2 clinical studies conducted by Afferon have enrolled patients with interstitial cystitis and overactive bladder. Clinical studies completed to date have demonstrated that RTX is safe and support the continued development of the compound.

"In recent years, there has been an increasing awareness of the serious impact of urological conditions on the lives of patients. ICOS is committed to commercializing novel therapeutic agents that both complement our product portfolio and address serious unmet medical needs," stated Paul Clark, ICOS Chairman and CEO.

"The medical community has done a wonderful job of educating patients to seek treatment for bladder conditions. However, in many cases, including interstitial cystitis and overactive bladder, there are many patients that do not respond well to existing treatments. We are pleased to have ICOS continue the development of RTX," commented Terry Winters, Ph.D., Afferon CEO and member of the board.

ICOS is a product-driven company that has expertise in both protein-based and small molecule therapeutics. The Company combines its capabilities in molecular, cellular and structural biology, high throughput drug screening, medicinal chemistry and gene expression profiling to develop highly innovative products with significant commercial potential. ICOS applies an integrated approach to specific target areas where it has expertise, including erectile dysfunction, sepsis, pulmonary hypertension and other cardiovascular diseases, inflammatory diseases and cancer.

This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. These forward-looking statements involve risks and uncertainties that could cause ICOS' results and the timing of certain events to differ materially from those discussed in the forward-looking statements, including risks associated with clinical development, regulatory approvals, product commercialization, intellectual property claims and litigation and other risks detailed in the Company's latest Annual Report on Form 10-K and its other public filings filed with the Securities and Exchange Commission.

CONTACT: ICOS Corporation
Lacy Fitzpatrick, 425/415-2207