ViroPharma and Wyeth Announce Achievement of Proof of Concept Milestone for HCV-796 - Companies Preparing to Initiate Phase 2 Clinical Evaluation

August 14, 2006

ViroPharma Incorporated (Nasdaq: VPHM) and Wyeth (NYSE: WYE) today announced that while the analysis of data from their Phase 1b study of HCV-796, an investigational oral non-nucleoside hepatitis C virus (HCV) polymerase inhibitor, in combination with pegylated interferon, is still ongoing, data analyzed to date indicate that HCV-796 has achieved a "proof of concept" milestone under the companies' agreements. The companies expect that preliminary data from the Phase 1b study will be available for release by the end of August 2006. Based upon the preliminary data reviewed to date, ViroPharma and Wyeth are preparing to initiate Phase 2 combination studies of HCV-796. The companies expect to begin dosing patients in the Phase 2 study in the fourth quarter of 2006.

In connection with meeting the proof of concept milestone, ViroPharma will issue to Wyeth 981,836 shares of ViroPharma's common stock for a purchase price of Ten Million Dollars ($10,000,000), which represents the last of three stock purchases outlined in the companies' agreements. The price per share for the stock was based on a premium to a trailing average price.

"ViroPharma and Wyeth have been partners in hepatitis C antiviral development since 1999; through the years, our goal has been to identify, develop and eventually market drugs to treat hepatitis C patients," said Michel de Rosen, ViroPharma's president and chief executive officer. "HCV-796 is the most promising compound we have developed together to date, and we look forward to announcing the Phase 1b data later this month. The achievement of this milestone and progression toward Phase 2 clinical trials marks an exciting time for us, and a promising opportunity for patients with HCV."

"With HCV-796, we now have for the first time in our collaboration a unique compound with a novel mechanism of action that has achieved proof of concept in combination with pegylated interferon," commented Robert Ruffolo, Ph.D., Wyeth Pharmaceutical's president of research. "We are excited to reach this milestone and to be collaborating with ViroPharma to move this promising compound toward Phase 2 trials."

In December 1999, ViroPharma and Wyeth entered into an alliance to develop and commercialize ViroPharma's lead small molecule antiviral drug candidates for hepatitis C virus (HCV) and to discover, develop and commercialize additional novel inhibitors of HCV. In this agreement, Wyeth agreed to purchase shares of ViroPharma's common stock at the time of completion of certain product development milestones. Under rules promulgated by the Securities and Exchange Commission, ViroPharma is required to publicly file, via Form 8-K, the fact that common stock is being issued in connection with the achievement of the proof of concept milestone.

About HCV-796

HCV-796 is an investigational non-nucleoside polymerase inhibitor compound for the treatment of hepatitis C that is being evaluated in ongoing clinical trials in combination with PEG-Interferon by ViroPharma and Wyeth.

About ViroPharma Incorporated

ViroPharma Incorporated is a biopharmaceutical company dedicated to the development and commercialization of products that address serious diseases treated by physician specialists and in hospital settings. ViroPharma commercializes Vancocin(R), approved for oral administration for treatment of antibiotic-associated pseudomembranous colitis caused by Clostridium difficile and enterocolitis caused by Staphylococcus aureus, including methicillin-resistant strains (for prescribing information, please download the package insert. ViroPharma currently focuses its drug development activities in viral diseases including cytomegalovirus (CMV) and hepatitis C (HCV). For more information on ViroPharma, visit the company's website at http://www.viropharma.com.

About Wyeth

Wyeth is one of the world's largest research-driven pharmaceutical and health care products companies. It is a leader in the discovery, development, manufacturing, and marketing of pharmaceuticals, vaccines, biotechnology products and nonprescription medicines that improve the quality of life for people worldwide. The Company's major divisions include Wyeth Pharmaceuticals, Wyeth Consumer Healthcare and Fort Dodge Animal Health.