ViroPharma Announces Lead Compound Series with Potent Antiviral Activity Against Orthopoxviruses

Advancement Toward Development of Smallpox Antiviral Drug

Exton, Pennsylvania, UNITED STATES

EXTON, Pa., July 7, 2003 (PRIMEZONE) -- VIROPHARMA INCORPORATED (Nasdaq:VPHM) today announced that its scientists have discovered a lead compound series from VIROPHARMA's unique chemical library that shows potent and specific antiviral activity against orthopoxviruses, including monkeypox virus, at concentrations that have no adverse effects on normal cells in culture. Moreover, compounds in the series have been shown to be orally bioavailable in animal studies. VIROPHARMA is collaborating in this effort with the U.S. Army Medical Research Institute of Infectious Diseases (USAMRIID) in Frederick, Maryland. USAMRIID has confirmed the activity of the VIROPHARMA compounds against a range of orthopoxviruses and expects to determine, within the next few weeks, the activity of the compounds against the deadly variola (smallpox) virus in tests to be conducted at the Centers for Disease Control and Prevention (CDC) in Atlanta. Orthopoxviruses are a group of closely related viruses that include vaccinia, cowpox, monkeypox, camelpox and variola (smallpox) viruses.

VIROPHARMA, together with USAMRIID, will further optimize these early stage compounds and conduct studies to evaluate the efficacy of the most promising drug candidates in animal models of orthopoxvirus disease in the coming months. Details of the virological and pharmacological attributes of these compounds will be presented at an upcoming scientific conference.

"Smallpox is one of the most serious bioterrorism threats we face. Our country's current ability to deal with a terrorist attack with this pathogen is unsettling," said Marc Collett, Ph.D., vice-president of Discovery Research at VIROPHARMA. "The U.S. government has expressed the urgent need for effective countermeasures to the smallpox threat. We have discovered an exciting chemical series that, if we establish its activity against the variola virus, will form the basis of an aggressive lead optimization program. VIROPHARMA and USAMRIID will work expeditiously to advance this program into animal efficacy and human safety studies with lead antiviral drug candidates."

Currently, there is no FDA-approved antiviral drug specifically for use in the event of a bioterrorist attack involving smallpox virus.

VIROPHARMA's smallpox program is part of a broader company effort in the area of bioterrorism and emerging virus disease threats. In late 2002, VIROPHARMA initiated a program to discover and advance potential antiviral product candidates that address National Institutes of Health "Category A virus" disease threats, including smallpox and viral hemorrhagic fevers (Ebola, Lassa and Rift Valley fever) and emerging virus diseases. Recently, VIROPHARMA, in collaboration with USAMRIID, began evaluating compounds from its more than 400,000-compound library for antiviral candidates against the virus that causes severe acute respiratory syndrome (SARS). VIROPHARMA has applied for government funding to help defray the costs of advancing certain of these projects, and expects to be notified in mid-2003 regarding awards for this round of funding.


Smallpox is a highly contagious, often fatal disease caused by variola (smallpox) virus. About 30% of those infected with the smallpox virus die. Smallpox outbreaks had occurred periodically for thousands of years. However, the disease was eradicated from the globe more than two decades ago after a successful worldwide vaccination campaign. The last case of smallpox in the United States was in 1949 and in the world in 1977. Routine vaccination against smallpox was stopped in the United States in 1972 and in the rest of the world in 1980. Scientists have retained stocks of the variola virus for research purposes in two secure laboratories, one at the CDC in Atlanta, Georgia, and the other in Moscow, Russia. However, in light of terrorist activities in recent years, there is global concern that stores of unaccounted smallpox virus could be used for bioterrorism. The CDC has classified smallpox as the highest priority (Category A) bioterrorism threat to the U.S. public health system and national security due to the fact that variola virus can be easily disseminated and transmitted from person to person, has the potential to cause widespread illness and death, and requires special actions for public health preparedness. There is currently no specific treatment for smallpox disease, and the only prevention is vaccination.


VIROPHARMA INCORPORATED is committed to the commercialization, development and discovery of antiviral pharmaceuticals. VIROPHARMA, in addition to its biodefense and emerging diseases initiatives, is currently focused on drug development and discovery activities in hepatitis C, and is pursuing clinical development activities to treat diseases caused by picornavirus infections. The company's most advanced hepatitis C antiviral compound is in human clinical trials, and the company is considering the development of Picovir(r) to treat patients suffering from severe or life-threatening enteroviral infections.

About U.S. Army Medical Research Institute of Infectious Diseases

USAMRIID conducts basic and applied research on biological threats resulting in medical solutions to protect the warfighter. As the Department of Defense's lead laboratory for medical aspects of biological warfare defense, USAMRIID collaborates with the CDC, the National Institutes of Health, the World Health Organization (WHO), the Department of Energy, the Federal Bureau of Investigation, and academic centers of excellence worldwide. USAMRIID also serves as a reference laboratory for the CDC and the WHO.

The information contained in this press release does not necessarily reflect the position or the policy of the Government and no official endorsement should be inferred.

This press release contains forward-looking statements. These include the Company's expectation to receive data from USAMRIID within the next few weeks to determine the activity of certain compounds against the smallpox (variola) virus, and the Company's plans to continue to work with the government to assist in the discovery and development of a treatment for smallpox, to advance the smallpox effort into animal efficacy studies, and to discover and advance other potential antiviral product candidates in a biodefense and emerging diseases initiative, as well as the Company's expectation that it will be notified in mid-June as to whether it will receive funding from the government to help defray the costs of advancing certain of these projects. The Company's efforts in biodefense (including smallpox) and emerging diseases are discovery stage programs, and as such are subject to risks and uncertainties. The discovery of active compounds, advancing promising active compounds through preclinical development and clinical development, and pursuing regulatory approval of product candidates that appear to demonstrate the requisite safety and efficacy, requires considerable time and expense. There can be no assurance that VIROPHARMA's efforts in biodefense (including smallpox) and emerging diseases will yield positive results, will result in effective treatments in a timely manner, if at all, or that the FDA would approve any such smallpox or other biodefense or emerging disease product candidate. These factors, and other factors, including, but not limited to those described in VIROPHARMA's most recent annual report on Form 10-K filed with the Securities and Exchange Commission, could cause future results to differ materially from the expectations expressed in this press release. The forward-looking statements contained in this press release may become outdated over time. VIROPHARMA does not assume any responsibility for updating any forward-looking statements.