“This was a significant study that demonstrated the ability of our platelet system to inactivate some very important blood-borne viruses and we are very pleased with the outcome,” said Cerus president and chief executive officer Stephen Isaacs. “These data are supported by scores of successful in vitro studies demonstrating the inactivation of hepatitis viruses as well as a broad spectrum of other known blood-borne pathogens including HIV.”

An estimated 300,000 people in the United States were infected with HCV through blood transfusions prior to mid-1992, at which time a reliable screening test was developed. Although the risk of transmission of HCV through blood transfusion has been greatly reduced, this year the Department of Health and Human Services has initiated a program to notify people who received blood transfusions prior to 1992 that they should be tested for the disease, which can lay dormant for up to 20 years. The disease, which afflicts approximately 3.9 million Americans and 170 million people worldwide, can cause severe liver damage and is the leading reason for liver transplantation. Hepatitis B, which also affects the liver, is one of the world's most common infectious diseases, and afflicts approximately 350 million people worldwide.

The Cerus platelet system is based on the company's proprietary light-activated psoralen compound, S-59. This compound has been developed to target and inactivate blood-borne pathogens, such as HBV and HCV, while leaving the therapeutic properties of platelets intact. An estimated 3.5 million units of platelets are transfused annually worldwide to prevent bleeding in a broad range of patients, including those undergoing cancer therapy and surgical procedures. The company commenced a European Phase 3 study of its platelet system earlier this year and is developing a protocol for a Phase 3 study in the U.S.

The company also is developing pathogen inactivation systems for fresh frozen plasma (FFP) and for red blood cells. The FFP system is based on the same light-activated compound, S-59, and has received clearance to proceed into a Phase 2b patient study. The red blood cell system, based on its proprietary pH-activated anchor-linker-effector (ALE) compound, S-303, is in a Phase 1a clinical trial in healthy subjects.

Cerus Corporation is developing systems designed to enhance the safety of blood transfusions by inactivating pathogens in blood components (platelets, plasma and red blood cells used for transfusion) and by inactivating white blood cells, which are responsible for a variety of adverse transfusion reactions. The company's platform technologies, which prevent viral, bacterial and cellular replication, may have potential applications in the health care field beyond pathogen inactivation in blood components.

Cerus Corporation is collaborating with the Fenwal Division of Baxter Healthcare Corporation to develop, manufacture and market pathogen inactivation systems for blood components used for transfusion. Baxter, a global medical products and services company, focuses on critical therapies for life-threatening conditions. Baxter is a leader in technologies related to blood and the circulatory system. The Fenwal Division develops, manufactures and markets products and services for the collection, separation, storage and transfusion of blood and its components.

This news release contains forward-looking statements that involve risks and uncertainties. Actual results could differ materially from the above forward-looking statements as a result of certain factors, including the uncertainty of the timing and results of any trials, regulation by the FDA, the uncertainty of replication of animal data in humans, the uncertainty of market acceptance of any products, competitive conditions, the uncertainty of future financing and other factors discussed in the company's 1997 Annual Report on Form 10-K.