Company to Present Preclinical Data at the American Society

Of Hematology Meeting

MIAMI, Dec. 7 /PRNewswire/ -- Cerus Corporation (Nasdaq: CERS) announced today that it has commenced a Phase 1a clinical trial of its red blood cell pathogen inactivation system. The trial is a randomized, controlled study designed to evaluate the post-transfusion viability of red blood cells treated with the company's system and includes approximately 40 healthy subjects. The study subjects are receiving a transfusion of either standard red blood cells or red blood cells treated with the company's pathogen inactivation system. The level of circulating transfused red blood cells is measured and compared with established standard of care values for red blood cell recovery twenty-four hours after each transfusion.

The company's pathogen inactivation systems for transfusion blood products (platelets, plasma and red blood cells) are designed to target and inactivate blood-borne pathogens while leaving the products' therapeutic properties intact. The company's red blood cell system is based on its proprietary pH-activated anchor-linker-effector (ALE) compound, S-303, which irreversibly prevents replication of blood-borne pathogens' DNA.

Preclinical data included in the company's Investigational New Drug (IND) application will be presented today at the American Society of Hematology (ASH) conference. Data to be presented from in vitro studies demonstrate ability of the company's red blood cell treatment system to inactivate HIV and hepatitis B and C model viruses below the limit of detection. In addition, data to be presented from an animal model study demonstrate post-transfusion viability and safety of treated red blood cells transfused in single and multiple doses. Together, the data show that treating red blood cells with S-303 offers the potential for robust viral and bacterial inactivation while preserving the viability of red blood cells without toxicity from single or multiple doses.

"Beginning clinical trials with our red blood cell system is a major achievement for the company," said Cerus president and chief executive officer Stephen Isaacs. "Our proprietary S-303 ALE technology is the first system for the pathogen inactivation of red blood cells to enter clinical trials. Pathogen inactivation of red blood cells represents a tremendous opportunity as red blood cells are by far the most commonly transfused blood product."

The Cerus red blood cell system has been developed to target and inactivate blood-borne pathogens while leaving the therapeutic properties of red blood cells intact. An estimated 31 million units of red blood cells are transfused worldwide each year in surgical settings and to treat various indications ranging from severe trauma to genetic disorders.

The company's pathogen inactivation systems for platelets and plasma are based on the proprietary light-activated compound, S-59. The platelet system is currently in a European Phase 3 clinical study and the company is developing a protocol for a Phase 3 study in the U.S. The FFP system has received clearance to proceed into a Phase 2b patient study.

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.