In the Phase 2 crossover study, healthy subjects had specific coagulation factors reduced through the use of the anticoagulant, Coumadin. The subjects were then transfused, in random order, with treated FFP and untreated FFP. The study was designed to evaluate recovery of the coagulation factors following transfusion.

The Phase 2 study demonstrated that post-transfusion coagulation factor levels of subjects receiving FFP treated with the company's S-59-based FFP pathogen inactivation system were comparable to those of subjects receiving untreated FFP. There were no safety issues attributable to the treated FFP. The study data will be presented at the American Society of Hematology (ASH) conference in Miami on December 7.

“By artificially depressing the coagulation factors in the healthy subjects, we obtained some insight into the therapeutic efficacy of the FFP treated with our pathogen inactivation system,” said Cerus vice president of medical affairs Laurence Corash, M.D. “The study showed that both the untreated FFP and FFP treated with our process restored the subjects' coagulation factor levels to their normal ranges.”

“Moving the FFP program into a patient study is a significant milestone for Cerus. The Phase 2b trial will be a small study which should provide valuable information as we work to develop a protocol for a Phase 3 study,” said Cerus president and chief executive officer Stephen Isaacs. “This comes on the heels of a recently completed small patient study for our platelet system which was designed for the same purpose.”

At the ASH conference, in addition to the FFP Phase 2 data, the company will be presenting study data from its platelet and red blood cell programs and from a new program the company has initiated relating to bone marrow transplantation.

The Cerus FFP pathogen inactivation system is based on its proprietary light-activated psoralen compound, S-59. This compound has been developed to target and inactivate blood-borne pathogens while leaving the therapeutic properties of FFP intact. An estimated 10 million units of FFP are transfused annually worldwide in surgical settings and to prevent bleeding in a broad range of indications.

The company also is developing pathogen inactivation systems for platelets and red blood cells intended for transfusion. The platelet system, based on the same light-activated S-59 compound, is currently in a European Phase 3 clinical study. The company is developing a protocol for a Phase 3 study in the U.S. The red blood cell system, based on the company's proprietary pH-activated anchor-linker-effector (ALE) compound, S-303, has been cleared by the FDA for Phase 1 clinical trials.

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 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.