Company is in discussions with the FDA regarding Phase 3 study design

CONCORD, Calif., Nov. 19 /PRNewswire/ -- Cerus Corporation (Nasdaq: CERS) announced today that the Food and Drug Administration (FDA) has concurred that the company may proceed into a Phase 3 clinical trial of its platelet pathogen inactivation system after reviewing the results of the company's Phase 2c template bleeding time study in patients. The company's pathogen inactivation systems are designed to target and inactivate blood-borne pathogens while leaving the therapeutic properties of transfusion blood products intact. Cerus is the first company to reach this stage of development of a pathogen inactivation system for platelets.

The Phase 2c study indicated that platelets treated with the company's S-59-based platelet pathogen inactivation system were therapeutically acceptable when compared to untreated platelets and there were no safety issues attributable to the treated platelets, which were administered to an acutely ill patient population. In the crossover study, thrombocytopenic (platelet-deficient) patients were transfused, in random order, with treated platelets and untreated platelets. The study was designed to evaluate platelet blood clotting function, the increase in platelet count and the time between required platelet transfusions.

"We have been very focused on the clinical progress of our platelet system," said Cerus President and Chief Executive Officer Stephen Isaacs. "We are very pleased that the Phase 2c study data support our effort to move into a Phase 3 trial. As this is the first product of its kind to reach this stage of development, we are working closely with the FDA to develop a protocol for a study of appropriate scope that is sufficiently sized to produce a statistically significant result."

"In this study, we examined a variety of clinical and laboratory parameters relating to platelet function and the safety of our system including a very difficult bleeding time measurement. The study was designed to provide clinical data in patients in preparation for a large-scale patient trial in the U.S. and will be used as a basis for our Phase 3 study design which will not include the template bleeding time test," said Cerus Vice President of Medical Affairs Laurence Corash, M.D. "Although not yet finalized, we expect our Phase 3 trial design to focus on a clinical hemostatic endpoint."

The Cerus platelet 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 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.

The company also is developing pathogen inactivation systems for fresh frozen plasma intended for transfusion (FFP) and for red blood cells. The FFP system is based on the same light-activated S-59 compound and is currently in a U.S. Phase 2 clinical study in healthy subjects. The red blood cell system, based on its 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, particularly those regarding product approvals, commercialization and markets, 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.