Cerus Corporation Starts Vaccine Trial for Epstein-Barr Virus.

Business Editors & Health/Medical Writers

CONCORD, Calif.--(BUSINESS WIRE)--Feb. 4, 2003

Cerus Corporation (Nasdaq:CERS) today announced the initiation of a Phase I clinical trial of an experimental Epstein-Barr virus (EBV) vaccine designed to protect transplant patients from the often fatal malignancies arising from the virus. The study will be conducted at the Kimmel Cancer Center at Johns Hopkins, supported in part by a grant from the National Institutes of Health.

"We are extremely pleased to collaborate with Johns Hopkins on this research study," said John Hearst, Ph.D., vice president of New Science Opportunities at Cerus Corporation. "This early vaccine work signals the further expansion of therapeutic applications of our Helinx(R) technology for controlling biological replication."

The Phase I trial, expected to enroll up to 40 organ transplant patients, will evaluate the safety and efficacy of the cellular vaccine in generating EBV-specific immune responses. The vaccine is produced by taking immune cells from the patient, infecting them with EBV and then treating those cells with Cerus' photochemical Helinx technology to inactivate the virus. The resultant cellular vaccine will be administered to the patient prior to organ transplantation.

Epstein-Barr virus infections can cause serious complications in solid organ transplant patients, including the development of a malignant lymphoma, which can often be fatal. The incidence of these tumors varies according to the organ transplanted, the age group of the recipient, and the immunosuppressive regimen used. Patients not previously exposed to the virus prior to transplantation are at least 10 times more likely to develop a malignant lymphoma than those who have been exposed.

The Helinx compound (amotosalen HCI), when activated, binds to and crosslinks nucleic acids (DNA and RNA), and has the ability to prevent the replication of viruses, bacteria and other pathogens, and to control cellular proliferation. The photoinactivated EBV infected immune cells are designed to stimulate a strong cellular immunity against the Epstein-Barr virus-associated lymphoma.

ABOUT CERUS

Cerus Corporation is building on its leading position in the biopharmaceutical industry by developing medical systems and therapeutics to provide safer and more effective options to patients. The company is developing products based on its proprietary Helinx technology for controlling biological replication. Cerus' most advanced programs are focused on systems to enhance the safety of the world's blood supply. The INTERCEPT Blood System, which is being developed in collaboration with Baxter Healthcare Corporation, is based on the company's Helinx technology. The Intercept Blood System is designed to inactivate viruses, bacteria, other pathogens and white blood cells. The Concord, California-based company also is pursuing therapeutic applications of Helinx technology to treat and prevent serious diseases.

Helinx is a trademark of Cerus Corporation

Intercept Blood System is a trademark of Baxter International, Inc.

Statements in this news release regarding clinical trials, regulatory filings, product development and commercial potential are 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 risks and uncertainty of the timing and results of clinical trials and other development activities, actions by regulatory authorities at any stage of the development process, additional financing activities, manufacturing, market acceptance of any products, competitive conditions and other factors discussed in the companies' most recent filings with the Securities and Exchange Commission.