Business Editors/Health/Medical Writers

CONCORD, Calif.--(BUSINESS WIRE)--July 23, 2003

Cerus Corporation (Nasdaq:CERS) today announced study results demonstrating that the INTERCEPT Blood System for platelets and red blood cells inactivates the causative agent of Severe Acute Respiratory Syndrome (SARS). The INTERCEPT Blood System for platelets, approved for commercial use in Europe, is a blood safety technology that protects patients by reducing the risk of transfusion-transmitted diseases. Cerus is developing the INTERCEPT Blood System for use with platelets, plasma and red blood cells in collaboration with subsidiaries of Baxter International Inc.

"We are pleased to report these inactivation results as the launch of INTERCEPT platelets gets underway in Europe and we continue late-stage development of our products in the United States," said Stephen T. Isaacs, president and chief executive officer of Cerus. "SARS is another example of an emerging and migrating pathogen that the FDA has stated may pose a safety risk to the blood supply. Since the INTERCEPT Blood System is designed to inactivate both known and, potentially, emerging pathogens, we believe the technology will offer a more comprehensive approach to maintaining a safe blood supply than is currently available."

Although there have, as yet, been no reported cases of SARS transmission through blood transfusion, the organism has been detected in the blood of infected individuals. The FDA has issued a guidance document to blood centers to defer blood donors that have traveled to certain geographies with SARS outbreaks, and there is no test currently available to screen for the virus in donated blood.

The in-vitro study measured the ability of the INTERCEPT Blood System to inactivate the Urbani strain of the SARS virus in samples of both platelets and red blood cells where the virus had been added. The particular isolate used, which causes the SARS respiratory illness in humans, is named after Carlo Urbani, the scientist who first identified the pathogen prior to his own exposure to, and death caused by, SARS. Following the INTERCEPT Blood System inactivation procedure, the blood products were tested for residual viable virus. Results of this study show that the virus was inactivated below the limit of detection in the assay system showing greater than one-million fold inactivation with no viable virus detected after treatment.

Cerus will be presenting this data at the National Heart, Lung, and Blood Institute Workshop on Pathogen Reduction and Blood Component Safety: Critical Issues and Decision Making on July 31 in Bethesda, Maryland.

The INTERCEPT Blood System is designed to provide an added level of protection for the blood supply from pathogens, such as HIV, hepatitis, SARS, and West Nile viruses as well as a spectrum of bacteria and parasites. Unlike tests used to detect pathogens in blood, the system's fundamental mechanism of action facilitates comprehensive inactivation of pathogens without the need for modifications according to the specifics of the particular virus, bacteria or parasite. Several blood centers in Europe use the INTERCEPT Blood System for platelets to add an additional layer of safety to the blood supply. Clinical trials for use of the INTERCEPT Blood System with plasma and red blood cells for transfusion are also underway in the United States.

Currently, SARS has infected approximately 8,000 people worldwide and has a mortality rate of 15 percent and up to 50 percent in elderly patients. This single-stranded RNA coronavirus has been detected in the blood of infected patients during the acute phase of the illness. It is therefore suspected that the virus may be transmissible through blood. The current strategies in place to prevent the spread of SARS through blood transfusions include a worldwide donor deferral program instituted by the World Health Organization (WHO) and research surrounding test development to enable screening and detection.

Cerus Corporation is developing medical systems and therapeutics based on its proprietary Helinx(R) technology for controlling biological replication. Cerus' most advanced programs are focused on systems to enhance the safety of blood products used for transfusion. The INTERCEPT Blood System, based on the Cerus Helinx technology, is being developed to inactivate viruses, bacteria, parasites 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 U.S. registered trademark of Cerus Corporation. Baxter and INTERCEPT Blood are trademarks of Baxter International Inc.

Statements in this news release regarding regulatory filings, product development, potential efficacy against emerging pathogens 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 and commercialization process, additional financing activities, manufacturing, market acceptance of any products, competitive conditions and other factors discussed in the company's most recent filings with the Securities and Exchange Commission.