CONCORD, CA, December 3, 2004 - Cerus Corporation (NASDAQ: CERS) today announced the presention of eight abstracts at the American Society of Hematology (ASH) Annual Meeting taking place on December 4 through 7, 2004, in San Diego, California. The presentations will include data for the INTERCEPT Blood System, as well as new research studies related to Cerus' Listeria cancer vaccine technology. Two INTERCEPT Platelet abstracts will be presented by European collaborators. The INTERCEPT Blood System is being jointly developed to inactivate pathogens in donated blood components by Cerus and subsidiaries of Baxter International Inc. (NYSE: BAX). INTERCEPT Platelets are currently available in Europe, and are being developed for use in Japan and certain other Asian countries by BioOne Corporation.

Two presentations will provide data from Phase III acute and chronic trials with red blood cells, which were halted in September 2003 after antibodies were observed in two patients in the chronic study. A third abstract for the red cell program describes a modified pathogen inactivation process, which may eliminate the immunoreactivity of the treated red cells. Data from a Phase III trial with plasma in thrombotic thrombocytopenic purpura patients, completed in May 2004, will also be presented, including follow-up safety data. European investigators will present an analysis of the practical impact of INTERCEPT Platelets on platelet utilization within a Belgian blood center, and also the interim results of an INTERCEPT Platelet study with pediatric patients. The remaining presentations will cover additional data for the INTERCEPT Blood System programs, as well as research on new therapeutic applications of Listeria.

"These abstracts detail recent progress and results for our three pathogen inactivation programs," said Claes Glassell, president and CEO of Cerus Corporation. "I am also pleased to see our European customers presenting their experiences with INTERCEPT Platelets to the international hematology community. The abstracts on our Listeria technology demonstrate the potential breadth of that proprietary technology platform."

The full text of these abstracts and others being presented at ASH 2004 can be found at http://www.abstracts2view.com/hem_sandiego2004.

Sunday, Dec 5 – Posters (Hall DE)

Immunization with Live-Attenuated Listeria Encoding CMV Antigen Induces Extensive Expansion of CMV-Specific CD8+ T-Cells Following HSCT: An Alternative to Adoptive Antiviral Immunotherapy
Poster #342-II / Abstract #2129

Elimination of Immunoreactivity of Red Cells Treated with a Modified S-303 Pathogen Inactivation Process
Poster #916-II / Abstract #2703

The INTERCEPT Blood System for Plasma: Process Validation Studies of Coagulation Factor Activity and Yield in Two European Blood Centers
Poster #943-II / Abstract #2730

Monday, Dec 6 – Orals – Transfusion Medicine I (Room 6B, 11:00 am – 12:30 pm)

Transfusion of S-303 Treated RBCs To Treat Acute Anemia during or Following Cardiac Surgery: Results of a Phase III Trial
11:30 am / Abstract #381

Antibody Formation to S-303-Treated RBCS in the Setting of Chronic RBC Transfusion
11:45 am / Abstract #382

Monday, Dec 6 – Posters (Hall DE)

Assessment of the Economic Value of the Intercept Blood System for Platelets in Belgium
Poster #426-III / Abstract #3156

Killed but Metabolically Active Recombinant Listeria monocytogenes as an Antigen Delivery and Activation Platform for Human Dendritic Cell-Based Cancer Immunotherapy
Poster #717-III / Abstract #3447

Routine Use of Platelet Components Prepared with Photochemical Treatment (INTERCEPT Platelets): Impact on Clinical Outcomes and Costs
Poster #899-III / Abstract #3629

Safety and Efficacy of Pathogen-Inactivated Platelets Transfused in Routine Use to Pediatric Patients: An Interim Report
Poster #909-III / Abstract #3639

Tuesday, Dec 7 – Orals – Transfusion Medicine II (Room 31, 8:00 am – 10:00 am)

Therapeutic Plasma Exchange (TPE) for Thrombotic Thrombocytopenic Purpura (TTP) Using Plasma Prepared with Photochemical Treatment (INTERCEPT Plasma)
9:45 am / Abstract #838

ABOUT CERUS
Cerus Corporation is developing novel technologies to provide safer and more effective therapeutic options to patients in areas with substantial unmet medical needs, particularly within the fields of cancer, infectious disease and blood safety. The Concord, California-based company is combining its proprietary vector technologies with public domain and proprietary antigens to develop new therapies for cancer and infectious disease. Cerus has two therapeutic cancer vaccine products in development using its Listeria vector technology, one in collaboration with MedImmune, Inc. and the other with Johns Hopkins University. Cerus also is collaborating with subsidiaries of Baxter International Inc. on the INTERCEPT Blood System, which is being developed to enhance the safety of donated blood components by inactivating viruses, bacteria and other pathogens. The INTERCEPT Blood System is based on the company's Helinx technology for controlling biological replication. The INTERCEPT Blood System for platelets is approved for use in the European Union, and is being developed for commercialization in Japan and certain other Asian countries by BioOne Corporation.

Statements in this news release regarding pre-clinical studies, clinical trials, potential efficacy and safety of products, potential regulatory approvals, product development and commercialization and the company's relationship with subsidiaries of Baxter International Inc. and BioOne Corporation 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 uncertainties inherent in developing biotechnology products based on new technologies, the timing and results of clinical trials and other development activities, the acceptability of any data by regulatory authorities, actions by regulatory authorities at any stage of the development process, manufacturing, market acceptance of any products, competitive conditions and other factors discussed in the company's Form 10-Q for the third quarter of fiscal 2004, as well as in other reports filed from time to time with the Securities and Exchange Commission. The company assumes no obligation to update any forward-looking statements.