Cerus Corporation Announces Publication in Nature Medicine; Killed But Metabolically Active Microbes -- A New Class of Vaccines.

CONCORD, Calif. -- Cerus Corporation (NASDAQ:CERS) announced today the publication in the August issue of Nature Medicine an article entitled, "Killed But Metabolically Active (KBMA) Microbes: A New Vaccine Paradigm For Eliciting Effector T-Cell Responses And Protective Immunity." Collaborators on the paper included scientists from Cerus Corporation and UC Berkeley. The article details the development of a new class of vaccines, called KBMA vaccines, based on bacteria that have been killed at the genetic level, but maintain their metabolic activity and immunologic potency. KBMA vaccines offer the prospect of combining the potency of live vaccines and the safety of killed vaccines.

KBMA technology has potential medical applications in several areas. First, KBMA vaccines may be used as therapeutics for treating intracellular pathogens such as HIV, HBV, HCV, tuberculosis and malaria. There is a critical need for more effective therapies against these intracellular agents. Second, KBMA vaccines may have a role in protection from bioterror agents such as anthrax, tularemia and bubonic plague, where a live bacterial vaccine would be inappropriate due to safety concerns. Cerus Corporation received $3.8 million in July 2004 from the National Institutes of Health to develop an anthrax vaccine based on its KBMA platform.

"We are pleased to be featured on the cover of Nature Medicine. The scientific results in this peer-reviewed publication reaffirm the significance of our KMBA platform," said Tom Dubensky, PhD, vice president of vaccine research, Cerus Corporation. "This novel class of vaccines may offer considerable advantages for patients requiring treatment for chronic infections."

KBMA vaccines are based on bacteria with engineered deletions in a widely shared DNA repair pathway. KBMA vaccines are killed by introducing a small number of crosslinks in their genome, which blocks replication of their DNA. However, the vast majority of genes can be transcribed to mRNA, and protein synthesis is largely unaffected. KBMA bacteria thus behave metabolically and immunologically as though they are alive, yet they cannot cause infection. A broad range of diseases can be addressed by programming these bacteria to express specific antigens, resulting in the induction of targeted immune responses. The article demonstrates that KBMA vaccines are much more immunologically potent than conventionally killed vaccines.

ABOUT CERUS

Cerus Corporation is developing novel products for cancer, infectious disease and blood safety based on multiple, innovative technology platforms. The company is building a pipeline of next generation cancer immunotherapies by combining its proprietary attenuated Listeria vector platform with promising disease antigens. These products are designed to stimulate innate and T-cell immune pathways, generating highly potent anti-tumor responses. Cerus is applying its Helinx technology to develop the INTERCEPT Blood System, which is designed to enhance the safety of blood components through pathogen inactivation. The company's strategy is to leverage the broad potential of its technologies and products through alliances. Cerus' partners to date include MedImmune and Johns Hopkins University for cancer immunotherapy, and Baxter International and BioOne for the INTERCEPT Blood System.

Helinx is a trademark of Cerus Corporation.

Baxter and INTERCEPT are trademarks of Baxter International Inc.

Statements in this news release regarding potential efficacy of products based on our vaccine platform, product development and commercial potential, and the company's relationship with its partners 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 our clinical trials and other research and development activities, market acceptance of our products, competitive conditions, actions by partners and collaborators and other factors discussed in the company's Form 10-K/A for fiscal 2004, as well as in other reports subsequently filed from time to time with the Securities and Exchange Commission. The Company assumes no obligation to update any forward-looking statements.