Press Release Details

Cerus to Present at American Association for Cancer Research Annual Meeting; Preclinical Safety and Efficacy Data Support Use of Proprietary Listeria Platform for Cancer Immunotherapy

April, 19 2005

ANAHEIM, Calif.--(BUSINESS WIRE)--April 19, 2005--Cerus Corporation (Nasdaq:CERS) today announced the presentation of two abstracts at the 96th American Association for Cancer Research Annual Meeting (AACR) taking place from April 16 through 20, 2005, in Anaheim, California. The presentations will include preclinical efficacy and safety data from studies using Cerus' proprietary Listeria platform, both alone and in combination with selected target antigens such as Mesothelin, a tumor antigen that is over-expressed in pancreatic and ovarian cancers. The study results indicate that Cerus' Listeria-based vaccines can generate potent anti-tumor responses while maintaining safety, and can also be administered repeatedly as part of a chronic treatment regimen. The company currently has three cancer immunotherapy products in preclinical development, including CRS-100, CRS-207, and MEDI EphA2.

"We are pleased to be at AACR presenting such promising new data supporting the use of our Listeria platform for cancer immunotherapy," said Claes Glassell, Cerus' president and chief executive officer. "Cerus has gained significant momentum this past year in our development of immunotherapy products, and we look forward to filing our first Listeria IND this year."

In the first presentation, "Recombinant Listeria monocytogenes-Based Immunotherapy Targeting Mesothelin for the Treatment of Pancreatic and Ovarian Cancer," the authors report the construction and evaluation of novel immunotherapeutics based on the Listeria platform strain expressing the Mesothelin tumor antigen. In studies of patients with pancreatic cancer, immune responses to this antigen have correlated with long-term patient survival. In Cerus' studies using tumor-bearing mice, immunization with these candidate vaccines resulted in therapeutic anti-tumor efficacy and increased survival. Additionally, high doses of the Listeria platform strain were delivered safely in non-human primates by two different routes of administration. Collectively, this data suggests that the combination of human Mesothelin as an immune target with Cerus' Listeria vector offers a promising strategy for active immunotherapy targeting pancreatic and ovarian cancers.

The second presentation, "Recombinant Listeria Induce and Boost Antigen-Specific Immune Responses In the Presence of Listeria-Specific Cellular and Humoral Immunity," provides strong evidence that pre-existing immunity to Listeria will not prevent Cerus' vaccines from stimulating potent immune responses to target antigens. The majority of the human population has been exposed to Listeria through food, and repeated administration of a Listeria-based vaccine would also be expected to generate a Listeria-specific response in recipients. Data presented by researchers at Cerus indicate that, even in the presence of pre-existing immunity, experimental Listeria-based vaccines can still stimulate antigen-specific immune responses, and that the responses can be boosted with additional vaccinations. This data distinguishes the Cerus platform from conventional biological vectors, including commonly used viral vectors. In addition, the evidence further supports the development of Cerus' novel immunotherapies for repeated administration to treat cancer and other chronic diseases.

Cerus' Attenuated Listeria Platform

Cerus' proprietary Listeria platform strain was systematically selected from a library of genetically defined, attenuated Listeria strains. This strain shows significantly higher safety margins than other strains, yet preserves Listeria's ability to generate potent innate and adaptive immune responses. Cerus' Listeria platform, often in combination with selected cancer or infectious disease antigens, has the potential to create potent and effective therapeutics that train the immune system to target malignant or infected cells.

About CRS-100, CRS-207 and MEDI EphA2

CRS-100, based on Cerus' Listeria platform strain, is currently under development for treatment of liver metastases in colorectal cancer patients. In CRS-207, Cerus' proprietary attenuated Listeria platform is being engineered to express Mesothelin, creating a therapeutic designed to stimulate potent anti-Mesothelin immune responses to target and destroy tumor cells. Similarly, MEDI EphA2, being developed in collaboration with MedImmune, Inc., will use Cerus' Listeria to generate immune responses to the cancer antigen EphA2. All three programs are currently in preclinical development.

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 The Johns Hopkins University for cancer immunotherapy, and Baxter International Inc., and BioOne Corporation 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 and safety of products based on our vaccine platform, potential regulatory approvals and 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 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, actions by partners and collaborators, competitive conditions and other factors discussed in the company's Form 10-K for 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.

    CONTACT: Cerus Corporation
             Lainie Corten, 925-288-6319

    SOURCE: Cerus Corporation

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