Novel vaccine technology to suppress the growth of certain tumors

MedImmune, Inc. and Cerus Corporation have announced preclinical results demonstrating the effectiveness of a novel therapeutic vaccine technology in suppressing the growth of certain tumors.

These results will be presented today at the 95th Annual Meeting of the American Association for Cancer Research (AACR) in Orlando, Florida at 8:00 a.m. eastern time. The associated AACR poster is entitled "Recombinant Listeria monocytogenes-Based Immunotherapy Targeting the Receptor Tyrosine Kinase EphA2." "Previous research has indicated that we may be able to promote selective destruction of tumor cells while minimizing the damage to normal cells using EphA2 antibodies," said Peter Kiener, D.Phil., vice president, research at MedImmune. "These new data reveal that we also may one day apply new bacteria-mediated strategies for treating or preventing the many cancers that express the EphA2 protein, including breast and colon cancer." To evaluate the effects of a Listeria-mediated vaccine technology, MedImmune and Cerus scientists implanted mice with tumors and then treated them with Listeria strains that had been genetically engineered to trigger an immune response directed at the EphA2 protein. Protective immunization with Listeria-huEphA2 significantly suppressed tumor growth in this study and prolonged survival for treated mice. Importantly, 80 percent of the Listeria- huEphA2-treated mice survived for greater than 43 days following tumor implantation whereas untreated controls had a median survival time of approximately 20 days. "This research demonstrates the potential to develop potent therapeutic vaccines utilizing our proprietary Listeria vaccine platform in combination with cancer antigens such as EphA2," said Stephen T. Isaacs, president and chief executive officer, Cerus Corporation. "Our vaccine platform is designed to encourage the stimulation of the patient's immune system to selectively recognize and destroy tumor cells expressing the targeted antigen."

About EphA2 & MedImmune, Inc. EphA2 is a protein overexpressed by many different types of human cancers, including melanoma (skin cancer), and breast, lung, prostate and colon cancers. The highest levels of EphA2 have been found on the most aggressive cancer cells, which is consistent with evidence linking EphA2 with clinical features of metastasis. Research to date indicates that EphA2 functions differently on malignant cells than it does on normal cells, and that these differences may help facilitate the selective targeting of cancer cells while minimizing unwanted toxicities to normal cells. MedImmune is a leading biotechnology company focused on researching, developing and commercializing products to prevent or treat infectious disease, autoimmune disease and cancer. MedImmune actively markets four products, Synagis(R) (palivizumab), Ethyol(R) (amifostine), FluMist(TM) (Influenza Virus Vaccine Live, Intranasal), and CytoGam(R) (cytomegalovirus immune globulin intravenous (human)), and has additional products in clinical testing. MedImmune employs approximately 1,800 people, is headquartered in Gaithersburg, Maryland, and has additional operations in Frederick, Maryland, as well as Pennsylvania, California, the United Kingdom and the Netherlands. For more information on MedImmune and its products, as well as for full product prescribing information, visit the company's website at http://www.medimmune.com.

About Listeria Vaccine Program & Cerus Cerus Corporation is developing novel technologies to provide safer and more effective options to patients in areas with substantial unmet medical needs. Cerus' proprietary, versatile vaccine platform technology is based on specially engineered strains of the intracellular bacterium Listeria monocytogenes. Cerus scientists have demonstrated that proprietary strains of Listeria are capable of inducing potent immune responses in laboratory tests. The combination of proprietary strains of Listeria with specific cancer antigens has the potential to harness the power of the immune system to selectively attack malignant cells. Additionally, Cerus is further developing its vaccine platform technology by combining it with its Helinx(R) technology to develop potentially safe and potent therapies and vaccines for infectious disease. Cerus' most advanced program is the INTERCEPT Blood System, designed to enhance the safety of the world's blood supply by inactivating viruses, bacteria, other pathogens and white blood cells. The INTERCEPT Blood System, which is being developed in collaboration with subsidiaries of Baxter International Inc., is based on the company's Helinx technology for controlling biological replication.