Scientists identify new vaccine targets for cancer-causing strains of human papilloma virus

March 26, 2001

New vaccine approach may help treat and prevent pre-cancerous lesions and cervical cancer

San Diego, CA - March 27, 2001 - Epimmune Inc. (Nasdaq: EPMN) announced today that Company scientists, in collaboration with Loyola University, Chicago, IL, Leiden University Medical Center, The Netherlands, and University of Wales College of Medicine, Wales, UK, have identified new vaccine targets for cancer-causing strains of the human papilloma virus (HPV). The scientists reported in today's issue of the Journal of Clinical Cancer Research the discovery of four epitopes (protein fragments) from the virus that can induce a cellular immune response in human cells in vitro and may lead to an effective vaccine for treatment and prevention of cervical intraepithelial neoplasia (CIN), pre-cancerous lesions that develop into cervical cancer.

An estimated 20 million Americans are infected with HPV, a virus that is well known for causing genital warts but also accounts for over 95 percent of cervical cancer cases. CIN lesions, which precede most if not all cases of cervical cancer, occur in over 50,000 women in the United States each year. Currently, CIN is detected by PAP smear and treated by surgical removal of the pre-cancerous lesions, a costly procedure that may result in reproductive complications and requires continual post-surgery monitoring for recurrence. Epimmune is developing a vaccine that is designed to bolster the immune system against HPV, potentially providing a new way to treat and prevent both CIN and cervical cancer.

"Previous research has indicated that a cellular immune response led by cytotoxic T cells is capable of controlling tumor growth and destroying virus-infected cells in HPV-infected patients," said Alessandro Sette, Ph.D., Vice President and Chief Scientific Officer at Epimmune. "Our research shows that it may be possible to emulate this successful immune response with a vaccine that consists of epitopes from several cancer-causing strains of HPV."

There are over 70 identified types of HPV, but a relatively few "high-risk" strains, including HPV-16 and HPV-18, are known to cause CIN and cervical cancer. Using Epimmune's proprietary Epitope Identification System™, the Epimmune scientists have identified epitopes predicted to activate cytotoxic T cells (CTLs) from several proteins of most cancer causing HPV strains. The current study showed that four epitopes from HPV-18, three derived from E6 and one derived from E7, were highly immunogenic using human cells in vitro, meaning they induce a CTL response.

Research by others has indicated that E6 and E7 proteins are "oncoproteins" that are responsible for the transformation of HPV-infected cells into CIN and cancer cells. Epimmune believes that a vaccine based on epitopes derived from these proteins may provide strong therapeutic benefit by teaching the immune system to recognize and attack HPV-infected cells at all stages of pre-cancerous and cancerous development.

"An effective vaccine to treat CIN and cervical cancer must target multiple cancer-causing strains of HPV," said Robert Chesnut, Executive Vice President, R&D at Epimmune. "Epimmune's approach directly addresses this challenge by combining epitopes from multiple virus strains into a single vaccine to combat all of the HPV strains frequently associated with causing cancer."

"Recently completed clinical trials (see note) of an HPV epitope-based vaccine have shown the potential benefit of this approach to treat CIN," said W. Martin Kast, Ph.D., Professor of Microbiology, Immunology and Pharmacology at Loyola University Chicago Stritch School of Medicine and Director of the Cancer Immunology Program at the Cardinal Bernardin Cancer Center of Loyola University Medical Center. "The conformation of additional HPV epitopes, such as those identified in the current study, is important in creating an effective vaccine." Dr. Kast is the senior author of the HPV epitope identification study entitled "Human T-cell responses to HLA-A restricted high binding affinity peptides of HPV-18 proteins E6 and E7", which appears today in the Journal of Clinical Cancer Research (Volume 7, Issue 3, Supplement, March 2001).
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Epimmune's cancer program is focused on developing vaccines for breast, colon and lung cancer as well as prostate and CIN/cervical cancer. Epimmune Inc. is a leader in using gene maps of cancer-associated proteins and infectious agents to design vaccines that induce cellular immunity. The Company's extensive technology platform is based on its pioneering work in deciphering the genetic code which regulates T-cell activation and identifying antigen fragments known as epitopes which can activate highly targeted T-cell responses to tumors, viruses, bacteria and parasites. This new field of pharmacology opens two significant areas of pharmaceutical development: protective vaccines that activate T-cell protection against infections, such as HIV and hepatitis C, and therapeutic vaccines designed to stimulate antigen-specific T-cell responses to infections, such as HIV, hepatitis C and hepatitis B, and tumors such as breast, colon, lung and prostate. For more information on Epimmune, visit www.epimmune.com.

Epitope Identification System™ (EIS) is a trademark of Epimmune, Inc.

Note: For more information, see Journal of Clinical Cancer Research, 6:3406, 2000.

This press release includes forward-looking statements that reflect management's current views of future events, including the utility of the Company's technology and the anticipated benefits of cancer vaccines being developed by the Company. Actual results may differ materially from the above forward-looking statements due to a number of important factors, including but not limited to the risks associated with the Company's ability to develop vaccines using epitopes, the ability of epitope-based vaccines to control cancer and infectious diseases, the safety and efficacy of epitope-based vaccines in humans, the Company's ability to enter into and maintain new collaborations, achievement of research and development objectives by the Company and any collaborator, the timing and cost of conducting human clinical trials, the regulatory approval process, and the possibility that testing may reveal undesirable and unintended side effects or other characteristics that may prevent or limit the commercial use of proposed products. These factors are more fully discussed in the Company's 1999 Form 10-K, the most recent 10-Qs and other periodic reports filed

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