Epitope-Based Vaccine Promising for HIV Treatment and Prevention.

KEYSTONE, Colo.--(BW HealthWire)--Jan. 14, 1999--Epimmune Inc., a majority-owned subsidiary of Cytel Corp. (Nasdaq:CYTL), today announced presentations by its scientists and collaborators of initial data suggesting that epitope-based vaccines hold promise for the control of HIV infection.

Data from two HIV related model studies were presented at the "Conference on HIV Vaccine Development" in Keystone, Colo.

"These initial results provide further support for our continued pursuit of development of an epitope-based HIV vaccine," said Robert W. Chesnut, Ph.D., executive vice president, Research and Development of Epimmune. "In one study involving macaque monkeys, a significant cytotoxic T-cell (CTL) response was induced in all vaccinated animals. The other study, conducted in transgenic mice, demonstrated the ability of our EpiGene(TM) construct to simultaneously induce potent responses to multiple CTL epitopes."

The first study involved macaque monkeys infected with simian immunodeficiency virus (SIV), an AIDS-like virus. Prior to infection with SIV, three monkeys were vaccinated with a single CTL epitope using a Dermal PowderJect(R) Delivery System. In all three vaccinated animals, a significant CTL response was induced against the epitope, while no CTL response was detected in the four unvaccinated animals.

During the eight weeks after infection with a highly virulent strain of SIV, the three vaccinated monkeys produced CTL responses that peaked three weeks sooner than the non-vaccinated animals -- an event thought to be important for combating virus infection. The monkey with the most significant CTL response showed a greatly reduced (close to 95 percent) level of virus in the blood.

"These results support the idea that CTL play a central role in the control of SIV and HIV infections," stated David I. Watkins, Ph.D., Professor of Pathology at the Wisconsin Regional Primate Research Center (WPRC), and Principal Investigator of the macaque study. "The data also demonstrate that epitopes can be used to target and activate a strong immune response. We plan to further evaluate the potential of epitope-based vaccines using multiple SIV epitopes."

Collaborating with Dr. Watkins on the macaque study were Drs. Alessandro Sette (Epimmune); Todd Allen (WPRC); Tomas Hanke and Andrew McMichael (Oxford University); John Altman (Emory University); and Deborah Fuller (PowderJect Vaccines).

In parallel with the macaque work, Epimmune scientists have defined multiple epitopes from HIV that are being used to create a multi-epitope human vaccine. Results of this work in transgenic mice were also presented at the conference.

The data demonstrated the effective delivery of multiple human HIV epitopes using the EpiGene construct, a DNA vector encoding the selected epitope sequences. The results showed that multiple HIV epitopes, specific for different HIV antigens, could simultaneously induce strong CTL responses to each of the epitopes.

"Both the breadth and strength of responses are believed to be very important for controlling the viral infection," added Dr. Chesnut. "Based on results to date in model systems, we believe that an EpiGene vaccine has the potential to induce CTL responses that are more potent and target more epitopes than vaccines using whole proteins or genes."

Epimmune Inc., established in October 1997, is a majority-owned subsidiary of Cytel Corp. (Nasdaq:CYTL), operating under separate management and financing. Applying its substantial immunology expertise and scientific leadership in the field of T-cell recognition and activation, Epimmune is developing novel vaccines which stimulate the body's immune system to treat and prevent infectious diseases and cancer.

Epimmune is collaborating with G.D. Searle & Co., a wholly-owned subsidiary of Monsanto Co., to develop immune stimulating products for the treatment of cancer. Additional product targets include prophylactic vaccines for hepatitis C, HIV and malaria and therapeutic vaccines for hepatitis B, hepatitis C and HIV.

This press release includes forward-looking statements that reflect management's current views of future events. 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 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 Cytel's most recent Forms 10-K and 10-Q.