Vaxfectin-formulated Measles DNA Vaccine Elicits Long-term Protection and Sterilizing Immunity in Nonhuman Primates

SEATTLE, May 31, 2007 /PRNewswire-FirstCall/ -- Vical Incorporated today announced that a measles DNA vaccine formulated with the company's Vaxfectin(TM) adjuvant elicited protective levels of neutralizing antibodies in juvenile (1 - 2 year old) nonhuman primates confirmed by complete protection following challenge more than one year after vaccination, and sterilizing immunity as evidenced by no clinical signs of disease and no detectable virus after challenge. In a separate study, the same vaccine elicited protective levels of neutralizing antibodies in infant (6 - 10 weeks old) nonhuman primates with no vaccine-related adverse events. The studies were conducted in collaboration with Diane E. Griffin, M.D., Ph.D., Alfred and Jill Sommer Professor and Chair of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, under a grant from the Bill and Melinda Gates Foundation.

"Sterilizing immunity is a rarely achieved ultimate goal in vaccination," said Vijay B. Samant, Vical's President and Chief Executive Officer. "The ability to provide such complete immunity with no adverse events offers proof of concept for Vaxfectin(TM)-formulated DNA vaccines. We look forward to continued development of the measles vaccine program by our collaborators at Johns Hopkins."

"We have tested a number of measles DNA vaccines, and the data relating to Vical's Vaxfectin(TM)-formulated DNA vaccine showed marked differences both in terms of disease resistance after exposure and antibody levels over the other vaccines, without significant side effects," said Dr. Griffin. "These data are exciting because of the potential of providing safety and efficacy suitable for infants and young children in the developing world, and continued development could result in a major impact on global measles disease and death rates."

The study in juvenile rhesus macaques tested the protective efficacy of a bivalent DNA vaccine encoding measles hemagglutinin and fusion glycoproteins. Vaccine was delivered by intradermal needle-and-syringe injection of two 0.5 mg doses or by intramuscular needle-and-syringe injection of two 1.0 mg doses at four-week intervals. All vaccines were formulated with Vical's patented Vaxfectin(TM) adjuvant. Neutralizing antibody levels exceeded the accepted protection threshold prior to the second injection at Week 4, peaked at Week 5, and remained well above the accepted protection threshold for more than one year, with no difference noted between routes of administration. Animals were challenged by intratracheal inoculation at Week 55, resulting in complete protection of all vaccinated animals against disease symptoms. None of the vaccinated animals had detectable levels of measles virus at any time point tested, in contrast to negative control animals which all had detectable virus. Measles-specific T-cell responses were also detected after vaccination. The vaccines were well-tolerated in all animals.

The study in infant rhesus macaques tested only intradermal needle-and- syringe delivery of vaccine at the same 0.5 mg dose used in the juvenile animals. Neutralizing antibody levels exceeded the accepted protection threshold prior to the second injection at Week 4, peaked at Week 8, and remained above the accepted protective level throughout the 20-week follow-up period. No adverse events related to the vaccination were observed. Data were presented by Adrian Vilalta, Ph.D., Vical's Senior Scientific Manager of Immunogen Discovery, at the annual meeting of the American Society of Gene Therapy (Seattle, May 30 - June 3).

About Measles

Routine vaccination with a live attenuated measles vaccine has largely eliminated the disease among children in most developed countries, however, it remains among the top ten infectious disease causes of deaths among young children worldwide because of poor vaccine acceptance in some countries, poor vaccine availability in others, and lack of effectiveness in young infants. Measles causes approximately one of every five deaths from vaccine-preventable diseases in children under age five. The disease is particularly prevalent in infants less than one year old in developing countries, and is most severe among those who are malnourished.

About Vical

Vical researches and develops biopharmaceutical products based on its patented DNA delivery technologies for the prevention and treatment of serious or life-threatening diseases. Potential applications of the company's DNA delivery technology include DNA vaccines for infectious diseases or cancer, in which the expressed protein is an immunogen; cancer immunotherapeutics, in which the expressed protein is an immune system stimulant; and cardiovascular therapies, in which the expressed protein is an angiogenic growth factor. The company is developing certain infectious disease vaccines and cancer therapeutics internally. In addition, the company collaborates with major pharmaceutical companies and biotechnology companies that give it access to complementary technologies or greater resources. These strategic partnerships provide the company with mutually beneficial opportunities to expand its product pipeline and address significant unmet medical needs. Additional information on Vical is available at www.vical.com.

This press release contains forward-looking statements subject to risks and uncertainties that could cause actual results to differ materially from those projected, including: whether Vical or others will continue evaluation of the Vaxfectin(TM)-formulated measles DNA vaccine; whether the vaccine will be effective in protecting juvenile or infant humans against measles infection or disease; whether the measles vaccine or any other product candidates will be shown to be safe and effective in clinical trials; the timing, nature and cost of clinical trials; the availability of future funding to support the cost of continued development; whether Vical or its collaborative partners will seek or gain approval to market the measles vaccine or any other product candidates; whether Vical or its collaborative partners will succeed in marketing the measles vaccine or any other product candidates; whether the company's issued patents will be challenged and whether such challenges will have an adverse effect on the scope of the patents; whether the company will enforce its issued patents or will be successful in any enforcement efforts; and additional risks set forth in the company's filings with the Securities and Exchange Commission. These forward-looking statements represent the company's judgment as of the date of this release. The company disclaims, however, any intent or obligation to update these forward-looking statements.

    Contacts:  Investors:                         Media:

               Alan R. Engbring                   Susan Neath

               Vical Incorporated                 Porter Novelli Life Sciences

               (858) 646-1127                     (619) 849-6007

               Website:  www.vical.com

CONTACT: Investors, Alan R. Engbring of Vical Incorporated,+1-858-646-1127; Media, Susan Neath of Porter Novelli Life Sciences,+1-619-849-6007

Web site: http://www.vical.com//

Ticker Symbol: (NASDAQ-NMS:VICL)

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Posted: May 2007

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