Vical's Vaxfectin Adjuvant Achieves Dose-Sparing Effect With Seasonal Influenza Vaccine

SAN FRANCISCO, April 11, 2007 /PRNewswire-FirstCall/ -- Vical Incorporated today announced that a seasonal influenza vaccine formulated with the company's Vaxfectin(TM) adjuvant generated up to 60-fold higher antibody responses than an unformulated vaccine at the same dose in a recently completed study in mice. Formulation of sanofi pasteur's Fluzone(R) commercial vaccine with Vaxfectin(TM) also allowed a nearly 10-fold reduction in vaccine dose while generating equivalent or better antibody responses compared with unformulated vaccine, even at the lowest doses tested. Alain P. Rolland, Pharm.D., Ph.D., the company's Senior Vice President of Product Development, presented the data at the Drug Delivery 2007 meeting (San Francisco, April 9 - 11).

Vical is developing its own Vaxfectin(TM)-formulated DNA vaccine designed to protect against emerging strains of influenza virus that have the potential to cause a pandemic. In previously reported studies conducted at St. Jude Children's Research Hospital, Vical's lead Vaxfectin(TM)-formulated, DNA vaccine candidate provided 100% protection in mice and ferrets against lethal challenges with a highly pathogenic strain of H5N1 influenza virus. Initial human testing of Vical's influenza DNA vaccine is expected to begin in the second half of 2007.

Vical tested the Vaxfectin(TM) adjuvant with Fluzone(R) seasonal influenza vaccine to evaluate its potential to ease the anticipated shortage of stockpiled pandemic influenza vaccine and the limited global vaccine manufacturing capacity. In separate studies conducted by others, stockpiled sanofi pasteur H5N1 pandemic influenza vaccine with no adjuvant achieved target levels of antibodies in less than half the subjects after two 90 mcg doses -- a total of six times the normal 15 mcg dose of each strain that provides 75% to 90% protection against seasonal influenza.

The new Fluzone(R) study data confirm and expand on an earlier study in mice, presented last year, which suggested the potential for Vaxfectin(TM) to be used as a dose-sparing agent with conventional influenza vaccines. Both studies used the Fluzone(R) 2005-2006 Formula trivalent inactivated seasonal influenza vaccine. In the recent study, mice were vaccinated with 1, 3, or 9 mcg of Fluzone(R) alone, or Fluzone(R) formulated with one of two dose levels of Vaxfectin(TM). Immune responses were evaluated by measuring hemagglutination inhibition (HI) antibody titers, the accepted standard correlate of protection for conventional influenza vaccines, against a single influenza strain included in the trivalent inactivated vaccine, as well as total antibody titers against all three of the strains included in the vaccine. Vaxfectin(TM)-formulated vaccines yielded HI antibody titers up to 30-fold higher, and total antibody titers up to 60-fold higher than unformulated vaccines at the same dose. Vaccines formulated with even the lowest tested dose of Vaxfectin(TM) yielded equivalent or better immune responses at the 1 mcg dose than unformulated vaccines at the 9 mcg dose, confirming the dose-sparing potential of Vaxfectin(TM). The improved performance of Vaxfectin(TM) in the latest studies reflected further optimization of the Vaxfectin(TM)/vaccine ratio at each of three dosing levels tested in mice.

Vaxfectin(TM) was designed by Vical to increase the immune response to DNA vaccines, and Vaxfectin(TM)-formulated DNA vaccines have demonstrated good tolerability and adjuvant activity in multiple animal models, including nonhuman primates. The Fluzone(R) data suggest that Vaxfectin(TM) could provide a dose-sparing effect with the government-stockpiled H5N1 pandemic influenza vaccine, also produced by sanofi pasteur. Since neither Fluzone(R) nor the sanofi pasteur H5N1 pandemic influenza vaccine are formulated with an adjuvant, Vaxfectin(TM) could, if approved, simply be added to either vaccine prior to administration. Vaxfectin(TM) may have potential applications as an adjuvant for other protein-based vaccines as well. The company holds patents in the United States covering Vaxfectin(TM) and its use with conventional vaccines against infectious diseases and cancer, and in both the United States and Europe covering the use of Vaxfectin(TM) with DNA vaccines.

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 Vaxfectin(TM) as an adjuvant for conventional vaccines against seasonal or pandemic influenza; whether Vaxfectin(TM) will be used as a dose-sparing agent with conventional influenza vaccines against seasonal or pandemic influenza strains; whether Vical or others will continue development of the pandemic influenza DNA vaccine candidate; whether H5N1 or other strains of avian influenza will emerge as pandemic threats; whether the company's DNA vaccine candidate will be effective in protecting humans against H5N1 or other strains of avian influenza; whether the influenza 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; whether Vaxfectin(TM) will provide a dose-sparing effect with the government-stockpiled H5N1 pandemic influenza vaccine; whether Vaxfectin(TM) will be used with other protein-based vaccines; whether Vical or its collaborative partners will seek or gain approval to market the influenza vaccine or any other product candidates; whether Vical or its collaborative partners will succeed in marketing the influenza 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; or Media, Susan Neath of Porter Novelli Life Sciences,+1-619-849-6007, for Vical Incorporated

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

Ticker Symbol: (NASDAQ-NMS:VICL)

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Posted: April 2007

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