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Multiple NIH Phase 2 HIV Vaccine Trials Using Vical's Technology Produce Encouraging Results

Thursday, August 23, 2007 General News J E 4
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SEATTLE, Aug. 22 Vical Incorporated(Nasdaq: VICL) announced today that results from a series of HIV vaccine Phase2a clinical trials, using a plasmid DNA (pDNA) vaccine developed by the NIHVaccine Research Center and manufactured by Vical, reinforced previouslyreported Phase 1 conclusions that a "DNA prime-adenoviral vector boost"vaccine regimen was safe and well-tolerated, and was effective in inducingT-cell immune responses in up to 70% of the vaccine recipients.

"These recent vaccine trials contribute to the growing body of knowledgedemonstrating plasmid DNA priming as a key factor in achieving significantimmune responses against HIV, a particularly difficult target pathogen,bringing us one step closer to evaluating the effectiveness of a prime-boostHIV vaccine regimen in a prophylactic setting," said Vijay B. Samant, Vical'sPresident and Chief Executive Officer. "The latest International AIDS VaccineInitiative (IAVI) listing of ongoing preventive HIV vaccine clinical trialsshows that more than half use pDNA either alone or in combination with othervaccine modalities. We are very pleased that DNA technology is an integralpart of the effort to address this high priority global health problem."

The trials involved priming an immune response with three doses of a pDNAvaccine over a two month period, based on Vical's proprietary DNA technology,and boosting the response with a single dose of adenoviral vector vaccine atsix months. The three trials, collectively known as TRIAD, were conducted bythe National Institute of Allergy and Infectious Diseases (NIAID) HIV TrialsVaccine Network (HVTN), the IAVI, and the U.S. Military HIV Research Program(USMHRP). Richard Koup, M.D., Chief of Immunology at the Dale and BettyBumpers Vaccine Research Center (VRC), NIAID, National Institutes of Health(NIH), highlighted TRIAD summary results and conclusions in an oralpresentation, "Update on safety and immunogenicity of VRC products," at theAIDS Vaccine 2007 conference (Seattle - August 20-23).

About the Vaccine

The "prime-boost" strategy uses two vaccine components given at differenttimes. Both contain synthetic versions of genes encoding three HIV proteins:gag, pol and env. The DNA component also includes a gene encoding a fourthprotein, nef. The gag, pol and nef genes come from HIV subtype B, the primaryvirus found in Europe and North America. The env gene encodes an HIV coatprotein that allows the virus to recognize and attach to human cells. Thevaccine incorporates modified env genes from subtypes A and C, most common inAfrica and parts of Asia, as well as subtype B. These three subtypescollectively represent about 85 percent of HIV infections worldwide.

The two vaccine components differ in how the genes are packaged. The pDNAcomponent contains only the specific gene sequences in a pDNA ring, and cannotreconstitute into an infectious virus. The adenoviral vector component uses areplication-defective adenoviral vector to shuttle the same non-infectiousgene sequences into the body. The pDNA vaccine used in the trials wasdeveloped by VRC scientists and was manufactured by Vical. The adenoviralvector vaccine was developed by VRC in collaboration with GenVec Inc., ofGaithersburg, Md., which also manufactured the adenoviral vector vaccine.

About Vical

Vical researches and develops biopharmaceutical products based on itspatented DNA delivery technologies for the prevention and treatment of seriousor life-threatening diseases. Potential applications of the company's DNAdelivery technology include DNA vaccines for infectious diseases or cancer, inwhich the expressed protein is an immunogen; cancer immunotherapeutics, inwhich the expressed protein is an immune system stimulant; and cardiovasculartherapies, in which the expressed protein is an angiogenic growth factor. Thecompany is developing certain infectious disease vaccines and ca
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