Ebola DNA vaccine produces immune responses in all fully vaccinated volunteers in Phase 1 trial

February 21, 2006

Vical Incorporated (Nasdaq:VICL) announced today that an Ebola vaccine candidate administered using Vical's proprietary DNA delivery technology was safe and well tolerated, and produced both antibody and T-cell Ebola-specific responses in all healthy volunteers who received the full 3 doses of vaccine.

The Phase 1, randomized, placebo-controlled, dose-escalation study, the first human trial for any Ebola vaccine, was sponsored by the National Institute of Allergy and Infectious Diseases (NIAID), National Institutes of Health (NIH), and conducted at the NIH Clinical Center. The data were presented at the American Society for Microbiology (ASM) 2006 Biodefense Research Meeting in Washington, D.C., by Julie E. Martin, D.O., a trial investigator and research scientist at NIAID's Dale and Betty Bumpers Vaccine Research Center (VRC), which developed the vaccine. The DNA vaccine used in the Phase 1 trial incorporates genetic material encoding core and surface proteins from two strains of Ebola. Vical has secured a nonexclusive license from the NIH to proprietary gene sequences used in the vaccine.

"The high rates of immune responses at all dose levels in this initial human Ebola vaccine study support continued development of this vaccine and further evaluation of our technology for potential additional biodefense and emerging disease applications," said David C. Kaslow, M.D., Vical's Chief Scientific Officer, "particularly where antibody responses may be protective. Our processes allow rapid development and manufacturing of vaccines without handling potentially dangerous pathogens."

The vaccine used in the Phase 1 trial vaccine included three plasmids (closed loops of DNA), one each encoding the surface glycoprotein (GP) from the Zaire strain of Ebola, GP from the Sudan/Gulu strain, and the internal nucleoprotein (NP) from the Zaire strain. Subjects received three doses of vaccine or placebo at one-month intervals via intramuscular needleless injection. Three cohorts tested progressively higher doses of the vaccine at 2 mg (5 subjects), 4 mg (8 subjects), or 8 mg (8 subjects - with 6 receiving the full three doses). Each cohort included two additional subjects who received placebo instead of active vaccine.

The vaccine was well tolerated, with no severe adverse reactions to the vaccine reported at any of the doses tested. Ebola-specific antibody responses against at least one of the encoded antigens were detected in all vaccine recipients. GP-specific antibody and T-cell responses were detected in all recipients who received the full three doses at all dose levels.
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Animal Rule
A rule published in 2002 by the U.S. Food and Drug Administration (FDA), known commonly as the "Animal Rule," established requirements for demonstrating effectiveness of drugs and biological products in settings where human clinical trials for efficacy are not feasible or ethical. The rule requires as conditions for market approval the demonstration of safety and biological activity in humans, and the demonstration of effectiveness under rigorous test conditions in up to two appropriate species of animal. The company believes that the Animal Rule creates a potentially favorable regulatory pathway for certain DNA-based products such as the Ebola vaccine.

Project BioShield
Project BioShield, a joint activity of the Department of Homeland Security and the Department of Health and Human Services, was signed into law in July 2004 to expand and speed up the availability of vaccines and treatments to combat potential bioterrorism agents. Under the plan, the federal government has earmarked $5.6 billion over 10 years to create and produce vaccines and treatments to guarantee drug companies a buyer for these products. Those funds included an initial procurement of $90 million and long-term procurement of $260 million for Ebola vaccines or treatments. The Ebola DNA vaccine under development by the NIH may be eligible for this stockpiling program.

In December 2005, the U.S. Congress granted authority to the Secretary of the Department of Health and Human Services to declare products as "necessary countermeasures" for a public health emergency, providing the manufacturers and distributors of such products with limited liability protections. The Company believes these protections are essential for vaccines against Ebola and other emerging diseases, which may be needed on an emergency use basis in the event of an outbreak.

About Ebola
Ebola hemorrhagic fever is a serious, often-fatal disease that affects humans and nonhuman primates. The disease is caused by infection with Ebola virus, named after the river in Africa where it was first identified in 1976, and has emerged in sporadic outbreaks in the years since its initial recognition. The Ebola virus is believed to reside in an animal host, or reservoir, between human outbreaks, but specifics of its origin and life cycle are largely unknown. Three of the four identified subtypes of Ebola virus have caused disease in humans: Ebola-Zaire, Ebola-Sudan/Gulu, and Ebola-Ivory Coast. The fourth, Ebola-Reston, has caused disease in nonhuman primates, but not in humans. Ebola is part of a group of illnesses caused by arenaviruses, filoviruses, bunyaviruses, and flaviviruses. These diseases typically impair the body's ability to regulate itself, and symptoms usually include hemorrhage (bleeding). Some types of hemorrhagic fever viruses can cause relatively mild illnesses, but Ebola and others can cause severe, life-threatening disease.

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 has retained all rights to its internally developed product candidates. 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 serve 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 development of the Ebola vaccine; whether Vical or others will evaluate potential additional applications of the company's technology; whether the Ebola vaccine or any other product candidates will be shown to be safe and effective; whether the company's processes will result in rapid development and manufacturing of vaccines; the timing, nature and cost of clinical trials; whether Vical or its collaborative partners will seek or gain approval to market any product candidates; whether the Animal Rule will be applicable to DNA-based products and whether it will provide a favorable regulatory pathway; whether Vical or its collaborative partners will succeed in marketing any product candidates; whether any funding under Project BioShield will be directed to the Ebola DNA vaccine; 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.

Porter Novelli, Life Sciences

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