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SAN DIEGO -- Vical Incorporated has announced the initiation of a Phase 1 clinical trial with its novel DNA vaccine for anthrax. The trial will test the vaccine in up to 52 healthy adult volunteers for safety and immune responses. Successful completion of this trial could lead to potential larger trials to support marketing approval under the U.S. Food and Drug Administration (FDA)'s Animal Rule, and could encourage development of other vaccines using the same technology. The trial is being supported by the U.S. National Institute of Allergy and Infectious Diseases (NIAID) of the National Institutes of Health (NIH) at two NIAID-funded Vaccine and Treatment Evaluation Units (VTEUs).
Dosing of all subjects should be completed by early 2005, said David C. Kaslow, M.D., Vicals chief scientific officer, providing an opportunity by early next year to evaluate interim results. Both the safety and immunogenicity results from this trial should provide critical information required to advance toward our objective of developing a well-tolerated, highly efficacious anthrax vaccine.
The multi-center, randomized, double-blind, placebo-controlled, dose-escalating clinical trial is designed to evaluate the safety and immunogenicity of Vicals prophylactic, cationic lipid-formulated, bivalent plasmid DNA anthrax vaccine. Each subject will receive three doses of the vaccine or placebo at doses from 0.2 milligrams to 2.0 milligrams. All subjects will be followed for up to one year. Although the primary endpoint of the trial is safety, secondary endpoints in this trial include the immunogenicity of the vaccine at the various doses and regimens.
This clinical trial brings a state-of-the-art DNA vaccine optimized for eliciting antibodies to the proof-of-concept stage for the first time in man, added Kaslow. In addition to addressing a pressing public need to counter bioterrorism, we expect to confirm the more general ability of lipid-formulated DNA vaccines to elicit biologically relevant antibody responses in humans, which would lead to a substantial broadening in the range of potential vaccine applications.
Anthrax is a serious infectious disease most frequently occurring in hoofed mammals, but also affecting humans exposed to the spore-forming Bacillus anthracis. Bacterial spores can survive for extended periods and become active upon gaining access to a host. Human infection with anthrax spores can occur after exposure through a cut or abrasion on the skin or through ingestion of contaminated meat, but the most serious risk is through inhalation.
Inhalation anthrax results in death for 90 percent to 100 percent of those exposed, if not treated promptly. Symptoms typically appear within a week of exposure, and may be misdiagnosed as a common cold or flu. Bacterial spores travel from the lungs to the lymph nodes, where they begin to grow. Eventually, they spread into the circulatory system and throughout the body, causing widespread internal bleeding and organ failure. People who work with animals or process animal products are at greatest risk of naturally acquired infection. The greatest potential threat for most people is the inhalation of anthrax spores used in biological warfare or in a bioterrorist attack.
The toxic effects of anthrax infection are the result of three proteins produced by the bacteria: edema factor (EF), lethal factor (LF) and protective antigen (PA). PA couples with either EF or LF and allows these toxins to penetrate and kill host cells, releasing large numbers of bacteria into circulation. Treatment for proven or suspected anthrax infection involves a long course of antibiotic therapy beginning as soon as possible after diagnosis or suspected exposure. Antibiotics used against anthrax work by killing the bacteria to prevent further production of the toxic proteins. They do not eliminate proteins that accumulate before treatment, and do not offer residual protection against infection after the treatment course has been completed. The U.S. licensed anthrax vaccine and others under clinical development target PA alone. Vicals bivalent vaccine targets both PA and LF.
Source: Vical Incorporated