VICAL INITIATES TRIAL OF THERAPEUTIC HIV VACCINE

Vical has initiated an NIH-sponsored Phase I trial of a prime/boost vaccine approach designed to prevent or control disease in patients already infected with HIV. The trial involves priming an immune response with multiple doses of a plasmid DNA vaccine, based on Vical's proprietary DNA delivery technology, and boosting the response with a single dose of adenoviral vector vaccine given at a later date.

The vaccine incorporates HIV genetic material from the three most globally important HIV subtypes, clades A, B and C, which are involved in about 85 percent of all HIV infections. Results from another Phase I trial in subjects not infected with HIV showed that the prime-boost approach was well-tolerated and effective in producing potent cellular and antibody immune responses, including specific responses against each of the HIV subtypes.

The vaccine used in the Phase I trial incorporates parts of four HIV genes. Three of these vaccine components are modified versions of HIV genes called gag, pol and nef, synthetically made based on sequence from clade B, the subtype that predominates in Europe and North America. The fourth vaccine component is a modified version of the HIV gene named env. The env gene codes for a protein on the outer coat of the virus that allows it to recognize and attach to human cells. The trial is double blinded and placebo controlled and will evaluate safety, tolerability and immune response.