GeoVax Labs (OTCMKTS:GOVX) said on Monday the simian analogue of its human immunodeficiency virus (HIV) vaccine, GOVX-B11, provided a 76% reduction in per exposure risk of simian immunodeficiency virus (SIV) infection in young adult rhesus macaques.
Per exposure risk was assessed over 12 weekly rectal exposures. The study, supported by the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health (NIH), also showed the vaccine providing much better protection for young adult than middle-aged and older macaques.
The test vaccine used a DNA vaccine expressing non-infectious virus-like particles (VLPs) to prime the immune response and a modified vaccinia Ankara (MVA) vaccine, also expressing non-infectious VLPs, to boost the primed response.
The vaccine regimen included two DNA primes at initially and in week 8 followed by two MVA boosts at weeks 16 and 32.
The efficacy of the vaccine was tested at 6 months after the final MVA boost by 12 weekly rectal exposures to a pathogenic SIV given at a dose that infected approximately 30 percent of the unvaccinated animals at each challenge. Animals that were less than 10 years old (estimated human age of about 40) had much better protection than those over 10 years old. The age-dependence for protection was stronger than typically seen for vaccines and likely reflects the HIV target for protective antibody being particularly well-camouflaged.
The human version of the vaccine, GOVX-B11, has undergone clinical testing through the NIAID-supported HIV Vaccine Trials Network (HVTN) in Phase 1 and 2a trials involving about 500 individuals.
These trials have shown the vaccine to have excellent safety and reproducible ability to elicit immune responses. Based on the results of the clinical trials, as well as the current preclinical trial, further evaluation of the GOVX-B11 vaccine in humans will use two DNA primes followed by three MVA boosts with the 16 week rest used in this trial between the last two MVA boosts.
GeoVax shares were up 1.6% at $0.07.