An investigational HIV vaccine tested in the "Imbokodo" clinical trial conducted in sub-Saharan Africa posed no safety concerns but did not provide sufficient protection against HIV infection, according to a primary analysis of the study data, as reported in a news release from the National Institutes of Health (NIH).
The Imbokodo study, also known as HVTN 705/HPX2008, is sponsored by Janssen Vaccines & Prevention B.V., part of the Janssen Pharmaceutical Companies of Johnson & Johnson. It is funded by two primary partners, the Bill & Melinda Gates Foundation (BMGF) and the National Institute of Allergy and Infectious Diseases (NIAID), part of NIH.
The Phase 2b proof-of-concept study, which began in November 2017, enrolled 2,637 women 18-35 years old from five countries.
The Imbokodo primary analysis was conducted 24 months after participants received their first vaccinations. The study's primary endpoint was based on the difference in the number of new HIV infections between the placebo and vaccine groups from month seven (one month after the third vaccination timepoint) through month 24.
When comparing the number of new HIV infections between study participants who were randomly assigned to receive either placebo or the investigational vaccine, statisticians found that 63 participants who received the placebo and 51 participants who received the experimental vaccine acquired HIV infection. Therefore, the investigational vaccine's efficacy was 25.2%. The study vaccine was found to be safe with no serious adverse events associated with it. Study participants are being informed of the findings and will have follow-up visits with the study investigators. Further analysis of the Imbokodo study will continue, and the study is thought to have provided sufficient data for further immunological correlates research.
"The development of a safe and effective vaccine to prevent HIV infection has proven to be a formidable scientific challenge," said NIAID Director Anthony S. Fauci, M.D. "Although this is certainly not the study outcome for which we had hoped, we must apply the knowledge learned from the Imbokodo trial and continue our efforts to find a vaccine that will be protective against HIV."
Earlier research indicated the vaccine was both well-tolerated and could induce an anti-HIV immune response. Imbokodo participants received four vaccinations during a one-year period. This included four doses of the investigational quadrivalent vaccine. The final two doses were administered together with doses of an HIV protein, clade C gp140, and an adjuvant to boost immune responses. Participants were followed for at least two years. The primary analysis occurred one year after the last study participant's final vaccination.