HIV drugs have made the virus manageable, but pharmaceutical companies continue to pursue vaccines that could offer people a preventative measure. One such effort from Johnson & Johnson has fallen short in a mid-stage clinical trial testing the vaccine in young, heterosexual women in southern Africa.
J&J said Tuesday that the primary analysis of the Phase 2b study showed that the vaccine did not provide enough protection against HIV infection. Based on those results, the clinical trial will not continue.
The J&J HIV vaccine is based on a “mosaic” of immunogens, the components that are designed to induce immune responses against a range of HIV strains found across the world. It’s made using the pharma giant’s proprietary AdVac technology, the basis of the company’s FDA-approved Ebola vaccine and the Covid-19 shot that was granted emergency use authorization. Like those vaccines, the HIV shot uses a strain of adenovirus, a virus that causes the common cold, engineered so that it does not cause infection. That virus delivers to cells four mosaic antigens intended to elicit an immune response.
The sub-Saharan Africa clinical trial was funded by the Bill & Melinda Gates Foundation and the National Institute of Allergy and Infectious Diseases. Begun in 2017, the study enrolled about 2,600 young women in Malawi, Mozambique, South Africa, Zambia, and Zimbabwe—a region of the continent in which women and girls accounted for an estimated 63% of all new HIV infections last year, according to United Nations joint program UNAIDS.
Trial participants received four vaccinations over the course of one year. At the third and fourth vaccination visits, the shots included an adjuvant, an ingredient that boosts the immune response. A primary analysis was conducted one year after the final shot. That analysis showed the vaccine was only 25.2% effective at preventing infection, J&J said. Women who acquired HIV were directed to medical care and offered treatment.
The results are a sharp contrast to tests the strong efficacy demonstrated in preclinical research conducted in monkeys. Against a simian version of HIV, the J&J vaccine reduced the risk of infection by 94%, according to results reported in 2017. But the Phase 2b results offer another example of human testing failing to reproduce the encouraging data from animal research. In a prepared statement, Paul Stoffels, J&J’s chief scientific officer, said that HIV has long posed challenges for vaccine research because of the virus’s ability to attack, hijack, and evade the human immune system.
The J&J vaccine was safe and well tolerated by patients, and no serious adverse events were reported. That’s one encouraging sign for another J&J HIV experimental vaccine candidate with a different composition. That vaccine is currently being evaluated in men who have sex with men and transgender people. Like the vaccine evaluated in the Africa study, this vaccine is also comprised of four immunogens but reflects the different strains circulating in the Americas and Europe where the pivotal study is underway. Given those differences, the independent data safety monitoring board decided that this Phase 3 study should continue, J&J said. According to the National Institutes of Health, which is providing funding for the clinical research, this study is expected to finish in 2024.