The wait for an HIV vaccine goes on. Johnson & Johnson, having seen peers including Merck swing at HIV and miss, has reported the failure of a vaccine based on similar technology to its COVID-19 jab to protect women from infection with the virus.
Investigators randomized around 2,600 young women across five countries in sub-Saharan Africa to receive four doses of the vaccine or placebo over one year. The researchers calculated the efficacy of the vaccine in the phase 2b clinical trial by looking at the number of HIV cases in each cohort from Month 7, one month after the third dose, to Month 24.
The analysis revealed 63 cases in the placebo arm and 51 cases in the slightly smaller vaccine cohort. J&J calculated the efficacy to be 25.2%, with a lower confidence interval of below 0%. While J&J said the vaccine was generally well tolerated, the efficacy data were too weak to support further study.
While J&J is stopping the study, a phase 3 trial of a related vaccine regimen is continuing. The phase 3 study is testing a different composition of the HIV vaccine regimen and enrolling men who have sex with men and transgender individuals in the Americas and Europe, where the circulating strains are different than in sub-Saharan Africa. The differences between the trials led to the continuation.
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J&J is continuing to analyze data from the failed phase 2b study. One outstanding question is why the high levels of protection seen in animals shrank in humans. J&J moved the candidate into advanced clinical trials on the strength of evidence it slashed infection rates in animals.
The continuation of the phase 3 trial, which has a primary completion date in 2024, gives J&J another crack at providing protection against HIV. Other vaccine developers are tackling the challenge, too, with Moderna set to start testing a mRNA candidate imminently.
Moderna’s approach is different from what has gone before. While J&J’s study looked at whether non-neutralizing antibodies can induce protection against HIV, Moderna is trying to use mRNA to generate broadly neutralizing antibodies against the virus. Neutralizing antibodies could prevent HIV from entering cells.