- The National Institutes of Health on Monday discontinued a South African trial of an HIV vaccine regimen after data monitors concluded the treatment hadn't prevented new infections.
- The HTVN 702 study stopped dosing following an interim analysis that was conducted when at least 60% of patients had been in the trial for 18 months. In the group given the vaccine, 129 patients were infected with HIV, while 123 were infected in the trial's placebo arm.
- "We hoped this vaccine candidate would work. Regrettably, it does not," Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said in a statement.
Worldwide, 38 million people are infected with HIV and nearly 2 million new infections happen every year. While effective treatments have been developed that prevent infections from progressing to AIDS, more than 700,000 people died from AIDS-related diseases in 2018.
Researchers hope a vaccine could prevent new infections, but the regimen tested in the Phase 2b/3 study, also known as Uhambo, did not live up to those hopes. The interim analysis consisted of data from 2,694 patients who received the active treatment and 2,689 patients who had been given a placebo, allowing the trial's data safety and monitoring board to draw its conclusion.
The board did not find any safety signals.
When the NIH initiated the trial in 2016, it said the vaccine regimen was the only one ever shown to provide some protection against HIV, citing results from a Thai study.
Researchers based the regimen used in the trial on work conducted by the U.S. Military HIV Research Program and the Thai Ministry of Health in a trial called RV144. In the South African study, the vaccine was adapted to protect against the virus most common there, an HIV subtype called Clade C.
The regimen consisted of a Sanofi Pasteur-supplied, canarypox-based vaccine, dubbed ALVAC-HIV, and a GlaxoSmithKline gp120 protein subunit vaccine with an immunity-boosting adjuvant, both modified to be specific to subtype C. Those two shots were followed with boosters at 12 and 18 months.
An earlier trial of this regimen had shown that it stimulated antibodies to several HIV strains. However, that biomarker finding was not confirmed as having a benefit in preventing infections.
Johnson & Johnson and NIH have initiated a Phase 3 trial of another two-vaccine regimen that aims to cover a number of HIV subtypes. Called MOSAICO, that trial will also use HIV infection rates as its primary measure and is scheduled to yield final results in 2023.