The decades-long quest to develop an HIV vaccine has suffered another major setback, with the ‘last in development’ failing to prevent disease better than a placebo in clinical trials that are about to end.
The international Mosaico study, which began in 2019 and involved more than 3,900 volunteers, was investigating the HIV vaccine for more than 4 people in cisgender men and transgender people who have sex with cisgender men and/or transgender people.
As the US National Institute of Allergy and Infectious Diseases (NIAID) reported last week, the trial was stopped after a review of the data prepared by the research and safety management team found that the vaccine is safe, but not effective.
“For our research colleagues and others who have worked for years to develop a vaccine to end the HIV/AIDS epidemic, these results are disappointing,” lead researcher Susan Buchbinder, an HIV researcher at the University of California, San Francisco, said. in a sentence.
“While HIV continues to be a challenge for vaccine development, the HIV research community remains committed to doing just that, and each study brings us closer to this realization.”
The vaccine was being developed by Janssen, the vaccine arm of Johnson & Johnson, who are testing a vaccine delivery system similar to their current COVID-19 vaccine.
Despite decades of research, only one person has shown that they have little power in preventing HIV infection. Cwas established in the early 2000s, that is the largest HIV vaccine trial to date. Researchers were hoping for a change in these results, with an HIV vaccine offering more protection.
To do this, the Mosaico trial, and other similar studies, were investigating a vaccine based on ‘mosaic’ immunogens – particles from several types of HIV – designed to teach the immune system to recognize the many types of HIV in the world. the whole world. .
This was thought to be a promising way to fight HIV, a notoriously fast-changing virus, still many steps ahead of vaccine development. It also protects itself from being recognized by antibodies with high-sugar proteins.
At the time the trial was launched, Buchbinder said it represented “an important step in the development of a safe and effective HIV vaccine for people around the world.”
That sentiment is true, even when the case ends. Experts say the way the test has improved participant selection, removed barriers to access to preventive medicine, and included those at high risk of HIV will have long-term benefits.
Volunteers enrolled in the trial only if they were offered, and refused, antiretroviral drugs that would prevent HIV infection. This medicine, called HIV pre-exposure prophylaxis (PrEP), is taken every day. Those who chose PrEP were linked to treatment, and trial participants who later changed their minds and wanted to use PrEP could do so.
“One thing we’ve learned from the participants in this study is that people want a choice, and that vaccination should be an option for those who don’t want PrEP,” Buchbinder said.
“The ethical and public nature of this research has helped build trust in communities that may not trust research institutions,” added Mitchell Warren, director of the AIDS Vaccine Advocacy Coalition.
Other efforts to develop an HIV vaccine are ongoing. Three HIV mRNA vaccines are currently being tested in phase I clinical trials, which will investigate whether the vaccine is safe and can stimulate an immune response.
“Finding an HIV vaccine has been a major scientific challenge,” public health expert and former NIAID director Anthony Fauci said in a statement last year.
“With the success of a safe and highly effective COVID-19 vaccine, we have an exciting opportunity to determine whether mRNA technology can do the same against HIV.”
The problem is, phase I safety trials are a long way from phase III trials that provide information on whether a new vaccine (or drug) is effective or not, so it will be years until we see someone arrive late.
As Warren told health reporter Helen Branswell at Stat News, the results of the latest trial are a “stark reminder” of the challenges of developing an HIV vaccine.
At least five experimental HIV vaccines, tested in nine trials, have failed in efficacy trials, Warren said. They suspect that the problem is not in the vaccination methods – which have worked against COVID-19 – but in the safety targets that the HIV vaccine aims to hit.
“Our problem is figuring out what we want,” Warren told Branswell. “We have cars. We don’t even know what people can put in cars.”
A difficult task against a shapeshifting virus.
