Injectables, implants may be the future of HIV prevention
Scientists are getting ready to start large-scale trials next month using injections to protect vulnerable groups against HIV for at least two months, in a step that will take HIV prevention to the next level.
The scientists are also hoping to produce matchstick-sized implants containing slow-release drugs – similar to existing under-the-skin contraceptive devices – that could offer year-long protection. Companies involved include Glaxo Smith Kline (GSK), Gilead Sciences and Merck.
The initiatives build on the success of Gilead’s once-daily pill Truvada, which has proved remarkably effective at stopping HIV infection during sex.
Clinical studies show such pre-exposure prophylaxis (PrEP) can cut the risk of catching the virus by more than 90%, as long as people take their pills regularly.
However, not many people do so. Some women in trials in Africa, for example, said they were reluctant to have HIV tablets in the house for fear of what partners or neighbors would think.
An injection given in a clinic, experts argue, would add privacy and ensure steady drug levels. An implant in the arm might even combine contraception and HIV protection in one go.
“Now that we know antiretrovirals have great potential to prevent HIV infections, it is time to really assess other ways to deliver these drugs,” said Jean-Michel Molina, professor of infectious diseases at Hospital Saint-Louis in Paris, France.
Despite treatment advances that have slashed AIDS deaths, the number of people catching HIV each year has remained unchanged since 2010 at around 1.9 million. New infections among gay men are actually increasing.
The United Nations AIDS program recently warned that the problem now threatened progress in ending the global epidemic, while the World Health Organization has recommended PrEP for all groups at substantial risk of HIV infection.
GSK’s majority-owned ViiV Healthcare unit, working with US government agencies and the Bill & Melinda Gates Foundation, hopes to add the first injectable PrEP.
It plans to start a four-year trial as soon as next month testing its experimental drug cabotegravir in gay men in the Americas and Thailand, with a second trial next year assessing the medicine in African women.
Two separate studies evaluating cabotegravir in combination with another drug for HIV treatment were launched this month.
“The holy grail is a vaccine, but we don’t have a vaccine yet,” said Myron Cohen of the University of North Carolina at Chapel Hill, who is involved in the ViiV prevention study program and believes new options can help rein in HIV.
He is also working on another prevention trial giving people antibodies via an intravenous drip.
Meanwhile, Gilead is also running a late-stage study assessing its next-generation HIV drug Descovy as an alternative oral PrEP, since it has milder side effects than Truvada.
In the long run, Cohen and other HIV experts are especially excited by slow-release drug implants. Implants have yet to prove themselves in human trials, although an experiment in beagles last year with a Gilead drug produced promising results. Products from GSK and Merck are also seen as implant options.
The size of the HIV prevention market remains uncertain and price will be an issue, especially in Africa, but some industry analysts believe it could be substantial.
Truvada, the only medicine so far approved for HIV prevention, is now being used for PrEP by 80,000-90,000 people in the US, accounting for 35-45% of the drug’s revenue in the third quarter.
It is starting to gain tractionin Europe as well, with France offering free supplies, while in Britain and other markets, where it is not paid for by the government, people are turning to online “buyers’ clubs” to get cut-price generics.
