Gilead to test once-a-year HIV prevention shot

Gilead said Tuesday that it will soon begin Phase 3 testing for a drug it believes could prevent HIV infection with just a single shot every year.

Such a medicine, if proven effective, would be the closest thing to a vaccine the HIV field has produced in four decades of research. The company plans to begin the trial next year, with an eye toward regulatory filings in late 2027.

The once-a-year drug is another formulation of lenacapavir, a medicine that already made headlines this year when Gilead published data showing it could prevent HIV infections with just one shot every six months.

Gilead executives revealed the 12-month formulation at an analyst day dedicated to its HIV portfolio. They said they recently completed a pharmacokinetics study — i.e. tracking how a drug behaves in the body — that gave them confidence to advance the molecule.  They will present that data next year. 

The trial comes amid a series of rapid advancements in the field of PrEP, as drugs that prevent HIV are known. PrEP has been available for a decade in the form of a daily pill. But that can be hard for many people to take consistently, for a variety of reasons, and HIV infections have continued to surge or remain roughly flat in many places. 

In 2021, the Food and Drug Administration approved the first injectable form of PrEP, called Apretude. It’s given every two months. Gilead plans to file approval for its once-every-six-month regimen next year. Because it’s so much easier to take — just go to a clinic twice a year — the drug proved substantially more effective than traditional oral prep.

Global access to these new forms of PrEP remains uncertain, though. Former CDC director Rochelle Walensky criticized Apretude’s maker, ViiV, for failing to make the drug more accessible in Africa and pushed Gilead to swiftly make lenacapavir broadly available. Gilead has signed deals to make the drug available in low- and middle-income countries, but advocates say they could go further. 

These drugs are notably not vaccines. Vaccines train the immune system to recognize the virus and provide some level of durable protection long after the vaccine has left the body. PrEP medications consist of one or more antivirals and are effective only as long as they stay in the body.

The challenge has been getting them to stay in for long periods of time. But there has been substantially more progress in that field than in the vaccine field, which has struggled to turn the immune system against one of the wiliest viruses humanity has ever encountered. After a recent failure, there are currently no HIV vaccines in late-stage trials — and the advent of effective, long-term PrEP could actually make it harder for researchers to develop one. 

Next year’s trial will test just one of several formulations of lenacapavir the company is working on as it pushes for an annual shot, said Gilead vice president Jared Baetan.

In addition to the annual shot, Gilead is working on longer-acting oral forms of PrEP that could be taken once a week or even once a month. Merck previously tested a once-a-month oral PrEP but halted the trial after safety concerns emerged for its molecule.