The Food and Drug Administration has just approved a preventative HIV drug widely regarded as a breakthrough.

On Wednesday afternoon, the FDA approved Gilead Sciences’ lenacapavir as a more convenient form of pre-exposure prophylaxis (PrEP). In clinical trials, the drug was shown to be highly effective at preventing HIV infection when taken just twice a year. At the same time, advocates are urging Gilead and U.S. officials to ensure the drug is widely accessible to the public.

“PrEP is one of the most indispensable tools we have for ending the HIV epidemic. Having the option of a twice-annual shot, rather than relying on a daily pill, will make long-term adherence to PrEP much easier for many,” said Kevin Robert Frost, CEO of amfAR, the Foundation for AIDS Research, in a statement provided to Gizmodo. “But this remarkable drug will only be as effective as it is accessible and affordable.”

The FDA first approved lenacapavir in 2022 as an antiretroviral treatment for HIV, marketed under the name Sunlenca. It was the first approved treatment of a novel drug class for HIV—drugs that directly target the capsid, or shell, of the virus. That alone has made lenacapavir a vital advance, since it can potentially treat infections that have become resistant to other drugs. But the drug’s greatest potential might come from its vaccine-like ability to prevent the virus from ever gaining a foothold in the first place.

A year ago, Gilead released the results of its PURPOSE 1 Phase III trial, which tested out a twice-yearly PrEP injection of lenacapavir in cisgender women. The drug outperformed daily PrEP options with a 100% prevention rate. A later trial also showed a 99.9% prevention rate among cisgender men, transgender men and women, and gender non-binary individuals. The drug’s success was so impressive that Science Magazine named it as the research breakthrough of the year. Gilead is also now studying if a single yearly dose can be just as effective.

As monumental as lenacapavir’s arrival for PrEP may be, its cost could pose a problem—especially given Gilead’s reputation. The company has long set high and often increasing list prices for its earlier PrEP drugs and it has fiercely resisted attempts by the U.S. and others to lower these prices (even today, a month’s supply of Truvada can cost up to $2,000 without insurance). Gilead has also been accused of trying to delay the development of cheaper generics, though these now exist; in 2023, the company settled a class action lawsuit over these allegations.

NBC News reported Wednesday that the PrEP version of lenacapavir, sold under the brand name Yeztugo, will have a list price of $14,109 per injection, or $2,352 per month. In its announcement of the FDA approval, Gilead stated that it is “working closely with insurers, healthcare systems and other payers with the goal of ensuring broad insurance coverage.” It will also establish programs intended to reduce Yeztugo’s out-of-pocket costs as low as $0 for some eligible people with or without insurance.

Time will have to tell whether these assurances will be enough to make the drug widely affordable and accessible to Americans and eventually everyone else in the world.

“amfAR calls on Gilead Sciences and the U.S. government to do everything in their power to make sure as many people who want lenacapavir can get it,” Frost said.