The US Food and Drug Administration has just approved lenacapavir, an injectable form of HIV prevention that is almost 100 percent effective and requires only two doses per year. Science magazine described the medicine the most important scientific advance of 2024.

In clinical trials, lenacapavir proved to be 99.9 percent effective in preventing HIV infection through sexual transmission in people weighing more than 35 kilograms. The drug, an antiretroviral, works not by stimulating an immune response, but by blocking HIV from reproducing during its early stages—specifically, by disrupting the function of the virus’s capsid protein. This happens so long as the body receives injections every six months.

Lenacapavir has already been approved in some countries as a treatment for HIV in people with forms of the virus that are resistant to other treatments. However, prior to this week, its prophylactic use had not been approved anywhere, making the FDA’s decision a significant new development in the fight against the HIV/AIDS epidemic.

The drug is not the first medicine that can be taken preemptively to protect against an HIV infection: pre-exposure prophylaxis (PrEP) pills were already available in many countries, including the United States. But these must be taken every day, and ensuring ongoing access to these medicines, and that people actually remember to take them, is a known challenge. It’s hoped the long-lasting effects of lenacapavir will make it easier for people to stay protected against the virus.

According to its creator, Gilead Sciences, lenacapavir will be marketed under the trade name Yeztugo. The company has committed to manufacturing 10 million doses by 2026.

“This is a historic day in the decades-long fight against HIV. Yeztugo is one of the most important scientific breakthroughs of our time and offers a very real opportunity to help end the HIV epidemic,” Daniel O’Day, president and CEO of Gilead, said in a statement on Wednesday.

However, lenacapavir’s price may be a barrier to access. Yeztugo will have an annual list price of $28,218 per person in the US. Winnie Byanyima, executive director of of the Joint United Nations Program on HIV/AIDS (UNAIDS), has also flagged in the past that the drug is unaffordable for many people in Africa, where the medicine has the potential to have the biggest impact. Roughly two-thirds of the people living with HIV worldwide live in sub-Saharan Africa.

On Wednesday, Gilead published details of a two-part plan to offer access to lenacapavir “in 120 high-incidence, resource-limited countries, which are primarily low- and lower-middle-income countries.” One step will be “voluntary licensing,” which is where other companies are granted permission to produce and sell generic versions of a patented product in a certain country. Alongside this, the company says it plans “to provide Gilead-supplied product at no profit to Gilead until generic manufacturers are able to fully support demand in voluntary licensing countries.”

This story originally appeared on WIRED en Español and has been translated from Spanish.

Updated 6-20-2025 3:30 pm BST: Details of Gilead Science’s strategy for providing access to lenacapavir in low- and lower-middle-income countries were added.