There's a new beacon of hope in HIV prevention. Recent results from a phase 3 trial reveal that a twice-yearly injection of the drug to treat AIDS offers 100% efficacy in preventing new infections.

In a landmark trial involving 5,000 young women and adolescent girls in South Africa and Uganda, not a single HIV infection was reported among those who received two shots of lenacapavir, from drugmaker Gilead.

Participants were randomly assigned to either receive lenacapavir injections every 26 weeks or take daily oral HIV medications, such as emtricitabine–tenofovir alafenamide (F/TAF) or emtricitabine–tenofovir disoproxil fumarate (FTC/TDF). The study was double-blind, so participants were unaware of which treatment they were receiving.

The results revealed that approximately 2% of those taking the daily pills contracted HIV from infected partners, highlighting the effectiveness of lenacapavir compared to the daily oral medications.

"With zero infections and 100% efficacy, twice-yearly lenacapavir has demonstrated its potential as an important new tool to help prevent HIV infections. We look forward to additional results from the ongoing PURPOSE clinical program and continuing toward our goal of helping to end the HIV epidemic for everyone, everywhere," said Dr. Merdad Parsey, Chief Medical Officer from Gilead Sciences.

Around 69% of the participants experienced injection-site reactions, compared to 35% in the placebo group. However, the researchers reported that no safety concerns were found.

Lenacapavir, marketed as Sunlenca, is already a prescription medication for HIV treatment. Having successfully wrapped up the PURPOSE 1 trial, researchers look forward to the results of the PURPOSE 2 trial that evaluates the effectiveness of the twice-yearly lenacapavir injections in preventing HIV across diverse populations and regions.

"These data confirm that twice-yearly lenacapavir for HIV prevention is a breakthrough advance with huge public health potential. If approved and delivered – rapidly, affordably, and equitably – to those who need or want it, this long-acting tool could help accelerate global progress in HIV prevention. We all owe a debt of gratitude to the thousands of young women in South Africa and Uganda who volunteered to be part of this study," Sharon Lewin, President of IAS – the International AIDS Society, said in a news release.

"Now we eagerly await results from PURPOSE 2, which is assessing twice-yearly lenacapavir for HIV prevention in other populations and countries. In the meantime, all stakeholders must work together to accelerate equitable delivery of existing HIV prevention options, and do more to prepare for future options, such as lenacapavir for PrEP," Lewin said.

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