A hopeful new chapter in HIV prevention is emerging, thanks to striking results from two major clinical trials of Lenacapavir, a twice-yearly injectable drug developed to help protect people from HIV.

In the first study, PURPOSE 1, researchers tested the medicine in Uganda and South Africa, where HIV incidence remains high. The trial included 3,200 participants and focused on young women receiving a subcutaneous injection of Lenacapavir every six months.

The outcome was remarkable: there were no new HIV infections among the women who received the drug, showing 100% efficacy in that group.

That joyful progress continued with PURPOSE 2, a broader trial that included 5,000 participants across more countries and continents. This time, the study expanded beyond young women to include men and people of different ages. Once again, the results were deeply encouraging, with a 99.9% reduction in infection rates.

Both PURPOSE trials were phase 3 clinical trials using randomized, double-blinded protocols. Rather than comparing Lenacapavir with a placebo, researchers measured it against the current standard in HIV prevention: daily pills such as Truvada or Descovy.

Those daily pills are also highly effective when taken consistently, having shown 99.9% protection during development. But taking medication every single day can be difficult to maintain over the long term. A twice-a-year injection offers a simpler path, making it easier for people to stay protected.

The benefits may reach beyond medical convenience. In places where stigma around HIV risk remains painful and where male homosexuality is illegal, such as Uganda, avoiding the visibility of a daily prevention pill could offer people greater privacy, comfort, and dignity.

The promise of the twice-yearly injection was so strong that both PURPOSE trials were stopped early for ethical reasons. Participants then received a 52-week follow-up to screen for HIV developments.

Lenacapavir was named Science Magazine’s Breakthrough of the Year in 2024 and has been approved by the FDA for use in humans under the brand name Yeztugo.

The drug works by targeting the HIV capsid, the protective shell the virus depends on during its life cycle. It binds to a “highly conserved” protein on the outside of that shell, meaning the target remains present even as the virus mutates. By disrupting the capsid’s precise process of breaking down and rebuilding, Lenacapavir prevents HIV from completing its life cycle.

Bringing a drug like this to the world takes enormous investment. Research and development, regulatory requirements, and the need to prove safety and effectiveness mean Gilead Sciences likely spent well over a billion dollars developing Lenacapavir, based on typical pharmaceutical development costs.

Even so, Gilead has committed to providing the drug at cost in certain low-income regions. The company has also licensed generic manufacturers to produce it for around $40 per year in 120 low- and middle-income countries beginning in 2027.

With powerful trial results, easier adherence, and plans to expand access, Lenacapavir offers a bright and compassionate step forward in the global effort to prevent HIV.