A once-weekly HIV pill combining Merck's islatravir and Gilead's lenacapavir matched the effectiveness of daily treatment in a Phase 3 clinical trial, the companies announced, with data presented at the AIDS 2026 conference.
The trial tested a combination tablet containing 2 milligrams of islatravir and 300 milligrams of lenacapavir against Gilead's daily pill Biktarvy in adults with HIV who switched from an existing antiretroviral regimen. Through 48 weeks, the once-weekly pill was non-inferior to daily treatment at maintaining viral suppression: none of the participants who switched to the weekly pill had HIV-1 RNA levels of 50 copies per milliliter or higher, compared with 0.3% of those who stayed on daily Biktarvy. More than 93% of participants in both groups remained virally suppressed throughout the trial, according to Merck and Gilead.
A sharp drop in reported burden
Beyond viral suppression, the trial also measured how burdensome patients found their treatment. About two-thirds of participants said their previous daily regimen felt burdensome, compared with just 1% who said the same about the new weekly pill, according to aidsmap. More than three-quarters of participants reported greater overall satisfaction with the weekly regimen. The companies said no new safety signals emerged during the trial.
Islatravir and lenacapavir work through different mechanisms: lenacapavir targets the protein shell that protects HIV's genetic material, while islatravir blocks an enzyme the virus needs to replicate. Combining them into a single once-weekly tablet is intended to reduce the daily pill-taking burden that can make it harder for some patients to stay consistently adherent to treatment, a factor known to affect long-term viral suppression and the risk of drug resistance developing over time.
The combination pill has not yet been approved by the U.S. Food and Drug Administration. Merck and Gilead said the Phase 3 results will support future regulatory submissions, though neither company gave a specific filing timeline in its announcement.
If approved, the pill would mark one of the first major shifts in HIV treatment from daily to weekly dosing, following years of research aimed at simplifying regimens for the millions of people living with HIV worldwide.