Gilead Sciences and Merck have reported positive results from two phase 3 trials backing what could become the first long-acting oral HIV treatment taken once weekly.
The combination regimen pairs Merck’s islatravir with Gilead’s lenacapavir, offering patients a single tablet taken just once per week rather than daily.
The trials, known as ISLEND-1 and ISLEND-2, both achieved their primary efficacy endpoints, marking a significant step forward in HIV treatment development.
The specific doses tested were a 2 mg dose of islatravir combined with a 300 mg dose of lenacapavir, administered together in a single tablet formulation.
The primary efficacy endpoint across both studies was the percentage of participants with HIV-1 RNA levels of 50 copies per millilitre or higher at week 48, defined by the FDA snapshot algorithm.
ISLEND-1 was a double-blind trial that measured the weekly combination against Gilead’s own once-daily pill Biktarvy, with the new regimen demonstrating statistical non-inferiority.
ISLEND-2 was an open-label study in which the weekly pill was compared against standard-of-care daily oral antiretroviral therapy regimens, again achieving statistical non-inferiority.
Both trials enrolled people living with HIV who were already virologically suppressed, meaning the virus was already being effectively controlled before the switch to the new regimen.
No new safety concerns were identified in either study, with the safety profile of the combination described as generally comparable to existing treatment options across both trials.
Islatravir is described as a next-generation nucleoside analog that blocks HIV replication through multiple mechanisms, including reverse transcriptase translocation inhibition, representing an advanced approach to antiviral therapy.
Lenacapavir, developed by Gilead, is a first-in-class capsid inhibitor that disrupts HIV at multiple stages of its lifecycle, and has already gained attention for its role in long-acting HIV prevention.
The pairing of these two drugs from competing pharmaceutical giants represents an unusual cross-company collaboration targeting one of the most persistent challenges in HIV care.
Daily pill regimens, while effective, can present adherence challenges for patients over long periods, making a weekly option a potentially transformative development for long-term disease management.
Gilead and Merck have stated they plan to file the phase 3 data from the ISLEND trials with regulatory authorities globally, with submissions expected to move forward in the near term.
The companies also intend to submit the detailed trial findings for presentation at a future scientific congress, where the broader medical community will have the opportunity to scrutinise the full dataset.