Promising results for a once-weekly HIV treatment pill are reported | AIDS 2026

Prospects for a weekly pill for HIV treatment are looking bright after findings from two phase 3 trials were presented today at AIDS 2026, the 26th International AID Conference, in Rio de Janeiro, in Brazil.

The weekly pill is a combination of islatravir, a nucleoside reverse transcriptase translocation inhibitor developed by Merck, and lenacapavir, a capsid inhibitor developed by Gilead Sciences, that has become well-known as an effective preventive agent in its long-acting injectable form.

Results from the two trials, named ISLEND-1 and ISLEND-2, were shared at a press conference last week, but researchers presented them formally today at the conference, sponsored by the International AIDS Society.

The ISLEND-2 results that were presented this morning show that at week 48, which is halfway through the scheduled length of the trial, one (0.3%) person among the 314 randomly selected to treatment with the weekly islatravir-lenacapavir pill had a viral load of HIV-1 RNA of 50 copies per milliliter (mL) or greater, which the investigators had set as the primary end point. Four (1.3%) study participants among the 312 who were randomly selected to remain on daily treatment pills had a viral load of HIV-1 RNA of 50 copies per mL or more.

The ISLEND-1 results, which are scheduled to be presented this afternoon, paint the same basic picture. The abstract shared at the press conferences says that at week 48, none of the approximately 300 patients randomly selected to receive treatment with the weekly islatravir-lenacapavir pill developed a viral load of HIV-1 RNA of 50 copies per mL or more, while one in the comparison group developed that viral load. In ISLEND-1 the comparison group were study participants who continued taking a daily treatment pill that contains three antiretrovirals, bictegravir, emtricitabine and tenofovir alafenamide, and is sold under the name Biktarvy in the U.S.

In both trials, the results met the statistical test of noninferiority.

The ISLEND-2 results show far more treatment-related adverse events among those taking the weekly islatravir-lenacapavir than those in the standard-of-care comparator group (58 vs. 1), but when the researchers narrowed the analysis to more serious adverse events (grade 3 or higher), neither group had any.

Amy E. Colson, M.D., M.P.H., research director at the Community Resource Initiative in the Boston Area, who presented the ISLEND-2 results this morning, noted that the greater number of adverse events seen in the islatravir-lenacapavir group is consistent with the pattern seen in open-label studies that involve a study group that switches from established treatment to an experimental one. Colson said that all the treatment-related adverse events were grade one or grade two.

One theme of the meeting in Rio is that the primary limitations in the global response to HIV are now political and economic, not scientific. The positive result for weekly oral treatment raises questions about what the price and availability of the islatravir-lenacapavir combination might be after what now seems like eventual approval by the FDA and other drug regulators and launch on the market. The countries with the greatest number of people living with HIV are in low- and moderate-income countries. Last week, a spokesman for Gilead shared a written statement that said it was “too early” to say what the price of the islatravir-lenacapavir pill might be. “Our decades of experience collaborating with a range of stakeholders will help us explore pathways with the goal of facilitating rapid uptake and broad access around the world,” the statement said, referring to both Merck and Gilead.