Phase 3 Trial of Weekly Oral Islatravir-Lenacapavir for HIV-1 Treatment

Once-daily, single-tablet regimens have transformed care for persons living with human immunodeficiency virus type 1 (HIV-1); however, challenges to adherence continue to limit effective treatment. Long-acting oral-drug combinations could offer new options with less frequent dose administration.

We conducted a phase 3, double-blind, randomized, active-controlled, noninferiority trial in 12 countries to evaluate the efficacy and safety of a switch to once-weekly oral islatravir-lenacapavir (ISL/LEN) from once-daily oral bictegravir-emtricitabine-tenofovir alafenamide (B/F/TAF) in adults in whom HIV-1 had been virologically suppressed for at least 6 months while they were receiving B/F/TAF. Participants were assigned in a 1:1 ratio to receive once-weekly ISL/LEN (2 mg/300 mg) or to continue once-daily B/F/TAF for 96 weeks; all received matched placebo for the alternative regimen. The primary end point was the percentage of participants with an HIV-1 RNA level of 50 copies per milliliter or higher at week 48, as determined by the Food and Drug Administration-defined snapshot algorithm. Noninferiority was determined at a margin of 4 percentage points.

A total of 607 participants underwent randomization; 304 were assigned to the ISL/LEN group and 303 to the B/F/TAF group. A total of 21% of the participants were women, 31% were Black, 26% were Hispanic or Latine, and 15% were 65 years of age or older. At week 48, an HIV-1 RNA level of 50 copies per milliliter or higher was reported in no participants in the ISL/LEN group and 1 (0.3%) in the B/F/TAF group (difference, -0.3 percentage points; 95.002% confidence interval [CI], -1.4 to 0.8); an HIV-1 RNA level of less than 50 copies per milliliter was reported in 284 (93.4%) and 280 (92.4%), respectively (difference, 1.0 percentage point, 95% CI, -3.2 to 5.2). The mean change in the CD4+ T-cell count at week 48 was -10 cells per microliter with ISL/LEN and -18 cells per microliter with B/F/TAF (least-squares mean difference, 12 cells per microliter; 95% CI, -16 to 39). The trial regimen was discontinued owing to adverse events in 6 participants (2.0%) in the ISL/LEN group and 5 (1.7%) in the B/F/TAF group; serious adverse events occurred in 16 (5.3%) and 14 (4.6%), respectively.

Among persons with virologically suppressed HIV-1, once-weekly oral ISL/LEN was noninferior to once-daily B/F/TAF in maintaining HIV viral load suppression. (Funded by Gilead Sciences and Merck Sharp and Dohme; ISLEND-1 ClinicalTrials.gov number, NCT06630286.).