Gilead's weekly islatravir/lenacapavir met HIV suppression goal versus Biktarvy
ISLEND-1's Week 48 data, already disclosed in June, head to AIDS 2026 on July 29 as Merck and Gilead push once-weekly oral dosing against daily standards of care.
Executive Summary
- A pivotal Phase 3 trial testing whether people with suppressed HIV-1 could switch to a once-weekly oral regimen met its primary virologic endpoint against a daily standard-of-care comparator.
- The result gives Gilead and Merck's islatravir/lenacapavir collaboration clinical evidence that weekly oral dosing can hold viral suppression as well as a daily single-tablet regimen, a dosing-frequency differentiation rather than a new mechanism.
- The HIV reverse-transcriptase target space is mature and crowded, with dozens of active trials and a low historical failure rate, so the informative test here is less whether the mechanism works and more whether a weekly format holds up on durability and tolerability through Week 96.
- The full data presentation at the AIDS conference will let the field see the actual suppression rate, discontinuation pattern, and CD4 trajectory behind the topline positive readout.
The result
ISLEND-1 (NCT06630286) is a Phase 3, randomized trial comparing a switch to once-weekly oral islatravir and lenacapavir against continuing the daily single-tablet regimen bictegravir/emtricitabine/tenofovir alafenamide (BIC/FTC/TAF) in 609 virologically suppressed adults with HIV-1. The registered primary endpoint is the proportion of participants with HIV-1 RNA at or above 50 copies/mL at Week 48, measured by the FDA-defined Snapshot algorithm. That endpoint was met, and safety was described as comparable to the comparator regimen with no new safety concerns identified. Merck will present the full efficacy and safety data as an oral late-breaker at the 26th International AIDS Conference in Rio de Janeiro on July 29, 2026, alongside parallel Week 48 data from the companion ISLEND-2 trial. NCT06630286+1Study to Compare an Oral Weekly Islatravir/Lenacapavir Regimen With Bictegravir/Emtricitabine/Tenofovir Alafenamide in Virologically Suppressed People With HIV-1NCT06630286Merck to Present New Data on Daily, Weekly, and Monthly Options Across its HIV Treatment and Prevention Pipeline at AIDS 2026Jul 15, 2026
Probability of SuccessBased on the AppliedXL Probability of Success model. For more information about the methodology, read the research here.
What it tests
The trial's design is a switch study, not a treatment-naive comparison: participants had already been suppressed on BIC/FTC/TAF for at least six months before randomization. That makes the informative question one of maintenance, whether a once-weekly oral pill can hold suppression as reliably as a daily one, rather than whether the drugs can newly suppress virus. Merck's chief medical officer, Dr. Eliav Barr, framed the presentation around "the potential of once-weekly oral treatments in combination with islatravir" as the next phase of the company's HIV pipeline following the FDA approval of its once-daily doravirine/islatravir combination IDVYNSO. The registry shows the primary completion date moved twice, from June 2026 to April 2026 and finally to April 17, 2026, while enrollment held flat at 609 participants after an early increase from 600. That enrollment change sits inside the routine band the operational model tracks and does not signal distress. NCT06630286+1Study to Compare an Oral Weekly Islatravir/Lenacapavir Regimen With Bictegravir/Emtricitabine/Tenofovir Alafenamide in Virologically Suppressed People With HIV-1NCT06630286Merck to Present New Data on Daily, Weekly, and Monthly Options Across its HIV Treatment and Prevention Pipeline at AIDS 2026Jul 15, 2026
The field
HIV-1 reverse transcriptase is a mature, densely worked target: 31 active trials are underway in HIV-1 infection, and the target-indication pair carries a 7% Phase 3 termination rate across 119 trials, a low bar historically. The direct comparator set includes Gilead's own bictegravir program, Merck's doravirine and islatravir franchises, ViiV Healthcare's dolutegravir and cabotegravir, and Gilead's lenacapavir prevention studies, all sharing the same reverse-transcriptase or capsid mechanism class. Given that backdrop, the mechanism is not in question; the differentiation axis is dosing frequency and pill burden, weekly oral versus daily oral or long-acting injectable, and the bar for this readout to matter is whether suppression and tolerability hold through the longer Week 96 secondary endpoint, not just Week 48.
Readthrough
A positive weekly-dosing result reads across Gilead's second pivotal trial in the same program, ISLEND-2, which tested the same once-weekly regimen against daily standard-of-care rather than a single named comparator, and whose Week 48 data will be presented the same week. It also carries into Merck's separate islatravir-based combinations, including the once-daily doravirine/islatravir regimen IDVYNSO that the FDA already approved, and the once-weekly islatravir-ulonivirine combination reporting Week 24 data at the same conference. Each shares the islatravir backbone and tests a different partner drug or dosing interval, so the ISLEND-1 result functions as an early proof point for whether patients and prescribers will adopt weekly oral dosing broadly across that franchise. MerckMerck to Present New Data on Daily, Weekly, and Monthly Options Across its HIV Treatment and Prevention Pipeline at AIDS 2026Jul 15, 2026
This analysis was produced using AI-assisted reporting systems, AppliedXL data, and official public records. These systems undergo editorial review, quality checks, and regular audits by human experts. Errors may still occur, as with any automated system. Always consult the linked primary sources. Read our AI Editorial Policy.