Merck to present ISLEND-2 Week 48 data confirming weekly ISL/LEN met endpoint
The Phase 3 readout already showed the switch regimen held HIV-1 suppression at Week 48; AIDS 2026 delivers the full efficacy and safety data behind that result.
Executive Summary
- The primary efficacy endpoint for the once-weekly oral switch regimen has already been reported met, and the upcoming conference session will present the complete dataset behind that result.
- A once-weekly regimen that matches daily standard-of-care suppression would extend the dosing-frequency reach of an oral HIV-1 treatment beyond anything currently in Phase 3 testing.
- The trial pulled its completion timeline forward rather than slipping it, and enrollment held flat against target, both signs of a program that executed on schedule.
- The regimen sits in a field with no other Phase 3 asset at the same dosing frequency, though longer-acting injectable and oral options from rival sponsors already compete on convenience.
What's being presented
Merck said it will deliver an oral late-breaker presentation of primary Week 48 efficacy and safety data from the pivotal Phase 3 ISLEND-2 trial (NCT06630299) at the 26th International AIDS Conference in Rio de Janeiro on July 29, 2026. The trial tested a switch from daily standard-of-care antiretroviral therapy to once-weekly oral islatravir plus lenacapavir in adults already virologically suppressed on treatment, with the registered primary endpoint set as the proportion of participants with HIV-1 RNA at or above 50 copies/mL at Week 48 under the FDA-defined Snapshot algorithm. That endpoint measures whether patients lose suppression after the switch, not whether the new regimen outperforms the old one. Merck+1Merck to Present New Data on Daily, Weekly, and Monthly Options Across its HIV Treatment and Prevention Pipeline at AIDS 2026Jul 15, 2026Study to Compare an Oral Weekly Islatravir/Lenacapavir Regimen With Standard of Care in Virologically Suppressed People With HIV-1NCT06630299
Probability of SuccessBased on the AppliedXL Probability of Success model. For more information about the methodology, read the research here.
The result already in hand
Gilead disclosed on June 8, 2026 that ISLEND-2 met its primary efficacy endpoint at Week 48. A companion release on June 24, 2026 covering both ISLEND-1 and ISLEND-2, spanning 1,209 enrolled participants, reported the primary endpoint met in both trials with safety described as comparable to the comparator regimens and no new safety signal identified. ISLEND-1 tested the same weekly regimen against bictegravir/emtricitabine/tenofovir alafenamide, a fixed-dose single-tablet regimen, while ISLEND-2 used a broader daily standard-of-care comparator. The AIDS 2026 session is where the granular Week 48 numbers behind those already-announced top-line results will surface, including the secondary measures of CD4 count change and treatment discontinuation due to adverse events. Merck+1Merck to Present New Data on Daily, Weekly, and Monthly Options Across its HIV Treatment and Prevention Pipeline at AIDS 2026Jul 15, 2026Study to Compare an Oral Weekly Islatravir/Lenacapavir Regimen With Standard of Care in Virologically Suppressed People With HIV-1NCT06630299
Trial execution
ISLEND-2 enrolled toward its 600-participant target and moved to Active, not recruiting status in May 2025. Its primary completion date moved twice, first pulled forward from June 2027 to April 2026, then adjusted to April 23, 2026, a net acceleration of more than a year rather than a delay. The enrollment target held flat at 600 with no growth or reduction, which the trial's own operational benchmarks describe as within the routine band for a Phase 3 program of this design. Combined with the timeline pulled in rather than pushed out, the registry record shows a trial that ran ahead of its original schedule into its Week 48 readout. NCT06630299Study to Compare an Oral Weekly Islatravir/Lenacapavir Regimen With Standard of Care in Virologically Suppressed People With HIV-1NCT06630299
Where it sits competitively
Within the tracked landscape for HIV-1 targeting trials in HIV-1 Infection, 20 industry trials across 16 sponsors have reached a maximum phase of Phase 3, and ISLEND-2 is the only Phase 3 asset in that set. Direct comparators at earlier phases include ViiV Healthcare's VH4004280 in Phase 2 and Gilead's own emtricitabine program, already at Phase 3 as an approved standard-of-care component. Longer-acting alternatives already compete on reduced dosing burden: ViiV Healthcare's cabotegravir combined with rilpivirine is established as a long-acting injectable maintenance option, tested for durability against daily oral regimens in trials such as NCT02951052 and NCT02938520. An oral regimen dosed weekly, if the full data confirm the suppression rate already reported, would sit between daily oral pills and monthly or longer injectable dosing on the treatment-burden spectrum, a positioning distinct from both.
Sponsor context
Merck's HIV franchise has separate momentum: the company noted the recent FDA approval of IDVYNSO, a once-daily single-tablet regimen of doravirine and islatravir shown non-inferior to bictegravir/emtricitabine/tenofovir alafenamide, as the backdrop for its AIDS 2026 program. Merck also plans to present Week 24 data on a separate islatravir-plus-ulonivirine weekly regimen and Week 96 data on daily doravirine/islatravir in patients with baseline resistance mutations, positioning islatravir across multiple dosing frequencies within its own portfolio. The company will hold an HIV-focused investor event on August 3, 2026, five days after the AIDS 2026 presentation. 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.