Gilead Sciences and Merck have reported positive topline Week 48 results from two Phase 3 ISLEND studies evaluating an investigational oral once-weekly single-tablet HIV treatment regimen combining islatravir and lenacapavir. The ISLEND-1 and ISLEND-2 trials assessed islatravir 2 mg/lenacapavir 300 mg (ISL/LEN) in people with HIV who were virologically suppressed and switched from BIKTARVY (bictegravir/emtricitabine/tenofovir alafenamide) in ISLEND-1 or from standard-of-care antiretroviral regimens in ISLEND-2. The primary efficacy endpoint at Week 48 – the percentage of participants with HIV-1 RNA ≥ 50 copies/mL by the FDA snapshot algorithm – was met in both trials, with ISL/LEN demonstrating statistical non-inferiority to BIKTARVY in the double-blind ISLEND-1 study and to standard-of-care daily oral regimens in the open-label ISLEND-2 study. Across both trials, the safety profile of ISL/LEN was generally comparable to the comparator regimens, and no new safety concerns were identified.
Investigators highlighted the potential of long-acting oral therapies to reshape HIV care by reducing dosing frequency while maintaining virologic control. Gilead noted that less frequent, once-weekly oral regimens like ISL/LEN could offer people living with HIV greater flexibility and discretion in daily life. Merck emphasized that the results reflect the companies’ shared commitment to expanding treatment options, and said that, if approved, ISL/LEN could become the first once-weekly long-acting oral HIV regimen for virologically suppressed individuals.
The combination of islatravir and lenacapavir targets multiple stages of HIV-1 replication, and their potency and pharmacokinetic characteristics are designed to support once-weekly dosing in a single-tablet regimen. Gilead and Merck plan to submit the Phase 3 ISLEND-1 and ISLEND-2 data to regulatory authorities worldwide and to present detailed findings at a future scientific congress. The companies stressed that islatravir and lenacapavir in combination remain investigational and are not yet approved for use.
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