Merck announced new clinical results from two pivotal Phase 3 trials of its investigational once-daily oral HIV therapy, a two-drug regimen combining doravirine and islatravir (DOR/ISL), in adults with virologically suppressed HIV-1 infection. The data, presented at the European AIDS Conference in Paris, demonstrate that switching to DOR/ISL from standard three-drug regimens maintained viral suppression while yielding minimal changes in weight and body composition as well as no clinically meaningful impact on fasting lipids and insulin resistance metrics.
The double-blind MK-8591A-052 trial enrolled 513 adults, randomizing them to either switch to DOR/ISL or continue their previous therapy (bictegravir/emtricitabine/tenofovir alafenamide). After 48 weeks, both groups showed very small changes in weight and body composition, with no substantial differences observed between treatment arms. Rates of adverse events and discontinuations were similar, confirming DOR/ISL's favorable safety profile. Comparable findings were observed in the open-label MK-8591A-051 study, which allowed participants on different antiretroviral therapies to switch to DOR/ISL.
Notably, the pooled DOR/ISL groups showed minimal variation in measures of total cholesterol, HDL, LDL, triglycerides, and insulin resistance. These indicators are key for cardiovascular risk management in patients on lifelong HIV treatment. The FDA accepted Merck’s New Drug Application for DOR/ISL earlier this year, with an expected decision date of April 28, 2026 under the Prescription Drug User Fee Act. If approved, DOR/ISL could offer people living with HIV a convenient, effective and metabolically neutral treatment option.
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