Merck announces results from Phase 3 trial evaluating doravirine/islatravir

RAHWAY, N.J., November 19, 2025 — Merck (NYSE: MRK), known as MSD outside of the United States and Canada, today announced topline results from the pivotal double-blind Phase 3 trial of the investigational, once-daily, oral, two-drug, single-tablet regimen of doravirine/islatravir [DOR/ISL (100 mg/0.25 mg)] in adults with HIV-1 infection who had not previously received antiretroviral treatment (treatment-naïve) (MK-8591A-053). The success criterion for the primary efficacy hypothesis, as measured by the percentage of participants with HIV-1 RNA levels <50 copies/mL at Week 48, was met, with DOR/ISL demonstrating non-inferiority to once-daily oral bictegravir/emtricitabine/tenofovir alafenamide [BIC/FTC/TAF (50 mg/200 mg/25 mg)]. The primary safety objective of the trial was also met, with the safety profile of DOR/ISL being comparable to BIC/FTC/TAF.

The company is planning to present detailed findings from this trial at a future scientific congress and to submit applications including these data to health authorities. The U.S. Food and Drug Administration (FDA) accepted the New Drug Application (NDA) for DOR/ISL for the treatment of HIV-1 infection in adults to replace the current antiretroviral regimen in those who are virologically-suppressed on a stable antiretroviral regimen and has set a target action date of April 28, 2026, for the application under the Prescription Drug User Fee Act (PDUFA). In the U.S., doravirine is approved for the treatment of adults with HIV-1 in combination with other antiretrovirals as a single agent (PIFELTRO) and a component of a single-tablet regimen [DELSTRIGO; doravirine, lamivudine, and tenofovir disoproxil fumarate (DOR/3TC/TDF)].

Read the full company press release here.