Merck’s NDA for Once-Daily Doravirine/Islatravir HIV Regimen Accepted by U.S. FDA
Merck, known as MSD outside the U.S. and Canada, announced that the U.S. Food and Drug Administration (FDA) has accepted its New Drug Application (NDA) for doravirine/islatravir (DOR/ISL), an investigational once-daily, oral, two-drug regimen for adults with virologically suppressed HIV-1. The FDA set a Prescription Drug User Fee Act (PDUFA) target action date of April 28, 2026.
“Merck has been committed to HIV innovation for over 35 years,” said Dr. Eliav Barr, chief medical officer of Merck Research Laboratories. “If approved, DOR/ISL could offer a simplified treatment option for people living with HIV who face evolving health needs.”
The NDA submission is supported by Week 48 data from two Phase 3 trials:
- MK-8591A-051: This open-label study showed that DOR/ISL was non-inferior to baseline antiretroviral therapy (bART) in 551 virologically suppressed adults. The safety profile was comparable between arms.
- MK-8591A-052: A double-blind trial in 513 adults comparing DOR/ISL to bictegravir/emtricitabine/tenofovir alafenamide (BIC/FTC/TAF). DOR/ISL again met non-inferiority criteria with similar safety outcomes.
Trial data were presented at the 2025 Conference on Retroviruses and Opportunistic Infections (CROI).
About Islatravir and Merck’s HIV Pipeline
Islatravir (MK-8591), a novel nucleoside reverse transcriptase translocation inhibitor (NRTTI), is being evaluated in several clinical programs as part of both daily and once-weekly regimens. Other Phase 3 trials include studies in treatment-naïve individuals and long-term follow-up cohorts. Merck is also exploring combinations with lenacapavir (in partnership with Gilead) and its own investigational NNRTI, ulonivirine.
The company is further advancing MK-8527, a once-monthly oral NRTTI candidate for HIV-1 pre-exposure prophylaxis (PrEP).
Merck’s HIV Legacy
Merck has played a leading role in HIV treatment development for over three decades and remains focused on delivering new antiviral options for both treatment and prevention.
Current FDA-Approved HIV Therapies
Merck’s PIFELTRO® (doravirine) and DELSTRIGO® (a combination of doravirine, lamivudine, and tenofovir disoproxil fumarate) are approved in the U.S. for use in adults who are either treatment-naïve or virologically suppressed, with no history of resistance.
