Merck, known as MSD outside of the United States and Canada, announced FDA approval of Idyvynso for the treatment of adults with HIV-1 on April 21st, 2026. Consisting of a single tablet comprising 100 mg doravirine and 0.25 mg islatravir, the treatment is indicated as a replacement for antiretroviral regimens in those who are virologically suppressed on a stable antiretroviral regimen with no history of virologic treatment failure and no known substitutions associated with resistance to doravirine.
“Idyvynso combines islatravir, a next-generation [nucleoside analog reverse transcriptase inhibitor] with multiple mechanisms of action, including translocation inhibition, with doravirine, an [non-nucleoside reverse transcriptase inhibitor] with an established efficacy and safety profile. As the only two-drug, non-[integrase strand transfer inhibitor], tenofovir-free regimen, Idyvynso expands therapeutic diversity beyond the currently available oral treatment options,” said Dr. Eliav Barr, Senior Vice President, Chief Medical Officer, Merck Research Laboratories, in a company press release. “As the health needs of adults living with HIV change over time, Idvynso gives clinicians a new choice for HIV treatment. This approval marks an important new chapter in Merck’s long-standing commitment to research and discovery for people living with HIV.”
According to the press release, FDA approval was supported by data from two randomized, active-controlled, non-inferiority Phase III trials that evaluated Idyvynso in virologically-supported adults with HIV after 48 weeks of treatment. The double-blind Trial 052 evaluated Idyvynso relative to Biktarvy (bictegravir/emtricitabine/tenofovir alafenamide; BIC/FTC/TAF), whereas the open-label Trial 051 evaluated Idyvynso relative to a baseline oral antiretroviral therapy (bART). Patients in the trials began on BIC/FTC/TAF and bART before continuing that treatment or switching to treatment with Idyvynso.
In Trial 052, researchers found that 1% of both patient populations maintained viral suppression (HIV-1 RNA of greater than 50 copies per milliliter), the primary endpoint of the study. Additionally, 92% of patients on the Idyvynso maintained viral suppression (HIV-1 RNA less than 50 copies per milliliter), a key secondary endpoint, versus 94% of the BIC/FTC/TAF patient group. In Trial 051, researchers found that 1% of participants in the Idyvynso cohort had a viral load of ≥50 copies/mL at Week 48 compared to 5% who were in the bART cohort. 96% of participants in the Idyvynso cohort maintained viral suppression compared to 92% of participants in the bART cohort.
“Advances in HIV treatment mean more people living with HIV are living longer — a remarkable achievement,” said Carl Baloney, Jr., President, CEO AIDS United, in the release. “People aging with HIV face additional health challenges, including managing multiple chronic conditions and medications at the same time. It is essential that management of HIV considers these factors in addition to virologic suppression when choosing an HIV treatment regimen.”
“Idvynso is the first non-[integrase strand transfer inhibitor], tenofovir-free, two-drug regimen to demonstrate non-inferior efficacy to standard oral antiretroviral regimens, including [BIC/FTC/TAF],” said Dr. Amy Colson, Director of Research, Community Resource Initiative, Boston, Massachusetts. “This makes Idvynso a potential alternative for people with virologically suppressed HIV who may need to switch their treatment.”
