FDA approves Merck’s once-daily HIV pill for stable patients

The Food and Drug Administration approved Merck’s once-daily HIV pill for a narrow group of adults already doing well on treatment, giving doctors a new switch option rather than a brand-new start for everyone. The tablet, sold as IDVYNSO, combines 100 mg of doravirine and 0.25 mg of islatravir and is cleared only as a replacement for a current antiretroviral regimen in adults with HIV-1 infection.

The label sets a tight bar for use. Patients must be virologically suppressed, with HIV-1 RNA below 50 copies per mL, on a stable regimen, with no history of virologic treatment failure and no known resistance substitutions linked to doravirine. The product is described as a complete regimen, and co-administration with other antiretroviral medications is not recommended. In practical terms, the approval is aimed at maintenance therapy, not at people starting HIV treatment for the first time.

For patients, the main appeal is simplification. IDVYNSO gives Merck another once-daily oral option in a field that increasingly rewards convenience, especially for people living with long-term therapy and the burden of daily adherence. Merck said the regimen is the first and only non-INSTI, tenofovir-free, once-daily complete two-drug regimen to show non-inferior efficacy in a head-to-head Phase 3 trial against Gilead Sciences’ Biktarvy. The company also said its switch study maintained virologic suppression through Week 96, while a treatment-naïve study showed non-inferiority and a similar safety profile at Week 48.

The approval also closes a long and difficult loop for islatravir, which was placed on clinical hold on December 13, 2021, after reports of decreases in total lymphocyte and CD4+ T-cell counts in some participants. Merck later restarted development at a lower dose, leading to the doravirine-islatravir combination now on the market. Doravirine was already sold in the United States as Pifeltro and as part of Delstrigo, so the new approval turns an established component of HIV treatment into a new two-drug regimen built for stable patients.

The decision comes as HIV remains a large global public health challenge. UNAIDS says 1.3 million people were newly infected in 2024, and women and girls accounted for 45% of those infections. For Merck, based in Rahway, New Jersey, the FDA action gives its HIV franchise a concrete foothold in maintenance therapy and sets up the next question for clinicians and patients alike: whether this is simply a smaller, cleaner option or a meaningful advance for people who need durable suppression with fewer treatment demands.