The U.S. Food and Drug Administration (FDA) approved Idvynso on May 1, 2026 as a fixed-dose tablet combining 0.25 mg islatravir with 100 mg doravirine. This approval is specifically for adults living with HIV-1 who are already virologically suppressed—commonly defined as having HIV-1 RNA levels below 50 copies per mL—and who have no history of virologic treatment failure. The regimen is notable because it is a two-drug single-tablet regimen that is non-INSTI and does not include tenofovir, positioning it differently from many current maintenance therapies.
Merck, the manufacturer, plans pharmacy availability reportedly beginning May 11, 2026. The approval represents both a regulatory milestone and a practical expansion of choices for clinicians and patients seeking alternatives to multi-drug or integrase inhibitor–based strategies. Throughout this article, virologic suppression refers to sustained low viral load under a stable antiretroviral regimen, and resistance substitution denotes specific viral mutations that reduce drug susceptibility.
How Idvynso works and what makes it different
Idvynso pairs two agents with complementary actions against the virus: islatravir, a first-in-class nucleoside reverse transcriptase translocation inhibitor, and doravirine, a well-established non-nucleoside reverse transcriptase inhibitor (NNRTI). The combination acts on the reverse transcriptase enzyme through distinct mechanisms—one that interferes with translocation and another that induces structural changes—thereby blocking viral replication through dual reverse transcriptase inhibition. Because it is a non-INSTI regimen, Idvynso offers an alternative for patients who need to avoid integrase strand transfer inhibitors for clinical reasons.
Another distinguishing feature is the absence of tenofovir in the tablet, which may be relevant for people with concerns about renal function or bone density linked to tenofovir exposure. The single-tablet format simplifies dosing and supports adherence by replacing more complex regimens in appropriately selected patients. As with any regimen change, clinicians must assess prior treatment history and resistance profiles because the switch is intended only for people without known doravirine resistance and without prior virologic failures.
Clinical evidence and trial outcomes
Trials and efficacy
The approval was supported by two randomized, active-controlled clinical trials that together involved more than 700 participants and measured outcomes to 48 weeks. In comparative analyses, Idvynso met criteria for non-inferiority to established regimens. In one trial comparing Idvynso to an integrase-based single-tablet regimen, 99% of participants on Idvynso maintained viral suppression at Week 48 versus 94% on the comparator. In the second study, Idvynso maintained suppression in 96% of participants compared with 92% who continued their baseline therapy. Results were broadly consistent across demographic subgroups, including older adults, with similar effectiveness observed regardless of age, sex, or race.
Safety signals and tolerability
Overall tolerability of Idvynso resembled that of comparator regimens. Discontinuations due to adverse events were uncommon; rates reported in trials were low and similar between arms. The most frequently observed adverse reactions included diarrhea, dizziness, fatigue, and headache, generally at low single-digit percentages. Weight change on average was minimal in study participants. While the safety profile is encouraging, careful monitoring is advised when switching drugs, particularly in people with multiple comorbidities or concomitant medications.
Use considerations, contraindications, and access
Idvynso is indicated only for adults who meet specific criteria: documented virologic suppression, no history of virologic treatment failure, and no known doravirine resistance-associated substitutions. The medication is contraindicated with strong CYP3A enzyme inducers, which can lower doravirine levels, and should not be coadministered with certain other antiretrovirals such as lamivudine or emtricitabine when those combinations are clinically inappropriate. Clinicians must review drug–drug interactions carefully and confirm resistance testing or treatment history before switching.
Beyond clinical guidance, Merck has indicated support programs to assist eligible patients with insurance navigation and co-pay needs, aiming to reduce access barriers. The company is also continuing research with islatravir in other settings, including studies of once-weekly dosing strategies and prophylactic applications, which could further diversify future HIV prevention and treatment tools.
Practical next steps
For people living with HIV-1 who are curious about switching to Idvynso, the first step is a discussion with their HIV care provider to review virologic history, resistance data, current medications, and personal health priorities. If a switch is clinically appropriate, shared decision-making should guide timing, monitoring plans, and follow-up viral load testing to ensure continued suppression.