The U.S. Food and Drug Administration has cleared Idvynso, a once-daily single-tablet regimen from Merck that pairs doravirine with islatravir. This approval specifically covers adults living with HIV-1 who are already virologically suppressed—commonly defined as having HIV-1 RNA below 50 copies/mL—and who want to switch from an effective antiretroviral regimen. Clinicians and patients often weigh long-term tolerability, drug–drug interactions, and cumulative toxicities when adapting maintenance therapy; Idvynso introduces a distinct option that is both non-INSTI and tenofovir-free.
Because the authorization is for people who have stable viral suppression and no known resistance to doravirine, Idvynso is presented as a maintenance strategy rather than a first-line initiation choice. The tablet contains 100 mg doravirine and 0.25 mg islatravir. Availability was announced to begin on May 11 in U.S. pharmacies, and healthcare teams will need to consider prior treatment history, comorbidities, and resistance testing when discussing switching to this two-drug alternative.
What Idvynso is and how it works
At its core, Idvynso is a two-drug antiretroviral regimen that departs from the increasingly dominant integrase inhibitor class. Doravirine is an established non-nucleoside reverse transcriptase inhibitor (NNRTI) with a known safety and interaction profile; islatravir is a next-generation nucleoside reverse transcriptase inhibitor (NRTI) that brings multiple mechanisms of action, including translocation inhibition, to the combination. Together, the two agents aim to preserve viral suppression while lowering exposure to tenofovir and avoiding integrase strand transfer inhibitors (INSTIs), which some patients or clinicians may prefer to avoid because of specific comorbidities or interaction concerns.
Composition and pharmacologic rationale
The pairing of a well-characterized NNRTI with a multi-mechanistic NRTI seeks to balance durability and simplicity. Islatravir contributes a distinctive antiviral profile that can support long-term suppression, while doravirine offers established tolerability. The result is a compact, once-daily single tablet that is marketed as an option to simplify the maintenance regimen for adults meeting the eligibility criteria.
Who is eligible to switch
Idvynso is approved for adults living with HIV-1 who are virologically suppressed on a stable antiretroviral regimen, who have no history of virologic failure, and who do not have known doravirine resistance-associated substitutions. In practice, this means candidates are those already maintaining suppression—often on integrase- or tenofovir-based regimens—who want or need to change therapy because of side effects, drug interactions with other medications, or long-term toxicity concerns.
Evidence from phase III switch trials
The FDA decision was supported by two randomized phase III studies that enrolled adults with suppressed viral loads and compared switching to Idvynso versus remaining on their baseline antiretroviral therapy. Across both Trials 051 and 052, Idvynso demonstrated non-inferior efficacy at 48 weeks, with high proportions of participants maintaining viral suppression. These studies included people switching from contemporary regimens, including bictegravir-based therapy, and measured virologic outcomes and tolerability.
Key outcomes and tolerability
Results showed strong maintenance of suppression: one trial reported about 92% of participants staying suppressed at week 48 after switching, and another reported approximately 96%. Rates of treatment discontinuation because of adverse events were low. The most commonly observed side effects were infrequent and included diarrhea, dizziness, fatigue, abdominal distention, and headache. Overall safety and tolerability were broadly comparable with existing oral antiretroviral regimens.
Clinical positioning and practical considerations
Idvynso provides clinicians with a non-INSTI, tenofovir-free maintenance choice that can be especially valuable for older patients or those with multiple chronic conditions, where minimizing drug–drug interactions and cumulative toxicities is a priority. Because the approval is for switching individuals who are already suppressed, routine considerations include reviewing resistance history, current comedications, and patient preferences. As with any regimen change, close monitoring after the switch is recommended to detect any loss of suppression early.
Access and next steps
Merck has positioned Idvynso as an addition to its HIV portfolio and as part of a broader strategy around islatravir-based therapies. For patients and providers, the immediate next steps are to determine suitability based on individual treatment history and resistance status and to plan follow-up viral load testing after switching. With its regulatory clearance, Idvynso expands the set of tools available for long-term HIV care and gives both clinicians and people living with HIV another evidence-backed option for maintenance therapy.