The U.S. Food and Drug Administration’s approval of Idvynso (doravirine and islatravir, or DOR/ISL) marks a turning point in HIV treatment, offering the first integrase strand transfer inhibitor (INSTI)-free, two-drug regimen for adults with virologically suppressed HIV-1. The once-daily pill, approved by the FDA on April 21, 2026, is designed to simplify treatment for those already achieving viral suppression, potentially reducing pill burden and improving adherence while maintaining durable viral control.
For decades, standard HIV treatment has relied on three-drug regimens, often including an INSTI—a class of drugs central to modern antiretroviral therapy (ART). The approval of DOR/ISL introduces a new paradigm: a two-drug combination that does not include an INSTI, yet demonstrates non-inferior efficacy and a favorable safety profile compared to established three-drug regimens. This shift could broaden treatment options for patients seeking simpler, more tolerable therapies.
Dr. Amy Colson, MD, MPH, an infectious disease consultant and Research Director at AccessHealth MA, specializes in HIV and hepatitis C care and has been at the forefront of interpreting the clinical implications of this approval. “The introduction of DOR/ISL is a significant milestone,” she notes. “It provides a much-needed alternative for patients who are stable on their current regimen but may be looking for a simpler, potentially better-tolerated option.”
DOR/ISL’s approval follows Phase 3 clinical trials, including MK-8591A-051 and MK-8591A-052, which demonstrated that the regimen maintained HIV-1 viral suppression at Week 48, comparable to bictegravir/emtricitabine/tenofovir alafenamide (BIC/FTC/TAF), a widely used three-drug regimen. The most common adverse reactions reported were generally mild, and the regimen showed a similar safety profile to the comparator.
How DOR/ISL Works and What the Data Show
DOR/ISL combines doravirine, a non-nucleoside reverse transcriptase inhibitor (NNRTI), with islatravir, a novel nucleoside reverse transcriptase translocation inhibitor (NRTTI). Unlike traditional NRTIs, islatravir does not require phosphorylation to become active, which may contribute to its favorable resistance profile and reduced risk of mitochondrial toxicity. This mechanism allows for a two-drug regimen that avoids the need for an INSTI, addressing a long-standing goal in HIV treatment simplification.
In the pivotal trials, DOR/ISL met its primary endpoint of non-inferiority for maintaining viral suppression (HIV-1 RNA less than 50 copies/mL) through 48 weeks. The regimen also showed a low incidence of resistance-associated substitutions, suggesting durable efficacy over time. These results are particularly promising for patients who may experience side effects or drug interactions with current three-drug regimens.
Who Stands to Gain and the Evolving Treatment Landscape
DOR/ISL is approved for adults with virologically suppressed HIV-1 who are on a stable antiretroviral regimen without prior treatment failure or resistance to doravirine. This includes patients who have achieved and maintained viral suppression for at least six months, according to the FDA’s guidance. The approval expands the toolkit for clinicians, who can now offer a simpler, once-daily option to those who may be interested in reducing pill count or managing side effects from current therapies.
The HIV treatment landscape has evolved rapidly in recent years, with a growing emphasis on patient-centered care and treatment simplification. The introduction of DOR/ISL aligns with this trend, offering a new option alongside other two-drug regimens like lenacapavir/GS-6207 (Sunlenca) and bictegravir/emtricitabine/tenofovir alafenamide. However, DOR/ISL distinguishes itself by being the first INSTI-free two-drug regimen approved for this indication.
Practical Considerations for Patients and Providers
For patients considering a switch to DOR/ISL, the FDA recommends consulting with a healthcare provider to ensure the regimen is appropriate based on individual medical history, current treatment, and resistance profile. The drug is available as a single-tablet, once-daily formulation, simplifying dosing and potentially improving adherence. Common adverse reactions reported in trials included headache, diarrhea, and nausea, though these were generally mild to moderate in severity.
Providers should also be mindful of potential drug interactions, particularly with medications metabolized by the liver enzymes CYP3A and CYP2C19. Merck, the manufacturer, provides detailed prescribing information to guide clinicians on managing these interactions.
| Parameter | DOR/ISL (%) | BIC/FTC/TAF (%) |
|---|---|---|
| HIV-1 RNA <50 copies/mL | 89.5% | 88.7% |
| Treatment-emergent resistance | Low incidence | Low incidence |
| Discontinuation due to adverse events | 2.4% | 2.7% |
What’s Next for DOR/ISL and HIV Treatment
The approval of DOR/ISL opens new avenues for research and clinical practice, particularly in exploring its long-term efficacy and safety, as well as its potential role in initial treatment regimens. Merck has announced plans to further investigate DOR/ISL in additional populations, including those with hepatitis B or C co-infection, and in treatment-naïve patients. The next milestone will be the presentation of additional real-world data and long-term follow-up results from ongoing trials.
For now, the focus remains on integrating DOR/ISL into clinical practice, ensuring equitable access, and continuing to advance the goal of HIV treatment simplification. As Dr. Colson observes, “This approval is just the beginning. The field is moving toward regimens that are not only effective but also easier to take, with fewer side effects. DOR/ISL represents a step in that direction, and we can expect to see more innovations in the coming years.”
Disclaimer: This article is for informational purposes only and is not intended as medical advice. Always consult with a healthcare provider for personalized guidance regarding HIV treatment options.
Have questions about how DOR/ISL might fit into your treatment plan? Share your thoughts or experiences in the comments below, or connect with an HIV specialist for personalized advice.
