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IDVYNSO is approved for adults with virologically suppressed HIV-1 with no history of virologic treatment failure and no known substitutions associated with resistance to doravirine
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IDVYNSO is the first and only non-INSTI, tenofovir-free, once-daily, complete two-drug regimen to demonstrate non-inferior efficacy in a head-to-head Phase 3 trial versus three-drug regimen BIKTARVY®i (BIC/FTC/TAF)
April 21, 2026--RAHWAY, N.J.--(BUSINESS WIRE)-- Merck (NYSE: MRK), known as MSD outside of the United States and Canada, announced today that the U.S. Food and Drug Administration (FDA) approved IDVYNSO™, a new, two-drug single-tablet regimen of 100 mg doravirine and 0.25 mg islatravir, for the treatment of HIV-1 infection in adults to replace the current antiretroviral regimen in those who are virologically suppressed (HIV-1 RNA less than 50 copies per mL) on a stable antiretroviral regimen with no history of virologic treatment failure and no known substitutions associated with resistance to doravirine. IDVYNSO is contraindicated when co-administered with drugs that are strong cytochrome P450 (CYP)3A enzyme inducers and lamivudine (3TC) or emtricitabine (FTC). Co-administration with these drugs may decrease the effectiveness of IDVYNSO. See additional selected safety information on the following pages. IDVYNSO (pronounced ihd-VIHN-soh) will be available in pharmacies after May 11.
“Advances in HIV treatment mean more people living with HIV are living longer — a remarkable achievement,” said Carl Baloney, Jr., president and chief executive officer of AIDS United. “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 combines islatravir, a next-generation NRTI with multiple mechanisms of action, including translocation inhibition, with doravirine, an NNRTI with an established efficacy and safety profile. As the only two-drug, non-INSTI, tenofovir-free regimen, IDVYNSO expands therapeutic diversity beyond the currently available oral treatment options,” said Dr. Eliav Barr, senior vice president and chief medical officer, Merck Research Laboratories. “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.”
IDVYNSO is a complete regimen; co-administration with other antiretroviral medications for treatment of HIV-1 infection is not recommended. Severe skin reactions, including Stevens-Johnson syndrome/toxic epidermal necrolysis, have been reported with doravirine-containing regimens. Drug Rash with Eosinophilia and Systemic Symptoms was reported with IDVYNSO. Concomitant use of IDVYNSO and certain other drugs may result in known or potentially significant drug interactions, some of which may lead to loss of therapeutic effect of IDVYNSO and possible development of resistance, or possible clinically significant adverse reactions from greater exposures of a component of IDVYNSO. See additional selected safety information on the following pages.
“IDVYNSO is the first non-INSTI, tenofovir-free, two-drug regimen to demonstrate non-inferior efficacy to standard oral antiretroviral regimens, including BIKTARVY. This makes IDVYNSO a potential alternative for people with virologically suppressed HIV who may need to switch their treatment,” said Dr. Amy Colson, director of research at Community Resource Initiative, Boston, Massachusetts.
Phase 3 studies supporting approval of IDVYNSO
The efficacy and safety of IDVYNSO is supported by Week 48 data from two randomized, active-controlled, non-inferiority trials [Trial 052 (NCT05630755) and Trial 051 (NCT05631093)] in virologically-suppressed (HIV-1 RNA less than 50 copies per mL) adults living with HIV. Participants must have been stably suppressed on their baseline regimen for at least 3 months prior to trial entry and had no history of treatment failure. Across the two trials, a total of 708 participants received once-daily IDVYNSO; of these, 81 (11%) participants were aged 65 years and older, including 10 (1%) aged 75 years and older.
In the double-blind Trial 052, participants were switched from BIKTARVY [bictegravir/emtricitabine/tenofovir alafenamide (BIC/FTC/TAF)] to IDVYNSO. A total of 513 participants were randomized (2:1) and were switched to once-daily IDVYNSO (n=342) or remained on BIC/FTC/TAF (n=171). At baseline, participants had a mean age of 48 years (range: 19 to 77), 21% of participants were female, 61% were White, 31% were Black/African American, and 6% were Asian. A total of 23% identified as Hispanic/Latino.
In the open-label Trial 051, participants were switched from an oral ART (antiretroviral therapy) regimen to IDVYNSO. A total of 551 participants were randomized (2:1) and were switched to once-daily IDVYNSO (n=366) or remained on their baseline ART (bART) (n=185). Randomization was stratified by bART. At baseline, participants had a mean age of 50 years (range: 18 to 83), 40% of participants were female, 39% were White, 45% were Black/African American, and 5% were Asian. A total of 15% identified as Hispanic/Latino. At enrollment, 64% of the participants were receiving integrase strand transfer inhibitor (INSTI)-based regimens, 5% protease inhibitor (PI)-based regimens (including combinations with INSTI), and 30% were receiving other regimens.
Efficacy profile of IDVYNSO
IDVYNSO was non-inferior to BIC/FTC/TAF (in Trial 052) and bART (in Trial 051) as assessed by the proportion of participants with HIV-1 RNA ≥50 copies/mL at Week 48.
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In the double-blind Trial 052, results for the primary endpoint (HIV-1 RNA ≥50 copies/mL) showed that 1% of participants who were switched to IDVYNSO (n=342) had a viral load of ≥50 copies/mL at Week 48, compared to 1% who continued on BIC/FTC/TAF (n=171; treatment difference 0.9%, 95% CI, -1.9%, 2.9%). At Week 48, results from the secondary endpoint showed that 92% of participants who switched to IDVYNSO maintained viral suppression (HIV-1 RNA <50 copies/mL) compared to 94% of participants who continued receiving BIC/FTC/TAF.
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In the open-label Trial 051, results for the primary endpoint (HIV-1 RNA ≥50 copies/mL) showed that 1% of participants who were switched to IDVYNSO (n=366) had a viral load of ≥50 copies/mL at Week 48, compared to 5% who continued on bART (n=185; treatment difference -3.6%, 95% CI, -7.8%, -0.8%). At Week 48, results from the secondary endpoint showed that 96% of participants who switched to IDVYNSO maintained viral suppression (HIV-1 RNA <50 copies/mL) compared to 92% of participants who continued on bART.
In both trials, treatment outcomes between treatment groups were similar across subgroups by age, sex and race, and in Trial 051, also by bART regimens. In participants aged 65 years and older who received IDVYNSO in both trials, no overall differences in safety or effectiveness were observed between these participants and younger participants, but greater sensitivity of some older individuals cannot be ruled out.
About IDVYNSO
IDVYNSO is a fixed-dose combination of two medicines, doravirine with islatravir. Doravirine is a non-nucleoside reverse transcriptase inhibitor (NNRTI) that inhibits HIV-1 replication by non-competitive inhibition of HIV-1 reverse transcriptase. Islatravir is a potent, next-generation nucleoside analog reverse transcriptase inhibitor (NRTI) that blocks HIV-1 replication by multiple mechanisms including:
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inhibition of reverse transcriptase translocation, resulting in immediate chain termination, and
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induction of structural changes in the viral DNA (delayed chain termination).
Merck’s Commitment to HIV
For 40 years, Merck has been committed to scientific research and discovery in HIV leading to scientific breakthroughs that have helped change HIV treatment. Our work has helped pioneer the development of new options across multiple drug classes to help those impacted by HIV. Today, we are developing a series of antiviral options designed to help people manage HIV and protect people from HIV. We are researching for real life and want to ensure people are not defined by HIV. Our work focuses on transformational innovations, collaborations with others in the global HIV community and access initiatives aimed at helping to end the HIV epidemic for everyone.
About Merck’s HIV research
Islatravir is under evaluation in multiple ongoing early and late-stage clinical trials in combination with other antiretrovirals for potential once-weekly treatments for HIV-1, with islatravir serving as the anchor medicine in these two-drug regimens. Islatravir in combination with Gilead’s lenacapavir is in Phase 3 development as a novel oral once-weekly treatment for HIV-1 [ISLEND-1 (NCT06630286) and ISLEND-2 (NCT06630299)], and islatravir in combination with our company’s investigational non-nucleoside reverse transcriptase inhibitor (NNRTI) ulonivirine (MK-8507) is in Phase 2b development [MK-8591B-060 (NCT06891066) and MK-8591B-062 (NCT07266831)] as an oral once-weekly treatment.
MK-8527 is the company’s investigational, novel, once-monthly oral candidate for pre-exposure prophylaxis (PrEP) for HIV-1. In collaboration with the Gates Foundation, the Phase 3 EXPrESSIVE-10 trial (MK-8527-010, NCT07071623) is evaluating the safety and efficacy of MK-8527 as PrEP to reduce the risk of sexually acquired HIV-1 infection among women and adolescent girls in sub-Saharan Africa. The Phase 3 EXPrESSIVE-11 trial (MK-8527-011, NCT07044297) in 16 countries is evaluating the safety and efficacy of MK-8527 as PrEP to reduce the risk of sexually acquired HIV-1 infection among people likely to be exposed to HIV-1. Both trials are now enrolling.
For an overview of Merck’s HIV treatment and prevention clinical development program, please click here.
About Merck
At Merck, known as MSD outside of the United States and Canada, we are unified around our purpose: We use the power of leading-edge science to save and improve lives around the world. For more than 130 years, we have brought hope to humanity through the development of important medicines and vaccines. We aspire to be the premier research-intensive biopharmaceutical company in the world – and today, we are at the forefront of research to deliver innovative health solutions that advance the prevention and treatment of diseases in people and animals. We foster a diverse and inclusive global workforce and operate responsibly every day to enable a safe, sustainable and healthy future for all people and communities.
i IDVYNSO™ is a trademark of Merck & Co., Inc. BIKTARVY is a registered trademark of Gilead Sciences Ireland UC.