Islatravir

IDVYNSO is a fixed-dose combination of the antiretroviral drugs doravirine and islatravir [see Microbiology (12.4) ].

• IDVYNSO™ is indicated as a complete two-drug regimen for the treatment of human immunodeficiency virus type 1 (HIV-1) infection in adults to replace the current antiretroviral regimen in those who are virologically-suppressed (HIV-1 RNA less than 50 copies/mL) on a stable antiretroviral regimen with no history of virologic treatment failure and no known substitutions associated with resistance to doravirine [see Microbiology (12.4) and Clinical Studies (14) ]. IDVYNSO is a two-drug combination of doravirine, a HIV-1 non-nucleoside reverse transcriptase inhibitor (NNRTI), and islatravir, a nucleoside analog reverse transcriptase inhibitor (NRTI), and is indicated as a complete regimen 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.ICD-10: B20

• IDVYNSO is contraindicated when co-administered with: drugs that are strong cytochrome P450 (CYP)3A enzyme inducers as significant decreases in doravirine plasma concentrations may occur, which may decrease the effectiveness of IDVYNSO [see Warnings and Precautions (5.2) , Drug Interactions (7.2) , and Clinical Pharmacology (12.3) ] . lamivudine (3TC) or emtricitabine (FTC) as significant decreases in islatravir-triphosphate (ISL-TP) concentrations may occur, which may decrease the effectiveness of IDVYNSO [see Warnings and Precautions (5.2) , Drug Interactions (7.2) and Clinical Pharmacology (12.3) ] .contraindicated

Recommended dosage: One tablet taken orally once daily with or without food in adults. ( 2.1 ) Dosage adjustment with rifabutin: Take one tablet of IDVYNSO once daily, followed by one tablet of doravirine (PIFELTRO) 100 mg approximately 12 hours after the dose of IDVYNSO. ( 2.2 ) 2.1 Recommended Dosage The recommended dosage of IDVYNSO is one tablet taken orally once daily with or without food [see Clinical Pharmacology (12.3) ] . One tablet of IDVYNSO contains 100 mg doravirine and 0.25 mg islatravir. 2.2 Dosage Adjustment with Rifabutin If IDVYNSO is co-administered with rifabutin, take one tablet of IDVYNSO once daily as recommended, followed by one tablet of doravirine (PIFELTRO) 100 mg approximately 12 hours after the dose of IDVYNSO for the duration of rifabutin co-administration [see Drug Interactions (7.2) and Clinical Pharmacology (12.3) ].

Severe skin reactions, including Stevens-Johnson syndrome (SJS)/toxic epidermal necrolysis (TEN), and Drug Rash with Eosinophilia and Systemic Symptoms (DRESS), have been reported. Discontinue IDVYNSO immediately if signs or symptoms of severe skin reactions develop. ( 5.1 ) 5.1 Skin and Hypersensitivity Reactions Severe skin reactions, including Stevens-Johnson syndrome (SJS)/toxic epidermal necrolysis (TEN), have been reported during postmarketing experience with doravirine-containing regimens [see Adverse Reactions (6.2) ] . In addition, Drug Rash with Eosinophilia and Systemic Symptoms (DRESS syndrome) was reported with IDVYNSO in a clinical trial [see Adverse Reactions (6.1) ] . Discontinue IDVYNSO, and other medications known to be associated with severe skin reactions, immediately if a painful rash with mucosal involvement, a progressive severe rash, or a rash with constitutional symptoms, eosinophilia, lymphadenopathy, or other organ involvement develops. Clinical status should be closely monitored, and appropriate therapy should be initiated. 5.2 Risk of Adverse Reactions or Loss of Virologic Response Due to Drug Interactions The concomitant use of IDVYNSO and certain other drugs may result in known or potentially significant drug interactions, some of which may lead to [see Dosage and Administration (2.2) , Contraindications (4) , Drug Interactions (7.2) , and Clinical Pharmacology (12.3) ]: Loss of therapeutic effect of IDVYNSO and possible development of resistance.

The following serious adverse reactions are described in greater detail in other sections of the labeling: Skin and Hypersensitivity Reactions [see Warnings and Precautions (5.1) ] Most common adverse reactions (incidence greater than or equal to 2%, all grades): diarrhea, dizziness, fatigue, abdominal distension, headache, and weight increased. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Merck Sharp & Dohme LLC at 1-877-888-4231 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch . 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. Adverse Reactions in Virologically-Suppressed Adults Living with HIV-1 Who Switched to IDVYNSO The safety assessment of IDVYNSO in virologically-suppressed (HIV-1 RNA less than 50 copies/mL) participants living with HIV was based on Week 48 data from two Phase 3, randomized trials, Trial 051 and Trial 052. A total of 708 participants received once-daily IDVYNSO [see Clinical Studies (14) ] . In Trial 051, an open-label trial with 551 participants, 366 participants were switched to IDVYNSO and 185 participants continued their baseline antiretroviral therapy (ART). By Week 48, 0.5% in the IDVYNSO group and 2% in the baseline ART group had adverse events leading to discontinuation of study medication.

8.1 Pregnancy Pregnancy Exposure Registry There is a pregnancy exposure registry that monitors pregnancy outcomes in individuals exposed to IDVYNSO during pregnancy. Healthcare providers are encouraged to register patients by calling the Antiretroviral Pregnancy Registry (APR) at 1-800-258-4263. Risk Summary There are insufficient human data on the use of IDVYNSO during pregnancy to inform a drug-associated risk of birth defects and miscarriage. In animal reproduction studies, no developmental effects were observed when the components of IDVYNSO were administered separately at exposures (AUC) at least 8 (doravirine) and 500 (islatravir) times the exposure at the recommended human dose (RHD) of these components in IDVYNSO (see Data .) The background rate of major birth defects is 2.7% in a U.S. reference population of the Metropolitan Atlanta Congenital Defects Program (MACDP). The rate of miscarriage is not reported in the APR. The estimated background rate of miscarriage in the clinically recognized pregnancies in the U.S. general population is 15-20%. Methodological limitations of the APR include the use of MACDP as the external comparator group. The MACDP population is not disease-specific, evaluates individuals and infants from the limited geographic area, and does not include outcomes for births that occurred at less than 20 weeks gestation.

Metabolism

Single-dose administration of one IDVYNSO tablet to healthy adult participants under fasted conditions provided comparable exposures of doravirine and islatravir to administration of a doravirine tablet (100 mg) plus an islatravir capsule (0.25 mg). No clinically significant difference in pharmacokinetics was observed between healthy participants and participants living with HIV-1.

No data are available on overdose of IDVYNSO and there is no known specific treatment for overdose with IDVYNSO. If overdose occurs, the person should be monitored, and standard supportive treatment applied as required.

• Apr 20, 2026NDANDA216964Msd

The 10 most recently updated of 30 ClinicalTrials.gov registrations naming Islatravir as an intervention. Registration is not evidence of efficacy or safety — reference crosswalk only.

• A Clinical Study of Islatravir and Ulonivirine for People With HIV-1 Who Have Not Been Treated Before (MK-8591B-062)
  Recruiting · Phase 2 · Phase 3 · Interventional · 570 enrolled · Merck Sharp & Dohme LLC
  NCT07266831updated 2026-06-08
• Study of Doravirine/Islatravir (DOR/ISL 100 mg/0.75 mg) to Evaluate the Antiretroviral Activity, Safety, and Tolerability in Treatment-Naïve Participants With Human Immunodeficiency Virus Type 1 (HIV-1) Infection (MK-8591A-020)
  Completed · Phase 3 · Interventional · 599 enrolled · Merck Sharp & Dohme LLC
  NCT04233879updated 2026-06-03
• Study to Compare an Oral Weekly Islatravir/Lenacapavir Regimen With Standard of Care in Virologically Suppressed People With HIV-1
  Active not recruiting · Phase 3 · Interventional · 600 enrolled · Gilead Sciences
  NCT06630299updated 2026-05-29
• Oral Islatravir (MK-8591) Once-Monthly as Preexposure Prophylaxis (PrEP) in Men and Transgender Women Who Are at High Risk for HIV-1 Infection (MK-8591-024)
  Terminated · Phase 3 · Interventional · 494 enrolled · Merck Sharp & Dohme LLC
  NCT04652700updated 2026-05-05
• Study to Compare an Oral Weekly Islatravir/Lenacapavir Regimen With Bictegravir/Emtricitabine/Tenofovir Alafenamide in Virologically Suppressed People With HIV-1
  Active not recruiting · Phase 3 · Interventional · 609 enrolled · Gilead Sciences
  NCT06630286updated 2026-04-30
• Switch to Doravirine/Islatravir (DOR/ISL) in Human Immunodeficiency Virus 1 (HIV-1) Participants Treated With Bictegravir/Emtricitabine/Tenofovir Alafenamide (BIC/FTC/TAF) (MK-8591A-018)
  Completed · Phase 3 · Interventional · 643 enrolled · Merck Sharp & Dohme LLC
  NCT04223791updated 2026-03-27
• A Study of Doravirine/Islatravir in Healthy Lactating Females (MK-8591A-061)
  Completed · Phase 1 · Interventional · 12 enrolled · Merck Sharp & Dohme LLC
  NCT07086079updated 2026-02-20
• Safety and Efficacy of a Switch to Doravirine/Islatravir in Participants With HIV-1 (MK-8591A-017)
  Completed · Phase 3 · Interventional · 672 enrolled · Merck Sharp & Dohme LLC
  NCT04223778updated 2026-02-18
• Oral ISL QM as PrEP in Cisgender Women at High Risk for HIV-1 Infection (MK-8591-022)
  Terminated · Phase 3 · Interventional · 730 enrolled · Merck Sharp & Dohme LLC
  NCT04644029updated 2026-02-04
• Study Evaluating the Safety and Efficacy of Islatravir in Combination With Lenacapavir in Virologically Suppressed People With HIV
  Active not recruiting · Phase 2 · Interventional · 142 enrolled · Gilead Sciences
  NCT05052996updated 2026-02-04

Frequently asked questions

How does Islatravir work?

IDVYNSO is a fixed-dose combination of the antiretroviral drugs doravirine and islatravir [see Microbiology (12.4) ].

What is Islatravir used for?

According to FDA labeling, Islatravir carries indications including: IDVYNSO™ is indicated as a complete two-drug regimen for the treatment of human immunodeficiency virus type 1 (HIV-1) infection in adults to replace the current antiretroviral regimen in those who are virologically-suppressed (HIV-1 RNA less than 50 copies/mL) on a stable antiretroviral regimen with no history of virologic treatment failure and no known substitutions associated with resistance to doravirine [see Microbiology (12.4) and Clinical Studies (14) ]. IDVYNSO is a two-drug combination of doravirine, a HIV-1 non-nucleoside reverse transcriptase inhibitor (NNRTI), and islatravir, a nucleoside analog reverse transcriptase inhibitor (NRTI), and is indicated as a complete regimen 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.. This is a reference summary of labeled uses, not medical advice or a treatment recommendation.

What are the brand names for Islatravir?

Islatravir is marketed under brand names including Idvynso.

What are the contraindications for Islatravir?

Islatravir labeling lists contraindications including: IDVYNSO is contraindicated when co-administered with: drugs that are strong cytochrome P450 (CYP)3A enzyme inducers as significant decreases in doravirine plasma concentrations may occur, which may decrease the effectiveness of IDVYNSO [see Warnings and Precautions (5.2) , Drug Interactions (7.2) , and Clinical Pharmacology (12.3) ] . lamivudine (3TC) or emtricitabine (FTC) as significant decreases in islatravir-triphosphate (ISL-TP) concentrations may occur, which may decrease the effectiveness of IDVYNSO [see Warnings and Precautions (5.2) , Drug Interactions (7.2) and Clinical Pharmacology (12.3) ] .. Always consult the full prescribing information and a clinician.