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MK-8591A

Phase 3

HIV-1 Infection | Small molecule | Infectious Disease |Merck & Company, Inc.|Last Updated: Dec 23, 2025

Success Probability
Approval Probability 71%
TA Base Rate26%
Adjusted LOA41%
ML RiskLOW_RISK
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Market & Valuation
rNPV $3.2B
Market Size $9.4B
Revenue Basis $1.6B
Competitors 6
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Trial Design
UNCONTROLLEDBiomarker
Total Trials1
Total Enrollment2,000
FDA Designations
No designations recorded
Clinical Trials (1)
NCT IDTitlePhaseStatusEnrollmentVelocityDesignStartCompletionLast UpdatedSitesCountries
NCT04776252Open-label, Follow-up of Doravirine/Islatravir (DOR/ISL 100 mg/0.75mg) for Participants With Human Immunodeficiency Virus-1 (HIV-1) Infection (MK-8591A-033)PHASE3 ACTIVE NOT_RECRUITING 2,000Sep 15, 2021May 29, 2029Dec 23, 202593 United States, Australia +14
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Study Endpoints
Primary Endpoints
Participants with serious adverse events (SAEs)
Up to Week 198

Percentage of participants with serious adverse events (SAEs)

Participants who discontinued due to an adverse event (AE)
Up to Week 192

Percentage of participants who discontinued study treatment due to an AE.

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Study Design & Arms
AllocationNA
MaskingNONE
ModelSINGLE_GROUP
PurposeTREATMENT
Treatment Arms
ArmTypeDescription
MK-8591AEXPERIMENTALFixed dose combination (FDC) tablet of 100 mg doravirine, 0.75 mg islatravir taken orally, once daily for up to 192 weeks.
Interventions
NameTypeDescription
MK-8591ADRUGFDC tablet of 100 mg doravirine, 0.75 mg islatravir taken orally, once daily for up to 192 weeks
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Eligibility Criteria
Age Range18 Years — N/A
SexALL
Healthy VolunteersNo
Study Sites93

Inclusion Criteria: * Is currently receiving DOR 100 mg/ISL 0.75 mg adult FDC tablet in an MSD-sponsored clinical study and has completed the last treatment visit. * Is considered by the investigator to have derived clinical benefit from receiving DOR/ISL and for whom further treatment with DOR/ISL...

Countries:United StatesAustraliaCanadaChileColombiaFranceGermanyItalyJapanNew ZealandPolandRussiaSouth AfricaSpainSwitzerlandUnited Kingdom
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Recent Changes (Last 90 Days)
LOWMay 26, 2026NCT04776252primaryCompletionDate: changed
LOWMay 24, 2026NCT04776252studyFirstPostDate: changed