A Clinical Study of Islatravir and Ulonivirine for People With HIV-1 Who Have Not Been Treated Before (MK-8591B-062)

May 15, 2026 updated by: Merck Sharp & Dohme LLC

A Phase 2/3, Randomized, Active-Controlled, Open-Label (Phase 2) and Double-Blind (Phase 3) Study to Evaluate the Antiretroviral Activity, Safety, and Tolerability of Islatravir (ISL) and Ulonivirine (ULO) Once Weekly Compared With Bictegravir/Emtricitabine/Tenofovir Alafenamide (BIC/FTC/TAF) Once Daily in Treatment-Naïve Adult Participants Living With HIV-1

Researchers are looking for new ways to treat HIV-1 (Human Immunodeficiency Virus Type 1). The usual (standard) treatment for HIV-1 is antiretroviral therapy (ART), which includes taking medicines to lower the amount of HIV-1 in the body. Standard ART helps people live longer, but people must take up to 3 medicines up to twice a day. Standard ART may also cause other health problems. Researchers want to know if a study ART works as well as a standard ART to treat HIV-1. The study ART combines 2 medicines, islatravir and ulonivirine, and is taken once a week. The goals of this study are to learn: 1) If the study ART works as well as a standard ART to treat HIV-1, and 2) About the safety of the study ART and if people tolerate it compared to a standard ART.

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Study Type

Interventional

Enrollment (Estimated)

570

Phase

  • Phase 2
  • Phase 3

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Locations

  • Argentina
    • Buenos Aires
      • CABA, Buenos Aires, Argentina, C1427CEA
        • Recruiting
        • Fundación Huesped ( Site 3100)
        • Contact:
          • Study Coordinator
          • Phone Number: +541121209999
      • Caba, Buenos Aires, Argentina, C1425AGC
        • Recruiting
        • Centro Medico Dra. Laura Maffei- Investigacion Clinica Aplicada ( Site 3102)
        • Contact:
          • Study Coordinator
          • Phone Number: +5491141639539
      • Mar del Plata, Buenos Aires, Argentina, B7600FZN
        • Recruiting
        • Instituto de Investigaciones Clinicas Mar del Plata ( Site 3103)
        • Contact:
          • Study Coordinator
          • Phone Number: +5492234365218
    • Buenos Aires F.D.
      • Buenos Aires, Buenos Aires F.D., Argentina, C1405CKC
        • Recruiting
        • Fundación IDEAA ( Site 3101)
        • Contact:
          • Study Coordinator
          • Phone Number: +5491161835390
    • Santa Fe Province
      • Rosario, Santa Fe Province, Argentina, S2000PBJ
        • Recruiting
        • Instituto CAICI SRL ( Site 3106)
        • Contact:
          • Study Coordinator
          • Phone Number: +543414248045
    • Tucumán Province
      • San Miguel de Tucumán, Tucumán Province, Argentina, T4000IHE
        • Recruiting
        • Clínica Mayo de Urgencias Médicas Cruz Blanca S.R.L ( Site 3105)
        • Contact:
          • Study Coordinator
          • Phone Number: +5403814502600
  • Canada
    • British Columbia
      • Vancouver, British Columbia, Canada, V6Z 2T1
        • Recruiting
        • Spectrum Health ( Site 3307)
        • Contact:
          • Study Coordinator
          • Phone Number: 6046853747
    • Quebec
      • Montreal, Quebec, Canada, H2L 4P9
        • Recruiting
        • Gestion clinique médicale l'Actuel ( Site 3303)
        • Contact:
          • Study Coordinator
          • Phone Number: 5145243642x2271
  • Chile
    • Region M. de Santiago
      • Santiago, Region M. de Santiago, Chile, 7500710
        • Recruiting
        • Biomedica Research Group ( Site 4201)
        • Contact:
          • Study Coordinator
          • Phone Number: 56222045686
      • Santiago, Region M. de Santiago, Chile, 7620157
        • Recruiting
        • Clínica Universidad de Los Andes ( Site 4207)
        • Contact:
          • Study Coordinator
          • Phone Number: 56226183123
      • Santiago, Region M. de Santiago, Chile, 7770086
        • Recruiting
        • Espacio Eme ( Site 4202)
        • Contact:
          • Study Coordinator
          • Phone Number: +56990008060
  • France
    • Gironde
      • Bordeaux, Gironde, France, 33000
        • Recruiting
        • Bordeaux University Hospital - Pellegrin ( Site 3605)
        • Contact:
          • Study Coordinator
          • Phone Number: +33556795536
    • Haute-Garonne
      • Toulouse, Haute-Garonne, France, 31059
        • Recruiting
        • Centre Hospitalier Universitaire de Toulouse - Hôpital Purpan ( Site 3608)
        • Contact:
          • Study Coordinator
          • Phone Number: +33561776800
    • Pays de la Loire Region
      • Nantes, Pays de la Loire Region, France, 44093
        • Recruiting
        • Centre Hospitalier Universitaire de Nantes - L' Hopital l'hôtel-Dieu-Infectious Disease ( Site 3606)
        • Contact:
          • Study Coordinator
          • Phone Number: +33240083109
    • Rhone
      • Lyon, Rhone, France, 69317
        • Recruiting
        • HOPITAL DE LA CROIX ROUSSE ( Site 3613)
        • Contact:
          • Study Coordinator
          • Phone Number: +33472071107
    • Île-de-France Region
      • Bobigny, Île-de-France Region, France, 93000
        • Recruiting
        • Hôpital Avicenne ( Site 3602)
        • Contact:
          • Study Coordinator
          • Phone Number: +33148955421
      • Paris, Île-de-France Region, France, 75018
        • Recruiting
        • Hôpital Bichat - Claude-Bernard ( Site 3601)
        • Contact:
          • Study Coordinator
          • Phone Number: +33140257803
      • Paris, Île-de-France Region, France, 75010
        • Recruiting
        • Hôpital Saint-Louis ( Site 3600)
        • Contact:
          • Study Coordinator
          • Phone Number: +33142494852
  • Guatemala
      • Guatemala City, Guatemala, 01009
        • Recruiting
        • MEDI-K ( Site 3803)
        • Contact:
          • Study Coordinator
          • Phone Number: +50222912323
      • Guatemala City, Guatemala, 01009
        • Recruiting
        • Clínica Médica Especializada en Pediatría e Infectología Pediátrica - Dr. Mario Melgar ( Site 3801)
        • Contact:
          • Study Coordinator
          • Phone Number: +50223196600
      • Guatemala City, Guatemala, 01010
        • Recruiting
        • CELAN,S.A ( Site 3802)
        • Contact:
          • Study Coordinator
          • Phone Number: +50222968018
  • Mexico
      • Veracruz, Mexico, 91910
        • Recruiting
        • Arké SMO S.A de C.V ( Site 4505)
        • Contact:
          • Study Coordinator
          • Phone Number: +522299314102
    • Guanajuato
      • León, Guanajuato, Mexico, 37000
        • Recruiting
        • Morales Vargas Centro de Investigacion, S.C. ( Site 4502)
        • Contact:
          • Study Coordinator
          • Phone Number: 4777160714
  • South Africa
    • Free State
      • Bloemfontein, Free State, South Africa, 9301
        • Recruiting
        • Josha Research ( Site 4302)
        • Contact:
          • Study Coordinator
          • Phone Number: +27 51 412 8160
    • KwaZulu-Natal
      • Durban, KwaZulu-Natal, South Africa, 4052
        • Recruiting
        • Wentworth Hospital ( Site 4303)
        • Contact:
          • Study Coordinator
          • Phone Number: +27837471149
    • Western Cape
      • Mbekweni, Paarl, Western Cape, South Africa, 7646
        • Recruiting
        • Be Part Yoluntu Centre ( Site 4300)
        • Contact:
          • Study Coordinator
          • Phone Number: +27 21 8683990/1/2
  • Spain
      • Barcelona, Spain, 08035
        • Recruiting
        • Hospital Universitari Vall d'Hebron ( Site 3402)
        • Contact:
          • Study Coordinator
          • Phone Number: +34934894377
      • Barcelona, Spain, 08036
        • Recruiting
        • HOSPITAL CLÍNIC DE BARCELONA ( Site 3400)
        • Contact:
          • Study Coordinator
          • Phone Number: +34932275574
      • Madrid, Spain, 28041
        • Recruiting
        • Hospital Universitario 12 de Octubre ( Site 3405)
        • Contact:
          • Study Coordinator
          • Phone Number: +34917792853
      • Málaga, Spain, 29010
        • Recruiting
        • Complejo Hospitalario Virgen De La Victoria ( Site 3409)
        • Contact:
          • Study Coordinator
          • Phone Number: +34 951032594
    • Madrid, Comunidad de
      • Madrid, Madrid, Comunidad de, Spain, 28029
        • Recruiting
        • Hospital Universitario La Paz ( Site 3404)
        • Contact:
          • Study Coordinator
          • Phone Number: +34915383515
    • Valenciana, Comunitat
      • Valencia, Valenciana, Comunitat, Spain, 46014
        • Recruiting
        • Consorcio Hospital General Universitario de Valencia ( Site 3406)
        • Contact:
          • Study Coordinator
          • Phone Number: +34 963131800x437834
  • United States
    • California
      • Los Angeles, California, United States, 90036
        • Recruiting
        • Ruane Clinical Research Group, Inc. ( Site 1513)
        • Contact:
          • Study Coordinator
          • Phone Number: 323-954-0400
    • Colorado
      • Denver, Colorado, United States, 80246
        • Recruiting
        • Vivent Health ( Site 1519)
        • Contact:
          • Study Coordinator
          • Phone Number: 303-393-8050
    • District of Columbia
      • Washington D.C., District of Columbia, United States, 20032
        • Recruiting
        • Whitman-Walker Institute ( Site 1538)
        • Contact:
          • Study Coordinator
          • Phone Number: 202-207-2510
    • Florida
      • Ft. Pierce, Florida, United States, 34982
        • Recruiting
        • Midway Immunology and Research Center ( Site 1503)
        • Contact:
          • Study Coordinator
          • Phone Number: 772-595-9830
      • Miami Gardens, Florida, United States, 33055
        • Recruiting
        • CAN Community Health- Miami Gardens ( Site 1549)
        • Contact:
          • Study Coordinator
          • Phone Number: 954-955-0023
      • Orlando, Florida, United States, 32803
        • Recruiting
        • Orlando Immunology Center ( Site 1501)
        • Contact:
          • Study Coordinator
          • Phone Number: 407-374-0220
      • Sarasota, Florida, United States, 34237
        • Recruiting
        • CAN Community Health ( Site 1510)
        • Contact:
          • Study Coordinator
          • Phone Number: 941-366-0134
      • West Palm Beach, Florida, United States, 33407
        • Recruiting
        • Triple O Research Institute ( Site 1505)
        • Contact:
          • Study Coordinator
          • Phone Number: 561-855-7871
    • Georgia
      • Decatur, Georgia, United States, 30033
        • Recruiting
        • Metro Infectious Diseases Consultants L.L.C. ( Site 1509)
        • Contact:
          • Study Coordinator
          • Phone Number: 404-297-9755
      • Macon, Georgia, United States, 31201
        • Recruiting
        • Mercer university, Department of internal medicine-Clinical Research ( Site 1512)
        • Contact:
          • Study Coordinator
          • Phone Number: 478-301-5846
    • Michigan
      • Detroit, Michigan, United States, 48202
        • Recruiting
        • Henry Ford Hospital ( Site 1535)
        • Contact:
          • Study Coordinator
          • Phone Number: 313-916-2600
    • Missouri
      • Kansas City, Missouri, United States, 64111
        • Recruiting
        • KC CARE Health Center ( Site 1506)
        • Contact:
          • Study Coordinator
          • Phone Number: 816-753-5144
    • New Jersey
      • Hillsborough, New Jersey, United States, 08844
        • Recruiting
        • ID Care ( Site 1507)
        • Contact:
          • Study Coordinator
          • Phone Number: 908-281-0221
    • North Carolina
      • Charlotte, North Carolina, United States, 28204
        • Recruiting
        • Atrium Health Infectious Disease Kenilworth - Charlotte ( Site 1533)
        • Contact:
          • Study Coordinator
          • Phone Number: 704-468-3510
      • Greensboro, North Carolina, United States, 27401
        • Recruiting
        • Regional Center for Infectious Diseases ( Site 1516)
        • Contact:
          • Study Coordinator
          • Phone Number: 336-832-3275
    • Ohio
      • Columbus, Ohio, United States, 43210
        • Recruiting
        • The Ohio State University ( Site 1536)
        • Contact:
          • Study Coordinator
          • Phone Number: 614-293-8112
    • Pennsylvania
      • Philadelphia, Pennsylvania, United States, 19104
        • Recruiting
        • University of Pennsylvania Perelman School of Medicine ( Site 1508)
        • Contact:
          • Study Coordinator
          • Phone Number: 215-349-8092
    • Texas
      • Bellaire, Texas, United States, 77401
        • Recruiting
        • Saint Hope Foundation, Inc. ( Site 1504)
        • Contact:
          • Study Coordinator
          • Phone Number: 713-839-7111
      • Dallas, Texas, United States, 75208
        • Recruiting
        • Prism Health North Texas, Oak Cliff Health Center ( Site 1514)
        • Contact:
          • Study Coordinator
          • Phone Number: 214-521-5191
      • Dallas, Texas, United States, 75246
        • Recruiting
        • North Texas Infectious Diseases Consultants ( Site 1500)
        • Contact:
          • Study Coordinator
          • Phone Number: 214-276-5627
      • Fort Worth, Texas, United States, 76104
        • Recruiting
        • Texas Center for Infectious Disease Associates ( Site 1502)
        • Contact:
          • Study Coordinator
          • Phone Number: 817-348-0042
      • Longview, Texas, United States, 75605
        • Recruiting
        • DCOL Center for Clinical Research ( Site 1511)
        • Contact:
          • Study Coordinator
          • Phone Number: 903-238-8854
    • Washington
      • Seattle, Washington, United States, 98104
        • Recruiting
        • Harborview Medical Center ( Site 1526)
        • Contact:
          • Study Coordinator
          • Phone Number: 206-744-8886

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • Phase 2: Is human immunodeficiency virus type 1 (HIV-1) positive with Plasma HIV-1 ribonucleic acid (RNA) ≥500 and ≤100,000 copies/mL.
  • Phase 3: Is HIV-1 positive with Plasma HIV-1 RNA ≥500 copies/mL.
  • Phase 2: Has cluster of differentiation 4-positive (CD4+) T-cell count ≥200 cells/mm^3.
  • Is naïve to antiretroviral therapy (ART), defined as having received no prior therapy with any antiretroviral agent following a diagnosis of HIV 1 infection.

Exclusion Criteria:

  • Has human immunodeficiency virus type 2 (HIV-2) infection.
  • Has a diagnosis of an active acquired immune deficiency syndrome (AIDS)-defining opportunistic infection.
  • Has active hepatitis C virus (HCV) or active hepatitis B virus (HBV) infection.
  • Has a history of malignancy ≤5 years prior to providing documented informed consent except for adequately treated basal cell or squamous cell skin cancer, in situ cervical or in situ anal cancer, or cutaneous Kaposi's sarcoma.
  • Has prior exposure to islatravir (ISL) or ulonivirine (ULO) for any duration any time prior to Day 1.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Double

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Phase 2: ISL + ULO
Islatravir (ISL) 2mg and Ulonivirine (ULO) 200mg administered orally once weekly (qw) for 96 weeks
Drug: ISL
ISL 2 x 1 mg oral capsules administered qw for 96 weeks
Other Names:
  • MK-8591
  • islatravir
Drug: ULO
ULO 2 x 100 mg oral tablets administered qw for 96 weeks
Other Names:
  • MK-8507
  • ulonivirine
Active Comparator: Phase 2: BIC/FTC/TAF
Bictegravir/Emtricitabine/Tenofovir Alafenamide (BIC/FTC/TAF) 50/200/25 mg, administered orally once daily (qd) for 96 weeks
Drug: BIC/FTC/TAF
BIC/FTC/TAF 50/200/25 mg oral tablet administered qd for 96 weeks
Other Names:
  • BIKTARVY®
  • bictegravir/emtricitabine/tenofovir alafenamide
Experimental: Phase 3: ISL/ULO and Placebo to BIC/FTC/TAF
ISL/ULO fixed dose combination (2/200 mg), administered orally qw, and matching placebo to BIC/FTC/TAF administered orally qd for 96 weeks
Drug: Placebo for BIC/FTC/TAF
BIC/FTC/TAF-matching placebo oral tablet administered qd for 96 weeks
Drug: ISL/ULO
ISL/ULO fixed-dose combination 2 mg/200 mg oral tablet administered qw for 96 weeks
Other Names:
  • MK-8591B
Active Comparator: Phase 3: BIC/FTC/TAF and Placebo to ISL/ULO
BIC/FTC/TAF 50/200/25 mg, administered orally qd, and matching placebo to ISL/ULO administered orally qw for 96 weeks
Drug: BIC/FTC/TAF
BIC/FTC/TAF 50/200/25 mg oral tablet administered qd for 96 weeks
Other Names:
  • BIKTARVY®
  • bictegravir/emtricitabine/tenofovir alafenamide
Drug: Placebo to ISL/ULO
ISL/ULO-matching placebo oral tablets administered qw for 96 weeks

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Phase 2: Percentage of Participants With Human Immunodeficiency Virus Type 1 (HIV-1) Ribonucleic Acid (RNA) <50 Copies/mL at Week 24
Time Frame: Week 24
Plasma HIV-1 ribonucleic acid (RNA) quantification will be performed at the central laboratory using a polymerase chain reaction (PCR) assay. Percentage of participants with HIV-1 RNA <50 copies/mL will be reported at week 24.
Week 24
Phase 2: Percentage of Participants Who Experience an Adverse Event (AE) at Week 24
Time Frame: Week 24
An AE is defined as any unfavorable and unintended sign, symptom, disease, or worsening of preexisting condition temporally associated with study treatment and irrespective of causality to study treatment.
Week 24
Phase 2: Percentage of Participants Who Discontinue Study Intervention Due to an AE at Week 24
Time Frame: Week 24
An AE is defined as any unfavorable and unintended sign, symptom, disease, or worsening of preexisting condition temporally associated with study treatment and irrespective of causality to study treatment.
Week 24
Phase 3: Percentage of Participants With HIV-1 RNA <50 Copies/mL at Week 48
Time Frame: Week 48
Plasma HIV-1 RNA quantification will be performed at the central laboratory using a PCR assay. Percentage of participants with HIV-1 RNA <50 copies/mL will be reported at week 48.
Week 48
Phase 3: Percentage of Participants Who Experience an AE at Week 48
Time Frame: Week 48
An AE is defined as any unfavorable and unintended sign, symptom, disease, or worsening of preexisting condition temporally associated with study treatment and irrespective of causality to study treatment.
Week 48
Phase 3: Percentage of Participants Who Discontinue Study Intervention Due to an AE at Week 48
Time Frame: Week 48
An AE is defined as any unfavorable and unintended sign, symptom, disease, or worsening of preexisting condition temporally associated with study treatment and irrespective of causality to study treatment.
Week 48

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Phase 2: Percentage of Participants With HIV-1 RNA <50 Copies/mL at Week 48
Time Frame: Week 48
Plasma HIV-1 RNA quantification will be performed at the central laboratory using a PCR assay. Percentage of participants with HIV-1 RNA <50 copies/mL will be reported at week 48.
Week 48
Phase 2: Percentage of Participants With HIV-1 RNA <50 Copies/mL at Week 96
Time Frame: Week 96
Plasma HIV-1 RNA quantification will be performed at the central laboratory using a PCR assay. Percentage of participants with HIV-1 RNA <50 copies/mL will be reported at week 96.
Week 96
Phase 2: Percentage of Participants With HIV-1 RNA <200 Copies/mL at Week 24
Time Frame: Week 24
Plasma HIV-1 RNA quantification will be performed at the central laboratory using a PCR assay. Percentage of participants with HIV-1 RNA <200 copies/mL will be reported at week 24.
Week 24
Phase 2: Percentage of Participants With HIV-1 RNA <200 Copies/mL at Week 48
Time Frame: Week 48
Plasma HIV-1 RNA quantification will be performed at the central laboratory using a PCR assay. Percentage of participants with HIV-1 RNA <200 copies/mL will be reported at week 48.
Week 48
Phase 2: Percentage of Participants With HIV-1 RNA <200 Copies/mL at Week 96
Time Frame: Week 96
Plasma HIV-1 RNA quantification will be performed at the central laboratory using a PCR assay. Percentage of participants with HIV-1 RNA <200 copies/mL will be reported at week 96.
Week 96
Phase 2: Mean Change From Baseline in Cluster of Differentiation 4-Positive (CD4+) T-Cell Count at Week 24
Time Frame: Baseline (Day 1) and Week 24
Blood samples will be collected to measure CD4+ T-cell count. The mean change from baseline in CD4+ T-cell count will be calculated at 24 weeks.
Baseline (Day 1) and Week 24
Phase 2: Mean Change From Baseline in CD4+ T-Cell Count at Week 48
Time Frame: Baseline (Day 1) and Week 48
Blood samples will be collected to measure CD4+ T-cell count. The mean change from baseline in CD4+ T-cell count will be calculated at 48 weeks.
Baseline (Day 1) and Week 48
Phase 2: Mean Change From Baseline in CD4+ T-Cell Count at Week 96
Time Frame: Baseline (Day 1) and Week 96
Blood samples will be collected to measure CD4+ T-cell count. The mean change from baseline in CD4+ T-cell count will be calculated at 96 weeks.
Baseline (Day 1) and Week 96
Phase 2: Percentage of Participants Who Experience an AE
Time Frame: Up to approximately 102 weeks
An AE is defined as any unfavorable and unintended sign, symptom, disease, or worsening of preexisting condition temporally associated with study treatment and irrespective of causality to study treatment.
Up to approximately 102 weeks
Phase 2: Percentage of Participants Who Discontinue Study Intervention Due to an AE
Time Frame: Up to approximately 96 weeks
An AE is defined as any unfavorable and unintended sign, symptom, disease, or worsening of preexisting condition temporally associated with study treatment and irrespective of causality to study treatment.
Up to approximately 96 weeks
Phase 2: Number of Participants With Evidence of Viral Drug Resistance-Associated Substitutions at Week 24
Time Frame: Week 24
Participants who meet the definition of clinically significant confirmed viremia (CSCV) or who discontinue study intervention for another reason and have HIV-1 RNA ≥200 copies/mL at the time of discontinuation, will be assessed for development of viral drug resistance. Among such participants, those with confirmed HIV-1 RNA ≥400 copies/mL will be included in the resistance analyses set. In addition, anyone for whom available genotypic and/or phenotypic data show evidence of resistance, irrespective of viral load, will also be included in the resistance analyses set. The number of participants in each treatment group who have evidence of resistance-associated substitutions at week 24 will be presented.
Week 24
Phase 2: Number of Participants With Evidence of Viral Drug Resistance-Associated Substitutions at Week 48
Time Frame: Week 48
Participants who meet the definition of clinically significant confirmed viremia (CSCV) or who discontinue study intervention for another reason and have HIV-1 RNA ≥200 copies/mL at the time of discontinuation, will be assessed for development of viral drug resistance. Among such participants, those with confirmed HIV-1 RNA ≥400 copies/mL will be included in the resistance analyses set. In addition, anyone for whom available genotypic and/or phenotypic data show evidence of resistance, irrespective of viral load, will also be included in the resistance analyses set. The number of participants in each treatment group who have evidence of resistance-associated substitutions at week 48 will be presented.
Week 48
Phase 2: Number of Participants With Evidence of Viral Drug Resistance-Associated Substitutions at Week 96
Time Frame: Week 96
Participants who meet the definition of clinically significant confirmed viremia (CSCV) or who discontinue study intervention for another reason and have HIV-1 RNA ≥200 copies/mL at the time of discontinuation, will be assessed for development of viral drug resistance. Among such participants, those with confirmed HIV-1 RNA ≥400 copies/mL will be included in the resistance analyses set. In addition, anyone for whom available genotypic and/or phenotypic data show evidence of resistance, irrespective of viral load, will also be included in the resistance analyses set. The number of participants in each treatment group who have evidence of resistance-associated substitutions at week 96 will be presented.
Week 96
Phase 3: Percentage of Participants With HIV-1 RNA <50 Copies/mL at Week 96
Time Frame: Week 96
Plasma HIV-1 RNA quantification will be performed at the central laboratory using a PCR assay. Percentage of participants with HIV-1 RNA <50 copies/mL will be reported at week 96.
Week 96
Phase 3: Percentage of Participants With HIV-1 RNA <200 Copies/mL at Week 48
Time Frame: Week 48
Plasma HIV-1 RNA quantification will be performed at the central laboratory using a PCR assay. Percentage of participants with HIV-1 RNA <200 copies/mL will be reported at week 48.
Week 48
Phase 3: Percentage of Participants With HIV-1 RNA <200 Copies/mL at Week 96
Time Frame: Week 96
Plasma HIV-1 RNA quantification will be performed at the central laboratory using a PCR assay. Percentage of participants with HIV-1 RNA <200 copies/mL will be reported at week 96.
Week 96
Phase 3: Mean Change From Baseline in Cluster of Differentiation 4-Positive (CD4+) T-Cell Count at Week 48
Time Frame: Baseline (Day 1) and Week 48
Blood samples will be collected to measure CD4+ T-cell count. The mean change from baseline in CD4+ T-cell count will be calculated at 48 weeks.
Baseline (Day 1) and Week 48
Phase 3: Mean Change From Baseline in Cluster of Differentiation 4-Positive (CD4+) T-Cell Count at Week 96
Time Frame: Baseline (Day 1) and Week 96
Blood samples will be collected to measure CD4+ T-cell count. The mean change from baseline in CD4+ T-cell count will be calculated at 96 weeks.
Baseline (Day 1) and Week 96
Phase 3: Percentage of Participants Who Experience an AE
Time Frame: Up to approximately 102 weeks
An AE is defined as any unfavorable and unintended sign, symptom, disease, or worsening of preexisting condition temporally associated with study treatment and irrespective of causality to study treatment.
Up to approximately 102 weeks
Phase 3: Percentage of Participants Who Discontinue Study Intervention Due to an AE
Time Frame: Up to approximately 96 weeks
An AE is defined as any unfavorable and unintended sign, symptom, disease, or worsening of preexisting condition temporally associated with study treatment and irrespective of causality to study treatment.
Up to approximately 96 weeks
Phase 3: Number of Participants With Evidence of Viral Drug Resistance-Associated Substitutions at Week 48
Time Frame: Week 48
Participants who meet the definition of clinically significant confirmed viremia (CSCV) or who discontinue study intervention for another reason and have HIV-1 RNA ≥200 copies/mL at the time of discontinuation, will be assessed for development of viral drug resistance. Among such participants, those with confirmed HIV-1 RNA ≥400 copies/mL will be included in the resistance analyses set. In addition, anyone for whom available genotypic and/or phenotypic data show evidence of resistance, irrespective of viral load, will also be included in the resistance analyses set. The number of participants in each treatment group who have evidence of resistance-associated substitutions at week 48 will be presented.
Week 48
Phase 3: Number of Participants With Evidence of Viral Drug Resistance-Associated Substitutions at Week 96
Time Frame: Week 96
Participants who meet the definition of clinically significant confirmed viremia (CSCV) or who discontinue study intervention for another reason and have HIV-1 RNA ≥200 copies/mL at the time of discontinuation, will be assessed for development of viral drug resistance. Among such participants, those with confirmed HIV-1 RNA ≥400 copies/mL will be included in the resistance analyses set. In addition, anyone for whom available genotypic and/or phenotypic data show evidence of resistance, irrespective of viral load, will also be included in the resistance analyses set. The number of participants in each treatment group who have evidence of resistance-associated substitutions at week 96 will be presented.
Week 96
Phase 3: Mean Change From Baseline in Body Weight at Week 48
Time Frame: Baseline (Day 1) and Week 48
Body weight will be collected throughout the study.
Baseline (Day 1) and Week 48
Phase 3: Mean Change From Baseline in Body Weight at Week 96
Time Frame: Baseline (Day 1) and Week 96
Body weight will be collected throughout the study.
Baseline (Day 1) and Week 96

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Merck Sharp & Dohme LLC

Investigators

  • Study Director: Medical Director, Merck Sharp & Dohme LLC

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

Helpful Links

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

December 18, 2025

Primary Completion (Estimated)

March 21, 2029

Study Completion (Estimated)

April 3, 2030

Study Registration Dates

First Submitted

December 1, 2025

First Submitted That Met QC Criteria

December 1, 2025

First Posted (Actual)

December 5, 2025

Study Record Updates

Last Update Posted (Actual)

May 19, 2026

Last Update Submitted That Met QC Criteria

May 15, 2026

Last Verified

May 1, 2026

More Information

Terms related to this study

Additional Relevant MeSH Terms

Other Study ID Numbers

  • 8591B-062
  • U1111-1323-4689 (Registry Identifier: UTN)
  • 2025-522519-40 (Registry Identifier: EU CT)
  • MK-8591B-062 (Other Identifier: MSD)

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

YES

IPD Plan Description

https://trialstransparency.msdclinicaltrials.com/pdf/ProcedureAccessClinicalTrialData.pdf

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

Yes

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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