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)

Percentage of Participants With HIV-1 RNA ≥50 Copies/mL at Week 96

The Abbott RealTime PCR assay with a reliable lower limit of quantification of 40 copies/mL was used to measure the HIV-1 RNA level in blood samples obtained at each visit. Per protocol, the secondary outcome measure, percentage of participants with HIV-1 RNA ≥50 copies/mL at Week 96, is presented using the Food and Drug Administration (FDA) Snapshot missing data approach. The percentage values were rounded to the nearest tenth digit.

Time frame: Week 96

Percentage of Participants With HIV-1 RNA ≥50 Copies/mL at Week 144

The Abbott RealTime PCR assay with a reliable lower limit of quantification of 40 copies/mL was used to measure the HIV-1 RNA level in blood samples obtained at each visit. Per protocol, the secondary outcome measure, percentage of participants with HIV-1 RNA ≥50 copies/mL at Week 144, is presented using the FDA snapshot missing data approach. The percentage values were rounded to the nearest tenth digit.

Time frame: Week 144

Percentage of Participants With HIV-1 RNA <50 Copies/mL at Week 48

The Abbott RealTime PCR assay with a reliable lower limit of quantification of 40 copies/mL was used to measure the HIV-1 RNA level in blood samples obtained at each visit. Per protocol, the secondary outcome measure, the percentage of participants with HIV-1 RNA \<50 copies/mL at Week 48, is presented using the FDA snapshot missing data approach. The percentage values were rounded to the nearest tenth digit.

Time frame: Week 48

Percentage of Participants With HIV-1 RNA <40 Copies/mL at Week 48

The Abbott RealTime PCR assay with a reliable lower limit of quantification of 40 copies/mL was used to measure the HIV-1 RNA level in blood samples obtained at each visit. Per protocol, the secondary outcome measure, the percentage of participants with HIV-1 RNA \<40 copies/mL at Week 48, is presented using the FDA snapshot missing data approach.

Time frame: Week 48

Percentage of Participants With HIV-1 RNA <50 Copies/mL at Week 96

The Abbott RealTime PCR assay with a reliable lower limit of quantification of 40 copies/mL was used to measure the HIV-1 RNA level in blood samples obtained at each visit. Per protocol, the secondary outcome measure, the percentage of participants with HIV-1 RNA \<50 copies/mL at Week 96, is presented using the FDA snapshot missing data approach. The percentage values were rounded to the nearest tenth digit.

Time frame: Week 96

Percentage of Participants With HIV-1 RNA <40 Copies/mL at Week 96

The Abbott RealTime PCR assay with a reliable lower limit of quantification of 40 copies/mL was used to measure the HIV-1 RNA level in blood samples obtained at each visit. Per protocol, the secondary outcome measure, the percentage of participants with HIV-1 RNA \<40 copies/mL at Week 96, is presented using the FDA snapshot missing data approach.

Time frame: Week 96

Percentage of Participants With HIV-1 RNA <50 Copies/mL at Week 144

The Abbott RealTime PCR assay with a reliable lower limit of quantification of 40 copies/mL was used to measure the HIV-1 RNA level in blood samples obtained at each visit. Per protocol, the secondary outcome measure, the percentage of participants with HIV-1 RNA \<50 copies/mL at Week 144 is presented using the FDA snapshot missing data approach. The percentage values were rounded to the nearest tenth digit.

Time frame: Week 144

Percentage of Participants With HIV-1 RNA <40 Copies/mL at Week 144

The Abbott RealTime PCR assay with a reliable lower limit of quantification of 40 copies/mL was used to measure the HIV-1 RNA level in blood samples obtained at each visit. Per protocol, the secondary outcome measure, percentage of participants with HIV-1 RNA \<40 copies/mL at Week 144, is presented using the FDA snapshot missing data approach.

Time frame: Week 144

Mean Change From Baseline in Cluster of Differentiation-positive (CD4+) T-cell Count at Week 48

Plasma CD4+ T-cell count was measured in cells/mm\^3 for baseline and 48 weeks by a central laboratory. Baseline measurement of CD4+ T-cell count is defined as the day 1 value for each participant. The mean change from baseline in CD4+ T-cell count at week 48 using the data as observed (DAO) approach is presented. A negative value indicates a mean decrease in CD4+ T-cell count from baseline and a positive value indicates a mean increase in CD4+ T-cell count from baseline.

Time frame: Baseline and Week 48

Mean Change From Baseline in CD4+ T-cell Count at Week 96

Plasma CD4+ T-cell count was measured in cells/mm\^3 for baseline and 96 weeks by a central laboratory. Baseline measurement of CD4+ T-cell count is defined as the day 1 value for each participant. The mean change from baseline in CD4+ T-cell count at week 96 using the data as observed (DAO) approach is presented. A negative value indicates a mean decrease in CD4+ T-cell count from baseline and a positive value indicates a mean increase in CD4+ T-cell count from baseline.

Time frame: Baseline and Week 96

Mean Change From Baseline in CD4+ T-cell Count at Week 144

Plasma CD4+ T-cell count was measured in cells/mm\^3 for baseline and 144 weeks by a central laboratory. Baseline measurement of CD4+ T-cell count is defined as the day 1 value for each participant. The mean change from baseline in CD4+ T-cell count at week 144 using the data as observed (DAO) approach is presented. A negative value indicates a mean decrease in CD4+ T-cell count from baseline and a positive value indicates a mean increase in CD4+ T-cell count from baseline.

Time frame: Baseline and Week 144

Number of Participants With Viral Drug Resistance-associated Substitutions at Week 48

Viral drug resistance is defined as participants with confirmed HIV-1 RNA ≥400 copies/mL having genotypic or phenotypic evidence of resistance to the study drug administered. The number of participants who demonstrate drug resistance is presented.

Time frame: Week 48

Number of Participants With Evidence of Viral Drug Resistance-associated Substitutions at Week 96

Viral drug resistance is defined as participants with confirmed HIV-1 RNA ≥400 copies/mL and/or genotypic or phenotypic analysis of data showing evidence of resistance to the study drug administered. The number of participants who demonstrate drug resistance at week 96 is presented.

Time frame: Week 96

Number of Participants With Evidence of Viral Drug Resistance-associated Substitutions at Week 144

Viral drug resistance is defined as participants with confirmed HIV-1 RNA ≥400 copies/mL and/or genotypic or phenotypic analysis of data showing evidence of resistance to the study drug administered. The number of participants who demonstrate drug resistance at week 144 is presented.

Time frame: Week 144

Change From Baseline in Body Weight at Week 48

Body weight was measured and recorded at baseline and week 48. Participants removed their shoes and wore a single layer of clothing at each measurement. The mean change from baseline in body weight at week 48 is presented.

Time frame: Baseline and Week 48

Change From Baseline in Body Weight at Week 96

Body weight was measured and recorded at baseline and week 96. Participants removed their shoes and wore a single layer of clothing at each measurement. The mean change from baseline in body weight at week 96 is presented.

Time frame: Baseline and Week 96

Change From Baseline in Body Weight at Week 144

Body weight was measured and recorded at baseline and week 144. Participants removed their shoes and wore a single layer of clothing at each measurement. The mean change from baseline in body weight at week 144 is presented.

Time frame: Baseline and Week 144

Percentage of Participants With One or More AEs

An AE is any untoward medical occurrence in a clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. An AE can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease (new or exacerbated) temporally associated with the use of a study intervention. The percentage of participants who experienced at least one or more AEs is presented. Per protocol, pregnancy-related AEs collected for enrolled participants are reported separately and are presented in the AE module.

Time frame: Up to approximately 55 months

Percentage of Participants Who Discontinued Study Intervention Due to an AE

An AE is any untoward medical occurrence in a clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. An AE can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease (new or exacerbated) temporally associated with the use of a study intervention. The percentage of participants who discontinued study intervention due to an AE is presented. Per protocol, pregnancy-related AEs collected for enrolled participants are reported separately and are presented in the AE module.

Time frame: Up to approximately 40 months