23 February 2023 - - US-based pharmaceutical company Merck (NYSE: MRK) has opened enrollment in its new Phase 3 clinical program with investigational once-daily islatravir 0.25 mg in combination with doravirine 100 mg (DOR/ISL) for the treatment of HIV-1 infection, the company said.

Two new Phase 3 studies began enrolling participants this month:

MK-8591A-051 A Phase 3, Randomized, Active-Controlled, Open-Label Clinical Study to Evaluate a Switch to Doravirine/Islatravir (DOR/ISL 100 mg/0.25 mg) Once-Daily in Participants With HIV-1 Who Are Virologically Suppressed on Antiretroviral Therapy

MK-8591A-052 A Phase 3, Randomized, Active-Controlled, Double-Blind Clinical Study to Evaluate a Switch to Doravirine/Islatravir (DOR/ISL 100 mg/0.25 mg) Once-Daily in Participants With HIV-1 Who Are Virologically Suppressed on Bictegravir/Emtricitabine/Tenofovir Alafenamide (BIC/FTC/TAF)
The following new Phase 3 studies are expected to begin enrollment in March:

MK-8591A-P053 A Phase 3, Randomized, Active-Controlled, Double-Blind Clinical Study to Evaluate the Antiretroviral Activity, Safety, and Tolerability of Doravirine/Islatravir (DOR/ISL 100 mg/0.25 mg) Once-Daily in HIV-1 Infected Treatment-Naïve Participants

MK-8591A-P054 A Phase 3 Open-label Clinical Study of Doravirine/Islatravir (DOR/ISL [100 mg/0.25 mg]) Once-Daily for the Treatment of HIV-1 Infection in Participants Who Previously Received DOR/ISL (100 mg/0.75 mg) Once-Daily in a Phase 3 Clinical Study

Certain study participants currently enrolled in prior DOR/ISL studies (Protocols 018, 020 and 033), which evaluated once-daily DOR/ISL 100/0.75 mg in treatment-naïve and virologically suppressed participants, will have the option of transitioning to study P054 evaluating once-daily DOR/ISL 100/0.25 mg as a potential fixed-dose combination, two-drug regimen.

Select Merck abstracts for islatravir at the Conference on Retroviruses and Opportunistic Infections 2023 include:

Switch to DOR/ISL (100/0.75MG) QD From B/F/TAF: Week 48 Results From a Phase 3 Trial. Late-breaker oral presentation: 197. Mills, A, et al.

Switch to DOR/ISL (100/0.75MG) QD: Week 48 Results From An Open-label Phase 3 Trial. Late-breaker oral presentation: 196. Molina, J-M, et al.

Effect of Islatravir on Total Lymphocyte and Lymphocyte Subset Counts. Oral presentation: 192. Squires, K, et al.

Modeling To Optimize Islatravir QW Dose in HIV Virologically Suppressed PWH. Late-breaker poster: 497. Vargo, R, et al.