Merck Announces Data From Phase 3 Trials That Show The Investigational, Once-Daily, Oral, Two-Drug Regimen Of Doravirine/Islatravir Maintained HIV-1 Viral Suppression At Week 48

DOR/ISL demonstrated non-inferiority and a similar safety profile to comparator antiretroviral therapies in adults with virologically suppressed HIV-1

Merck (NYSE:MRK), known as MSD outside of the United States and Canada, today announced the presentation of positive results from two pivotal Phase 3 trials of the investigational, once-daily, oral, two-drug regimen of doravirine/islatravir [DOR/ISL (100mg/0.25mg)] in adults with HIV-1 infection that is virologically suppressed on bictegravir/emtricitabine/tenofovir alafenamidei [BIC/FTC/TAF (50mg/200mg/25mg)] in trial MK-8591A-052) or antiretroviral therapy [baseline antiretroviral therapy (bART)] in trial MK-8591A-051. In both trials, DOR/ISL met the primary efficacy success criterion for non-inferiority to comparator antiretroviral therapies and primary safety objectives at Week 48. The findings will be shared in late-breaking oral presentations at the 32nd Conference on Retroviruses and Opportunistic Infections (CROI) being held in San Francisco and were featured in a CROI press conference. Merck plans to begin submitting applications for marketing authorization to regulatory agencies by mid-2025.

In the double-blind trial MK-8591A-052 (Abstract #204A), results for the primary endpoint (HIV-1 RNA ≥50 copies/mL) showed that 1.5% of participants who switched to DOR/ISL had a viral load of ≥50 copies/mL at Week 48, compared to 0.6% on BIC/FTC/TAF (treatment difference 0.9%, 95% CI -1.9, 2.9). At Week 48, 91.5% of participants who switched to DOR/ISL maintained viral suppression (HIV-1 RNA <50 copies/mL) compared to 94.2% of participants who continued receiving BIC/FTC/TAF (treatment difference -2.6%, 95% CI -7.1, 2.6; secondary endpoint).

In the open-label trial MK-8591A-051 (Abstract #204B), results for the primary endpoint (HIV-1 RNA ≥50 copies/mL) showed that 1.4% of participants who received DOR/ISL had a viral load of ≥50 copies/mL at Week 48, compared to 4.9% on bART (treatment difference -3.6%, 95% CI -7.8, -0.8. At Week 48, 95.6% of participants who switched to DOR/ISL maintained viral suppression (HIV-1 RNA <50 copies/mL) compared to 91.9% of participants who continued on bART (treatment difference 3.7%, 95% CI -0.3, 8.9; secondary endpoint).

Across both trials, the safety profile of DOR/ISL was generally comparable to the comparator antiretroviral regimens, including BIC/FTC/TAF in MK-8591A-052. At Week 48, the mean percent change in total lymphocyte and CD4 counts were similar for DOR/ISL and comparator regimens. No treatment-emergent resistance to DOR or ISL was observed in either trial.