Biopharmaceutical company Merck (NYSE: MRK), known as MSD outside the US and Canada, reported on Wednesday that it has presented new data from two Phase 3 studies evaluating its investigational, once-daily oral two-drug HIV regimen, doravirine/islatravir (DOR/ISL 100mg/0.25mg), in adults with virologically suppressed HIV-1 infection. Findings, presented at the 20th European AIDS Conference in Paris, showed minimal changes in weight, body composition, fasting lipids, and insulin resistance measures, with results comparable to existing therapies.

Data from trials MK-8591A-052 and MK-8591A-051 confirmed that DOR/ISL maintained viral suppression and was non-inferior to standard three-drug regimens, including bictegravir/emtricitabine/tenofovir alafenamide (BIC/FTC/TAF), without observed treatment-emergent resistance. Across studies, changes in fasting lipids, glucose, and the homeostatic model assessment of insulin resistance were minimal and similar between treatment groups.

In MK-8591A-052, participants switching from BIC/FTC/TAF to DOR/ISL experienced negligible weight variation at Week 48, averaging –0.03 kg versus +0.28 kg for those continuing on BIC/FTC/TAF. Adverse event profiles were comparable, with discontinuation rates due to drug-related events below 2% in both groups.

The US Food and Drug Administration accepted Merck's New Drug Application for DOR/ISL earlier this year, with a Prescription Drug User Fee Act (PDUFA) target action date of 28 April 2026.

DOR/ISL combines Merck's non-nucleoside reverse transcriptase inhibitor doravirine with islatravir, an investigational nucleoside reverse transcriptase translocation inhibitor (NRTTI). Islatravir is under evaluation for both daily and weekly treatment and prevention regimens.

Merck has been engaged in HIV research for more than 35 years, developing multiple therapies and advancing prevention strategies to help reduce the global burden of infection.