Merck’s Doravirine/Islatravir HIV Treatment Shows Promising Phase 3 Results

Merck, known as MSD outside the U.S. and Canada, announced the results of two key Phase 3 clinical trials evaluating its investigational once-daily, single-tablet HIV treatment combining doravirine and islatravir (DOR/ISL 100 mg/0.25 mg). The trials, MK-8591A-051 and MK-8591A-052, focused on adults with HIV-1 who were virologically suppressed on other antiretroviral therapies.

Both studies met their primary goals, showing that DOR/ISL was as effective (non-inferior) as baseline antiretroviral therapy (bART) in the open-label MK-8591A-051 trial and comparable to bictegravir/emtricitabine/tenofovir alafenamide (BIC/FTC/TAF) in the double-blind MK-8591A-052 trial. The percentage of participants with HIV-1 RNA levels less than 50 copies/mL at Week 48 was comparable across the treatments, demonstrating DOR/ISL’s effectiveness. While superiority criteria were not met in the MK-8591A-052 trial, both studies met their safety objectives, confirming the treatment's tolerability.

Merck plans to present detailed findings at an upcoming scientific conference and submit the data to regulatory authorities for review. In the U.S., doravirine is already approved as part of other HIV treatments, including PIFELTRO and DELSTRIGO. Islatravir (MK-8591), Merck’s experimental nucleoside reverse transcriptase translocation inhibitor (NRTTI), is designed to prevent the incorporation of nucleotides into the DNA chain, effectively halting the replication of the virus. It is being studied in both early and late-stage clinical trials in combination with other antiretroviral therapies.

In addition to the recently completed Phase 3 trials, ongoing studies include trials on treatment-naïve individuals (MK-8591A-053) and an open-label evaluation (MK-8591A-054) of DOR/ISL in participants from earlier Phase 3 studies. These trials highlight Merck’s continued commitment to advancing HIV treatment options.

“We are encouraged by the results from these Phase 3 trials evaluating a once-daily, oral, two-drug, single-tablet regimen of doravirine and islatravir. We are committed to advancing our clinical programs for islatravir in combination with other antiretrovirals as potential options to help address the needs of people living with HIV,” said Dr Eliav Barr, senior vice president, head of global clinical development and chief medical officer of Merck Research Laboratories.