Merck's HIV-1 Regimen Shows Positive Phase III Results

The success criterion for the primary efficacy hypothesis, as measured by the percentage of participants with HIV-1 RNA levels ≥50 copies/mL at Week 48, was met in both trials. DOR/ISL was demonstrated to be non-inferior to bART in open-label trial MK-8591A-051 and non-inferior to BIC/FTC/TAF in double-blind trial MK-8591A-052. The superiority criteria were not met in trial MK-8591A-052. Primary safety objectives of both trials were also met.

The company is planning to present detailed findings from these trials at a future scientific congress and will also plan to file these data with regulatory authorities. In the U.S., doravirine is approved for the treatment of adults with HIV-1 in combination with other antiretrovirals, as a single agent (PIFELTRO) and a component of a single-tablet regimen [DELSTRIGO; doravirine, lamivudine, and tenofovir disoproxil fumarate (DOR/3TC/TDF)].

Islatravir (MK-8591), Merck’s investigational nucleoside reverse transcriptase translocation inhibitor (NRTTI), exhibits both transcriptase and translocation inhibition (which prevents nucleotide binding and incorporation to the DNA chain, resulting in immediate chain termination) and delayed chain termination (which prevents nucleotide incorporation even in the event of translocation). Islatravir is being evaluated in multiple early and late-stage clinical trials in combination with other antiretroviral therapies for the treatment of HIV-1. In addition to the MK-8591A-051 and MK-8591A-052 trials, ongoing Phase III trials of DOR/ISL include MK-8591A-053 in people with HIV who had not previously received treatment (treatment-naïve), and MK-8591A-054 evaluating open-label DOR/ISL (100 mg/0.25 mg) in individuals who participated in earlier Phase III trials of DOR/ISL (100 mg/0.75 mg).

About MK-8591A-051 ( NCT05631093 )

MK-8591A-051 is a Phase III, randomized, active-controlled, open-label clinical trial evaluating a switch to investigational, oral, once-daily DOR/ISL (100 mg/0.25 mg) in adults with HIV-1 infection that has been virologically suppressed using ART. Participants (n=551) were randomized 2:1 to either switch to investigational DOR/ISL or continue with their current bART regimen through Week 48. After Week 48, all participants receive DOR/ISL through Week 144 of the trial. After Week 144, eligible participants may continue on DOR/ISL and continue trial treatment until Week 240 or when DOR/ISL becomes commercially accessible (whichever comes first). The primary efficacy (percentage of participants with HIV-1 RNA levels ≥50 copies/mL) and safety (number of participants experiencing adverse events (AEs) and discontinuing trial intervention due to AEs) endpoints were assessed at Week 48.

About MK-8591A-052 ( NCT05630755 )

MK-8591A-052 is a Phase III, randomized, active-controlled, double-blind clinical trial evaluating a switch to investigational, oral, once-daily DOR/ISL (100mg /0.25mg) in adults with HIV-1 infection that has been virologically suppressed using BIC/FTC/TAF (50 mg/200 mg/25 mg). Participants (n=513) were randomized 2:1 to either switch to DOR/ISL or continue on BIC/FTC/TAF through Week 144. After Week 144, eligible participants may continue on DOR/ISL and continue trial treatment until Week 240 or when DOR/ISL becomes commercially accessible (whichever comes first). The primary efficacy (percentage of participants with HIV-1 RNA levels ≥50 copies/mL) and safety (number of participants experiencing AEs and discontinuing trial intervention due to AEs) endpoints were assessed at Week 48.