Merck, also known as MSD outside the US and Canada, has announced positive topline results from two Phase 3 trials of doravirine/islatravir (DOR/ISL) in adults with HIV-1 virus.
The trials evaluated the investigational, once-daily, oral, two-drug, single-tablet regimen of doravirine/islatravir. The combination was assessed in adults with virologically suppressed HIV-1 on various antiretroviral therapy regimens, including baseline antiretroviral therapy (bART) or bictegravir/emtricitabine/tenofovir alafenamide (BIC/FTC/TAF).
In October 2021, Merck announced positive top-line results from two Phase 3 trials of doravirine/islatravir in adults with virologically suppressed HIV-1. Both trials met primary efficacy endpoints, showing comparable antiviral efficacy, with consistent safety and tolerability.
During the same period, Gilead Sciences and Merck initiated a Phase 2 clinical HIV study of islatravir in combination with the former’s potential capsid inhibitor lenacapavir.
MK-8591A-051 is a Phase 3, randomised, open-label trial assessing a switch to oral, once-daily DOR/ISL in adults with virologically suppressed HIV-1 on antiretroviral therapy (ART).
MK-8591A-052 is a Phase 3, randomised, double-blind trial evaluating a switch to oral, once-daily DOR/ISL in adults with virologically suppressed HIV-1 on BIC/FTC/TAF.
Merck announced that the primary efficacy success criterion was met in both Phase 3 trials evaluating doravirine/islatravir.
In the MK-8591A-051 study, the combination was shown to be non-inferior to baseline antiretroviral therapy (bART).
In the MK-8591A-052 trial, DOR/ISL was non-inferior to bictegravir/emtricitabine/tenofovir alafenamide (BIC/FTC/TAF).
However, superiority was not achieved in MK-8591A-052. Both trials also met their primary safety objectives.
The drugmaker plans to present detailed findings from these trials to regulatory authorities.
Merck research laboratories senior vice president, global clinical development head and chief medical officer Eliav Barr said: “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 programmes for islatravir in combination with other antiretrovirals as potential options to help address the needs of people living with HIV.”
In the US, doravirine is already approved as a single agent under the brand name PIFELTRO and as part of the combination tablet DELSTRIGO, which includes doravirine, lamivudine, and tenofovir disoproxil fumarate.
Islatravir is being evaluated in various early and late-stage clinical trials in combination with other antiretroviral therapies for HIV-1 treatment.
In addition to the MK-8591A-051 and MK-8591A-052 trials, ongoing Phase 3 trials include MK-8591A-053 for treatment-naïve individuals and MK-8591A-054, which assesses open-label DOR/ISL in participants from earlier DOR/ISL Phase 3 trials.
