Merck & Co. is pushing forward with a simplified oral HIV treatment – a once-daily, two drug regimen that combines Pifeltro (doravirine) with its experimental nucleoside reverse transcriptase translocation inhibitor islatravir – aiming to file for regulatory approval by mid-2025.The announcement Wednesday follows positive data from two Phase III trials demonstrating that the regimen is just as effective as standard HIV therapies in maintaining viral suppression in adults with HIV-1. Merck first shared topline results in December and unveiled more detail at the Conference on Retroviruses and Opportunistic Infections (CROI) on Wednesday.In one of studies, called MK-8591A-052, the Pifeltro/islatravir combo was tested against Gilead Sciences' HIV treatment Biktarvy (bictegravir/emtricitabine/tenofovir alafenamide) in 513 HIV patients who had virologic suppression for at least three months while on Biktarvy. At 48 weeks, 91.5% of patients who switched to Merck's regimen kept their viral load under control, compared to 94.2% of those on Biktarvy, meeting the bar for non-inferiority. Although the regimen did not achieve superiority over the Gilead's drug.The second trial, dubbed MK-8591A-051, compared Pifeltro/islatravir to patients' existing antiretroviral therapy (bART). Here, 95.6% of patients on Pifeltro/islatravir maintained viral suppression at 48 weeks, versus 91.9% seen in the bART group.If approved, Merck's treatment would be the first two-drug HIV regimen that doesn't include an integrase inhibitor to demonstrate comparable efficacy and safety to the three-drug InSTI-based Biktarvy regimen in a Phase III trial, according to Eliav Barr, chief medical officer at Merck Research Laboratories."These data and our work on the longer-acting islatravir-based therapies in our pipeline show our continued commitment to help find new options that address the evolving needs of people living with HIV," Barr added.The regimen's safety profile was generally comparable to the comparator antiretroviral regimens across both trials. At week 48, the mean percent change in total lymphocyte and CD4 counts were similar between Pifeltro/islatravir and comparator treatments, an issue that had stalled the programme a few years ago. There was also no treatment-emergent resistance to Pifeltro or islatravir in either trial.Beyond this daily oral combination, Merck is also advancing a once-weekly combination of islatravir with Gilead's capsid inhibitor lenacapavir, which showed positive Phase II results in October.