A once-daily combination pill containing doravirine and islatravir maintained viral suppression for a year in a pair of Phase III trials. Doravirine (Pifeltro) is a next-generation non-nucleoside reverse transcriptase inhibitor, while islatravir is the first nucleoside reverse transcriptase translocation inhibitor. Islatravir hit a snag in 2021 when participants in earlier trials showed declines in CD4 and total lymphocyte counts, but the doses used were too high. Two subsequent trials tested a single-tablet regimen containing doravirine plus a lower dose of islatravir. Participants with viral suppression on Biktarvy (bictegravir/tenofovir alafenamide/emtricitabine) or another oral regimen were randomized to switch to doravirine/islatravir or stay on the same combo. More than 90% of people in all treatment groups had an undetectable viral load at 48 weeks, showing that doravirine/islatravir was non-inferior. Treatment was well tolerated, and the researchers did not see the same blood cell declines that doomed higher doses of islatravir.