A once-daily combination pill containing doravirine and islatravir maintained viral suppression for a year in a pair of late-stage trials. Doravirine (sold alone as Pifeltro) is Merck’s next-generation non-nucleoside reverse transcriptase inhibitor, while islatravir is an experimental nucleoside reverse transcriptase translocation inhibitor. Islatravir previously hit a snag when participants in early trials experienced declines in CD4 and total lymphocyte counts, but scientists determined that the doses used were too high. Two subsequent Phase III trials tested a single-tablet regimen containing doravirine plus a lower dose of islatravir. Together, they enrolled more than 1,000 adults with an undetectable viral load on Biktarvy (bictegravir/tenofovir alafenamide/emtricitabine) or other baseline antiretroviral regimens. The doravirine/islatravir combo maintained viral suppression at 48 weeks, and researchers did not see the blood cell declines that doomed the higher islatravir dose. Merck plans to submit the data to the Food and Drug Administration for approval.