The FDA approved Merck & Co.’s once-daily HIV regimen Idvynso (doravirine/islatravir), giving patients a new option and increasing competitive pressure on existing standard therapies. The approval covers adults with HIV-1 who are virologically suppressed and meet specific resistance and treatment-failure criteria, with a timeline that converges around a recently noted PDUFA date. The decision is expected to matter for sequencing in real-world care—particularly for patients switching due to safety or tolerability concerns rather than virologic failure. Merck’s entry also provides a new benchmark for pharmacy and formulary strategies across U.S. payers. From a market perspective, the approval sets up more head-to-head discussions among manufacturers in the broader antiretroviral landscape, with potential implications for adherence programs built around once-daily dosing.