The FDA approved Regeneron’s activin A–targeting antibody, garetosmab—branded Pasatru—for fibrodysplasia ossificans progressiva (FOP), giving patients a second approved option in the ultrarare disorder. In pivotal Phase 3 testing, Pasatru cut new abnormal bone formation by around 90% versus placebo over 56 weeks, and also reduced clinician-assessed flare-ups at higher dosing. Pasatru becomes the second FDA-cleared therapy for FOP, setting up a commercial and clinical differentiation race versus Ipsen’s Sohonos (palovarotene). Regeneron expects Pasatru to be dosed intravenously every four weeks and to reach the estimated adult population eligible in the U.S. The approval follows a development pause in earlier testing after multiple trial deaths, with Regeneron concluding the events were not causally linked to the therapy before advancing the program into late-stage studies.