Regeneron’s garetosmab, branded Pasatru, won FDA approval for fibrodysplasia ossificans progressiva (FOP), adding a second approved therapy for the ultra-rare bone-forming disorder. The antibody targets activin A, aiming to suppress abnormal endochondral bone formation and reduce painful flare-ups that precede tissue ossification. The approval follows late-stage results in which Pasatru reduced new abnormal bone lesions by 90% or more versus placebo across the 10- and 3-mg/kg regimens, and also reduced flare-up outcomes in adult patients in the pivotal Optima trial program. Regulators cleared Pasatru for adult use, with an anticipated launch targeting the small U.S. FOP patient community. Commercially, the approval is framed as a head-to-head competitive dynamic with Ipsen’s Sohonos (palovarotene), which has faced scrutiny around comparative benefit and flare-up safety signals in prior regulatory discussions.