The FDA cleared Regeneron’s garetosmab, now marketed as Pasatru, for adults with fibrodysplasia ossificans progressiva (FOP), an ultra-rare genetic disorder that drives soft-tissue to bone conversion. Regeneron positioned the antibody as targeting activin A to reduce new abnormal bone formation and associated inflammatory flare-ups. The approval follows a pivotal Phase 3 trial (Optima) that randomized 63 adults to two Pasatru doses or placebo every four weeks for 56 weeks. Regeneron said both dosing arms reduced new bone lesions by 90% or more versus placebo, and the higher dose also cut clinician-assessed flare-ups. Regeneron becomes the second FDA-cleared therapy for FOP after Ipsen’s Sohonos (palovarotene), and the company is expected to target commercial differentiation through flare-up reduction and the activation of the activin A pathway. Pasatru’s launch also adds to Regeneron’s rare-disease momentum at a time when the company faces continued scrutiny of broader strategy, with analysts likely to watch uptake against existing standard-of-care approaches.