The FDA cleared Regeneron’s Pasatru (garetosmab) to treat fibrodysplasia ossificans progressiva (FOP), intensifying competition in an ultra-rare bone-loss market that already has Ipsen’s Sohonos. Pasatru is an Activin A–targeting antibody (given IV every four weeks) that is designed to reduce abnormal bone formation and flare-ups that drive progressive mobility loss. The approval was supported by Phase 3 Optima data announced last September, where Pasatru reduced new bone formations by 90% or more over 56 weeks versus placebo and reduced inflammatory “flare-ups” in the same trial. Regeneron said Pasatru will be available within the U.S. for roughly 220 adult patients with FOP. Financial terms were disclosed ahead of launch, with a per-patient list-price estimate around $1.4 million annually based on clinical study enrollment. Regeneron’s access and pricing strategy will be tested as it positions Pasatru against Ipsen’s earlier FDA approval and ongoing questions about benefit–risk tradeoffs in that class.