FDA approves new treatment to curb abnormal bone growth in adults with FOP

The US Food and Drug Administration has approved Pasatru, or garetosmab, for adults with fibrodysplasia ossificans progressiva, an ultra-rare genetic disorder that progressively replaces soft tissue with bone. The intravenous treatment is intended to reduce new heterotopic ossification lesions and clinician-assessed flare-ups, painful episodes that can precede permanent bone formation and further loss of movement.

Approval was supported by OPTIMA, a placebo-controlled phase III trial involving 63 adults. After 56 weeks, doses given every four weeks reduced the number of new lesions detected by low-dose CT scans by 90% to 94% compared with placebo. The recommended 10 mg/kg dose also reduced investigator-assessed flare-ups by 88%, while the lower dose produced a 15% reduction.

Pasatru is only the second FDA-approved treatment for FOP and works by neutralizing activin A, a protein central to abnormal bone growth in the condition. The label warns of embryo-fetal toxicity, skin and soft-tissue infections, and serious nosebleeds; other common adverse events included acne, rash and oral ulcers. The evidence comes from a small trial, reflecting the condition’s rarity, and a study in children and adolescents is planned.