Regeneron announced on Aug. 19, 2026, that the U.S. FDA approved Pasatru (garetosmab-grts) for adults with fibrodysplasia ossificans progressiva (FOP), an ultra-rare genetic disease in which muscles, tendons, ligaments and other connective tissues progressively turn into bone.
The approval covers reduction of new heterotopic ossification (HO) lesions and clinician-assessed disease flare-ups. Pasatru is described as the first FDA-approved treatment shown in a placebo-controlled trial to reduce new HO lesions in adults with FOP, and the second FDA-approved FOP therapy overall.
Approval was supported by the 56-week Phase 3 OPTIMA trial involving 63 adults. New HO lesions fell by 90% at the 10 mg/kg dose and 94% at the 3 mg/kg dose versus placebo, based on CT scans.
At the 10 mg/kg dose, clinician-assessed flare-ups declined by 88% versus placebo; the reduction at 3 mg/kg was 15%.
Pasatru is administered as a monthly intravenous infusion, starting at 10 mg/kg, with reduction to 3 mg/kg if the higher dose is not tolerated. It is currently approved only for adults; pediatric safety and effectiveness have not been established.
Pasatru blocks Activin A, a protein believed to play a central role in abnormal bone formation in FOP. Reported common adverse reactions included skin infections or abscesses, acne, increased hair growth, eyebrow loss, oral ulcers, nosebleeds, folliculitis, nail infections and rash.
Sources:
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