Regeneron posts positive Phase III trial of garetosmab

18 September 2025

Regeneron Pharmaceuticals (Nasdaq: REGN) has announced the primary endpoint was met in the Phase III OPTIMA trial investigating garetosmab in adults with fibrodysplasia ossificans progressiva (FOP).

At 56 weeks, both doses of garetosmab, 3mg/kg and 10 g/kg, were highly efficacious in reducing the number of new bone lesions (heterotopic ossification, or HO lesions) as compared to placebo, demonstrating a 94% and 90% reduction, respectively. Garetosmab is a monoclonal antibody that neutralizes the Activin A protein, which Regeneron scientists discovered to be a critical protein in the development of HO lesions in people with FOP.

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