Regeneron's Garetosmab Receives FDA Priority Review for Rare Bone Disorder FOP

The U.S. Food and Drug Administration has accepted for Priority Review the Biologics License Application for garetosmab for the treatment of adults with fibrodysplasia ossificans progressiva. The target action date for the FDA decision is August 2026.

Garetosmab is a monoclonal antibody that blocks Activin A, a protein discovered to be critical in the development of heterotopic ossification lesions in people with FOP. If approved, garetosmab would be the first and only available treatment shown to reduce the number and volume of new heterotopic bone lesions in adults with FOP.

The BLA is supported by positive Phase 3 OPTIMA results showing large reductions in new heterotopic bone lesions and volume versus placebo. The OPTIMA Phase 3 trial demonstrated a 94% reduction in new HO lesions at the 3 mg/kg dose and a 90% reduction in new HO lesions at the 10 mg/kg dose. The trial also showed greater than 99% reduction in mean total volume of new HO lesions.

The safety profile showed common adverse reactions including epistaxis and increased hair growth. Common adverse reactions occurring in 30% or more of patients included epistaxis, hypertrichosis, abscess, and acne. Serious treatment-emergent adverse events were reported in 3 garetosmab-treated patients.

FOP is a relentless, ultra-rare genetic disorder in which muscles, tendons, ligaments and other connective tissues are progressively infiltrated by abnormal bone formation, a process known as HO, which results in significant disfunction of these structures and skeletal deformity. HO of the jaw, spine, hip and rib cage can make it difficult to speak, eat, walk or breathe, leading to weight loss. Approximately 900 patients are diagnosed with FOP worldwide.