Regeneron Pharmaceuticals announced that the U.S. Food and Drug Administration has accepted for Priority Review the Biologics License Application (BLA) for garetosmab, marking a significant milestone for patients living with fibrodysplasia ossificans progressiva (FOP). The FDA is expected to make a decision by August 2026 as was reported by Drugs.com.
FOP is an ultra-rare genetic disorder affecting approximately 900 people worldwide. The condition causes muscles, tendons, ligaments, and other connective tissues to be progressively replaced by abnormal bone formation, a process called heterotopic ossification (HO). This abnormal bone growth leads to severe skeletal deformity and significant disability. When HO affects the jaw, spine, hip, and rib cage, patients experience difficulty speaking, eating, walking, and breathing. Most individuals with FOP become wheelchair-dependent by age 30, with a median life expectancy of approximately 56 years.
Garetosmab is a fully human monoclonal antibody that blocks Activin A, a protein that Regeneron scientists identified as critical to HO development in FOP patients. If approved, garetosmab would be the first and only treatment demonstrated to reduce the number and volume of new heterotopic bone lesions in adults with FOP.
The FDA’s Priority Review decision was based on compelling efficacy and safety data from the Phase 3 OPTIMA trial. In the study, both garetosmab doses tested showed remarkable results. Patients receiving the 3 mg/kg dose experienced a 94% reduction in new HO lesions compared to placebo (1 lesion versus 19 lesions), while those receiving the 10 mg/kg dose saw a 90% reduction (2 lesions versus 19 lesions). Additionally, both doses demonstrated a greater than 99% reduction in the mean total volume of new bone lesions.
Safety monitoring of the 63 trial participants aged 18 and older revealed a favorable safety profile. Serious adverse events occurred in only 1 patient in the 3 mg/kg group, 2 patients in the 10 mg/kg group, and 2 placebo recipients. The most common side effects—occurring in 30% or more of patients, included nosebleeds, increased hair growth, abscess formation, and acne.
This Priority Review status reflects the FDA’s recognition that garetosmab has the potential to provide significant improvements in treating a serious condition. Regeneron previously received Fast Track designation and Orphan Drug Designation for the therapy, and garetosmab has also been granted Orphan Designation in the European Union with additional regulatory submissions planned worldwide.
Looking ahead, Regeneron plans to initiate OPTIMA 2, a Phase 3 trial evaluating garetosmab in adolescents and children with FOP, later this year. For patients living with this devastating rare disease, the FDA’s acceptance of garetosmab for Priority Review represents hope for the first disease-modifying treatment option.
