FDA Accepts Regeneron's Garetosmab BLA For Priority Review For Treatment Of Adults With Fibrodysplasia Ossificans Progressiva

FOP is an ultra-rare genetic disorder characterized by abnormal bone formation that infiltrates muscles, tendons, ligaments and other connective tissues, resulting in significant disability 

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

TARRYTOWN, N.Y., Feb. 19, 2026 (GLOBE NEWSWIRE) -- Regeneron Pharmaceuticals, Inc. (NASDAQ:REGN) today announced that the U.S. Food and Drug Administration (FDA) has accepted for Priority Review the Biologics License Application (BLA) for garetosmab for the treatment of adults with fibrodysplasia ossificans progressiva (FOP). Garetosmab is a monoclonal antibody that blocks Activin A, a protein that Regeneron scientists discovered to be critical in the development of heterotopic ossification (HO) lesions in people with FOP. The target action date for the FDA decision is August 2026.

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 and escalating loss of mobility. Most people with FOP are wheelchair bound by 30 years old, and the median age of survival is approximately 56 years. Approximately 900 people are diagnosed with FOP worldwide, with many others thought to remain undiagnosed or misdiagnosed.

The BLA is supported by efficacy and safety data from the positive Phase 3 OPTIMA trial evaluating garetosmab in adults with FOP. Both garetosmab doses (3 mg/kg and 10 mg/kg) evaluated in the trial were highly efficacious in reducing the total number and volume of new HO lesions at 56 weeks, compared to placebo. Regarding the primary endpoint analysis of reduction in total number of new HO lesions compared to placebo (n=21), those receiving the 3 mg/kg dose (n=19) experienced a 94% reduction (1 lesion vs. 19 lesions; p=0.0274), while those receiving the 10 mg/kg dose (n=23) experienced a 90% reduction (2 lesions vs. 19 lesions; p=0.0260). A post-hoc analysis also found both doses of garetosmab demonstrated a greater than 99% reduction in mean total volume (cm3) of new HO lesions compared to placebo (3 mg/kg: 0.01 cm3 vs. 10.45 cm3; nominal p=0.0013; 10 mg/kg: 0.02 cm3 vs. 10.45 cm3; nominal p=.0005).

At 56 weeks, among all 63 people with FOP aged 18 years and older who participated in the OPTIMA trial, serious treatment-emergent adverse events occurred in 1 patient treated with 3 mg/kg garetosmab, 2 patients treated with 10 mg/kg garetosmab and 2 patients treated with placebo. The most common adverse reactions (incidence ≥30%) are epistaxis, increased hair growth, abscess and acne.

Priority Review is granted to regulatory applications seeking approval for therapies that have the potential to provide significant improvements in the treatment, diagnosis or prevention of serious conditions. The FDA previously granted Fast Track designation and Orphan Drug Designation for garetosmab for the prevention of HO in patients with FOP. Garetosmab has also been granted Orphan Designation in the European Union, and additional garetosmab regulatory submissions are planned in countries around the world.

The safety and efficacy of garetosmab, as well as its potential use for the treatment of FOP, are investigational and have not been fully evaluated or approved by any regulatory authority.

About the OPTIMA Clinical Trial

OPTIMA is a Phase 3, multi-center, multinational trial to assess the efficacy of garetosmab on the reduction of heterotopic bone formation, as well as its safety, tolerability, and pharmacokinetics, in patients with active FOP.

The trial enrolled 63 participants aged 18 years and older who have any FOP-causing variant of type I Activin A receptor (ACVR1), exhibited FOP disease activity or progression of HO lesions, and had a cumulative analogue joint involvement scale (CAJIS) score at screening of ≤19. CAJIS is a clinician-assessed tool, with higher scores representing greater disease severity (scale: 0 to 30). Eligible participants were randomized to intravenously receive 3 mg/kg garetosmab, 10 mg/kg garetosmab, or placebo once every four weeks for 56 weeks. Following this, participants could elect to extend their treatment for at least 84 weeks or discontinue treatment and enter an observation-only arm.

During the treatment period, efficacy was evaluated through whole body computed tomography (CT) scans for HO lesions; physician and patient assessment of flare-ups; utilization of CAJIS to rate joint functionality; and observances of change in disease severity. Safety assessment includes reports of adverse events, measurement of vital signs, physical examination, and coagulation testing.

A Phase 3 trial of garetosmab in adolescents and children with FOP, OPTIMA 2, is planned to begin later this year.