The FDA approved Regeneron's Pasatru (garetosmab-grts) on Aug. 19 as the first treatment for fibrodysplasia ossificans progressiva, an ultra-rare genetic disorder affecting about 900 people worldwide. Phase 3 OPTIMA trial data showed a 90% to 94% reduction in new heterotopic ossification lesions at 56 weeks.
The FDA approved Regeneron's Pasatru (garetosmab-grts) on Aug. 19, the first FOP treatment, cutting new bone lesions by 90% to 94%.
"For people living with FOP, every irregular new bone formation is a step toward disability and potential loss of mobility," Dr. Kathryn Dahir, professor at Vanderbilt University and primary investigator for the OPTIMA trial, said. "With the ability to reduce the number of new bone lesions and flare-ups, we now have a new treatment that can positively affect patients."
The approval is based on the Phase 3 OPTIMA trial of 63 adults with fibrodysplasia ossificans progressiva (FOP), an ultra-rare genetic disorder in which muscles, tendons, and ligaments are progressively replaced by rogue bone. At 56 weeks, the 10 mg/kg dose reduced new heterotopic ossification (HO) lesions by 90% (2 vs. 19 for placebo), while the 3 mg/kg dose achieved a 94% reduction (1 vs. 19). Clinician-assessed flare-ups fell 88% on the higher dose (9 vs. 66 for placebo) but only 15% on the lower dose (53 vs. 66). Serious treatment-emergent adverse events occurred in two patients on the 10 mg/kg dose, one on 3 mg/kg, and two on placebo. Common adverse reactions included abscess, acne, increased hair growth, oral ulcers, and nosebleeds.
FOP affects approximately 900 people worldwide, with most patients wheelchair-bound by age 30 and a median survival of 56 years. Pasatru is administered intravenously once monthly at a starting dose of 10 mg/kg, with home infusion available where appropriate. The drug is a fully human monoclonal antibody that blocks Activin A, a protein Regeneron scientists identified as critical to HO lesion development. Pasatru previously received Fast Track and Orphan Drug Designation from the FDA.
Regeneron's Q2 2026 revenue reached $4.3 billion, up 16.7% year over year. The company plans to begin OPTIMA 2, a pediatric trial of Pasatru, later this year. A European regulatory submission is under review by the European Medicines Agency, with additional filings planned in Japan and other markets.
"This approval is monumental for our community, providing a vital new therapy that can have a significant impact on the life of someone with FOP," Michelle Davis, executive director of the International FOP Association, said.
The approval gives Regeneron a first-mover position in an underserved ultra-rare disease market. Wall Street analysts at HSBC, Barclays, and Truist Securities have issued buy ratings on the stock, with a median price target of $769 across 17 analysts. Investors will watch the OPTIMA 2 pediatric trial launch and European regulatory decision as the next catalysts.
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