Regeneron Wins FDA Approval for Pasatru, a New Drug for Ultra-Rare Bone Disease

Regeneron Pharmaceuticals received U.S. Food and Drug Administration approval to launch Pasatru, a novel therapy for treating fibrodysplasia ossificans progressiva in adults.

The regulatory approval allows the drug to combat the formation of new heterotopic ossification lesions and reduce the frequency of clinician-assessed flare-ups associated with this ultra-rare disease.

Understanding FOP and Treatment Administration

FOP progressively erodes muscles, ligaments, and tendons with abnormal bone growth. This severe dysfunction impedes basic activities such as eating, speaking, and breathing.

There are approximately 900 confirmed cases worldwide, with a median patient survival age of 56 years, and many patients require wheelchairs by age 30.

Pasatru is a fully human monoclonal antibody that actively blocks the Activin A protein, which is responsible for the development of these abnormal bone lesions.

To accommodate patients facing severe mobility impairments, healthcare providers can administer monthly 60-minute intravenous infusions in a home care setting.

The starting dose is 10 mg/kg, and physicians can reduce it to 3 mg/kg if patients do not tolerate it well.

Clinical Efficacy and Future Regulatory Steps

The positive Phase 3 OPTIMA trial drove the FDA's decision. After 56 weeks of treatment, CT scans showed that the 10 mg/kg and 3 mg/kg doses eliminated 90% and 94% of new lesions, respectively, compared to placebo. Additionally, the 10 mg/kg dose reduced clinician-assessed flare-ups by 88%.

Following U.S. approval, the European Medicines Agency is currently reviewing the treatment, and Regeneron plans to submit additional regulatory applications globally, including in Japan.

REGN Stock Activity: Regeneron Pharmaceuticals shares rose 0.44% in premarket trading Thursday to $844.52.