Regeneron Gets Speedy FDA Review of Garetosmab in FOP

Regeneron's treatment for rare genetic disorder could be first and only available option.

Published on Feb. 24, 2026

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Regeneron Pharmaceuticals has won U.S. Food and Drug Administration priority review for its application seeking approval of garetosmab for adults with the ultra-rare genetic disorder fibrodysplasia ossificans progressiva, or FOP. Garetosmab, if approved, would be the first and only available treatment shown to reduce the number and volume of new heterotopic bone lesions in adults with FOP, which is characterized by abnormal bone formation that infiltrates muscles, tendons, ligaments and other connective tissues, resulting in significant disability.

Why it matters

The FDA's priority review designation for garetosmab indicates the potential for this treatment to provide significant improvements in the treatment of FOP, a debilitating and extremely rare genetic disorder. With no currently approved therapies, the availability of garetosmab could be transformative for FOP patients.

The details

Regeneron said the FDA has set an August target action date for the application. The company also plans to start a Phase 3 study of garetosmab in adolescents and children with FOP later this year.

  • Regeneron won FDA priority review on February 19, 2026.
  • The FDA has set an August target action date for Regeneron's application.
  • Regeneron plans to start a Phase 3 study of garetosmab in adolescents and children with FOP later in 2026.

The players

Regeneron Pharmaceuticals

A biotechnology company that develops medicines for serious diseases.

U.S. Food and Drug Administration (FDA)

The federal agency responsible for regulating and supervising the safety of food, drugs, and other products in the United States.

Garetosmab

Regeneron's investigational treatment for fibrodysplasia ossificans progressiva (FOP), a rare genetic disorder characterized by abnormal bone formation.

Fibrodysplasia Ossificans Progressiva (FOP)

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

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What’s next

Regeneron plans to start a Phase 3 study of garetosmab in adolescents and children with FOP later in 2026.

The takeaway

The FDA's priority review of Regeneron's garetosmab highlights the significant unmet need for effective treatments for the debilitating genetic disorder FOP. If approved, garetosmab could become the first and only available therapy shown to reduce the progression of this rare and disabling condition.