FDA Approves Regeneron’s Pasatru for Rare Bone Disorder FOP

Regeneron Pharmaceuticals has received U.S. Food and Drug Administration approval for Pasatru (garetosmab-grts), a new treatment for adults living with fibrodysplasia ossificans progressiva (FOP), an ultra-rare genetic disorder that causes abnormal bone formation in muscles and other connective tissues.

Pasatru is approved to reduce the formation of new heterotopic ossification (HO) lesions and clinician-assessed flare-ups in adults with FOP. The treatment is administered intravenously once every four weeks and can be given in different care settings, including home infusion where appropriate.

FOP is a severe and progressive condition in which abnormal bone forms in muscles, tendons, ligaments and other soft tissues. Over time, the extra bone can restrict movement and make everyday activities such as speaking, eating, walking and breathing increasingly difficult.

Around 900 people worldwide are diagnosed with FOP. Many patients experience significant loss of mobility, with most becoming wheelchair-dependent by the age of 30.

Pasatru is a fully human monoclonal antibody that blocks Activin A, a protein identified by Regeneron scientists as a key driver of abnormal bone formation in people with FOP.

The FDA approval was supported by results from Regeneron’s Phase 3 OPTIMA trial. At 56 weeks, patients receiving either the 10 mg/kg or 3 mg/kg dose showed a major reduction in new HO lesions compared with placebo.

Patients receiving the 10 mg/kg dose had two new lesions, compared with 19 in the placebo group, representing a 90% reduction. Those receiving the 3 mg/kg dose had one new lesion, representing a 94% reduction compared with placebo.

The higher 10 mg/kg dose also reduced clinician-assessed flare-ups by 88% compared with placebo. Serious treatment-emergent adverse events were reported in two patients receiving the higher dose, one patient receiving the lower dose and two patients in the placebo group.

Common side effects included abscesses, acne, increased hair growth, loss of eyebrows, mouth ulcers, nosebleeds, folliculitis, nail infections and rash.

Dr. Kathryn Dahir of Vanderbilt University and a primary investigator in the OPTIMA trial said the approval provides an important new treatment option for people living with FOP.

Michelle Davis, Executive Director of the International FOP Association, described the approval as a major milestone for the FOP community and their families.

Regeneron said the approval follows decades of research into the role of Activin A in FOP and reflects the company’s focus on developing treatments for people with rare diseases.

The company will support eligible patients through its myRARE program, which provides information on treatment access, insurance benefit verification and potential financial assistance.

Meanwhile, Pasatru is also under regulatory review in the European Union. Regeneron plans to submit the treatment for approval in additional countries, including Japan.

The therapy had previously received FDA Fast Track and Orphan Drug Designations, along with orphan designations from regulators in Europe and Japan.