FDA Approves Second Treatment for Fibrodysplasia Ossificans Progressiva
Action
The U.S. Food and Drug Administration (FDA) has approved Pasatru (garetosmab-grts) to reduce new heterotopic ossification (bone formation outside the skeleton) and reduce clinician-assessed disease flare-ups in adults with fibrodysplasia ossificans progressiva (FOP). Pasatru is the second drug approved for patients with this very rare disease.
The recommended starting dosage of Pasatru is 10 mg/kg infused intravenously (IV) over 60 minutes, once every four weeks. The dosage may be decreased to 3 mg/kg administered intravenously once every four weeks if 10 mg/kg is not tolerated.
Disease or Condition
Fibrodysplasia ossificans progressiva (FOP) is a rare genetic disease caused by a mutation in activin A receptor-type 1, which controls new bone growth. As a result, connective tissues such as muscle, tendons and ligaments gradually turn into bone, causing limited movement, deformities, severe disability, and early death.
Pasatru is an antibody that blocks activation of the abnormal activin A receptor-type 1.
Effectiveness
The effectiveness and safety of Pasatru were evaluated in a randomized, double-blind, placebo-controlled clinical study of 63 adults with FOP. Patients received Pasatru 3 mg/kg, Pasatru 10 mg/kg, or placebo, each given by IV infusion every 4 weeks for 56 weeks. After the initial 56 weeks, 61 patients continued in an extended follow-up phase on the same treatment.
The primary efficacy endpoint was the number of new heterotopic ossification lesions that formed by Week 56, detected using full-body low-dose CT scans. The study also evaluated the number of disease flare-ups (episodes of pain, swelling, or worsening) assessed by the clinician.
Both doses of Pasatru significantly reduced new bone growth compared to placebo (2 new lesions among 23 patients receiving the 10 mg/kg dose and 1 new lesion among 19 patients receiving the 3 mg/kg dose, compared to 19 new lesions among 21 patients receiving placebo). The number of clinician-assessed disease flare ups over the 56 weeks were 9 with the 10 mg/kg dose, 53 with the 3 mg/kg dose and 66 with placebo.
Safety Information
Pasatru has a warning for fetal harm when administered during pregnancy. Patients treated with Pasatru who can become pregnant should use effective birth control methods during treatment and for 6 months after the last dose. Pasatru also has warnings for skin and soft tissue infections requiring treatment or hospitalization and for cases of nose bleeding requiring medical intervention.
The most common adverse reactions include nosebleeds, increased hair growth, abscess, and acne. See the full prescribing information for all risks associated with Pasatru.
Designations
Pasatru received Breakthrough Therapy, Fast Track, Orphan Drug and Priority Review designations for this indication.
FDA granted this approval to Regeneron Pharmaceuticals, Inc.