Pasatru Approved for Fibrodysplasia Ossificans Progressiva
On Aug. 19, 2026, the US Food and Drug Administration (FDA) approved Regeneron Pharmaceuticals’ Pasatru™ (garetosmab-grts) to reduce the formation of new heterotopic ossification (HO) lesions and clinician-assessed flare-ups in adults who have fibrodysplasia ossificans progressiva (FOP). Pasatru is a VelocImmune®-derived, fully human monoclonal antibody that blocks Activin A, a protein critical to the abnormal Activin A receptor type-1 signaling that drives HO in people with FOP. The recommended starting dosage is 10mg/kg administered intravenously (IV) over 60 minutes every four weeks, which may be decreased to 3mg/kg over 60 minutes once monthly if not tolerated. Regeneron states that Pasatru can be administered across a range of care settings, including home infusion. Launch is said to be quick after approval, and pricing has not yet been announced. Full prescribing information can be found here.
At a Glance
- Brand Drug: Pasatru™ (garetosmab-grts)
- Manufacturer: Regeneron
- Date Approved: Aug. 19, 2026
- Indication: To reduce formation of new HO lesions and clinician-assessed flare-ups in adults with FOP
- Dosage Forms Available: 300mg/5mL (60mg/mL) in a single-dose vial
- Launch Date: Shortly after approval.
- Estimated Annual Cost: Not yet announced.
- FDA Designation: Breakthrough Therapy. Fast Track. Orphan Drug. Priority Review.
- FOP is an ultra-rare genetic disorder marked by heterotopic ossification (HO), in which abnormal bone progressively forms in muscles, tendons, ligaments and other connective tissues. When HO affects the jaw, spine, hips and rib cage, it can make speaking, eating, walking and breathing difficult, leading to skeletal deformity, weight loss and progressive loss of mobility.
- Approximately 900 people worldwide are diagnosed with FOP and about 220 Americans are living with the condition. Most become wheelchair-bound by age 30, with a median survival of 56 years.
- Approval was based on the phase III OPTIMA trial of 63 adults, in which both doses significantly reduced new bone growth versus placebo at 56 weeks. There were two new lesions among 23 patients on the 10mg/kg dose (a 90% reduction) and one new lesion among 19 patients on the 3mg/kg dose (a 94% reduction), compared with 19 new lesions among 21 patients on placebo.
- Pasatru also markedly reduced clinician-assessed disease flare-ups over 56 weeks, totaling nine with the 10mg/kg dose and 53 with the 3mg/kg dose, compared with 66 on placebo.
- Pasatru carries warnings for embryo-fetal harm, skin and soft tissue infections requiring treatment or hospitalization, and nosebleeds requiring medical intervention.
- The most common adverse reactions include nosebleeds, increased hair growth, abscess and acne.
- Pasatru is the second FDA-approved FOP therapy, following Ipsen’s Sohonos® (palovarotene), an oral retinoid approved in 2023 for the reduction in the volume of new HO lesions in adults and children aged 8 years and older for females and 10 years and older for males with FOP. It is not indicated to reduce clinician-assessed flare-ups. The labeling carries a boxed warning for embryo-fetal toxicity and premature growth plate closure.
- Incyte’s zilurgisertib, an oral activin receptor-like kinase 2 (ALK2) inhibitor, is under FDA Priority Review with approval expected by Sept. 26, 2026, for FOP. In a phase II study, it reduced the proportion of patients developing new HO lesions by 81% versus placebo at week 24.
- Regeneron is also planning OPTIMA 2, a phase III trial evaluating Pasatru in children and adolescents with FOP, which is expected to begin later in 2026.