FOP Now Has Three Approved Drugs for About 300 US Patients, Two of Them in 37 Days

The FDA approved Atebrioz (zilurgisertib), an oral once-daily ALK2 inhibitor from Mirum Pharmaceuticals and Incyte, on 25 September 2026, to reduce the volume of new heterotopic ossification in patients aged 12 and older with fibrodysplasia ossificans progressiva (FOP). Incyte developed the drug and licensed worldwide rights to Mirum.
In Cohort 1 of the Phase 2 PROGRESS study, 63 patients were randomised 1:1. At week 24, mean new bone volume fell by 3.2 cm³ on zilurgisertib and rose by 24.6 cm³ on placebo, with effects maintained to week 48. No adverse events led to discontinuation or dose reduction.
FOP affects about 300 people in the US and 900 worldwide. Regeneron’s Pasatru (garetosmab), an Activin A antibody for adults, was approved on 19 August 2026, and Ipsen’s Sohonos (palovarotene) in 2023.
Incyte received a Rare Pediatric Disease Priority Review Voucher. Atebrioz launches in October through Mirum Access Plus, with eligible patients paying as little as $0 a month, and an EU application is under EMA review.

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Three drugs now divide an ultra-rare disease by mechanism, route and age, and the newest one competes on convenience and safety.

Each drug owns a different patient. Sohonos, a retinoid, starts at age 8 for girls and 10 for boys and carries a boxed warning for embryo-fetal toxicity and premature growth-plate closure. Pasatru is an intravenous antibody given every four weeks to adults. Atebrioz is a daily tablet from age 12, with an embryo-fetal warning but no boxed warning in the release.
The evidence is not comparable. Atebrioz rests on a 24-week Phase 2 measuring lesion volume; Pasatru on a 56-week Phase 3 in adults that cut new lesions by 90% or more; Sohonos on a single-arm study against natural history. Prescribers will be choosing across trials that never met.
Europe is the open market. The European Commission declined to authorise palovarotene in 2023, and zilurgisertib is now under EMA review. With a second priority review voucher issued in FOP, the small US population is also being monetised through tradeable vouchers, not only through sales.