Atebrioz (zilurgisertib) approved for fibrodysplasia ossificans progressiva aged 12+
FDA approved zilurgisertib (Atebrioz; Mirum Pharmaceuticals / Incyte), an ALK2 inhibitor, to reduce new heterotopic ossification in patients aged 12 years and older with FOP. In the PROGRESS trial, mean new lesion volume decreased by 3.2 cm³ with zilurgisertib vs an increase of 24.6 cm³ on placebo at week 24.
Atebrioz (zilurgisertib) ↗, developed by Mirum Pharmaceuticals and Incyte, was approved by FDA on 25 September 2026 for patients aged 12 years and older with fibrodysplasia ossificans progressiva (FOP). It is the second approved therapy for FOP, joining palovarotene (Sohonos).
About fibrodysplasia ossificans progressiva
FOP ↗ is an ultra-rare autosomal dominant disorder caused by a gain-of-function mutation in the ACVR1 gene, which encodes ALK2 (activin receptor-like kinase 2). Affected individuals progressively develop heterotopic ossification — bone forming in muscles, tendons, and ligaments outside the skeleton — leading to irreversible loss of mobility. Global prevalence is approximately 1 in 2 million. There is no cure, and flare-ups can be triggered by trauma, infection, or intramuscular injections.
Evidence: PROGRESS trial
The approval was based on the PROGRESS randomised controlled trial. The primary endpoint was total new heterotopic ossification (HO) lesion volume measured by whole-body low-dose CT at week 24. Patients receiving zilurgisertib had a mean decrease of 3.2 cm³ in new HO volume, versus a mean increase of 24.6 cm³ in the placebo group. The recommended dose is 100 mg orally once daily. Trial registry: NCT04577820 ↗.
Mechanism
Zilurgisertib is a selective ALK2 inhibitor. By blocking constitutively active ALK2/BMPR1A signalling caused by the R206H mutation, it reduces the aberrant BMP (bone morphogenetic protein) pathway activation that drives heterotopic ossification. For a mechanistic review see Kaplan et al., Bone (NCBI) ↗.
FAQ
What does FDA approval mean?
FDA approval means the agency has determined, based on scientific evidence submitted by the manufacturer, that a drug's benefits outweigh its known risks for a specific indication and patient population. The review process includes evaluation of clinical trial data, manufacturing quality, and proposed labelling. See the FDA drug approval process overview ↗.
Does approval mean the drug is available immediately?
Not always. Commercial launch timelines depend on manufacturing scale-up, pricing, and distribution. REMS-restricted drugs ↗ require prescriber or pharmacy enrolment before the product can be dispensed. Rare disease drugs may also have limited initial supply. Check the manufacturer's website or RxNav ↗ for availability status.