Zilurgisertib (Atebrioz) for Fibrodysplasia ossificans progressiva (FOP)
What the FDA decided
The FDA approved Mirum Pharmaceuticals / Incyte's NDA for Zilurgisertib (Atebrioz) in Fibrodysplasia ossificans progressiva (FOP). Approved September 25, 2026 as Atebrioz, 1 day ahead of its September 26th action date, to reduce the volume of total new heterotopic ossification in adults and pediatric patients 12 and older with FOP. It is a once-daily 100 mg oral ALK2 inhibitor and the third FOP treatment, after Sohonos (2023) and Pasatru (August 2026). It carries fast track, priority review, and orphan drug designations. The label warns of fetal harm based on animal studies (patients of reproductive potential must use effective contraception; pregnant patients should discontinue and contact their provider) and of interactions with certain other medications; the most common side effects are headache, joint pain, upper respiratory tract infection, nosebleeds, and nausea. Mirum told Reuters it plans to launch in October and will announce the price then.
Who this decision matters to
Fibrodysplasia Ossificans Progressiva (FOP) is an extremely rare genetic disorder characterized by progressive heterotopic ossification, where soft tissues (muscles, tendons, ligaments) gradually transform into bone. This leads to progressive immobility and severe physical disability. FOP is caused by mutations in the ACVR1 gene, and nearly all cases involve a single mutation (c.617G>A).
Prevalence: Extremely rare, about 1 in 1 million to 1 in 2 million people worldwide. See our full Fibrodysplasia Ossificans Progressiva page for current treatments, recruiting trials, and community resources.
About the drug
Zilurgisertib: oral small-molecule inhibitor of ALK2 (ACVR1), the bone-forming receptor whose mutation is stuck in the on position in nearly all people with FOP; blocking it directly is meant to stop soft tissue from turning into bone. Our full Zilurgisertib profile covers how it works, side effects in plain language, and its trial history.
Where Fibrodysplasia Ossificans Progressiva treatment stands today
Read our full Fibrodysplasia Ossificans Progressiva treatment summary
Research in Fibrodysplasia Ossificans Progressiva is advancing through ALK2 inhibitors targeting the specific ACVR1 mutation that causes the disease, along with approaches to block BMP signaling pathways that drive abnormal bone formation. Clinical trials measure treatment success through imaging tracking ossification progression, assessments of functional mobility, and importantly, reductions in flare frequency and severity that cause pain and rapid progression.
Quality of life improvements matter significantly. Your genetic confirmation of the ACVR1 mutation guides therapy selection.
Baseline imaging documents disease extent and helps track progression. Trials track biomarkers including alkaline phosphatase that reflect ossification activity.
Pain management and reducing inflammation during flares are equally important as slowing bone formation. Your rheumatologist or genetics specialist experienced in FOP can help identify appropriate trials and discuss the exciting potential of ALK2 inhibitors.
The FDA has approved 3 medicines for FOP: Sohonos (palovarotene) capsules on August 16, 2023 for adults and for girls 8 and older and boys 10 and older, Pasatru (garetosmab) infusions on August 19, 2026 for adults, and Atebrioz (zilurgisertib) on September 25, 2026 for people 12 and older. No trial has compared them with each other, so ask your FOP specialist whether an approved medicine or a clinical trial is the better fit for you.
The Fibrodysplasia Ossificans Progressiva page has every treatment and trial →Meanwhile, 5 Fibrodysplasia Ossificans Progressiva trials are recruiting
Whatever the FDA decides here, research on Fibrodysplasia Ossificans Progressiva does not stop. A few currently enrolling studies, US sites first:
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Our coverage
Frequently asked questions
Has the FDA decided on Zilurgisertib?
The FDA has already decided. It approved the application.
Details: the outcome and what it means are at the top of this page.
Source: FDA approval notice
What was Zilurgisertib approved for?
The FDA approved Mirum Pharmaceuticals / Incyte's NDA for Zilurgisertib in Fibrodysplasia ossificans progressiva (FOP).
What to know: Approved September 25, 2026 as Atebrioz, 1 day ahead of its September 26th action date, to reduce the volume of total new heterotopic ossification in adults and pediatric patients 12 and older with FOP. It is a once-daily 100 mg oral ALK2 inhibitor and the third FOP treatment, after Sohonos (2023) and Pasatru (August 2026). It carries fast track, priority review, and orphan drug designations. The label warns of fetal harm based on animal studies (patients of reproductive potential must use effective contraception; pregnant patients should discontinue and contact their provider) and of interactions with certain other medications; the most common side effects are headache, joint pain, upper respiratory tract infection, nosebleeds, and nausea. Mirum told Reuters it plans to launch in October and will announce the price then.
How it works: Oral small-molecule inhibitor of ALK2 (ACVR1), the bone-forming receptor whose mutation is stuck in the on position in nearly all people with FOP; blocking it directly is meant to stop soft tissue from turning into bone.
More: the Zilurgisertib drug page explains it in plain language.
Is there already an FDA-approved treatment for Fibrodysplasia Ossificans Progressiva?
Yes. Trial Friend's drug list includes 3 FDA-approved drugs for Fibrodysplasia Ossificans Progressiva.
Approved: Sohonos (palovarotene), Atebrioz (zilurgisertib), Pasatru (garetosmab-grts).
Check: the Fibrodysplasia Ossificans Progressiva page also searches FDA drug labels for approved treatments.
What did the Zilurgisertib trials show?
Approval rests on Cohort 1 of the PROGRESS study (NCT05090891), which randomized 63 adolescents and adults with FOP, average age about 21, to zilurgisertib 100 mg once daily or placebo for 24 weeks, followed by an open-label extension. New bone was measured by whole-body CT. The FDA based its approval on the change in the volume of total new heterotopic ossification: at week 24 it had decreased by an average of 3.2 cubic centimeters in patients on Atebrioz and increased by 24.6 cubic centimeters on placebo, and the FDA states the effect was maintained through week 48 of the open-label extension.
More: the Zilurgisertib drug page has the full trial history and sources.
What are the side effects of Zilurgisertib?
Atebrioz can cause fetal harm, based on animal studies. Anyone who can become pregnant should use effective contraception during treatment, and should stop the drug and contact their doctor right away if pregnancy occurs (FDA).
More: the Zilurgisertib drug page lists the warnings in full.
How much will Zilurgisertib cost?
Trial Friend does not list a price for Zilurgisertib. What you pay depends on your insurance and on help from the drugmaker or a charity fund.
Find help: the patient assistance finder lists programs by insurance type.
What happens after the Zilurgisertib decision?
The FDA approved Zilurgisertib for Fibrodysplasia ossificans progressiva (FOP) on September 25, 2026.
Next steps: getting the drug still takes time. Specialty pharmacy setup, insurance review and patient assistance often take weeks. Our guide covers what families can do on day 1.
Where this date comes from
The FDA does not publish PDUFA dates; companies disclose them. This one comes from FDA approval notice. Dates can move, and the FDA can act early or late. This page rechecks against our calendar, which is re-verified daily.