Zilurgisertib for Fibrodysplasia ossificans progressiva (FOP)
The FDA is expected to decide on Zilurgisertib for Fibrodysplasia ossificans progressiva (FOP) by September 26, 2026, under a NDA from Mirum Pharmaceuticals / Incyte.
What is being decided
Mirum Pharmaceuticals / Incyte has a NDA under FDA review for Zilurgisertib in Fibrodysplasia ossificans progressiva (FOP). Oral ALK2 inhibitor under priority review for an ultra-rare disease affecting roughly 300 people in the US.
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, approximately 1 per 2 million people globally; extremely small patient population. See our full Fibrodysplasia Ossificans Progressiva page for current treatments, recruiting trials, and community resources.
What each outcome would mean
An approval starts a second race rather than ending the first one: specialty pharmacy setup, insurance review, and patient assistance typically take weeks even when everything goes right. Our guide to the 90 days after a rare disease approval explains the timeline and the moves families can make on day 1.
A complete response letter would mean the FDA declined to approve in the application's current form. CRLs are often about manufacturing or data presentation rather than efficacy, and resubmission is common. Either way, this page updates with the outcome and what it means.
Where Fibrodysplasia Ossificans Progressiva treatment stands today
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.
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:
Get notified when new fibrodysplasia-ossificans-progressiva trials open or existing trials change status, add sites, or update eligibility.
Our coverage
Frequently asked questions
When will the FDA decide on Zilurgisertib?
The FDA's target decision date (PDUFA date) for Zilurgisertib in Fibrodysplasia ossificans progressiva (FOP) is September 26, 2026, disclosed by Mirum Pharmaceuticals / Incyte. The agency can act before this date and occasionally runs past it.
What is Zilurgisertib being reviewed for?
Mirum Pharmaceuticals / Incyte submitted a NDA for Zilurgisertib in Fibrodysplasia ossificans progressiva (FOP). Oral ALK2 inhibitor under priority review for an ultra-rare disease affecting roughly 300 people in the US.
What happens after the Zilurgisertib decision?
If approved, availability is not immediate: specialty pharmacy setup, insurance review, and patient assistance typically take weeks even when everything goes right. If the FDA issues a complete response letter, the application was not approved in its current form; CRLs are often about manufacturing or data presentation rather than efficacy, and sponsors frequently resubmit. This page updates with the outcome either way.
Where this date comes from
The FDA does not publish PDUFA dates; companies disclose them. This one comes from Mirum/Incyte press release. Dates can move, and the FDA can act early or late. This page rechecks against our calendar, which is re-verified weekly.