Incyte, the Wilmington, Delaware-based biopharmaceutical company, and Mirum Pharmaceuticals, announced on September 25, 2026 that the U.S. Food and Drug Administration (FDA) has approved Atebrioz™ (zilurgisertib) tablets to reduce the volume of total new heterotopic ossification (HO) in adult and pediatric patients aged 12 and older with fibrodysplasia ossificans progressiva (FOP). Atebrioz was developed by Incyte and licensed to Mirum for worldwide development and commercialization. With the approval, the FDA also issued Incyte a Rare Pediatric Disease Priority Review Voucher, which can be used for a later drug application that would not otherwise qualify for priority review.
“Today marks an important milestone for people living with FOP, bringing a new treatment option to adult and pediatric patients living with this devastating disease,” said Chris Peetz, Chief Executive Officer at Mirum. “At Mirum, we are driven to serve rare disease communities where the unmet need is significant and the opportunity to make a difference is profound. The approval of Atebrioz reflects what can be achieved when industry, researchers and patient communities work together, and we remain committed to fostering that spirit of collaboration in FOP.”
Targeting the Root of a Rare Disease
FOP is an ultra-rare, progressive genetic disease affecting approximately 300 people in the U.S. and 900 worldwide. In people with FOP, variants in the ACVR1 gene abnormally activate ALK2, causing bone to form in muscles, tendons, ligaments, and other soft tissues. As these HO lesions accumulate, they progressively restrict movement and can lead to significant disability, with symptoms typically appearing in early childhood. Atebrioz is a once-daily oral ALK2 inhibitor designed to target that disease-driving pathway.
“For families living with FOP, having additional treatment options means having greater flexibility in managing a complex, lifelong disease,” said Michelle Davis, Executive Director at the International Fibrodysplasia Ossificans Progressiva Association (IFOPA). “Every person’s experience with FOP is different, and expanding treatment options gives patients, families and their physicians the opportunity to consider what may be right for their individual needs.”
The Data Behind the Approval
The approval was based on Cohort 1 of the global Phase 2 PROGRESS study, which randomized 63 patients aged 12 and older to zilurgisertib 100 mg once daily or placebo. At Week 24, mean total new HO lesion volume decreased by 3.2 cm³ in patients receiving zilurgisertib, compared with an increase of 24.6 cm³ in patients on placebo, and treatment effects were maintained through Week 48 of the open-label extension. Zilurgisertib was generally well tolerated. The most common side effects were headache, joint pain, upper respiratory tract infection, nosebleed, and nausea; most were mild or moderate, and none led to treatment discontinuation or dose reduction.
“FOP is a lifelong disease in which the accumulation of HO leads to increasing disability and loss of function,” said Robert Pignolo, M.D., Ph.D., Robert and Arlene Kogod Professor of Geriatric Medicine at the Mayo Clinic College of Medicine and lead investigator for the PROGRESS study. “Having another treatment option is meaningful in a progressive disease like FOP, particularly for adolescents who may be earlier in the course of their disease.”
Access and What’s Next
Atebrioz is expected to be commercially available in the U.S. in October through Mirum Access Plus (MAP), a patient support program offering insurance and access support, financial assistance, and educational resources, with eligible patients paying as little as $0 per month. In the European Union, a marketing authorization application for zilurgisertib is under review by the European Medicines Agency. The PROGRESS pediatric program continues, with enrollment complete in Cohort 2 (children aged 6 to under 12) and underway in Cohort 3 (children aged 2 to under 12).
About Incyte
Incyte is a Wilmington, Delaware-based biopharmaceutical company with an established portfolio of first-in-class medicines and a pipeline of next-generation medicines across hematology, oncology, and inflammation and autoimmunity.
About Mirum Pharmaceuticals
Mirum Pharmaceuticals is a rare disease company focused on rare liver and rare genetic diseases. Its commercial portfolio includes LIVMARLI® (maralixibat), Atebrioz™ (zilurgisertib), CHOLBAM® (cholic acid), and CTEXLI® (chenodiol).
