Mirum and Incyte Win FDA Approval for Atebrioz (Zilurgisertib) in Rare Bone Disease FOP

The U.S. Food and Drug Administration approved Atebrioz (zilurgisertib) on September 25, 2026, a win for MIRM and INCY. The drug is indicated to reduce the volume of new heterotopic ossification in adults and pediatric patients 12 years and older with fibrodysplasia ossificans progressiva (FOP), a rare genetic disease in which muscle, tendons and ligaments gradually turn into bone.

Incyte developed zilurgisertib and licensed it to Mirum Pharmaceuticals for worldwide development and commercialization. Alongside the approval, the FDA issued a Rare Pediatric Disease Priority Review Voucher to Incyte, not Mirum. The drug is a once-daily oral activin receptor-like kinase 2 (ALK2) inhibitor, dosed at 100 mg, that targets abnormal ALK2 activation caused by ACVR1 gene variants.

Approval rests on the PROGRESS study, which randomized 63 patients. At Week 24, new bone volume fell by 3.2 cm³ on zilurgisertib versus a 24.6 cm³ increase on placebo. The FDA granted fast track, priority review and orphan drug designations, and noted that Atebrioz can cause fetal harm based on animal studies. The agency describes it as the third approved FOP treatment.

What to watch: the U.S. commercial launch expected in October 2026, uptake through Mirum's patient access program, and how Incyte uses or monetizes the priority review voucher.