Mirum Pharmaceuticals and Incyte Announce Positive Pivotal Phase 2 Results from PROGRESS Study of Zilurgisertib in Fibrodysplasia Ossificans Progressiva

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- Cohort 1 results presented at ENDO 2026 demonstrate meaningful reductions in total heterotopic ossification (HO) lesion volume, new HO lesions and flare activity in adolescents and adults with FOP - U.S. Food and Drug Administration (FDA) accepted the New Drug Application (NDA) for zilurgisertib in FOP under Priority Review FOSTER CITY, Calif. & WILMINGTON, Del. --(BUSINESS WIRE)-- Mirum Pharmaceuticals, Inc. (Nasdaq:MIRM) and Incyte (Nasdaq:INCY) today announced pivotal Phase 2 results from Cohort 1 of the PROGRESS study evaluating zilurgisertib, an investigational oral activin receptor-like kinase 2 (ALK2) inhibitor, in adolescents and adults (≥12 years of age) with fibrodysplasia ossificans progressiva (FOP). Results were shared in a late-breaking rapid-fire presentation at ENDO 2026, the Endocrine Society’s annual meeting. This press release features multimedia. View the full release here: https://www.businesswire.com/news/home/20260614539468/en/ Results from Cohort 1 of the PROGRESS study demonstrated a consistent treatment effect across measures of disease activity and durability through Week 48. During the open-label extension, no new HO lesions were observed among patients who continued to receive zilurgisertib or among placebo-treated patients who crossed over to active treatment at Week 24. "The findings presented at ENDO represent an important milestone for the zilurgisertib program and further strengthen the growing body of clinical evidence supporting its potential as a treatment for FOP," said Steven Stein , M.D., Executive Vice President, Chief Medical Officer and Head of Late-Stage Development at Incyte . "People living with FOP and their families urgently need additional treatment options," said Joanne Quan , M.D., Chief Medical Officer at Mirum Pharmaceuticals . "These results reinforce our confidence in the potential of zilurgisertib and our commitment to working with Incyte to bring this important program forward as we prepare for potential commercialization and support the FOP community." Cohort 1 of the PROGRESS study evaluated zilurgisertib 100 mg once-daily in 63 adolescents and adults (≥12 years of age) with FOP. Patients were randomized 1:1 to receive zilurgisertib (n=32) or placebo (n=31) during a 24-week, placebo-controlled, double-blind period, followed by an open-label extension period. Baseline demographics and disease characteristics were generally balanced between treatment groups, with a mean age of approximately 21 years and evidence of recent disease activity prior to enrollment. A total of 61 patients had 48-week whole-body CT scan data available at the time of the open-label extension analysis. Key efficacy findings included: Fewer patients receiving zilurgisertib developed new HO lesions at Week 24, with an 81% reduction versus placebo (p=0.0986). 99.9% reduction in total volume of new HO lesions in patients receiving zilurgisertib versus placebo at Week 24 (nominal p-value

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