Mirum Pharmaceuticals Announces Key Phase 2 Results from Cohort 1 of the PROGRESS Study. The study assessed zilurgisertib, an investigational oral activin receptor-like kinase 2 (ALK2) inhibitor. It focused on patients 12 years of age and older, including adolescents and adults, with Fibrodysplasia Ossificans Progressiva treatment. The companies shared the results in a late-breaking rapid-fire session at ENDO 2026, the Endocrine Society’s annual meeting.
The results of the PROGRESS study showed a consistent treatment effect across the measures of disease activity. The findings also demonstrated durability through Week 48. No new heterotopic ossification (HO) lesions were observed in the open-label extension period for patients who continued to receive zilurgisertib. Similar results were seen in 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.”
PROGRESS Study Evaluates Zilurgisertib in FOP Patients
Cohort 1 of the PROGRESS study evaluated a 100 mg once-daily dose of zilurgisertib in 63 adolescents and adults with FOP. Patients were randomly assigned in a 1:1 ratio to receive either zilurgisertib or placebo during a 24-week, placebo-controlled, double-blind treatment period. The study included 32 patients receiving zilurgisertib and 31 patients receiving placebo. After this period, participants entered an open-label extension phase. Baseline demographics and disease characteristics remained generally balanced between both groups. The average patient age was approximately 21 years.
Participants also showed evidence of recent disease activity before enrollment. At the time of the open-label extension analysis, 61 patients had available 48-week whole-body CT scan data. The Phase 2 FOP treatment study reported several important efficacy outcomes. Patients receiving zilurgisertib showed fewer new HO lesions at Week 24, with an 81% reduction compared with placebo (p=0.0986). Zilurgisertib demonstrated a 99.9% reduction in the total volume of new HO lesions compared with placebo at Week 24 (nominal p-value<0.0001).
Patients receiving zilurgisertib experienced a reduction in total existing HO lesion volume. Meanwhile, placebo-treated patients showed an increase at Week 24 (nominal p-value=0.004). Among patients who continued receiving zilurgisertib, no new HO lesions appeared between Week 24 and Week 48.
Total HO lesion volume continued to decrease among patients receiving ongoing zilurgisertib treatment. Patients who switched from placebo to zilurgisertib also showed no new HO lesions. Furthermore, their total HO lesion volume decreased from Week 24 to Week 48.
Zilurgisertib Safety Profile in Phase 2 Trial
Zilurgisertib demonstrated a generally well-tolerated safety profile during the 24-week placebo-controlled period. The study reported that most adverse events were mild or moderate in severity. Additionally, no adverse events resulted in treatment discontinuation or dose reduction. Serious adverse events and Grade ≥3 adverse events occurred at low rates across both treatment groups.
The most commonly reported adverse events among patients receiving zilurgisertib included:
- FOP flare-up or aching/pain associated with FOP (25%)
- Headache (21.9%)
- Upper respiratory tract infection (21.9%)
- Arthralgia (18.8%)
- Epistaxis (12.5%)
- Nausea (12.5%)
The latest Phase 2 results strengthen the clinical development program for zilurgisertib. Moreover, Mirum Pharmaceuticals and Incyte continue advancing efforts to develop potential treatment options for people living with fibrodysplasia ossificans progressiva.
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News Source: Businesswire.com
