Mirum Pharmaceuticals Announces FDA Approval of Atebrioz; AZURE-1 Phase 3 Positive

What Happened

• Mirum Pharmaceuticals (MIRM) filed an 8-K on Sept. 28, 2026 reporting two material events. On Sept. 25, 2026 the FDA approved Atebrioz™ (zilurgisertib) tablets to reduce the volume of total new heterotopic ossification (HO) in adults and pediatric patients aged 12+ with fibrodysplasia ossificans progressiva (FOP). The recommended dose is 100 mg orally once daily; Atebrioz was developed by Incyte and is licensed to Mirum for worldwide development and commercialization. Mirum expects U.S. commercial availability in October and will distribute through its Mirum Access Plus (MAP) patient support program.
• On Sept. 28, 2026 Mirum announced topline Phase 3 results from the AZURE-1 study of brelovitug for chronic hepatitis delta virus (HDV). The Phase 3 portion (n=153) met its primary endpoint at Week 24: the combined endpoint of virologic response (≥2 log10 reduction or undetectable HDV RNA) plus ALT normalization was achieved by 56% (300 mg weekly) and 45% (900 mg every 4 weeks) versus 0% in the delayed-treatment arm (p<0.0001 for both).

Key Details

• FDA approval date for Atebrioz: Sept. 25, 2026; recommended dose 100 mg once daily; U.S. commercial availability expected in October 2026.
• PROGRESS Cohort 1 efficacy for Atebrioz: mean total new HO lesion volume change at Week 24 was −3.2 cm3 (zilurgisertib) vs +24.6 cm3 (placebo); effects maintained through Week 48.
• AZURE-1 Phase 3 (n=153) Week 24 primary endpoint: 56% (300 mg QW) and 45% (900 mg Q4W) vs 0% delayed; virologic response rates were 86% and 85% respectively.
• Regulatory and commercial timing: Mirum expects to submit a BLA for brelovitug in H1 2027 with potential U.S. launch in Q4 2027; topline AZURE-4 results expected Q4 2026. Company estimates annual peak revenue potential >$1B for brelovitug (HDV) and >$200M for Atebrioz (FOP).

Why It Matters

• FDA approval of Atebrioz creates an immediate U.S. commercial pathway for a treatment addressing a rare, disabling disease (FOP) and may generate near-term product revenue when sales begin in October 2026. Mirum also highlights patient access via MAP, which could reduce out‑of‑pocket costs for eligible patients.
• Positive AZURE-1 Phase 3 results are a major clinical milestone toward regulatory approval of brelovitug for HDV; Mirum’s planned BLA submission and projected launch timelines (BLA H1 2027, potential U.S. launch Q4 2027) are key near‑term catalysts to watch. Investors should note the company’s stated revenue potential estimates and the planned release timing for additional pivotal study results.