MIRM · Mirum Pharmaceuticals, Inc.

The VISTAS Phase 2b results represent a pivotal clinical milestone for Mirum Pharmaceuticals, as the trial met its primary endpoint with high statistical significance (p<0.0001) in a well-defined, moderate-to-severe itch cohort of 111 PSC patients. The robust 1.64-point placebo-adjusted improvement in the Adult ItchRO scale — a patient-reported outcome validated in cholestatic liver disease — directly addresses an unmet need in PSC, where no approved therapy exists for cholestatic pruritus. The rapid onset of effect within two weeks further strengthens the clinical profile, suggesting potential for meaningful symptom relief in a population with limited options. While gastrointestinal adverse events and transaminase/bilirubin elevations were more frequent with volixibat, the safety data are consistent with the mechanism of IBAT inhibition and do not appear to preclude advancement; notably, no treatment-related deaths occurred and discontinuations due to diarrhea were low (3.9%). The regulatory path is now clearly delineated: a pre-NDA meeting with the FDA is scheduled for summer 2026, and the NDA submission is targeted for the second half of 2026 — a timeline that positions volixibat for potential approval in 2027 if the FDA review proceeds without major delays. Additionally, the upcoming VANTAGE Phase 2b data in PBC (Q1 2027) could broaden the drug’s label and commercial opportunity across cholestatic liver diseases. Collectively, these developments materially advance volixibat’s development status and significantly increase the probability of near-term regulatory and commercial inflection for Mirum.