8-K: Mirum Pharma's Volixibat Meets Primary Endpoint in PSC Study

Mirum Pharmaceuticals announced its investigational drug volixibat met the primary endpoint in a Phase 2b study for primary sclerosing cholangitis (PSC), showing significant improvement in pruritus.

Summary

• Mirum Pharmaceuticals announced that the VISTAS Phase 2b study evaluating volixibat, an investigational oral ileal bile acid transporter (IBAT) inhibitor, in patients with primary sclerosing cholangitis (PSC) met its primary endpoint.
• The study included 158 patients with PSC, divided into moderate to severe itch (primary analysis cohort, n=111) and mild itch (secondary analysis cohort, n=47) groups.
• Patients received either volixibat 20 mg twice daily or a placebo.
• In the primary analysis cohort, volixibat demonstrated a 2.72 point improvement in pruritus, with a placebo-adjusted difference of 1.64 points (p<0.0001) on the Adult Itch Reported Outcome (ItchRO) scale.
• Statistically significant improvements in pruritus were observed within two weeks of treatment and in the secondary cohort.
• Volixibat's safety profile was consistent with IBAT inhibition, primarily showing gastrointestinal adverse events and elevations in liver laboratory parameters.
• The company has a pre-New Drug Application (NDA) meeting with the FDA scheduled for summer 2026 and plans to submit the NDA in the second half of 2026.
• Topline data from the VANTAGE Phase 2b study of volixibat in primary biliary cholangitis (PBC) is now expected in the first quarter of 2027.

Sentiment

Score: 8

Explanation: StockSavvy.ai views this as a highly positive development, with the drug meeting its primary endpoint in a Phase 2b study and a clear regulatory path forward, indicating strong potential for future approval and market entry.

Positives

• The primary endpoint of the VISTAS Phase 2b study for volixibat in PSC was met, demonstrating a statistically significant improvement in pruritus.
• Volixibat showed a robust 2.72 point improvement in pruritus, with a placebo-adjusted difference of 1.64 points (p<0.0001) on the Adult ItchRO scale.
• Pruritus improvement was observed rapidly, within two weeks of treatment.
• The study results support the potential for volixibat to be the first treatment for cholestatic pruritus in PSC patients.
• Volixibat also demonstrated a statistically significant improvement in serum bile acid (sBA) levels, with a placebo-adjusted difference of -35.8 (p=0.0324).
• A higher percentage of patients on volixibat achieved a 2-point reduction in Adult ItchRO compared to placebo (55.6% vs 26.3%, p=0.0019).

Negatives

• Treatment with volixibat was associated with a higher incidence of treatment-emergent adverse events (TEAEs) (93.5% vs 84.0%).
• Volixibat treatment led to a higher rate of TEAEs that led to premature discontinuation from the study (9.1% vs 2.5%).
• Diarrhea was a common adverse event, occurring in 40.3% of patients on volixibat compared to 8.6% on placebo.
• Elevations in liver laboratory parameters, including ALT, AST, ALP, and bilirubin, were observed more frequently in volixibat-treated patients.
• Serious adverse events (SAEs) were reported in 10.4% of volixibat-treated patients compared to 6.2% of placebo patients.

Risks

• The safety profile of volixibat is characterized by gastrointestinal adverse events and elevations in liver laboratory parameters.
• There is a risk of serious adverse events, including cholangitis, infection, abdominal pain, and cholangiocarcinoma, although none were deemed related to volixibat in the study.
• Actual results may differ from forward-looking statements due to risks and uncertainties associated with pharmaceutical product development and the company's business.

Future Outlook

Mirum Pharmaceuticals plans to submit a New Drug Application (NDA) for volixibat in PSC in the second half of 2026, following a pre-NDA meeting with the FDA in summer 2026. Topline data from the VANTAGE Phase 2b study in PBC is anticipated in the first quarter of 2027.

Management Comments

• The VISTAS Phase 2b study results support the potential for volixibat to become the first treatment for cholestatic pruritus in patients with PSC.

Industry Context

StockSavvy.ai notes that the successful completion of a Phase 2b study and the clear path towards an NDA submission for volixibat in PSC represent a significant step forward in addressing an unmet medical need. The company's progress aligns with the broader industry trend of developing targeted therapies for rare cholestatic liver diseases.

Stakeholder Impact

• Shareholders: Positive impact due to progress towards potential drug approval and commercialization, which could increase company value.
• Patients with PSC: Potential for a new, effective treatment option for cholestatic pruritus, improving quality of life.
• Healthcare Providers: Introduction of a novel therapeutic agent for managing PSC symptoms.

Next Steps

• Present full results from the VISTAS Phase 2b study at the European Association for the Study of the Liver International Liver Congress on May 30, 2026.
• Conduct pre-NDA meeting with the FDA in summer 2026.
• Submit NDA for volixibat in PSC in the second half of 2026.
• Report topline data from the VANTAGE Phase 2b study in PBC in Q1 2027.

Key Dates

Recommendation

The company has successfully met the primary endpoint in a Phase 2b study for volixibat in PSC, a condition with significant unmet needs. The drug demonstrated statistically significant and clinically meaningful improvements in pruritus and serum bile acids, with a clear regulatory pathway and upcoming NDA submission. This positive clinical data, coupled with the potential for volixibat to be a first-in-class treatment, strongly supports a positive outlook and warrants a 'strong buy' recommendation.

Keywords

Mirum Pharmaceuticals, Volixibat, PSC, Primary Sclerosing Cholangitis, IBAT inhibitor, Pruritus, Phase 2b Study, VISTAS