Mirum Pharmaceuticals saw its shares rise 12% Monday after announcing that volixibat achieved the primary endpoint in the VISTAS Phase 2b study for primary sclerosing cholangitis, according to company disclosures.
The trial, which enrolled 158 patients with PSC, showed a statistically significant reduction in pruritus as measured by the Adult ItchRO instrument. The study recorded a 2.72 point reduction from baseline and a placebo-adjusted improvement of 1.64 points, with a p-value of 0.0019. The primary analysis cohort included 111 patients who met the pre-specified criteria for moderate to severe itch at baseline.
In addition to the mean score improvement, volixibat produced a higher responder rate: 55.6% of treated patients achieved at least a 2-point decrease on the Adult ItchRO scale versus 26.3% for placebo. The investigational ileal bile acid transporter inhibitor also generated a placebo-adjusted reduction of 35.8 in serum bile acids, with a reported p-value of 0.0324.
Mirum outlined next steps for the program. The company has scheduled a pre-New Drug Application meeting with the U.S. Food and Drug Administration for summer 2026 and plans to submit an NDA in the second half of 2026. Mirum also noted that full VISTAS results will be presented at the European Association for the Study of the Liver International Liver Congress on May 30. The company expects topline data from its separate VANTAGE Phase 2b study of volixibat in primary biliary cholangitis in the first quarter of 2027.
On safety, the company reported a profile consistent with the known effects of IBAT inhibition. Adverse events were dominated by gastrointestinal events and included elevations in liver laboratory parameters such as alanine aminotransferase and bilirubin. Study discontinuations due to adverse events occurred in 9.1% of volixibat-treated patients compared with 2.5% on placebo.
Market analysts reacted to the VISTAS readout. Baird analyst Brian Skorney reiterated an Outperform rating and a $112.00 price target, stating that the dataset provides a favorable setup into second-half regulatory milestones and the upcoming VANTAGE PBC topline, and that confidence in Mirum’s differentiated positioning in hepatology has been enhanced.
The VISTAS results mark a clinical milestone for a condition with no currently approved therapies for PSC. The data will be scrutinized by regulators and presented to the broader hepatology community at the May 30 congress.