Results from Phase 2b Clinical Trial for Volixibat to Treat Itch in PSC

On May 4, 2026, Mirum Pharmaceuticals issued a press release announcing the results from the Phase 2b VISTAS study for volixibat to treat pruritus (itch) in people living with primary sclerosing cholangitis (PSC). The study achieved its primary endpoint of meaningful improvement in patient-reported itch scores for those receiving volixibat.

Volixibat is an ileal bile acid transporter (IBAT) inhibitor that blocks the reabsorption of bile acids in the small intestine so that less bile acids return to the liver. In PSC, this may be beneficial to reduce the overall bile acid levels and bile acid toxicity in the liver and blood. This reduction in bile acids may therefore reduce itching associated with cholestasis in PSC. In other cholestatic diseases, other IBAT inhibitors have been effective and approved for treating itch.

Ricky Safer, founder and CEO of PSC Partners Seeking a Cure, is quoted in the release: “After decades of commitment from patients, families and researchers participating in PSC studies, these results represent real hope for what could become the first approved treatment. For many patients, the itch associated with PSC is constant and deeply disruptive – affecting sleep, daily activities and overall quality of life. Seeing meaningful progress in reducing this burden is incredibly encouraging for a community that has long had limited options.”

Mirum also announced that they will have a pre-New Drug Application (NDA) meeting with the FDA in summer 2026, and plan to submit an NDA for volixibat in the second half of 2026. If submitted and if approved (which typically takes about a year) according to this schedule, volixibat could be available to U.S. patients in 2027 or early 2028.

Key Study Results:

A total of 158 people with PSC-related itch participated in the VISTAS study, with 77 receiving volixibat and 81 receiving placebo. The primary study endpoint was to measure change in the Adult ItchRO, a 0-10 scale for measuring itch (0 = no itch, 10 = worst itch imaginable). Patients with moderate to severe itch accounted for 70% of the participants and were the primary focus of the study. In this subgroup, those receiving volixibat reported a -2.72 point average reduction on the ItchRO scale, compared to -1.08 on placebo. Additionally, 55% of these participants receiving volixibat reported a 2 point or greater reduction on the Adult ItchRO scale (26% in placebo).

Participants receiving volixibat also saw a reduction on average in serum bile acids, which are a potentially contributing factor in PSC-related itch.

The study showed a favorable safety profile for volixibat, with a comparable overall rate of major adverse events in the treatment cohort vs. placebo. Higher rates of gut-related adverse events (diarrhea, nausea, and abdominal pain) were seen in those receiving volixibat. Additionally, more participants receiving volixibat saw an increase in ALT, AST, ALP, and/or bilirubin levels in bloodwork.

This marks the first successful late-stage clinical trial in the U.S. for new potential treatments for PSC, a major milestone for the community.

Full presentation slides are available on the Mirum website. More detailed results will be presented at the annual EASL Conference on May 27, 2026. We will continue to share updates as they become available.

Read Mirum Press Release