Volixibat

In PSC and PBC, bile does not drain normally from the liver, and bile acids build up in the blood and liver, which is linked to the itch many patients have. Bile acids are normally reabsorbed in the last part of the small intestine through a pump called the ileal bile acid transporter (IBAT) and sent back to the liver. Mirum describes volixibat as a minimally absorbed pill designed to block IBAT, so bile acids are not recycled and levels fall in the body and liver^[8].

Livmarli (maralixibat), another Mirum medicine, uses the same approach in people with Alagille syndrome (3 months and older) and PFIC (12 months and older). The studies' main goal is itch. They also look at possible effects on disease progression, and no result on that has been reported^[1][2].

VISTAS (NCT04663308) is a Phase 2b, double-blind, placebo-controlled study of itch in PSC. ClinicalTrials.gov lists 182 people enrolled, aged 12 and older where allowed and 18 and older elsewhere, with 34 US sites^[1], and Mirum's results cover 158 people with PSC, 111 of them with moderate to severe itch^[5]. Its main measure was the Adult ItchRO, a daily itch score from 0 (no itch) to 10 (worst itch).

Among 111 people with moderate to severe itch, itch fell by 2.72 points on volixibat 20mg twice a day against 1.08 on placebo, and 55.6% against 26.3% had a drop of at least 2 points. Serum bile acids fell on volixibat and did not on placebo^[5]. Mirum reported in May 2026 a trend toward better sleep scores and no statistically significant change in fatigue^[6].

VANTAGE (NCT05050136) is the matching Phase 2b study in PBC, with 333 adults enrolled and 44 US sites; it is no longer recruiting, and Mirum expects topline results in the first quarter of 2027^[2][8].

Volixibat has no FDA label, so its side effects are not settled. In VISTAS, adverse events of any kind were reported by 93.5% of people on volixibat and 84.0% on placebo, and serious adverse events by 10.4% and 6.2%; Mirum said none of the serious events on volixibat were related to the drug. Side effects led 9.1% on volixibat to leave the study against 2.5% on placebo, including 3.9% for diarrhea against 1.2%.

Liver test elevations (ALT, AST, ALP and bilirubin) were more common on volixibat^[5]. In an early look at the PBC study VANTAGE, 77% reported diarrhea, all mild to moderate and mostly short-lived, according to Mirum^[4].

Volixibat was first tested under the code SHP626 in nonalcoholic steatohepatitis (NASH), in a trial stopped early in July 2018^[3]. Mirum now sponsors every volixibat study. The FDA granted Breakthrough Therapy designation for cholestatic itch in PSC and in PBC, and Orphan Drug designation for PSC, according to Mirum^[7]. Mirum reported in May 2026 that VISTAS met its primary endpoint^[5].

In August 2026 Mirum said the FDA had recommended a Phase 3 study at the pre-NDA meeting, and that it would hold more discussions with the FDA before a possible application based on VISTAS in the first half of 2027^[7]. No application had been submitted as of November 10, 2026.