Mirum Pharmaceuticals has reported that its VISTAS Phase IIb clinical study of volixibat, an investigational oral ileal bile acid transporter inhibitor, has achieved its primary goal in patients with primary sclerosing cholangitis (PSC).
The placebo-controlled, double-blind, randomised, global trial enrolled 158 patients with PSC.
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They were allocated to two cohorts based on baseline itch severity: a primary cohort with moderate to severe itch comprising 111 patients and a secondary cohort with mild itch comprising 47 patients.
The patients received volixibat 20mg twice daily or placebo, with the endpoint assessed in the primary cohort.
Volixibat showed a 2.72-point improvement in pruritus in the primary analysis cohort, with a placebo-adjusted difference of 1.64 points on the adult itch reported outcome (ItchRO) scale.
Improvements were observed as early as two weeks, and similar results were noted in the secondary cohort.
The main adverse events for volixibat were gastrointestinal and included increased liver laboratory parameters, such as alanine aminotransferase and bilirubin.
The safety profile matched the known effects of ileal bile acid transporter (IBAT) inhibition in both primary and secondary cohorts.
Mirum has scheduled a pre-new drug application (NDA) meeting with the US Food and Drug Administration (FDA) in mid-2026 and plans to submit the NDA later this year.
Mirum Pharmaceuticals chief medical officer Joanne Quan said: “These results mark an important milestone for the PSC community, where there are currently no approved therapies. In a disease that has been historically difficult to study and treat, VISTAS delivered a clear and compelling efficacy signal.
“The observed statistically significant and clinically meaningful reductions in pruritus demonstrate the potential for volixibat to address one of PSC’s most burdensome and defining symptoms.”
Full VISTAS Phase IIb results will be presented at the European Association for the Study of the Liver International Liver Congress on 30 May.
The therapy is currently being evaluated in Phase IIb trials for PSC (VISTAS study) and primary biliary cholangitis (PBC) (VANTAGE study).
Top line data from the VANTAGE Phase IIb study of volixibat in PBC are expected in the first quarter of 2027.
PSC is a rare, long-term disease characterised by inflammation, scarring, and gradual narrowing of the bile ducts both within and outside the liver.
In March 2026, Mirum completed enrolment in the Phase III EXPAND study assessing Livmarli (maralixibat) for patients aged six months and above with cholestatic pruritus linked to rare cholestatic liver diseases, including biliary atresia.
