A new clinical trial update has brought encouraging news for the primary sclerosing cholangitis (PSC) community, particularly for those living with the severe, disruptive symptom of cholestatic pruritus (itch).

On 4 May 2026, Mirum Pharmaceuticals announced positive topline results from its global VISTAS Phase 2b clinical trial. The study looked at a medication called volixibat, which is designed to target and lower the build-up of bile acids that can cause severe itching in people with PSC.

Currently, there are no approved, PSC-specific therapies available to treat this condition or its symptoms. For many people, PSC itch is constant, deeply distressing, and profoundly impacts sleep, work, and overall quality of life.

What is volixibat and how does it treat primary sclerosing cholangitis itch?

Volixibat is an experimental tablet that aims to stop bile acids from building up in the body. It works in the gut to block the body from recycling these acids, allowing them to be passed out naturally instead of entering the bloodstream. This helps reduce the severe liver-related itch that many people with PSC experience.

What were the key findings from the VISTAS Phase 2b trial?

The VISTAS trial looked at 158 adults with PSC. Researchers focused mostly on a group of 111 people who had moderate-to-severe itching when the study started. These participants tracked their itch every day on a 0-to-10 scale (0 = no itch; 10 = worst itch imaginable). They were split into two groups: one group took 20 mg of volixibat twice a day, and the other group took a placebo (an inactive, dummy tablet).

The main results showed:

• Significant Itch Reduction: People taking volixibat saw their itch scores drop by an average of 2.72 points, compared to a 1.08-point drop for those on the placebo. This means volixibat gave a clear, noticeable improvement compared to the dummy tablet.
• High Success Rate: More than half of the participants taking volixibat (55.6%) saw their daily itch scores drop by 2 points or more, compared to just over a quarter (26.3%) in the placebo group.
• Fast Relief: Patients and researchers noticed that the itching began to improve as early as one to two weeks after starting the treatment.
• Benefits for Mild Itch: The treatment also showed significant reduction in itch for a separate group of 47 participants who only had mild itching when they joined the study.

Does volixibat slow down or reverse underlying liver disease?

No, early findings suggest that volixibat helps control symptoms rather than treating the underlying disease. While this is a major milestone for managing daily symptom burden, we do not yet know if volixibat can slow down, stop, or reverse liver damage, bile duct narrowing, or scarring. To read about the charity's wider work to find disease-altering treatments, view our strategy.

What are the side effects and safety profile of volixibat?

The trial showed that volixibat’s side effects were typical for this type of medication, mostly causing stomach issues and temporary changes in routine liver blood tests (such as ALT and bilirubin levels).

The specific safety details from the study include:

• Overall Side Effects: Side effects occurred in 93.5% of people taking volixibat, compared to 84.0% of those taking the placebo. More severe side effects occurred in 13.0% of the volixibat group and 11.1% of the placebo group.
• Leaving the Trial Early: In total, 9.1% of patients in the volixibat group had to stop the trial early because of side effects, compared to 2.5% in the placebo group.
• Stomach Issues: Diarrhoea caused 3.9% of the volixibat group to drop out of the study, compared to 1.2% in the placebo group. 
• Serious Illnesses: Serious health events happened in 10.4% of volixibat patients and 6.2% of placebo patients. These included issues like bile duct infections (cholangitis), general infections, stomach pain, bile duct changes, and fever. Importantly, doctors determined that none of these serious events were caused by the medication itself, and there were zero deaths in the trial.

These types of side effects are a known feature of how this medicine works. 

What are the next steps for volixibat approval?

Mirum Pharmaceuticals is engaging with regulatory authorities. The company hopes to submit an official application for regulatory approval in the second half of 2026 in the US to help bring this treatment to clinics.

The full scientific details, which will give a closer look at the drug's safety and long-term effectiveness, will be presented at the European Association for the Study of the Liver (EASL) International Liver Congress on 30 May 2026.

I am on the Open Label Extension - what will happen to me?

Mirum Pharmaceuticals have reassured us that participants on the trial who are still taking volixibat (as part of their Open Label Extension phase) will continue to have access to the medication while the company engages with regulatory authorities. 

PSC Support is the only patient organisation in the UK dedicated to helping people affected by PSC. We will monitor these updates closely and share what we learn from the medical congress.