A medicine that has been used for liver conditions for more than 30 years is now being tested as a possible way to slow Parkinson’s disease. It is being added to a UK trial that its organisers describe as the world’s largest trial of treatments for the condition1. The drug is ursodeoxycholic acid, usually shortened to UDCA. Researchers at Sheffield Teaching Hospitals NHS Foundation Trust and the University of Sheffield identified it as a promising candidate1.
The trial is called the Edmond J Safra Accelerating Clinical Trials in Parkinson’s Disease trial, or EJS ACT-PD. UDCA becomes its third active treatment. The first two were telmisartan and terazosin1. Each drug is tested against a placebo, a dummy treatment that looks the same but contains no medicine1.
What happened
The Sheffield hospital trust announced on 5 November 2026 that UDCA is being included in EJS ACT-PD1. The trial plans to recruit 2,000 participants from 40 NHS hospital sites, including Sheffield’s Royal Hallamshire Hospital1. It is led nationally by researchers at University College London (UCL) and Newcastle University, and is run by UCL’s Innovative Clinical Trials Unit1.
UDCA needs to be taken on a different schedule from the two drugs already in the trial. Because of this, people who join from now on will be placed at random into one of five groups: UDCA, telmisartan, terazosin, or one of two placebo groups. Which groups a person can join depends on what they are eligible for1. While the trial is running, neither the volunteers nor the study team know who is getting which drug or the placebo1. This setup is called “double-blind”. It helps stop expectations from colouring the results.
Why researchers picked a liver drug
Parkinson’s is the second most common disease of nerve-cell loss worldwide. It affects about 1% of people over 602. Today’s medicines can ease movement symptoms. But according to the researchers who designed this trial, there are currently no registered treatments that change the course of the disease itself3.
The Sheffield team’s idea centres on mitochondria, the tiny “power plants” inside cells1. In Parkinson’s, the nerve cells that make dopamine sit in a part of the brain that controls movement. When their mitochondria stop working properly, this is believed to play an important role in how the disease gets worse1. The researchers believe UDCA could protect these nerve cells by improving how their mitochondria work, and so slow the disease1.
The drug came out of a search through an entire library of existing medicines. The University of Sheffield-led team tested it on tissue samples from people with Parkinson’s, the first time a full drug library had been screened this way1. Parkinson’s UK funded that first screen1. Professor Oliver Bandmann led the drug’s development. He is a movement-disorders neurologist at the University of Sheffield and Sheffield Teaching Hospitals1. He said:
“Our research began with the first systematic screening of an entire library of compounds in tissue from people with Parkinson’s disease at the Sheffield Institute for Translational Neuroscience (SITraN). This identified UDCA, an existing medication for liver disease, as a promising candidate for protecting nerve cells by improving mitochondrial function.”1
The evidence so far
After the lab work, the team ran an early-stage, proof-of-concept trial in people with Parkinson’s, called the UP study1. According to the Sheffield announcement, it showed the drug was safe and well tolerated in people with Parkinson’s1. The announcement also describes UDCA as “safe and effective for use in Parkinson’s patients” in that study, but adds that “large-scale testing is now needed to assess effectiveness further”1.
UDCA did not get into the big trial on the Sheffield findings alone. The trial’s organisers published how they chose their drugs in the journal Movement Disorders in 20253. A working group gathered candidates from published research, a related Cure Parkinson’s programme and suggestions from experts3. It sorted them into five groups by how they might work. One of those groups was drugs that target mitochondria3. Experts then scored each candidate on lab, drug and clinical evidence. People with Parkinson’s gave feedback throughout the process3.
Out of 293 possible treatments, 52 passed a first screen and were scored. Detailed files on the 14 highest-ranked were sent to the trial’s steering committee3. Telmisartan, terazosin and UDCA were chosen as the first three treatments3. Oliver Bandmann, Tom Foltynie and Camille Carroll, who now co-lead the UDCA arm, are among the paper’s authors31.
What it does not show yet
Being added to a trial is not a result. No data from EJS ACT-PD on UDCA have been reported. The trial exists to answer the open question: does the drug actually slow Parkinson’s in a large group of people, compared with a placebo1?
The case for UDCA so far comes from two kinds of work. The first is lab tests on patient tissue, which can point to a possible effect but cannot show what happens in a living person’s brain1. The second is the early-stage UP study, which the Sheffield team describes as showing the drug was safe and well tolerated1. The idea that UDCA protects nerve cells by helping their mitochondria is what the researchers “believe”. It has not yet been shown to change the course of the disease1.
Who is behind it and who pays
EJS ACT-PD is sponsored by University College London1. It is funded by the Efficacy and Mechanism Evaluation Programme, a partnership of the UK’s MRC and NIHR research funders, along with Cure Parkinson’s, The Michael J Fox Foundation, Parkinson’s UK, The John Black Charitable Foundation, The Gatsby Charitable Foundation and Van Andel Institute1. The UP study was co-funded by the Jon Moulton Charity Trust and Cure Parkinson’s, with strong support from the NIHR Biomedical Research Centre Sheffield1.
Bandmann led both the original drug discovery work and the UP study, the latter together with Foltynie1. He will now co-lead the UDCA part of the big trial with Foltynie at UCL and Carroll at Newcastle University1. The same researchers who found the drug are therefore helping to test it. This is common in academic research, and the double-blind design is meant to guard against bias. The sources do not mention any drug company involvement.
How it fits the field
EJS ACT-PD is a “multi-arm, multi-stage” trial. It tests several treatments against one shared placebo group and drops ones that are not working early, so new ones can take their place3. The aim is to test more drugs faster and more efficiently than separate trials could1. UDCA’s arrival as the third drug is described by the trial’s backers as an important milestone for this approach1.
The Sheffield team also points out that it is rare for a drug discovery programme led by universities to go from a lab finding, through a phase 2 trial with a novel design, to what they call a “definitive phase 3 trial”, the last big test of whether a treatment works1. Bandmann said the UDCA arm marks the result of more than a decade of research in Sheffield1. Reusing a medicine already approved for something else, as here, means a lot is already known about its safety from years of use1.
What to watch next
- Recruitment: how quickly the trial reaches its 2,000 planned participants across 40 NHS sites1.
- Interim decisions: because the trial can drop treatments that are not working early, any of the three drugs could be stopped or carried forward along the way3.
- Final results: whether UDCA slows Parkinson’s compared with a placebo. That is the question the early-stage UP study could not answer1.
For now, the facts are these. A long-used liver drug, picked by screening medicines on patient tissue and found safe and well tolerated in an early-stage, proof-of-concept study, has moved into a large controlled trial1. Whether it slows the disease is still unknown.
