A liver drug picked for protecting mitochondria joins the world's largest Parkinson's trial
Edited by Samael A. Tejada, Founder & Editor-in-Chief
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UDCA, a long-used liver drug identified in patient-tissue screening as a protector of mitochondrial function, has joined the EJS ACT-PD platform trial as its third active arm, to be tested against placebo in 2,000 participants at 40 UK hospital sites (announced November 6, 2026). An earlier study showed it was safe and well tolerated in Parkinson's; whether it slows the disease is exactly what this phase 3 trial has not yet answered.
Most Parkinson's drugs manage symptoms. This one was chosen, from a screen of an entire drug library in patients' own tissue, for a different job: keeping the mitochondria of dopamine neurons working.
How was UDCA chosen?
The Sheffield team screened an entire library of compounds in tissue from people with Parkinson's disease — a first for the field — and UDCA emerged as a promising candidate for protecting nerve cells by improving mitochondrial function. Lead researcher Professor Oliver Bandmann, who will co-lead the UDCA arm with Professor Tom Foltynie (UCL) and Professor Camille Carroll (Newcastle), describes the arc as rare for an academically led program: from laboratory discovery through a proof-of-concept trial to a definitive phase 3 evaluation.
What will the trial do?
EJS ACT-PD is a multi-arm platform designed to test more drugs faster: new participants will be randomly assigned to one of five groups — the three active treatments (UDCA, telmisartan, terazosin) or two placebo groups, depending on eligibility — with neither participants nor the study team knowing assignments. UDCA was selected after an extensive review of hundreds of potential therapies by scientific experts and people with Parkinson's, and it was strongly supported by the NIHR Biomedical Research Centre Sheffield.
What is already known — and what is not?
Known: UDCA's safety record over 30-plus years of liver use, and its tolerability in Parkinson's patients in the UP study, which also provided encouraging evidence on brain energy metabolism. Not known: whether any of that translates into slower progression. Mitochondria-protective candidates have a long history of promising early signals that large trials did not confirm — which is precisely why a 2,000-person placebo-controlled test, rather than another small study, is the right next step.
Frequently asked questions
What is UDCA?
Ursodeoxycholic acid, a drug used for over 30 years for certain liver conditions. Sheffield researchers identified it in patient-tissue screening as a candidate for improving mitochondrial function in Parkinson's disease.
What is the EJS ACT-PD trial?
The Edmond J Safra Accelerating Clinical Trials in Parkinson's Disease platform, led by UCL and Newcastle University, recruiting 2,000 participants across 40 NHS sites to test multiple candidate disease-modifying drugs in parallel against placebo. UDCA is its third active arm.
Has UDCA been shown to slow Parkinson's?
No. An early-stage study showed it was safe and well tolerated, with encouraging signals on brain energy metabolism. Slowing progression is the unproven question the phase 3 trial is designed to answer.
Where the evidence stands
- Established: Loss of mitochondrial function in dopamine-producing neurons is believed to contribute to Parkinson's progression; UDCA has been used for certain liver conditions for over 30 years and was safe and well tolerated in the early-stage UP study in Parkinson's patients.
- Preliminary: UDCA's disease-modifying potential: identified by screening a drug library in patient tissue, with encouraging brain-energy-metabolism signals in a small proof-of-concept trial. Efficacy is unproven until the phase 3 platform reports.
- Absent: Any completed large-scale evidence that UDCA slows Parkinson's progression — the EJS ACT-PD arm is designed to produce that evidence and has no results yet.
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