UDCA: an old liver drug joins the world's largest Parkinson's trial
The bile acid UDCA is thought to strengthen the power plants of nerve cells. It is now being tested in the large UK trial EJS ACT-PD.
Updated: November 2026
I am particularly interested in drugs that already exist and might be put to new use for Parkinson's. That is why I was very pleased about news from 5 November 2026: ursodeoxycholic acid, UDCA for short, is now being tested in a large trial.
What is it about?
UDCA is a bile acid that has been used for decades against certain liver and gallbladder diseases. It is well researched, inexpensive and considered well tolerated.
UDCA is interesting for Parkinson's because it apparently strengthens the mitochondria, the power plants of our cells. In Parkinson's, these power plants work less well in the dopamine-producing nerve cells, and this is considered one reason why the cells gradually die. UDCA was discovered in Sheffield: the team of Prof. Oliver Bandmann tested an entire library of known drugs on tissue from Parkinson's patients, and UDCA stood out positively.
What do we know so far? The UP study
- Phase 2, randomized, double-blind, placebo-controlled
- 30 people with Parkinson's, two thirds received UDCA, one third placebo
- High dose: 30 mg per kilogram of body weight per day, for 48 weeks
- Published in 2023 in the journal Movement Disorders (PubMed)
The results:
- UDCA was safe and well tolerated. Only mild, temporary stomach and bowel complaints were more common than with placebo.
- Special brain scans (magnetic resonance spectroscopy) showed signs of better energy supply in the midbrain, exactly where the dopamine cells are located.
- A sensor-based gait analysis pointed to a possibly better gait.
- The classic rating of movement (MDS-UPDRS Part 3), however, showed no difference from placebo.
The new trial: EJS ACT-PD
According to the University of Sheffield, the Edmond J Safra Accelerating Clinical Trials in Parkinson's Disease trial is the largest of its kind in the world. It is led by University College London and Newcastle University and is to include around 2,000 participants at 40 hospitals in the UK. What makes it special: it tests several drugs at the same time against a shared placebo group. So far these were the blood pressure drug telmisartan and the prostate drug terazosin. Now UDCA is joining as the third drug. New participants are randomly assigned to UDCA, telmisartan, terazosin or one of two placebo groups.
The aim is to find out whether one of these drugs really slows the progression of Parkinson's.
And what about TUDCA?
Many of you know TUDCA (tauroursodeoxycholic acid), which is sold freely in Germany as a dietary supplement. TUDCA is closely related to UDCA: it is UDCA with the amino acid taurine attached, and the body even makes some of it itself from ingested UDCA. Both are thought to strengthen the mitochondria in a similar way.
Even so, the two must not simply be treated as the same. The data on which the new trial is based come from UDCA at a high dose. For TUDCA in Parkinson's there are so far only positive results from cell cultures and animal studies, but no controlled trial in patients. In ALS, on the other hand, TUDCA was tested in a large European phase 3 trial with 336 participants over 18 months. The result was sobering: no difference from placebo, neither in the course of the disease nor in survival (NeurologyLive). This shows me how careful one has to be with hopes from animal models. Whether TUDCA helps in Parkinson's is simply not known.
My assessment
I think the approach is smart. Instead of spending decades developing new molecules, known and safe drugs are being tested specifically for Parkinson's. If one of them works, it could reach us patients very quickly.
But we have to stay honest: so far there is no proof that UDCA slows Parkinson's. The UP study was small and was mainly meant to test safety. The better values for energy supply in the brain are a hint, nothing more. There was no difference in movement. It will probably be several years before the large trial delivers results.
In Germany UDCA requires a prescription, and the dose used in the study is high. I therefore expressly advise against starting it on your own. Anyone considering it should discuss it with their neurologist. I will follow the trial closely and report here as soon as there is news.
Sources
- University of Sheffield: Drug discovery by Sheffield scientists joins world's largest trial of Parkinson's treatments
- Payne et al., Movement Disorders 2023: UP study of UDCA in Parkinson's
- NeurologyLive: TUDCA falls short in phase 3 ALS trial (April 2024)
Note: This article describes my personal view and is not medical advice. UDCA requires a prescription; please do not take it without medical supervision.