Landmark 155 · Trial in people
AZA-PD azathioprine
Did not meet its main goal in 66 people over 12 months. Immune markers moved, but symptoms did not clearly improve.
In short
The first trial of an immune-suppressing drug in early Parkinson's (66 people, 12 months) did not meet its primary measure (off-state gait and axial score at 12 months); exploratory analyses hinted at immune-marker effects.
- What it is
- Trial in people
- Outcome
- Did not work
- When
- 2020–2026
- Size
- 66 people · Phase 2
- Approach
- Look beyond the brain
- Research lane
- Inflammation & immunity
- Last checked
- 19 Oct 2026
The research record
This is the project's file for this landmark, as written and checked. Sources are listed at the end; anything not yet confirmed is marked "Not yet verified".
Who
Caroline Williams-Gray, Julia Greenland and colleagues, University of Cambridge (single site). Funded by the Cambridge Centre for Parkinson-Plus, Cure Parkinson's and the NIHR Cambridge Biomedical Research Centre.
What happened
- Azathioprine is an old drug that suppresses T and B cells. It does not cross the blood-brain barrier, so the test was of the peripheral immune system.
- Phase 2. Randomised, double-blind. 66 people aged 50-80, within 3 years of diagnosis, enrolled from May 2021 to July 2022 (32 azathioprine, 34 placebo). Oral azathioprine 2 mg/kg a day or placebo for 12 months.
- Result (Lancet Neurology, 2026). Primary measure: change in the off-state MDS-UPDRS gait-axial score at 12 months. It rose 0.54 points on azathioprine and 0.13 on placebo (effect size 0.438, 95% CI −0.694 to 1.57, p=0.78): not met. Serious adverse events: 8 (24%) on azathioprine, 4 (12%) on placebo. Exploratory analyses suggested effects on peripheral and central immune markers and on motor symptoms, possibly larger in women than men; these are hypotheses only.
- The team calls it proof of concept that the peripheral immune system can be targeted.
Why it moved us toward a cure
It put the autoimmune idea from landmark 38 to a direct test. The immune markers may have moved but the primary measure did not, so on this evidence immune suppression alone does not slow the disease.
Outcome
Dead end for azathioprine as a slowing treatment; the immune branch stays open.
Sources
- Greenland et al., Lancet Neurol 2026, DOI 10.1016/S1474-4422(25)00386-2, PMID 41389828 (abstract via Europe PMC); ISRCTN 14616801
- Cure Parkinson's results page, Feb 2026
- Cambridge Network news · Williams-Gray lab page
- Not yet verified: the full paper (abstract only); the exploratory biomarker and sex-difference results; the dapansutrile (DAPA-PD) follow-on trial mentioned by the team (removed from the text); the volume and pages (lab page gives 25(1):39-49). A correction: an earlier version said the study began in 2020 and called the primary measure a general motor outcome.
How it connects
Built on
- tests T cells recognise synuclein · 2017
Led to
- builds on DAPA-PD (dapansutrile) · 2026