AZA-PD

Our studies of the immune system in Parkinson’s disease indicate that immune activation and inflammation are associated with faster disease progression – and suggest that immunosuppression might be a useful therapeutic strategy for PD. To explore this, we conducted a clinical trial repurposing an immunosuppressant drug called azathioprine, which is already used to treat a number of autoimmune and inflammatory conditions. 66 participants were randomly allocated to receive treatment with either azathioprine or placebo for 12 months (in addition to their usual PD treatment) and were followed up for a further 6 months afterwards. Although there was no effect on the primary outcome measure (assessing walking and balance), we found that azathioprine had a beneficial effect on motor symptoms, with the greatest benefits being seen in women. Although azathioprine acts on the peripheral immune system and does not cross the blood brain barrier, our results showed that treatment did impact on the central nervous system - leading to a reduction of immune cells in the cerebrospinal fluid, and a reduction in the spread of brain inflammation. Importantly, the trial also showed that there were no significant safety concerns with azathioprine use in people with Parkinson's. Overall, the AZA-PD trial has provided 'proof of concept' for the approach of targeting the peripheral immune system in PD - paving the way for future immune therapy trials. 

The results are available in full at Greenland et al. Azathioprine for the treatment of early Parkinson's disease (AZA-PD): a randomised, double-blind, placebo-controlled, proof-of-concept, phase 2 trial. The Lancet Neurology. 2026;25(1):39-49.

Julia Greenland (pictured with Caroline Williams-Gray) presented the results of the AZA-PD trial at the international ADPD conference in April 2025 and received a junior faculty award 

The AZA-PD trial was funded by the Centre for Parkinson-Plus and Cure Parkinson’s, and supported by the NIHR Cambridge Biomedical Research Centre.