Groundbreaking Cambridge research indicates immunosuppression may help treat Parkinson’s
Dr Caroline Williams-Gray, honorary consultant neurologist
07 April 2025
A pioneering trial, led from Cambridge Biomedical Research Centre, has shown that immunosuppressing medicines could provide the key to treatment of Parkinson’s disease, according to results presented this weekend at the world’s most prestigious neurodegeneration conference AD/PD.
The AZA/PD trial which was carried out at the NIHR Cambridge Clinical Research Facility is the first to show that broadly suppressing the immune system could have a beneficial impact in Parkinson’s disease.
Participants on the treatment reported an overall improvement in movement-related symptoms. This meant they found it easier to perform tasks such as moving around, writing, washing and dressing.
These improvements were greater in female participants compared to males.
Additionally, patients with faster-progressing Parkinson’s disease showed signs of improved memory and thinking skills. Importantly, the trial did not reveal significant safety concerns around using immunosuppression treatments in Parkinson’s disease. This will enable larger research studies of immune therapies for PD in the future.
Parkinson’s disease is the fastest growing neurological condition in the world, affecting over 10 million people and around 153,000 people in the UK. Although treatments exist to manage some symptoms, there are no cures and treatments do not slow disease progression.
The AZA-PD trial, included 66 people with early-stage Parkinson’s disease. It investigated the effects of the drug Azathioprine, which suppresses the immune system. Azathioprine is already widely used to treat conditions such as rheumatoid arthritis and inflammatory bowel disease.
Existing research has shown that the immune system is over-active in people with Parkinson’s disease. This trial indicates that targeting immune activation might be a useful strategy for the treatment of Parkinson’s and provides impetus for further research to confirm these results in larger groups of patients.
Participants on the trial were treated with Azathioprine or a placebo for 12 months and were then followed up for another 6 months. Assessments looked at various movement and non-movement related symptoms of Parkinson’s disease as well as assessing safety of treatment.
One of the reasons Parkinson’s disease has proven so challenging to treat is because the brain is surrounded by a structure called the blood-brain barrier that serves to protect against infections. Many drugs also cannot cross the barrier.
During the trial, the effect of the drug on the immune system was measured in both the blood and brains of participants. It showed that, although Azathioprine cannot cross the blood-brain barrier, it acts indirectly to slow progression of inflammation in the brain, and this could explain its effects in Parkinson’s disease.
