Disappointing results from trials of vaccines for Parkinson’s, but hope for the future

Results published in the New England Journal of Medicine provide an update on 2 clinical trials looking to slow the progression of Parkinson’s. One paper shares the results from a phase 2 study of prasinezumab in 316 people recently diagnosed with Parkinson’s (the PASADENA study). The other on results from a phase 2 trial of cinpanemab in 357 people (the SPARK study) over a period of 2 years. Neither of these studies were funded by Parkinson's UK but some people may have taken part in these studies.

While these published results have not been promising, there is hope that antibody based therapies may be beneficial over a longer term. And there are further opportunities for people to take part in the research.

• Read the full results of the PASADENA study on the New England Journal of Medicine website.
• Read the full results of the SPARK study on the New England Journal of Medicine website.

What did the research set out to do? 

Both studies used vaccination to target and remove a protein called alpha-synuclein. This protein forms clumps inside the cells affected by Parkinson’s and is believed to contribute to the loss of brain cells. 

What do we mean by a vaccine for Parkinson’s? 

Scientists have taken inspiration from the body’s immune defence, which uses specialised proteins called antibodies to mark and fight off unwanted invaders, like bacteria and viruses. These antibodies can also be used to get rid of unwanted proteins. The researchers designed their own antibodies in the lab to recognise and stick to alpha-synuclein to mark the protein for removal. They delivered these antibodies during the study via an injection. 

Biotech companies Prothena and Roche called their potential treatment prasinezumab and Biogen called theirs cinpanemab. They are very similar but stick to alpha-synuclein in slightly different ways. 

What are the results? 

Both studies compared a placebo (a dummy treatment) to the active treatment and measured whether motor and non-motor symptoms of Parkinson’s improved over at least a period of 2 years. Neither showed an effect on improving symptoms or slowing the progression of the condition. 

What’s next? 

Please note this trial has finished recruiting. The trial into cinpanemab has stopped. However, the trial to investigate prasinezumab is in its next stage and is currently recruiting 575 people recently diagnosed with Parkinson’s to see if the treatment is beneficial over 5 years. 

Dr Katherine Fletcher, Research Communications Manager at Parkinson’s UK, said:  

"It is always disappointing to hear when trials don’t meet their aims. However, it will be interesting to follow the next stage of the prasinezumab trial to see if a longer period of treatment is needed. 

"These results show that we still don’t know enough about the different forms of alpha-synuclein, which is needed to help uncover specific ways of targeting this protein in Parkinson’s. But it is vital that research continues to explore all avenues for something that has the potential to slow or stop the condition."