Why is it important?
Similarly to other areas of medicine, recognition that cancer, for instance, was not a single disease led to massive progress in discovering the different, unique pathways underlying different subtypes. This now allows treating each individual with a unique regime, and targeting their disease precisely. A similar shift in the dominant view on Parkinson’s is now taking place, with leading clinicians and researchers around the world recognising that a ‘one size fits all’ approach it not serving us in the quest for cures. This is because each individual represents a unique profile of clinical characteristics (signs and symptoms), genetic and biochemical barkers. Rather than ignoring differences and trying to find a shared, common pattern across the millions of patient profiles that are routinely enrolled in trials and treated in clinic, the more constructive approach is to make meaningful sense of these differences. Using biomarkers, that is, biological substances, including genes, which allow us to identify and track disease, we are already discovering the different pathways that cause Parkinson’s in different people. This explains why one person can play numerous rounds of golf more than 20 years into their disease, while another may have significantly reduced mobility just 5 years after diagnosis.
Systematically addressing biomarker relationships to Parkinson’s, and focusing on different genes, inflammation profiles, glucose tolerance levels etc, will enable us to pinpoint a range of very different biochemical mechanisms, each leading to different forms of Parkinson’s. Espay et al describe this as a necessary “identity change” similar to the one that took place in oncology. Subtyping Parkinson’s on the basis of superficial signs and symptoms has not served the Parkinson’s community well. What we anticipate should be far more successful is subtyping according to different biomarkers that reveal different underlying disease processes.
The Parkinson’s community is recognising that progress on biomarker discovery is essential. This requires the collection and storage of biological samples (eg blood, CSF) for each patient enrolled in a trial, so that large numbers of these can be pooled and analysed now, or in the future. In addition, the development of a separate set of criteria for Parkinson’s which will now include biomarkers in addition to clinical signs will be informative, especially in clinical trials. Perhaps the most important next step in our hunt for cures may first be a step back before the next leap forward: with precision medicine, we need to redefine the different subtypes of Parkinson’s and target their diverse underlying processes with the right, tailored treatments.
Related work and trials