Opportunities and challenges related to participant stratification and cohort enrichment in ALS clinical trials

Amyotrophic lateral sclerosis (ALS) is marked by substantial clinical heterogeneity. This heterogeneity has impacted clinical trials by obscuring treatment effects and causing inefficiency. In this review, we summarize potential approaches for addressing heterogeneity in ALS via patient stratification and cohort enrichment methods and highlight potential challenges and limitations. These categories include stratification based on genetics, clinical characteristics (e.g. pattern of weakness, ALS Functional Rating Scale rates of progression), wet biomarkers (e.g. neurofilament light chain), neuroimaging, and novel methods employing statistical modeling or machine learning. These stratification methods have yet to be fully leveraged in clinical trial design. But these strategies must be employed thoughtfully and judiciously due to potential issues stratification can introduce. Future clinical trials should explore how participant stratification and cohort enrichment strategies may improve our ability to identify treatment effects, which may ultimately aid in the quest to establish more personalized medicine for persons with ALS.