Alberto Espay, MD, FAAN, University of Cincinnati, Cincinnati, OH, talks on the urgent need for improved Parkinson’s disease subtyping. Over the years, many molecules aiming to modify disease progression have been through clinical trials and failed. However, patients recruited to these trials were all done so without any assessment of whether they had any underlying biology that would make them suitable for the intervention. Thus, many candidate molecules may have been overlooked by not assessing them in a population where the specific pathway they are active in is indicated in their disease. Prof. Espay emphasizes that bioassays to confirm whether the investigative agent has the potential to benefit an individual are a critical missing component. Prof. Espay highlights work being done to combat this need, including the development of a biomarker program undertaking phenotype-agnostic molecular subtyping of neurodegenerative disorders. The study is using a reverse biology-to-phenotype direction of biomarker development aimed at linking biologically suitable subjects to already available drugs with repurposing potential. This interview took place during the 2021 International Congress of Parkinson’s Disease and Movement Disorders.