Defining clinical outcome pathways

•We define the concept of Clinical Outcome Pathways (COP).•COPs is a chain of key events: Initiating-Intermediate-Clinical Outcome.•COPs will deepen our understanding of the biological pathways of drug action.•COP concept could accelerate drug discovery and repurposing. Here, we propose a broad concept of ‘Clinical Outcome Pathways’ (COPs), which are defined as a series of key molecular and cellular events that underlie therapeutic effects of drug molecules. We formalize COPs as a chain of the following events: molecular initiating event (MIE) → intermediate event(s) → clinical outcome. We illustrate the concept with COP examples both for primary and alternative (i.e., drug repurposing) therapeutic applications. We also describe the elucidation of COPs for several drugs of interest using the publicly accessible Reasoning Over Biomedical Objects linked in Knowledge-Oriented Pathways (ROBOKOP) biomedical knowledge graph-mining tool. We propose that broader use of COP uncovered with the help of biomedical knowledge graph mining will likely accelerate drug discovery and repurposing efforts.