A key component of mechanistic evaluation and target validation is defining target engagement/modulation biomarkers. As a first step towards biomarker identification, we utilise our linked kinase–substrate residue phosphorylation information (in collaboration with Phosphosite (15); Supplementary Figure S2B). The user can select specific phosphorylation sites on the target itself or on downstream substrates that, to the best of our knowledge, are unique to the target's enzymatic action. Though the biomarker decision is dependent on the specific experimental question being addressed, the user is alerted when additional targets are known to modify the same site and can factor in this information to their experimental design.
