Therapeutics promoting the endogenous production of IL-10 have the potential to restore homeostasis in inflammatory disorders such as inflammatory bowel disease (IBD). Here we describe the identification of a series of IL-10 upregulators based on a pyrimidyl-piperidine scaffold through a high throughput phenotypic CD4+ T-cell multiplex assay. In vitro optimization of the initial hit yielded a lead with good potency and an in vitro clearance profile, compound 3-7, which additionally demonstrated efficacy in a murine endotoxin challenge PK-PD mechanistic model. Target deconvolution efforts identified compound 3-7 as a highly selective CDK8/19 inhibitor, and crystallographic studies unveiled its binding mode to the CDK8/Cyclin-C complex, characterized by an unusual water-mediated hydrogen bond to the kinase hinge region.