Baricitinib (99.97% purity) and tofacitinib (99.96% purity) compounds were purchased from MedChem Express LLC (New Jersey, www.medchemexpress.com). In vitro characterization was performed on a fee-for-service basis at Eurofins (www.eurofins.com), if the assay was commercially available. Baricitinib and tofacitinib were tested at a single concentration (30 µM) or multiple concentrations (30 µM highest concentration) with technical replicates, using biochemical assays (radioligand or enzymatic assays) or cell-based assays (see online supplementary material 2 for further details).