SR-318 is a potent and selective type-II inhibitor th at targets p38α/β in an inactive DFG-out conformation with good kinome selectivity (p38α/β IC50 = 5/39 nM by radiometric kinase assay). SR-318 selectively inhibits p38α/β by cell-based NanoBRET assay (IC50 = 3.7 nM/p38α, 10 nM/p38β, 0.91 μM/ZAK, ≥3 μM/DDR1, DDR2, KIT, MYLK4, RSK4) and effectively blocks LPS-induced TNF-α release in human whole blood (IC50 = 283 nM). SR-321 is an inactive structural analog and the recommended negative control compound.