A potent, selective, and cell-permeable inhibitor of p38 MAP kinases; inhibits p38α (SAPK2A, MAPK14) and p38β (SAPK2B, MAPK11) with IC50 values of 50 and 100 nM, respectively; has negligible effects on a range of other kinases when used at a concentration of 10 μM; including other MAP kinases such as ERK and JNK