Skepinone-L is a potent, ATP-competitive inhibitor of p38 MAPK isoform p38α (IC50 = 5 nM) and p38β (97% inhibition at 1 μM). It has little effect on a range of other kinases, including p38γ and p38δ. Skepinone-L dose-dependently blocks the phosphorylation of heat shock protein 27 (HSP27), a p38 MAPK substrate, in response to stimulation with anisomycin (Cat. No. 1549) in HeLa cells (IC50 = 25 nM) or TNF-α in THP-1 cells. MW: 425.4. Purity ≥98% by HPLC