SP600125 is a potent, selective and reversible inhibitor of the three JNK enzymes (c-Jun N-terminal kinases), with IC50 = 40 nM for JNK1 and JNK2, and 90 nM for JNK3. Inhibition is competitive with respect to ATP, and over 300-fold more selective for JNK as compared to ERK1 and p38-2 MAP kinases. SP600125 was shown to cause a dose-dependent inhibition of the phosphorylation of c-Jun, and thereby the expression of inflammatory genes COX-2, IFN-γ, IL-2, TNF-α, and block the activation and differentiation of primary human CD4 cell cultures. SP 600125 has also been shown to prevent apoptosis in an array of cell types, and inhibit autophagy in HeLa cells.