K252A is a staurosporine analogue isolated from a Nocardiopsis strain as a potent inhibitor of protein kinase C. K252A exhibits potent antitumor activity but shows no antimicrobial activity in vitro, or in vivo toxicity in rodents. While K252A is a potent inhibitor of Ca2+/calmodulin kinase II, it is also active against other kinases, notably myosin light chain kinase, cAMP-dependent protein kinase (PKA), protein kinase C (PKC) and cGMP-dependent protein kinase (PKG).