KN-93 hydrochloride is a cell-permeable, reversible, and competitive inhibitor of calmodulin-dependent kinase type II (CaMKII) with a K_i of 370 nM.

Following a 2-day treatment with KN-93, 95% of cells experienced G1 arrest, which was found to be reversible as cells began to progress into S and G2-M phases 1 day post-release of KN-93. Additionally, KN-93 effectively inhibits the growth of NIH 3T3 fibroblasts stimulated by basic fibroblast growth factor, platelet-derived growth factor-BB, and epidermal growth factor. Furthermore, KN-93 demonstrates the ability to inhibit H+, K+-ATPase activity, significantly dissipate proton gradients across gastric membrane vesicles, and decrease luminal space volume. At a concentration of 0.5 μM, KN-93 prevents the increase in left ventricular (LV) developed pressure observed during action potential prolongation and early afterdepolarizations, a process linked to the prevention of the rise in Ca2+-independent CaM kinase activity that occurs during early afterdepolarizations.