KN-93 hydrochloride (CAS 1956426-56-4) is a selective inhibitor of Ca2 /calmodulin-dependent protein kinase II (CaMK II) binding competitively at the calmodulin site with a reported Ki of 0 37 M and an IC50 of 370 nM In isolated gastric parietal cells KN-93 suppresses acid secretion stimulated by carbachol and histamine with IC50 values of 0 15 M and 0 3 M respectively and inhibits mucin-stimulated aminopyrine uptake (IC50 0 6 M) Additionally KN-93 shows inhibitory activity against H /K -ATPase and directly blocks voltage-gated potassium (Kv) channels by promoting C-type inactivation KN-93 is widely used to probe CaMK II signaling and its downstream physiological effects in cellular and electrophysiological studies