KN-62 is a potent and specific inhibitor of Ca2+/calmodulin-dependent protein kinase II (CaMKII) with Ki of 0.9 μM; also a non-competitive antagonist of the purinergic receptor P2RX7 (IC50 = 15 nM). It is selective for CaMKII relative to PKA, PKC and MLCK, but inhibits CaMKI and CaMKIV equally well, The Ki value of KN-62 for CaMK V is 0.8 μM.