Embodiments herein generally relate to methods, compositions and uses of CaMKII inhibitors. Other embodiments relate to methods, compositions and uses of agents that target CaMKII. Yet further embodiments relate to compositions, methods and uses of CaMKIIN-derived molecules and other CaMKII inhibitor molecules that inhibit autonomous CaMKII activity. In accordance with these embodiments, compositions that inhibit autonomous CaMKII activity may be used for treating conditions causing neuronal cell death, for treating cancer or for treating neurodegenerative disorders.