As a structurally novel, potent, and pan-KCa3.1/KCa2 channel active inhibitor 13b constitutes a new tool compound to further study the physiological and pathophysiological roles of these channels and might also have therapeutic utility in disease states, like chronic inflammation and autoimmune disease, atherosclerosis, fibrosis, cancer, and hypotension to which KCa3.1/KCa2 channel up-regulation or activation contribute. Here, KCNN4 is linked to autoimmune disease.