CGP 37157 is a benzothiazepine that acts as a selective inhibitor of the mitochondrial sodium-calcium exchanger (IC50 = 0.36 μM in isolated mitochondria). It does not affect channels, exchangers, or ATPases on the cardiac sarcolemma or ATPases on sarcoplasmic reticulum. CGP 37157 is commonly used to study the role of mitochondrial-derived calcium in cytoplasmic calcium homeostasis. CGP 37157 inhibits sodium-dependent calcium efflux via the mitochondrial exchanger NCLX in a variety of cell types (IC50 = 5 μM).