Terfenadine-d3 (()-Terfenadine-d3) is the deuterium labeled Terfenadine. Terfenadine (()-Terfenadine) is a potent open-channel blocker of hERG with an IC50 of 204 nM[1]. Terfenadine, an H1 histamine receptor antagonist, acts as a potent apoptosis inducer in melanoma cells through modulation of Ca2+ homeostasis. Terfenadine induces ROS-dependent apoptosis, simultaneously activates Caspase-4, -2, -9[2].