hERG (the human Ether-à-go-go-Related Gene) is a gene (KCNH2) that codes for a protein known as Kv11.1, the alpha subunit of a potassium ion channel. This ion channel (sometimes simply denoted as 'hERG') is best known for its contribution to the electrical activity of the heart: the hERG channel mediates the repolarizing IKr current in the cardiac action potential, which helps coordinate the heart's beating.
When this channel's ability to conduct electrical current across the cell membrane is inhibited or compromised, either by application of drugs or by rare mutations in some families, it can result in a potentially fatal disorder called long QT syndrome. Conversely, genetic mutations that increase the current through these channels can lead to the related inherited heart rhythm disorder short QT syndrome. A number of clinically successful drugs in the market have had the tendency to inhibit hERG, lengthening the QT and potentially leading to a fatal irregularity of the heartbeat (a ventricular tachyarrhythmia called torsades de pointes). This has made hERG inhibition an important antitarget...