Abstract
Selenium has frequently been used as a less electronegative substitute for sulfur in potential pharmaceuticals. While substitution with selenium can increase the potency of thiol compounds, the reactivity of selenium with sulfhydryl groups often leads to increased toxicity. The discovery of selenium at the active site of glutathione peroxidase (GSH-Px) led to a search for selenium compounds which could affect GSH-Px. The benzisoselenazolone, ebselen, catalyses hydroperoxide breakdown per se, exhibits anti-inflammatory activity and is being developed clinically for the treatment of cerebral ischaemia. Its toxicity is low because of metabolic retention of selenium within the molecule. Other compounds have been synthesised to take advantage of the catalytic activity of selenium substitution, but have either fallen victim to management concerns about toxicity or are still at an early stage of development.