Chemical & Engineering News gives us a lesson in the joys of covalent bonds. Apparently, they're the marrying type, forming irreversible, 'til-death-do-us-part bonds between small-molecule drugs and protein targets. The fear is that a covalent bond would be "so desperate for a mate" that it hitches up to the wrong target, causing toxic side effects. As a result, drug companies have been happy to produce drugs that just can't commit. Now, groups of scientists within academia and in pharmaceutical companies are working on drugs that are looking for a long-term relationship with a single target and are working on covalent drug candidates. The strategy could mean drugs with low toxicity and high potency and selectivity. Full report here