Deuterium in drug discovery: progress, opportunities and challenges

Substituting a hydrogen atom with its heavy isotope deuterium may improve the pharmacokinetic and/or toxicity profile of a drug compared with its non-deuterated counterpart. This article highlights milestones in the field of deuteration in drug discovery and development, and discusses recent examples of its application, which have shifted towards deuteration of novel drug candidates instead of developing deuterated analogues of marketed drugs. Substitution of a hydrogen atom with its heavy isotope deuterium entails the addition of one neutron to a molecule. Despite being a subtle change, this structural modification, known as deuteration, may improve the pharmacokinetic and/or toxicity profile of drugs, potentially translating into improvements in efficacy and safety compared with the non-deuterated counterparts. Initially, efforts to exploit this potential primarily led to the development of deuterated analogues of marketed drugs through a 'deuterium switch' approach, such as deutetrabenazine, which became the first deuterated drug to receive FDA approval in 2017. In the past few years, the focus has shifted to applying deuteration in novel drug discovery, and the FDA approved the pioneering de novo deuterated drug deucravacitinib in 2022. In this Review, we highlight key milestones in the field of deuteration in drug discovery and development, emphasizing recent and instructive medicinal chemistry programmes and discussing the opportunities and hurdles for drug developers, as well as the questions that remain to be addressed.