Jag carried out postdoctoral research with Professor Steve Ley, FRS, working on the total synthesis of rapamycin. In 1997 he joined SmithklineBeecham as a medicinal chemist. In 2009 he joined UCB in Belgium as Director of Medicinal Chemistry working on CNS projects. In 2015 he relocated to UCB Slough to work on immunology and inflammation NCE projects. He has a broad range of interests from hit identification to candidate selection, working at the interface of computational drug design, cheminformatics, and medicinal chemistry. He is associated with delivering clinical candidates in a number of therapeutic areas including CNS and cardiovascular disease and is a fellow of the Royal Society of Chemistry.