A large fraction of modern drug development is focused on specific biochemical pathways, often identified via the study of rare genetic disorders or genome-wide association studies. For example, patients with Familial hypercholesterolemia, a relatively rare genetic disorder, provided strong evidence for a causal role of cholesterol in ischaemic heart disease (a discovery for which Brown and Goldstein were awarded the Nobel prize). The enzyme inhibited by statins (HMG-CoA-reductase) is a key player in this pathway.