Abstract Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a hepatic enzyme that regulates the low-density lipoprotein cholesterol (LDL-c) receptor and thus circulating LDL-c levels. With overwhelming evidence now supporting the reduction in LDL-c to lower the risk of cardiovascular disease, PCSK9 inhibitors represent an important therapeutic target, particularly in high-risk populations. Here, we summarise and update the science of PCSK9, including its discovery and the development of various inhibitors, including the now approved monoclonal antibodies. In addition, we summarise the clinical applications of PCSK9 inhibitors in a range of patient populations, as well as the major randomised controlled trials investigating their use in coronary prevention.