PCSK9 and diabetes mellitus: In this review, we discuss the following topics: the biology of PCSK9; studies confirming the causal relationship between PCSK9 and cardiovascular disease (CVD); the various classes of PCSK9 inhibitors at different stages of investigation; the efficacy (in people with and without diabetes where data are available) and safety of PCSK9 inhibitors and their potential position in clinical practice.