Molecular pathology of familial hypercholesterolemia, related dyslipidemias and therapies beyond the statins

The development of the statin class of cholesterol-lowering drugs is one of the most significant success stories of modern pharmacotherapy. World-wide there are an estimated 150 million people on statins, with the emerging economies of India and China predicted to contribute significantly to that number. Notwithstanding their success, a significant number of people cannot tolerate statins because of serious side effects; of equal concern, a substantial proportion of high risk patients fail to reach cholesterol-lowering targets. For these subjects there is an urgent need for new cholesterol-lowering agents to be used alone or in combination with statins. The success of statins has been largely underpinned by knowledge of cholesterol homeostasis at a molecular level, knowledge that was first gleaned in the 1980s from Brown and Goldstein's pioneering studies of familial hypercholesterolemia (FH, OMIM 143890). Follow-up work that has identified a number of intracellular and circulating factors, all capable of disrupting LDL clearance, has revealed that the low-density lipoprotein receptor- (LDLR) mediated clearance pathway is substantially more complex than previously thought. These factors were discovered in studies of individuals with very rare inherited conditions that lead to either hypo- or hypercholesterolemia. These investigations, besides providing clearer insight into the molecular mechanisms regulating plasma LDL concentrations, have also revealed a number of novel therapeutic targets independent from statins. Consequently, a number of novel therapeutic approaches that are based on small interfering bio-molecules, including antisense oligonucleotides, are now in clinical development. These are aimed at impairing the assembly, synthesis and secretion of apolipoprotein B-containing lipoproteins and/or accelerating their hepatic catabolism. The aim of this article is to focus on these recent advances in the understanding of the molecular basis of cholesterol metabolism that should herald novel cholesterol-lowering agents beyond the statins.