Fergus McTaggart

Preclinical and clinical pharmacology of Rosuvastatin, a new 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor.

Rosuvastatin (formerly ZD4522) is a new 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor (statin) with distinct pharmacologic properties. Compared with most other statins, it is relatively hydrophilic, similar in this respect to pravastatin. Rosuvastatin has been shown to be a comparatively potent inhibitor of HMG-CoA reductase activity in a purified preparation of the catalytic domain of the human enzyme, as well as in rat and human hepatic microsomes. In rat hepatocytes, rosuvastatin was found to have significantly higher potency as an inhibitor of cholesterol synthesis than 5 other statins. Rosuvastatin was approximately 1,000-fold more potent in rat hepatocytes than in rat fibroblasts. Further studies in rat hepatocytes demonstrated that rosuvastatin is taken up into these cells by a high-affinity active uptake process. Rosuvastatin was also taken up selectively into the liver after intravenous administration in rats. Potent and prolonged HMG-CoA reductase inhibitory activity has been demonstrated after oral administration to rats and dogs. Pharmacokinetic studies in humans using oral doses of 5 to 80 mg showed that maximum plasma concentrations and areas under the concentration-time curve are approximately linear with dose. The terminal half-life is approximately 20 hours. Studies with human hepatic microsomes and human hepatocytes have suggested little or no metabolism via the cytochrome P-450 3A4 isoenzyme. On the basis of these observations, it is suggested that rosuvastatin has the potential to exert a profound effect on atherogenic lipoproteins.

Inhibitors of 3-Hydroxy-3-Methylglutaryl–CoA Reductase Reduce Receptor-Mediated Endocytosis in Opossum Kidney Cells

Renal proximal tubule cells are responsible for the reabsorption of proteins that are present in the tubular lumen. This occurs by receptor-mediated endocytosis, a process that has a requirement for some GTP-binding proteins. Statins are inhibitors of 3-hydroxy-3-methylglutaryl CoA (HMG-CoA) reductase used for the therapeutic reduction of cholesterol-containing plasma lipoproteins. However, they can also reduce intracellular levels of isoprenoid pyrophosphates that are derived from the product of the enzyme, mevalonate, and are required for the prenylation and normal function of GTP-binding proteins. The hypothesis that inhibition of HMG-CoA reductase in renal proximal tubule cells could reduce receptor mediated-endocytosis was therefore tested. Five different statins inhibited the uptake of FITC-labeled albumin by the proximal tubule-derived opossum kidney cell line in a dose-dependent manner and in the absence of cytotoxicity. The reduction in albumin uptake was related to the degree of inhibition of HMG-CoA reductase. Simvastatin (e.g., statin) inhibited receptor-mediated endocytosis of both FITC-albumin and FITC-beta(2)-microglobulin to similar extents but without altering the binding of albumin to the cell surface. The effect on albumin endocytosis was prevented by mevalonate and by the isoprenoid geranylgeranyl pyrophosphate but not by cholesterol. Finally, evidence that the inhibitory effect of statins on endocytosis of proteins may be caused by reduced prenylation and thereby decreased function of one or more GTP-binding proteins is provided. These data establish the possibility in principle that inhibition of HMG-CoA reductase by statins in proximal tubule cells may reduce tubular protein reabsorption.

Comparative pharmacology of rosuvastatin

The major therapeutic action of statin drugs is reduction in levels of circulating atherogenic lipoproteins as a result of inhibition of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase mainly in the liver. The magnitude of reduction of atherogenic lipoproteins differs among various statins. It is suggested that an ideal statin would maximize the pharmacodynamic activity in the liver and minimize the inhibitory activity outside the liver, particularly in some vulnerable tissues, such as skeletal muscle. An additional advantage would be a low risk of undesirable interactions with other drugs. Compared with other statins, rosuvastatin has been found to be a relatively potent inhibitor of HMG-CoA reductase and to have a high degree of selectivity for effect in liver cells compared with a range of non-hepatic cells, including cultured human skeletal muscle cells. In addition, rosuvastatin undergoes relatively little metabolism by the hepatic CYP system; it has a moderate degree of systemic bioavailability and a relatively long elimination half-life. On the basis of these criteria, rosuvastatin represents a step forward in efforts to optimize the pharmacologic properties of the statin class.

Effects of Statins on High-Density Lipoproteins: A Potential Contribution to Cardiovascular Benefit

PurposeThe objective was to systematically review clinical trial data on the effects of statins on high-density lipoproteins (HDL) and to examine the possibility that this provides cardiovascular benefits in addition to those derived from reductions in low-density lipoproteins (LDL).MethodsThe PubMed database was searched for publications describing clinical trials of atorvastatin, pravastatin, rosuvastatin, and simvastatin. On the basis of predefined criteria, 103 were selected for review.ResultsCompared with placebo, statins raise HDL, measured as HDL-cholesterol (HDL-C) and apolipoprotein A-I (apo A-I); these elevations are maintained in the long-term. In hypercholesterolemia, HDL-C is raised by approximately 4% to 10%. The percentage changes are greater in patients with low baseline levels, including those with the common combination of high triglycerides (TG) and low HDL-C. These effects do not appear to be dose-related although there is evidence that, with the exception of atorvastatin, the changes in HDL-C are proportional to reductions in apo B-containing lipoproteins. The most likely explanation is a reduced rate of cholesteryl ester transfer protein (CETP)-mediated flow of cholesterol from HDL. There is some evidence that the statin effects on HDL reduce progression of atherosclerosis and risk of cardiovascular disease independently of reductions in LDL.ConclusionStatins cause modest increases in HDL-C and apo A-I probably mediated by reductions in CETP activity. It is plausible that such changes independently contribute to the cardiovascular benefits of the statin class but more studies are needed to further explore this possibility.

Optimizing the pharmacology of statins: characteristics of rosuvastatin.

Rosuvastatin (Crestor, AstraZeneca) is a new synthetic statin that exhibits a number of highly desirable pharmacologic characteristics. The drug has a high affinity for the active site of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase and exhibits greater potency in inhibiting enzyme activity and cholesterol synthesis in vitro than other statins. The effects of rosuvastatin are selective for hepatic cells, and there is minimal uptake of the drug by nonhepatic tissues. The vast majority of biologic activity of the drug is associated with the parent compound, which does not appear to undergo extensive metabolism. Hepatic metabolism appears to be minimal, and there is little evidence of metabolic interaction with cytochrome P450 3A4. In an early-phase study, rosuvastatin produced large and dose-related decreases in low-density lipoprotein (LDL) cholesterol of up to 65% in hypercholesterolemic patients. Rosuvastatin should constitute an important addition to current lipid-lowering interventions.

Novel optimised quinuclidine squalene synthase inhibitors

Abstract Optimised quinuclidine squalene synthase (SQS) inhibitors are reported; 3-[2-(2-allyl-4-(2-ethoxy carbonylethyl)phenyl)ethynyl]quinuclidin-3-ol 1c, is a potent inhibitor of rat (KI = 6 nM) and human (KI = 43 nM) microsomal SQS; the oral ED50 of 1c, for the inhibition of rat cholesterol biosynthesis was 1.3±0.45 mg/kg and for the R-enantiomer 1m, 0.8±0.2 mg/kg, with the corresponding R-carboxylic acid 6a, being 0.9±0.25 mg/kg.