Pitavastatin is a new synthetic 3-hydroxy-3-methyl glutaryl coenzyme A reductase (HMG-CoA reductase) inhibitor, which was developed, and has been available in Japan since July 2003. Metabolism of pitavastatin by the cytochrome P450 (CYP) system is minimal, principally through CYP 2C9, with little involvement of the CYP 3A4 isoenzyme, potentially reducing the risk of drug-drug interactions between pitavastatin and other drugs known to inhibit CYP enzymes. To date, human and animal studies have shown pitavastatin to be potentially as effective in lowering LDL-cholesterol levels as rosuvastatin. Pitavastatin under the trade name Livalo is indicated as an adjunctive therapy to diet to reduce elevated total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), apolipoprotein B (Apo B), triglycerides (TG), and to increase HDL-C in adult patients with primary hyperlipidemia or mixed dyslipidemia. Pitavastatin competitively inhibits HMG-CoA reductase, which is a rate-determining enzyme involved with biosynthesis of cholesterol, in a manner of competition with the substrate so that it inhibits cholesterol synthesis in the liver. As a result, the expression of LDL-receptors followed by the uptake of LDL from blood to liver is accelerated and then the plasma TC decreases. Further, the sustained inhibition of cholesterol synthesis in the liver decreases levels of very low density lipoproteins. Common statin-related side effects (headaches, stomach upset, abnormal liver function tests and muscle cramps) were similar to other statins.

Atorvastatin calcium (LIPITOR®) is a pyrrole and heptanoic acid derivative, a synthetic lipid-lowering agent. Atorvastatin is a selective, competitive inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase. This enzyme catalyzes the conversion of HMG-CoA to mevalonate, an early and rate-limiting step in cholesterol biosynthesis. Atorvastatin is used to reduce serum levels of LDL(low-density lipoprotein)-cholesterol; apolipoprotein B; and triglycerides and to increase serum levels of HDL(high-density lipoprotein)-cholesterol in the treatment of hyperlipidemias and prevention of cardiovascular disease in patients with multiple risk factors.

Pitavastatin lactone is the major metabolite of pitavastatin in humans. Pitavastatin is a potent competitive inhibitor of HMG-CoA reductase, which is indicated for hypercholesterolaemia (elevated cholesterol) and for the prevention of cardiovascular disease. Uridine 5’ -diphosphate (UDP) glucuronosyl transferase (UGT) is critically involved in the lactonization of pitavastatin in man and animals. The metabolic and transporter profiles of pitavastatin in man are complex, involving acid/lactone interconversion. Both forms of pitavastatin are observed in-vivo following oral administration. Lactone form and pitavastatin differ in substrate activity towards uptake and efflux transporters.

Tenivastatin (well known as simvastatin acid or simvastatin hydroxy acid) is a pharmacologically active metabolite, which is formed in the mammalian organism from lactone prodrug, simvastatin. Tenivastatin is a potent reversible inhibitor of HMGCR (HMG-CoA reductase), reduces cholesterol synthesis and increases low-density lipoprotein (LDL) receptors on cell membranes of liver and extrahepatic tissues. It is also a substrate of organic anion transporting polypeptide 1B1 (OATP1B1/Oatp2), an influx transporter expressed on the sinusoidal membrane of hepatocytes. Recent studies have shown that OATP1B1 plays a clinically important role in the hepatic elimination of several drugs including statins, via mediating the hepatic uptake. In addition, was discovered, that the tenivastatin was a substrate of another transporter protein, human organic anion transporting polypeptide 3A1 (OATP3A1), which is predominately expressed in the heart. Presence of OATP3A1 in cardiomyocytes suggested that transporter could modulate the exposure of cardiac tissue to simvastatin acid due to its enrichment in cardiomyocytes. Increases in the uptake of simvastatin acid by OATP3A1 when combined with OATP substrates suggest the potential for drug-drug interactions that could influence clinical outcomes.