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Optimizing the pharmacology of statins: characteristics of rosuvastatin
Atherosclerosis Supplements 2 (2002) 33 – 37 www.elsevier.com/locate/atherosclerosis
Optimizing the pharmacology of statins: characteristics of rosuvastatin M. John Chapman a,*, Fergus McTaggart b a
Pa6illon Benjamin Delassert, INSERM Unite 321, Hopital de la Pitie, 83 Boule6ard de l’hopital, 75651 Paris, Cedex 13, France b CV and GI Disco6ery, AstraZeneca, Alderley Park, Macclesfield, Cheshire, UK
Abstract 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. © 2002 Elsevier Science Ireland Ltd. All rights reserved. Keywords: 3-Hydroxy-3-methylglutaryl coenzyme A reductase; Pharmacological properties; Tissue selectivity; Lipid profile; Pleiotropic effects
1. Introduction
2. Chemical properties of rosuvastatin
Statins are recognized as highly effective and well-tolerated agents in reducing low-density lipoprotein (LDL) cholesterol and exerting beneficial effects on other lipid parameters. Attempts to optimize pharmacologic attributes and lipid-modifying effects of this drug class are ongoing. ‘Ideal’ pharmacologic characteristics might be argued to include potent reversible inhibition of the target 3-hydroxy-3-methylglutaryl coenzyme A (HMG – CoA) reductase enzyme in vitro and in vivo; high selectivity for uptake and action in the liver; inhibitory action that is optimal for reduction of atherogenic plasma lipoproteins; biologic activity primarily derived from the parent compound; lack of tissue accumulation; and minimal potential for drug – drug interaction. The new statin rosuvastatin (Crestor®; AstraZeneca, Alderley Park, Macclesfield, Cheshire, UK; licensed from Shionogi & Co. Ltd., Osaka, Japan) will be evaluated in light of these criteria.
Rosuvastatin is a synthetic compound consisting of a single enantiomer (3R5S) formulated and administered as the calcium salt of the active hydroxy acid. The molecule consists of a dihydroxy heptenoic acid portion, the characteristic statin pharmacophore, which binds to the active site of the target enzyme, 3-hydroxy-3-methylglutaryl coenzyme A (HMG –CoA) reductase. The remainder of the molecule is structurally distinct from the corresponding portions of other statins. This latter non –HMG –CoA reductase –binding domain of the rosuvastatin molecule includes a polar methane sulfonamide group that confers relatively low lipophilicity [1]. Rosuvastatin (log D at pH 7.4, − 0.33) therefore more closely resembles pravastatin (log D, − 0.84) in terms of lipophilicity when compared with other statins (log D \ 1 and B 2 for atorvastatin, fluvastatin, simvastatin, and cerivastatin) [2]. Given its relative hydrophilicity, rosuvastatin may exhibit limited access to nonhepatic cells as a result of low passive diffusion and avid hepatic cell uptake via selective organic anion transport. In addition, the relative water solubility of the compound may be associated with reduced need for cytochrome P450 (CYP) enzyme metabolism.
* Corresponding author. Tel.: +33-1-4217-7878; fax: + 33-1-45828198. E-mail address: [email protected] (M.J. Chapman).
0021-9150/02/$ - see front matter © 2002 Elsevier Science Ireland Ltd. All rights reserved. PII: S 1 5 6 7 - 5 6 8 8 ( 0 1 ) 0 0 0 1 6 - 2
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M.J. Chapman, F. McTaggart / Atherosclerosis 2 (2002) 33–37
X-ray crystallography studies of binding between the catalytic domain of human HMG– CoA reductase and a number of statins indicate that statins inhibit this enzyme by attaching to its active site and sterically inhibiting substrate binding [3]. Compared with other statins (mevastatin, simvastatin, fluvastatin, cerivastatin, and atorvastatin), rosuvastatin has the greatest number of bonding interactions with HMG– CoA reductase, including a unique polar interaction between the Arg568 side chain of the enzyme and the electronegative sulfone group of rosuvastatin, as well as a variety of other interactions that occur in other enzyme –statin complexes. Another binding characteristic seen only with rosuvastatin and atorvastatin is a hydrogen bond between Ser565 and a sulfone oxygen atom (rosuvastatin) or a carbonyl oxygen atom (atorvastatin). Overall, the interactions between rosuvastatin and the active site of the enzyme distinguish this statin as the most potent HMG– CoA reductase inhibitor developed to date.
3. Activity and selectivity Rosuvastatin exhibits reversible inhibition of HMG –CoA reductase that is competitive with the HMG –CoA substrate and noncompetitive with the cosubstrate NADPH (nicotinamide– adenine dinucleotide phosphate). Studies using the purified catalytic domain of human HMG – CoA reductase indicate that rosuvastatin has high affinity for the active site (Ki $ 0.1 nM). In purified human catalytic domain preparations, rosuvastatin exhibited a mean 50% inhibitory concentration (IC50) of 5.4 nM, compared with mean IC50 values of 8.2 nM for atorvastatin, 10.0 nM for cerivastatin, 11.2 nM for simvastatin, 27.6 nM for fluvastatin and 44.1 nM for pravastatin [4,5]. In primary rat hepatocytes, the mean rosuvastatin IC50 value for inhibition of cholesterol synthesis was 0.16 nM, compared with 1.16 nM for atorvastatin, 2.74 nM for simvastatin, 3.54 for cerivastatin, 3.78 for fluvastatin and 6.93 for pravastatin [4]. Further evidence of potent inhibition of cholesterol synthesis was observed in a study of rat hepatic microsomes [2]. In this study, rosuvastatin had a prolonged effect on hepatic cholesterol synthesis, exhibiting 62% inhibition at 7 hours after oral administration, compared with −7% for atorvastatin, 13% for simvastatin and 31% for cerivastatin. With respect to hepatic selectivity, comparison of rosuvastatin’s inhibitory effects in primary rat hepatocytes versus cultured rat fibroblasts showed that inhibition in fibroblasts was approximately 1000-fold lower. In addition, the log ratio for inhibitory activity in hepatocytes:fibroblasts was 3.3 for both rosuvastatin and pravastatin, compared with 2.2 for atorva-
statin, 0.54 for simvastatin, − 0.04 for fluvastatin and − 0.14 for cerivastatin [1]. Studies with 14C-labeled rosuvastatin in rat hepatocytes showed hepatocyte uptake by both nonspecific diffusion and active transport, with a specific uptake Km of 9.2 mM (Fig. 1, top) [6]. The rate of active uptake clearance was significantly greater than that of pravastatin, the other statin with relatively low lipophilicity. Intravenous administration of 14C-labeled rosuvastatin at a dose of 5 mg/kg to rats revealed that uptake clearance rates were 0.9 ml/min/g into the liver, 0.2 ml/min/g into the kidney, and 5 0.02 ml/min/g into other tissues (Fig. 1, bottom). Pravastatin also showed liver uptake selectivity, whereas simvastatin showed high rates of uptake not only into the liver but also into other tissues such as the adrenals and spleen.
4. Metabolism Single- and multiple-dose pharmacokinetic studies in healthy subjects indicate that maximum plasma concentration achieved and the area under the concentration–time curve for rosuvastatin are approximately linear over a dose range of 5–80 mg and that the elimination half-life of the drug is approximately 20 h [4,7]. Approximately 85–95% of circulating active HMG–CoA reductase inhibitory activity is due to unchanged rosuvastatin (i.e. the parent compound). In studies of the excretion of the drug using 14C-labeled compound at a dose of 20 mg, 90% of the dose was recovered in feces and 10% in the urine; 92% of the radioactivity in feces and approximately 50% in urine were associated with the parent compound, indicating the absence of extensive rosuvastatin metabolism [8]. A number of available statins are metabolized by CYP 3A4 enzymes and thus have potential for drug– drug interactions. In vitro investigation of the effects of rosuvastatin 50 mM on CYP 1A2, 2C9, 2C19, 2D6, 2E1, and 3A4 activity in human hepatic microsomes showed no significant inhibitory effect on any of the enzymes. At worst, 2C9 enzyme activity was reduced by 10% [9]. Since the hepatic concentration of rosuvastatin after a 20-mg dose is predicted to be B 1 mM, these findings indicate a very low likelihood of clinically significant CYP enzyme inhibition in vivo. Consistent with the in vivo findings indicating absence of significant metabolism are in vitro studies of rosuvastatin at concentrations of 1–4 mM that show absence of metabolism by human hepatic microsomes and heterologously expressed CYP enzymes, as well as very slow metabolism by cultured human hepatocytes (5–50% over 3 days). In the latter case, a single M-desmethyl product was formed, with inhibi-
M.J. Chapman, F. McTaggart / Atherosclerosis 2 (2002) 33–37
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Fig. 1. Top: uptake of 14C-labeled rosuvastatin into rat hepatocytes. Inset, right, shows nonspecific diffusion and specific uptake at rosuvastatin concentrations up to around 150 mM. Bottom: rates of uptake clearance (CLuptake) into various tissues after intravenous administration of 14 C-labeled rosuvastatin 5 mg/kg in rats. Data are from Nezasa [6].
tion of metabolism by sulphaphenazole and omeprazole, which indicates that 2C9 and 2C19 were the enzymes primarily active in this metabolism. Overall, these findings suggest that rosuvastatin is unlikely to be associated with clinically significant metabolic interactions.
5. Effects on lipid profile In a phase II dose-ranging program, rosuvastatin was administered to hypercholesterolemic patients at doses of 1 –80 mg for 6 weeks [10]. Treatment was associated with large dose-dependent reductions in LDL cholesterol of up to 65%, reductions in triglycerides of up to 35%, and increases in high-density lipoprotein cholesterol (HDL cholesterol) of up to 14% (Table 1). As reviewed in more detail elsewhere in this supplement, the efficacy of rosuvastatin in reducing LDL cholesterol and improving other lipid variables has subsequently been demonstrated in a number of phase III trials, which have shown superiority of rosuvastatin over atorvastatin, pravastatin, and simvastatin in reducing LDL cholesterol in primary hypercholesterolemia [11,12] and over atorvastatin in familial hypercholesterolemia [13].
6. Pleiotropic effects A number of recent studies have suggested that in addition to modifying blood lipids, statins may exert a beneficial effect in protecting the vascular endothelium from inflammatory processes, and that this effect may be associated with statin-induced upregulation of endothelial nitric oxide synthase (eNOS) [14,15]. Under pathophysiologic conditions, nitric oxide exerts an antiinflammatory effect by preventing leukocyte adherence to the endothelium. A recent study examined the effects of intraperitoneally administered rosuvastatin on Table 1 Effect of rosuvastatin 5–80 mg for 6 weeks on key lipid variables in dose-ranging program in hypercholesterolemic patients Percent change
LDL cholesterol Triglycerides HDL cholesterol
5 mg
10 mg
20 mg
40 mg
80 mg
−43 −35 +14
−51 −10 +14
−57 −23 +10
−63 −28 +10
−65 −23 +13
From Olsson et al. [10].
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M.J. Chapman, F. McTaggart / Atherosclerosis 2 (2002) 33–37
thrombin-induced leukocyte-endothelium interactions in rat mesenteric microvasculature using intravital microscopy [16]. It was found that pretreatment with rosuvastatin significantly and dose dependently attenuated leukocyte rolling, adherence, and transmigration. In addition, rosuvastatin treatment was associated with a significant reduction in expression of the adhesion molecule P-selectin on immunohistochemical analysis, as well as with enhanced release of nitric oxide measured directly in aortic segments. The investigators also demonstrated that inhibition of leukocyte– endothelium interactions was reversed by pretreatment with mevalonic acid, and that rosuvastatin pretreatment did not reduce leukocyte–endothelium interactions in eNOSdeficient mice (eNOS − / − ). Taken together, these findings indicate that rosuvastatin exerts significant anti-inflammatory effects by inhibiting endothelial cell adhesion molecule expression, that the protective effect requires endothelial release of nitric oxide, and that the anti-inflammatory effects of statins may be associated with decreased mevalonic acid activity within endothelial cells.
7. Conclusion As a potential inhibitor of HMG–CoA reductase, rosuvastatin exhibits optimized pharmacologic characteristics. It is a highly efficacious, liver-selective inhibitor of HMG –CoA reductase and a potent inhibitor of cholesterol synthesis in primary hepatocytes, and also exhibits minimal uptake by nonhepatic tissues. The vast majority of rosuvastatin’s biologic activity is associated with the parent compound. Hepatic metabolism of the drug is minimal, and clinically significant drug– drug interactions due to interactions with CYP enzymes appear unlikely. Rosuvastatin has been shown to produce large, dose-dependent reductions in LDL cholesterol and beneficial effects on other lipid variables in hypercholesterolemic patients. This new statin should constitute a valuable addition to options in lipid-lowering therapy in dyslipidemic subjects at elevated cardiovascular risk.
Appendix A. Question and answer session Vincent Mooser, Switzerland: Regarding the very high tissue specificity of rosuvastatin, do you think that this may represent a drawback regarding the pleiotropic effects? John Chapman: The answer would be ‘not necessarily,’ for several reasons. The first one would be that the high level of tissue specificity may prove advantageous in terms of a potentially lower frequency of adverse effects in peripheral tissues. The second point that
should be made is that work from Dr Lefer’s laboratory in Philadelphia shows that in vivo in the rat, very low circulating concentrations of rosuvastatin induce increases in nitric oxide availability and diminish leukocyte adhesion to the endothelial surface. At the present time, the precise molecular mechanisms have not been defined, but we cannot exclude either a direct effect within those cells or a systemic effect of rosuvastatin. Certainly, though, the hepatic specificity does not seem in any way to preclude the potential for pleiotropic effects for this particular statin. James Shepherd: Another question from the audience concerns the variability of the effect of rosuvastatin on triglycerides in the phase II data — whether there is any relationship between the phenotype of the individual and the kind of response that you’re going to see. So, John, why do you think there’s so much variability in the way triglycerides respond, and do the people with high triglycerides get a better response? John Chapman: There is a suggestion with statins that the response in terms of triglyceride lowering may well be phenotype dependent. One of the reasons why that question is mechanistically complex is because the plasma triglyceride level represents a global measurement of a series of triglyceride-rich particles containing apo B of both intestinal and hepatic origin — VLDL-1, VLDL-2, and their remnants. Recent work suggests that certain of those particles may be preferentially targeted by statin treatment, particularly the hepatic production of VLDL-1, as shown by Professor Packard in in vivo studies of type IIb subjects. So the response, in terms of triglyceride reduction, may well depend on the profile of triglyceride-rich particles at baseline, and on their origin. We also cannot exclude effects on such enzymes as lipoprotein lipase and hepatic lipase, and there is evidence for indirect modulation of both of those enzymes by statins. So the suggestion would be that there are a number of mechanisms involved in the statin-mediated reduction of triglyceride, and that this is, at least in part, dependent on phenotype and, particularly, on the relative proportions and origins of the circulating triglyceride-rich particles. James Shepherd [audience question]: Is there anything that you can tell us about the influence of rosuvastatin on fibrinogen? John Chapman: Unfortunately, no. Certainly, the effects of members of the statin family on fibrinogen appear to vary. There is a suggestion from Professor Stael’s laboratory that the fibrinogen gene is, in part, regulated by PPAR (peroxisome proliferator-activated receptor)-a, and there is now the suggestion that there may be an indirect action of statins on PPAR-a in the liver. So one would suppose that there would tend to be a reduction in fibrinogen by statins. But that has not always been the case.
M.J. Chapman, F. McTaggart / Atherosclerosis 2 (2002) 33–37
James Shepherd: Another question. What do you think is the value of the increases in HDL cholesterol that we see with rosuvastatin? Do you think that is going to give it a particular edge? John Chapman: I think this is an exceedingly important question. The only clinical data that can be brought to bear in response to that question are from the 4S trial, in which a relatively small — I think 7% — increase in HDL cholesterol in those high-risk hypercholesterolemic individuals was seen to contribute significantly, at the P =.048 level, to the reduction in cardiovascular morbidity and mortality. At the moment, it would appear that in individuals with an HDL cholesterol in the region of 30– 40 mg/dl, it’s particularly critical to raise that, and it is particularly beneficial even when the increase in HDL cholesterol is relatively small. We still have to learn exactly what the nature of those particles is and how they exert their cardioprotective action. Hypothetically, the reverse cholesterol pathway would certainly be one of the priority candidates to explain that action. But I still don’t think we have the evidence to respond fully to that question.
References [1] Buckett L, Ballard P, Davidson R, Dunkley C, Martin L, Stafford J, McTaggart F. Selectivity of ZD4522 for inhibition of cholesterol synthesis in hepatic versus non-hepatic cells. Atherosclerosis 2000;151:41. Abstract MoP29:W6. [2] Smith G, Davidson R, Bloor S, Burns K, Calnan C, McAulay P, Torr N, Ward W, McTaggart F. Pharmacological properties of ZD4522 — a new HMG–CoA reductase inhibitor. Atherosclerosis 2000;151:39. Abstract MoP20:W6. [3] Istvan ES, Deisenhofer J. Structural mechanism for statin inhibition of HMG– CoA reductase. Science 2001;292:1160 – 4. [4] McTaggart F, Buckett L, Davidson R, Holdgate G, McCormick A, Schneck D, Smith G, Warwick M. Preclinical and clinical pharmacology of rosuvastatin, a new 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor. Am J Cardiol 2001;87 (Suppl):28B – 32B. [5] Data on file, AstraZeneca, 2000.
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[6] Nezasa K, Higaki K, Hasegawa H, Inazawa K, Takeuchi M, Yukawa T, McTaggart F, Nakano M. Uptake of HMG–CoA reductase inhibitor ZD4522 into hepatocytes and distribution into liver and other tissues of the rat. Atherosclerosis 2000;151:39. Abstract MoP21:W6. [7] Warwick MJ, Dane AL, Raza A, Schneck DW. Single- and multiple-dose pharmacokinetics and safety of the new HMG – CoA reductase inhibitor ZD4522. Atherosclerosis 2000;151:39. Abstract MoP19:W6. [8] Martin PD, Dane AL, Schneck DW, Warwick MJ. Disposition of new HMG– CoA reductase inhibitor ZD4522 following dosing in healthy subjects. J Clin Pharmacol 2000;40:1056. Abstract 48. [9] McCormick AD, McKillop D, Bulters CJ, Miles GS, Baba T, Touchi A, Yamaguchi Y. ZD4522: an HMG – CoA reductase inhibitor free of metabolically mediated drug interactions: metabolic studies in human in vitro systems. J Clin Pharmacol 2000;40:1055. Abstract 46. [10] Olsson AG, Pears J, McKellar J, Mizan J, Raza A. Effect of rosuvastatin on low-density lipoprotein cholesterol in patients with hypercholesterolemia. Am J Cardiol 2001;88(5):504 –8. [11] Paoletti R, Fahmy M, Mahla G, et al. Rosuvastatin demonstrates greater reduction of low-density lipoprotein cholesterol compared with pravastatin and simvastatin in hypercholesterolaemic patients: a randomised, double-blind study. J Cardiovasc Risk 2001;8:383 – 90. [12] Davidson M, Ma P, Stein E, Gotto AM, Raza A, Chitra R, Hutchinson H. Comparison of effects on low-density lipoprotein cholesterol and high-density lipoprotein cholesterol with rosuvastatin vs. atorvastatin in patients with type IIa or IIb hypercholesterolemia. Am J Cardiol 2002;89:268 – 75. [13] Stein E, Strutt KL, Miller E, Southworth H. Rosuvastatin (20, 40 and 80 mg) reduces LDL-C, raises HDL-C and achieves treatment goals more effectively than atorvastatin (20, 40 and 80 mg) in patients with heterozygous familial hypercholesterolemia (abstract). European Atherosclerosis Society 72nd Annual Meeting, 20 – 23 May, 2001, Glasgow, Scotland. Atherosclerosis 2001;Suppl 2:90 – 1. Abstract P176. [14] Lefer AM, Campbell B, Shin YK, Scalia R, Hayward R, Lefer DJ. Simvastatin preserves the ischemic-reperfused myocardium in normocholesterolemic rat hearts. Circulation 1999;100:178 – 84. [15] Pruefer D, Scalia R, Lefer AM. Simvastatin inhibits leukocyteendothelial cell interactions and protects against inflammatory processes in normocholesterolemic rats. Arterioscler Thromb Vasc Biol 1999;19:2894 – 900. [16] Stalker TJ, Lefer AM, Scalia R. A new HMG – CoA reductase inhibitor, rosuvastatin, exerts anti-inflammatory effects on the microvascular endothelium: the role of mevalonic acid. Br J Pharmacol 2001;133:406 – 12.
Optimizing the pharmacology of statins: characteristics of rosuvastatin M. John Chapman a,*, Fergus McTaggart b a
Pa6illon Benjamin Delassert, INSERM Unite 321, Hopital de la Pitie, 83 Boule6ard de l’hopital, 75651 Paris, Cedex 13, France b CV and GI Disco6ery, AstraZeneca, Alderley Park, Macclesfield, Cheshire, UK
Abstract 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. © 2002 Elsevier Science Ireland Ltd. All rights reserved. Keywords: 3-Hydroxy-3-methylglutaryl coenzyme A reductase; Pharmacological properties; Tissue selectivity; Lipid profile; Pleiotropic effects
1. Introduction
2. Chemical properties of rosuvastatin
Statins are recognized as highly effective and well-tolerated agents in reducing low-density lipoprotein (LDL) cholesterol and exerting beneficial effects on other lipid parameters. Attempts to optimize pharmacologic attributes and lipid-modifying effects of this drug class are ongoing. ‘Ideal’ pharmacologic characteristics might be argued to include potent reversible inhibition of the target 3-hydroxy-3-methylglutaryl coenzyme A (HMG – CoA) reductase enzyme in vitro and in vivo; high selectivity for uptake and action in the liver; inhibitory action that is optimal for reduction of atherogenic plasma lipoproteins; biologic activity primarily derived from the parent compound; lack of tissue accumulation; and minimal potential for drug – drug interaction. The new statin rosuvastatin (Crestor®; AstraZeneca, Alderley Park, Macclesfield, Cheshire, UK; licensed from Shionogi & Co. Ltd., Osaka, Japan) will be evaluated in light of these criteria.
Rosuvastatin is a synthetic compound consisting of a single enantiomer (3R5S) formulated and administered as the calcium salt of the active hydroxy acid. The molecule consists of a dihydroxy heptenoic acid portion, the characteristic statin pharmacophore, which binds to the active site of the target enzyme, 3-hydroxy-3-methylglutaryl coenzyme A (HMG –CoA) reductase. The remainder of the molecule is structurally distinct from the corresponding portions of other statins. This latter non –HMG –CoA reductase –binding domain of the rosuvastatin molecule includes a polar methane sulfonamide group that confers relatively low lipophilicity [1]. Rosuvastatin (log D at pH 7.4, − 0.33) therefore more closely resembles pravastatin (log D, − 0.84) in terms of lipophilicity when compared with other statins (log D \ 1 and B 2 for atorvastatin, fluvastatin, simvastatin, and cerivastatin) [2]. Given its relative hydrophilicity, rosuvastatin may exhibit limited access to nonhepatic cells as a result of low passive diffusion and avid hepatic cell uptake via selective organic anion transport. In addition, the relative water solubility of the compound may be associated with reduced need for cytochrome P450 (CYP) enzyme metabolism.
* Corresponding author. Tel.: +33-1-4217-7878; fax: + 33-1-45828198. E-mail address: [email protected] (M.J. Chapman).
0021-9150/02/$ - see front matter © 2002 Elsevier Science Ireland Ltd. All rights reserved. PII: S 1 5 6 7 - 5 6 8 8 ( 0 1 ) 0 0 0 1 6 - 2
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M.J. Chapman, F. McTaggart / Atherosclerosis 2 (2002) 33–37
X-ray crystallography studies of binding between the catalytic domain of human HMG– CoA reductase and a number of statins indicate that statins inhibit this enzyme by attaching to its active site and sterically inhibiting substrate binding [3]. Compared with other statins (mevastatin, simvastatin, fluvastatin, cerivastatin, and atorvastatin), rosuvastatin has the greatest number of bonding interactions with HMG– CoA reductase, including a unique polar interaction between the Arg568 side chain of the enzyme and the electronegative sulfone group of rosuvastatin, as well as a variety of other interactions that occur in other enzyme –statin complexes. Another binding characteristic seen only with rosuvastatin and atorvastatin is a hydrogen bond between Ser565 and a sulfone oxygen atom (rosuvastatin) or a carbonyl oxygen atom (atorvastatin). Overall, the interactions between rosuvastatin and the active site of the enzyme distinguish this statin as the most potent HMG– CoA reductase inhibitor developed to date.
3. Activity and selectivity Rosuvastatin exhibits reversible inhibition of HMG –CoA reductase that is competitive with the HMG –CoA substrate and noncompetitive with the cosubstrate NADPH (nicotinamide– adenine dinucleotide phosphate). Studies using the purified catalytic domain of human HMG – CoA reductase indicate that rosuvastatin has high affinity for the active site (Ki $ 0.1 nM). In purified human catalytic domain preparations, rosuvastatin exhibited a mean 50% inhibitory concentration (IC50) of 5.4 nM, compared with mean IC50 values of 8.2 nM for atorvastatin, 10.0 nM for cerivastatin, 11.2 nM for simvastatin, 27.6 nM for fluvastatin and 44.1 nM for pravastatin [4,5]. In primary rat hepatocytes, the mean rosuvastatin IC50 value for inhibition of cholesterol synthesis was 0.16 nM, compared with 1.16 nM for atorvastatin, 2.74 nM for simvastatin, 3.54 for cerivastatin, 3.78 for fluvastatin and 6.93 for pravastatin [4]. Further evidence of potent inhibition of cholesterol synthesis was observed in a study of rat hepatic microsomes [2]. In this study, rosuvastatin had a prolonged effect on hepatic cholesterol synthesis, exhibiting 62% inhibition at 7 hours after oral administration, compared with −7% for atorvastatin, 13% for simvastatin and 31% for cerivastatin. With respect to hepatic selectivity, comparison of rosuvastatin’s inhibitory effects in primary rat hepatocytes versus cultured rat fibroblasts showed that inhibition in fibroblasts was approximately 1000-fold lower. In addition, the log ratio for inhibitory activity in hepatocytes:fibroblasts was 3.3 for both rosuvastatin and pravastatin, compared with 2.2 for atorva-
statin, 0.54 for simvastatin, − 0.04 for fluvastatin and − 0.14 for cerivastatin [1]. Studies with 14C-labeled rosuvastatin in rat hepatocytes showed hepatocyte uptake by both nonspecific diffusion and active transport, with a specific uptake Km of 9.2 mM (Fig. 1, top) [6]. The rate of active uptake clearance was significantly greater than that of pravastatin, the other statin with relatively low lipophilicity. Intravenous administration of 14C-labeled rosuvastatin at a dose of 5 mg/kg to rats revealed that uptake clearance rates were 0.9 ml/min/g into the liver, 0.2 ml/min/g into the kidney, and 5 0.02 ml/min/g into other tissues (Fig. 1, bottom). Pravastatin also showed liver uptake selectivity, whereas simvastatin showed high rates of uptake not only into the liver but also into other tissues such as the adrenals and spleen.
4. Metabolism Single- and multiple-dose pharmacokinetic studies in healthy subjects indicate that maximum plasma concentration achieved and the area under the concentration–time curve for rosuvastatin are approximately linear over a dose range of 5–80 mg and that the elimination half-life of the drug is approximately 20 h [4,7]. Approximately 85–95% of circulating active HMG–CoA reductase inhibitory activity is due to unchanged rosuvastatin (i.e. the parent compound). In studies of the excretion of the drug using 14C-labeled compound at a dose of 20 mg, 90% of the dose was recovered in feces and 10% in the urine; 92% of the radioactivity in feces and approximately 50% in urine were associated with the parent compound, indicating the absence of extensive rosuvastatin metabolism [8]. A number of available statins are metabolized by CYP 3A4 enzymes and thus have potential for drug– drug interactions. In vitro investigation of the effects of rosuvastatin 50 mM on CYP 1A2, 2C9, 2C19, 2D6, 2E1, and 3A4 activity in human hepatic microsomes showed no significant inhibitory effect on any of the enzymes. At worst, 2C9 enzyme activity was reduced by 10% [9]. Since the hepatic concentration of rosuvastatin after a 20-mg dose is predicted to be B 1 mM, these findings indicate a very low likelihood of clinically significant CYP enzyme inhibition in vivo. Consistent with the in vivo findings indicating absence of significant metabolism are in vitro studies of rosuvastatin at concentrations of 1–4 mM that show absence of metabolism by human hepatic microsomes and heterologously expressed CYP enzymes, as well as very slow metabolism by cultured human hepatocytes (5–50% over 3 days). In the latter case, a single M-desmethyl product was formed, with inhibi-
M.J. Chapman, F. McTaggart / Atherosclerosis 2 (2002) 33–37
35
Fig. 1. Top: uptake of 14C-labeled rosuvastatin into rat hepatocytes. Inset, right, shows nonspecific diffusion and specific uptake at rosuvastatin concentrations up to around 150 mM. Bottom: rates of uptake clearance (CLuptake) into various tissues after intravenous administration of 14 C-labeled rosuvastatin 5 mg/kg in rats. Data are from Nezasa [6].
tion of metabolism by sulphaphenazole and omeprazole, which indicates that 2C9 and 2C19 were the enzymes primarily active in this metabolism. Overall, these findings suggest that rosuvastatin is unlikely to be associated with clinically significant metabolic interactions.
5. Effects on lipid profile In a phase II dose-ranging program, rosuvastatin was administered to hypercholesterolemic patients at doses of 1 –80 mg for 6 weeks [10]. Treatment was associated with large dose-dependent reductions in LDL cholesterol of up to 65%, reductions in triglycerides of up to 35%, and increases in high-density lipoprotein cholesterol (HDL cholesterol) of up to 14% (Table 1). As reviewed in more detail elsewhere in this supplement, the efficacy of rosuvastatin in reducing LDL cholesterol and improving other lipid variables has subsequently been demonstrated in a number of phase III trials, which have shown superiority of rosuvastatin over atorvastatin, pravastatin, and simvastatin in reducing LDL cholesterol in primary hypercholesterolemia [11,12] and over atorvastatin in familial hypercholesterolemia [13].
6. Pleiotropic effects A number of recent studies have suggested that in addition to modifying blood lipids, statins may exert a beneficial effect in protecting the vascular endothelium from inflammatory processes, and that this effect may be associated with statin-induced upregulation of endothelial nitric oxide synthase (eNOS) [14,15]. Under pathophysiologic conditions, nitric oxide exerts an antiinflammatory effect by preventing leukocyte adherence to the endothelium. A recent study examined the effects of intraperitoneally administered rosuvastatin on Table 1 Effect of rosuvastatin 5–80 mg for 6 weeks on key lipid variables in dose-ranging program in hypercholesterolemic patients Percent change
LDL cholesterol Triglycerides HDL cholesterol
5 mg
10 mg
20 mg
40 mg
80 mg
−43 −35 +14
−51 −10 +14
−57 −23 +10
−63 −28 +10
−65 −23 +13
From Olsson et al. [10].
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thrombin-induced leukocyte-endothelium interactions in rat mesenteric microvasculature using intravital microscopy [16]. It was found that pretreatment with rosuvastatin significantly and dose dependently attenuated leukocyte rolling, adherence, and transmigration. In addition, rosuvastatin treatment was associated with a significant reduction in expression of the adhesion molecule P-selectin on immunohistochemical analysis, as well as with enhanced release of nitric oxide measured directly in aortic segments. The investigators also demonstrated that inhibition of leukocyte– endothelium interactions was reversed by pretreatment with mevalonic acid, and that rosuvastatin pretreatment did not reduce leukocyte–endothelium interactions in eNOSdeficient mice (eNOS − / − ). Taken together, these findings indicate that rosuvastatin exerts significant anti-inflammatory effects by inhibiting endothelial cell adhesion molecule expression, that the protective effect requires endothelial release of nitric oxide, and that the anti-inflammatory effects of statins may be associated with decreased mevalonic acid activity within endothelial cells.
7. Conclusion As a potential inhibitor of HMG–CoA reductase, rosuvastatin exhibits optimized pharmacologic characteristics. It is a highly efficacious, liver-selective inhibitor of HMG –CoA reductase and a potent inhibitor of cholesterol synthesis in primary hepatocytes, and also exhibits minimal uptake by nonhepatic tissues. The vast majority of rosuvastatin’s biologic activity is associated with the parent compound. Hepatic metabolism of the drug is minimal, and clinically significant drug– drug interactions due to interactions with CYP enzymes appear unlikely. Rosuvastatin has been shown to produce large, dose-dependent reductions in LDL cholesterol and beneficial effects on other lipid variables in hypercholesterolemic patients. This new statin should constitute a valuable addition to options in lipid-lowering therapy in dyslipidemic subjects at elevated cardiovascular risk.
Appendix A. Question and answer session Vincent Mooser, Switzerland: Regarding the very high tissue specificity of rosuvastatin, do you think that this may represent a drawback regarding the pleiotropic effects? John Chapman: The answer would be ‘not necessarily,’ for several reasons. The first one would be that the high level of tissue specificity may prove advantageous in terms of a potentially lower frequency of adverse effects in peripheral tissues. The second point that
should be made is that work from Dr Lefer’s laboratory in Philadelphia shows that in vivo in the rat, very low circulating concentrations of rosuvastatin induce increases in nitric oxide availability and diminish leukocyte adhesion to the endothelial surface. At the present time, the precise molecular mechanisms have not been defined, but we cannot exclude either a direct effect within those cells or a systemic effect of rosuvastatin. Certainly, though, the hepatic specificity does not seem in any way to preclude the potential for pleiotropic effects for this particular statin. James Shepherd: Another question from the audience concerns the variability of the effect of rosuvastatin on triglycerides in the phase II data — whether there is any relationship between the phenotype of the individual and the kind of response that you’re going to see. So, John, why do you think there’s so much variability in the way triglycerides respond, and do the people with high triglycerides get a better response? John Chapman: There is a suggestion with statins that the response in terms of triglyceride lowering may well be phenotype dependent. One of the reasons why that question is mechanistically complex is because the plasma triglyceride level represents a global measurement of a series of triglyceride-rich particles containing apo B of both intestinal and hepatic origin — VLDL-1, VLDL-2, and their remnants. Recent work suggests that certain of those particles may be preferentially targeted by statin treatment, particularly the hepatic production of VLDL-1, as shown by Professor Packard in in vivo studies of type IIb subjects. So the response, in terms of triglyceride reduction, may well depend on the profile of triglyceride-rich particles at baseline, and on their origin. We also cannot exclude effects on such enzymes as lipoprotein lipase and hepatic lipase, and there is evidence for indirect modulation of both of those enzymes by statins. So the suggestion would be that there are a number of mechanisms involved in the statin-mediated reduction of triglyceride, and that this is, at least in part, dependent on phenotype and, particularly, on the relative proportions and origins of the circulating triglyceride-rich particles. James Shepherd [audience question]: Is there anything that you can tell us about the influence of rosuvastatin on fibrinogen? John Chapman: Unfortunately, no. Certainly, the effects of members of the statin family on fibrinogen appear to vary. There is a suggestion from Professor Stael’s laboratory that the fibrinogen gene is, in part, regulated by PPAR (peroxisome proliferator-activated receptor)-a, and there is now the suggestion that there may be an indirect action of statins on PPAR-a in the liver. So one would suppose that there would tend to be a reduction in fibrinogen by statins. But that has not always been the case.
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James Shepherd: Another question. What do you think is the value of the increases in HDL cholesterol that we see with rosuvastatin? Do you think that is going to give it a particular edge? John Chapman: I think this is an exceedingly important question. The only clinical data that can be brought to bear in response to that question are from the 4S trial, in which a relatively small — I think 7% — increase in HDL cholesterol in those high-risk hypercholesterolemic individuals was seen to contribute significantly, at the P =.048 level, to the reduction in cardiovascular morbidity and mortality. At the moment, it would appear that in individuals with an HDL cholesterol in the region of 30– 40 mg/dl, it’s particularly critical to raise that, and it is particularly beneficial even when the increase in HDL cholesterol is relatively small. We still have to learn exactly what the nature of those particles is and how they exert their cardioprotective action. Hypothetically, the reverse cholesterol pathway would certainly be one of the priority candidates to explain that action. But I still don’t think we have the evidence to respond fully to that question.
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