Characterization of simvastatin acid uptake by organic anion transporting polypeptide 3A1 (OATP3A1) and influence of drug-drug interaction

Human organic anion transporting polypeptide 3A1 (OATP3A1) is predominately expressed in the heart. The ability of OATP3A1 to transport statins into cardiomyocytes is unknown, although other OATPs are known to mediate the uptake of statin drugs in liver. The pleiotropic effects and uptake of simvastatin acid were analyzed in primary human cardiomyocytes and HEK293 cells transfected with the OATP3A1 gene. Treatment with simvastatin acid reduced indoxyl sulfate-mediated reactive oxygen species and modulated OATP3A1 expression in cardiomyocytes and HEK293 cells transfected with the OATP3A1 gene. We observed a pH-dependent effect on OATP3A1 uptake, with more efficient simvastatin acid uptake at pH5.5 in HEK293 cells transfected with the OATP3A1 gene. The Michaelis-Menten constant (K_m) for simvastatin acid uptake by OATP3A1 was 0.017±0.002μM and the V_max was 0.995±0.027fmol/min/10⁵ cells. Uptake of simvastatin acid was significantly increased by known (benzylpenicillin and estrone-3-sulfate) and potential (indoxyl sulfate and cyclosporine) substrates of OATP3A1. In conclusion, the presence of OATP3A1 in cardiomyocytes suggests that this transporter may modulate the exposure of cardiac tissue to simvastatin acid due to its enrichment in cardiomyocytes. Increases in uptake of simvastatin acid by OATP3A1 when combined with OATP substrates suggest the potential for drug-drug interactions that could influence clinical outcomes.

Fluvastatin use and risk of acute pancreatitis: a population-based case-control study in Taiwan

OBJECTIVES

This study aimed to examine the association between fluvastatin use and acute pancreatitis in Taiwan.

METHODS

Using the database from the Taiwan National Health Insurance (NHI) Program, we designed a case-control study which consisted of 3501 individuals aged 20-84 with new at-the-time diagnoses acute pancreatitis as the case group and 8373 randomly selected individuals without acute pancreatitis as the control group during the period of 1998-2011. Both groups were matched for sex, age, and index year of being diagnosed with acute pancreatitis. "Current use" of fluvastatin was defined as individuals whose last remaining tablet of fluvastatin was noted ≤ 7 days before the date of their being diagnosed with acute pancreatitis. "Late use" of fluvastatin was defined as individuals whose last remaining tablet of fluvastatin was noted within 8-30 days before the date of their being diagnosed with acute pancreatitis. "No use" of fluvastatin was defined as individuals who had never had a fluvastatin prescription. The odds ratio (OR) and 95% confidence interval (CI) for acute pancreatitis associated with fluvastatin use was examined using a multivariable unconditional logistic regression analysis.

RESULTS

After adjustment for potential confounders, the multivariable analysis showed that the adjusted ORs of acute pancreatitis were 1.17 for individuals with "current use" of fluvastatin (95% CI 0.69, 1.97) and 1.82 for individuals with "late use" of fluvastatin (95% CI 0.41, 8.19), but there was no statistical significance when compared with individuals with "no use" of fluvastatin.

CONCLUSIONS

In this this study, no association was detected between fluvastatin use and acute pancreatitis.

13-Series resolvins mediate the leukocyte-platelet actions of atorvastatin and pravastatin in inflammatory arthritis

Rheumatoid arthritis is an inflammatory condition characterized by overzealous inflammation that leads to joint damage and is associated with an increased incidence of cardiovascular disease. Statins are frontline therapeutics for patients with cardiovascular disease and exert beneficial actions in rheumatoid arthritis. The mechanism that mediates the beneficial actions of statins in rheumatoid arthritis remains of interest. In the present study, we found that the administration of 2 clinically relevant statins—atorvastatin (0.2 mg/kg) or pravastatin (0.2 mg/kg)—to mice during inflammatory arthritis up-regulated systemic and tissue amounts of a novel family of proresolving mediators, termed 13-series resolvins (RvTs), and significantly reduced joint disease. Of note, administration of simvastatin (0.2 mg/kg) did not significantly up-regulate RvTs or reduce joint inflammation. We also found that atorvastatin and pravastatin each reduced systemic leukocyte activation, including platelet-monocyte aggregates (∼25–60%). These statins decreased neutrophil trafficking to the joint as well as joint monocyte and macrophage numbers. Atorvastatin and pravastatin produced significant reductions (∼30–50%) in expression of CD11b and major histocompatibility complex class II on both monocytes and monocyte-derived macrophages in joints. Administration of an inhibitor to cyclooxygenase-2, the initiating enzyme in the RvT pathway, reversed the protective actions of these statins on both joint and systemic inflammation. Together, these findings provide evidence for the role of RvTs in mediating the protective actions of atorvastatin and pravastatin in reducing local and vascular inflammation, and suggest that RvTs may be useful in measuring the anti-inflammatory actions of statins.—Walker, M. E., Souza, P. R., Colas, R. A., Dalli, J. 13-Series resolvins mediate the leukocyte-platelet actions of atorvastatin and pravastatin in inflammatory arthritis.

Statins Prevent Dextrose-Induced Endoplasmic Reticulum Stress and Oxidative Stress in Endothelial and HepG2 Cells

Statins have favorable effects on endothelial function partly because of their capacity to reduce oxidative stress. However, antioxidant vitamins, unlike statins, are not as cardioprotective, and this paradox has been explained by failure of vitamin antioxidants to ameliorate endoplasmic reticulum (ER) stress. To determine whether statins prevent dextrose-induced ER stress in addition to their antioxidative effects, human umbilical vein endothelial cells and HepG2 hepatocytes were treated with 27.5 mM dextrose in the presence of simvastatin (lipophilic statin that is a prodrug) and pravastatin (water-soluble active drug), and oxidative stress, ER stress, and cell death were measured. Superoxide generation was measured using 2-methyl-6-(4-methoxyphenyl)-3,7-dihydroimidazo[1,2-A]pyrazin-3-one hydrochloride. ER stress was measured using the placental alkaline phosphatase assay and Western blot of glucose-regulated protein 75, c-jun-N-terminal kinase, phospho-JNK, eukaryotic initiating factor 2α and phospho-eIF2α, and X-box binding protein 1 mRNA splicing. Cell viability was measured by propidium iodide staining. Superoxide anion production, ER stress, and cell death induced by 27.5 mM dextrose were inhibited by therapeutic concentrations of simvastatin and pravastatin. The salutary effects of statins on endothelial cells in reducing both ER stress and oxidative stress observed with pravastatin and the prodrug simvastatin suggest that the effects may be independent of cholesterol-lowering activity.

Synthesis and antifungal activity of novel indole-replaced streptochlorin analogues

Based on examples of the successful applications in drug discovery of bioisosterism, a series of streptochlorin analogues in which indole has been replaced by other heterocycles has been designed and synthesized, as a continuation of our studies aimed at the discovery of novel streptochlorin analogues with improved antifungal activity. Biological testing showed that most of the indole-replaced streptochlorin analogues were inactive, though compound 6f had a broad spectrum of antifungal activity with significant activity against Alternaria solani. The SAR study demonstrated that indole ring is an essential moiety for the antifungal activity of streptochlorin analogues, promoting the idea of indole ring as a framework that might be exploited in the future.

Functioning of drug-metabolizing microsomal cytochrome P450s: In silico probing of proteins suggests that the distal heme 'active site' pocket plays a relatively 'passive role' in some enzyme-substrate interactions

PURPOSE

The currently held mechanistic understanding of microsomal cytochrome P450s (CYPs) seeks that diverse drug molecules bind within the deep-seated distal heme pocket and subsequently react at the heme centre. To explain a bevy of experimental observations and meta-analyses, we indulge a hypothesis that involves a "diffusible radical mediated" mechanism. This new hypothesis posits that many substrates could also bind at alternate loci on/within the enzyme and be reacted without the pertinent moiety accessing a bonding proximity to the purported catalytic Fe-O enzyme intermediate.

METHODS

Through blind and heme-distal pocket centered dockings of various substrates and non-substrates (drug molecules of diverse sizes, classes, topographies etc.) of microsomal CYPs, we explored the possibility of access of substrates via the distal channels, its binding energies, docking orientations, distance of reactive moieties (or molecule per se) to/from the heme centre, etc. We investigated specific cases like- (a) large drug molecules as substrates, (b) classical marker drug substrates, (c) class of drugs as substrates (Sartans, Statins etc.), (d) substrate preferences between related and unrelated CYPs, (e) man-made site-directed mutants' and naturally occurring mutants' reactivity and metabolic disposition, (f) drug-drug interactions, (g) overall affinities of drug substrate versus oxidized product, (h) meta-analysis of in silico versus experimental binding constants and reaction/residence times etc.

RESULTS

It was found that heme-centered dockings of the substrate/modulator drug molecules with the available CYP crystal structures gave poor docking geometries and distances from Fe-heme centre. In conjunction with several other arguments, the findings discount the relevance of erstwhile hypothesis in many CYP systems. Consequently, the newly proposed hypothesis is deemed a viable alternate, as it satisfies Occam's razor.

CONCLUSIONS

The new proposal affords expanded scope for explaining the mechanism, kinetics and overall phenomenology of CYP mediated drug metabolism. It is now understood that the heme-iron and the hydrophobic distal pocket of CYPs serve primarily to stabilize the reactive intermediate (diffusible radical) and the surface or crypts of the apoprotein bind to the xenobiotic substrate (and in some cases, the heme distal pocket could also serve the latter function). Thus, CYPs enhance reaction rates and selectivity/specificity via a hitherto unrecognized modality.

Comparative pharmacokinetics of three SGLT-2 inhibitors sergliflozin, remogliflozin and ertugliflozin: an overview

1. Several sodium-glucose cotransporter-2 (SGLT-2) inhibitors are in clinical use for the management of type 2 diabetes. The objectives of the current review were: (a) to provide a comparative pharmacokinetics including absorption, distribution, metabolism and excretory (ADME) profiles of three SGLT-2 inhibitors namely: sergliflozin, remogliflozin and ertugliflozin; (b) to provide some perspectives on possible developmental issues. 2. Based on the half-life (t_1/2) values observed in humans, the rank order of the three SGLT-2 inhibitors was ertugliflozin (16 h) > remogliflozin (2-4 h) > sergliflozin (1-1.5 h). Therefore, while once a day dosing of ertugliflozin is possible, the other two drugs need to be dosed more frequently. Perhaps, the short t_1/2 of sergliflozin may have contributed for its discontinuation. 3. Although there was paucity of published data on the metabolism, transporter related and excretory aspects for sergliflozin, the other two drugs provided a differentiating profile. However, the compiled data suggested that there may be a minimal or no risk of pharmacokinetic drug interaction issues associated with any of the reviewed drugs. 4. Because of the crowded development pipeline and approved SGLT-2 inhibitors, the safety and efficacy of sergliflozin, remogliflozin and ertugliflozin appear to be a key from differentiation perspective.

Chemical and microbiological stability studies of an aqueous solution of pravastatin sodium salt for drug therapy of the dysphagic patients

Objective

This study is aimed to improve dysphagic patient compliance under therapy with cholesterol-lowering drugs. Patients suffering severe dysphagia, who do not feed independently, receive enteral nutrition through feeding tube and they need alternative oral route also for the administration of pharmacological therapy. This research deals with the development and stability (chemical and microbiological) of an aqueous solution of pravastatin sodium salt that will be administered orally directly in the feeding tube starting from commercial tablets. Tablets formulation is the only pharmaceutical dosage form available on the market for this type of drug.

Methods

Pravastatin sodium salt tablets are dissolved in a preserved sodium bicarbonate solution at the final concentration of 4 mg/mL. Samples are stored in two different conditions until 60 days. The samples are prepared for high-performance liquid chromatography analysis coupled to a diode array detector (HPLC-DAD), microbiological analysis and pH measurements.

Results

The chemical stability of the solution performed with HPLC-DAD analysis shows peaks' overlapping, which are characteristic of pravastatin, and correspondence of the concentration of the active ingredient in the solution. The detected values are analysed by one-way analysis of variance showing no statistically significant differences. Microbiological analyses proved that there is not microbial growth. By considering the dilution factor applied, it was possible to express the result as <10 CFU/mL in the two different culture media.

Conclusion

This study demonstrated the possibility to reformulate pravastatin tablets as liquid pharmaceutical formulation for enteral administration with the aim of improving drug therapy in dysphagic patients.

Pediatric Statin Administration: Navigating a Frontier with Limited Data

Increasingly, children and adolescents with dyslipidemia qualify for pharmacologic intervention. As they are for adults, 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase inhibitors (statins) are the mainstay of pediatric dyslipidemia treatment when lifestyle modifications have failed. Despite the overall success of these drugs, the magnitude of variability in dose-exposure-response profiles contributes to adverse events and treatment failure. In children, the cause of treatment failures remains unclear. This review describes the updated guidelines for screening and management of pediatric dyslipidemia and statin disposition pathway to assist the provider in recognizing scenarios where alterations in dosage may be warranted to meet patients' specific needs.

The role of acid-base imbalance in statin-induced myotoxicity

Disturbances in acid-base balance, such as acidosis and alkalosis, have potential to alter the pharmacologic and toxicologic outcomes of statin therapy. Statins are commonly prescribed for elderly patients who have multiple comorbidities such as diabetes mellitus, cardiovascular, and renal diseases. These patients are at risk of developing acid-base imbalance. In the present study, the effect of disturbances in acid-base balance on the interconversion of simvastatin and pravastatin between lactone and hydroxy acid forms have been investigated in physiological buffers, human plasma, and cell culture medium over pH ranging from 6.8-7.8. The effects of such interconversion on cellular uptake and myotoxicity of statins were assessed in vitro using C2C12 skeletal muscle cells under conditions relevant to acidosis, alkalosis, and physiological pH. Results indicate that the conversion of the lactone forms of simvastatin and pravastatin to the corresponding hydroxy acid is strongly pH dependent. At physiological and alkaline pH, substantial proportions of simvastatin lactone (SVL; ∼87% and 99%, respectively) and pravastatin lactone (PVL; ∼98% and 99%, respectively) were converted to the active hydroxy acid forms after 24 hours of incubation at 37°C. At acidic pH, conversion occurs to a lower extent, resulting in greater proportion of statin remaining in the more lipophilic lactone form. However, pH alteration did not influence the conversion of the hydroxy acid forms of simvastatin and pravastatin to the corresponding lactones. Furthermore, acidosis has been shown to hinder the metabolism of the lactone form of statins by inhibiting hepatic microsomal enzyme activities. Lipophilic SVL was found to be more cytotoxic to undifferentiated and differentiated skeletal muscle cells compared with more hydrophilic simvastatin hydroxy acid, PVL, and pravastatin hydroxy acid. Enhanced cytotoxicity of statins was observed under acidic conditions and is attributed to increased cellular uptake of the more lipophilic lactone or unionized hydroxy acid form. Consequently, our results suggest that comorbidities associated with acid-base imbalance can play a substantial role in the development and potentiation of statin-induced myotoxicity.

Pregabalin- and azithromycin-induced rhabdomyolysis with purpura: An unrecognized interaction: A case report

INTRODUCTION

Rhabdomyolysis associated with the use of pregabalin or azithromycin has been demonstrated to be a rare but potentially life-threatening adverse event. Here, we report an extremely rare case of rhabdomyolysis with purpura in a patient who had used pregabalin and azithromycin.

PRESENTATION OF CASE

We present the case of a 75-year-old woman with a history of fibromyalgia who was admitted with mild limb weakness and lower abdominal purpura. She was prescribed pregabalin (75mg, twice daily) for almost 3 months to treat chronic back pain. Her medical history revealed that 3days before admission, she began experiencing acute bronchitis and was treated with a single dose of azithromycin (500mg). She had developed rapid onset severe myalgia, mild whole body edema, muscle weakness leading to gait instability, abdominal purpura and tender purpura on the lower extremities. Laboratory values included a white blood cell count of 25,400/mL and a creatinine phosphokinase (CPK) concentration of 1250 IU/L. Based on these findings and the patient's clinical history, a diagnosis of pregabalin- and azithromycin-induced rhabdomyolysis was made.

DISCUSSION

The long-term use of pregabalin and the initiation azithromycin therapy followed by a rapid onset of rhabdomyolysis is indicative of a drug interaction between pregabalin and azithromycin.

CONCLUSION

We report an extremely rare case of rhabdomyolysis with purpura caused by a drug interaction between pregabalin and azithromycin. However, the mechanisms of the interactions between azithromycin on the pregabalin are still unknown.

In vitro and clinical evaluation of OATP-mediated drug interaction potential of sacubitril/valsartan (LCZ696)

WHAT IS KNOWN AND OBJECTIVE

Sacubitril/valsartan (LCZ696) has been recently approved for the treatment of heart failure (HF) patients with reduced ejection fraction. Several HF patients receive statins as co-medication.

METHODS

Because clearance of statins is meditated via OATP1B1/1B3, the inhibition potential of these transporters by LCZ696 analytes was evaluated in vitro. Furthermore, an open-label, fixed-sequence clinical study was conducted to determine the effect of LCZ696 on the exposure of simvastatin and its active metabolite simvastatin acid. In this clinical study, 26 healthy subjects received simvastatin 40 mg alone or in combination with LCZ696 or after 1 or 2 h of LCZ696 dosing.

RESULTS AND DISCUSSION

Although no significant inhibition by LBQ657 (an active metabolite of sacubitril) and valsartan was observed, sacubitril inhibited OATP1B1 and OATP1B3 in vitro, with IC50 of 1·91 and 3·81 μm, respectively. Upon co-administration of simvastatin with LCZ696, the Cmax of simvastatin and simvastatin acid decreased by 7% and 13%, respectively. When administered 1 h after LCZ696 dosing, the corresponding Cmax of simvastatin and simvastatin acid decreased by 16% and 4%, respectively. When administered 2 h after LCZ696 dosing, the Cmax of simvastatin decreased by 33% and that of simvastatin acid increased by 16%. However, no notable changes were observed in the AUCs of simvastatin or simvastatin acid upon co-administration or time-separated administration with LCZ696. No notable impact of simvastatin co-administration was observed on the pharmacokinetics of LCZ696 analytes. LCZ696 and simvastatin were generally well tolerated when administered alone or in combination.

WHAT IS NEW AND CONCLUSIONS

Overall, the results of this study suggest that although sacubitril inhibited OATP1B1 and OATP1B3 in vitro, it does not translate into any clinically relevant in vivo effect.

Synergistic Antiproliferative Effects of Zoledronic Acid and Fluvastatin on Human Pancreatic Cancer Cell Lines: An in Vitro Study

Bisphosphonates and statins are known to have antitumor activities against different types of cancer cell lines. In the present study, we investigated the antiproliferative effects of the combination of zoledronic acid (ZOL), a bisphophosphonate, and fluvastatin (FLU), a statin, in vitro on two types of human pancreatic cancer cell lines, Mia PaCa-2 and Suit-2. The pancreatic cancer cell lines were treated with ZOL and FLU both individually and in combination to evaluate their antiproliferative effects using WST-8 cell proliferation assay. In this study, we demonstrated a potent synergistic antiproliferative effect of both drugs when used in combination in both cell lines. Moreover, we studied the molecular mechanism behind this synergistic effect, which was inhibited by the addition of the mevalonate pathway products, farnesyl pyrophosphate (FPP) and geranylgeranyl pyrophosphate (GGPP). Furthermore, we aimed to determine the effect of ZOL and FLU combination on RhoA and Ras guanosine 5'-triphosphate (GTP)-proteins. The combination induced a marked accumulation in RhoA and unprenylated Ras. GGPP and FPP reversed the increase in the amount of both proteins. These results indicated that the combination treatment impaired RhoA and Ras signaling pathway by the inhibition of geranylgeranylation and/or farnesylation. This study provides a potentially effective approach for the treatment of pancreatic cancer using a combination treatment of ZOL and FLU.

Statin drug-drug interactions in a Romanian community pharmacy

BACKGROUND AND AIM

Statins are frequently prescribed for patients with dyslipidemia and have a well-established safety profile. However, when associated with interacting dugs, the risk of adverse effects, especially muscular toxicity, is increased. The objective of this study was to identify, characterize and quantify the prevalence of the potential drug-drug interactions (pDDIs) of statins in reimbursed prescriptions from a community pharmacy in Bucharest.

METHODS

We analyzed the reimbursed prescriptions including statins collected during one month in a community pharmacy. The online program Medscape Drug Interaction Checker was used for checking the drug interactions and their classification based on severity: Serious - Use alternative, Significant - Monitor closely and Minor.

RESULTS

132 prescriptions pertaining to 125 patients were included in the analysis. Our study showed that 25% of the patients who were prescribed statins were exposed to pDDIs: 37 Serious and Significant interactions in 31 of the statins prescriptions. The statins involved were atorvastatin, simvastatin and rosuvastatin.

CONCLUSIONS

Statin pDDIs have a high prevalence and patients should be monitored closely in order to prevent the development of adverse effects that result from statin interactions.

SLCO1B1 polymorphism markedly affects the pharmacokinetics of lovastatin acid

OBJECTIVE

Organic anion transporting polypeptide 1B1 (OATP1B1, encoded by SLCO1B1 gene) is a hepatic uptake transporter, and its genetic variability is associated with pharmacokinetics and muscle toxicity risk of simvastatin. We examined the possible effects of variations in the SLCO1B1 gene on the pharmacokinetics of lovastatin in a prospective genotype panel study.

PARTICIPANTS AND METHODS

Seven healthy volunteers with the SLCO1B1*1B/*1B genotype, five with the SLCO1B1*5/*15 or *15/*15 genotype, and 15 with the SLCO1B1*1A/*1A genotype (controls) were recruited. Each study participant ingested a single 40-mg dose of lovastatin. Plasma concentrations of lovastatin (inactive lactone) and its active metabolite lovastatin acid were measured up to 24 h.

RESULTS

In the SLCO1B1*5/*15 or *15/*15 genotype group, the geometric mean Cmax and AUC0-24 of lovastatin acid were 340 and 286% of the corresponding values in the SLCO1B1*1A/*1A (reference) genotype group (P<0.005). In contrast, the AUC0-24 of lovastatin acid in the SLCO1B1*1B/*1B genotype group was only 68% of that in the reference genotype group (P=0.03). No statistically significant association was observed between the SLCO1B1 genotype and the pharmacokinetics of lovastatin lactone.

CONCLUSION

SLCO1B1*5/*15 and *15/*15 genotypes markedly increase the exposure to active lovastatin acid, but have no significant effect on lovastatin lactone, similar to their effects on simvastatin and simvastatin acid. Accordingly, it is probable that the risk of muscle toxicity during lovastatin treatment is increased in individuals carrying the SLCO1B1*5 or *15 allele. The SLCO1B1*1B/*1B genotype is associated with reduced lovastatin acid concentrations, consistent with enhanced hepatic uptake.

Clinical pharmacology profile of boceprevir, a hepatitis C virus NS3 protease inhibitor: focus on drug-drug interactions

Boceprevir is a potent, orally administered ketoamide inhibitor that targets the active site of the hepatitis C virus (HCV) non-structural (NS) 3 protease. The addition of boceprevir to peginterferon plus ribavirin resulted in higher rates of sustained virologic response (SVR) than for peginterferon plus ribavirin alone in phase III studies in both previously treated and untreated patients with HCV infection. Because boceprevir is metabolized by metabolic routes common to many other drugs, and is an inhibitor of cytochrome P450 (CYP) 3A4/5, there is a high potential for drug-drug interactions when boceprevir is administered with other therapies, particularly when treating patients with chronic HCV infection who are often receiving other medications concomitantly. Boceprevir is no longer widely used in the US or EU due to the introduction of second-generation treatments for HCV infection. However, in many other geographic regions, first-generation protease inhibitors such as boceprevir continue to form an important treatment option for patients with HCV infection. This review summarizes the interactions between boceprevir and other therapeutic agents commonly used in this patient population, indicating dose adjustment requirements where needed. Most drug interactions do not affect boceprevir plasma concentrations to a clinically meaningful extent, and thus efficacy is likely to be maintained when boceprevir is coadministered with the majority of other therapeutics. Overall, the drug-drug interaction profile of boceprevir suggests that this agent is suitable for use in a wide range of HCV-infected patients receiving concomitant therapies.

Mixed effects of OATP1B1, BCRP and NTCP polymorphisms on the population pharmacokinetics of pravastatin in healthy volunteers

1. Pravastatin is a 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor used for the treatment of hyperlipidaemia. This study aims to investigate the effects of genetic polymorphisms in OATP1B1, BCRP and NTCP on pravastatin population pharmacokinetics in healthy Chinese volunteers using a non-linear mixed-effect modelling (NONMEM) approach. A two-compartment model with a first-order absorption and elimination described plasma pravastatin concentrations well. 2. Genetic polymorphisms of rs4149056 (OATP1B1) and rs2306283 (OATP1B1) were found to be associated with a significant (p < 0.01) decrease in the apparent clearance from the central compartment (CL/F), while rs2296651 (NTCP) increased CL/F to a significant degree (p < 0.01). The combination of these three polymorphisms reduced the inter-individual variability of CL/F by 78.8%. 3. There was minimal effect of rs2231137 (BCRP) and rs2231142 (BCRP) on pravastatin pharmacokinetics (0.01 < p < 0.05), whereas rs11045819 (OATP1B1), rs1061018 (BCRP) and rs61745930 (NTCP) genotypes do not appear to be associated with pravastatin pharmacokinetics based on the population model (p > 0.05). 4. The current data suggest that the combination of rs4149056, rs2306283 and rs2296651 polymorphisms is an important determinant of pravastatin pharmacokinetics.

Gold-Catalyzed Cycloisomerization and Diels-Alder Reaction of 1,6-Diyne Esters with Alkenes and Diazenes to Hydronaphthalenes and -cinnolines

A method for the efficient preparation of hydronaphthalene and -cinnoline derivatives by Au(I)-catalyzed cycloisomerzation of 1,6-diyne esters followed by a Diels-Alder reaction with alkenes or diazenes under mild conditions at room temperature with catalyst loadings as low as 1 mol % is described.

Drug-drug interactions that interfere with statin metabolism

INTRODUCTION

Lipid-lowering drugs, especially hydroxymethylglutaryl-CoA reductase inhibitors (statins), are widely used in the treatment and prevention of atherosclerotic diseases. The benefits of statins are well documented. However, myotoxic side effects, which can sometimes be severe, including myopathy or rhabdomyolysis, have been associated with the use of statins. In some cases, this toxicity is associated with pharmacokinetic alterations. Potent inhibitors of CYP 3A4 significantly increase plasma concentrations of the active forms of simvastatin, lovastatin and atorvastatin. Fluvastatin is metabolized by CYP2C9, while pravastatin, rosuvastatin and pitavastatin are not susceptible to inhibition by any CYP.

AREAS COVERED

This review discusses the pharmacokinetic aspects of the drug-drug interaction with statins and genetic polymorphisms in CYPs, which are involved in the metabolism of statins, and highlights the importance of establishing a system utilizing electronic medical information practically to avoid adverse drug reactions.

EXPERT OPINION

An understanding of the mechanisms underlying statin interactions will help to minimize drug interactions and develop statins that are less prone to adverse interactions. Quantitatively analyzed information for the low-density lipoprotein cholesterol lowering effects of statin based on electronic medical records may be useful for avoiding the adverse effect of statins.

Key factors which concur to the correct therapeutic evaluation of herbal products in free radical-induced diseases

For many years now the world's scientific literature has been perfused with articles on the therapeutic potential of natural products, the vast majority of which have herbal origins, as in the case of free radical-induced diseases. What is often overlooked is the effort of researchers who take into consideration the preclinical and clinical evaluation of these herbal products, in order to demonstrate the therapeutic efficacy and safety. The first critical issue to be addressed in the early stages of the preclinical studies is related to pharmacokinetics, which is sometimes not very favorable, of some of these products, which limits the bioavailability after oral intake. In this regard, it is worthy underlining how it is often unethical to propose the therapeutic efficacy of a compound on the basis of preclinical results obtained with far higher concentrations to those which, hopefully, could be achieved in organs and tissues of subjects taking these products by mouth. The most widely used approach to overcome the problem related to the low bioavailability involves the complexation of the active ingredients of herbal products with non-toxic carriers that facilitate the absorption and distribution. Even the induction or inhibition of drug metabolizing enzymes by herbal products, and the consequent variations of plasma concentrations of co-administered drugs, are phenomena to be carefully evaluated as they can give rise to side-effects. This risk is even greater when considering that people lack the perception of the risk arising from an over use of herbal products that, by their very nature, are considered risk-free.

Cardiac allograft vasculopathy: diagnosis, therapy, and prognosis

Development of cardiac allograft vasculopathy represents the major determinant of long-term survival in patients after heart transplantation. Due to graft denervation, these patients seldom present with classic symptoms of angina pectoris, and the first clinical presentations are progressive heart failure or sudden cardiac death. Although coronary angiography remains the routine technique for coronary artery disease detection, it is not sensitive enough for screening purposes. This is especially the case in the first year after transplantation when diffuse and concentric vascular changes can be easily detected only by intravascular ultrasound. The treatment of the established vasculopathy is disappointing, so the primary effort should be directed toward early prevention and diagnosis. Due to diffuse vascular changes, revascularization procedures are restricted only to a relatively small proportion of patients with favorable coronary anatomy. Percutaneous coronary intervention is preferred over surgical revascularization since it leads to better acute results and patient survival. Although there is no proven long-term advantage of drug-eluting stents for the treatment of in-stent restenosis, they are preferred over bare-metal stents. Severe vasculopathy has a poor prognosis and the only definitive treatment is retransplantation. This article reviews the present knowledge on the pathogenesis, diagnosis, treatment, and prognosis of cardiac allograft vasculopathy.

Chronic cholesterol depletion by lovastatin suppresses MUC5AC gene expression in human airway epithelial cells

BACKGROUND

We recently showed that acute cholesterol depletion in the plasma membrane of NCI-H292 cells by methyl-β-cyclodextrin suppressed IL-1beta-induced MUC5AC gene expression. Because cholesterol depletion is clinically used as an antihypersecretory method, chronic cholesterol depletion by lovastatin is more rational and safe than acute depletion. Therefore, we sought to investigate whether chronic cholesterol depletion by lovastatin is feasible and, if so, suppresses the expression of GMUC5AC in NCI-H292 cells. We also considered whether this alteration of MUC5AC expression is related to IL-1 receptor and mitogen-activated protein kinase (MAPK) activity.

METHODS

After NCI-H292 cells were pretreated with 10 μM of lovastatin for 1 hour, 10 ng/mL of IL-1β was added and cotreated with lovastatin for 24 hours. MUC5AC mRNA expression was then determined by real-time polymerase chain reaction. Cholesterol depletion by lovastatin was measured by modified microenzymatic fluorescence assay and filipin staining. The phosphorylation of IL-1 receptor, ERK, and p38 MAPK was analyzed by Western blot.

RESULTS

Cholesterol in the plasma membrane was significantly depleted by lovastatin treatment for 24 hours. IL-1beta0-induced MUC5AC mRNA expression was decreased by lovastatin and this decrease occurred IL-1 receptor specifically. Lovastatin suppressed the activation of p38 MAPK but not ERK1/2 in cells activated with IL-1beta. This result suggests that lovastatin-mediated suppression of IL-1beta-induced MUC5AC mRNA operated only viathe p38 MAPK-dependent pathway.

CONCLUSION

Chronic cholesterol depletion in the plasma membrane of NCI-H292 cells may be considered an antihypersecretory method, because it effectively inhibits mucin gene expression of human airway epithelial cells.

A multicenter phase I study of pazopanib in combination with paclitaxel in first-line treatment of patients with advanced solid tumors

This study was designed to evaluate the safety, pharmacokinetics, and clinical activity of pazopanib combined with paclitaxel to determine the recommended phase II dose in the first-line setting in patients with advanced solid tumors. Patients were enrolled in a 3+3 dose-escalation design to determine the maximum tolerated regimen (MTR) of once daily pazopanib plus paclitaxel administered every 3 weeks at four dose levels (DL1-4). Safety, pharmacokinetics, pharmacogenetics, and disease assessments were performed. Twenty-eight patients received treatment. One patient at DL1 had dose-limiting toxicity (DLT) of elevated hepatic enzymes. After pazopanib discontinuation, liver enzyme concentrations remained high until a concurrent medication, simvastatin, was discontinued. This patient had the defective CYP2C8*3*3 genotype. At DL2, 1 patient had DLT of elevated hepatic enzymes with rash and 1 patient had DLT of rash. The MTR was paclitaxel 150 mg/m(2) plus pazopanib 800 mg. The most common toxicities were alopecia, fatigue, hypertension, nausea, diarrhea, dysgeusia, neutropenia, myalgia, hair color changes, and peripheral neuropathy. Coadministration of pazopanib and paclitaxel resulted in a 38% increase in systemic exposure to paclitaxel, relative to administration of paclitaxel alone, at the MTR. Of the 28 patients treated with the combination, 10 achieved a partial response and 10 achieved stable disease of ≥12 weeks. Pazopanib 800 mg daily plus paclitaxel 150 mg/m(2) every 3 weeks was the recommended phase II dose, with a manageable safety profile, and with clinical activity in both melanoma and non-small cell lung cancer that suggest further evaluation of this combination is warranted.

[Risk of pharmacological interactions due to the co-administration of statins and cytochrome P450 isoenzyme 3A4-metabolized drugs: multicentre, crossover study]

BACKGROUND AND OBJECTIVES

Statins are safe but have a significant potential for pharmacological interactions. The objective of the study was to evaluate the prevalence of potential interactions throughout the cytochrome P450 isoenzyme 3A4 (CYP3A4) system in a large sample of statin-treated subjects and to determine which factors, from the patient and the physician, were associated with a higher risk of interactions.

PATIENTS AND METHODS

This is an observational, cross-over, population study that included 7,880 subjects treated with statins. Both data from patients and from the1,681 participating physicians were recorded and analyzed.

RESULTS

Fifty-nine percent of the participants were receiving a statin metabolized by the CYP3A4, and 21.5% of all participants received a drug, different from a statin, metabolized by the CYP3A4. There were no differences in the frequency of utilization of statins metabolized or not by the CYP3A4 in relation to the simultaneous prescription of drugs metabolized by the same pathway (22 vs. 21%, respectively). Globally, 12.9% of all participants were at risk of an interaction. These patients were older, received a higher number of drugs and had more comorbidity. Sixty percent of the physicians mentioned that the possibility of an interaction greatly conditioned their selection of a particular statin. Likewise, 56% of them had software that alerted of possible interactions. These aspects, however, did not influence the number of patients at risk of interactions.

CONCLUSION

The proportion of statin-treated patients at risk of interaction is elevated. Physicians do not usually pay attention to this possibility despite having available alert software and therapeutic alternatives.

Anti-cancer potential of MAPK pathway inhibition in paragangliomas-effect of different statins on mouse pheochromocytoma cells

To date, malignant pheochromocytomas and paragangliomas (PHEOs/PGLs) cannot be effectively cured and thus novel treatment strategies are urgently needed. Lovastatin has been shown to effectively induce apoptosis in mouse PHEO cells (MPC) and the more aggressive mouse tumor tissue-derived cells (MTT), which was accompanied by decreased phosphorylation of mitogen-activated kinase (MAPK) pathway players. The MAPK pathway plays a role in numerous aggressive tumors and has been associated with a subgroup of PHEOs/PGLs, including K-RAS-, RET-, and NF1-mutated tumors. Our aim was to establish whether MAPK signaling may also play a role in aggressive, succinate dehydrogenase (SDH) B mutation-derived PHEOs/PGLs. Expression profiling and western blot analysis indicated that specific aspects of MAPK-signaling are active in SDHB PHEOs/PGLs, suggesting that inhibition by statin treatment could be beneficial. Moreover, we aimed to assess whether the anti-proliferative effect of lovastatin on MPC and MTT differed from that exerted by fluvastatin, simvastatin, atorvastatin, pravastatin, or rosuvastatin. Simvastatin and fluvastatin decreased cell proliferation most effectively and the more aggressive MTT cells appeared more sensitive in this respect. Inhibition of MAPK1 and 3 phosphorylation following treatment with fluvastatin, simvastatin, and lovastatin was confirmed by western blot. Increased levels of CASP-3 and PARP cleavage confirmed induction of apoptosis following the treatment. At a concentration low enough not to affect cell proliferation, spontaneous migration of MPC and MTT was significantly inhibited within 24 hours of treatment. In conclusion, lipophilic statins may present a promising therapeutic option for treatment of aggressive human paragangliomas by inducing apoptosis and inhibiting tumor spread.

Dietary modulators of statin efficacy in cardiovascular disease and cognition

Cardiovascular disease remains the leading cause of morbidity and mortality in the United States and other developed countries, and is fast growing in developing countries, particularly as life expectancy in all parts of the world increases. Current recommendations for the prevention of cardiovascular disease issued jointly from the American Academy of Cardiology and American Heart Association emphasize that lifestyle modification should be incorporated into any treatment plan, including those on statin drugs. However, there is a dearth of data on the interaction between diet and statins with respect to additive, complementary or antagonistic effects. This review collates the available data on the interaction of statins and dietary patterns, cognition, genetics and individual nutrients, including vitamin D, niacin, omega-3 fatty acids, fiber, phytochemicals (polyphenols and stanols) and alcohol. Of note, although the available data is summarized, the scope is limited, conflicting and disparate. In some cases it is likely there is unrecognized synergism. Virtually no data are available describing the interactions of statins with dietary components or dietary pattern in subgroups of the population, particularly those who may benefit most were positive effects identified. Hence, it is virtually impossible to draw any firm conclusions at this time. Nevertheless, this area is important because were the effects of statins and diet additive or synergistic harnessing the effect could potentially lead to the use of a lower intensity statin or dose.

Drug-drug interactions between HMG-CoA reductase inhibitors (statins) and antiviral protease inhibitors

The HMG-CoA reductase inhibitors are a class of drugs also known as statins. These drugs are effective and widely prescribed for the treatment of hypercholesterolemia and prevention of cardiovascular morbidity and mortality. Seven statins are currently available: atorvastatin, fluvastatin, lovastatin, pitavastatin, pravastatin, rosuvastatin and simvastatin. Although these drugs are generally well tolerated, skeletal muscle abnormalities from myalgia to severe lethal rhabdomyolysis can occur. Factors that increase statin concentrations such as drug-drug interactions can increase the risk of these adverse events. Drug-drug interactions are dependent on statins' pharmacokinetic profile: simvastatin, lovastatin and atorvastatin are metabolized through cytochrome P450 (CYP) 3A, while the metabolism of the other statins is independent of this CYP. All statins are substrate of organic anion transporter polypeptide 1B1, an uptake transporter expressed in hepatocyte membrane that may also explain some drug-drug interactions. Many HIV-infected patients have dyslipidemia and comorbidities that may require statin treatment. HIV-protease inhibitors (HIV PIs) are part of recommended antiretroviral treatment in combination with two reverse transcriptase inhibitors. All HIV PIs except nelfinavir are coadministered with a low dose of ritonavir, a potent CYP3A inhibitor to improve their pharmacokinetic properties. Cobicistat is a new potent CYP3A inhibitor that is combined with elvitegravir and will be combined with HIV-PIs in the future. The HCV-PIs boceprevir and telaprevir are both, to different extents, inhibitors of CYP3A. This review summarizes the pharmacokinetic properties of statins and PIs with emphasis on their metabolic pathways explaining clinically important drug-drug interactions. Simvastatin and lovastatin metabolized through CYP3A have the highest potency for drug-drug interaction with potent CYP3A inhibitors such as ritonavir- or cobicistat-boosted HIV-PI or the hepatitis C virus (HCV) PI, telaprevir or boceprevir, and therefore their coadministration is contraindicated. Atorvastatin is also a CYP3A substrate, but less potent drug-drug interactions have been reported with CYP3A inhibitors. Non-CYP3A-dependent statin concentrations are also affected although to a lesser extent when coadministered with HIV or HCV PIs, mainly through interaction with OATP1B1, and treatment should start with the lowest available statin dose. Effectiveness and occurrence of adverse effects should be monitored at regular time intervals.

HMG CoA reductase inhibitor treatment induces dysglycemia in renal allograft recipients

BACKGROUND

Dysglycemia and dyslipidemia are important metabolic complications of organ transplantation. Statins are widely used to control dyslipidemia; however, long-term use of statins is related to diabetes mellitus (DM) and impaired fasting glucose (IFG). The aim of this study was to evaluate the influence of statins on the development of dysglycemia (IFG and/or DM) in renal allograft recipients.

METHODS

A total of 394 patients without previously known DM or IFG who underwent kidney transplantation were enrolled. Patients were grouped into the two groups according to the use of statin (control, n=149; statin, n=245). The major statins used were fluvastatin (80 mg/d, n=134) and atorvastatin (20 mg/d, n=111). We compared the incidence of IFG or DM during the follow-up period.

RESULTS

The incidence of IFG was higher in the statin group than that in the control group (28.6% vs. 8.7%, P<0.001). The incidence of dysglycemia was significantly higher in the statin group (40.0% vs. 15.4%, P=0.001). Time to development of dysglycemia after transplantation was shorter in the statin group than in the control group (38.8±29.7 vs. 47.2±23.3 months, P=0.002). Statin use was associated with an increased risk for dysglycemia after adjustment for age, sex, body mass index, hypertension, cholesterol levels, hepatitis C infection, and type of immunosuppressant (hazard ratio=3.08, 95% confidence interval=1.91-4.98). The dysglycemic effect was more profound in the patients who used atorvastatin than in those who used fluvastatin (hazard ratio=2.21, 95% confidence interval=1.02-4.76).

CONCLUSION

Statin treatment is associated with an elevation in fasting plasma glucose and in the development of dysglycemia in renal allograft recipients.

Comparison of low-dose rosuvastatin with atorvastatin in lipid-lowering efficacy and safety in a high-risk pakistani cohort: an open-label randomized trial

Background. Treatment of hyperlipidemia is helpful in both primary and secondary prevention of coronary heart disease and stroke. Aim. To compare lipid-lowering efficacy of rosuvastatin with atorvastatin. Methodology. This open-label randomized controlled trial was carried out at 1 Mountain Medical Battalion from September 2012 to August 2013 on patients with type 2 diabetes, hypertension, myocardial infarction, or stroke, meriting treatment with a statin. Those with secondary causes of dyslipidemia were excluded. Blood samples for estimation of serum total cholesterol, triglycerides, HDL-C, and LDL-C were collected after a 12-hour fast. Patients were randomly allocated to receive either atorvastatin 10 mg HS or rosuvastatin 5 mg HS daily. Lipid levels were rechecked after six weeks. Results. Atorvastatin was used in 63 patients and rosuvastatin in 66. There was a greater absolute and percent reduction in serum LDL-C levels with rosuvastatin as compared to atorvastatin (0.96 versus 0.54 mg/dL; P = 0.011 and 24.34 versus 13.66%; P = 0.045), whereas reduction in all other fractions was equal. Myalgias were seen in 5 (7.94%) patients treated with atorvastatin and 8 (12.12%) patients treated with rosuvastatin (P: 0.432). Conclusion. Rosuvastatin produces a greater reduction in serum LDL-C levels and should therefore be preferred over atorvastatin.

Targeting epidermal lipids for treatment of Mendelian disorders of cornification

BACKGROUND

Inherited ichthyoses or Mendelian disorders of cornification (MeDOC) are clinically heterogeneous disorders with high unmet therapeutic needs, which are characterized by skin hyperkeratosis and scaling. Some MeDOC types are associated with defects of the epidermal lipid metabolism, resulting in perturbed barrier permeability and subsequent epidermal hyperplasia, hyperkeratosis and inflammation. An example is the CHILD (congenital hemidysplasia with ichthyosiform nevus and limb defects) syndrome, an X-linked dominant multisystem MeDOC caused by mutations in the NSDHL (NAD(P)H steroid dehydrogenase-like protein) gene, which is involved in the distal cholesterol biosynthetic pathway. The skin manifestations of the CHILD syndrome have been attributed to two major mechanisms: deficiency of cholesterol, probably influencing the proper corneocyte membrane formation, and toxic accumulation of aberrant steroid precursors.

METHODS

Here we addressed the efficacy of an ointment containing cholesterol and simvastatin, an agent inhibiting endogenous cholesterol synthesis in a compassionate-use treatment of three patients with CHILD syndrome. To test the specificity of this therapeutic approach, we applied the same topical treatment to two patients with other types of MeDOC with disturbed skin lipid metabolism.

RESULTS

The therapy with simvastatin and cholesterol was highly effective and well-tolerated by the CHILD syndrome patients; only lesions in the body folds represented a therapeutic challenge. No improvement was noted in the patients with other types of MeDOC.

CONCLUSIONS

This therapy is inexpensive and accessible to every patient with CHILD syndrome, because both simvastatin and cholesterol are available worldwide. Our data provide initial evidence of the specificity of the therapeutic effect of the simvastatin-cholesterol ointment in CHILD syndrome in comparison to other types of MeDOC.

Statins in lymphangioleiomyomatosis. Simvastatin and atorvastatin induce differential effects on tuberous sclerosis complex 2-null cell growth and signaling

Mutations of the tumor suppressor genes tuberous sclerosis complex (TSC)1 and TSC2 cause pulmonary lymphangioleiomyomatosis (LAM) and tuberous sclerosis (TS). Current rapamycin-based therapies for TS and LAM have a predominantly cytostatic effect, and disease progression resumes with therapy cessation. Evidence of RhoA GTPase activation in LAM-derived and human TSC2-null cells suggests that 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitor statins can be used as potential adjuvant agents. The goal of this study was to determine which statin (simvastatin or atorvastatin) is more effective in suppressing TSC2-null cell growth and signaling. Simvastatin, but not atorvastatin, showed a concentration-dependent (0.5-10 μM) inhibitory effect on mouse TSC2-null and human LAM-derived cell growth. Treatment with 10 μM simvastatin induced dramatic disruption of TSC2-null cell monolayer and cell rounding; in contrast, few changes were observed in cells treated with the same concentration of atorvastatin. Combined treatment of rapamycin with simvastatin but not with atorvastatin showed a synergistic growth-inhibitory effect on TSC2-null cells. Simvastatin, but not atorvastatin, inhibited the activity of prosurvival serine-threonine kinase Akt and induced marked up-regulation of cleaved caspase-3, a marker of cell apoptosis. Simvastatin, but not atorvastatin, also induced concentration-dependent inhibition of p42/p44 Erk and mTORC1. Thus, our data show growth-inhibitory and proapoptotic effects of simvastatin on TSC2-null cells compared with atorvastatin. These findings have translational significance for combinatorial therapeutic strategies of simvastatin to inhibit TSC2-null cell survival in TS and LAM.

The pharmacogenomics of statins

The statin class of cholesterol-lowering drugs have been used for decades to successfully lower plasma cholesterol concentrations and cardiovascular risk. Adverse effects of statins are generally considered mild, but increase with age of patients and polypharmacy. One aspect of statin therapy that is still difficult for prescribers to predict is the individual's response to statin therapy. Recent advances in the field of pharmacogenomics have indicated variants of candidate genes that affect statin efficacy and safety. In this review, a number of candidates that affect statin pharmacokinetics and pharmacodynamics are discussed. Some of these candidates, in particular those involved in import and efflux of statins, have now been linked to increased risk of side effects. Furthermore, pharmacogenomic studies continue to reveal new players that are involved in the fine-tuning of the complex regulation of cholesterol homeostasis and response to statins.

Combined analysis of pharmacokinetic and efficacy data of preclinical studies with statins markedly improves translation of drug efficacy to human trials

Correct prediction of human pharmacokinetics (PK) and the safety and efficacy of novel compounds based on preclinical data, is essential but often fails. In the current study, we aimed to improve the predictive value of ApoE*3Leiden (E3L) transgenic mice regarding the cholesterol-lowering efficacy of various statins in humans by combining pharmacokinetic with efficacy data. The efficacy of five currently marketed statins (atorvastatin, simvastatin, lovastatin, pravastatin, and rosuvastatin) in hypercholesterolemic patients (low-density lipoprotein ≥ 160 mg/dl) was ranked based on meta-analysis of published human trials. Additionally, a preclinical combined PK efficacy data set for these five statins was established in E3L mice that were fed a high-cholesterol diet for 4 weeks, followed by 6 weeks of drug intervention in which statins were supplemented to the diet. Plasma and tissue levels of the statins were determined on administration of (radiolabeled) drugs (10 mg/kg p.o.). As expected, all statins reduced plasma cholesterol in the preclinical model, but a direct correlation between cholesterol lowering efficacy of the different statins in mice and in humans did not reach statistical significance (R(2) = 0.11, P < 0.57). It is noteworthy that, when murine data were corrected for effective liver uptake of the different statins, the correlation markedly increased (R(2) = 0.89, P < 0.05). Here we show for the first time that hepatic uptake of statins is related to their cholesterol-lowering efficacy and provide evidence that combined PK and efficacy studies can substantially improve the translational value of the E3L mouse model in the case of statin treatment. This strategy may also be applicable for other classes of drugs and other preclinical models.

Pharmacokinetics of high-dose simvastatin in refractory and relapsed chronic lymphocytic leukemia patients

PURPOSE

To evaluate the pharmacokinetics of simvastatin at the maximum tolerated dose (MTD) of 7.5 mg/kg, twice daily, in the context of a pilot trial enrolling patients with recurrent and refractory chronic lymphocytic leukemia.

METHODS

Patients received simvastatin orally at MTD for 7 days during a 21-day cycle for 6 cycles. Blood samples were collected during cycle 1. Simvastatin lactone and carboxylate concentrations were measured in plasma and peripheral blood mononuclear cells (PBMCs) using a validated HPLC-MS/MS assay.

RESULTS

Patients accrued to this study showed high variability in their exposure to simvastatin. Exposure was dose proportional (AUC and C max) as compared to those receiving standard hyperlipidemia therapy. Peak plasma concentrations ranged from 0.08 to 2.2 and from 0.03 to 0.6 μM for simvastatin lactone and carboxylate, respectively.

CONCLUSION

Our study shows that when simvastatin is administered at its MTD, only low micro-molar concentrations are achieved in plasma and PBMCs, which is consistent with the results observed in previous studies with lovastatin, but far lower than the concentrations required for anticancer effects in vitro. However, whether simvastatin at its MTD can confer therapeutic benefits to patients still remains to be determined.

Transporters and drug-drug interactions: important determinants of drug disposition and effects

Uptake and efflux transporters determine plasma and tissue concentrations of a broad variety of drugs. They are localized in organs such as small intestine, liver, and kidney, which are critical for drug absorption and elimination. Moreover, they can be found in important blood-tissue barriers such as the blood-brain barrier. Inhibition or induction of drug transporters by coadministered drugs can alter pharmacokinetics and pharmacodynamics of the victim drugs. This review will summarize in particular clinically observed drug-drug interactions attributable to inhibition or induction of intestinal export transporters [P-glycoprotein (P-gp), breast cancer resistance protein (BCRP)], to inhibition of hepatic uptake transporters [organic anion transporting polypeptides (OATPs)], or to inhibition of transporter-mediated [organic anion transporters (OATs), organic cation transporter 2 (OCT2), multidrug and toxin extrusion proteins (MATEs), P-gp] renal secretion of xenobiotics. Available data on the impact of nutrition on transport processes as well as genotype-dependent, transporter-mediated drug-drug interactions will be discussed. We will also present and discuss data on the variable extent to which information on the impact of transporters on drug disposition is included in summaries of product characteristics of selected countries (SPCs). Further work is required regarding a better understanding of the role of the drug metabolism-drug transport interplay for drug-drug interactions and on the extrapolation of in vitro findings to the in vivo (human) situation.

Pharmacogenomics of lipid-lowering therapies

Statins are the most widely used group of lipid-lowering drugs and they have been shown to be effective in the prevention of cardiovascular disease, primarily by reducing plasma low-density lipoprotein cholesterol concentrations and possibly through other pleiotropic effects. However, there are large variations in lipid responses to statins and some patients have intolerable muscle adverse drug reactions, which may in part be related to genetic factors. In the last decade, pharmacogenetic studies on statins ranging from the candidate gene approach to the more recent genome-wide association studies have provided evidence that genetic variations play an important role in determining statin responses. This review summarizes the current understanding on the pharmacogenomics of statins and other lipid-lowering drugs in current use.

Regulation of cholesterol homeostasis

Hypercholesterolemia is an important risk factor for cardiovascular disease. It is caused by a disturbed balance between cholesterol secretion into the blood versus uptake. The pathways involved are regulated via a complex interplay of enzymes, transport proteins, transcription factors and non-coding RNA's. The last two decades insight into underlying mechanisms has increased vastly but there are still a lot of unknowns, particularly regarding intracellular cholesterol transport. After decades of concentration on the liver, in recent years the intestine has come into focus as an important control point in cholesterol homeostasis. This review will discuss current knowledge of cholesterol physiology, with emphasis on cholesterol absorption, cholesterol synthesis and fecal excretion, and new (possible) therapeutic options for hypercholesterolemia.

Pharmacokinetic evaluation of the interaction between hepatitis C virus protease inhibitor boceprevir and 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors atorvastatin and pravastatin

Boceprevir is a potent orally administered inhibitor of hepatitis C virus and a strong, reversible inhibitor of CYP3A4, the primary metabolic pathway for many 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors. Thus, the aim of the present study was to investigate drug-drug interactions between atorvastatin or pravastatin and boceprevir. We conducted a single-center, open-label, fixed-sequence, one-way-crossover study with 20 healthy adult volunteers. Subjects received single-dose atorvastatin (40 mg) or pravastatin (40 mg) on day 1, followed by boceprevir (800 mg three times daily) for 7 to 10 days. Repeat single doses of atorvastatin or pravastatin were administered in the presence of steady-state boceprevir. Atorvastatin exposure increased in the presence of boceprevir, with atorvastatin area under the concentration-time curve from time zero to infinity after single dosing (AUC(inf)) increasing 2.3-fold (90% confidence interval [CI], 1.85, 2.90) and maximum observed concentration in plasma (Cmax) 2.7-fold (90% CI, 1.81, 3.90). Pravastatin exposure was slightly increased in the presence of boceprevir, with pravastatin AUC(inf) increasing 1.63-fold (90% CI, 1.03, 2.58) and C(max) 1.49-fold (90% CI, 1.03, 2.14). Boceprevir exposure was generally unchanged when the drug was coadministered with atorvastatin or pravastatin. All adverse events were mild and consistent with the known safety profile of boceprevir. The observed 130% increase in AUC of atorvastatin supports the use of the lowest possible effective dose of atorvastatin when coadministered with boceprevir, without exceeding a maximum daily dose of 40 mg. The observed 60% increase in pravastatin AUC with boceprevir coadministration supports the initiation of pravastatin treatment at the recommended dose when coadministered with boceprevir, with close clinical monitoring.