Cholesteryl Ester Transfer Protein Inhibitor Torcetrapib and Off-Target Toxicity

Atherosclerotic plaque stabilization and regression: a review of clinical evidence

Atherosclerotic plaque results from a complex interplay between lipid deposition, inflammatory changes, cell migration and arterial wall injury. Over the past two decades, clinical trials utilizing invasive arterial imaging modalities, such as intravascular ultrasonography, have shown that reducing levels of atherogenic lipoproteins, mainly serum LDL-cholesterol (LDL-C), to very low levels can safely reduce overall atherosclerotic plaque burden and favourably modify plaque composition. Classically, this outcome has been achieved with intensive statin therapy. Since 2016, newer and potent lipid-lowering strategies, such as proprotein convertase subtilisin-kexin type 9 inhibition, have shown incremental effects on plaque regression and risk of clinical events. Despite maximal reduction in plasma LDL-C levels, considerable residual cardiovascular risk remains in some patients. Therefore, there is a need to study therapeutic approaches that address residual risk beyond LDL-C reduction to promote plaque stabilization or regression. Contemporary imaging modalities, such as coronary computed tomography angiography, enable non-invasive assessment of the overall atherosclerotic plaque burden as well as of certain local plaque characteristics. This technology could allow further study of plaque stabilization and regression using novel therapeutic approaches. Non-invasive plaque assessment might also offer the potential to guide personalized management strategies if validated for this purpose.

A new risk factor for coronary artery disease can be detected by an ApoA1 mAb-based assay

BACKGROUND

This study aimed to find coronary artery disease (CAD) related apolipoprotein A1 (ApoA1) monoclonal antibody (mAb) and to evaluate the diagnostic value of the assay based on it.

METHODS

Patients with CAD diagnosed by coronary angiography (disease group, n = 180) and healthy subjects (control group, n = 199) were recruited. The correlation between methods and CAD were evaluated by Spearman's rank correlation coefficients. Receiver operating characteristic (ROC) curve analysis was used to evaluate the auxiliary diagnostic value of methods for CAD. Odds ratios (ORs) of the test results in CAD were estimated using logistic regression analysis.

RESULTS

Measurements from an ApoA1 mAb were found significantly positively correlated with CAD (r = 0.243, P < 0.01), unlike the measurements from the ApoA1 pAb were negatively correlated with CAD (r = -0.341, P < 0.001). The areas under the ROC curve of the ApoA1 mAb and pAb measurements were 0.704 and 0.563, respectively, in patients with normal HDL-C levels. ApoA1 values from the mAb assay had a significant positive impact on CAD risk.

CONCLUSION

An ApoA1 mAb-based assay can distinguish a high-density lipoprotein (HDL) subclass positively related to CAD, which can be used to improve and reappraise CAD risk assessment.

Structure-based mechanism and inhibition of cholesteryl ester transfer protein

PURPOSE OF REVIEW

Cholesteryl ester transfer proteins (CETP) regulate plasma cholesterol levels by transferring cholesteryl esters (CEs) among lipoproteins. Lipoprotein cholesterol levels correlate with the risk factors for atherosclerotic cardiovascular disease (ASCVD). This article reviews recent research on CETP structure, lipid transfer mechanism, and its inhibition.

RECENT FINDINGS

Genetic deficiency in CETP is associated with a low plasma level of low-density lipoprotein cholesterol (LDL-C) and a profoundly elevated plasma level of high-density lipoprotein cholesterol (HDL-C), which correlates with a lower risk of atherosclerotic cardiovascular disease (ASCVD). However, a very high concentration of HDL-C also correlates with increased ASCVD mortality. Considering that the elevated CETP activity is a major determinant of the atherogenic dyslipidemia, i.e., pro-atherogenic reductions in HDL and LDL particle size, inhibition of CETP emerged as a promising pharmacological target during the past two decades. CETP inhibitors, including torcetrapib, dalcetrapib, evacetrapib, anacetrapib and obicetrapib, were designed and evaluated in phase III clinical trials for the treatment of ASCVD or dyslipidemia. Although these inhibitors increase in plasma HDL-C levels and/or reduce LDL-C levels, the poor efficacy against ASCVD ended interest in CETP as an anti-ASCVD target. Nevertheless, interest in CETP and the molecular mechanism by which it inhibits CE transfer among lipoproteins persisted. Insights into the structural-based CETP-lipoprotein interactions can unravel CETP inhibition machinery, which can hopefully guide the design of more effective CETP inhibitors that combat ASCVD. Individual-molecule 3D structures of CETP bound to lipoproteins provide a model for understanding the mechanism by which CETP mediates lipid transfer and which in turn, guide the rational design of new anti-ASCVD therapeutics.

ApoA-I Infusion Therapies Following Acute Coronary Syndrome: Past, Present, and Future

PURPOSE OF REVIEW

The elevated adverse cardiovascular event rate among patients with low high-density lipoprotein cholesterol (HDL-C) formed the basis for the hypothesis that elevating HDL-C would reduce those events. Attempts to raise endogenous HDL-C levels, however, have consistently failed to show improvements in cardiovascular outcomes. However, steady-state HDL-C concentration does not reflect the function of this complex family of particles. Indeed, HDL functions correlate only weakly with serum HDL-C concentration. Thus, the field has pivoted from simply raising the quantity of HDL-C to a focus on improving the putative anti-atherosclerotic functions of HDL particles. Such functions include the ability of HDL to promote the efflux of cholesterol from cholesterol-laden macrophages. Apolipoprotein A-I (apoA-I), the signature apoprotein of HDL, may facilitate the removal of cholesterol from atherosclerotic plaque, reduce the lesional lipid content and might thus stabilize vulnerable plaques, thereby reducing the risk of cardiac events. Infusion of preparations of apoA-I may improve cholesterol efflux capacity (CEC). This review summarizes the development of apoA-I therapies, compares their structural and functional properties and discusses the findings of previous studies including their limitations, and how CSL112, currently being tested in a phase III trial, may overcome these challenges.

RECENT FINDINGS

Three major ApoA-I-based approaches (MDCO-216, CER-001, and CSL111/CSL112) have aimed to enhance reverse cholesterol transport. These three therapies differ considerably in both lipid and protein composition. MDCO-216 contains recombinant ApoA-I Milano, CER-001 contains recombinant wild-type human ApoA-I, and CSL111/CSL112 contains native ApoA-I isolated from human plasma. Two of the three agents studied to date (apoA-1 Milano and CER-001) have undergone evaluation by intravascular ultrasound imaging, a technique that gauges lesion volume well but does not assess other important variables that may relate to clinical outcomes. ApoA-1 Milano and CER-001 reduce lecithin-cholesterol acyltransferase (LCAT) activity, potentially impairing the function of HDL in reverse cholesterol transport. Furthermore, apoA-I Milano can compete with and alter the function of the recipient's endogenous apoA-I. In contrast to these agents, CSL112, a particle formulated using human plasma apoA-I and phosphatidylcholine, increases LCAT activity and does not lead to the malfunction of endogenous apoA-I. CSL112 robustly increases cholesterol efflux, promotes reverse cholesterol transport, and now is being tested in a phase III clinical trial. Phase II-b studies of MDCO-216 and CER-001 failed to produce a significant reduction in coronary plaque volume as assessed by IVUS. However, the investigation to determine whether the direct infusion of a reconstituted apoA-I reduces post-myocardial infarction coronary events is being tested using CSL112, which is dosed at a higher level than MDCO-216 and CER-001 and has more favorable pharmacodynamics.

Traditional Risk Factors are Causally Related to Carotid Intima-Media Thickness Progression: Inferences from Observational Cohort Studies and Interventional Trials

In the present review, associations between traditional vascular risk factors (VRFs) and carotid intimamedial thickness progression (C-IMTp) as well as the effects of therapies for VRFs control on C-IMTp were appraised to infer causality between each VRF and C-IMTp. Cohort studies indicate that smoking, binge drinking, fatness, diabetes, hypertension and hypercholesterolemia are associated with accelerated C-IMTp. An exception is physical activity, with mixed data. Interventions for the control of obesity, diabetes, hypertension and hypercholesterolemia decelerate C-IMTp. Conversely, scarce information is available regarding the effect of smoking cessation, stop of excessive alcohol intake and management of the metabolic syndrome. Altogether, these data support a causative role of several traditional VRFs on C-IMTp. Shortcomings in study design and/or ultrasonographic protocols may account for most negative studies, which underlines the importance of careful consideration of methodological aspects in investigations using C-IMTp as the outcome.

Cholesterol transport system: An integrated cholesterol transport model involved in atherosclerosis

Atherosclerosis, the pathological basis of most cardiovascular disease (CVD), is closely associated with cholesterol accumulation in the arterial intima. Excessive cholesterol is removed by the reverse cholesterol transport (RCT) pathway, representing a major antiatherogenic mechanism. In addition to the RCT, other pathways are required for maintaining the whole-body cholesterol homeostasis. Thus, we propose a working model of integrated cholesterol transport, termed the cholesterol transport system (CTS), to describe body cholesterol metabolism. The novel model not only involves the classical view of RCT but also contains other steps, such as cholesterol absorption in the small intestine, low-density lipoprotein uptake by the liver, and transintestinal cholesterol excretion. Extensive studies have shown that dysfunctional CTS is one of the major causes for hypercholesterolemia and atherosclerosis. Currently, several drugs are available to improve the CTS efficiently. There are also several therapeutic approaches that have entered into clinical trials and shown considerable promise for decreasing the risk of CVD. In recent years, a variety of novel findings reveal the molecular mechanisms for the CTS and its role in the development of atherosclerosis, thereby providing novel insights into the understanding of whole-body cholesterol transport and metabolism. In this review, we summarize the latest advances in this area with an emphasis on the therapeutic potential of targeting the CTS in CVD patients.

Non-coding RNAs in lipid metabolism

Cardiovascular disease (CVD), the leading cause of death and morbidity in the Western world, begins with lipid accumulation in the arterial wall, which is the initial step in atherogenesis. Alterations in lipid metabolism result in increased risk of cardiometabolic disorders, and treatment of lipid disorders remains the most common strategy aimed at reducing the incidence of CVD. Work done over the past decade has identified numerous classes of non-coding RNA molecules including microRNAs (miRNAs) and long-non-coding RNAs (lncRNAs) as critical regulators of gene expression involved in lipid metabolism and CVD, mostly acting at post-transcriptional level. A number of miRNAs, including miR-33, miR-122 and miR-148a, have been demonstrated to play important role in controlling the risk of CVD through regulation of cholesterol homeostasis and lipoprotein metabolism. lncRNAs are recently emerging as important regulators of lipid and lipoprotein metabolism. However, much additional work will be required to fully understand the impact of lncRNAs on CVD and lipid metabolism, due to the high abundance of lncRNAs and the poor-genetic conservation between species. This article reviews the role of miRNAs and lncRNAs in lipid and lipoprotein metabolism and their potential implications for the treatment of CVD.

Increasing HDL-C levels with medication: current perspectives

PURPOSE OF REVIEW

To date, observational studies have repeatedly demonstrated an inverse association between HDL cholesterol (HDL-C) levels and cardiovascular outcomes. Although the efficacy of established HDL-modifying treatment strategies have been examined in multiple large-scale phase III trials, findings from these experimental studies conflict with the hypothesis that HDL-C levels are atheroprotective. In this review, we describe the trial evidence to date, and attempt to place these results in the broader context of recent hypotheses for the association between HDL-C levels and clinical outcomes.

RECENT FINDINGS

Both translational and genetic studies are in line with the hypothesis that HDL-C levels do not hold causal importance for cardiovascular risk reduction. In addition to its possible role as a biomarker for other atherogenic lipoproteins, efforts should be made to elucidate HDLs' role in lipoprotein flux, which is increasingly being linked to surrogate outcomes of importance to cardiovascular epidemiology. In the future, it will be of great importance to link this measure of HDL functionality to clinical endpoints.

SUMMARY

Although trial evidence does not support an atheroprotective role of overall HDL-C plasma levels, HDL function/lipoprotein flux holds great promise for the development of novel therapeutic approaches.

30 YEARS OF THE MINERALOCORTICOID RECEPTOR: The role of the mineralocorticoid receptor in the vasculature

Since the mineralocorticoid receptor (MR) was cloned 30 years ago, it has become clear that MR is expressed in extra-renal tissues, including the cardiovascular system, where it is expressed in all cells of the vasculature. Understanding the role of MR in the vasculature has been of particular interest as clinical trials show that MR antagonism improves cardiovascular outcomes out of proportion to changes in blood pressure. The last 30 years of research have demonstrated that MR is a functional hormone-activated transcription factor in vascular smooth muscle cells and endothelial cells. This review summarizes advances in our understanding of the role of vascular MR in regulating blood pressure and vascular function, and its contribution to vascular disease. Specifically, vascular MR contributes directly to blood pressure control and to vascular dysfunction and remodeling in response to hypertension, obesity and vascular injury. The literature is summarized with respect to the role of vascular MR in conditions including: pulmonary hypertension; cerebral vascular remodeling and stroke; vascular inflammation, atherosclerosis and myocardial infarction; acute kidney injury; and vascular pathology in the eye. Considerations regarding the impact of age and sex on the function of vascular MR are also described. Further investigation of the precise molecular mechanisms by which MR contributes to these processes will aid in the identification of novel therapeutic targets to reduce cardiovascular disease (CVD)-related morbidity and mortality.

An exploratory analysis of the competing effects of aggressive decongestion and high-dose loop diuretic therapy in the DOSE trial

BACKGROUND

Effective decongestion of heart failure patients predicts improved outcomes, but high dose loop diuretics (HDLD) used to achieve diuresis predict adverse outcomes. In the DOSE trial, randomization to a HDLD intensification strategy (HDLD-strategy) improved diuresis but not outcomes. Our objective was to determine if potential beneficial effects of more aggressive decongestion may have been offset by adverse effects of the HDLD used to achieve diuresis.

METHODS AND RESULTS

A post hoc analysis of the DOSE trial (n=308) was conducted to determine the influence of post-randomization diuretic dose and fluid output on the rate of death, rehospitalization or emergency department visitation associated with the HDLD-strategy. Net fluid output was used as a surrogate for beneficial decongestive effects and cumulative loop diuretic dose for the dose-related adverse effects of the HDLD-strategy. Randomization to the HDLD-strategy resulted in increased fluid output, even after adjusting for cumulative diuretic dose (p=0.006). Unadjusted, the HDLD-strategy did not improve outcomes (p=0.28). However, following adjustment for cumulative diuretic dose, significant benefit emerged (HR=0.64, 95% CI 0.43-0.95, p=0.028). Adjusting for net fluid balance eliminated the benefit (HR=0.95, 95% CI 0.67-1.4, p=0.79).

CONCLUSIONS

A clinically meaningful benefit from a randomized aggressive decongestion strategy became apparent after accounting for the quantity of loop diuretic administered. Adjusting for the diuresis resulting from this strategy eliminated the benefit. These hypothesis-generating observations may suggest a role for aggressive decongestion in improved outcomes.

Re-evaluation of cholesteryl ester transfer protein function in atherosclerosis based upon genetics and pharmacological manipulation

PURPOSE OF REVIEW

To re-evaluate the functions of plasma cholesteryl ester transfer protein (CETP) in atherosclerosis based upon recent findings from human genetics and pharmacological CETP manipulation.

RECENT FINDINGS

CETP is involved in the transfer of cholesteryl ester from HDL to apolipoprotein B-containing lipoproteins, a key step of reverse cholesterol transport (RCT). CETP inhibitors have been developed to raise serum HDL-cholesterol (HDL-C) levels and reduce cardiovascular events. However, outcome studies of three CETP inhibitors (torcetrapib, dalcetrapib and evacetrapib) were prematurely terminated because of increased mortality or futility despite marked increases in HDL-cholesterol and decreases in LDL-cholesterol except for dalcetrapib. Patients with CETP deficiency show remarkable changes in HDL and LDL and are sometimes accompanied by atherosclerotic cardiovascular diseases. Recent prospective epidemiological studies demonstrated atheroprotective roles of CETP. CETP inhibition induces formation of small dense LDL and possibly dysfunctional HDL and downregulates hepatic scavenger receptor class B type I (SR-BI). Therefore, CETP inhibitors may interrupt LDL receptor and SR-BI-mediated cholesterol delivery back to the liver.

SUMMARY

For future drug development, the opposite strategy, namely enhancers of RCT via CETP and SR-BI activation as well as the inducers of apolipoprotein A-I or HDL production might be a better approach rather than delaying HDL metabolism by inhibiting a main stream of RCT in vivo.

Cardiovascular Safety in Drug Development

As drug development becomes a long and demanding process, it might also become a barrier to medical progress. Drug safety concerns are responsible for many of the resources consumed in launching a new drug. Despite the money and time expended on it, a significant number of drugs are withdrawn years or decades after being in the market. Cardiovascular toxicity is one of the major reasons for those late withdrawals, meaning that many patients are exposed to unexpected serious cardiovascular risks. It seems that current methods to assess cardiovascular safety are imperfect, so new approaches to avoid the exposure to those undesirable effects are quite necessary. Endothelial dysfunction is the earliest detectable pathophysiological abnormality, which leads to the development of atherosclerosis, and it is also an independent predictor for major cardiovascular events. Endothelial toxicity might be the culprit of the cardiovascular adverse effects observed with a significant number of drugs. In this article, we suggest the regular inclusion of the best validated and less invasive endothelial function tests in the clinical phases of drug development in order to facilitate the development of drugs with safer cardiovascular profiles.

Aldosterone and type 2 diabetes mellitus

Primary hyperaldosteronism (PA) has recently been demonstrated to be strictly associated to metabolic syndrome as compared with essential hypertension (EH). Besides, the characteristics of metabolic syndrome are different in PA compared to EH, as high fasting glucose is more frequent in the former condition. The adverse effect of excess aldosterone on insulin metabolic signaling has generated increasing interest in the role of hyperaldosteronism in the pathogenesis of insulin resistance and resistant hypertension. Moreover, aldosterone receptor antagonist therapy in diabetic and cardiopathic patients improved coronary flow. The aim of this review is to present recent knowledge about the relationship between aldosterone, insulin resistance and diabetes.

Systematic review of CETP inhibitors for increasing high-density lipoprotein cholesterol: where do these agents stand in the approval process?

The role that low levels of high-density lipoprotein cholesterol (HDL-C) plays in coronary artery disease and ischemic heart disease is well established. As such, therapies targeting low HDL-C levels have been of great therapeutic interest. These therapies include nonpharmacological methods such as exercise, tobacco cessation, weight reduction, moderate alcohol intake, and increasing dietary monounsaturated fatty acids and polyunsaturated fatty acids. Additionally, pharmacological methods of increasing HDL-C have been of great interest, with 2 classes of drugs, fibric acid derivatives and nicotinic acid, and have mixed trial results when used on top of standard lipid therapy. However, a new class of medications, cholesteryl ester transfer protein inhibitors, has shown increases in HDL-C of over 100%. However, early trial results with torcetrapib showed an increase in mortality, although this was attributed to off-target toxicity. Dalcetrapib was found to be safer than torcetrapib, but data released in 2012 showed no additional benefit in patients suffering an acute coronary syndrome event. Two newer agents, anacetrapib and evacetrapib, in early-phase clinical trials have shown to be safer than torcetrapib and significantly more potent than dalcetrapib (both increase HDL-C by a greater amount and both have a significant effect on low-density lipoprotein cholesterol). It remains to be seen whether the use of cholesteryl ester transfer protein inhibitors will result in clinical benefit in large, randomized double-blind trials and whether any agents in this class will ever be approved for clinical use.

Dysfunctional High-Density Lipoprotein: An Innovative Target for Proteomics and Lipidomics

High-Density Lipoprotein-Cholesterol (HDL-C) is regarded as an important protective factor against cardiovascular disease, with abundant evidence of an inverse relationship between its serum levels and risk of cardiovascular disease, as well as various antiatherogenic, antioxidant, and anti-inflammatory properties. Nevertheless, observations of hereditary syndromes featuring scant HDL-C concentration in absence of premature atherosclerotic disease suggest HDL-C levels may not be the best predictor of cardiovascular disease. Indeed, the beneficial effects of HDL may not depend solely on their concentration, but also on their quality. Distinct subfractions of this lipoprotein appear to be constituted by specific protein-lipid conglomerates necessary for different physiologic and pathophysiologic functions. However, in a chronic inflammatory microenvironment, diverse components of the HDL proteome and lipid core suffer alterations, which propel a shift towards a dysfunctional state, where HDL-C becomes proatherogenic, prooxidant, and proinflammatory. This heterogeneity highlights the need for further specialized molecular studies in this aspect, in order to achieve a better understanding of this dysfunctional state; with an emphasis on the potential role for proteomics and lipidomics as valuable methods in the search of novel therapeutic approaches for cardiovascular disease.

Anacetrapib as lipid-modifying therapy in patients with heterozygous familial hypercholesterolaemia (REALIZE): a randomised, double-blind, placebo-controlled, phase 3 study

BACKGROUND

Present guidelines emphasise the importance of low concentrations of LDL cholesterol (LDL-C) in patients with familial hypercholesterolaemia. In most patients with the disease, however, these concentrations are not achieved with present treatments, so additional treatment is therefore warranted. Inhibition of cholesteryl ester transfer protein has been shown to reduce LDL-C concentrations in addition to regular statin treatment in patients with hypercholesterolaemia or at high risk of cardiovascular disease. We aimed to investigate the safety and efficacy of anacetrapib, a cholesteryl ester transfer protein inhibitor, in patients with heterozygous familial hypercholesterolaemia.

METHODS

In this multicentre, randomised, double-blind, placebo-controlled, phase 3 study, patients aged 18-80 years with a genotype-confirmed or clinical diagnosis of heterozygous familial hypercholesterolaemia, on optimum lipid-lowering treatment for at least 6 weeks, and with an LDL-C concentration of 2·59 mmol/L or higher without cardiovascular disease or 1·81 mmol/L or higher with cardiovascular disease from 26 lipid clinics across nine countries were eligible. We randomly allocated participants with a computer-generated allocation schedule (2:1; block size of six; no stratification) to oral anacetrapib 100 mg or placebo for 52 weeks, with a 12 week post-treatment follow-up afterwards. We masked patients, care providers, and those assessing outcomes to treatment groups throughout the study. The primary outcome was percentage change from baseline in LDL-C concentration. We did analysis using a constrained longitudinal repeated measures model. This trial is registered with ClinicalTrials.gov, number NCT01524289.

FINDINGS

Between Feb 10, 2012, and Feb 12, 2014, we randomly allocated 204 patients to anacetrapib and 102 to placebo. One patient in the anacetrapib group did not receive the drug. At week 52, anacetrapib reduced mean LDL-C concentration from 3·3 mmol/L (SD 0·8) to 2·1 mmol/L (0·8; percentage change 36·0% [95% CI -39·5 to -32·5] compared with an increase with placebo from 3·4 mmol/L (1·2) to 3·5 mmol/L (1·6; percentage change 3·7% [-1·2 to 8·6], with a difference in percentage change between anacetrapib and placebo of -39·7% (95% CI -45·7 to -33·7; p<0·0001). The number of cardiovascular events was increased in patients given anacetrapib compared with those given placebo (4 [2%] of 203 vs none [0%] of 102; p=0·1544), but the proportion with adverse events leading to discontinuation was similar (12 [6%] of 203 vs five [5%] of 102).

INTERPRETATION

In patients with heterozygous familial hypercholesterolaemia, treatment with anacetrapib for 1 year was well tolerated and resulted in substantial reductions in LDL-C concentration. Whether this change leads to a reduction of cardiovascular events will be answered in an outcome study.

FUNDING

Merck & Co, Inc.

Tolerability, pharmacokinetics and pharmacodynamics of TA-8995, a selective cholesteryl ester transfer protein (CETP) inhibitor, in healthy subjects

AIMS

Two double-blind, randomized studies were conducted to assess the tolerability, pharmacokinetics and pharmacodynamics of oral TA-8995, a new cholesteryl ester transfer protein (CETP) inhibitor, in healthy subjects.

METHODS

Study 1: Subjects received single doses of TA-8995 or placebo (fasted). Doses were 5, 10, 25, 50 (fed/fasted), 100 and 150 mg (Caucasian males, 18-55 years), 25 mg (Caucasian males, > 65 years and Caucasian females, 18-55 years), 25, 50, 100 and 150 mg (Japanese males, 18-55 years). Study 2: Caucasian males (18-55 years) received 1, 2.5, 10 or 25 mg once daily TA-8995 or placebo for 21-28 days. Blood and urine for pharmacokinetics and/or pharmacodynamics were collected. Tolerability was assessed by adverse events, vital signs, electrocardiograms and laboratory safety tests.

RESULTS

Peak TA-8995 concentrations occurred approximately 4 h post-dose. Mean half-lives ranged from 81 to 166 h, without an obvious dose relationship. Exposure increased less than proportionally to dose. TA-8995 was not excreted in urine. Following 2.5 to 25 mg once daily dosing, TA-8995 demonstrated nearly complete inhibition of CETP activity (92-99%), increased high density lipoprotein-cholesterol (HDL-C) by 96 to 140% and decreased low density liporotein-cholesterol (LDL-C) by 40% to 53%. There were dose-related increases in apolipoproteins A-1 and E, HDL2-C and HDL3-C, and decreases in apolipoprotein B and lipoprotein A. There was no evidence of significant effects of age, gender, ethnicity or food on pharmacokinetics or pharmacodynamics. All doses were well tolerated.

CONCLUSIONS

TA-8995 is a potent CETP inhibitor and warrants further investigation.

Future of cholesteryl ester transfer protein inhibitors

The cholesteryl ester transfer protein (CETP) plays an integral role in the metabolism of plasma lipoproteins. Despite two failures, CETP inhibitors are still in clinical development. We review the genetics of CETP and coronary disease, preclinical data on CETP inhibition and atherosclerosis, and the effects of CETP inhibition on cholesterol efflux and reverse cholesterol transport. We discuss the two failed CETP inhibitors, torcetrapib and dalcetrapib, and attempt to extract lessons learned. Two CETP inhibitors, anacetrapib and evacetrapib, are in phase III development, and we attempt to differentiate them from the failed drugs. Whether pharmacologic CETP inhibition will reduce the risk of cardiovascular disease is one of the most fascinating and important questions in the field of cardiovascular medicine.

Building an Integrated Early Clinical Development Platform to Improve the Path to Proof of Concept

Probability of success in phase II dominates the drug development cost calculus, with phase I/II as the critical juncture for proof of concept. Failure to address fundamental pharmacologic questions in early development is alarmingly frequent and a strong predictor of failure. Safety, manufacture, formulation, and commercialization issues are also vital. Systems biology provides a framework to analyze genomic, proteomic, and metabolomic data and construct complex network models of molecular pathophysiology. Biomarkers offer the largest learning opportunity, and combined adaptive protocol designs provide a lean but scientifically robust path to proof of concept. The traditional model of phase I study execution in a clinical pharmacology unit is evolving to a networked model of an integrated early clinical development platform. The power of this platform is enhanced with a proactive multidisciplinary approach to quality and safety, including lean 6 sigma tools and simulations.

Anacetrapib reduces progression of atherosclerosis, mainly by reducing non-HDL-cholesterol, improves lesion stability and adds to the beneficial effects of atorvastatin

BACKGROUND

The residual risk that remains after statin treatment supports the addition of other LDL-C-lowering agents and has stimulated the search for secondary treatment targets. Epidemiological studies propose HDL-C as a possible candidate. Cholesteryl ester transfer protein (CETP) transfers cholesteryl esters from atheroprotective HDL to atherogenic (V)LDL. The CETP inhibitor anacetrapib decreases (V)LDL-C by ∼15-40% and increases HDL-C by ∼40-140% in clinical trials. We evaluated the effects of a broad dose range of anacetrapib on atherosclerosis and HDL function, and examined possible additive/synergistic effects of anacetrapib on top of atorvastatin in APOE*3Leiden.CETP mice.

METHODS AND RESULTS

Mice were fed a diet without or with ascending dosages of anacetrapib (0.03; 0.3; 3; 30 mg/kg/day), atorvastatin (2.4 mg/kg/day) alone or in combination with anacetrapib (0.3 mg/kg/day) for 21 weeks. Anacetrapib dose-dependently reduced CETP activity (-59 to -100%, P < 0.001), thereby decreasing non-HDL-C (-24 to -45%, P < 0.001) and increasing HDL-C (+30 to +86%, P < 0.001). Anacetrapib dose-dependently reduced the atherosclerotic lesion area (-41 to -92%, P < 0.01) and severity, increased plaque stability index and added to the effects of atorvastatin by further decreasing lesion size (-95%, P < 0.001) and severity. Analysis of covariance showed that both anacetrapib (P < 0.05) and non-HDL-C (P < 0.001), but not HDL-C (P = 0.76), independently determined lesion size.

CONCLUSION

Anacetrapib dose-dependently reduces atherosclerosis, and adds to the anti-atherogenic effects of atorvastatin, which is mainly ascribed to a reduction in non-HDL-C. In addition, anacetrapib improves lesion stability.

Recent advances in pharmacotherapy for hypertriglyceridemia

Elevated plasma triglyceride (TG) concentrations are associated with an increased risk of atherosclerotic cardiovascular disease (CVD), hepatic steatosis and pancreatitis. Existing pharmacotherapies, such as fibrates, n-3 polyunsaturated fatty acids (PUFAs) and niacin, are partially efficacious in correcting elevated plasma TG. However, several new TG-lowering agents are in development that can regulate the transport of triglyceride-rich lipoproteins (TRLs) by modulating key enzymes, receptors or ligands involved in their metabolism. Balanced dual peroxisome proliferator-activated receptor (PPAR) α/γ agonists, inhibitors of microsomal triglyceride transfer protein (MTTP) and acyl-CoA:diacylglycerol acyltransferase-1 (DGAT-1), incretin mimetics, and apolipoprotein (apo) B-targeted antisense oligonucleotides (ASOs) can all decrease the production and secretion of TRLs; inhibitors of cholesteryl ester transfer protein (CETP) and angiopoietin-like proteins (ANGPTLs) 3 and 4, monoclonal antibodies (Mabs) against proprotein convertase subtilisin/kexin type 9 (PCSK9), apoC-III-targeted ASOs, selective peroxisome proliferator-activated receptor modulators (SPPARMs), and lipoprotein lipase (LPL) gene replacement therapy (alipogene tiparvovec) enhance the catabolism and clearance of TRLs; dual PPAR-α/δ agonists and n-3 polyunsaturated fatty acids can lower plasma TG by regulating both TRL secretion and catabolism. Varying degrees of TG reduction have been reported with the use of these therapies, and for some agents such as CETP inhibitors and PCSK9 Mabs findings have not been consistent. Whether they reduce CVD events has not been established. Trials investigating the effect of CETP inhibitors (anacetrapib and evacetrapib) and PCSK9 Mabs (AMG-145 and REGN727/SAR236553) on CVD outcomes are currently in progress, although these agents also regulate LDL metabolism and, in the case of CETP inhibitors, HDL metabolism. Further to CVD risk reduction, these new treatments might also have a potential role in the management of diabetes and non-alcoholic fatty liver disease owing to their insulin-sensitizing action (PPAR-α/γ agonists) and potential capacity to decrease hepatic TG accumulation (PPAR-α/δ agonists and DGAT-1 inhibitors), but this needs to be tested in future trials. We summarize the clinical trial findings regarding the efficacy and safety of these novel therapies for hypertriglyceridemia.

Clinical Strategies for Managing Dyslipidemias

Dyslipidemia is defined as elevated fasting blood levels of total cholesterol (TC), and its primary lipoprotein carrier—low-density lipoprotein (LDL), triglycerides (TG), or reduced high-density lipoprotein (HDL), alone, or in combination (mixed dyslipidemia). Dyslipidemia is well known to be associated with cardiovascular disease (CVD) risk. All patients with dyslipidemia should initiate therapeutic lifestyle changes to target lifestyle-related factors such as physical inactivity, dietary habits, and obesity. The combination of a proper dietary plan and regular aerobic exercise has been reported to lower TC, LDL-C, and TG by 7% to 18%, while increasing HDL-C by 2% to 18%. Numerous pharmacological therapies are available and aggressive therapy using a HMG-CoA reductase (3-hydroxy-3-methyl-glutaryl coenzyme A reductase) inhibitor (statins) should be initiated if lifestyle therapy is not enough to achieve optimal lipid levels with a primary target of lowering LDL-C levels. Aggressive treatment of dyslipidemia with maximal dosage of statin drugs have been reported to reduce LDL-C by 30% to 60%. If mixed dyslipidemia is present, a combination therapy with statin, niacin, cholestyramine, or fibrates should be initiated to reduce the risk of CVD events. These strategies have been shown to reduce CVD risk and optimize LDL-C levels in primary and secondary prevention of CVD.

An overview of the new frontiers in the treatment of atherogenic dyslipidemias

Cardiovascular diseases (CVDs) are the leading cause of morbidity/mortality worldwide. Dyslipidemia is a major risk factor for premature atherosclerosis and CVD. Lowering low-density-lipoprotein cholesterol (LDL-C) levels is well established as an intervention for the reduction of CVDs. Statins are the first-line drugs for treatment of dyslipidemia, but they do not address all CVD risk. Development of novel therapies is ongoing and includes the following: (i) reduction of LDL-C concentrations using antibodies to proprotein convertase subtilisin/kexin-9, antisense oligonucleotide inhibitors of apolipoprotein B production, microsomal transfer protein (MTP) inhibitors, and acyl-coenzyme A cholesterol acyl transferase inhibitors; (ii) reduction in levels of triglyceride-rich lipoproteins with ω-3 fatty acids, MTP inhibitors, and diacylglycerol acyl transferase-1 inhibitors; and (iii) increase of high-density-lipoprotein (HDL) cholesterol levels, HDL particle numbers, and/or HDL functionality using cholesteryl ester transfer protein inhibitors, HDL-derived agents, apolipoprotein AI mimetic peptides, and microRNAs. Large prospective outcome trials of several of these emerging therapies are under way, and thrilling progress in the field of lipid management is anticipated.

The ebbs and flows in the development of cholesterol-lowering drugs: prospects for the future

Cardiovascular disease (CVD) is the leading cause of mortality worldwide, and its prevalence is increasing worldwide. Statins are the mainstay of treatment but do not address all aspects of CVD risk. Other lipid-lowering therapies are available but are less effective than statins. New therapies to lower low-density-lipoprotein cholesterol (LDL-C) by as much as statins, to reduce triglycerides (TGs), and to modify the metabolism of high-density lipoproteins (HDLs) are in development.

Dusty punch cards and an eternal enigma: high-density lipoproteins and atherosclerosis

Epidemiological, clinical, and experimental evidence has accumulated during the last decades suggesting that high-density lipoproteins (HDLs) may protect from atherosclerosis and its clinical consequences. However, more than 55 years after the first description of the link between HDL and heart attacks, many facets of the biochemistry, function, and clinical significance of HDL remain enigmatic. This applies particularly to the completely unexpected results that became available from some recent clinical trials of nicotinic acid and of inhibitors of cholesteryl ester transfer protein (CETP). The concept that raising HDL cholesterol by pharmacological means would decrease the risk of vascular disease has therefore been challenged.

Mineralocorticoid receptors in vascular disease: connecting molecular pathways to clinical implications

The mineralocorticoid receptor (MR), a steroid-hormone-activated transcription factor, plays a substantial role in cardiovascular diseases. MR antagonists (MRAs) have long been appreciated as effective treatments for heart failure and hypertension; however, recent research suggests that additional patient populations may also benefit from MRA therapy. Experimental evidence demonstrates that in addition to its classic role in the regulating sodium handling in the kidney, functional MR is expressed in the blood vessels and contributes to hypertension, vascular inflammation and remodeling, and atherogenesis. MR activation drives pathological phenotypes in smooth muscle cells, endothelial cells, and inflammatory cells, whereas MRAs inhibit these effects. Collectively, these studies demonstrate a new role for extrarenal MR in cardiovascular disease. This review summarizes these new lines of evidence and how they contribute to the mechanisms of atherosclerosis, pulmonary and systemic hypertension, and vein graft failure, and describes new patient populations that may benefit from MRA therapy.

Single step reconstitution of multifunctional high-density lipoprotein-derived nanomaterials using microfluidics

High-density lipoprotein (HDL) is a natural nanoparticle that transports peripheral cholesterol to the liver. Reconstituted high-density lipoprotein (rHDL) exhibits antiatherothrombotic properties and is being considered as a natural treatment for cardiovascular diseases. Furthermore, HDL nanoparticle platforms have been created for targeted delivery of therapeutic and diagnostic agents. The current methods for HDL reconstitution involve lengthy procedures that are challenging to scale up. A central need in the synthesis of rHDL, and multifunctional nanomaterials in general, is to establish large-scale production of reproducible and homogeneous batches in a simple and efficient fashion. Here, we present a large-scale microfluidics-based manufacturing method for single-step synthesis of HDL-mimicking nanomaterials (μHDL). μHDL is shown to have the same properties (e.g., size, morphology, bioactivity) as conventionally reconstituted HDL and native HDL. In addition, we were able to incorporate simvastatin (a hydrophobic drug) into μHDL, as well as gold, iron oxide, quantum dot nanocrystals or fluorophores to enable its detection by computed tomography (CT), magnetic resonance imaging (MRI), or fluorescence microscopy, respectively. Our approach may contribute to effective development and optimization of lipoprotein-based nanomaterials for medical imaging and drug delivery.

Plaque regression and plaque stabilisation in cardiovascular diseases

Atherosclerosis is characterized by formation of plaques on the inner walls of arteries that threatens to become the leading cause of death worldwide via its sequelae of myocardial infarction and stroke. Endothelial dysfunction leads to cholesterol uptake and accumulation of inflammatory markers within the plaque. The stability of a plaque eventually depends on the balance between vascular smooth muscle cells that stabilize it and the inflammatory cells like macrophages and T lymphocytes that make it prone to rupture. The current approach to manage atherosclerosis focuses on the treatment of a ruptured plaque and efforts have been made to reduce the risk of plaque rupture by identifying vulnerable plaques and treating them before they precipitate into clinical events. New diagnostic approaches such as IVUS and CIMT ultrasound are now being preferred over traditional coronary angiography because of their better accuracy in measuring plaque volume rather than the level of stenosis caused. The present review highlights the literature available on two prevalent approaches to manage a vulnerable plaque, namely, plaque stabilization and plaque regression, and their validation through various treatment modalities in recent plaque management studies. Plaque stabilization focuses on stabilizing the content of plaque and strengthening the overlying endothelium, while plaque regression focuses on the overall reduction in plaque volume and to reverse the arterial endothelium to its normal functional state. Although earlier studies contemplated the practicality of plaque regression and focused greatly on stabilization of a vulnerable plaque, our review indicated that, aided by the use of superior diagnostics tools, more intensive lipid modifying therapies have resulted in actual plaque regression.

Cholesteryl ester transfer protein inhibitors in the treatment of dyslipidemia: a systematic review and meta-analysis

Cholesteryl ester transfer protein (CETP) inhibitors are gaining substantial research interest for raising high density lipoprotein cholesterol levels. The aim of the research was to estimate the efficacy and safety of cholesteryl ester transfer protein inhibitors as novel lipid modifying drugs. Systematic searches of English literature for randomized controlled trials (RCT) were collected from MEDLINE, EBASE, CENTRAL and references listed in eligible studies. Two independent authors assessed the search results and only included the double-blind RCTs by using cholesteryl ester transfer protein inhibitors as exclusively or co-administrated with statin therapy irrespective of gender in enrolled adult subjects. Two independent authors extracted the data by using predefined data fields. Of 503 studies identified, 14 studies met the inclusion criteria, and 12 studies were included into the final meta-analysis. Our meta-analysis revealed that CETP inhibitors increased the HDL-c levels (n = 2826, p<0.00001, mean difference (MD) = 20.47, 95% CI [19.80 to 21.15]) and total cholesterol (n = 3423, p = 0.0002, MD = 3.57, 95%CI [1.69 to 5.44] to some extent combined with a reduction in triglyceride (n = 3739, p<0.00001, MD = -10.47, 95% CI [-11.91 to -9.03]) and LDL-c (n = 3159, p<0.00001, MD = -17.12, 95% CI [-18.87 to -15.36]) irrespective of mono-therapy or co-administration with statins. Subgroup analysis suggested that the lipid modifying effects varied according to the four currently available CETP inhibitors. CETP inhibitor therapy did not increase the adverse events when compared with control. However, we observed a slight increase in blood pressure (SBP, n = 2384, p<0.00001, MD = 2.73, 95% CI [2.14 to 3.31], DBP, n = 2384, p<0.00001, MD = 1.16, 95% CI [0.73 to 1.60]) after CETP inhibitor treatment, which were mainly ascribed to the torcetrapib treatment subgroup. CETP inhibitors therapy is associated with significant increase in HDL-c and decrease in triglyceride and LDL-c with satisfactory safety and tolerability in patients with dyslipidemia. However, the side-effect on blood pressure deserves more consideration in future studies.

Proteomic diversity of high density lipoproteins: our emerging understanding of its importance in lipid transport and beyond

Recent applications of mass spectrometry technology have dramatically increased our understanding of the proteomic diversity of high density lipoproteins (HDL). Depending on the method of HDL isolation, upwards of 85 proteins have been identified, and the list continues to grow. In addition to proteins consistent with traditionally accepted roles in lipid transport, HDL carries surprising constituents, such as members of the complement pathway, protease inhibitors involved in hemostasis, acute-phase response proteins, immune function mediators, and even metal-binding proteins. This compositional diversity fits well with hundreds of studies demonstrating a wide functional pleiotrophy, including roles in lipid transport, oxidation, inflammation, hemostasis, and immunity. This review summarizes the progression of our understanding of HDL proteomic complexity and points out key experimental observations that reinforce the functional diversity of HDL. The possibility of specific HDL subspecies with distinct functions, the evidence supporting this concept, and some of the best examples of experimentally defined HDL subspecies are also discussed. Finally, key challenges facing the field are highlighted, particularly the need to identify and define the function of HDL subspecies to better inform attempts to pharmacologically manipulate HDL for the benefit of cardiovascular disease and possibly other maladies.

Carotid intima-media thickness testing as an asymptomatic cardiovascular disease identifier and method for making therapeutic decisions

Cardiovascular disease (CVD) is the leading cause of death and disability in the United States. Although current therapies can reduce the risk for CVD, they are only given to patients who are considered to be at risk, and are therefore only beneficial if a patient's risk is accurately predicted before he or she sustains a cardiovascular (CV) event. Unfortunately, even relatively accurate risk factor analyses, such as the Reynolds Risk Score algorithm, fail to identify some patients who will sustain a CV event within 10 years. In contrast, the presence of an atheroma is an absolute predictor for the potential of an atherothrombotic event to occur, and it is therefore reasonable to anchor clinical decisions based on this knowledge. Carotid intima-media thickness (CIMT) testing via B-mode ultrasound is a safe, simple, and inexpensive method for evaluating CV risk by measuring the combined thickness of the intimal and medial layers of the arterial wall. Use of CIMT testing can also detect marked thickening of the arterial wall, possibly indicating plaques or atheromas that are associated with accelerated atherosclerotic disease and increased risk for coronary artery disease, myocardial infarction, and stroke. These characteristics make CIMT a practical supplemental method that physicians can use when making decisions. Moreover, the ability of CIMT testing to identify and quantify atherosclerotic disease has led to the adoption of CIMT as a surrogate endpoint in clinical trials, allowing the efficacy of new drugs to be assessed much more rapidly than would be possible by focusing solely on CV event or mortality rates. To date, several trials have provided evidence to indicate that some CVD therapies slow, stop, or reverse the progression of CIMT. Although many of these studies show that changes in CIMT predict future CV events, the value of CIMT testing in CVD risk assessment is still vigorously debated. In this article, we clarify the utility of CIMT testing for risk classification and reexamine its usefulness as a method for assessing therapeutic efficacy.

Is the future of statins aligned with new novel lipid modulation therapies?

Dyslipidemia is an established risk factor for the development of atherosclerotic cardiovascular disease. Statin therapy has been proven in a number of clinical trials to lower the risk of acute cardiovascular events and is the mainstay of cholesterol treatment. Despite current optimal treatment for dyslipidemia, many patients fail to reach adequate cholesterol treatment goals and remain at a significantly increased risk of cardiovascular events. Given this residual risk, there is a critical need for additional lipid therapies that could augment the ability of statins to lower the burden of atherogenic lipoproteins and, in some cases, raise levels of high-density lipoproteins. A number of novel lipid-altering therapies have been developed and are currently in clinical trials. In this review, we discuss these promising therapies, which include PCSK9 inhibitors, apolipoprotein B antisense oligonucleotides, microsomal transfer protein inhibitors, thyroid mimetics, and cholesteryl ester transfer protein inhibitors. Although statin therapy is the current recommended primary treatment for dyslipidemia, emerging novel agents may become adjuvant therapies in the treatment of atherosclerotic heart disease.

Novel pharmacotherapies of familial hyperlipidemia

Familial hyperlipidemia is an inherited metabolic disorder characterized by elevated lipid and/or lipoprotein levels in the blood. Despite improvements in lipid-lowering therapy during the last decades, it still remains a substantial contributor to the incidence of cardiovascular disease since patients on current conventional therapies do not achieve their target LDL-cholesterol levels. With a view to lower LDL-cholesterol levels, a number of new therapeutic strategies have been developed over recent years. In this review, we provide an overview of these treatment options that are currently in clinical development and may offer alternative or adjunctive therapies for this high-risk population.

HDL--is it too big to fail?

The HDL hypothesis has suffered damage in the past few years. Clinical trials have shown that raising HDL cholesterol levels does not improve cardiovascular disease (CVD) outcomes. In addition, Mendelian randomization studies have shown that DNA variants that alter HDL cholesterol levels in populations are unrelated to incident CVD events. Balancing this deluge of negative data are substantial basic science data supporting the concept that raising HDL cholesterol levels reduces CVD risk. Also, functionally relevant HDL subfractions might be more important determinants of risk than overall HDL cholesterol levels. But, while wobbly, the HDL hypothesis is still standing, seemingly too big to fail owing to past intellectual, economic and psychological investments in the idea.

Aldosterone increases early atherosclerosis and promotes plaque inflammation through a placental growth factor-dependent mechanism

Background

Aldosterone levels correlate with the incidence of myocardial infarction and mortality in cardiovascular patients. Aldosterone promotes atherosclerosis in animal models, but the mechanisms are poorly understood.

Methods and Results

Aldosterone was infused to achieve pathologically relevant levels that did not increase blood pressure in the atherosclerosis‐prone apolipoprotein E–knockout mouse (ApoE−/−). Aldosterone increased atherosclerosis in the aortic root 1.8±0.1‐fold after 4 weeks and in the aortic arch 3.7±0.2‐fold after 8 weeks, without significantly affecting plaque size in the abdominal aorta or traditional cardiac risk factors. Aldosterone treatment increased lipid content of plaques (2.1±0.2‐fold) and inflammatory cell content (2.2±0.3‐fold), induced early T‐cell (2.9±0.3‐fold) and monocyte (2.3±0.3‐fold) infiltration into atherosclerosis‐prone vascular regions, and enhanced systemic inflammation with increased spleen weight (1.52±0.06‐fold) and the circulating cytokine RANTES (regulated and normal T cell secreted; 1.6±0.1‐fold). To explore the mechanism, 7 genes were examined for aldosterone regulation in the ApoE−/− aorta. Further studies focused on the proinflammatory placental growth factor (PlGF), which was released from aldosterone‐treated ApoE−/− vessels. Activation of the mineralocorticoid receptor by aldosterone in human coronary artery smooth muscle cells (SMCs) caused the release of factors that promote monocyte chemotaxis, which was inhibited by blocking monocyte PlGF receptors. Furthermore, PlGF‐deficient ApoE−/− mice were resistant to early aldosterone‐induced increases in plaque burden and inflammation.

Conclusions

Aldosterone increases early atherosclerosis in regions of turbulent blood flow and promotes an inflammatory plaque phenotype that is associated with rupture in humans. The mechanism may involve SMC release of soluble factors that recruit activated leukocytes to the vessel wall via PlGF signaling. These findings identify a novel mechanism and potential treatment target for aldosterone‐induced ischemia in humans.

Mineralocorticoid receptor-mediated vascular insulin resistance: an early contributor to diabetes-related vascular disease?

Two-thirds of adults in the U.S. are overweight or obese, and another 26 million have type 2 diabetes (T2D). Patients with diabetes and/or the metabolic syndrome have a significantly increased risk of heart attack and stroke compared with people with normal insulin sensitivity. Decreased insulin sensitivity in cardiovascular tissues as well as in traditional targets of insulin metabolic signaling, such as skeletal muscle, is an underlying abnormality in obesity, hypertension, and T2D. In the vasculature, insulin signaling plays a critical role in normal vascular function via endothelial cell nitric oxide production and modulation of Ca(2+) handling and sensitivity in vascular smooth muscle cells. Available evidence suggests that impaired vascular insulin sensitivity may be an early, perhaps principal, defect of vascular function and contributor to the pathogenesis of vascular disease in persons with obesity, hypertension, and T2D. In the overweight and obese individual, as well as in persons with hypertension, systemic and vascular insulin resistance often occur in concert with elevations in plasma aldosterone. Indeed, basic and clinical studies have demonstrated that elevated plasma aldosterone levels predict the development of insulin resistance and that aldosterone directly interferes with insulin signaling in vascular tissues. Furthermore, elevated plasma aldosterone levels are associated with increased heart attack and stroke risk. Conversely, renin-angiotensin-aldosterone system and mineralocorticoid receptor (MR) antagonism reduces cardiovascular risk in these patient populations. Recent and accumulating evidence in this area has implicated excessive Ser phosphorylation and proteosomal degradation of the docking protein, insulin receptor substrate, and enhanced signaling through hybrid insulin/IGF-1 receptor as important mechanisms underlying aldosterone-mediated interruption of downstream vascular insulin signaling. Prevention or restoration of these changes via blockade of aldosterone action in the vascular wall with MR antagonists (i.e., spironolactone, eplerenone) may therefore account for the clinical benefit of these compounds in obese and diabetic patients with cardiovascular disease. This review will highlight recent evidence supporting the hypothesis that aldosterone and MR signaling represent an ideal candidate pathway linking early promoters of diabetes, especially overnutrition and obesity, to vascular insulin resistance, dysfunction, and disease.

Does it make sense to combine statins with other lipid-altering agents following AIM-HIGH, SHARP and ACCORD?

Hypercholesterolemia is one of the main risk factors for the development of atherosclerotic diseases. Multiple clinical trials of lipid-lowering agents have demonstrated that lowering cholesterol effectively reduces the risk of cardiovascular events and death. Currently, treatment with 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors ("statins") is the most commonly used approach, given their superior efficacy relative to other cholesterol lowering agents. However, not all patients on statin monotherapy achieve target cholesterol levels, and even when cholesterol lowering is successful, significant residual cardiovascular risk remains. There is increasing interest in developing combination cholesterol-modifying therapies that may augment the treatment effect and minimize the side effects of statins. Although there is currently no evidence that any of the potential therapy combinations can improve clinical outcome compared to statin monotherapy alone, results of several large ongoing trials will help to clarify this important field.

Safety of CETP inhibition

PURPOSE OF REVIEW

Cholesteryl ester transfer protein (CETP)-inhibiting drugs effectively raise HDL cholesterol. In 2007, the CETP inhibitor torcetrapib unexpectedly showed increased fatality and cardiovascular events, possibly related to increased blood pressure and aldosterone levels caused by torcetrapib. Since then, novel CETP inhibiting drugs have been investigated. This review will discuss the safety of the CETP-inhibiting drugs.

RECENT FINDINGS

The novel CETP inhibitors dalcetrapib, evacetrapib and anacetrapib did not show harmful effects on blood pressure or aldosterone levels. Ultrasound brachial artery flow-mediated vasodilation, carotid MRI and (18)F-fluordeoxyglucose PET imaging studies, showed that dalcetrapib therapy had neither harmful nor beneficial effects on endothelial function, atherosclerosis progression, or vessel wall inflammation. Recently, the clinical endpoint study investigating dalcetrapib was announced to be terminated early, after the second interim analysis showed that dalcetrapib lacked clinically meaningful efficacy.

SUMMARY

Dalcetrapib, evacetrapib and anacetrapib did not show the harmful effects on aldosterone and blood pressure that were exhibited by torcetrapib, indicating that CETP inhibition is well tolerated. So far CETP inhibition did not show beneficial effects on clinical outcome. The phase III study with anacetrapib will give final answers on whether CETP inhibition can reduce cardiovascular events.

New horizons for cholesterol ester transfer protein inhibitors

High-density lipoprotein (HDL) cholesterol levels bear an inverse relationship to cardiovascular risk. To date, however, no intervention specifically targeting HDL has been demonstrated to reduce cardiovascular risk. Cholesterol ester transfer protein (CETP) mediates transfer of cholesterol ester from HDL to apolipoprotein B-containing particles. Most, but not all observational cohort studies indicate that genetic polymorphisms of CETP associated with reduced activity and higher HDL cholesterol levels are also associated with reduced cardiovascular risk. Some, but not all studies indicate that CETP inhibition in rabbits retards atherosclerosis, whereas transgenic CETP expression in mice promotes atherosclerosis. Torcetrapib, the first CETP inhibitor to reach phase III clinical development, was abandoned due to excess mortality associated with increases in aldosterone and blood pressure. Two other CETP inhibitors have entered phase III clinical development. Anacetrapib is a potent inhibitor of CETP that produces very large increases in HDL cholesterol and large reductions in low-density lipoprotein (LDL) cholesterol, beyond those achieved with statins. Dalcetrapib is a less potent CETP inhibitor that produces smaller increases in HDL cholesterol with minimal effect on LDL cholesterol. Both agents appear to allow efflux of cholesterol from macrophages to HDL in vitro, and neither agent affects blood pressure or aldosterone in vivo. Two large cardiovascular outcomes trials, one with anacetrapib and one with dalcetrapib, should provide a conclusive test of the hypothesis that inhibition of CETP decreases cardiovascular risk.

Residual cardiovascular risk despite optimal LDL cholesterol reduction with statins: the evidence, etiology, and therapeutic challenges

This review captures the existence, cause, and treatment challenges of residual cardiovascular risk (CVR) after aggressive low-density lipoprotein cholesterol (LDL-C) reduction. Scientific evidence implicates low high-density lipoprotein cholesterol (HDL-C) and high triglycerides (TG) in the CVR observed after LDL-C lowering. However, the Action to Control Cardiovascular Risk in Diabetes (ACCORD) lipid trial with fenofibrate, the Investigation of Lipid Level Management to Understand its Impact in Atherosclerotic Events (ILLUMINATE) study with torcetrapib, and the recently terminated Atherothrombosis Intervention in Metabolic Syndrome with Low HDL Cholesterol/High Triglyceride and Impact on Global Health Outcomes (AIM-HIGH) study with niacin, do not clearly attribute risk reduction value to HDL-C/TG modulation. The optimum approach to long-term lipid-modifying therapies for CVR reduction remains uncertain. Consequently, absolute risk modulation via lifestyle changes remains the centerpiece of a strategy addressing the physiologic drivers of CVR associated with HDL-C/TG, especially in the context of diabetes/metabolic syndrome.

Cholesteryl ester transfer-protein modulator and inhibitors and their potential for the treatment of cardiovascular diseases

Elevated low-density lipoprotein (LDL) cholesterol and lowered high-density lipoprotein (HDL) cholesterol are important risk factors for cardiovascular disease. Accordingly, raising HDL cholesterol induced by cholesteryl ester transfer protein (CETP) inhibition is an attractive approach for reducing the residual risk of cardiovascular events that persist in many patients receiving low-density LDL cholesterol-lowering therapy with statins. The development of torcetrapib, a CETP inhibitor, was terminated due to its adverse cardiovascular effects. These adverse effects did not influence the mechanism of CETP inhibition, but affected the molecule itself. Therefore a CETP modulator, dalcetrapib, and a CETP inhibitor, anacetrapib, are in Phase III of clinical trials to evaluate their effects on cardiovascular outcomes. In the dal-VESSEL (dalcetrapib Phase IIb endothelial function study) and the dal-PLAQUE (safety and efficacy of dalcetrapib on atherosclerotic disease using novel non-invasive multimodality imaging) clinical studies, dalcetrapib reduced CETP activity by 50% and increased HDL cholesterol levels by 31% without changing LDL cholesterol levels. Moreover, dalcetrapib was associated with a reduction in carotid vessel-wall inflammation at 6 months, as well as a reduced vessel-wall area at 24 months compared with the placebo. In the DEFINE (determining the efficacy and tolerability of CETP inhibition with anacetrapib) clinical study, anacetrapib increased HDL cholesterol levels by 138% and decreased LDL cholesterol levels by 36%. In contrast with torcetrapib, anacetrapib had no adverse cardiovascular effects. The potential of dalcetrapib and anacetrapib in the treatment of cardiovascular diseases will be revealed by two large-scale clinical trials, the dal-OUTCOMES (efficacy and safety of dalcetrapib in patients with recent acute coronary syndrome) study and the REVEAL (randomized evaluation of the effects of anacetrapib through lipid modification, a large-scale, randomized placebo-controlled trial of the clinical effects of anacetrapib among people with established vascular disease) study. The dal-OUTCOMES study is testing whether dalcetrapib can reduce cardiovascular events and the REVEAL study is testing whether anacetrapib can reduce cardiovascular events. These reports are expected to be released by 2013 and 2017, respectively.