Dalcetrapib: a review of Phase II data

Importance of the field: While statins reduce the risk of cardiovascular disease by up to 50%, many patients remain at increased risk due to low levels of high-density lipoprotein cholesterol (HDL-C). Whether pharmacologically raising HDL-C per se with drug therapy will reduce cardiovascular events remains to be determined.

Areas covered in this review: Review of HDL-C-raising compounds, with a focus on cholesteryl ester transfer protein (CETP) inhibitors.

What the reader will gain: An overview of the CETP inhibitor dalcetrapib. Despite 70% increases in HDL-C, development of the CETP inhibitor torcetrapib was halted due to excess mortality, attributed largely to activation of the renin–angiotensin–aldosterone system resulting in hypertensive effects. Development of the CETP inhibitors dalcetrapib and anacetrapib is ongoing. Dalcetrapib has a unique chemical structure and induces a conformational change in CETP rather than forming a non-productive CETP/HDL-C complex as do the other CETP inhibitors. Although dalcetrapib is the least potent CETP inhibitor of the three in terms of CETP activity, the 900-mg dose did not increase blood pressure or raise aldosterone levels over 48 weeks of follow-up. The 600-mg dose of dalcetrapib is moving forward and raises HDL-C by 25 – 30% when used alone or in combination with a statin, with little effect on low-density lipoprotein cholesterol levels.

Take home message: Before regulatory approval is granted, results from the ongoing dal-OUTCOMES trial evaluating the effects of dalcetrapib 600 mg daily over standard statin therapy on mortality and morbidity in > 15,000 high-risk CHD patients will be needed. The Dalcetrapib HDL Evaluation, Atherosclerosis and Reverse Cholesterol Transport (dal-HEART) program also includes three surrogate end point trials, dal-VESSEL, dal-PLAQUE and dal-PLAQUE 2, which will provide further information as to the contribution of CETP to cardiovascular disease.     

On- and off-target pharmacology of torcetrapib: current understanding and implications for the structure activity relationships (SAR), discovery and development of cholesteryl ester-transfer protein (CETP) inhibitors

Lowering of serum low-density lipoprotein cholesterol (LDL-C) levels remains the primary aim of lipid management. Much progress has been made in reducing rates of cardiovascular disease morbidity and mortality, largely through increased awareness of lipid-lowering therapies and particularly through the use of high-efficacy LDL-C-lowering HMG-CoA reductase inhibitors (statins). While statins have been effective in reducing cardiovascular disease risk, many patients do not adequately achieve guideline-recommended LDL-C goals and may benefit from additional cholesterol management therapies. Low serum levels of high-density lipoprotein cholesterol (HDL-C) are considered another important determinant of cardiovascular disease risk, and increased serum HDL-C levels have been shown to be associated with reductions in the incidence of cardiovascular disease. One approach toward raising serum HDL-C levels is the inhibition of cholesteryl ester-transfer protein (CETP), a plasma protein that promotes the transfer of cholesteryl ester from HDL particles and other lipoprotein fractions to pro-atherogenic apolipoprotein B-containing lipoproteins. The inhibition of this protein raises HDL-C levels and also reduces LDL-C levels. The concept of raising HDL-C levels through pharmacological intervention of this target was validated in preclinical and clinical studies with torcetrapib, the first CETP inhibitor to be assessed in late-stage clinical trials. The large clinical outcomes trial, ILLUMINATE, was prematurely terminated due to other unexpected pharmacological effects of torcetrapib that led to an increased risk of cardiovascular events and deaths. Thus, the ultimate effect of CETP inhibition on cardiovascular disease outcomes remains to be determined. Other CETP inhibitors currently in development do not have the adverse effects of increased blood pressure and circulating levels of aldosterone shown to be structurally related to torcetrapib. Preclinical and pharmacology studies have shown that these CETP inhibitors are distinct compared with torcetrapib and lack the features related to its off-target pharmacology. These findings indicate that the off-target activities of torcetrapib are not necessarily class effects of CETP inhibitors. Recent clinical trials have shown that dalcetrapib, anacetrapib and evacetrapib, the most advanced of these compounds in development, effectively raise HDL-C levels and lower LDL-C in the absence of off-target activities. The results of these trials are encouraging within the limits of study size and duration and provide a rationale for conducting further studies, including large clinical outcomes trials to assess whether CETP inhibition can lead to cardioprotective effects. This review summarizes the data supporting the development of CETP inhibitors as HDL-C-raising therapy, including structure-activity relationships and preclinical and clinical pharmacology studies of known CETP inhibitors.     

Investigational CETP antagonists for hyperlipidemia and atherosclerosis prevention

Introduction: Reverse cholesterol transport (RCT) is a function of high-density lipoproteins (HDL) in humans and higher species. It is enabled by the cholesteryl ester transfer protein (CETP), a high molecular weight protein exchanging cholesteryl esters in HDL for triglycerides in very low-density lipoproteins (VLDL). Inhibition of CETP may provide a useful strategy to raise HDL, the protective lipoprotein fraction in plasma.

Areas covered: Evaluation based on clinical and experimental findings of the three drugs developed or in advanced development for CETP inhibition.

Expert opinion: Inhibition of CETP, both inherited and drug induced, at times leads to dramatic elevations of HDL-cholesterol (HDL-C) levels. Epidemiological data presently available do not, however, provide convincing evidence that reduced CETP levels or activity due to genetic factors and associated with HDL-C elevations, reduce cardiovascular risk. Indeed, the opposite may be true in some instances. All the three CETP inhibitors were the object of experimental and clinical evaluation. Large clinical trials with torcetrapib led to very negative findings, that is, raised cardiovascular morbidity and mortality in addition to raised risk of cancer and sepsis. Off-target effects of the drug, such as aldosterone retention and raised blood pressure, were believed to provide an explanation for these negative findings. The two newer agents, dalcetrapib and anacetrapib, do not exert off-target effects. The two drugs differ because anacetrapib has a more dramatic effect on HDL cholesterolemia (+139%) versus more moderate effects of dalcetrapib (+20–30%). Anacetrapib, however, may impair formation of pre-β HDL, that is, the primary particles in the process of cholesterol removal. The initial large trial with anacetrapib (DEFINE study) in coronary patients on statin treatment, appeared to confirm a remarkable HDL raising property, together with some reduction in vascular end points, in particular coronary procedures. The issue of other potentially harmful effects of CETP inhibition (sepsis and others) has yet to be clarified. Large clinical end-point trials, however, will be necessary to provide convincing evidence that, in addition to raising HDL-C, CETP inhibitors provide a valid additional treatment, for example, to statins in patients with coronary heart disease (CHD) or at high risk of CHD.     

Anacetrapib for the treatment of dyslipidaemia: the last bastion of the cholesteryl ester transfer protein inhibitors?

Introduction: Inhibition of cholesteryl ester transfer protein (CETP) has emerged as a potential way to decrease cardiovascular risk by raising high density lipoprotein (HDL) cholesterol and lowering low density lipoprotein (LDL) cholesterol concentrations. However, high profile withdrawals of several CETP inhibitors have cast doubt over this hypothesis. Despite this concern, anacetrapib appears to be safe, well-tolerated and delivers a substantial increases in HDL cholesterol and reductions in LDL cholesterol as monotherapy and when combined with a statin.

Areas covered: We discuss the role of CETP and HDL cholesterol as therapeutic targets, describe the pharmacokinetics and pharmacodynamics of anacetrapib, as well as report on the recent clinical trials.

Expert opinion: The focus of CETP inhibition has shifted from HDL cholesterol-raising to LDL cholesterol-lowering. Although anacetrapib appears to be safe and is effective in altering lipid-related biochemical parameters of interest, its effect on cardiovascular outcomes remains unknown. Extrapolation of LDL cholesterol lowering to improved cardiovascular outcomes is not possible, because LDL and HDL functionality in the setting of anacetrapib treatment is unclear. The results of the phase III REVEAL randomised controlled trial will be critical for anacetrapib to establish a place in clinical care.     

LDL‐C/HDL‐C ratio in subjects with cardiovascular disease and a low HDL‐C: results of the RADAR (Rosuvastatin and Atorvastatin in different Dosages And Reverse cholesterol transport) study

ABSTRACT

Background: The ratio of low-density lipoprotein cholesterol and high-density lipoprotein cholesterol (LDL‐C/HDL‐C) is a reliable predictor of cardiovascular risk. Low HDL‐C levels in patients with coronary artery disease are associated with a high risk for cardiovascular events.

Objectives: This study compared the effects of rosuvastatin and atorvastatin on the LDL‐C/HDL‐C ratio in patients with cardiovascular disease and low HDL‐C.

Methods: Patients aged 40–80 years with established cardiovascular disease and HDL‐C < 1.0?mmol/L (< 40?mg/dL) entered a 6‐week dietary run-in period, before randomisation to open-label treatment with rosuvastatin 10?mg (n = 230) or atorvastatin 20?mg (n = 231) for 6 weeks. Doses were increased after 6 weeks to rosuvastatin 20?mg or atorvastatin 40?mg, and after 12 weeks to rosuvastatin 40?mg or atorvastatin 80?mg. Serum lipid parameters were measured at baseline and 6, 12 and 18 weeks.

Results: After 6 weeks of treatment, mean percentage change from baseline in LDL‐C/HDL‐C ratio was –47.0% in the rosuvastatin group and –41.9% in the atorvastatin group (?p < 0.05 for between-group comparison). After 12 and 18 weeks of treatment, change from baseline was –53.0% and –57.3%, respectively, for rosuvastatin, compared with –47.9% and –49.6%, respectively, for atorvastatin (?p < 0.01 and p < 0.001, respectively, for between-group comparison). Rosuvastatin also reduced LDL‐C, total cholesterol and non-HDL‐C significantly more than atorvastatin at all three time points, and significantly improved total cholesterol/HDL‐C and apolipoprotein B/A‐I ratios.

Conclusions: Rosuvastatin 10, 20 and 40?mg is significantly more effective than atorvastatin 20, 40 and 80?mg, respectively, in improving the LDL‐C/HDL‐C ratio in patients with cardiovascular disease and low HDL‐C. Further studies are required to clarify the benefits of rosuvastatin for reduction of cardiovascular risk.     

胆固醇酯转移蛋白抑制剂Anacetrapib

高密度脂蛋白-胆固醇(HDL-C)低于正常水平是诱发心血管疾病的因素之一,升高较低水平的HDL-C能够降低患心血管疾病的风险.一些代谢疾病,如胰岛素耐受、高三酰甘油血症都会增强胆固醇酯转移蛋白的活性,高活性的胆固醇酯转移蛋白可诱发动脉粥样硬化和增加患心血管疾病的风险.因此,抑制胆固醇酯转移蛋白是治疗动脉粥样硬化症的新靶...     

One third of the variability in HDL‐cholesterol level in a large dyslipidaemic population is predicted by age,sex and triglyceridaemia:The Paris La Pitié Study

ABSTRACT

Objective: The objective of this study was to identify key determinants of high-density lipoprotein-cholesterol (HDL-C) level, including subclinical inflammation and insulin resistance, and to determine the prevalence of a low HDL-C phenotype in dyslipidaemic patients at high cardiovascular risk.

Methods: In a cross-sectional study, we assessed the prevalence of low HDL‐C phenotypes in 14?667 dyslipidaemic patients attending our specialised lipid clinic and evaluated the potential relationships between HDL‐C level and 16 clinical and biological parameters.

Results: In univariate analysis, women exhibited higher plasma concentrations of HDL‐C as compared with men. Levels of triglycerides, fasting blood glucose, uric acid, waist circumference, body mass index, high sensitivity C-reactive protein (hs‐CRP), insulin resistance (as HOMA‐IR index) and smoking were all negatively correlated with HDL‐C, whereas age was positively correlated with HDL‐C levels. Moderate drinkers (10–30?g/day) displayed higher HDL‐C concentrations as compared with abstinent subjects; in contrast, consumption of more than 30?g alcohol/day was associated with a further non-significant elevation of HDL‐C levels as compared to moderate drinkers. Multivariate analysis identified eight independent correlates of HDL‐C. Age, sex and TG accounted for 37% of variability in HDL‐C; modifiable factors including waist circumference, alcohol consumption and smoking, in addition to HOMA‐IR and hs‐CRP, accounted for an additional 5% of the variability in HDL‐C. Using a cut-off of 40?mg/dL (1.03?mmol/L) for men and 50?mg/dL (1.29?mmol/L) for women, 33% and 28% of men and women displayed low levels of HDL‐C.

Conclusion: Eight independent determinants of HDL‐C account for 41% of variability in HDL‐C in our dyslipidaemic population. Three of them, i.e. age, sex and degree of triglyceridaemia accounted for more than one third of such variability. The high prevalence of low HDL‐C phenotypes in dyslipidaemic patients at elevated cardiovascular risk emphasises the need for both lifestyle and pharmacological strategies of intervention to raise HDL‐C.     

Targeting cAMP in chronic lymphocytic leukemia: a pathway-dependent approach for the treatment of leukemia and lymphoma

Background: CETP has an established role in the transport of cholesterol from the peripheral tissues to the liver for elimination. The fact that CETP was recognized as a target for raising high-density lipoprotein cholesterol (HDL-C) levels has led to research on CETP inhibitors to protect against atherosclerosis. Objective: To review the role of CETP as a pivotal target for atherosclerosis and cardiovascular diseases and the effect of its overexpression or inhibition on lipid metabolism. Methods: A review of literature on the role of CETP in cholesterol metabolism and on recent developments on CETP inhibitors. Results/conclusions: Animal and human studies have provided evidence supporting both the pro- and antiatherogenic roles of CETP. Clinical trials with CETP inhibitors remain under serious consideration. Further studies are necessary for understanding of the role of CETP in lipid metabolism and the development of novel therapies involving a combination of strategies for treatment of atherosclerosis and cardiovascular disease.     

Emerging drug for diarrhea predominant irritable bowel syndrome

Introduction: Hypercholesterolemia is a major risk factor for cardiovascular disease (CVD). Low-density lipoprotein cholesterol (LDL-C) reduction has been demonstrated to decrease CVD-related morbidity and mortality. However, several patients do not reach LDL-C target levels with the currently available lipid lowering agents, particularly statins. Lipid and non-lipid parameters other than LDL-C may account for the residual CVD risk after adequate LDL-C lowering with statins.

Areas covered: This review focuses on the efficacy and safety of emerging drugs aiming at high-density lipoprotein cholesterol (HDL-C) elevation (i.e., recombinant or plasma-derived wild-type apolipoprotein (apo) A-I, apo A-I mimetic peptides, reconstituted mutant HDL, partially delipidated HDL and cholesterol ester transfer protein inhibitors), microsomal triglyceride transfer protein inhibitors and antisense oligonucleotides.

Expert opinion: Several lipid modifying agents in development may potently reduce the residual CVD risk. Ongoing and future studies with clinical outcomes will clarify their efficacy in clinical practice.     

Pharmacological management of diabetic dyslipidemia

Introduction: Diabetes mellitus is associated with increased cardiovascular disease (CVD) risk.

Areas covered: Main goal of hypolipidemic treatment in diabetic patients is low-density lipoprotein cholesterol (LDL-C) lowering with the use of statins. Addition of ezetimibe is useful in diabetic patients who cannot achieve their LDL-C target. However, many diabetic patients have increased residual CVD risk, which is mainly attributed to high triglycerides and low high-density lipoprotein (HDL-C) values. The addition of fenofibrate targets these variables and possibly reduces residual CVD risk, but a possible beneficial effect has been shown only in a pre-specified subgroup analysis in patients with high triglycerides and low HDL-C values. The newer proprotein convertase subtilisin/kexin type 9 inhibitors lower substantially LDL-C levels, but data from specifically designed trials in diabetic patients are not currently available. Although the cholesterol ester transfer protein (CETP) inhibitors have shown harmful effects or lack of efficacy in completed clinical trials, the newer CETP inhibitors have promising effects on lipid profile and carbohydrate metabolism, but their effects on CVD risk and safety profile have not been assessed.

Expert commentary: Clinicians have a range of pharmacological options to reduce the CVD risk of diabetic patients.     

Antiproteinuric therapy decreases LDL-cholesterol as well as HDL-cholesterol in non-diabetic proteinuric patients: relationships with cholesteryl ester transfer protein mass and adiponectin

Objective: Dyslipidemia contributes to increased cardiovascular risk in nephrotic syndrome. We questioned whether reduction in proteinuria not only lowers low-density lipoprotein cholesterol (LDL-C), but also high-density lipoprotein cholesterol (HDL-C) and cholesteryl ester transfer protein (CETP) mass and whether changes in HDL-C were related to changes in plasma adiponectin. Methods: Thirty-two non-diabetic proteinuric patients (12 on statin therapy), were followed during two double blind 6-week periods of placebo and treatment (low sodium + 100mg losartan + 25 mg hydrochlorothiazide). Results: With placebo HDL-C was lower but LDL-C and CETP were not different in proteinuric patients compared with matched controls. LDL-C, HDL-C and CETP decreased upon proteinuria reduction. The decrease in LDL-C correlated with the drop in CETP and the degree of proteinuria reduction. HDL-C also decreased in proportion to proteinuria lowering. Individual changes in HDL-C were correlated with changes in adiponectin. Conclusion: LDL-C lowering upon robust reduction of proteinuria may be affected by changes in plasma CETP mass, but this treatment also decreases HDL-C in relation to the degree of proteinuria reduction. This adverse effect on HDL-C may in part be attributable to changes in adiponectin.     

Investigational CETP antagonists for hyperlipidemia and atherosclerosis prevention

INTRODUCTION: Reverse cholesterol transport (RCT) is a function of high-density lipoproteins (HDL) in humans and higher species. It is enabled by the cholesteryl ester transfer protein (CETP), a high molecular weight protein exchanging cholesteryl esters in HDL for triglycerides in very low-density lipoproteins (VLDL). Inhibition of CETP may provide a useful strategy to raise HDL, the protective lipoprotein fraction in plasma. AREAS COVERED: Evaluation based on clinical and experimental findings of the three drugs developed or in advanced development for CETP inhibition. EXPERT OPINION: Inhibition of CETP, both inherited and drug induced, at times leads to dramatic elevations of HDL-cholesterol (HDL-C) levels. Epidemiological data presently available do not, however, provide convincing evidence that reduced CETP levels or activity due to genetic factors and associated with HDL-C elevations, reduce cardiovascular risk. Indeed, the opposite may be true in some instances. All the three CETP inhibitors were the object of experimental and clinical evaluation. Large clinical trials with torcetrapib led to very negative findings, that is, raised cardiovascular morbidity and mortality in addition to raised risk of cancer and sepsis. Off-target effects of the drug, such as aldosterone retention and raised blood pressure, were believed to provide an explanation for these negative findings. The two newer agents, dalcetrapib and anacetrapib, do not exert off-target effects. The two drugs differ because anacetrapib has a more dramatic effect on HDL cholesterolemia (+139%) versus more moderate effects of dalcetrapib (+20-30%). Anacetrapib, however, may impair formation of pre-β HDL, that is, the primary particles in the process of cholesterol removal. The initial large trial with anacetrapib (DEFINE study) in coronary patients on statin treatment, appeared to confirm a remarkable HDL raising property, together with some reduction in vascular end points, in particular coronary procedures. The issue of other potentially harmful effects of CETP inhibition (sepsis and others) has yet to be clarified. Large clinical end-point trials, however, will be necessary to provide convincing evidence that, in addition to raising HDL-C, CETP inhibitors provide a valid additional treatment, for example, to statins in patients with coronary heart disease (CHD) or at high risk of CHD.     

High-density lipoprotein cholesterol targeting for novel drug discovery: where have we gone wrong?

Lowering low-density lipoprotein-cholesterol (LDL-C) is an effective strategy to reduce cardiovascular risk. However, a significant residual risk remains in statin-treated patients. High-density lipoprotein cholesterol (HDL-C) is a strong, independent and inverse predictor of cardiovascular risk in many epidemiologic studies and has, therefore, emerged as a potential novel therapeutic target for addressing this substantial residual risk. Nevertheless, the failure of cholesteryl ester transfer protein (CETP) inhibitors and niacin in clinical trials has generated considerable speculation about the beneficial effects of HDL. Experimental studies have identified several HDL cardioprotective functions, including enhancement of macrophage reverse cholesterol transport and endothelial function and its antioxidant, anti-inflammatory and anti-thrombotic properties. Furthermore, HDL is highly heterogeneous and the atheroprotective functions of the different HDL subpopulations are not completely understood. Current available data indicate that increased HDL-C levels do not always correlate with enhanced HDL functions and, therefore, should not be considered a biomarker of HDL functionality. The clinical application of the novel HDL-based therapeutic approaches requires the development of validated and reproducible measures of key HDL functions.     

High-density lipoprotein-based drug discovery for treatment of atherosclerosis

Introduction: Although there has been great progress achieved by the use of intensive statin therapy, the burden of atherosclerotic cardiovascular disease (CVD) remains high. This has initiated the search for novel high-density lipoprotein (HDL)-based therapeutics. Recent years have witnessed a shift from traditional raising HDL-C levels to enhancing HDL functionality, in which the process of reverse cholesterol transport (RCT) has acquired much attention.

Areas covered: In this review, the authors describe the key factors involved in RCT process for potential drug targets to reduce the CVD risk. Furthermore, the review provides a summary of the effective screening methods that have been developed to target RCT and their applications. This review also introduces some new strategies currently being clinically developed, which have the potential to improve HDL function in the RCT process.

Expert opinion: It is rational that the functionality of HDL is more important than the plasma HDL-C level in the evaluation of pharmacological treatment in atherosclerosis. HDL-based strategies designed to promote macrophage RCT are a major area of current drug discovery and development for atherosclerotic diseases. A better understanding of the functionality of HDL and its relationship with atherosclerosis will expand our knowledge of the role of HDL in lipid metabolism, holding promise for a future successful HDL-based therapy.     

Identifying and attaining LDL-C goals: mission accomplished? Next target: new therapeutic options to raise HDL-C levels

Currently, low density lipoprotein cholesterol (LDL-C) levels are the main, if not the only, lipid target in the effort to reduce cardiovascular disease (CVD) morbidity and mortality. Several primary and secondary CVD prevention trials with statins shaped current guidelines and provided detailed targets across a range of CVD risk categories. These targets can be attained using effective statins or combination therapy. However, the net benefit in CVD risk reduction may be improved if we address other lipid risk factors. High density lipoprotein cholesterol (HDL-C) emerges from epidemiological studies as the most promising target. This review links the increase in HDL-C levels with clinical benefit from "old" (e.g. sustained release niacin) and new treatment options. Synthetically produced recombined apolipoprotein A-I Milano administered intravenously seems to have a marked effect in reducing the atheroma burden. The anti-cholesterol ester transfer protein (CETP) vaccine (CETi-1) produces auto-antibodies against CETP thus increasing the cholesterol ester content in HDL particles. CETP inhibitors (e.g. JTT-705 and torcetrapib) seem to be the most promising regimen to increase HDL-C levels. Torcetrapib (already in phase IIIa studies) can substantially increase HDL-C levels (up to 106%), alone or in combination with atorvastatin. HDL-C strategies, in combination with effective statins, are a new drug target aimed at a further reduction in CVD morbidity and mortality compared with statin monotherapy.     

Cardiovascular outcomes trial with anacetrapib in subjects with high cardiovascular risk – are major benefits REVEALed?

Introduction: The actions of the cholesteryl ester transfer protein (CETP) inhibitors (torcetrapib, dalcetrapib and evacetrapib) include increasing high-density lipoprotein (HDL) cholesterol, but they do not reduce cardiovascular outcomes in subjects with high cardiovascular risk. Anacetrapib also inhibits CETP, increases HDL cholesterol and lowers low-density lipoprotein (LDL) cholesterol.

Areas covered: This evaluation is of the REVEAL (Randomized Evaluation of the Effects of Anacetrapib through Lipid Modification) trial, which was a cardiovascular outcomes trial with anacetrapib in subjects with high cardiovascular risk. Consideration is given as to whether increasing HDL cholesterol, lowering LDL cholesterol or other mechanisms/factors underlying the positive outcome with this CETP inhibitor.

Expert opinion: After three years, the REVEAL trial with anacetrapib, demonstrated cardiovascular benefits, but not a reduction in coronary artery deaths. The reductions were not significant in years one and two. Thus, in my opinion, the benefits of anacetrapib were not major, and may not apply in ‘real’ world populations where adherence to medicines is lower than in REVEAL. Also, lowering LDL cholesterol and off-target mechanisms of anacetrapib may have contributed to any beneficial and/or toxic effects. Anacetrapib has a good safety profile.     

A new paradigm for managing dyslipidemia with combination therapy: laropiprant + niacin + simvastatin

Importance of the field: Despite effective lowering of low-density lipoprotein cholesterol (LDL-C) with statin for prevention of cardiovascular adverse events, residual risk remains high due to low high-density lipoprotein cholesterol (HDL-C) levels in patients with mixed dyslipidemia. As a result, alternative treatment options to raise HDL-C are being investigated intensively. Currently, niacin is the most potent lipid lowering agent for raising HDL-C levels together with lowering of triglyceride and LDL-C. Previous clinical studies have demonstrated that niacin therapy significantly reduces the risk of cardiovascular events in high risk subjects. However, the clinical use of niacin is limited by its major adverse effect, cutaneous flushing. Although the use of extended-release (ER) formulation can reduce flushing, the tolerability and compliance of niacin remains suboptimal. A selective antagonist of prostaglandin D Type 1 receptor, laropiprant, has been investigated in a number of clinical studies and shown to be effective in reducing niacin-induced flushing. Despite the potential of laropiprant in reducing niacin-induced flushing, the long-term clinical efficacy and potential off-target side effects are not well studied.

Areas covered in this reviews: In this article, the pharmacological properties, clinical efficacy and future perspective of this combination therapy of simvastatin/ER niacin/laropiprant are reviewed.

What the reader will gain: Readers will understand both the mechanism and clinical effects of the combination therapy of simvastatin/ER niacin/laropiprant.

Take home message: The triple combination therapy of simvastatin/ER niacin/laropiprant may reduce flushing side effects and facilitate a more comprehensive treatment for patients with mixed dyslipidemia.     

No cardiovascular benefit with evacetrapib – is this the end of the road for the ‘cetrapibs’?

Introduction: Increasing high-density lipoprotein(HDL) cholesterol levels predict improved cardiovascular outcomes. However, inhibiting cholesteryl ester transfer protein (CETP) to increase HDL cholesterol, with the ‘cetrapibs’ (torcetrapib and dalcetrapib), did not improve cardiovascular clinical outcomes. Despite these findings, the clinical outcomes trial with evacetrapib continued.

Areas covered: Treatment with evacetrapib increased the levels of HDL by ~130%, and decreased low-density lipoprotein (LDL) cholesterol by ~37%. However, The Assessment of Clinical Effects of Cholesteryl Ester Transfer Protein Inhibition with Evacetrapib in Patients at a High Risk for Vascular Outcomes (ACCELERATE) trial did not show reduced cardiovascular outcomes with this cetrapib. Evacetrapib may have failed because increasing HDL cholesterol may not be beneficial in the presence of coronary artery disease and/or it is possible that evacetrapib has toxic effects that counter any beneficial effects.

Expert opinion: In addition to our understanding of the relationships between CETP, HDL cholesterol and cardiovascular disease being incomplete, recent meta-analysis evidence suggests that increasing HDL cholesterol does not improve cardiovascular outcomes in subjects taking statins, and this may explain the failure of evacetrapib. Also, the preclinical characteristics of the cetrapibs, especially off-target mechanisms, were not explored prior to clinical trial, and may have contributed to the failure of cetrapibs, including evacetrapib.     

Identification of a novel,non-tetrahydroquinoline variant of the cholesteryl ester transfer protein (CETP) inhibitor torcetrapib,with improved aqueous solubility

Abstract

1.?Elaborate studies of cholesteryl ester transfer protein (CETP) polymorphisms and genetic deficiency in humans suggest direct links between CETP, high-density lipoprotein cholesterol (HDL-c) levels and coronary heart diseases. The hypothesis that CETP inhibition by small molecule inhibitors raises HDL-c has been validated clinically with structurally-diverse CETP inhibitors such as torcetrapib, anacetrapib, dalcetrapib and evacetrapib.

2.?Despite promising phase 2 results with respect to HDL-c elevation, torcetrapib was discontinued in phase 3 trials due to increased mortality rates in the cardiovascular outcomes study. Emerging evidence for the adverse effects hints at off-target chemotype-specific cardiovascular toxicity, possibly related to the pressor effects of torcetrapib, since structurally diverse CETP inhibitors such as anacetrapib, evacetrapib and dalcetrapib are not associated with blood pressure increases in humans. Nonclinical follow-up studies showed that torcetrapib induces aldosterone biosynthesis and secretion in vivo and in vitro, an effect which is not observed with other CETP inhibitors in clinical development.

3.?As part of ongoing efforts to identify novel CETP inhibitors devoid of pressor effects, strategies were implemented towards the design of compounds, which lack the 1,2,3,4-tetrahydroquinoline (THQ) scaffold present in torcetrapib. In this article, we disclose results of structure–activity relationship studies for a series of novel non-THQ CETP inhibitors, which resulted in the identification of a novel isonipecotic acid derivative 10 (also referred to as PF-04445597) with vastly improved oral pharmacokinetic properties mainly as a result of improved aqueous solubility. This feature is attractive in that, it bypasses significant investments needed to develop compatible solubilizing formulation(s) for oral drug delivery of highly lipophilic and poorly soluble compounds; attributes, which are usually associated with small molecule CETP inhibitors. PF-04445597 was also devoid of aldosterone secretion in human H295R adrenal carcinoma cells.     

Cholesteryl ester transfer protein inhibitors as high-density lipoprotein raising agents

Background: Not only hypercholesterolemia, but also low levels of high-density lipoprotein cholesterol is a critical risk factor for atherosclerosis-related disease. Therefore, there has been great interest in identifying effective and selective cholesteryl ester transfer protein (CETP) inhibitors that can raise high-density lipoprotein. Recently, Phase III clinical studies of torcetrapib, one of the CETP inhibitors developed by researchers at Pfizer, were unexpectedly terminated because of an increase in cardiovascular events and mortality. Torcetrapib has some compound-specific and off-target effects, such as raising blood pressure and aldosterone, which could affect an increase in cardiovascular events and mortality. Objective: The aim of this review is to provide an update (from 2000 to early 2009) on the patenting activity in the field of CETP inhibitors and the status of the most advanced compounds. Conclusion: Dalcetrapib (JTT-705) and anacetrapib, which have not been reported to have the off-target effects of torcetrapib, are currently in Phase III. They are expected to reveal whether CETP inhibition is beneficial for atherosclerosis-related diseases.