Cholesteryl Ester Transfer Protein Inhibitor Anacetrapib Research Articles

CETP inhibition enhances monocyte activation and bacterial clearance and reduces streptococcus pneumonia-associated mortality in mice.

Sepsis is a leading cause of mortality worldwide, and pneumonia is the most common cause of sepsis in humans. Low levels of high-density lipoprotein cholesterol (HDL-C) levels are associated with an increased risk of death from sepsis, and increasing levels of HDL-C by inhibition of cholesteryl ester transfer protein (CETP) decreases mortality from intraabdominal polymicrobial sepsis in APOE*3-Leiden.CETP mice. Here, we show that treatment with the CETP inhibitor (CETPi) anacetrapib reduced mortality from Streptococcus pneumoniae-induced sepsis in APOE*3-Leiden.CETP and APOA1.CETP mice. Mechanistically, CETP inhibition reduced the host proinflammatory response via attenuation of proinflammatory cytokine transcription and release. This effect was dependent on the presence of HDL, leading to attenuation of immune-mediated organ damage. In addition, CETP inhibition promoted monocyte activation in the blood prior to the onset of sepsis, resulting in accelerated macrophage recruitment to the lung and liver. In vitro experiments demonstrated that CETP inhibition significantly promoted the activation of proinflammatory signaling in peripheral blood mononuclear cells and THP1 cells in the absence of HDL; this may represent a mechanism responsible for improved bacterial clearance during sepsis. These findings provide evidence that CETP inhibition represents a potential approach to reduce mortality from pneumosepsis.

The Cholesteryl Ester Transfer Protein Inhibitor, des-Fluoro-Anacetrapib, Prevents Vein Bypass-induced Neointimal Hyperplasia in New Zealand White Rabbits

Coronary artery bypass grafting is among the most commonly performed of all cardiovascular surgical procedures. However, graft failure due to stenosis reduces the long-term benefit of the intervention. This study asks if elevating plasma high density lipoprotein cholesterol (HDL-C) levels by inhibition of cholesteryl ester transfer protein (CETP) activity with des-fluoro-anacetrapib, an analog of the CETP inhibitor anacetrapib, prevents vein bypass-induced neointimal hyperplasia. NZW rabbits were placed on a normal chow diet or chow containing 0.14% (wt/wt) des-fluoro-anacetrapib for 6 weeks. Bypass grafting of the jugular vein to the common carotid artery was performed 2 weeks after starting dietary des-fluoro-anacetrapib supplementation. The animals were euthanised 4 weeks post-bypass grafting. Relative to control, dietary supplementation with des-fluoro-anacetrapib reduced plasma CETP activity by 89 ± 6.9%, increased plasma apolipoprotein A-I levels by 24 ± 5.5%, increased plasma HDL-C levels by 93 ± 26% and reduced intimal hyperplasia in the grafted vein by 38 ± 6.2%. Des-fluoro-anacetrapib treatment was also associated with decreased bypass grafting-induced endothelial expression of vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1), endothelial dysfunction, and smooth muscle cell (SMC) proliferation in the grafted vein. In conclusion, increasing HDL-C levels by inhibiting CETP activity is associated with inhibition of intimal hyperplasia in grafted veins, reduced inflammatory responses, improved endothelial function, and decreased SMC proliferation.

Impact of ADCY9 Genotype on Response to Anacetrapib.

Exploratory analyses of previous randomized trials generated a hypothesis that the clinical response to cholesteryl ester transfer protein (CETP) inhibitor therapy differs by ADCY9 genotype, prompting the ongoing dal-GenE trial in individuals with a particular genetic profile. The randomized placebo-controlled REVEAL trial (Randomized Evaluation of the Effects of Anacetrapib through Lipid-Modification) demonstrated the clinical efficacy of the CETP inhibitor anacetrapib among patients with preexisting atherosclerotic vascular disease. In the present study, we examined the impact of ADCY9 genotype on response to anacetrapib in the REVEAL trial. Individuals with stable atherosclerotic vascular disease who were treated with intensive atorvastatin therapy received either anacetrapib 100 mg daily or matching placebo. Cox proportional hazards models, adjusted for the first 5 principal components of ancestry, were used to estimate the effects of allocation to anacetrapib on major vascular events (a composite of coronary death, myocardial infarction, coronary revascularization, or presumed ischemic stroke) and the interaction with ADCY9 rs1967309 genotype. Among 19 210 genotyped individuals of European ancestry, 2504 (13.0%) had a first major vascular event during 4 years median follow-up: 1216 (12.6%) among anacetrapib-allocated participants and 1288 (13.4%) among placebo-allocated participants. Proportional reductions in the risk of major vascular events with anacetrapib did not differ significantly by ADCY9 genotype: hazard ratio (HR) = 0.92 (95% CI, 0.81-1.05) for GG; HR = 0.94 (95% CI, 0.84-1.06) for AG; and HR = 0.93 (95% CI, 0.76-1.13) for AA genotype carriers, respectively; genotypic P for interaction = 0.96. Furthermore, there were no associations between ADCY9 genotype and the proportional reductions in the separate components of major vascular events or meaningful differences in lipid response to anacetrapib. The REVEAL trial is the single largest study to date evaluating the ADCY9 pharmacogenetic interaction. It provides no support for the hypothesis that ADCY9 genotype is materially relevant to the clinical effects of the CETP inhibitor anacetrapib. The ongoing dal-GenE study will provide direct evidence as to whether there is any specific pharmacogenetic interaction with dalcetrapib. URL: https://www. gov. Unique identifier: NCT01252953. URL: http://www.isrctn.com. Unique identifier: ISRCTN48678192. URL: https://www.clinicaltrialsregister.eu. Unique identifier: 2010-023467-18.

Mendelian randomization reveals unexpected effects of CETP on the lipoprotein profile.

According to the current dogma, cholesteryl ester transfer protein (CETP) decreases high-density lipoprotein (HDL)-cholesterol (C) and increases low-density lipoprotein (LDL)-C. However, detailed insight into the effects of CETP on lipoprotein subclasses is lacking. Therefore, we used a Mendelian randomization approach based on a genetic score for serum CETP concentration (rs247616, rs12720922 and rs1968905) to estimate causal effects per unit (µg/mL) increase in CETP on 159 standardized metabolic biomarkers, primarily lipoprotein subclasses. Metabolic biomarkers were measured by nuclear magnetic resonance (NMR) in 5672 participants of the Netherlands Epidemiology of Obesity (NEO) study. Higher CETP concentrations were associated with less large HDL (largest effect XL-HDL-C, P = 6 × 10-22) and more small VLDL components (largest effect S-VLDL cholesteryl esters, P = 6 × 10-6). No causal effects were observed with LDL subclasses. All these effects were replicated in an independent cohort from European ancestry (MAGNETIC NMR GWAS; n ~20,000). Additionally, we assessed observational associations between ELISA-measured CETP concentration and metabolic measures. In contrast to results from Mendelian randomization, observationally, CETP concentration predominantly associated with more VLDL, IDL and LDL components. Our results show that CETP is an important causal determinant of HDL and VLDL concentration and composition, which may imply that the CETP inhibitor anacetrapib decreased cardiovascular disease risk through specific reduction of small VLDL rather than LDL. The contrast between genetic and observational associations might be explained by a high capacity of VLDL, IDL and LDL subclasses to carry CETP, thereby concealing causal effects on HDL.

Cholesteryl Ester Transfer Protein Inhibitors as Agents to Reduce Coronary Heart Disease Risk.

Cholesteryl ester transfer protein (CETP) promotes the transfer of cholesteryl esters from the nonatherogenic high density lipoprotein (HDL) fraction to potentially proatherogenic non-HDL fractions. Inhibition of CETP reduces the concentration of non-HDL cholesterol, enhances HDL functionality, and increases the concentration of HDL cholesterol and apoA-I. Despite an absence of benefit in earlier trials of CETP inhibition, the REVEAL trial has shown that treatment with the CETP inhibitor anacetrapib reduces the risk of having a coronary event in high-risk, statin-treated patients.

High-Density Lipoprotein Function in Cardiovascular Disease and Diabetes Mellitus.

Cardiovascular disease (CVD) is the most common cause of death worldwide.1 Major CVD risk factors are hypertension, smoking, physical inactivity, abnormal glucose levels/diabetes mellitus, and dyslipidemia. Among these, dyslipidemia characterized by a low level of HDL-C (high-density lipoprotein cholesterol) is strongly and inversely correlated with CVD risk,2–4 and low HDL-C levels is part of the atherogenic dyslipidemia complex associated with diabetes mellitus.5 These observations triggered intense interest in increasing HDL-C levels for therapeutic intervention of CVD.6,7 However, several recent lines of evidence now suggest that the association between HDL-C levels and CVD status may be indirect or more complicated than previously recognized.7 Thus, human genetic studies demonstrate that genetically altered HDL-C levels do not necessarily translate to an altered risk of CVD.8–12 Phase III clinical trials of drugs that elevate HDL-C, such as niacin and CETP (cholesteryl ester transfer protein) inhibitors, also have largely failed to reduce CVD events in statin-treated subjects with established CVD.13–15 For several CETP inhibitors, improvement in CVD prevention was unsuccessful because of off-target effects (torcetrapib) or lack of efficacy (dalcetrapib and evacetrapib).14,16–18 The exception is the recent REVEAL trial (Randomized Evaluation of the Effects of Anacetrapib Through Lipid-Modification), which included more subjects and was performed for longer than previous CETP inhibitor trials. The REVEAL demonstrated that the CETP inhibitor anacetrapib exhibited beneficial effects on cardiovascular outcomes on top of those of statin therapy, although the risk reduction was moderate19,20 and might have been due, at least in part, to a reduction in non-HDL-C rather than elevated HDL-C.21 Considering these cumulative observations, it remains uncertain whether increased HDL-C directly impacts atherosclerosis and the …

Abstract 23077: The Effects Of Prolonged Anacetrapib Therapy On First And Subsequent Occlusive Vascular Events

Background: There is definitive evidence that lowering LDL-cholesterol with statins as monotherapy, or in combination with ezetimibe or PCSK9 inhibitors, prevents not only first but also subsequent major coronary events (i.e. coronary death, myocardial infarction or coronary revascularization). Consequently, prolonged treatment produces greater absolute reductions in morbidity, mortality and economic costs. Inhibition of cholesteryl ester transfer protein (CETP) by anacetrapib lowers LDL-cholesterol levels, as well as substantially increasing HDL-cholesterol, but it is not yet known if it produces benefits on first and subsequent occlusive vascular events and deaths. Methods: The HPS3/TIMI55-REVEAL trial has assessed the effects of adding the CETP inhibitor anacetrapib to atorvastatin on vascular morbidity and mortality in 30,449 individuals who had a history of atherosclerotic vascular disease. Study treatment was continued for a median of 4.1 years. Information was recorded on first and subsequent cardiovascular events that occurred during the scheduled treatment period. Results: The main trial results are to be presented at the European Society of Cardiology Congress in August 2017. For the American Heart Association Congress, it is proposed to present more detailed results on the effects of anacetrapib on first and subsequent occlusive vascular events. Within this high-risk population of individuals with pre-existing vascular disease, 3443 (11%) had a first major coronary event and 1097 subsequent events were reported during the scheduled treatment period. Conclusions: Unblinded results of the cumulative effects of anacetrapib on first and subsequent rates of coronary and other occlusive vascular events will be available for presentation.

Trials and Tribulations of CETP Inhibitors.

The development of CETP (cholesteryl ester transfer protein) inhibitors has had a long and difficult course with 3 compounds failing in phase III clinical trials. Finally, the REVEAL (Randomized Evaluation of the Effects of Anacetrapib through Lipid modification) trial has shown that the CETP inhibitor anacetrapib decreased coronary heart disease when added to statin therapy. Although the result is different to earlier studies, this is likely related to the size and duration of the trial. The benefit of anacetrapib seems to be largely explained by lowering of non-HDL-C (high-density lipoprotein cholesterol), rather than increases in HDL-C. Although the magnitude of benefit for coronary heart disease appeared to be moderate, in part this may have reflected aspects of the trial design. Anacetrapib treatment was associated with a small increase in blood pressure, but was devoid of major side effects and was also associated with a small reduction in diabetes mellitus. Treatment with CETP inhibitors, either alone or in combination with statins, could provide another option for patients with coronary disease who require further reduction in LDL (low-density lipoprotein) and non-HDL-C.

Effect of compounds affecting ABCA1 expression and CETP activity on the HDL pathway involved in intestinal absorption of lutein and zeaxanthin.

The antioxidant xanthophylls lutein and zeaxanthin are absorbed from the diet in a process involving lipoprotein formation. Selective mechanisms exist for their intestinal uptake and tissue-selective distribution, but these are poorly understood. We investigated the role of high-density lipoprotein (HDL), apolipoprotein (apo) A1 and ATP-binding cassette transporter (ABC) A1 in intestinal uptake of lutein in a human polarized intestinal cell culture and a hamster model. Animals received dietary lutein and zeaxanthin and either a liver X receptor (LXR) agonist or statin, which up- or down-regulate intestinal ABCA1 expression, respectively. The role of HDL was studied following treatment with the cholesteryl ester transfer protein (CETP) modulator dalcetrapib or the CETP inhibitor anacetrapib. In vitro, intestinal ABCA1 at the basolateral surface of enterocytes transferred lutein and zeaxanthin to apoA1, not to mature HDL. In hamsters, plasma lutein and zeaxanthin levels were markedly increased with the LXR agonist and decreased with simvastatin. Dalcetrapib, but not anacetrapib, increased plasma and liver lutein and zeaxanthin levels. ABCA1 expression and apoA1 acceptor activity are important initial steps in intestinal uptake and maintenance of lutein and zeaxanthin levels by an HDL-dependent pathway. Their absorption may be improved by physiological and pharmacological interventions affecting HDL metabolism.

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

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. 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. 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.

Abstract 246: Anacetrapib Adds to the Antiatherogenic Effect of Atorvastatin, Mainly by Increasing the Clearance of Non-HDL Cholesterol

Introduction: The residual risk that remains after statin treatment 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 anacetrapib on lipid metabolism, HDL function and atherosclerosis, 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/d), atorvastatin (2.4 mg/kg/d) alone or in combination with anacetrapib (0.3 mg/kg/d) for 21 weeks. Anacetrapib dose-dependently reduced CETP activity (-59% to -100%, P&lt;0.01), thereby decreasing nonHDL-C (-24% to -45%, P&lt;0.001) and increasing HDL-C (+30% to +86%, P&lt;0.001). Anacetrapib did not affect HDL function. Additionally, we showed that anacetrapib reduced nonHDL-C mainly by increasing the clearance by the liver. Anacetrapib dose-dependently reduced atherosclerotic lesion area (-41% to -92%, P&lt;0.01) and severity, increased the plaque stability index and added to the effects of atorvastatin by further decreasing lesion size (-95%, P&lt;0.001) and severity. Analysis of covariance showed that both anacetrapib (P&lt;0.05) and nonHDL-C (P&lt;0.001), but not HDL-C (P=0.76), independently decreased lesion size. Conclusions: Anacetrapib reduces atherosclerosis, and adds to the anti-atherogenic effect of atorvastatin. The anti-atherogenic effect is mainly ascribed to a reduction in nonHDL-C, as a consequence of an increased clearance. In addition, anacetrapib improves lesion stability.

Abstract 119: LCAT Activation in Combination with the CETP Inhibitor Anacetrapib Results in Enhanced Cholesterol Efflux and a Favorable Lipid Profile in Dyslipidemic Hamsters

Lecithin cholesterol acyltransferase (LCAT) is a key enzyme involved in the metabolism of HDL. LCAT synthesizes cholesterol esters (CE) in plasma by catalyzing the transfer of the sn-2 fatty acid of phosphatidylcholine to cholesterol on HDL. The hydrophobic CE moves to the core of the HDL particle which results in HDL maturation and a progressive enlargement of the particle. Cholesteryl ester transfer protein (CETP) is a plasma protein that facilitates the transport of CE from HDL to ApoB-containing lipoproteins. CETP inhibition has been identified as a potential strategy for lowering LDL-c and raising HDL cholesterol levels for the treatment of CVD. The purpose of the current study was to test the hypothesis that CETP inhibition in the context of LCAT activation might yield an unfavorable lipoprotein profile (e.g. dysfunctional HDL). We measured plasma lipoprotein (via FPLC), particle size and ex vivo cholesterol efflux from dyslipidemic hamsters chronically treated with a small molecule LCAT activator (20 and 60 mpk/day) in the presence or absence of the CETP inhibitor anacetrapib (20mpk/day). As expected, anacetrapib significantly reduced LDL-c (-45%) and increased HDL-c (+63%) after chronic treatment. LCAT activation reduced TG (-35%) and increased HDL-c (+40-68%) but had no effect on LDL-c. Both treatments led to an apparent increase in HDL particle size as measured by FPLC. Additionally, LCAT activation showed a significant reduction in ABCA1-mediated efflux, presumably due to the resulting increase in HDL particle size. Animals that received both anacetrapib and the LCAT activator maintained the favorable lipid profile observed with single treatment. Moreover, HDL from hamsters treated with both LCATa and CETPi demonstrated a significant increase in ABCG1- and SRB1-mediated efflux whereas single treatment did not exhibit a measurable effect. We provide evidence that LCAT activation in the context of a CETP inhibitor, maintains a favorable lipid profile (lower LDL-c) and appear s to have a synergistic effect on cholesterol efflux.

Abstract 69: Anacetrapib Dose-dependently Decreases Atherosclerosis Development and Adds to the Beneficial Effects of Atorvastatin in APOE*3Leiden.CETP Mice

Introduction The residual risk of cardiovascular disease that remains after statin treatment has triggered the search for a secondary treatment target. Epidemiological studies propose HDL-cholesterol (HDL-C) as a possible candidate. Cholesteryl ester transfer protein (CETP) transfers cholesteryl esters from atheroprotective HDL to atherogenic (V)LDL. In human intervention trials, the CETP inhibitor anacetrapib decreases (V)LDL-C by 30-40% and increases HDL-C by 40-140%. Hypothesis Complete inhibition of CETP activity may result in adverse effects as compared to partial inhibition due to the appearance of a dysfunctional HDL. We, therefore, evaluated the effect of a broad treatment window of anacetrapib-induced CETP inhibition with partial to full inhibition, as well as the combination of atorvastatin and anacetrapib on atherosclerosis development in APOE*3Leiden.CETP mice. Methods Female mice were fed a Western-type diet containing 0.1% cholesterol without or with incremental dosages of anacetrapib (0.03; 0.3; 3; 30 mg/kg/d), atorvastatin (2.4 mg/kg/d) or a combination of anacetrapib (0.3 mg/kg/d) and atorvastatin (2.4 mg/kg/d) for 20 weeks. Effects on plasma lipids, CETP activity and levels, as well as atherosclerotic lesion size and severity were assessed. Results Anacetrapib dose-dependently reduced CETP activity (-60% to -100%, P&lt;0.001) and increased CETP levels (+13% to +31%, P&lt;0.05), thereby decreasing nonHDL-C (-23% to -44%, P&lt;0.001) and increasing HDL-C (+32% to +88%, P&lt;0.001). Atorvastatin decreased CETP activity (-29%, P&lt;0.001) and nonHDL-C (-36%, P&lt;0.001). Anacetrapib dose-dependently decreased atherosclerotic lesion size (-36%, P&lt;0.05 to -92%, P&lt;0.001) and the percentage severe lesions. Anacetrapib added to the effects of atorvastatin by further reducing nonHDL-C (-36%, P&lt;0.001), increasing HDL-C (+72%, P&lt;0.001) and decreasing lesion size (-86%, P&lt;0.001) and severity. Results on lesion composition are pending. Conclusions Anacetrapib dose-dependently decreases atherosclerosis development and adds to the beneficial effects of atorvastatin in APOE*3Leiden.CETP mice. Total blockage of CETP activity does not reveal adverse effects as compared to partial blockage.

Measurement of LDL-C after treatment with the CETP inhibitor anacetrapib

Estimation of low-density lipoprotein cholesterol (LDL-C) using the Friedewald (FR) formula is often inaccurate when triglycerides are elevated or VLDL particle composition is altered. We hypothesized that LDL-C estimation by the FR formula and other measurement methods might also be inaccurate in individuals treated with a cholesteryl ester transfer protein (CETP) inhibitor. An assay comparison study was conducted using pre and posttreatment serum samples from 280 of the 811 patients treated with the CETP inhibitor anacetrapib in the DEFINE study (determining the efficacy and tolerability of CETP inhibition with anacetrapib). After 24 weeks of treatment with anacetrapib, mean LDL-C values by FR formula, Roche direct method (RDM) and Genzyme direct method (GDM) deviated from that measured by the β-quantification (BQ) reference method by -12.2 ± 7.5, -10.2 ± 6.6, -10.8 ± 8.8 mg/dl, respectively. After treatment with anacetrapib, the FR formula and detergent-based direct methods provided lower LDL-C values than those obtained by the BQ reference method. The bias by the FR formula appeared to be due to an overestimation of VLDL-C by the TG/5 component of the formula. Evaluation of the clinical significance of these findings awaits comprehensive lipid and cardiovascular outcome data from ongoing Phase III clinical studies of anacetrapib.

Abstract 168: Effects of the CETP Inhibitor Anacetrapib on HDL3-to-HDL2 Transfer: Comparison of in Vitro and in Vivo Methodologies

Cholesteryl ester transfer protein (CETP) is a target for the treatment of dyslipidemia and coronary artery disease. In addition to the well-known effect of CETP to transfer CE from HDL to LDL and to VLDL, in vitro , CETP has been reported to transfer CE between small and large HDL particles (HDL2 and HDL3, respectively). We sought to understand how the CETP inhibitor anacetrapib (ANA) affects HDL3-to-HDL2 transfer under both in vitro and in vivo conditions. In vitro , ANA dose-dependently inhibited transfer of 3 H-CE from total HDL to LDL (IC50 30nM), and from isolated HDL3 to HDL2 particles (IC50 200nM). In human CETP transgenic mice, animals treated with a single dose of ANA (100mg/kg) displayed 80% maximal reduction in plasma CETP activity and a 22% increase in total HDL cholesterol. In animals treated with either vehicle or ANA, 3 H-CE-labeled HDL3 was injected intravenously and 3 H-tracer was monitored in lipoprotein fractions following injection. Animals treated with ANA showed an increase in the amount 3 H-tracer present in HDL2 compared to vehicle over time (20-70% increase across 6 hrs post 3 H-CE-HDL3 injection, P&lt;0.05 vs vehicle). The HDL2 CE pool was also increased with ANA treatment, and 3 H-cholesterol flux into HDL2 was increased with ANA treatment when adjusted to the change in pool size (at 2 and 4 hrs post 3H-CE-HDL3 injection). No change in HDL2 3 H-tracer was seen in C57BL6 mice (lacking CETP) treated with ANA. These results indicate that in contrast to in vitro findings, ANA increases flux of CE into HDL2 in vivo , a process which likely involves multiple pathways. Therefore, the in vitro phenomena of 1) HDL3-to-HDL2 transfer by CETP and 2) inhibition of this transfer by CETP inhibitors are not recapitulated in vivo . It is clear that in vivo approaches are necessary to understand the relevance of HDL3-to-HDL2 transfer in vivo , and to accurately study the effects of CETP inhibition on lipoprotein metabolism.

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.

HDL Metabolism and CETP Inhibition

High density lipoprotein-cholesterol (HDL-C) concentration in the blood is independently and inversely associated with an increased risk of coronary heart disease. Some of the cholesterol-lowering drugs (niacin, fibrates, and statins) incidentally raise HDL-C. These drugs are not effective in causing major changes in HDL-C. Since the discovery of human genetic cholesteryl ester transfer protein (CETP) deficiency in a Japanese population with high levels of HDL-C and apolipoprotein A-I, CETP inhibition has become a novel strategy for raising HDL-C in humans. Mice, a species naturally lacking CETP, were transduced with the human CETP gene, which resulted in dose-related reductions in HDL-C. Rabbits, a species with naturally high levels of CETP, were fed a synthetic CETP inhibitor, JTT-705, leading to both a 90% increase in HDL-C and a 70% reduction in aortic atherosclerotic lesion area. Human intervention trials with a new potent and selective CETP inhibitor, torcetrapib, have taken place. In a phase I multidose trial, HDL-C increased by 91% with torcetrapib 120 mg twice daily. A phase II trial conducted with multiple combinations of torcetrapib and atorvastatin showed that the combination was well tolerated and doses 30 mg and higher of torcetrapib caused 8.3-40.2% changes from baseline HDL-C across the dose range of atorvastatin at 12 weeks. Recently the phase III clinical trial ILLUMINATE (Investigation of Lipid Level Management to Understand its Impact in Atherosclerotic Events) was prematurely terminated because of an increase in mortality in the torcetrapib/atorvastatin treatment arm compared with atorvastatin used alone. In companion studies no improvement in carotid or coronary atherosclerosis could be detected in patients treated with the torcetrapib/atorvastatin combination despite favorable changes in both low density lipoprotein (LDL)- and HDL-cholesterol levels. The future for CETP inhibition with drug therapy is now unclear, and must include a closer look at CETP inhibitor's effects on blood pressure and HDL itself. Accordingly, it was recently shown in 2 double-blind, placebo-controlled, randomized, phase I studies with the CETP inhibitor anacetrapib in healthy individuals and in patients with dyslipidemias that the drug increased HDL and reduced LDL, while having no effect on blood pressure.