Chemical Synthesis, Biological Evaluation, and Cheminformatics Analysis of a Group of Chlorinated Diaryl Sulfonamides: Promising Inhibitors of Cholesteryl Ester Transfer Protein

BACKGROUND

Hyperlipidemia is characterized by an abnormally elevated serum cholesterol, triglycerides, or both. The relationship between an elevated level of LDL and cardiovascular diseases is well-established. Cholesteryl ester transfer protein (CETP) is an enzyme that moves cholesterol esters and triglycerides between LDL, VLDL, and HDL. CETP inhibition leads to a reduction in cardiovascular disease by raising HDL and minimizing LDL.

OBJECTIVE

This study synthesized ten meta-chlorinated benzene sulfonamides 6a-6j and explored their structure-activity relationship.

METHODS

The synthesized molecules were characterized using 1H-NMR, 13C-NMR, IR, and HR-MS. Moreover, cheminformatics analyses included pharmacophore mapping, LibDock studies, and cheminformatics characterization using 2-dimensional (2D) molecular descriptors and principal component analysis.

RESULTS

Based on in vitro functional CETP assays, compounds 6e, 6i, and 6j demonstrated the strongest inhibitory activities against CETP, reaching 100% inhibition. The inhibitory activity of compounds 6a-6d and 6f-6h ranged from 47.5% to 96.5% at 10 μM concentration. Pharmacophore mapping results suggested CETP inhibitory action, while the docking scores and calculated binding energies predicted favoring binding at the CETP active site. Best-scoring docking poses predicted critical hydrophobic features corresponding to key interactions with His232 and Cys13. Cheminformatics analysis using 2D molecular descriptors indicated that the synthesized compounds span various physicochemical properties and drug-likeness.

CONCLUSION

It was found that a chloro moiety at the ortho-position, or a nitro group at the meta and para-positions, improves the CETP inhibitory activity of synthesized analogs. Computational studies suggest the formation of stable ligand-protein complexes between compounds 6a- 6j and CETP.

Dissecting the Structural Dynamics of Authentic Cholesteryl Ester Transfer Protein for the Discovery of Potential Lead Compounds: A Theoretical Study

Current structural and functional investigations of cholesteryl ester transfer protein (CETP) inhibitor design are nearly entirely based on a fully active mutation (CETPMutant) constructed for protein crystallization, limiting the study of the dynamic structural features of authentic CETP involved in lipid transport under physiological conditions. In this study, we conducted comprehensive molecular dynamics (MD) simulations of both authentic CETP (CETPAuthentic) and CETPMutant. Considering the structural differences between the N- and C-terminal domains of CETPAuthentic and CETPMutant, and their crucial roles in lipid transfer, we identified the two domains as binding pockets of the ligands for virtual screening to discover potential lead compounds targeting CETP. Our results revealed that CETPAuthentic displays greater flexibility and pronounced curvature compared to CETPMutant. Employing virtual screening and MD simulation strategies, we found that ZINC000006242926 has a higher binding affinity for the N- and C-termini, leading to reduced N- and C-opening sizes, disruption of the continuous tunnel, and increased curvature of CETP. In conclusion, CETPAuthentic facilitates the formation of a continuous tunnel in the "neck" region, while CETPMutant does not exhibit such characteristics. The ligand ZINC000006242926 screened for binding to the N- and C-termini induces structural changes in the CETP unfavorable to lipid transport. This study sheds new light on the relationship between the structural and functional mechanisms of CETP. Furthermore, it provides novel ideas for the precise regulation of CETP functions.

CETP inhibitor evacetrapib enters mouse brain tissue

High levels of plasma cholesterol, especially high levels of low-density lipoprotein cholesterol (LDL-C), have been associated with an increased risk of Alzheimer's disease. The cholesteryl ester transfer protein (CETP) in plasma distributes cholesteryl esters between lipoproteins and increases LDL-C in plasma. Epidemiologically, decreased CETP activity has been associated with sustained cognitive performance during aging, longevity, and a lower risk of Alzheimer's disease. Thus, pharmacological CETP inhibitors could be repurposed for the treatment of Alzheimer's disease as they are safe and effective at lowering CETP activity and LDL-C. Although CETP is mostly expressed by the liver and secreted into the bloodstream, it is also expressed by astrocytes in the brain. Therefore, it is important to determine whether CETP inhibitors can enter the brain. Here, we describe the pharmacokinetic parameters of the CETP inhibitor evacetrapib in the plasma, liver, and brain tissues of CETP transgenic mice. We show that evacetrapib crosses the blood-brain barrier and is detectable in brain tissue 0.5 h after a 40 mg/kg i.v. injection in a non-linear function. We conclude that evacetrapib may prove to be a good candidate to treat CETP-mediated cholesterol dysregulation in Alzheimer's disease.

Serum Cholesteryl Ester Transfer Protein (CETP) and Sortilin (SORT) in Patients with Psoriasis with Relation to Systemic Treatment

Psoriasis is a common inflammatory skin disease, which is tightly associated with metabolic disorders. Cholesteryl ester transfer protein (CETP) and sortilin (SORT) are molecules engaged in lipid metabolism of proatherogenic properties. They have been hardly ever studied in psoriasis before. Serum CETP and SORT concentrations were measured in 33 patients with plaque-type psoriasis before and after 12 weeks of treatment with methotrexate or acitretin. There was no significant difference in CEPT and SORT serum concentrations between patients and controls. Positive correlations between CETP after the treatment with acitretin and activity of transaminases (R = 0.65, R = 0.56, respectively) were noted. CETP was positively related with triglycerides (R = 0.49), glucose (R = 0.54) and CRP (R = 0.64) before the treatment with methotrexate, which all disappeared afterwards. Systemic therapy with methotrexate caused normalization of SORT concentration. There was significant correlation between SORT and WBC (p < 0.01) and CRP (p < 0.05). CETP and SORT cannot be used as individual biomarkers. Nevertheless, they show some interesting relations with other parameters. Increased concentration of CETP perhaps could investigated as a marker of liver side effects of acitretin treatment in psoriatics. SORT could be considered as a new indicator of metabolically induced inflammation in psoriasis. Methotrexate may be preferred in patients with high SORT concentrations. Further studies are needed to establish their exact role in psoriatic patients.

Disturbances of the transfer of cholesterol to high-density lipoprotein (HDL) in patients with peripheral artery disease with or without type 2 diabetes mellitus

INTRODUCTION

Low high-density lipoprotein (HDL)-cholesterol is frequent in patients with peripheral artery disease (PAD) and also in type 2 diabetes mellitus (T2DM), the major risk factor for PAD. The transfer of cholesterol from the other lipoproteins to HDL is an important aspect of HDL metabolism and function, and may contribute to atherogenic mechanisms that lead to PAD development.

OBJECTIVE

The aim of this study was to investigate the status of cholesterol transfers in patients with PAD without or with T2DM.

METHODS

Patients with PAD (n = 19), with PAD and T2DM (PAD + DM, n = 19), and healthy controls (n = 20), all paired for age, sex, and BMI were studied. Transfer of both forms of cholesterol, unesterified (UC) and esterified (EC), was performed by incubating plasma with a donor nanoemulsion containing radioactive UC and EC, followed by chemical precipitation and HDL radioactive counting.

RESULTS

Low-density lipoprotein (LDL)-cholesterol and triglycerides were similar in the three groups. Compared to controls, HDL-C was lower in PAD + DM (p < 0.05), but not in PAD. Transfer of UC was lower in PAD + DM than in PAD and controls (4.18 ± 1.17%, 5.13 ± 1.44%, 6.59 ± 1.25%, respectively, p < 0.001). EC transfer tended to be lower in PAD + DM than in controls (2.96 ± 0.60 vs 4.12 ± 0.89%, p = 0.05). Concentrations of cholesteryl ester transfer protein (CETP) and lecithin-cholesterol acyltransferase (LCAT), both involved in HDL metabolism, were not different among the three groups.

CONCLUSION

Deficient cholesterol transfer to HDL may play a role in PAD pathogenesis. Since UC transfer to HDL was lower in PAD + DM compared to PAD alone, it is possible that defective HDL metabolism may contribute to the higher PAD incidence in patients with T2DM.Keywords.

Low-density lipoprotein receptor is required for cholesteryl ester transfer protein to regulate triglyceride metabolism in both male and female mice

Elevated triglycerides (TGs) and impaired TG clearance increase the risk of cardiovascular disease in both men and women, but molecular mechanisms remain poorly understood. Cholesteryl ester transfer protein (CETP) is a lipid shuttling protein known for its effects on high-density lipoprotein cholesterol. Although mice lack CETP, transgenic expression of CETP in mice alters TG metabolism in males and females by sex-specific mechanisms. A unifying mechanism explaining how CETP alters TG metabolism in both males and females remains unknown. Since low-density lipoprotein receptor (LDLR) regulates both TG clearance and very low density lipoprotein (VLDL) production, LDLR may be involved in CETP-mediated alterations in TG metabolism in both males and females. We hypothesize that LDLR is required for CETP to alter TG metabolism in both males and females. We used LDLR null mice with and without CETP to demonstrate that LDLR is required for CETP to raise plasma TGs and to impair TG clearance in males. We also demonstrate that LDLR is required for CETP to increase TG production and to increase the expression and activity of VLDL synthesis targets in response to estrogen. Additionally, we show that LDLR is required for CETP to enhance β-oxidation. These studies support that LDLR is required for CETP to regulate TG metabolism in both males and females.

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.

Investigational therapies for hypercholesterolemia

INTRODUCTION

Cardiovascular morbidity and mortality are of increasing concern, not only to patients but also to the health care profession and service providers. The preventative benefit of treatment of dyslipidaemia is unquestioned but there is a large, so far unmet need to improve clinical outcome. There are exciting new discoveries of targets that may translate into improved clinical outcome. Areas covered: This review highlights some new pathways in cholesterol and triglyceride metabolism and examines new targets, new drugs and new molecules. The review includes the results of recent trials of relatively new drugs that have shown benefit in cardiovascular endpoint outcomes, drugs that have been licenced without endpoint trials yet available and new drugs that have not yet been licenced but have produced exciting results in animal studies and some in early phase 2 human studies. Expert opinion: The new areas that have been discovered as the cause of dyslipidaemia have opened up a host of new targets for new drugs including antisense RNA's, microRNA's and human monoclonal antibodies. The plethora of new targets and new drugs has made it an extraordinarily exciting time in the development of therapeutics to combat atherosclerosis.

Structural Plasticity of Cholesteryl Ester Transfer Protein Assists the Lipid Transfer Activity

Cholesteryl ester transfer protein (CETP) mediates the transfer of cholesteryl esters (CEs) and triglycerides between different lipoproteins. Recent studies have shown that blocking the function of CETP can increase the level of HDL cholesterol in blood plasma and suppress the risk of cardiovascular disease. Hence, understanding the structure, dynamics, and mechanism by which CETP transfers the neutral lipids has received tremendous attention in last decade. Although the recent crystal structure has provided direct evidence of the existence of strongly bound CEs in the CETP core, very little is known about the mechanism of CE/triglyceride transfer by CETP. In this study, we explore the large scale dynamics of CETP by means of multimicrosecond molecular dynamics simulations and normal mode analysis, which provided a wealth of detailed information about the lipid transfer mechanism of CETP. Results show that the bound CEs intraconvert between bent and linear conformations in the CETP core tunnel as a consequence of the high degree of conformational flexibility of the protein. During the conformational switching, there occurred a significant reduction in hydrophobic contacts between the CEs and CETP, and a continuous tunnel traversing across the CETP long axis appeared spontaneously. Thus, our results support the recently proposed "tunnel mechanism" of CETP from cryo-EM studies for the transfer of neutral lipids between different lipoproteins. The detailed understanding obtained here could help in devising methods to prevent CETP function as a cardiovascular disease therapeutic.

Cholesteryl ester transfer protein (CETP) deficiency and CETP inhibitors

Epidemiologic studies have shown that low-density lipoprotein cholesterol (LDL-C) is a strong risk factor, whilst high-density lipoprotein cholesterol (HDL-C) reduces the risk of coronary heart disease (CHD). Therefore, strategies to manage dyslipidemia in an effort to prevent or treat CHD have primarily attempted at decreasing LDL-C and raising HDL-C levels. Cholesteryl ester transfer protein (CETP) mediates the exchange of cholesteryl ester for triglycerides between HDL and VLDL and LDL. We have published the first report indicating that a group of Japanese patients who were lacking CETP had extremely high HDL-C levels, low LDL-C levels and a low incidence of CHD. Animal studies, as well as clinical and epidemiologic evidences, have suggested that inhibition of CETP provides an effective strategy to raise HDL-C and reduce LDL-C levels. Four CETP inhibitors have substantially increased HDL-C levels in dyslipidemic patients. This review will discuss the current status and future prospects of CETP inhibitors in the treatment of CHD. At present anacetrapib by Merck and evacetrapib by Eli Lilly are under development. By 100mg of anacetrapib HDL-C increased by 138%, and LDL-C decreased by 40%. Evacetrapib 500 mg also showed dramatic 132% increase of HDL-C, while LDL-C decreased by 40%. If larger, long-term, randomized, clinical end point trials could corroborate other findings in reducing atherosclerosis, CETP inhibitors could have a significant impact in the management of dyslipidemic CHD patients. Inhibition of CETP synthesis by antisense oligonucleotide or small molecules will produce more similar conditions to human CETP deficiency and may be effective in reducing atherosclerosis and cardiovascular events. We are expecting the final data of prospective clinical trials by CETP inhibitors in 2015.

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.