Safety, tolerability and pharmacokinetics of dalcetrapib following single and multiple ascending doses in healthy subjects: a randomized, double-blind, placebo-controlled, phase I study

A Randomized, Parallel, Open-Label, Single-Dose and Multiple-Dose Clinical Trial to Investigate the Pharmacokinetic, Pharmacodynamic, and Safety Profiles of Obicetrapib in Healthy Participants in China

Obicetrapib is a selective cholesteryl ester transfer protein (CETP) inhibitor. Previous research has demonstrated similar pharmacokinetic (PK) responses to single doses of obicetrapib between Japanese and White males, but the PK responses have not been established in Chinese individuals. The purpose of this randomized, parallel, open-label trial was to characterize the PK and pharmacodynamic (PD; CETP activity and plasma lipids) responses and safety of single doses (5, 10, or 25 mg; N = 36) and multiple doses (10 mg for 14 days; N = 12) of obicetrapib in healthy Chinese individuals. The maximum concentration and area under the drug concentration-time curve of obicetrapib from 0 h to infinity increased with dose after all single doses of obicetrapib. After 7 consecutive days of dosing, low-density lipoprotein cholesterol and high-density lipoprotein cholesterol reached their minimum and maximum changes of 42% reduction and 108% increase, respectively. Primary PK and PD parameters after single- and multiple-dose administration of obicetrapib were similar to those in healthy white participants in previous studies. One participant in the 5 mg dose group experienced a treatment-emergent adverse event of decreased white blood cell and neutrophil counts, which resolved without intervention. In conclusion, these findings support the inclusion of Chinese individuals in the ongoing phase 3 clinical development program of obicetrapib.

Inhibition of the 3CL Protease and SARS-CoV-2 Replication by Dalcetrapib

The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) 3CL protease is a promising target for inhibition of viral replication by interaction with a cysteine residue (Cys145) at its catalytic site. Dalcetrapib exerts its lipid-modulating effect by binding covalently to cysteine 13 of a cholesteryl ester transfer protein. Because 12 free cysteine residues are present in the 3CL protease, we investigated the potential of dalcetrapib to inhibit 3CL protease activity and SARS-CoV-2 replication. Molecular docking investigations suggested that dalcetrapib-thiol binds to the catalytic site of the 3CL protease with a delta G value of -8.5 kcal/mol. Dalcetrapib inhibited both 3CL protease activity in vitro and viral replication in Vero E6 cells with IC₅₀ values of 14.4 ± 3.3 μM and an EC₅₀ of 17.5 ± 3.5 μM (mean ± SD). Near-complete inhibition of protease activity persisted despite 1000-fold dilution after ultrafiltration with a nominal dalcetrapib-thiol concentration of approximately 100 times below the IC₅₀ of 14.4 μM, suggesting stable protease-drug interaction. The inhibitory effect of dalcetrapib on the SARS-CoV-2 3CL protease and viral replication warrants its clinical evaluation for the treatment of COVID-19.

The influence of multiple oral administration on the pharmacokinetics and distribution profile of dalcetrapib in rats

We investigated the influence of multiple oral administration on the accumulation of dalcetrapib (JTT-705/RO4607381), a novel cholesteryl ester transfer protein inhibitor, in rats. It is well known that orally administered dalcetrapib is rapidly hydrolysed to its active form, which has a sulfhydryl group, in the body. The active form then binds covalently to endogenous thiols via mixed disulfide bonds. Following multiple once daily oral administration of ¹⁴C-dalcetrapib for seven days to rats, the concentration of radioactivity in the plasma and almost all tissues reached the steady state by day 4. At 24 h after the last dose, there was a relatively high concentration of radioactivity in the mesenteric lymph nodes, liver, adrenal glands and fat. After the last dose to rats, the radioactivity was almost completely recovered in the urine and faeces, indicating that dalcetrapib is not retained in the body, probably due to the reversibility of the disulfide bonds despite being covalent bonds.

Clinical Pharmacokinetics and Pharmacodynamics of Dalcetrapib

The cholesterol ester transfer protein (CETP) inhibitor dalcetrapib has been under evaluation for its potential to prevent cardiovascular (CV) events for almost two decades. The current clinical development program, representing new advances in precision medicine and focused on a genetically defined population with acute coronary syndrome (ACS), is supported by a large body of pharmacokinetic and pharmacodynamic data as well as substantial clinical experience in over 13,000 patients and volunteers. Dalcetrapib treatment of 600 mg/day produces significant inhibition of CETP activity, and has been utilized in phase II and III studies, including CV endpoint trials. Numerous studies have investigated the interactions between dalcetrapib and most drugs commonly prescribed to CV patients and have not demonstrated any clinically significant effects. Evaluations in patients with renal and hepatic impairment demonstrate a greater exposure to dalcetrapib than in the non-impaired population, but long-term clinical studies including patients with mild to moderate hepatic and renal dysfunction demonstrate no increase in adverse events. Safety pharmacology and toxicology studies as well as the clinical safety experience support the continuing development of dalcetrapib as an adjunct to ‘standard of care’ for the ACS population. This article provides a full review of the pharmacokinetics, as well as pharmacodynamics and pharmacology, of dalcetrapib in the context of a large clinical program.

Present therapeutic role of cholesteryl ester transfer protein inhibitors

Therapeutic interventions aimed at increasing high-density lipoprotein (HDL) levels in order to reduce the residual cardiovascular (CV) risk of optimally drug treated patients have not provided convincing results, so far. Transfer of cholesterol from extrahepatic tissues to the liver appears to be the major atheroprotective function of HDL, and an elevation of HDL levels could represent an effective strategy. Inhibition of the cholesteryl ester transfer protein (CETP), raising HDL-cholesterol (HDL-C) and apolipoprotein A-I (apoA-I) levels, reduces low-density lipoprotein-cholesterol (LDL-C) and apoB levels, thus offering a promising approach. Despite the beneficial influence on cholesterol metabolism, off-target effects and lack of reduction in CV events and mortality (with torcetrapib, dalcetrapib and evacetrapib) highlighted the complex mechanism of CETP inhibition. After the failure of the above mentioned inhibitors in phase III clinical development, possibly due to the short duration of the trials masking benefit, the secondary prevention REVEAL trial has recently shown that the inhibitor anacetrapib significantly raised HDL-C (+104%), reduced LDL-C (-18%), with a protective effect on major coronary events (RR, 0.91; 95%CI, 0.85-0.97; p = 0.004). Whether LDL-C lowering fully accounts for the CV benefit or if HDL-C-rise is a crucial factor still needs to be determined, although the reduction of non-HDL (-18%) and Lp(a) (-25%), should be also taken into account. In spite of the positive results of the REVEAL Study, Merck decided not to proceed in asking regulatory approval for anacetrapib. Dalcetrapib (Dal-GenE study) and CKD-519 remain the two molecules within this area still in clinical development.

Assessing the mechanisms of cholesteryl ester transfer protein inhibitors

Cholesteryl ester transfer protein (CETP) inhibitors are a new class of therapeutics for dyslipidemia that simultaneously improve two major cardiovascular disease (CVD) risk factors: elevated low-density lipoprotein (LDL) cholesterol and decreased high-density lipoprotein (HDL) cholesterol. However, the detailed molecular mechanisms underlying their efficacy are poorly understood, as are any potential mechanistic differences among the drugs in this class. Herein, we used electron microscopy (EM) to investigate the effects of three of these agents (Torcetrapib, Dalcetrapib and Anacetrapib) on CETP structure, CETP-lipoprotein complex formation and CETP-mediated cholesteryl ester (CE) transfer. We found that although none of these inhibitors altered the structure of CETP or the conformation of CETP-lipoprotein binary complexes, all inhibitors, especially Torcetrapib and Anacetrapib, increased the binding ratios of the binary complexes (e.g., HDL-CETP and LDLCETP) and decreased the binding ratios of the HDL-CETP-LDL ternary complexes. The findings of more binary complexes and fewer ternary complexes reflect a new mechanism of inhibition: one distal end of CETP bound to the first lipoprotein would trigger a conformational change at the other distal end, thus resulting in a decreased binding ratio to the second lipoprotein and a degraded CE transfer rate among lipoproteins. Thus, we suggest a new inhibitor design that should decrease the formation of both binary and ternary complexes. Decreased concentrations of the binary complex may prevent the inhibitor was induced into cell by the tight binding of binary complexes during lipoprotein metabolism in the treatment of CVD.

HDL surface lipids mediate CETP binding as revealed by electron microscopy and molecular dynamics simulation

Cholesteryl ester transfer protein (CETP) mediates the transfer of cholesterol esters (CE) from atheroprotective high-density lipoproteins (HDL) to atherogenic low-density lipoproteins (LDL). CETP inhibition has been regarded as a promising strategy for increasing HDL levels and subsequently reducing the risk of cardiovascular diseases (CVD). Although the crystal structure of CETP is known, little is known regarding how CETP binds to HDL. Here, we investigated how various HDL-like particles interact with CETP by electron microscopy and molecular dynamics simulations. Results showed that CETP binds to HDL via hydrophobic interactions rather than protein-protein interactions. The HDL surface lipid curvature generates a hydrophobic environment, leading to CETP hydrophobic distal end interaction. This interaction is independent of other HDL components, such as apolipoproteins, cholesteryl esters and triglycerides. Thus, disrupting these hydrophobic interactions could be a new therapeutic strategy for attenuating the interaction of CETP with HDL.

Future of cholesteryl ester transfer protein (CETP) inhibitors: a pharmacological perspective

In almost 30 years since the introduction of HMG-CoA reductase inhibitors (statins), no other class of lipid modulators has entered the market. Elevation of high-density lipoprotein-cholesterol (HDL-C) via inhibiting cholesteryl ester transfer protein (CETP) is an attractive strategy for reducing the risk of cardiovascular events in high-risk patients. Transfer of triglyceride and cholesteryl ester (CE) between lipoproteins is mediated by CETP; thus inhibition of this pathway can increase the concentration of HDL-C. Torcetrapib was the first CETP inhibitor evaluated in phase III clinical trials. Because of off-target effects, torcetrapib raised blood pressure and increased the concentration of serum aldosterone, leading to higher cardiovascular events and mortality. Torcetrapib showed positive effects on cardiovascular risk especially in patients with a greater increase in HDL-C and apolipoprotein A-1 (apoA-1) levels. The phase III clinical trial of dalcetrapib, the second CETP inhibitor that has entered clinical development, was terminated because of ineffectiveness. Dalcetrapib is a CETP modulator that elevated HDL-C levels but did not reduce the concentration of low-density lipoprotein cholesterol (LDL-C). Both heterotypic and homotypic CE transfer between lipoproteins are mediated by some CETP inhibitors, including torcetrapib, anacetrapib, and evacetrapib, while dalcetrapib only affects the heterotypic CE transfer. Dalcetrapib has a chemical structure that is distinct from other CETP inhibitors, with a smaller molecular weight and a lack of trifluoride moieties. Moreover, dalcetrapib is a pro-drug that must be hydrolyzed to a pharmacologically active thiol form. Two other CETP inhibitors, anacetrapib and evacetrapib, are currently undergoing evaluation in phase III clinical trials. Both molecules have shown beneficial effects by increasing HDL-C and decreasing LDL-C concentration. The success of anacetrapib and evacetrapib remains to be confirmed upon the completion of phase III clinical trials in 2017 and 2015, respectively. Generally, the concentration of HDL-C has been considered a biomarker for the activity of CETP inhibitors. However, it is not clear whether a fundamental relationship exists between HDL-C levels and the risk of coronary artery diseases. The most crucial role for HDL is cholesterol efflux capacity in which HDL can reverse transport cholesterol from foam cells in atherosclerotic plaques. In view of the heterogeneity in HDL particle size, charge, and composition, the mere concentration of HDL-C may not be a good surrogate marker for HDL functionality. Recent clinical studies have reported that increased HDL functionality inversely correlates with the development of atherosclerotic plaque. Future development of CETP inhibitors may therefore benefit from the use of biomarkers of HDL functionality.

Cholesteryl ester transfer protein inhibitors for dyslipidemia: focus on dalcetrapib

Among the noteworthy recent stories in the management and prevention of atherosclerotic cardiovascular disease (CVD) is the saga of the development of pharmacological inhibitors of cholesteryl ester transfer protein (CETP). Inhibiting CETP significantly raises plasma concentrations of high-density lipoprotein cholesterol, which has long been considered a marker of reduced CVD risk. However, the first CETP inhibitor, torcetrapib, showed a surprising increase in CVD events, despite a dramatic increase in high-density lipoprotein cholesterol levels. This paradox was explained by putative off-target effects not related to CETP inhibition that were specific to torcetrapib. Subsequently, three newer CETP inhibitors, namely dalcetrapib, anacetrapib, and evacetrapib, were at various phases of clinical development in 2012. Each of these had encouraging biochemical efficacy and safety profiles. Dalcetrapib even had human arterial imaging results that tended to look favorable. However, the dalcetrapib development program was recently terminated, presumably because interim analysis of a large CVD outcome trial indicated no benefit. These events raise important questions regarding the validity of the mechanism of CETP inhibition and the broader issue of whether pharmacological raising of high-density lipoprotein cholesterol itself is a useful strategy for CVD risk reduction.

An update on the clinical development of dalcetrapib (RO4607381), a cholesteryl ester transfer protein modulator that increases HDL cholesterol levels

CETP is the target of CETP inhibitors such as anacetrapib and the modulator dalcetrapib. Both molecules have entered Phase III clinical trials, with the ultimate goal of reducing cardiovascular events by raising HDL cholesterol. At the 600-mg dose selected for the dal-OUTCOMES study, dalcetrapib is expected to inhibit CETP activity by approximately 30% and raise HDL-C by approximately 30% with limited effects on LDL cholesterol. Importantly, dalcetrapib does not raise blood pressure or aldosterone levels, two effects previously associated with the CETP inhibitor torcetrapib. Dalcetrapib has been well tolerated at the 600-mg dose. In the dal-PLAQUE atherosclerosis imaging study, dalcetrapib reduced the enlargement of total vessel area over time. In May 2012, following the results of the second interim analysis of dal-OUTCOMES, the Data and Safety Monitoring Board recommended stopping the study owing to a lack of clinically significant benefit, which was followed by Roche’s (Basel, Switzerland) decision to terminate the study and the dalcetrapib program (dal-HEART). Contrary to anacetrapib, a potent CETP inhibitor that markedly increases HDL cholesterol and significantly reduces LDL cholesterol, dalcetrapib has allowed us to test the hypothesis that an isolated, moderate elevation in HDL cholesterol prevents cardiovascular events.

Dalcetrapib , a cholesteryl ester transfer protein modulator

INTRODUCTION

Cholesteryl ester transfer protein (CETP) plays an important role in reverse cholesterol transport by transferring cholesteryl esters from high-density lipoprotein (HDL) to the apolipoprotein B-containing lipoproteins. Inhibition of CETP is a target to increase HDL-cholesterol and potentially reduce atherosclerosis. Dalcetrapib is an orally administered CETP inhibitor developed for the treatment of primary hypercholesterolaemia and mixed hyperlipidaemia.

AREAS COVERED

AREAS COVERED are: mode of action, preclinical development and clinical trials of dalcetrapib, a CETP modulator. The article provides an understanding of the pharmacokinetic and pharmacodynamic characteristics of dalcetrapib and insight into its clinical efficacy and safety. In clinical trials, dalcetrapib produced significant elevations in HDL-cholesterol when taken alone or in combination with statin with no effect on blood pressure or expression of genes involved in the renin-angiotensin-aldosterone system.

EXPERT OPINION

Although dalcetrapib is the least potent CETP inhibitor, it does not impair the formation of CETP-induced pre-β HDL, which might be needed to increase reverse cholesterol transport. While dalcetrapib is well-tolerated and does not show major side effects, the recent interim results of the Phase III dal-OUTCOMES trial have shown the lack of a clinically meaningful benefit, and further testing of the drug has been halted.

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.

Different effects of compounds decreasing cholesteryl ester transfer protein activity on lipoprotein metabolism

PURPOSE OF REVIEW

Review literature on the effect of decreasing cholesteryl ester transfer protein (CETP) activity through pharmacological inhibition or modulation in preclinical and clinical settings compared to human CETP deficiency on lipoprotein characteristics, HDL remodelling and function.

RECENT FINDINGS

Torcetrapib, anacetrapib and dalcetrapib inhibited the heterotypic transfer of cholesteryl ester from HDL to LDL and/or VLDL with similar potency, although the potency of dalcetrapib was time dependent. Homotypic transfer of cholesteryl ester from HDL3 to HDL2 via recombinant human CETP was inhibited by torcetrapib and anacetrapib (CETP inhibitors, CETPi) but not by dalcetrapib (CETP modulator, CETPm). In a hamster model of reverse cholesterol transport, only dalcetrapib increased efflux of fecal sterols from macrophages to feces. In clinical studies, dose-responses of CETPi and CETPm demonstrate qualitative and quantitative changes in HDL and LDL particle composition and distribution.

SUMMARY

Recent studies of the CETPi torcetrapib and anacetrapib and the CETPm dalcetrapib have shown differences in the resulting increase in HDL-cholesterol and in the level of HDL remodelling and potential for effective reverse cholesterol transport. Results from ongoing clinical outcomes studies with anacetrapib and dalcetrapib will clarify the relevance of CETP inhibition versus modulation towards HDL remodelling in the treatment of cardiovascular diseases.

Type 2 diabetes is associated with reduced ATP-binding cassette transporter A1 gene expression, protein and function

OBJECTIVE

Increasing plasma glucose levels are associated with increasing risk of vascular disease. We tested the hypothesis that there is a glycaemia-mediated impairment of reverse cholesterol transport (RCT). We studied the influence of plasma glucose on expression and function of a key mediator in RCT, the ATP binding cassette transporter-A1 (ABCA1) and expression of its regulators, liver X receptor-α (LXRα) and peroxisome proliferator-activated receptor-γ (PPARγ).

METHODS AND RESULTS

Leukocyte ABCA1, LXRα and PPARγ expression was measured by polymerase chain reaction in 63 men with varying degrees of glucose homeostasis. ABCA1 protein concentrations were measured in leukocytes. In a sub-group of 25 men, ABCA1 function was quantified as apolipoprotein-A1-mediated cholesterol efflux from 2-3 week cultured skin fibroblasts. Leukocyte ABCA1 expression correlated negatively with circulating HbA1c and glucose (rho = -0.41, p<0.001; rho = -0.34, p = 0.006 respectively) and was reduced in Type 2 diabetes (T2DM) (p = 0.03). Leukocyte ABCA1 protein was lower in T2DM (p = 0.03) and positively associated with plasma HDL cholesterol (HDL-C) (rho = 0.34, p = 0.02). Apolipoprotein-A1-mediated cholesterol efflux correlated negatively with fasting glucose (rho = -0.50, p = 0.01) and positively with HDL-C (rho = 0.41, p = 0.02). It was reduced in T2DM compared with controls (p = 0.04). These relationships were independent of LXRα and PPARγ expression.

CONCLUSIONS

ABCA1 expression and protein concentrations in leukocytes, as well as function in cultured skin fibroblasts, are reduced in T2DM. ABCA1 protein concentration and function are associated with HDL-C levels. These findings indicate a glycaemia-related, persistent disruption of a key component of RCT.