Posts Tagged ‘HDL’

Curator: Aviva Lev-Ari, PhD, RN


UPDATED on 7/29/2018


HDL-C: Is It Time to Stop Calling It the ‘Good’ Cholesterol? – Medscape – Jul 27, 2018.


In Eli Lilly’s Pipeline: DISCONTINUING Evacetrapib, a CETP inhibitor that’s meant to boost HDL

Reporter: Aviva Lev-Ari, PhD, RN


On April 3, 2012 we published

Fight against Atherosclerotic Cardiovascular Disease: A Biologics not a Small Molecule – Recombinant Human lecithin-cholesterol acyltransferase (rhLCAT) attracted AstraZeneca to acquire AlphaCore

ACP-501, a recombinant human lecithin-cholesterol acyltransferase (LCAT) enzyme.

LCAT, an enzyme in the bloodstream, is a key component in the reverse cholesterol transport (RCT) system, which is thought to play a major role in driving the removal of cholesterol from the body and may be critical in the management of high-density lipoprotein (HDL) cholesterol levels.  The LCAT enzyme could also play a role in a rare, hereditary disorder called familial LCAT deficiency (FLD) in which the LCAT enzyme is absent.

On April 4, 2013, the next day, a new study was published on a novel class of compounds, cholesteryl ester transfer protein (CETP) inhibitors, has demonstrated many potentially beneficial lipid-modifying effects was published on Anacetrapib, a compound that causes near-complete CETP inhibition, has among its effects, robust reductions in LDL-C and lipoprotein(a) as well as dramatic increases in HDL-C. The ability of anacetrapib to reduce coronary disease events is being tested in the Randomized EValuation of the Effects of Anacetrapib Through Lipid-modification (REVEAL) trial (NCT01252953).

Writer’s VIEWS:

    • AstraZeneca acquisition of AlphaCore represents its market entry into the CETP inhibitor segment via an acquisition where the company did not have presence or inhouse research. The results of the second study will position Merck at a superior position upon completion of Phase III Clinical Trials for Anacetrapib
    • If Biologics will help increase HDL in wide market penetration, the market share of Statins will be negatively impacted. Patent expiration and generic market availability of Statin erode future profits
    • Anacetrapib in in Phase III clinical Trial, if successfully completed — will be the FIRST biologics to use CETP inhibition biology of lipid metabolism in the quest to fight atherosclerosis by improving CVD outcomes
    • A connection between this two events and cites in Disclosure, AstraZeneca, Merck, supporting the research of Christopher P Cannon on the study on Anacetrapib.
    • Full Article PDF file was published in Research Reports in Clinical Cardiology, one of the Journals on Beall’s list publisher, where scientists pay to have the article been published, Dove Press, on its Web site says, “There are no limits on the number or size of the papers we can publish.” See reference for Beall’s list publishers

Study Goals:

  • testing the hypothesis that CETP inhibition may reduce atherosclerotic outcomes. 
  • answer important questions regarding the role of CETP in the biology of lipid metabolism and atherosclerosis.

Research Reports in Clinical Cardiology, 4 April 2013 Volume 2013:4 Pages 39 – 53

Dylan L Steen,1 Amit V Khera,2 Christopher P Cannon1

1TIMI Study Group, Cardiovascular Division, 2Department of Medicine, Brigham and Women’s Hospital, Boston, MA, USA


Dr Cannon is a member of the advisory boards of and has received grant support from Alnylam, Bristol-Myers Squibb, Pfizer, and CSL Behring; has received grant support from Accumetrics, AstraZeneca, Essentialis, GlaxoSmithKline, Merck, Regeneron, Sanofi, and Takeda; and is a clinical advisor to Automated Medical Systems. All other authors have reported that they have no relationships relevant to the contents of this paper.

Abstract: Despite major advances in cardiovascular care in recent decades, atherosclerotic cardiovascular disease remains the leading cause of morbidity and mortality worldwide. Statins have been shown to reduce cardiovascular events by 25%–40% in a dose-dependent fashion; yet additional therapies are needed to reduce vascular disease progression and acute thrombotic events. In addition to low-density lipoprotein cholesterol (LDL-C) reduction, other lipid risk factors, such as low high-density lipoprotein cholesterol (HDL-C), have created interest as therapeutic targets to lower cardiovascular risk. However, the absence of compelling data for incremental benefit of non-LDL-centric therapies in the statin era has limited their clinical use. A novel class of compounds, cholesteryl ester transfer protein (CETP) inhibitors, has demonstrated many potentially beneficial lipid-modifying effects. While in vitro and animal data for CETP inhibition have been encouraging, the initial enthusiasm for the class has been tempered by the failure of two CETP inhibitors (torcetrapib and dalcetrapib) in Phase III trials to reduce cardiovascular outcomes. Anacetrapib, a compound that causes near-complete CETP inhibition, has among its effects, robust reductions in LDL-C and lipoprotein(a) as well as dramatic increases in HDL-C. The ability of anacetrapib to reduce coronary disease events is being tested in the Randomized EValuation of the Effects of Anacetrapib Through Lipid-modification (REVEAL) trial (NCT01252953).

Keywords: anacetrapib, cholesteryl ester transfer protein, cholesteryl ester transfer protein inhibitor, atherosclerosis

  • Niacin, which augments HDL-C by 20%–25%, recently failed to lower atherosclerotic events in both the Atherothrombosis Intervention in Metabolic Syndrome with Low HDL/High Triglycerides and Impact on Global Health Outcomes (AIM-HIGH)6 and Treatment of HDL to Reduce the Incidence of Vascular Events (HPS2-THRIVE) trials.7,8
  • Lp(a) lowering has not yet been evaluated in randomized controlled trials, but observational and genetic (including Mendelian randomization) analyses have demonstrated an independent association of increased Lp(a) levels with increased CV events, suggesting Lp(a) lowering may confer benefit.9
  • surprising failure of the first two CETP inhibitors (torcetrapib and dalcetrapib) in Phase III outcomes trials has somewhat tempered this initial excitement and forced a re-evaluation of the complex effects of CETP inhibition on lipid metabolism and vascular biology.
  • Anacetrapib results in near-complete CETP inhibition with more pronounced lipid effects than its predecessors and is currently in a Phase III study for secondary prevention of coronary events. If successful it is likely that anacetrapib will also be considered for statin-intolerant patients and for primary prevention in patients who require LDL-C lowering beyond statin monotherapy
  • Human CETP is a 476-residue, 74 kDa, hydrophobic glycoprotein primarily secreted by the liver and adipose tissue.13 CETP was first cloned in 1987.14 The structure of CETP allows formation of a tunnel with the opening on one end interacting with HDL and the other with a very low-density lipoprotein (VLDL), intermediate-density lipoprotein (IDL), or LDL particle. The hydrophobic central cavity of this tunnel is large enough to allow transfer of neutral lipids (eg, cholesteryl esters [CEs], triglycerides [TGs]) from donor to acceptor particles, but conformational changes may occur to accommodate larger lipoprotein particles. The concave surface of CETP matches the curvature of the HDL particles to which it is primarily bound in the bloodstream.15,16
  • The overall effect of CETP is a net transfer of CE from HDL to these apolipoprotein B (apoB)-containing particles and TG to HDL and LDL
  • An important driver of the transfer of CE from HDL to apoB-containing particles is the production of CE from free cholesterol within HDL by lecithin acetyltransferase (LCAT).17

    The role of CETP in reverse cholesterol transport.

    Beginning in the peripheral tissues, free cholesterol is predominantly taken up by small “immature” HDL particles (eg, pre-β-HDL) via the ABCA1 transporter. Alternatively, it can be taken up by larger “mature” HDL particles (eg, HDL2) via the ABCG1 transporter. LCAT converts free cholesterol into cholesteryl ester, which is then shuttled to apoB-lipoproteins (eg, LDL, VLDL) in exchange for triglycerides. Only a minority of cholesteryl ester is delivered directly to the liver by HDL via the SR-BI; the majority is delivered indirectly to the liver by apoB-lipoproteins via the LDL recepter.

    Abbreviations: CETP, cholesteryl ester transfer protein; HDL, high-density lipoprotein; ABCA1, ATP-binding cassette transporter A1; ABCG1, ATP-binding cassette transporter G1; LCAT, lecithin acetyltransferase; apoB, apolipoprotein B; LDL, low-density lipoprotein; VLDL, very low density lipoprotein; SR-BI, scavenger receptor-BI; FC, free cholesterol; CE, cholesteryl ester.

  • One of the interesting questions in CETP deficiency is whether the HDL particles produced by potent CETP inhibition are functional. Regardless of whether reverse cholesterol transport is increased, the initial steps of cholesterol efflux from foam cells may be one of the key anti-atherogenic functions of HDL.5
  • This increased efflux is related to the very high content of LCAT and apoE in these large HDL particles, presumably driving net cholesterol efflux by promoting cholesterol esterification.36
  • effect of CETP deficiency on liver uptake of cholesteryl ester, an important downstream step in a reverse cholesterol transport. These studies suggest that there may be increased CE uptake via SR-BI as well as through a high affinity of large apoE-rich HDL for LDL receptors.20
  • meta-analysis established that three CETP genotypes were not only associated with decreased CETP activity and increased HDL but also with a lower risk of myocardial infarction (MI). For example, for each allele inherited, individuals with the TaqIB polymorphism had lower mean CETP activity (−8.6%), higher mean HDL-C (4.5%), higher mean apoA-I (2.4%), and an odds ratio for coronary disease of 0.95 (95% confidence intervals [CI], 0.92, 0.99). Similar associations were found for the other two CETP genotypes.40
  • Subsequent studies have confirmed that genetic variants leading to reduced CETP activity and its corresponding anti-atherogenic lipid profile are associated with reduced atherosclerotic outcomes.41–43
  • In ILLUSTRATE, an inverse association between HDL-C achieved and the primary endpoint of atheroma volume (r = −0.17, P , 0.001) was found. In addition, the highest quartile of HDL-C achieved (.86 mg/dL) demonstrated atheroma regression, suggesting that there may be a “threshold effect” to HDL-C elevation.68
  • Other CETP inhibitors:

was developed by Hoffmann–La Roche until May 2012. It did not raise blood pressure and did raise HDL, but it showed no clinically meaningful efficacy.


is under development by Eli Lilly & Company.
was developed by Pfizer until December 2006 but caused unacceptable increases in blood pressure and had net cardiovascular detriment.
Anacetrapib At the 16th International Symposium on Drugs Affecting Lipid Metabolism (New York, Oct 4-7, 2007), Merck reported on a Phase IIb study. The eight week study reported dosage correlated reduction in LDL-C and increases in HDL-C levels with no corresponding increases in blood pressure in any cohort. The increase in HDL was particularly significant, averaging 44 percent, 86 percent, 139 percent and 133 percent at doses of 10 mg, 40 mg, 150 mg and 300 mg. Merck performed a dose-ranging study of anacetrapib, with the results presented in 2009.


Anacetrapib is a 3,5-bis-trifluoromethyl-benzene derivative with similar binding properties to CETP as torcetrapib. The compound was developed when it was found that a substitution modification of the oxazolidinone ring increased its potency for CETP inhibition in a transgenic mouse model.85 In terms of its pharmacokinetics and pharmacodynamics, anacetrapib is rapidly absorbed with a time-to-peak plasma concentration of about 4 hours. The oral bioavailability of anacetrapib is poor, with only about 20% being absorbed; however at this exposure, LDL-C is reduced up to 40% and HDL-C increased up to 140%. It is recommended that anacetrapib be taken with food (ie, low-fat diet) to increase drug exposure (and efficacy) as well as compliance.86

Anacetrapib is highly protein bound (eg, CETP) in the plasma (.99.5%). It is cleared by oxidative metabolism via Cytochrome P450 3A4 (CYP3A4) with excretion of the metabolites via the biliary/fecal route. Only a trace amount is eliminated by urinary excretion.87 Importantly, while anacetrapib is a sensitive CYP3A4 substrate, anacetrapib neither inhibits nor induces CYP3A4 activity. No meaningful interactions have been found between anacetrapib and simvastatin, digoxin, or warfarin.86 Anacetrapib in part to its redistribution to adipose tissue has a long terminal half-life.88

In terms of safety endpoints, anacetrapib demonstrated no increase in side effects (including myalgia), drug-related adverse effects, adverse events leading to drug discontinuation, or other important safety endpoints, such as BP, electrolyte, aldosterone, creatinine kinase, or transaminase levels. A very small increase in C-reactive protein of undetermined significance was seen with anacetrapib, which notably was also reported with torcetrapib and dalcetrapib in their Phase III studies. It is unknown whether this is a class effect as the small sample size in the evacetrapib Phase II study limits evaluation of small C-reactive protein changes.

It is expected that the REVEAL (the Phase III) population will also have lower starting LDL-C levels, both because statin-intolerant subjects will not be enrolled and because of more stringent lipid entry criteria. The final major difference is that the primary endpoint in REVEAL is focused on coronary events, while ACCELERATE has a broader primary endpoint. A broader primary endpoint along with a slightly higher risk population will allow for a shorter follow-up duration and much smaller sample size in ACCELERATE.


  • CETP remains a valid target and that the lipid changes resulting from its inhibition may be protective. The biology of CETP inhibition is complex, and questions remain regarding which lipid changes (eg, reductions in LDL and Lp(a), increases in HDL) are most likely to be important and whether there are still unknown effects that may negate any overall clinical benefit.
  • if potent CETP inhibition is found to be beneficial, it is still unclear whether this effect will be homogeneous or vary based on individual metabolism.
  • anacetrapib-induced HDL (especially the apoE-rich HDL2 particles) may have an enhanced ability for reverse cholesterol transport without any known adverse effects. Importantly, if a threshold effect for HDL-C augmentation exists, the vast majority of patients taking anacetrapib would be expected to cross it.
  • Despite a difficult beginning for the class of CETP inhibitors, anacetrapib and evacetrapib hold promise as future therapies for patients with atherosclerosis

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submit your manuscript | Dovepress Dovepress 51 Anacetrapib for coronary heart disease Research Reports in Clinical Cardiology 2013:4

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Curator: Aviva Lev-Ari, PhD, RN

Evidence of HDL Modulation of eNOS in Humans

 Whereas the functional link between HDL and eNOS has been appreciated only recently, the relationship between HDL and endothelium-dependent vasodilation has been known for some time. In studies of coronary vasomotor responses to acetylcholine, it was noted in 1994 that patients with elevated HDL have greater vasodilator and attenuated vasoconstrictor responses (Zeiher et al., 1994).

Circulation, 89:2525–2532.

Studies of flow-mediated vasodilation of the brachial artery have also shown that HDL cholesterol is an independent predictor of endothelial function (Li et al., 2000).

Int. J. Cardiol., 73:231–236

Induction of NO Production and Stimulation of eNOS

Mechanism of Action (MOA) for Nitric Oxide (NO) and endothelial Nitric Oxide Syntase (eNOS) are described in George T. and P. Ramwell, (2004). Nitric Oxide, Donors, & Inhibitors. Chapter 19 in Katzung, BG., Basic & Clinical Pharmacology. McGraw-Hill, 9th Edition, pp. 313 – 318

The direct, short-term impact of HDL on endothelial function also has recently been investigated in humans. One particularly elegant study recently evaluated forearm blood flow responses in individuals who are heterozygous for a loss-of-function mutation in the ATP-binding cassette transporter 1 (ABCA1) gene. Compared with controls, ABCA1 heterozygotes (six men and three women) had HDL levels that were decreased by 60%, their blood flow responses to endothelium-dependent vasodilators were blunted, and endothelium-independent responses were unaltered. After a 4-hour infusion of apoAI/phosphatidylcholine disks, their HDL level increased threefold and endothelium-dependent vasomotor responses were fully restored (Bisoendial et al., 2003). It has also been observed that endothelial function is normalized in hypercholesterolemic men with normal HDL levels shortly following the administration of apoAI/phosphatidylcholine particles (Spieker et al., 2002).

Circulation, 105:1399–1402.

Thus, evidence is now accumulating that HDL is a robust positive modulator of endothelial NO production in humans (Shaul & Mineo, 2004).

J Clin Invest., 15; 113(4): 509–513.

HDL is more than an eNOS Agonist

 In addition to the modulation of NO production by signaling events that rapidly dictate the level of enzymatic activity, important control of eNOS involves changes in the abundance of the enzyme. In a clinical trial by the Karas laboratory of niacin therapy in patients with low HDL levels (nine males and two females), flow-mediated dilation of the brachial artery was improved in association with a rise in HDL of 33% over 3 months (Kuvin et al., 2002).

Am. Heart J., 144:165–172.

They also demonstrated that eNOS expression in cultured human endothelial cells is increased by HDL exposure for 24 hours. They further showed that the increase in eNOS is related to an increase in the half-life of the protein, and that this is mediated by PI3K–Akt kinase and MAPK (Ramet et al., 2003).

J. Am. Coll. Cardiol., 41:2288–2297.

Thus, the same mechanisms that underlie the acute activation of eNOS by HDL appear to be operative in upregulating the expression of the enzyme.

The current understanding of the mechanism by which HDL enhances endothelial NO production is summarized in Shaul & Mineo (2004), Figure 1.

J Clin Invest., 15; 113(4): 509–513.

It describes the mechanism of action for HDL enhancement of NO production by eNOS in vascular endothelium.

(a)   HDL causes membrane-initiated signaling, which stimulates eNOS activity. The eNOS protein is localized in cholesterol-enriched (orange circles) plasma membrane caveolae as a result of the myristoylation and palmitoylation of the protein. Binding of HDL to SR-BI via apoAI causes rapid activation of the nonreceptor tyrosine kinase src, leading to PI3K activation and downstream activation of Akt kinase and MAPK. Akt enhances eNOS activity by phosphorylation, and independent MAPK-mediated processes are additionally required (Duarte, et al., 1997). .Eur J Pharmacol, 338:25–33. HDL also causes an increase in intracellular Ca2+ concentration (intracellular Ca2+ store shown in blue; Ca2+ channel shown in pink), which enhances binding of calmodulin (CM) to eNOS. HDL-induced signaling is mediated at least partially by the HDL-associated lysophospholipids SPC, S1P, and LSF acting through the G protein–coupled lysophospholipid receptor S1P3. HDL-associated estradiol (E2) may also activate signaling by binding to plasma membrane–associated estrogen receptors (ERs), which are also G protein coupled. It remains to be determined if signaling events are also directly mediated by SR-BI (Yuhanna et al., 2001), (Nofer et al., 2004), (Gong et al., 2003), (Mineo et al., 2003).

Nat. Med.7:853–857.

J. Clin. Invest.,113:569–581.

J. Clin. Invest., 111:1579–1587.

J. Biol. Chem., 278:9142–9149.

(b)   HDL regulates eNOS abundance and subcellular distribution. In addition to modulating the acute response, the activation of the PI3K–Akt kinase pathway and MAPK by HDL upregulates eNOS expression (open arrows). HDL also regulates the lipid environment in caveolae (dashed arrows). Oxidized LDL (OxLDL) can serve as a cholesterol acceptor (orange circles), thereby disrupting caveolae and eNOS function. However, in the presence of OxLDL, HDL maintains the total cholesterol content of caveolae by the provision of cholesterol ester (blue circles), resulting in preservation of the eNOS signaling module (Ramet et al., 2003), (Blair et al., 1999), (Uittenbogaard et al., 2000).

J. Am. Coll. Cardiol., 41:2288–2297.

J. Biol. Chem., 274:32512–32519.

J. Biol. Chem., 275:11278–11283.

Source for HDL-eNOS Figure: Shaul & Mineo (2004).


HDL enhances NO production by eNOS in vascular endothelium.


Shaul, PW and Mineo, C, (2004). HDL action on the vascular wall: is the answer NO? J Clin Invest., 15; 113(4): 509–513.

eNOS is not Activated by Nebivolol in Human Failing Myocardium.

Nebivolol is a highly selective beta(1)-adrenoceptor blocker with additional vasodilatory properties, which may be due to an endothelial-dependent beta(3)-adrenergic activation of the endothelial nitric oxide synthase (eNOS). beta(3)-adrenergic eNOS activation has been described in human myocardium and is increased in human heart failure. Therefore, this study investigated whether nebivolol may induce an eNOS activation in cardiac tissue. Immunohistochemical stainings were performed using specific antibodies against eNOS translocation and eNOS serine(1177) phosphorylation in rat isolated cardiomyocytes, human right atrial tissue (coronary bypass-operation), left ventricular non-failing (donor hearts) and failing myocardium after application of the beta-adrenoceptor blockers nebivolol, metoprolol and carvedilol, as well as after application of BRL 37344, a specific beta(3)-adrenoceptor agonist. BRL 37344 (10 muM) significantly increased eNOS activity in all investigated tissues (either via translocation or phosphorylation or both). None of the beta-blockers (each 10 muM), including nebivolol, increased either translocation or phosphorylation in any of the investigated tissues. In human failing myocardium, nebivolol (10 muM) decreased eNOS activity. In conclusion, nebivolol shows a tissue-specific eNOS activation. Nebivolol does not activate the endothelial eNOS in end-stage human heart failure and may thus reduce inhibitory effects of NO on myocardial contractility and on oxidative stress formation. This mode of action may be of advantage when treating heart failure patients.

Brixius K, Song Q, Malick A, Boelck B, Addicks K, Bloch W, Mehlhorn U, Schwinger R, (2006). eNOS is not activated by nebivolol in human failing myocardium.

Life Sci. 2006 Apr 25


Brixius K, Song Q, Malick A, Boelck B, Addicks K, Bloch W, Mehlhorn U, Schwinger R, (2006). eNOS is not activated by nebivolol in human failing myocardium.

Life Sci. 2006 Apr 25

Mineo C, Yuhanna IS, Quon MJ, Shaul PW., (2003). HDL-induced eNOS activation is mediated by Akt and MAP kinases. J. Biol. Chem., 278:9142–9149.

Shaul, PW and Mineo, C, (2004). HDL action on the vascular wall: is the answer NO? J Clin Invest., 15; 113(4): 509–513.

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