The Effect of Darapladib on Plasma Lipoprotein-Associated Phospholipase A2 Activity and Cardiovascular Biomarkers in Patients With Stable Coronary Heart Disease or Coronary Heart Disease Risk Equivalent

Antioxidant and inflammatory aspects of lipoprotein-associated phospholipase A₂ (Lp-PLA₂): a review

The association of cardiovascular events with Lp-PLA₂ has been studied continuously today. The enzyme has been strongly associated with several cardiovascular risk markers and events. Its discovery was directly related to the hydrolysis of the platelet-activating factor and oxidized phospholipids, which are considered protective functions. However, the hydrolysis of bioactive lipids generates lysophospholipids, compounds that have a pro-inflammatory function. Therefore, the evaluation of the distribution of Lp-PLA₂ in the lipid fractions emphasized the dual role of the enzyme in the inflammatory process, since the HDL-Lp-PLA₂ enzyme contributes to the reduction of atherosclerosis, while LDL-Lp-PLA₂ stimulates this process. Recently, it has been verified that diet components and drugs can influence the enzyme activity and concentration. Thus, the effects of these treatments on Lp-PLA₂ may represent a new kind of prevention of cardiovascular disease. Therefore, the association of the enzyme with the traditional assessment of cardiovascular risk may help to predict more accurately these diseases.

Inhibition of lipoprotein-associated phospholipase A2 ameliorates inflammation and decreases atherosclerotic plaque formation in ApoE-deficient mice

BACKGROUND

Lipoprotein-associated phospholipase A2 (Lp-PLA2) is thought to play modulatory roles in the development of atherosclerosis. Here we evaluated the effects of a specific lp-PLA2 inhibitor on atherosclerosis in ApoE-deficient mice and its associated mechanisms.

METHODOLOGY/PRINCIPAL FINDINGS

ApoE-deficient mice fed an atherogenic high-fat diet for 17 weeks were divided into two groups. One group was administered the specific lp-PLA2 inhibitor, darapladib (50 mg/kg/day; p.o.) daily for 6 weeks, while the control group was administered saline. We observed no differences in body weight and serum lipids levels between the two groups at the end of the dietary period. Notably, serum lp-PLA2 activity as well as hs-CRP (C-reactive protein) and IL-6 (Interleukin-6) levels were significantly reduced in the darapladib group, compared with the vehicle group, while the serum PAF (platelet-activating factor) levels were similar between the two groups. Furthermore, the plaque area through the arch to the abdominal aorta was reduced in the darapladib group. Another finding of interest was that the macrophage content was decreased while collagen content was increased in atherosclerotic lesions at the aortic sinus in the darapladib group, compared with the vehicle group. Finally, quantitative RT-PCR performed to determine the expression patterns of specific inflammatory genes at atherosclerotic aortas revealed lower expression of MCP-1, VCAM-1 and TNF-α in the darapladib group.

CONCLUSIONS/SIGNIFICANCE

Inhibition of lp-PLA2 by darapladib leads to attenuation of in vivo inflammation and decreased plaque formation in ApoE-deficient mice, supporting an anti-atherogenic role during the progression of atherosclerosis.

Editorial: why inhibition of lipoprotein-associated phospholipase A2 has the potential to improve patient outcomes

PURPOSE OF REVIEW

Lipoprotein-associated phospholipase A2 (Lp-PLA2) is a risk factor as strong as low-density lipoprotein (LDL) cholesterol. Therapies targeting Lp-PLA2 in plasma and plaque are now being developed. This article will review these data.

RECENT FINDINGS

Lp-PLA2 is intimately involved in the development of atherosclerosis and is found in vulnerable human plaques. Multiple epidemiological studies have shown that Lp-PLA2 is related to the occurrence of myocardial infarction (MI), stroke and vascular death.Darapladib is a novel oral compound that selectively inhibits Lp-PLA2 in plasma and in human plaques. Darapladib has also been shown to halt necrotic core progression in coronary arteries over a 12-month period and to have few adverse effects.

SUMMARY

Two large phase III trials are randomizing 26,000 patients to darapladib or placebo with chronic coronary heart disease or following an acute coronary syndrome. The primary composite outcomes are cardiovascular death, MI or stroke and results should be available in 2012. Darapladib has the potential to improve patient outcomes in addition to evidence-based treatments by modulating mechanisms of disease that have not been addressed by current therapies.

Relationship between cardiovascular risk factors and biomarkers with necrotic core and atheroma size: a serial intravascular ultrasound radiofrequency data analysis

We explored the impact of patient demographics, anthropometric measurements, cardiovascular risk factors, and soluble biomarkers on necrotic core and atheroma size in patients with coronary disease. The IBIS-2 trial enrolled 330 patients. In the multivariate analysis, at baseline, creatinine had a positive, whereas baseline mean lumen diameter and myeloperoxidase had a negative, independent association with percentage of necrotic core (PNC); while age, glomerular filtration rate <60, HbA1c, previous PCI or CABG and baseline % diameter stenosis were positively, and acute coronary syndromes (ACS) were negatively associated with baseline percentage atheroma volume (PAV). The variables associated with a decrease in PNC from baseline were darapladib, ACS and a large content of NC at baseline, while variables associated with an increase in PNC were previous stroke and % diameter stenosis at baseline. Those variables associated with a decrease in PAV from baseline were waist circumference, statin use, CD40L and baseline PAV, while the only variable associated with an increase in PAV was baseline diastolic blood pressure. Treatment with darapladib was associated with a decrease in necrotic core, but was not associated with a decrease in percentage atheroma volume. On the contrary, statin use was only associated with a decrease in percentage atheroma volume.

Peripheral artery disease, biomarkers, and darapladib

OBJECTIVE

Subjects with peripheral artery disease (PAD) are at increased risk of cardiovascular morbidity and mortality, perhaps in part, related to increased levels of inflammation, platelet activity, and lipids. We therefore sought to investigate the relationship between PAD and levels of inflammatory, platelet, and lipid biomarkers and the treatment effect of darapladib, a novel lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) inhibitor.

METHODS

This is a post hoc analysis of the 959 patients with coronary disease or their risk equivalent receiving atorvastatin who were randomized to receive darapladib or placebo to examine the effects of an Lp-PLA(2) inhibitor on the biomarkers of cardiovascular risk. We conducted an exploratory analysis evaluating the levels of biomarkers in subjects with PAD (n = 172) compared with those without PAD (n = 787).

RESULTS

After adjustment for age, sex, smoking, body mass index, and diabetes, subjects with PAD had greater levels of matrix metalloproteinase-9 (between group comparisons 22%, 95% confidence interval [10-31], P < .01), myeloperoxidase (12% [2-20], P = .01), interleukin-6 (13% [4-21], P = .01), adiponectin (17% [7-26], P < .01), intercellular adhesion molecule-1 (7% [2-11], P < .01), osteoprotegrin (6% [1-10], P = .02), CD40 ligand (15% [1-28], P = .04), high-sensitivity C-reactive protein (17% [1-31], P = .04), and triglycerides (11% [0.2-21], P = .05). No significant difference was detected for Lp-PLA(2) activity, P-selectin, urinary 11-dehydrothroboxane B2, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol between subjects with and without PAD. Darapladib produced highly significant inhibition of Lp-PLA(2) activity when compared with placebo at weeks 4 and 12 (P < .01) in patients with and without PAD.

CONCLUSIONS

Subjects with PAD had elevated levels of matrix metalloproteinase-9, myeloperoxidase, interleukin-6, adiponectin, intercellular adhesion molecule-1, osteoprotegrin, CD40 ligand, high-sensitivity C-reactive protein, and triglycerides compared with those without PAD. Darapladib, a novel Lp-PLA(2) inhibitor, was equally effective in reducing Lp-PLA(2) activity levels in subjects with and without PAD.

Lipoprotein associated phospholipase A(2): role in atherosclerosis and utility as a biomarker for cardiovascular risk

Atherosclerosis and its clinical manifestations are widely prevalent throughout the world. Atherogenesis is highly complex and modulated by numerous genetic and environmental risk factors. A large body of basic scientific and clinical research supports the conclusion that inflammation plays a significant role in atherogenesis along the entire continuum of its progression. Inflammation adversely impacts intravascular lipid handling and metabolism, resulting in the development of macrophage foam cell, fatty streak, and atheromatous plaque formation. Given the enormous human and economic cost of myocardial infarction, ischemic stroke, peripheral arterial disease and amputation, and premature death and disability, considerable effort is being committed to refining our ability to correctly identify patients at heightened risk for atherosclerotic vascular disease and acute cardiovascular events so that they can be treated earlier and more aggressively. Serum markers of inflammation have emerged as an important component of risk factor burden. Lipoprotein-associated phospholipase A2 (Lp-PLA(2)) potentiates intravascular inflammation and atherosclerosis. A variety of epidemiologic studies support the utility of Lp-PLA(2) measurements for estimating and further refining cardiovascular disease risk. Drug therapies to inhibit Lp-PLA(2) are in development and show considerable promise, including darapladib, a specific molecular inhibitor of the enzyme. In addition to substantially inhibiting Lp-PLA(2) activity, darapladib reduces progression of the necrotic core volume of human coronary artery atheromatous plaque. The growing body of evidence points to an important role and utility for Lp-PLA(2) testing in preventive and personalized clinical medicine.

Inflammatory markers in coronary heart disease

INTRODUCTION

Inflammation plays a key role in the development of atherosclerosis and coronary heart disease (CHD).

SOURCES OF DATA

Peer-reviewed studies published in English-language journals were reviewed with a focus on C-reactive protein (CRP) and lipoprotein-associated phospholipase A(2) (Lp-PLA2).

AREAS OF AGREEMENT

Elevated levels of serum CRP and Lp-PLA2 are associated with an increased risk of incident CHD events in both primary and secondary prevention studies across a wide range of age, gender and ethnic groups.

AREAS OF CONTROVERSY

The utility of inflammatory markers in predicting CHD risk when added to traditional risk factors is under debate. They are most useful in subjects in the intermediate-risk category.

GROWING POINTS

Treatment with a statin in subjects with elevated CRP but without hyperlipidemia can reduce the risk of CHD.

AREAS TIMELY FOR DEVELOPING RESEARCH

Extensive research is under way to identify additional novel serum markers with higher specificity for coronary artery plaque inflammation. Specific inhibitors against vascular inflammation in combination with medications to lower low-density lipoprotein cholesterol, i.e. statins, may help prevent cardiovascular events in the future.

Lp-PLA₂- a novel risk factor for high-risk coronary and carotid artery disease

Lipoprotein-associated phospholipase A2 (Lp-PLA₂) is at the crossroads of lipid metabolism and the inflammatory response. It is produced by inflammatory cells, bound to LDL and other lipoproteins, and once in the arterial wall facilitates hydrolysis of phospholipids. Elevated serum levels of Lp-PLA₂ have been associated with increased cardiovascular risk in healthy populations and in patients with known vascular disease. Here, we review the role of Lp-PLA₂ in the development of atherosclerosis and progression to unstable disease, the utility of Lp-PLA₂ as a risk predictor for coronary and carotid events and the potential clinical benefit of pharmacologic inhibition of Lp-PLA₂.

Phospholipase A2 inhibition and atherosclerotic vascular disease: prospects for targeting secretory and lipoprotein-associated phospholipase A2 enzymes

PURPOSE OF REVIEW

Selective inhibitors of secretory phospholipase A2 and lipoprotein-associated phospholipase A2 are potential candidates for reducing recurrent cardiovascular events in patients with established coronary heart disease (CHD). With the active enrollment of CHD patients into phase III clinical trials with both classes of inhibitors, this article reviews the available experimental animal and human trial evidence that provides the rationale for the development of the phospholipase A2 inhibitors varespladib methyl and darapladib as preventive therapy.

RECENT FINDINGS

Recently completed experimental animal studies, human biomarker data, and vascular imaging studies provide support for proceeding with clinical outcome trials secretory phospholipase A2 and lipoprotein-associated phospholipase A2 inhibition.

SUMMARY

Both secretory phospholipase A2 and lipoprotein-associated phospholipase A2 inhibitors hold promise for the reduction of recurrent cardiovascular events in patients treated with current standards of care. The completion of the ongoing clinical event trials has the potential to provide a new dimension to secondary preventive therapy.

Lysophosphatidylcholine is generated by spontaneous deacylation of oxidized phospholipids

Elevated levels of lysophosphatidylcholine (lysoPC), present in oxidatively damaged low-density lipoprotein (oxLDL), are implicated in cardiovascular complications. LysoPC is generated by free radical-catalyzed oxidation of polyunsaturated PCs to oxidatively truncated phosphophatidylcholines (oxPCs). It is known that oxPCs are especially susceptible to hydrolysis by platelet-activating factor acetylhydrolase, a phospholipase (PL) A(2) that exists in plasma largely in association with LDL. Drugs that aim to prevent the generation of lysoPC by inhibiting this PLA(2)-catalyzed hydrolysis are in advanced clinical trials. We now report that spontaneous deacylation oxPCs, such as 1-palmityl-2-(4-hydroxy-7-oxo-5-heptenoyl)-sn-glycero-3-phosphocholine, occurs readily under physiological conditions of temperature and pH (t(1/2) = 30 min at 37 °C and pH 7.4). We also show that this reaction proceeds through an intramolecular transesterification mechanism. Because antiphospholipase drugs cannot block this nonenzymatic pathway to lysoPC, additional therapeutic measures may be needed to avoid the pathological consequences of the newly discovered biomolecular chemistry of oxPCs.

Effects of varespladib methyl on biomarkers and major cardiovascular events in acute coronary syndrome patients

OBJECTIVES

The purpose of this study was to investigate the effects of varespladib on cardiovascular biomarkers in acute coronary syndrome patients.

BACKGROUND

Secretory phospholipase A(2) (sPLA(2)) represents a family of proatherogenic enzymes that hydrolyze lipoprotein phospholipids, increasing their affinity for intimal proteoglycans; contribute to cholesterol loading of macrophages by nonscavenger receptor mediated pathways; and activate inflammatory pathways. In prospective studies, high sPLA(2)-IIA levels predicted major adverse cardiovascular events in acute coronary syndrome (ACS) and stable coronary heart disease patients.

METHODS

This randomized, double-blind, prospective controlled clinical trial (phase 2B) was designed to investigate the effects of sPLA(2) inhibition with varespladib 500 mg daily versus placebo as adjunctive therapy to atorvastatin 80 mg daily on biomarkers (low-density lipoprotein cholesterol [LDL-C], high-sensitivity C-reactive protein [hsCRP], and sPLA(2)-IIA levels), major adverse cardiovascular events (unstable angina, myocardial infarction, death), and safety. In all, 625 ACS subjects were randomized within 96 h of the index event and treated for a minimum of 6 months.

RESULTS

After 8 weeks (primary efficacy end point), varespladib/atorvastatin reduced mean LDL-C levels from baseline by 49.6% compared with 43.4% with placebo/atorvastatin (p = 0.002). Respective 8-week median reductions in sPLA(2)-IIA levels were 82.4% and 15.6% (p < 0.0001), and hsCRP levels were lowered by 75.0% and 71.0% (p = 0.097). At 24 weeks, respective reductions with varespladib and placebo were as follows: LDL-C 43.5% versus 37.6% (p < 0.05), hsCRP 79.8% versus 77.0% (p = 0.02), and sPLA(2)-IIA 78.5% versus 6.4% (p < 0.0001). Major adverse cardiovascular events were not different from placebo 6 months post-randomization (7.3% varespladib vs. 7.7% placebo). No treatment differences in elevated liver function studies on >1 occasion were observed.

CONCLUSIONS

Varespladib therapy effectively reduced LDL-C and inflammatory biomarkers in ACS patients treated with conventional therapy including atorvastatin 80 mg daily. There were no treatment differences in clinical cardiovascular events. (FRANCIS [Fewer Recurrent Acute Coronary Events With Near-Term Cardiovascular Inflammation Suppression]-ACS Trial: A Study of the Safety and Efficacy of A 002 in Subjects With Acute Coronary Syndromes; NCT00743925).

Recent developments with lipoprotein-associated phospholipase A2 inhibitors

Lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) is a calcium-independent phospholipase A(2) enzyme secreted by leukocytes and associated with circulating low-density lipoprotein and macrophages in atherosclerotic plaques. Until recently, the biological role of Lp-PLA(2) in atherosclerosis was controversial, but now the preponderance of evidence demonstrates a proatherogenic role of this enzyme. Lp-PLA(2) generates two proinflammatory mediators, lysophosphatidylcholine and oxidized nonesterified fatty acids, which play a major role in the development of atherosclerotic lesions and formation of a necrotic core, leading to more vulnerable plaques. These findings have opened the door to a potential novel therapeutic target, selective inhibition of Lp-LPA(2). Recently, both animal models and human studies have shown that selective inhibition of Lp-PLA(2) reduces plasma Lp-PLA(2) activity, plaque area, and necrotic core area. This article reviews the most recent developments with Lp-PLA(2) inhibitors.

Lipoprotein-associated phospholipase A₂ activity and mass in relation to vascular disease and nonvascular mortality

OBJECTIVES

To assess whether associations of circulating lipoprotein-associated phospholipase A₂ (Lp-PLA₂) with vascular disease are independent of other risk factors.

METHODS

Lp-PLA₂ activity and mass, lipids and other characteristics were measured at baseline in 19,037 individuals at high risk of vascular disease in a randomized trial of simvastatin with 5-year average follow-up.

RESULTS

Lp-PLA₂ activity and mass were correlated with each other (r = 0.56), lipids and other vascular risk factors. The moderate association of Lp-PLA₂ activity with occlusive coronary events (n = 2531) in analyses adjusted for nonlipid factors (hazard ratio per 1 SD [HR] 1.11, 95% CI 1.06-1.15) became nonsignificant after further adjustment for apolipoproteins (HR 1.02, 0.97-1.06). Such adjustment also attenuated HRs with Lp-PLA₂ mass from 1.08 (1.03-1.12) to 1.05 (1.01-1.09). By contrast, the HR with apolipoprotein-B100 of 1.15 (1.10-1.19) was only slightly attenuated to 1.14 (1.09-1.19) after further adjustment for apolipoprotein A₁ and Lp-PLA₂. Age- and sex-adjusted HRs for other cardiac events (n = 1007) with either Lp-PLA₂ activity or mass were about 1.20, but HRs reduced after adjustment for nonlipid factors (activity: 1.11, 1.04-1.18; mass: 1.08, 1.02-1.15). Adjusted HRs for ischaemic stroke (n = 900) were weak and nonsignificant and for nonvascular mortality (n = 1040) were 1.01 (0.94-1.09) with activity and 1.12 (1.05-1.19) with mass. Simvastatin reduced Lp-PLA₂ levels by about one-quarter, but simvastatin's vascular protection did not vary with baseline Lp-PLA₂ concentration.

CONCLUSIONS

Associations of Lp-PLA₂ with occlusive coronary events depend considerably on lipid levels, whereas those with other cardiac events appear to reflect confounding from cardiovascular medication and prior vascular disease.

Lipoprotein-associated phospholipase A2 as a biomarker of coronary heart disease and a therapeutic target

PURPOSE OF REVIEW

Lipoprotein-associated phospholipase A2 (Lp PLA2) is postulated to occupy a key position in the pathogenic sequence leading to formation of complex atherosclerotic lesions. This study reviews evidence supporting its role as a biomarker of vascular disease and as a possible therapeutic target.

RECENT FINDINGS

Evidence continues to build supporting the usefulness of Lp PLA2 as a predictor of coronary events in the general population and in those with established coronary heart disease. Elevated Lp PLA2 is also associated with stroke and heart failure. The crystal structure of Lp PLA2 is now available and offers insight into the links between structure, function and atherogenic properties. Recently completed studies on the efficacy of darapladib, a specific Lp PLA2 inhibitor, show beneficial changes in plaque morphology in animal models and in humans.

SUMMARY

Lp PLA2 is gaining acceptance as a useful biomarker of chronic inflammation and as a predictor of vascular disease. Early results with darapladib offer promise, but not definitive proof, of a potential role for Lp PLA2 inhibition in coronary heart disease prevention.

Darapladib: an emerging therapy for atherosclerosis

Despite a reduction in cardiovascular risk conferred by therapies that modify circulating lipids, a need remains for novel treatments to further decrease the occurrence of complications of atherosclerotic cardiovascular diseases. Lipoprotein-associated phospholipase-A2 is an important regulator of lipid metabolism and inflammation that circulates with lipoprotein particles and is carried into the arterial wall with low-density lipoprotein particles during the progression of atherosclerosis. Within the vessel wall, lipoprotein-associated phospholipase-A2 releases small molecules that stimulate macrophage recruitment and evolution to foam cells, leading to plaque vulnerability. Epidemiologic studies demonstrate that elevated circulating levels of lipoprotein-associated phospholipase-A2 predict an increased risk of myocardial infarction and stroke, whereas histologic examination of diseased human coronary arteries reveals intense presence of the enzyme in atherosclerotic plaques that are prone to rupture. These considerations suggest lipoprotein-associated phospholipase-A2 as a promising therapeutic target, and a specific inhibitor, darapladib, has been under development for this application. This review summarizes the completed preclinical and early phase clinical studies that underlie two recently commenced phase III clinical trials that will investigate the efficacy and safety of darapladib in nearly 13,000 individuals with coronary heart disease. When completed, these trials should provide important insights into the utility of darapladib to reduce myocardial infarction, stroke and cardiovascular death.

Association of carotid plaque Lp-PLA(2) with macrophages and Chlamydia pneumoniae infection among patients at risk for stroke

Background

We previously showed that the burden of Chlamydia pneumoniae in carotid plaques was significantly associated with plaque interleukin (IL)-6, and serum IL-6 and C-reactive protein (CRP), suggesting that infected plaques contribute to systemic inflammatory markers in patients with stroke risk. Since lipoprotein-associated phospholipase A2 (Lp-PLA₂) mediates inflammation in atherosclerosis, we hypothesized that serum Lp-PLA₂ mass and activity levels and plaque Lp-PLA₂ may be influenced by plaque C. pneumoniae infection.

Methodology/Principal Findings

Forty-two patients underwent elective carotid endarterectomy. Tissue obtained at surgery was stained by immunohistochemistry for Lp-PLA₂ grade, macrophages, IL-6, C. pneumoniae and CD4+ and CD8+ cells. Serum Lp-PLA₂ activity and mass were measured using the colorimetric activity method (CAM™) and ELISA, respectively. Serum homocysteine levels were measured by HPLC. Eleven (26.2%) patients were symptomatic with transient ischemic attacks. There was no correlation between patient risk factors (smoking, coronary artery disease, elevated cholesterol, diabetes, obesity, hypertension and family history of genetic disorders) for atherosclerosis and serum levels or plaque grade for Lp-PLA₂. Plaque Lp-PLA₂ correlated with serum homocysteine levels (p = 0.013), plaque macrophages (p<0.01), and plaque C. pneumoniae (p<0.001), which predominantly infected macrophages, co-localizing with Lp-PLA₂.

Conclusions

The significant association of plaque Lp-PLA₂ with plaque macrophages and C. pneumoniae suggests an interactive role in accelerating inflammation in atherosclerosis. A possible mechanism for C. pneumoniae in the atherogenic process may involve infection of macrophages that induce Lp-PLA₂ production leading to upregulation of inflammatory mediators in plaque tissue. Additional in vitro and in vivo research will be needed to advance our understanding of specific C. pneumoniae and Lp-PLA₂ interactions in atherosclerosis.

Lipoprotein-associated phospholipase A2: a new therapeutic target

Lipoprotein-associated phospholipase A2 is an enzyme produced by inflammatory cells, which binds to apolipoprotein B-containing lipoproteins and degrades oxidatively modified phospholipids in low-density lipoprotein cholesterol particles, leading to formation of proinflammatory and cytotoxic products. Experimental studies suggest a role for lipoprotein-associated phospholipase A2 in the formation of advanced rupture-prone atherosclerotic lesions, and epidemiological investigations have linked it to increased cardiovascular risk. Ongoing trials are evaluating the role of novel pharmacological inhibitors of this enzyme, such as darapladib, in the management of high-risk coronary artery disease patients.

PLA2G7 genotype, lipoprotein-associated phospholipase A2 activity, and coronary heart disease risk in 10 494 cases and 15 624 controls of European Ancestry

BACKGROUND

Higher lipoprotein-associated phospholipase A(2)(Lp-PLA2) activity is associated with increased risk of coronary heart disease (CHD), making Lp-PLA2 a potential therapeutic target. PLA2G7 variants associated with Lp-PLA2 activity could evaluate whether this relationship is causal.

METHODS AND RESULTS

A meta-analysis including a total of 12 studies (5 prospective, 4 case-control, 1 case-only, and 2 cross-sectional studies; n=26 118) was undertaken to examine the association of the following: (1) Lp-PLA2 activity versus cardiovascular biomarkers and risk factors and CHD events (2 prospective studies; n=4884); (2) PLA2G7 single-nucleotide polymorphisms and Lp-PLA2 activity (3 prospective, 2 case-control, 2 cross-sectional studies; up to n=6094); and (3) PLA2G7 single-nucleotide polymorphisms and angiographic coronary artery disease (2 case-control, 1 case-only study; n=4971 cases) and CHD events (5 prospective, 2 case-control studies; n=5523). Lp-PLA2 activity correlated with several CHD risk markers. Hazard ratios for CHD events for the top versus bottom quartile of Lp-PLA2 activity were 1.61 (95% confidence interval, 1.31 to 1.99) and 1.17 (95% confidence interval, 0.91 to 1.51) after adjustment for baseline traits. Of 7 single-nucleotide polymorphisms, rs1051931 (A379V) showed the strongest association with Lp-PLA2 activity, with VV subjects having 7.2% higher activity than AAs. Genotype was not associated with risk markers, angiographic coronary disease (odds ratio, 1.03; 95% confidence interval, 0.80 to 1.32), or CHD events (odds ratio, 0.98; 95% confidence interval, 0.82 to 1.17).

CONCLUSIONS

Unlike Lp-PLA2 activity, PLA2G7 variants associated with modest effects on Lp-PLA2 activity were not associated with cardiovascular risk markers, coronary atheroma, or CHD. Larger association studies, identification of single-nucleotide polymorphisms with larger effects, or randomized trials of specific Lp-PLA2 inhibitors are needed to confirm or refute a contributory role for Lp-PLA2 in CHD.

Nonsteroidal Anti-Inflammatory Drugs (NSAIDs): Progress in Small Molecule Drug Development

Ever since the discovery of aspirin, small molecule therapeutics have been widely prescribed to treat inflammation and pain. Aspirin and several small molecule NSAIDs are known to inhibit the enzymes cyclooxygenase-1 (COX-1) and -2 (COX-2). Despite the success of NSAIDs to treat inflammatory disorders, the development of a clinically useful small molecule NSAIDs with decreased side effect profiles is an ongoing effort. The recent discovery and development of selective COX-2 inhibitors was a step toward this direction. Emerging trends are represented by the progress in the development of hybrid agents such as nitric oxide donor-NSAIDs (NO-NSAIDs) and dual COX/lipoxygenase (LOX) inhibitors. This review focuses on the recent advances in the rational design of small molecule NSAIDs in therapy.

Lipoprotein-associated phospholipase A2 activity and incident coronary heart disease among men and women with type 2 diabetes

OBJECTIVE

Lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) has been shown to be associated with increased risk of coronary heart disease (CHD) in general adult populations. Because men and women with type 2 diabetes are at particularly high risk for CHD, the aim of this study was to assess the association of Lp-PLA(2) with future coronary events among diabetic men and women.

RESEARCH DESIGN AND METHODS

We measured Lp-PLA(2) activity among 740 men and 777 women with confirmed diabetes enrolled in the Health Professionals Follow-Up Study (HPFS) and Nurses' Health Study (NHS). Participants were free of all cardiovascular disease and cancer at baseline.

RESULTS

During 10 years of follow-up among men and 14 years among women, we documented 178 and 146 cases of CHD, respectively. We defined CHD as coronary artery bypass graft, angioplasty, nonfatal myocardial infarction, and fatal CHD. After adjustment for age, smoking, medical history, and biomarkers including C-reactive protein, HDL, and LDL, the relative risk of total CHD comparing extreme tertiles of Lp-PLA(2) was 1.39 (95% CI 1.01-1.90; P trend = 0.03). When we restricted analyses to only nonfatal myocardial infarction and fatal CHD, the relative risk was 1.75 (95% CI 1.05-2.92; P for trend = 0.001). LDL, HDL, C-reactive protein, hormone replacement therapy use, and diabetes duration did not modify these relationships.

CONCLUSIONS

Levels of Lp-PLA(2) activity were significantly associated with incident CHD among men and women with type 2 diabetes, independent of traditional and inflammatory risk factors. This positive association was strongest for more severe clinical end points.

Lipoprotein-associated phospholipase A(2) and risk of coronary disease, stroke, and mortality: collaborative analysis of 32 prospective studies

BACKGROUND

Lipoprotein-associated phospholipase A(2) (Lp-PLA(2)), an inflammatory enzyme expressed in atherosclerotic plaques, is a therapeutic target being assessed in trials of vascular disease prevention. We investigated associations of circulating Lp-PLA(2) mass and activity with risk of coronary heart disease, stroke, and mortality under different circumstances.

METHODS

With use of individual records from 79 036 participants in 32 prospective studies (yielding 17 722 incident fatal or non-fatal outcomes during 474 976 person-years at risk), we did a meta-analysis of within-study regressions to calculate risk ratios (RRs) per 1 SD higher value of Lp-PLA(2) or other risk factor. The primary outcome was coronary heart disease.

FINDINGS

Lp-PLA(2) activity and mass were associated with each other (r=0.51, 95% CI 0.47-0.56) and proatherogenic lipids. We noted roughly log-linear associations of Lp-PLA(2) activity and mass with risk of coronary heart disease and vascular death. RRs, adjusted for conventional risk factors, were: 1.10 (95% CI 1.05-1.16) with Lp-PLA(2) activity and 1.11 (1.07-1.16) with Lp-PLA(2) mass for coronary heart disease; 1.08 (0.97-1.20) and 1.14 (1.02-1.27) for ischaemic stroke; 1.16 (1.09-1.24) and 1.13 (1.05-1.22) for vascular mortality; and 1.10 (1.04-1.17) and 1.10 (1.03-1.18) for non-vascular mortality, respectively. RRs with Lp-PLA(2) did not differ significantly in people with and without initial stable vascular disease, apart from for vascular death with Lp-PLA(2) mass. Adjusted RRs for coronary heart disease were 1.10 (1.02-1.18) with non-HDL cholesterol and 1.10 (1.00-1.21) with systolic blood pressure.

INTERPRETATION

Lp-PLA(2) activity and mass each show continuous associations with risk of coronary heart disease, similar in magnitude to that with non-HDL cholesterol or systolic blood pressure in this population. Associations of Lp-PLA(2) mass and activity are not exclusive to vascular outcomes, and the vascular associations depend at least partly on lipids.

FUNDING

UK Medical Research Council, GlaxoSmithKline, and British Heart Foundation.

Lp-PLA2 Inhibition-The Atherosclerosis Panacea?

Based on the complex pathophysiology of atherosclerosis, a large number of biomarkers that relate to lipids, inflammation, immunity, thrombosis and hemostasis, have been investigated experimentally, in epidemiologic studies and in clinical trials. Interest focuses on their potential role to aid in risk stratification, as possible surrogate markers of atherosclerosis, and potential targets for therapy. More recently, one lipid associated biomarker, lipoprotein-associated phospholipase A2 (Lp-PLA₂), has gained considerable interest. In addition to a plausible pathophysiological role by generating pro-inflammatory and pro-atherogenic compounds from oxidized LDL in the vessel wall, there is a large, fairly consistent epidemiological database indicating that increased levels of Lp-PLA₂ mass or activity are associated with increased risk for cardiovascular outcomes; such data further suggest that it might improve risk stratification. In addition, clinical studies indicate that increased Lp-PLA₂ levels are associated with endothelial dysfunction. Moreover, it may also serve as an interesting therapeutic target, since a specific inhibitor of the enzyme is available with promising animal data and initial positive data in humans. Recent experimental data from a hyperlipidemic diabetic pig model strongly suggest that increased Lp-PLA₂ in the vessel wall is associated with a more vulnerable plaque phenotype which can be modulated by inhibiting Lp-PLA₂ activity. A biomarker study in more than 1,000 patients with CHD over three months has demonstrated a positive effect on various inflammatory molecules. In addition, an imaging study using IVUS based modalities (greyscale, virtual histology, and palpography) together with a panel of biomarkers (IBIS-2) has been done in more than 300 patients with CHD treated over 12 months and results indicate that the progression of the necrotic core of the plaque can be retarded. Inhibition of the pro-atherogenic and pro-inflammatory effects of Lp-PLA₂ may therefore contribute to decrease the residual risk in high risk patients already on polypharmacotherapy. This hypothesis is now being tested in two large phase 3 clinical trials. Thus, Lp-PLA₂ indeed may represent a biomarker and a promising target for intervention.

Darapladib

IMPORTANCE OF THE FIELD

Atherosclerosis is an inflammatory-immune mediated disease process. Plaque rupture is responsible for the clinical events of ischemic death, myocardial infarction, acute coronary syndromes and ischemic strokes. Lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) seems to play a major role in the development of such high-risk lesions, in both the coronary and carotid arteries. Darapladib is a selective inhibitor of Lp-PLA(2).

AREAS COVERED IN THIS REVIEW

An overview of darapladib by reviewing the studies (1990 - 2009) that have provided the rationale for the development of darapladib; and a discussion of its potential merit as a new therapeutic drug to target high-risk atherosclerosis.

WHAT THE READER WILL GAIN

The reader should gain an understanding of the importance of inflammation during atherogenesis as well as of the biology of Lp-PLA(2) and its proatherogenic role. Additional insights will be gained into the role of selective inhibitors of Lp-PLA(2) as new therapeutic agents.

TAKE HOME MESSAGE

Darapladib is a selective inhibitor of Lp-PLA(2) and represents a new class of therapeutic agents that target inflammation to treat high-risk atherosclerosis.

Lipid oxidation and peroxidation in CNS health and disease: from molecular mechanisms to therapeutic opportunities

Reactive oxygen species (ROS) are produced at low levels in mammalian cells by various metabolic processes, such as oxidative phosphorylation by the mitochondrial respiratory chain, NAD(P)H oxidases, and arachidonic acid oxidative metabolism. To maintain physiological redox balance, cells have endogenous antioxidant defenses regulated at the transcriptional level by Nrf2/ARE. Oxidative stress results when ROS production exceeds the cell's ability to detoxify ROS. Overproduction of ROS damages cellular components, including lipids, leading to decline in physiological function and cell death. Reaction of ROS with lipids produces oxidized phospholipids, which give rise to 4-hydroxynonenal, 4-oxo-2-nonenal, and acrolein. The brain is susceptible to oxidative damage due to its high lipid content and oxygen consumption. Neurodegenerative diseases (AD, ALS, bipolar disorder, epilepsy, Friedreich's ataxia, HD, MS, NBIA, NPC, PD, peroxisomal disorders, schizophrenia, Wallerian degeneration, Zellweger syndrome) and CNS traumas (stroke, TBI, SCI) are problems of vast clinical importance. Free iron can react with H(2)O(2) via the Fenton reaction, a primary cause of lipid peroxidation, and may be of particular importance for these CNS injuries and disorders. Cholesterol is an important regulator of lipid organization and the precursor for neurosteroid biosynthesis. Atherosclerosis, the major risk factor for ischemic stroke, involves accumulation of oxidized LDL in the arteries, leading to foam cell formation and plaque development. This review will discuss the role of lipid oxidation/peroxidation in various CNS injuries/disorders.

Phospholipase A2 inhibitors in the treatment of atherosclerosis: a new approach moves forward in the clinic

Phase II results of the trials of two phospholipase A2 inhibitors which may be of value in the treatment of atherosclerosis and cardiovascular disease have been reported in the past year. Darapladib (GlaxoSmithKline) is an inhibitor of lipoprotein-associated phospholipase A2 and varespladib (Anthera) inhibits several forms of the secreted phospholipase A2s. Despite the apparent similarity of mechanism, which is also built into the compounds' names, the role of the two types of phospholipase in atherogenesis is very different. Evidence for this comes from a range of preclinical studies and from epidemiological data which are summarised here. These data provide a basis for the Phase II studies and support decisions to move into Phase III, a decision which in the case of darapladib has been made and studies commenced (STABILITY trial). For varespladib the FRANCIS-ACS trial in acute coronary syndrome patients is in progress.

The role of lipoprotein-associated phospholipase A2 in atherosclerosis may depend on its lipoprotein carrier in plasma

Platelet-activating factor (PAF) acetylhydrolase exhibits a Ca(2+)-independent phospholipase A2 activity and degrades PAFas well as oxidized phospholipids (oxPL). Such phospholipids are accumulated in the artery wall and may play key roles in vascular inflammation and atherosclerosis. PAF-acetylhydrolase in plasma is complexed to lipoproteins; thus it is also referred to as lipoprotein-associated phospholipase A2 (Lp-PLA2). Lp-PLA2 is primarily associated with low-density lipoprotein (LDL), whereas a small proportion of circulating enzyme activity is also associated with high-density lipoprotein (HDL). The majority of the LDL-associated Lp-PLA2 (LDL-Lp-PLA2) activity is bound to atherogenic small-dense LDL particles and it is a potential marker of these particles in plasma. The distribution of Lp-PLA2 between LDL and HDL is altered in various types of dyslipidemias. It can be also influenced by the presence of lipoprotein (a) [Lp(a)] when plasma levels of this lipoprotein exceed 30 mg/dl. Several lines of evidence suggest that the role of plasma Lp-PLA2 in atherosclerosis may depend on the type of lipoprotein particle with which this enzyme is associated. In this regard, data from large Caucasian population studies have shown an independent association between the plasma Lp-PLA2 levels (which are mainly influenced by the levels of LDL-Lp-PLA2) and the risk of future cardiovascular events. On the contrary, several lines of evidence suggest that HDL-associated Lp-PLA2 may substantially contribute to the HDL antiatherogenic activities. Recent studies have provided evidence that oxPL are preferentially sequestered on Lp(a) thus subjected to degradation by the Lp(a)-associated Lp-PLA2. These data suggest that Lp(a) may be a potential scavenger of oxPL and provide new insights into the functional role of Lp(a) and the Lp(a)-associated Lp-PLA2 in normal physiology as well as in inflammation and atherosclerosis. The present review is focused on recent advances concerning the Lp-PLA2 structural characteristics, the molecular basis of the enzyme association with distinct lipoprotein subspecies, as well as the potential role of Lp-PLA2 associated with different lipoprotein classes in atherosclerosis and cardiovascular disease.

Darapladib and atherosclerotic plaque: should lipoprotein-associated phospholipase A2 be a therapeutic target?

There is great interest in developing a reliable measure of atherosclerotic disease activity that can serve as an index of response to antiatherosclerotic therapies. The epidemiologic relationship between lipid measures, most notably low-density lipoprotein cholesterol (LDL-C), and binary cardiovascular events has been confirmed in treatment trials reliably demonstrating a reduction in LDL-C translating into improved cardiovascular outcomes. Lipoprotein-associated phospholipase A2 (LpPLA2) is part of a family of lipases involved in the modification of lipids within the atheroma and may be a complimentary therapeutic target to the reduction of LDL-C in patients with advanced atherosclerosis. Darapladib is an orally available, specific inhibitor of LpPLA2 activity and has been shown to reduce lysophosphatidylcholine content and expression of multiple genes associated with macrophage and T-lymphocyte functioning, with considerable decrease in plaque and necrotic core area. Thus, this agent holds the hope of being a bona fide antiatherosclerotic therapy that can be gauged through blood measurement of LpPLA2 activity.

Lipoprotein-associated phospholipase A(2) and atherosclerosis

PURPOSE OF REVIEW

There is substantial data from over 50 000 patients that increased lipoprotein-associated phospholipase A2 (Lp-PLA2) mass or activity is associated with an increased risk of cardiac death, myocardial infarction, acute coronary syndromes and ischemic stroke. However, only recently have data emerged demonstrating a role of Lp-PLA2 in development of advanced coronary artery disease. Indeed, Lp-PLA2 may be an important link between lipid homeostasis and the vascular inflammatory response.

RECENT FINDINGS

Lp-PLA2, also known as platelet-activating factor acetylhydrolase, rapidly cleaves oxidized phosphatidylcholine molecules produced during the oxidation of LDL and atherogenic lipoprotein Lp(a), generating the soluble proinflammatory and proapoptotic lipid mediators, lyso-phosphatidylcholine and oxidized nonesterified fatty acids. These proinflammatory lipids play an important role in the development of atherosclerotic necrotic cores, the substrate for acute unstable coronary disease by recruiting and activating leukocytes/macrophages, inducing apoptosis and impairing the subsequent removal of dead cells. Selective inhibition of Lp-PLA2 reduces development of necrotic cores and may result in stabilization of atherosclerotic plaques.

SUMMARY

Recent data have shown that immune pathways play a major role in the development and progression of high-risk atherosclerosis, which leads to ischemic sudden death, myocardial infarction, acute coronary syndromes and ischemic strokes. Persistent and sustained macrophage apoptosis appears to play a major role in the resulting local inflammatory response in part by effects elicited by Lp-PLA2. Selective inhibition of Lp-PLA2 has been postulated to reduce necrotic core progression and the clinical sequelae of advanced, unstable atherosclerosis.

Phospholipase A2 inhibitors

PURPOSE OF REVIEW

As the role of lipids and inflammation in the genesis and progression of the atherosclerosis disease is unquestionable, novel treatment modalities that target both aspects are currently under investigation.

RECENT FINDINGS

For a long time atherosclerosis was regarded as a lipid-driven disease, but now it is evident that it also involves the simultaneous and combined effect of inflammation and immunological pathways. The secreted PLA2s and the lipoprotein-associated phospholipase A2 (Lp-PLA2) have been associated with atherogenesis and its complications. These two enzymes produce biologically active metabolites that are involved in several phases of the atherosclerosis process.

SUMMARY

In animal, pathological and epidemiological studies, the increased levels of these two phospholipases (i.e. PLA2s and Lp-PLA2) have been related with an increase in complex coronary lesions and increase in major cardiovascular clinical events, respectively. Therefore, inhibition of these enzymes has become the focus of research in this last decennium. Novel pharmacological inhibitors of those enzymes such as darapladib and varespladib emerge as promising therapeutical options for treating patients with coronary artery disease. Ongoing mechanistic and clinical outcome trials will further elucidate their role in this context.

Novel and conventional biomarkers for prediction of incident cardiovascular events in the community

CONTEXT

Prior studies have demonstrated conflicting results regarding how much information novel biomarkers add to cardiovascular risk assessment.

OBJECTIVE

To evaluate the utility of contemporary biomarkers for predicting cardiovascular risk when added to conventional risk factors.

DESIGN, SETTING, AND PARTICIPANTS

Cohort study of 5067 participants (mean age, 58 years; 60% women) without cardiovascular disease from Malmö, Sweden, who attended a baseline examination between 1991 and 1994. Participants underwent measurement of C-reactive protein (CRP), cystatin C, lipoprotein-associated phospholipase 2, midregional proadrenomedullin (MR-proADM), midregional proatrial natriuretic peptide, and N-terminal pro-B-type natriuretic peptide (N-BNP) and underwent follow-up until 2006 using the Swedish national hospital discharge and cause-of-death registers and the Stroke in Malmö register for first cardiovascular events (myocardial infarction, stroke, coronary death).

MAIN OUTCOME MEASURES

Incident cardiovascular and coronary events.

RESULTS

During median follow-up of 12.8 years, there were 418 cardiovascular and 230 coronary events. Models with conventional risk factors had C statistics of 0.758 (95% confidence interval [CI], 0.734 to 0.781) and 0.760 (0.730 to 0.789) for cardiovascular and coronary events, respectively. Biomarkers retained in backward-elimination models were CRP and N-BNP for cardiovascular events and MR-proADM and N-BNP for coronary events, which increased the C statistic by 0.007 (P = .04) and 0.009 (P = .08), respectively. The proportion of participants reclassified was modest (8% for cardiovascular risk, 5% for coronary risk). Net reclassification improvement was nonsignificant for cardiovascular events (0.0%; 95% CI, -4.3% to 4.3%) and coronary events (4.7%; 95% CI, -0.76% to 10.1%). Greater improvements were observed in analyses restricted to intermediate-risk individuals (cardiovascular events: 7.4%; 95% CI, 0.7% to 14.1%; P = .03; coronary events: 14.6%; 95% CI, 5.0% to 24.2%; P = .003). However, correct reclassification was almost entirely confined to down-classification of individuals without events rather than up-classification of those with events.

CONCLUSIONS

Selected biomarkers may be used to predict future cardiovascular events, but the gains over conventional risk factors are minimal. Risk classification improved in intermediate-risk individuals, mainly through the identification of those unlikely to develop events.

Update on patented cholesterol absorption inhibitors

BACKGROUND

Atherosclerosis is one of the most life-threatening diseases primarily associated with hypercholesterolemia and is characterized by increased serum cholesterol level. Cholesterol originates from both its de novo synthesis within the hepatic cells and its absorption into the intestine in the form of dietary or bile cholesterol. Interventions influencing both of these processes are promising therapeutic options to lower the cholesterol level. Hydroxymethyl glutaryl-CoA reductase inhibitors, commonly known as statins, effectively block the rate determining step in the biosynthesis of cholesterol. Ezetimibe is the first new class of drugs used to treat hypercholesterolemia by inhibition of cholesterol absorption through Niemann Pick C1 Like 1 membrane of enterocytes. Therefore, combination therapy of ezetimibe and statins offers an efficacious new approach for the prevention and treatment of hypercholesterolemia.

OBJECTIVES

The present review focuses on updates on ezetimibe and patented profile of novel cholesterol absorption inhibitors followed by critical analysis of different targets such as cholesterol esterase inhibitors, bile acid transport inhibitors or phospholipase-A(2) inhibitors, etc.which play an important role in the lipid absorption.

CONCLUSION

The discovery of ezetimibe has opened a new door for the management of hyper-cholesterolemia in combination with statins. There are newer analogues that are under clinical trials, among which darapladib, FM-VP4 and A-002 are promising compounds.

Lipoprotein-associated phospholipase A2: a cardiovascular risk predictor and a potential therapeutic target

Lipoprotein-associated phospholipase A2 (Lp-PLA2), present in the circulation and in atherosclerotic plaque, is an inflammatory marker with potential use as a predictor of cardiovascular risk and as a therapeutic target. Although Lp-PLA2 is associated with both LDL and HDL, it is important to determine whether Lp-PLA2 has a predominantly pro- or anti-atherogenic effect. Increasing evidence suggests a proatherogenic role for Lp-PLA2. ©iEpidemiologic and clinical evidence suggests Lp-PLA2 is an independent predictor of risk and may be superior to other inflammatory markers owing to its specificity and minimal biovariation. Lp-PLA2 inhibitors currently being investigated in clinical trials are promising novel anti-inflammatory agents with a specificity for the vascular bed and a potential for decreasing plaque vulnerability.