Building the Case for Clopidogrel as a World Health Organization Essential Medicine

Females are less likely to receive best medical therapy for stroke prevention before and after carotid revascularization than males

BACKGROUND

Current professional guidelines recommend best medical therapy (BMT) with statin agents and antiplatelet therapy for primary and secondary stroke prevention in patients with carotid artery stenosis. We aimed to assess the association of patient sex with preoperative BMT in patients undergoing carotid revascularization.

METHODS

We performed a retrospective review of Vascular Quality Initiative patients who underwent carotid endarterectomy or carotid artery stenting between January 2003 and February 2022. Multivariable logistic regression models were used to assess the association of patient sex with preoperative BMT after adjusting for sociodemographic, comorbidity, and disease severity characteristics. In-hospital outcomes were assessed by sex and preoperative BMT status.

RESULTS

Of 214,008 patients who underwent carotid revascularization, 38.7% (n = 82,855) were female and 61.3% (n = 131,153) were male. Overall, 77.2% (n = 63,922) of females were on preoperative BMT, compared with 80.4% (n = 105,375) of males (P < .001). After adjusting for baseline differences, females had 11% lower odds of being on BMT compared with males (adjusted odds ratio, 0.89; 95% confidence interval, 0.86-0.91). Postoperatively, females had 18% lower odds of being prescribed BMT than males (adjusted odds ratio, 0.82; 95% confidence interval, 0.79-0.84). In-hospital stroke (1.20% vs 1.51%), death (0.37% vs 0.66%), and stroke/death (1.46% vs 1.98%) were all significantly lower for patients on BMT (all P < .001).

CONCLUSIONS

There is a significant discrepancy in the proportion of females versus males receiving preoperative BMT for stroke prevention before carotid artery revascularization. In-hospital outcomes are worse in patients without BMT, highlighting the importance of raising awareness and implementing targeted interventions to improve preoperative adherence to stroke prevention guidelines.

Choline and trimethylamine N-oxide impair metabolic activation of and platelet response to clopidogrel through activation of the NOX/ROS/Nrf2/CES1 pathway

BACKGROUND

Trimethylamine N-oxide (TMAO), a gut microbe-generated metabolite, elicits thrombotic events by enhancing platelet reactivity; however, no studies have reported the effects of TMAO on the metabolism of and response to clopidogrel.

OBJECTIVES

To determine whether choline and TMAO could significantly impair metabolic activation of and platelet response to clopidogrel in choline- or TMAO-fed mice and the mechanisms involved.

METHODS

Male mice were fed with vehicle control (Ctrl), TMAO, choline alone or in combination with 3,3-dimethyl-1-butanol, N-acetyl-L-cysteine, or ML385 for 14 days and then treated with Ctrl or a single oral dose of clopidogrel. Plasma TMAO, protein levels of clopidogrel-metabolizing enzymes in the liver, plasma concentrations of clopidogrel and its metabolites, and adenosine diphosphate-induced platelet aggregation and activation were measured. In addition, HepG2 cells were treated with Ctrl or TMAO alone or in combination with N-acetyl-L-cysteine, ML385, or apocynin, and CES1, reactive oxygen species (ROS), and Nrf2 protein levels were measured, respectively.

RESULTS

TMAO significantly increased Ces1 protein expression and activity and clopidogrel hydrolysis in the liver as well as intracellular ROS and CES1 levels and Nrf2 nucleus translocation in HepG2 cells but decreased the formation of clopidogrel active metabolite and impaired platelet response to clopidogrel. Furthermore, concomitant use of 3,3-dimethyl-1-butanol, N-acetyl-L-cysteine, or ML385 effectively reversed choline- or TMAO-induced impairment of inhibition of platelet aggregation by clopidogrel in mice, respectively.

CONCLUSIONS

Choline and TMAO impair the metabolic activation of and platelet response to clopidogrel through the activation of the NOX-dependent ROS/Nrf2/CES1 pathway, suggesting novel strategies for overcoming clopidogrel resistance from bench to bedside.

P-glycoprotein deficiency enhances metabolic activation of and platelet response to clopidogrel through marked up-regulation of Cyp3a11 in mice: Direct evidence for the interplay between P-glycoprotein and Cyp3a

Variability in P-glycoprotein (P-gp) efflux transporting activity was supposed to be involved in altered intestinal absorption and bioavailability of clopidogrel in patients; however, reliable evidence is still lacking. In this study, we sought to determine whether P-gp could play an important role in the metabolic activation of and platelet response to clopidogrel in mice. Abcb1a/1b knock-out (KO) and wild-type (WT) mice were used to evaluate differences in the intracellular accumulation of clopidogrel in the intestine, liver, and brain tissues and in systemic exposure of clopidogrel and its main metabolites as well as the mechanisms involved. Results indicated that, compared with WT mice, KO mice exhibited an 84% increase in systemic exposure of clopidogrel active thiol metabolite H4 and a 14.5% rise of suppression of ADP-induced platelet integrin αIIbβ3 activation, paralleled by a 41% decrease in systemic exposure of clopidogrel due to enhanced systemic clearance. Furthermore, KO mice displayed a 45% increase in Cyp3a11 but a 23% decrease in Ces1 at their protein levels compared with WT mice. Concurrently, intracellular clopidogrel concentrations in the tissues examined did not differ significantly between KO and WT mice. We conclude that although P-gp does not transport clopidogrel and its major metabolites in mice, P-gp-deficient mice exhibit elevated formation of the active metabolite H4 and enhanced antiplatelet effect of clopidogrel through up-regulation of Cyp3a11 and down-regulation of Ces1, suggesting that P-gp activity may correlate inversely with the formation of H4 and antiplatelet efficacy of clopidogrel in clinical settings due to P-gp and CYP3A4 interplay.

Resource and Infrastructure-Appropriate Management of ST-Segment Elevation Myocardial Infarction in Low- and Middle-Income Countries

The 143 low- and middle-income countries (LMICs) of the world constitute 80% of the world's population or roughly 5.86 billion people with much variation in geography, culture, literacy, financial resources, access to health care, insurance penetration, and healthcare regulation. Unfortunately, their burden of cardiovascular disease in general and acute ST-segment-elevation myocardial infarction (STEMI) in particular is increasing at an unprecedented rate. Compounding the problem, outcomes remain suboptimal because of a lack of awareness and a severe paucity of resources. Guideline-based treatment has dramatically improved the outcomes of STEMI in high-income countries. However, no such focused recommendations exist for LMICs, and the unique challenges in LMICs make directly implementing Western guidelines unfeasible. Thus, structured solutions tailored to their individual, local needs, and resources are a vital need. With this in mind, a multicountry collaboration of investigators interested in LMIC STEMI care have tried to create a consensus document that extracts transferable elements from Western guidelines and couples them with local realities gathered from expert experience. It outlines general operating principles for LMICs focused best practices and is intended to create the broad outlines of implementable, resource-appropriate paradigms for management of STEMI in LMICs. Although this document is focused primarily on governments and organizations involved with improvement in STEMI care in LMICs, it also provides some specific targeted information for the frontline clinicians to allow standardized care pathways and improved outcomes.

The Role of Clopidogrel in 2020: A Reappraisal

Antiplatelet therapy is the mainstay of treatment and secondary prevention of cardiovascular disease (CVD), including acute coronary syndrome (ACS), transient ischemic attack (TIA) or minor stroke, and peripheral artery disease (PAD). The P2Y₁₂ inhibitors, of which clopidogrel was the first, play an integral role in antiplatelet therapy and therefore in the treatment and secondary prevention of CVD. This review discusses the available evidence concerning antiplatelet therapy in patients with CVD, with a focus on the role of clopidogrel. In combination with aspirin, clopidogrel is often used as part of dual antiplatelet therapy (DAPT) for the secondary prevention of ACS. Although newer, more potent P2Y₁₂ inhibitors (prasugrel and ticagrelor) show a greater reduction in ischemic risk compared with clopidogrel in randomized trials of ACS patients, these newer P2Y₁₂ inhibitors are often associated with an increased risk of bleeding. Deescalation of DAPT by switching from prasugrel or ticagrelor to clopidogrel may be required in some patients with ACS. Furthermore, real-world studies of ACS patients have not confirmed the benefits of the newer P2Y₁₂ inhibitors over clopidogrel. In patients with very high-risk TIA or stroke, short-term DAPT with clopidogrel plus aspirin for 21-28 days, followed by clopidogrel monotherapy for up to 90 days, is recommended. Clopidogrel monotherapy may also be used in patients with symptomatic PAD. In conclusion, there is strong evidence supporting the use of clopidogrel antiplatelet therapy in several clinical settings, which emphasizes the importance of this medication in clinical practice.

Effect of remote ischaemic conditioning on platelet reactivity and endogenous fibrinolysis in ST-elevation myocardial infarction: a substudy of the CONDI-2/ERIC-PPCI randomized controlled trial

AIMS

Remote ischaemic conditioning (RIC) has been shown to reduce myocardial infarct size in animal models of myocardial infarction. Platelet thrombus formation is a critical determinant of outcome in ST-segment elevation myocardial infarction (STEMI). Whether the beneficial effects of RIC are related to thrombotic parameters is unclear.

METHODS AND RESULTS

In a substudy of the Effect of Remote Ischaemic Conditioning on clinical outcomes in STEMI patients undergoing Primary Percutaneous Coronary Intervention (ERIC-PPCI) trial, we assessed the effect of RIC on thrombotic status. Patients presenting with STEMI were randomized to immediate RIC consisting of an automated autoRIC™ cuff on the upper arm inflated to 200 mmHg for 5 min and deflated for 5 min for four cycles (n = 53) or sham (n = 47). Venous blood was tested at presentation, discharge (48 h) and 6-8 weeks, to assess platelet reactivity, coagulation, and endogenous fibrinolysis using the Global Thrombosis Test and thromboelastography. Baseline thrombotic status was similar in the two groups. At discharge, there was some evidence that the time to in vitro thrombotic occlusion under high shear stress was longer with RIC compared to sham (454 ± 105 s vs. 403 ± 105 s; mean difference 50.1 s; 95% confidence interval 93.7-6.4, P = 0.025), but this was no longer apparent at 6-8 weeks. There was no difference in clot formation or endogenous fibrinolysis between the study arms at any time point.

CONCLUSION

RIC may reduce platelet reactivity in the first 48 h post-STEMI. Further research is needed to delineate mechanisms through which RIC may reduce platelet reactivity, and whether it may improve outcomes in patients with persistent high on-treatment platelet reactivity.

Modernizing the World Health Organization List of Essential Medicines for Preventing and Controlling Cardiovascular Diseases

The World Health Organization (WHO) Model List of Essential Medicines (EML) is a key tool for improving global access to medicines for all conditions, including cardiovascular diseases (CVDs). The WHO EML is used by member states to determine their national essential medicine lists and policies and to guide procurement of medicines in the public sector. Here, we describe our efforts to modernize the EML for global CVD prevention and control. We review the recent history of applications to add, delete, and change indications for CVD medicines, with the aim of aligning the list with contemporary clinical practice guidelines. We have identified 4 issues that affect decisions for the EML and may strengthen future applications: 1) cost and cost-effectiveness; 2) presence in clinical practice guidelines; 3) feedback loops; and 4) community engagement. We share our lessons to stimulate others in the global CVD community to embark on similar efforts.

Overcoming Clopidogrel Resistance: Three Promising Novel Antiplatelet Drugs Developed in China

Clopidogrel is one of the most frequently prescribed drugs worldwide; however, the presence of clopidogrel resistance and high susceptibility to genetic variations and drug interactions are facilitating the development of other antiplatelet drugs. To overcome clopidogrel resistance, several promising clopidogrel analogues have been developed in China, such as vicagrel (and its deuterated analogues), PLD-301, and W1. These novel chemical analogues are all characterized by much faster and more efficient bioconversion to clopidogrel thiolactone (or 2-oxo-clopidogrel, the precursor of clopidogrel active metabolite) in the intestine than clopidogrel itself through bypassing the first-step P450-mediated oxidation of clopidogrel in the liver. Of them, metabolic conversion of vicagrel and PLD-301 to 2-oxo-clopidogrel is catalyzed by intestinal carboxylesterase 2 and alkaline phosphatase, respectively. In this review article, we summarized all evidence on highly efficient bioconversion to their shared precursor of clopidogrel active metabolite and the mechanisms underlying such a pronounced improvement. These drugs in the pipeline would be promising antiplatelet drugs that could be superior to clopidogrel in future patient care.

Human UGT2B7 is the major isoform responsible for the glucuronidation of clopidogrel carboxylate

Clopidogrel is predominantly hydrolyzed to clopidogrel carboxylic acid (CCA) by carboxylesterase 1, and subsequently CCA is glucuronidated to clopidogrel acyl glucuronide (CAG) by uridine diphosphate-glucuronosyltransferases (UGTs); however, the UGT isoenzymes glucuronidating CCA remain unidentified to date. In this study, the glucuronidation of CCA was screened with pooled human liver microsomes (HLMs) and 7 human recombinant UGT (rUGT) isoforms. Results indicated that rUGT2B7 exhibited the highest catalytical activity for the CCA glucuronidation as measured with a mean V_max value of 120.9 pmol/min/mg protein, 3- to 12-fold higher than that of the other rUGT isoforms tested. According to relative activity factor approach, the relative contribution of rUGT2B7 to CCA glucuronidation was estimated to be 58.6%, with the minor contributions (3%) from rUGT1A9. Moreover, the glucuronidation of CCA followed Michaelis-Menten kinetics with a mean K_m value of 372.9 μM and 296.4 μM for pooled HLMs and rUGT2B7, respectively, showing similar affinity for both. The formation of CAG was significantly inhibited by azidothymidine and gemfibrozil (well-characterized UGT2B7 substrates) in a concentration-dependent manner, or by fluconazole (a typical UGT2B7-selective inhibitor) in a time-dependent manner, for both HLMs and rUGT2B7, respectively. In addition, CCA inhibited azidothymidine glucuronidation (catalyzed almost exclusively by UGT2B7) by HLMs and rUGT2B7 in a concentration-dependent manner, indicating that CCA is a substrate of UGT2B7. These results reveal that UGT2B7 is the major enzyme catalyzing clopidogrel glucuronidation in the human liver, and that there is the potential for drug-drug interactions between clopidogrel and the other substrate drugs of UGT2B7.