Clopidogrel: the future choice for preventing platelet activation during coronary stenting?

Biodegradation of clopidogrel bisulfate by Pseudomonas aeruginosa and Pseudomonas putida strains isolated from Algerian wastewater

The clopidogrel bisulfate was degraded under aerobic conditions by two bacterial strains isolated from industrial effluents in El-Harrach, Algeria. The sequencing of their 16S rRNA revealed that these two strains are Pseudomonas aeruginosa and Pseudomonas putida. The experiments showed that this consortium could remove clopidogrel bisulfate at high concentrations (5-1500 mg·L^-1) within 96 h incubation period. The HPLC analysis recorded 75.23% degradation of clopidogrel bisulfate at an initial concentration of 100 mg·L^-1 after five days of incubation at pH 7.0 and a temperature of 30 °C. Also, a maximum degradation of 99.08% was carried out at a more basic pH (8.5). While only 41% was degraded at a temperature of 20 °C. Moreover, the presence of supplemental sources of carbon and nitrogen in the mixed culture media effectively improved the biodegradation of clopidogrel bisulfate by the stains. Finally, the morphology of the strains and the properties of the cell's surface were studied using a scanning electron microscope (SEM). This study reports, for the first time, the viability of the aerobic biodegradation of clopidogrel bisulfate in water in a wide range of concentrations.

Multicomponent reactions as a potent tool for the synthesis of benzodiazepines

Benzodiazepines (BZDs), a diverse class of benzofused seven-membered N-heterocycles, display essential pharmacological properties and play vital roles in some biochemical processes. They have mainly been prescribed as potential therapeutic agents, which interestingly represent various biological activities such as anticancer, anxiolytic, antipsychotic, anticonvulsant, antituberculosis, muscle relaxant, and antimicrobial activities. The extensive biological activities of BZDs in various fields have encouraged medicinal chemists to discover and design novel BZD-based scaffolds as potential therapeutic candidates with the favorite biological activity through an efficient protocol. Although certainly valuable and important, conventional synthetic routes to these bicyclic benzene compounds contain methodologies often requiring multistep procedures, which suffer from waste materials generation and lack of sustainability. By contrast, multicomponent reactions (MCRs) have recently advanced as a green synthetic strategy for synthesizing BZDs with the desired scope. In this regard, MCRs, especially Ugi and Ugi-type reactions, efficiently and conveniently supply various complex synthons, which can easily be converted to the BZDs via suitable post-transformations. Also, MCRs, especially Mannich-type reactions, provide speedy and economic approaches for the one-pot and one-step synthesis of BZDs. As a result, various functionalized-BZDs have been achieved by developing mild, efficient, and high-yielding MCR protocols. This review covers all aspects of the synthesis of BZDs with a particular focus on the MCRs as well as the mechanism chemistry of synthetic protocols. The present manuscript opens a new avenue for organic, medicinal, and industrial chemists to design safe, environmentally benign, and economical methods for the synthesis of new and known BZDs.

Tailor-made amino acids in the design of small-molecule blockbuster drugs

The role of amino acids (AAs) in modern health industry is well-appreciated. Residues of individual AAs, or their chemical modifications, such as diamines and amino alcohols, are frequently found in the structures of modern pharmaceuticals. The goal of this review article, is to emphasize that, currently, tailor-made AAs serve as key structural features in many most successful pharmaceuticals, so-called blockbuster drugs. In the present article, we profile 14 small-molecule drugs, underscoring the breadth of structural variety of AAs applications in numerous therapeutic areas. For each compound, we provide spectrum of biological activity, medicinal chemistry discovery, and synthetic approaches.

Atorvastatin (Lipitor) by MCR

A concise and convergent synthesis of the atorvastatin, the best-selling cardiovascular drug of all time, is presented. Our approach is based on an Ugi reaction, which shortens the current synthetic route and is advantageous over the published syntheses.

Green chemistry approaches as sustainable alternatives to conventional strategies in the pharmaceutical industry

Green chemistry is a rapidly developing field for the sustainable development of future science and technology. Incorporating green chemistry into the synthesis of active pharmaceutical ingredients and intermediates is of ongoing importance to the pharmaceutical industry.

Antiplatelet drugs: mechanisms and risks of bleeding following cardiac operations

Preoperative antiplatelet drug use is common in patients undergoing coronary artery bypass grafting (CABG). The impact of these drugs on bleeding and blood transfusion varies. We hypothesize that review of available evidence regarding drug-related bleeding risk, underlying mechanisms of platelet dysfunction, and variations in patient response to antiplatelet drugs will aid surgeons as they assess preoperative risk and attempt to limit perioperative bleeding. The purpose of this review is to (1) examine the role that antiplatelet drugs play in excessive postoperative blood transfusion, (2) identify possible mechanisms to explain patient response to antiplatelet drugs, and (3) formulate a strategy to limit excessive blood product usage in these patients. We reviewed available published evidence regarding bleeding risk in patients taking preoperative antiplatelet drugs. In addition, we summarized our previous research into mechanisms of antiplatelet drug-related platelet dysfunction. Aspirin users have a slight but significant increase in blood product usage after CABG (0.5 U of nonautologous blood per treated patient). Platelet adenosine diphosphate (ADP) receptor inhibitors are more potent antiplatelet drugs than aspirin but have a half-life similar to aspirin, around 5 to 10 days. The American Heart Association/American College of Cardiology and the Society of Thoracic Surgeons guidelines recommend discontinuation, if possible, of ADP inhibitors 5 to 7 days before operation because of excessive bleeding risk, whereas aspirin should be continued during the entire perioperative period in most patients. Individual variability in response to aspirin and other antiplatelet drugs is common with both hyper- and hyporesponsiveness seen in 5 to 25% of patients. Use of preoperative antiplatelet drugs is a risk factor for increased perioperative bleeding and blood transfusion. Point-of-care tests can identify patients at high risk for perioperative bleeding and blood transfusion, although these tests have limitations. Available evidence suggests that multiple blood conservation techniques benefit high-risk patients taking antiplatelet drugs before operation. Guidelines for patients who take aspirin and/or thienopyridines before cardiac procedures include some or all of the following: (1) preoperative identification of high-risk patients using point-of-care testing; (2) withdrawal of aspirin or other antiplatelet drugs for a few days and delay of operation in patients at high risk for bleeding if clinical circumstances permit; (3) selective perioperative use of evidence-based blood conservation interventions (e.g., short-course erythropoietin, off-pump procedures, and use of intraoperative blood conservation techniques), especially in high-risk patients; and (4) platelet transfusions if clinical bleeding occurs.

Single nucleotide polymorphisms of the purinergic 1 receptor are not associated with myocardial infarction in a Latvian population

The purinergic 1 receptor (P2RY1) has been implicated in development of heart disease and in individual pharmacodynamic response to anticoagulant therapies. However, the association of polymorphisms in the P2RY1 gene with myocardial infarction (MI), and its associated conditions, has yet to be reported in the literature. We evaluated seven known SNPs in P2RY1 for association with MI in a Latvian population. Seven independent parameters that are related to MI [body mass index (BMI), type 2 diabetes (T2D), angina pectoris, hypertension, hyperlipidemia, atrial fibrillation and heart failure] were investigated. No significant association with MI was observed for any of the polymorphisms. Those SNPs for which the P value was close to significance were located in coding or promoter regions. Intriguingly, carriers of the minor allele in the P2RY1 gene locus showed a tendency towards higher onset age for MI, suggesting a possible protective effect of these SNPs against MI or their contribution in progression as opposed to onset. Finally, a linkage disequilibrium (LD) plot was generated for these polymorphisms in the Latvian population. The results of this study suggest that the role of P2RY1 in individuals from Latvian population is likely to be principally involved in platelet aggregation and thromboembolic diseases, and not as a significant contributing factor to the global metabolic syndrome.

On the industrial applications of MCRs: molecular diversity in drug discovery and generic drug synthesis

During the last decades, multicomponent chemistry has gained much attention in pharmaceutical research, especially in the context of lead finding and optimization. Here, in particular, the main advantages of multicomponent reactions (MCRs) like ease of automation and high diversity generation were utilized. In consequence of these beneficial properties, a plethora of new MCRs combined with appropriate classical reaction sequences have been published, the accessible chemical space was extended steadily. In the meantime, the desired high diversity became a challenge itself, because by now the systematic use of this huge and unmanageable space for drug discovery was limited by the lack of suitable computational tools. Therefore, this article provides an insight for the rational use of this enormous chemical space in drug discovery and generic drug synthesis. In this context, a short overview of the applied chemo informatics, necessary for the virtual screening of the biggest available chemical space, is given. Furthermore, some examples for recently developed multicomponent sequences are presented.

Relationships between optical aggregometry (type born) and flow cytometry in evaluating ADP-induced platelet activation

BACKGROUND

Platelet response to activating agents is used to monitor the efficacy of anti-aggregation therapies. The aim of our study has been to demonstrate the existence of relationships between early events of ADP-induced platelet activation, measured by flow cytometry and platelet-rich plasma aggregation, quantified by optical aggregometry.

METHODS

We evaluated peripheral blood of 12 donors. The following parameters were quantified by cytometry after stimulation with adenosine diphosphate (ADP) (0.5, 1, 2, 5, 10, 20 muM): CD62P (P-selectin) and PAC-1 expression, and cytosolic Ca(2+) mobilization. Aggregation was measured by optical aggregometry. We also studied 13 patients, undergoing coronary stenting, treated with aspirin (before procedure) or with aspirin plus clopidogrel (after procedure). We evaluated CD62P and PAC-1 expression, aggregation, and vasodilator-stimulated phopshoprotein phosphorylation (platelet reactivity index, PRI).

RESULTS

Flow procedures were more sensitive than aggregometry, with a lowest interindividual variability. Linear relationships existed in donors between CD62P expression and Ca(2+) mobilization (P < 0.0001), and between aggregation and Ca(2+) mobilization (P < 0.0001). Linear relationships existed between aggregation and CD62P expression, as percentage (P < 0.0001), or relative fluorescence intensity (RFI) (P < 0.0001). Exponential equations related aggregation and PAC-1 expression, as percentage (P < 0.0001), or RFI (P < 0.0001). Linear relationships between aggregation and CD62P expression (as percentage) existed in the patients before (P = 0.0022) and after procedure (P = 0.0020). Exponential relationships between aggregation and PAC-1 expression (as percentage) existed before (P = 0.0012) and after procedure (P = 0.0024). Linear correlations related aggregation response predicted on CD62P expression, and measured aggregation inhibition after clopidogrel (P = 0.0013) as well as predicted aggregation and PRI inhibition (P = 0.0031).

CONCLUSIONS

Tight relationships between aggregation and cytometric quantification of platelet markers in whole blood, in particular CD62P, allow to predict aggregation response to ADP from flow data in patients treated with aspirin alone or with aspirin plus clopidogrel.

Expression of platelet surface receptors and early changes in platelet function in patients with STEMI treated with abciximab and clopidogrel versus clopidogrel alone

BACKGROUND

Platelets play a crucial role in the pathogenesis of acute coronary syndromes (ACS). The efficacy of antiplatelet treatment is pivotal in the success of percutaneous coronary intervention (PCI) performed in patients with ACS.

OBJECTIVE

The aim of the study was to investigate the effects of clopidogrel with or without abciximab on the expression of platelet surface receptors and platelet function in patients with ST-segment elevation myocardial infarction (STEMI) undergoing PCI.

MATERIALS AND METHODS

Thirty patients with STEMI were included in the study. During acute primary coronary intervention, patients received aspirin (acetylsalicylic acid) and clopidogrel in a loading dose of 300mg. Clopidogrel was the only antiplatelet therapy used by nine patients (group B). Twenty-one patients (group A) received additional abciximab. Blood samples were collected and analyzed twice: before and up to 22 hours after administration of antiplatelet therapy. The platelet aggregation was established as primary platelet-related hemostasis (closure time [CT] assessed using the PFA100 system). The absolute number of platelet surface antigens as CD41a, CD42a, CD42b, CD61, and CD62P were determined by flow cytometry analysis.

RESULTS

The study revealed a statistically significant increase in CT induced by adenosine diphosphate and adrenaline (epinephrine) +130 seconds (p < 0.0001) and +94 seconds (p < 0.0001), respectively, in group A patients post-therapy. While in group B the parameters of CT did not change after treatment. In addition, the absolute number of CD41a antigens (glycoprotein [GP] IIb/IIIa) increased significantly after treatment in group A. No significant changes were observed after treatment in the expression of CD62P (P-selectin) antigens in either treatment group. There was a significant reduction in the percentage of CD62P-positive platelets in group B after antiplatelet therapy.

CONCLUSIONS

The absolute number of GP IIb/IIIa receptors increases and platelets are not activated up to 12 hours after cessation of abciximab therapy. Treatment of STEMI patients undergoing PCI with a loading dose of clopidogrel reduces the percentage of active platelets but does not influence the CT.

Quantification of clopidogrel in human plasma by sensitive liquid chromatography/tandem mass spectrometry

A simple, sensitive and rapid high-performance liquid chromatography/positive electrospray ionization tandem mass spectrometry method was developed and validated for the assay of clopidogrel in human plasma. Following liquid-liquid extraction, the analytes were separated using an isocratic mobile phase on a reversed-phase column and analyzed by mass spectrometry in the multiple reaction monitoring mode using the respective [M+H](+) ions, m/z 322/212 for clopidogrel and m/z 264/154 for the internal standard. The assay exhibited a linear dynamic range of 5-6000 pg/mL for clopidogrel in human plasma. The lower limit of quantification was 5 pg/mL with a relative standard deviation of less than 8%. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. A run time of 2.5 min for each sample made it possible to analyze more than 400 human plasma samples per day. The validated method has been successfully used to analyze human plasma samples for application in pharmacokinetic, bioavailability or bioequivalence studies.

Endothelial action of thienopyridines and thienopyrimidinones in the isolated guinea pig heart

Antiplatelet thienopyridines (ticlopidine, clopidogrel) and their thienopyrimidinone congeners, induce prostacyclin-dependent thrombolysis in vivo. Here we tested whether thienopyridines (ticlopidine, clopidogrel, and its enantiomer without antiplatelet properties) and structurally related thienopyrimidinones release NO from coronary endothelium in the isolated guinea pig heart, perfused according to Langendorff technique. The involvement of endothelium-derived NO in coronary vasodilation induced by these agents was assessed by effect of L-N(G)-nitro-arginine methyl ester (L-NAME). In addition, effect of thienopyridines or thienopyrimidinones on nitrite accumulation in cultured endothelium was assayed. Tienopyridines (10-100 micromol L(-1)) and thienopyrimidinones (10-30 micromol L(-1)) produced concentration-dependent increase in coronary flow comparable to that induced by acetylcholine (0.1 micromol L(-1)) or bradykinin (3 nmol L(-1)) which was inhibited by L-NAME (by 50-70%) but not by indomethacin. Furthermore, thienopyridines and thienopyrimidinones caused NO release from cultured endothelial cells. In conclusion, both thienopyridines independently from their antiplatelet action and their thienopyrimidinone congeners that are devoid of antiplatelet action stimulate coronary endothelium to release NO. Endothelial action of these compounds merits further investigation.

The effect of long-term clopidogrel use on neointimal formation after percutaneous coronary intervention

OBJECTIVE

The purpose of this study was to evaluate the long term effect of clopidogrel-based antiplatelet therapy on neointimal formation.

METHODS

This study comprised 78 patients with typical stable angina pectoris or documented myocardial ischaemia, and with only one angiographic lesion in one native coronary artery undergoing successful stent implantation without predilatation with C-reactive protein levels < or =5 mg/l at 72 h after the procedure. All patients received dual antiplatelet therapy with 75 mg/day clopidogrel and 300 mg/day aspirin for four weeks. Clopidogrel was switched to isochronous placebo in half of the patients (n=39) at the end of the fourth week. This allocation was maintained for 20 weeks, and at week 24 of the study, coronary angiography and intravascular ultrasound imaging were performed again in all cases in order to evaluate the changes that had occurred in the in-stent neointimal formation; rates of restenosis were also recorded

RESULTS

At the end of the follow-up period, angiographic stenosis diameter and restenosis rates were smaller in the clopidogrel group than in the placebo group (23.3% versus 35.6%, p=0.05 and 5.12% versus 10.25%; p=0.03 respectively); the intravascular ultrasonographic neointimal cross sectional area was also smaller in the clopidogrel group (3.6 +/- 2.7 mm(2) versus 5.2 +/- 2.5 mm(2), p=0.03).

CONCLUSIONS

Long-term clopidogrel administration significantly reduced neointimal formation at the stent site as well as reducing major clinical events in patients who did not develop high-risk systemic inflammatory response after percutaneous coronary intervention.

Clopidogrel’s role in the management of atherosclerotic disease: a focus on acute coronary syndromes

Recent advances in our understanding of the role of the platelet in the atherosclerotic process beyond the acute formation of arterial blood clots, such as inflammation, have highlighted the role of antiplatelet agents as being much more than just 'blood thinners.' Some of the most important cardiovascular trials performed in the last 20 years have studied antiplatelet therapies. However, despite their long history, current global health implications and proven benefit, there remain substantial gaps in our understanding as to how to best utilize the limited number of antiplatelet agents available. This article will discuss the mechanism of action of the antiplatelet class known as thienopyridines, the pharmacodynamics and pharmacokinetics of the thienopyridine agent clopidogrel (Plavix, Bristol-Myers Squibb and Sanofi Pharmaceuticals) as well as the literature supporting its clinical benefits and areas of ongoing research that will help clarify the optimal utilization of clopidogrel for the treatment of cardiovascular disease.

Onset and extent of platelet inhibition by clopidogrel loading in patients undergoing elective coronary stenting: the Plavix Reduction Of New Thrombus Occurrence (PRONTO) trial

BACKGROUND

Despite the common practice of clopidogrel loading for coronary stenting, the time dependence and degree of platelet inhibition after this therapy are not well defined. We sought to establish an optimal clopidogrel dosing regimen for sustained platelet inhibition in stented patients.

METHODS AND RESULTS

Platelets were assessed by conventional aggregation with 5 micromol/L adenosine diphosphate (ADP), 1 microg/mL collagen (COLL), and 750 micromol/L arachidonic acid; whole blood aggregation by 1 microg/mL collagen (WBA); shear-induced closure time (CT); contractile force (CF); and expression of 9 surface receptors by flow cytometry in 100 patients undergoing elective stent placement without glycoprotein (GP) IIb/IIIa receptor antagonists. Blood was obtained at baseline and serially over 5 days poststenting after different clopidogrel loading regimens: 300 mg 24 hours before (Group A), 12 hours before (Group B), 3 to 6 hours before (Group C), and 75 mg at the time of intervention (Group D). Before stenting, ADP, COLL, CT, and WBA were reduced by clopidogrel loading (P <.05). CF was not affected by clopidogrel. Before stenting, GP IIb/IIIa expression increased in groups A through C (P <.05), whereas PECAM-1 and CD107a were reduced (P <.05). At 2 hours and 2 days poststenting, platelets, in general, exhibited an increase in activity that was most inhibited by clopidogrel loading. Clopidogrel inhibited GP Ib, platelet/endothelial cell adhesion molecule-1, CD 107a, CD 151, and GP IIb/IIIa expression at day 5 poststenting.

CONCLUSION

A 300 mg clopidogrel load given 3 to 24 hours before stenting inhibits platelets at the time of the procedure and reduces poststent activity more than a 75 mg dose given at the time of the procedure. The inhibition of adhesive molecule expression may also contribute an antithrombotic effect. Poststent activation of platelets may warrant higher periprocedural dosing.

Eptifibatide and abciximab exhibit equivalent antiplatelet efficacy in an experimental model of stenting in both healthy volunteers and patients with coronary artery disease

Platelet deposition and aggregation are the major determinants of acute thrombosis in coronary stents. We aimed to compare the antiplatelet efficacy of different treatments--glycoprotein (Gp) IIb/IIIa inhibitors and conventional antiaggregants--in an experimental model for stenting. Blood samples were obtained from patients with coronary artery disease (n = 15) and healthy volunteers (n = 8) and incubated either with eptifibatide (2.0 microg/ml), abciximab (3.0 microg/ml), indomethacin (15 microg/ml), or saline. Platelet adenosine diphosphate-induced aggregation in whole blood was assessed for all groups. Blood was also tested in an experimental circulation model containing metallic probes, on which platelet deposition in shear flow conditions was assessed by means of fluorescent-labeled platelet-specific (anti-GpIIIa and Ib) antibodies. Eptifibatide and abciximab, in comparison with indomethacin and no treatment, significantly reduced platelet aggregation (0, 0, 4, and 3 arbitrary units [AU], respectively; p < 0.001), anti-GpIIIa (2.25, 1.83, 11.24, and 13.42 counts per second [cps]/mg, respectively; p < 0.001), and anti-GpIb binding (0.61, 0.61, 1.00, and 1.83 cps/mg, respectively; p < 0.001). Anti-GpIIIa and anti-GpIb binding were significantly correlated (R = 0.36; p < 0.01). Patients showed a higher anti-GpIIIa, but not anti-GpIb binding, than controls (8.43 versus 3.33 cps/mg; p < 0.01), irrespective of treatment. In conclusion, eptifibatide and abciximab show equivalent in vitro antiplatelet efficacy, superior to that of indomethacin. Given the occurrence of GpIIb/IIIa platelet overexpression in the course of coronary artery disease, an extended use of GpIIb/IIIa inhibitors may be proposed to prevent acute thrombosis during routine coronary stenting.

Clopidogrel: a review of its use in the prevention of atherothrombosis

Clopidogrel is an ADP receptor antagonist that is indicated for the reduction of atherosclerotic events including myocardial infarction, ischaemic stroke and vascular death in patients with atherosclerosis manifested by recent stroke, myocardial infarction or established peripheral vascular disease. In the 19 185 patients enrolled in the multicentre, randomised double-blind CAPRIE study, the annual risk of the combined end-point of ischaemic stroke, myocardial infarction and death from vascular disease (vascular death) was significantly lower during treatment with clopidogrel 75 mg/day than aspirin 325 mg/day [5.3 vs 5.8%/year, respectively; relative risk reduction (RRR) 8.7%, p = 0.043] after a mean follow-up of 1.9 years. Clopidogrel provided even greater reductions in the risk of recurrent ischaemic events than aspirin in patients with a history of coronary artery bypass surgery, diabetes mellitus and in those receiving concomitant lipid-lowering therapy. Moreover there was a significant reduction in the incidence of hospitalisation in patients treated with clopidogrel. In a patient population (Saskatchewan, Canada) with a greater risk of ischaemic events than the CAPRIE study population, the number of patients needed to be treated with clopidogrel to prevent 1 ischaemic event was estimated to be 70 (vs 200 in the CAPRIE study). In randomised trials and registry surveys, clopidogrel 75 mg/day plus aspirin had similar efficacy (as measured by adverse cardiac outcomes) to ticlopidine 250mg twice daily plus aspirin during the 30 days after placement of intracoronary stents. Tolerability of clopidogrel was significantly better than ticlopidine in the randomised, double-blind CLASSICS study. Among patients treated with clopidogrel or aspirin in the CAPRIE study, the overall gastrointestinal tolerability of clopidogrel was generally better than that of aspirin; the frequency of gastrointestinal haemorrhage was significantly lower among patients treated with clopidogrel than aspirin. Diarrhoea, rash and pruritus were significantly more common with clopidogrel than aspirin.

CONCLUSION

Clopidogrel was significantly more effective than aspirin in the prevention of vascular events (ischaemic stroke, myocardial infarction or vascular death) [corrected] in patients with atherothrombotic disease manifested by recent myocardial infarction, recent ischaemic stroke or symptomatic peripheral arterial occlusive disease [corrected] in the CAPRIE study. The overall tolerability profile of the drug was similar to that of aspirin, although gastrointestinal haemorrhage occurred significantly less often in clopidogrel recipients. The drug is widely used in combination with aspirin for the prevention of atherothrombosis after placement of intravascular stents, and available data suggest that this combination is as effective as ticlopidine plus aspirin for this indication.