Antiplatelet agents aspirin and clopidogrel are hydrolyzed by distinct carboxylesterases, and clopidogrel is transesterificated in the presence of ethyl alcohol

Safety, tolerability, pharmacokinetics and pharmacodynamics of milvexian with aspirin and/or clopidogrel in healthy participants

Milvexian, an oral activated Factor XI (FXIa) inhibitor, is in clinical studies where it may be combined with antiplatelet agents, including aspirin and/or clopidogrel, to prevent thromboembolic diseases. This phase I trial assessed safety, pharmacokinetics, and pharmacodynamics of milvexian coadministration with aspirin and/or clopidogrel in healthy participants through 3 drug-drug interaction studies using a 3-period, 3-treatment, crossover design. A total of 113 participants were randomized to receive milvexian (200 mg; twice daily for 5 days) or matched placebo coadministered with once-daily aspirin (325 mg for 5 days) and/or clopidogrel (Day 1: 300 mg; Days 2-5: 75 mg). Milvexian was safe and well tolerated, with and without aspirin and/or clopidogrel. Eight mild bleeding adverse events (AEs) were reported in 5 of 113 participants across various treatment arms. Peak and total exposures of milvexian were similar with or without clopidogrel and/or aspirin. Exposure-dependent prolongation of activated partial thromboplastin time and reduction of FXI clotting activity by milvexian were similar with coadministration of aspirin and/or clopidogrel. Milvexian, with or without coadministration of aspirin and/or clopidogrel, did not affect bleeding time or platelet aggregation. Administration of milvexian alone or with aspirin and/or clopidogrel was safe and well tolerated without increased incidence of AEs, including bleeding. Pharmacokinetic and pharmacodynamic effects of milvexian, including bleeding time, were similar with or without aspirin and/or clopidogrel.ClinicalTrials.gov Identifier: NCT03698513.

Role of carboxylesterase and arylacetamide deacetylase in drug metabolism, physiology, and pathology

Carboxylesterases (CES1 and CES2) and arylacetamide deacetylase (AADAC), which are expressed primarily in the liver and/or gastrointestinal tract, hydrolyze drugs containing ester and amide bonds in their chemical structure. These enzymes often catalyze the conversion of prodrugs, including the COVID-19 drugs remdesivir and molnupiravir, to their pharmacologically active forms. Information on the substrate specificity and inhibitory properties of these enzymes, which would be useful for drug development and toxicity avoidance, has accumulated. Recently,in vitroandin vivostudies have shown that these enzymes are involved not only in drug hydrolysis but also in lipid metabolism. CES1 and CES2 are capable of hydrolyzing triacylglycerol, and the deletion of their orthologous genes in mice has been associated with impaired lipid metabolism and hepatic steatosis. Adeno-associated virus-mediated human CES overexpression decreases hepatic triacylglycerol levels and increases fatty acid oxidation in mice. It has also been shown that overexpression of CES enzymes or AADAC in cultured cells suppresses the intracellular accumulation of triacylglycerol. Recent reports indicate that AADAC can be up- or downregulated in tumors of various organs, and its varied expression is associated with poor prognosis in patients with cancer. Thus, CES and AADAC not only determine drug efficacy and toxicity but are also involved in pathophysiology. This review summarizes recent findings on the roles of CES and AADAC in drug metabolism, physiology, and pathology.

In Silico Study of Camptothecin-Based Pro-Drugs Binding to Human Carboxylesterase 2

Pro-drugs, which ideally release their active compound only at the site of action, i.e., in a cancer cell, are a promising approach towards an increased specificity and hence reduced side effects in chemotherapy. A popular form of pro-drugs is esters, which are activated upon their hydrolysis. Since carboxylesterases that catalyse such a hydrolysis reaction are also abundant in normal tissue, it is of great interest whether a putative pro-drug is a probable substrate of such an enzyme and hence bears the danger of being activated not just in the target environment, i.e., in cancer cells. In this work, we study the binding mode of carboxylesters of the drug molecule camptothecin, which is an inhibitor of topoisomerase I, of varying size to human carboxylesterase 2 (HCE2) by molecular docking and molecular dynamics simulations. A comparison to irinotecan, known to be a substrate of HCE2, shows that all three pro-drugs analysed in this work can bind to the HCE2 protein, but not in a pose that is well suited for subsequent hydrolysis. Our data suggest, moreover, that for the irinotecan substrate, a reactant-competent pose is stabilised once the initial proton transfer from the putative nucleophile Ser202 to the His431 of the catalytic triad has already occurred. Our simulation work also shows that it is important to go beyond the static models obtained from molecular docking and include the flexibility of enzyme-ligand complexes in solvents and at a finite temperature. Under such conditions, the pro-drugs studied in this work are unlikely to be hydrolysed by the HCE2 enzyme, indicating a low risk of undesired drug release in normal tissue.

Advances and Perspectives in methods for identifying high platelet reactivity

Antiplatelet therapy is the foundational treatment for the prevention and treatment of coronary and cerebrovascular ischemic events in patients with coronary heart disease, ischemic stroke, and transient ischemic attack (TIA). However, with more and more studies reporting an increased risk of thrombosis in some patients due to poor response to therapeutic agents, the selection of appropriate P2Y12 inhibitors has become a major challenge that needs to be addressed urgently. Currently, commonly used oral P2Y12 inhibitors include clopidogrel, ticagrelor, and prasugrel. Assessing patients' risk factors before the development of treatment regimens by effectively predicting the risk of high platelet reactivity with specific P2Y12 inhibitors in advance to avert the occurrence of major adverse cardiovascular and cerebrovascular events (MACCE) is the key point to the problem. Up to now, methods available for predicting platelet reactivity include genetic testing, platelet function testing, and risk scores. This review provides a summarization of the existent available identification methods and analyzes the advantages and drawbacks of different methods in specific clinical settings, intending to guide the rational clinical application of P2Y12 receptor inhibitors.

Influence of CYP450 Enzymes and ABCB1 Polymorphisms on Clopidogrel Response in Moroccan Patients with Acute Coronary Syndromes

Introduction

Clopidogrel is an antiplatelet prodrug primarily prescribed to prevent or treat acute coronary syndrome (ACS) or acute ischemic stroke (IS), polymorphisms of genes encoding cytochrome P-450 (CYP) and P-glycoprotein transporter, could affect the efficiency of clopidogrel absorption and biotransformation, especially during the first critical hours following its administration.

Methods

The present study was designed to investigate the potential association of clopidogrel responsiveness and 14 polymorphisms in the genes encoding the CYPs (CYP2C9, 2C19, 3A4, 3A5, 1A2, and 2B6), the ATP binding cassette subfamily B member 1 (ABCB1). Platelet aggregation activity was measured after 8h of 300mg clopidogrel administration for fifty-five ACS patients.

Results

There was no significant association between polymorphism of the studied CYPs and clopidogrel responsiveness (P>0.05). The frequency of the ABCB1 3435 T allele in clopidogrel non-responders was higher (78.9%) compared to responders (52.8%), but this difference was not significant (P=0.057). Demographic characteristics, comorbidities, concomitant treatments were not associated with clopidogrel response.

Discussion

There was no effect of the studied genetic variations and demographic factors on the platelet activity of clopidogrel in Moroccan ACS patients.

Aspirin microcrystals deposited on high-density microneedle tips for the preparation of soluble polymer microneedles

To reduce mucosal damage in the gastrointestinal tract caused by aspirin, aspirin microcrystals were loaded in soluble polymeric microneedle (MN) tips. Aspirin was prepared into aspirin microcrystals by jet milling. Aspirin microcrystals with particle sizes of 0.5-5 μm were loaded on MN tips with a height of 250 µm or 300 µm. The aspirin microcrystals suspended in a polymer solution were concentrated in the MN tips under negative pressure. The aspirin microcrystals had high stability in the MNs since they were not dissolved in solution during the fabrication process. The MN patch packaged in an aluminum-plastic bag containing silica gel desiccant can be stored at 4 °C. The MN tips implanted in the skin of Institute of Cancer Research (ICR) mice dissolved within 30 min. Isolated porcine ear skin was punctured by MNs with heights of 300 μm and 250 μm to depths of 130 μm and 90 μm, respectively. The fluorescent red (FR) release from MNs reached 98.59% within 24 h. The MNs delivered aspirin microcrystals to the epidermis and dermis, providing a smooth plasma concentration in rats. The MNs loaded with aspirin microcrystals did not evoke primary irritation on the dorsal skin of Japanese white rabbits. In summary, MNs loaded with aspirin microcrystals provide a new approach to improve the stability of aspirin in MN patches.

Hormetic effects of EGC and EGCG on CES1 activity and its rescue from oxidative stress in rat liver S9

Carboxylesterase 1 (CES1) is a hydrolytic enzyme that plays an important role in the activation or deactivation of many therapeutic agents, thus affecting their pharmacokinetic and pharmacodynamic outcomes. Using rat liver S9 as an enzyme source and enalapril as a CES1 substrate, the present study examined effects of a number of flavonoids on the formation of enalaprilat (the active form of enalapril) produced by CES1-mediated hydrolysis. While a majority of flavonoids tested showed inhibition on CES1, an unexpected hormetic effect was observed for epigallocatechin (EGC) and epigallocatechin gallate (EGCG), i.e., stimulatory effect at low concentrations and enzyme inhibition at high concentrations. Further experiments revealed that oxidative stress caused by hydrogen peroxide, arachidonic acid plus iron, and oxidized low density lipoproteins (oxLOL) reduced CES1 activity in rat liver S9 and the loss of CES1 enzyme activity could be rescued largely by EGC or EGCG. In contrast, such effects were minimal in human liver S9, probably due to the presence of a higher ratio of reduced vs oxidized forms of glutathione. The above findings suggest that the polyphenolic nature of EGC or EGCG might be responsible for rescuing CES1 activity under oxidative stress. Because of the importance of CES1 in drug activation or deactivation and rat liver S9 as a versatile in vitro system used for drug metabolism studies and drug safety assessment, caution should be exercised to avoid potential biases for data interpretation and decision making when CES1 activity in rat liver S9 is evaluated with dependency on experimental conditions.

Viral target and metabolism-based rationale for combined use of recently authorized small molecule COVID-19 medicines: Molnupiravir, nirmatrelvir, and remdesivir

The COVID-19 pandemic remains a major health concern worldwide, and SARS-CoV-2 is continuously evolving. There is an urgent need to identify new antiviral drugs and develop novel therapeutic strategies. Combined use of newly authorized COVID-19 medicines including molnupiravir, nirmatrelvir, and remdesivir has been actively pursued. Mechanistically, nirmatrelvir inhibits SARS-CoV-2 replication by targeting the viral main protease (Mpro ), a critical enzyme in the processing of the immediately translated coronavirus polyproteins for viral replication. Molnupiravir and remdesivir, on the other hand, inhibit SARS-CoV-2 replication by targeting RNA-dependent RNA-polymerase (RdRp), which is directly responsible for genome replication and production of subgenomic RNAs. Molnupiravir targets RdRp and induces severe viral RNA mutations (genome), commonly referred to as error catastrophe. Remdesivir, in contrast, targets RdRp and causes chain termination and arrests RNA synthesis of the viral genome. In addition, all three medicines undergo extensive metabolism with strong therapeutic significance. Molnupiravir is hydrolytically activated by carboxylesterase-2 (CES2), nirmatrelvir is inactivated by cytochrome P450-based oxidation (e.g., CYP3A4), and remdesivir is hydrolytically activated by CES1 but covalently inhibits CES2. Additionally, remdesivir and nirmatrelvir are oxidized by the same CYP enzymes. The distinct mechanisms of action provide strong rationale for their combined use. On the other hand, these drugs undergo extensive metabolism that determines their therapeutic potential. This review discusses how metabolism pathways and enzymes involved should be carefully considered during their combined use for therapeutic synergy.

Bioconversion and P-gp-Mediated Transport of Depot Fluphenazine Prodrugs after Intramuscular Injection

Fluphenazine (FPZ) decanoate, an ester-type prodrug formulated as a long-acting injection (LAI), is used in the treatment of schizophrenia. FPZ enanthate was also developed as an LAI formulation, but is no longer in use clinically because of the short elimination half-life of FPZ, the parent drug, after intramuscular injection. In the present study, the hydrolysis of FPZ prodrugs was evaluated in human plasma and liver to clarify the reason for this difference in elimination half-lives. FPZ prodrugs were hydrolyzed in human plasma and liver microsomes. The rate of hydrolysis of FPZ enanthate in human plasma and liver microsomes was 15-fold and 6-fold, respectively, faster than that of FPZ decanoate. Butyrylcholinesterase (BChE) and human serum albumin (HSA) present in human plasma, and two carboxylesterase (CES) isozymes, hCE1 and hCE2, expressed in ubiquitous organs including liver, were mainly responsible for the hydrolysis of FPZ prodrugs. FPZ prodrugs may not be bioconverted in human skeletal muscle at the injection site because of lack of expression of BChE and CESs in muscle. Interestingly, although FPZ was a poor substrate for human P-glycoprotein, FPZ caproate was a good substrate. In conclusion, it is suggested that the shorter elimination half-life of FPZ following administration of FPZ enanthate compared with FPZ decanoate can be attributed to the more rapid hydrolysis of FPZ enanthate by BChE, HSA and CESs.

Transesterification of Indazole-3-carboxamide Synthetic Cannabinoids: Identification of Metabolite Biomarkers for Diagnosing Co-abuse of 5F-MDMB-PINACA and Alcohol

Concurrent use of alcohol with synthetic cannabinoids (SCs) has been widely recorded among drug abusers. The susceptibilities of three indazole-3-carboxamide type SCs with methyl ester moiety, 5F-MDMB-PINACA, 5F-MMB-PINACA, and MMB-FUBINACA, to transesterification in the presence of ethanol warranted further investigation in view of probable augmented toxicity. In vitro metabolite identification experiments were first performed using human liver microsomes (HLMs) to characterize the novel metabolites of the three parent SCs in the presence of ethanol. Formation of transesterified metabolite, hydrolyzed metabolite, and several oxidative metabolites in HLM in the presence of alcohol was further determined for each parent SC and the respective ethyl ester analog, 5F-EDMB-PINACA, 5F-EMB-PINACA, and EMB-FUBINACA, to quantitatively elucidate transesterification and hydrolysis activities. Our results suggested that all three SCs undergo carboxylesterase-mediated transesterification to their respective ethyl ester analog in the presence of ethanol, which was incubation time- and ethanol concentration-dependent. Each ethyl ester metabolite was sequentially and readily metabolized to novel oxidative metabolites with the intact ethyl ester moiety and the same hydrolyzed metabolite as derived from its parent SC. A smaller extent of transesterification was non-enzymatically driven. Notably, we proposed 5F-EDMB-PINACA oxidative defluorination metabolite as the biomarker for diagnosing the potential co-abuse of 5F-MDMB-PINACA and alcohol. Due to the comparable pharmacological activities between each SC and its ethyl ester metabolite, augmented toxicity associated with co-abuse of SCs and alcohol is probable and deserves further investigation.

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.

Dissolvable polymeric microneedles loaded with aspirin for antiplatelet aggregation

To reduce mucosal damage in the gastrointestinal tract caused by aspirin, we developed a dissolvable polymeric microneedle (MN) patch loaded with aspirin. Biodegradable polymers provide mechanical strength to the MNs. The MN tips punctured the cuticle of the skin and dissolved when in contact with the subcutaneous tissue. The aspirin in the MN patch is delivered continuously through an array of micropores created by the punctures, providing a stable plasma concentration of aspirin. The factors affecting the stability of aspirin during MNs fabrication were comprehensively analyzed, and the hydrolysis rate of aspirin in the MNs was less than 2%. Compared to oral administration, MN administration not only had a smoother plasma concentration curve but also resulted in a lower effective dose of antiplatelet aggregation. Aspirin-loaded MNs were mildly irritating to the skin, causing only slight erythema on the skin and recovery within 24 h. In summary, aspirin-loaded MNs provide a new method to reduce gastrointestinal adverse effects in patients requiring aspirin regularly.

Alcohol inhibits the metabolism of dimethyl fumarate to the active metabolite responsible for decreasing relapse frequency in the treatment of multiple sclerosis

Dimethyl fumarate (DMF) is a first-line prodrug for the treatment of relapsing-remitting multiple sclerosis (RRMS) that is completely metabolized to monomethyl fumarate (MMF), the active metabolite, before reaching the systemic circulation. Its metabolism has been proposed to be due to ubiquitous esterases in the intestines and other tissues, but the specific enzymes involved are unknown. We hypothesized based on its structure and extensive presystemic metabolism that DMF would be a carboxylesterase substrate subject to interaction with alcohol. We sought to determine the enzymes(s) responsible for the extensive presystemic metabolism of DMF to MMF and the effect of alcohol on its disposition by conducting metabolic incubation studies in human recombinant carboxylesterase-1 (CES1), carboxylesterase-2 (CES2) and human intestinal microsomes (HIM), and by performing a follow-up study in an in vivo mouse model. The in vitro incubation studies demonstrated that DMF was only metabolized to MMF by CES1. Consistent with the incubation studies, the mouse pharmacokinetic study demonstrated that alcohol decreased the maximum concentration and area-under-the-curve of MMF in the plasma and the brain after dosing with DMF. We conclude that alcohol may markedly decrease exposure to the active MMF metabolite in the plasma and brain potentially decreasing the effectiveness of DMF in the treatment of RRMS.

The COVID-19 Oral Drug Molnupiravir Is a CES2 Substrate: Potential Drug-Drug Interactions and Impact of CES2 Genetic Polymorphism In Vitro

Molnupiravir is one of the two coronavirus disease 2019 (COVID-19) oral drugs that were recently granted the emergency use authorization by the Food and Drug Administration (FDA). Molnupiravir is an ester and requires hydrolysis to exert antiviral activity. Carboxylesterases constitute a class of hydrolases with high catalytic efficiency. Humans express two major carboxylesterases (CES1 and CES2) that differ in substrate specificity. Based on the structural characteristics of molnupiravir, this study was performed to test the hypothesis that molnupiravir is preferably hydrolyzed by CES2. Several complementary approaches were used to test this hypothesis. As many as 24 individual human liver samples were tested and the hydrolysis of molnupiravir was significantly correlated with the level of CES2 but not CES1. Microsomes from the intestine, kidney, and liver, but not lung, all rapidly hydrolyzed molnupiravir and the magnitude of hydrolysis was related closely to the level of CES2 expression among these organs. Importantly, recombinant CES2 but not CES1 hydrolyzed molnupiravir, collectively establishing that molnupiravir is a CES2-selective substrate. In addition, several CES2 polymorphic variants (e.g., R180H) differed from the wild-type CES2 in the hydrolysis of molnupiravir. Molecular docking revealed that wild-type CES2 and its variant R180H used different sets of amino acids to interact with molnupiravir. Furthermore, molnupiravir hydrolysis was significantly inhibited by remdesivir, the first COVID-19 drug granted the full approval by the FDA. The results presented raise the possibility that CES2 expression and genetic variation may impact therapeutic efficacy in clinical situations and warrants further investigation. SIGNIFICANCE STATEMENT: COVID-19 remains a global health crisis, and molnupiravir is one of the two recently approved oral COVID-19 therapeutics. In this study, we have shown that molnupiravir is hydrolytically activated by CES2, a major hydrolase whose activity is impacted by genetic polymorphic variants, disease mediators, and many potentially coadministered medicines. These results presented raise the possibility that CES2 expression and genetic variation may impact therapeutic efficacy in clinical situations and warrants further investigation.

Effect of alcohol exposure on the efficacy and safety of tenofovir alafenamide fumarate, a major medicine against human immunodeficiency virus

Human immunodeficiency virus (HIV) continues to be a major health concern. AIDS-related deaths (acquired immunodeficiency syndrome) have decreased recently, but chronic liver disease is now a major cause of mortality among HIV patients. Widespread alcohol use is recognized to be a major contributing factor. Tenofovir alafenamide fumarate (TAF), one of the most used HIV drugs, requires hydrolysis followed by phosphorylation to produce tenofovir diphosphate, the ultimate anti-HIV metabolite. Carboxylesterase-1 (CES1), established to hydrolyze TAF, is known to catalyze transesterification in the presence of ethanol. The aim of the study was to test the hypothesis that metabolism-based interactions between TAF and ethanol negatively impact both efficacy and safety of TAF. To test this hypothesis, the metabolism of TAF was determined in human primary hepatocytes and with a large number of human liver samples (S9 fractions) in the presence or absence of ethanol. The metabolism was monitored by LC-MS/MS (liquid chromatography with tandem mass spectrometry) and the level of CES1 or CES2 was determined by Western blotting. Consistent with the hypothesis, TAF underwent transesterification in the presence of ethanol accompanied by decreased hydrolysis. The formation of tenofovir diphosphate (the therapeutically active metabolite) was significantly decreased. In addition, TAF but not its hydrolytic metabolite, was found to increase intracellular lipid retention, and the increase was enhanced by ethanol. These findings conclude that alcohol consumption, beyond commonly accepted poor adherence to HIV medications, directly impacts the efficacy and safety of TAF.

Major implications of single nucleotide polymorphisms in human carboxylesterase 1 on substrate bioavailability

The number of studies and reviews conducted for the Carboxylesterase gene is limited in comparison with other enzymes. Carboxylesterase (CES) gene or human carboxylesterases (hCES) is a multigene protein belonging to the α/β-hydrolase family. Over the last decade, two major carboxylesterases (CES1 and CES2), located at 16q13-q22.1 on human chromosome 16 have been extensively studied as important mediators in the metabolism of a wide range of substrates. hCES1 is the most widely expressed enzyme in humans, and it is found in the liver. In this review, details regarding CES1 substrates include both inducers (e.g. Rifampicin) and inhibitors (e.g. Enalapril, Diltiazem, Simvastatin) and different types of hCES1 polymorphisms (nsSNPs) such as rs2244613 and rs71647871. along with their effects on various CES1 substrates were documented. Few instances where the presence of nsSNPs exerted a positive influence on certain substrates which are hydrolyzed via hCES1, such as anti-platelets like Clopidogrel when co-administered with other medications such as angiotensin-converting enzyme (ACE) inhibitors were also recorded. Remdesivir, an ester prodrug is widely used for the treatment of COVID-19, being a CES substrate, it is a potent inhibitor of CES2 and is hydrolyzed via CES1. The details provided in this review could give a clear-cut idea or information that could be used for further studies regarding the safety and efficacy of CES1 substrate.

Inhibition of Radix Scutellariae flavones on carboxylesterase mediated activations of prodrugs

AIMS

Carboxylesterase (CES) plays an essential role in the hydrolysis of ester prodrugs. Our study explored the inhibitions of Radix Scutellariae flavones, including baicalein (B), baicalin (BG), wogonin (W), wogonoside (WG), oroxylin A (OXA) and oroxylin A-7-O-glucuronide (OAG), on CES-mediated hydrolysis of seven prodrugs (capecitabine, clopidogrel, mycophenolate mofetil, dabigatran etexilate, acetylsalicylic acid, prasugrel and irinotecan).

MAIN METHODS

In vitro screenings were developed by incubating the flavones with prodrugs in rat plasma, intestine S9 and liver S9. Docking simulations were conducted using AMDock v1.5.2. In vivo evaluations were performed in rats co-administered with the selected flavone and prodrug via oral gavage/intravenous administration for five consecutive days.

KEY FINDINGS

The in vitro investigation showed that B and OXA demonstrated strongest inhibitions on the hydrolysis of irinotecan followed by dabigatran in rat plasma, intestine S9 and liver S9. Consistent results showed in the molecular docking analyses. Additionally, in rats receiving irinotecan, B/OXA intravenous and oral pre-treatments both led to reduction trends on the active metabolite SN-38 formation in plasma. Besides, significant decreases of SN-38/irinotecan plasma concentration ratios were found in the B/OXA oral pre-treatment group with quicker and stronger inhibition potential in OXA pre-treatment than that from B pre-treatment. OXA oral pre-treatment was also found to be able to significantly inhibit intestinal CES2 activities at 0.5 h and 5 h after irinotecan administration.

SIGNIFICANCE

Our current findings for the first time alert on potential CES-mediated HDIs between RS flavones and prodrugs, which provide a constructive information referring to rational drug combinations in clinical practice.

Pleiotropic effects of clopidogrel

Clopidogrel is a widely prescribed prodrug with anti-thrombotic activity through irreversible inhibition of the P2Y₁₂ receptor on platelets. It is FDA-approved for the clinical management of thrombotic diseases like unstable angina, myocardial infarction, stroke, and during percutaneous coronary interventions. Hepatic clopidogrel metabolism generates several distinct metabolites. Only one of these metabolites is responsible for inhibiting the platelet P2Y₁₂ receptor. Importantly, various non-hemostatic effects of clopidogrel therapy have been described. These non-hemostatic effects are perhaps unsurprising, as P2Y₁₂ receptor expression has been reported in multiple tissues, including osteoblasts, leukocytes, as well as vascular endothelium and smooth muscle. While the "inactive" metabolites have been commonly thought to be biologically inert, recent findings have uncovered P2Y₁₂ receptor-independent effects of clopidogrel treatment that may be mediated by understudied metabolites. In this review, we summarize both the P2Y₁₂ receptor-mediated and non-P2Y₁₂ receptor-mediated effects of clopidogrel and its metabolites in various tissues.

Ilaprazole and Clopidogrel Resistance in Acute Stroke Patients

Clopidogrel, an antiplatelet agent used for secondary prevention of cerebrovascular diseases, is often taken with proton pump inhibitors (PPIs). Generally, the combined use of clopidogrel and PPIs causes adverse drug–drug interactions. VerifyNow is a quick and convenient method to confirm clopidogrel resistance (CR), which compromises adequate antithrombotic effects. We aimed to confirm CR, identify its factors, and determine the influence of the combination of ilaprazole and clopidogrel on clopidogrel using VerifyNow. In this retrospective study, we examined patients who were receiving clopidogrel after three months, starting within one week from the onset of cerebral infarction symptoms. Clinical records, imaging records, and diagnostic laboratory results, including P2Y12 reaction units (PRU), were compared and analyzed to check for CR. Additionally, the groups treated with either both ilaprazole and clopidogrel or with medications other than ilaprazole were comparatively analyzed. CR was defined as a PRU ≥240 after clopidogrel for three months. Among factors influencing CR by affecting clopidogrel metabolism, positive statistical correlations with age and alcohol consumption were confirmed. The diagnostic tests revealed a lower glomerular filtration rate and platelet count of the CR-positive group. This finding proved that the combination therapy of ilaprazole and clopidogrel is safe, as it does not interfere with the metabolism of clopidogrel.

P2Y12 Antagonists in Cardiovascular Disease—Finding the Best Balance Between Preventing Ischemic Events and Causing Bleeding

Dual antiplatelet therapy comprising of aspirin and oral P2Y₁₂ receptor antagonists are an established cornerstone of therapy in acute coronary syndromes and percutaneous coronary intervention. As a result, the platelet P2Y₁₂ receptor remains a key therapeutic target in cardiovascular medicine since pharmacological antagonists were first developed in the 1990’s. With a greater understanding of platelet biology and the role played by the P2Y₁₂ receptor in the amplification of platelet activation and thrombus formation, there has been progressive refinement in the development of P2Y₁₂ receptor antagonists with greater potency and consistency of antiplatelet effect. However, challenges remain in the utilization of these agents particularly in balancing the need for greater protection from ischemic events whilst minimizing the bleeding risk and present a real opportunity for the institution of individualized medicine. Future drug developments will provide clinicians with greater avenues to achieve this.

Simultaneous determination of clopidogrel, 2-oxo-clopidogrel, and the thiol metabolite of clopidogrel in human plasma by LC-MS/MS

Clopidogrel is a pro-drug which needs two-step metabolism to produce the active thiol metabolite. This study aimed to explore an efficient method to simultaneously determine the plasma clopidogrel, 2-oxo-clopidogrel (2-Oxo-CLP), and the clopidogrel active metabolite (CAM). A high-throughput liquid chromatography tandem mass spectrometry (LC-MS/MS) was therefore developed. The analytes were extracted from plasma by using methyl tert-butyl ether (MTBE). Chromatographic separation was performed on a C18 column under an isocratic elution, accompanied with acetonitrile and deionized water containing 0.1% formic acid. After optimizing the condition of LC-MS/MS, a stable linearity was observed in the standard curves over the concentration ranges of 0.05 to 50.0 ng/mL for clopidogrel, 0.5 to 50.0 ng/mL for 2-Oxo-CLP, and 0.5 to 100 ng/mL for clopidogrel active metabolite derivative (CAMD). The retention time was 4.78 minutes, 3.79 minutes, 3.59 minutes, and 4.82 minutes for clopidogrel, 2-Oxo-CLP, CAMD, and internal standard, respectively. Both the relative standard deviation and the relative error were within the requirement of operating criteria. No significant degradation of clopidogrel, 2-Oxo-CLP, and CAMD occurred under different storage conditions. This method was successfully validated in 3 patients with coronary artery disease. The results showed that the current LC-MS/MS method was efficient for simultaneously detecting clopidogrel, 2-Oxo-CLP, and CAM with fine linearity, accuracy, precision, and stability.

The nucleoside antiviral prodrug remdesivir in treating COVID-19 and beyond with interspecies significance

Infectious pandemics result in hundreds and millions of deaths, notable examples of the Spanish Flu, the Black Death and smallpox. The current pandemic, caused by SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2), is unprecedented even in the historical term of pandemics. The unprecedentedness is featured by multiple surges, rapid identification of therapeutic options and accelerated development of vaccines. Remdesivir, originally developed for Ebola viral disease, is the first treatment of COVID-19 (Coronavirus disease 2019) approved by the United States Food and Drug Administration. As demonstrated by in vitro and preclinical studies, this therapeutic agent is highly potent with a broad spectrum activity against viruses from as many as seven families even cross species. However, randomized controlled trials have failed to confirm the efficacy and safety. Remdesivir improves some clinical signs but not critical parameters such as mortality. This antiviral agent is an ester/phosphorylation prodrug and excessive hydrolysis which increases cellular toxicity. Remdesivir is given intravenously, leading to concentration spikes and likely increasing the potential of hydrolysis-based toxicity. This review has proposed a conceptual framework for improving its efficacy and minimizing toxicity not only for the COVID-19 pandemic but also for future ones caused by remdesivir-sensitive viruses.

Pharmacokinetics and Pharmacodynamics of Approved and Investigational P2Y12 Receptor Antagonists

Coronary artery disease remains the major cause of mortality worldwide. Antiplatelet drugs such as acetylsalicylic acid and P2Y12 receptor antagonists are cornerstone treatments for the prevention of thrombotic events in patients with coronary artery disease. Clopidogrel has long been the gold standard but has major pharmacological limitations such as a slow onset and long duration of effect, as well as weak platelet inhibition with high inter-individual pharmacokinetic and pharmacodynamic variability. There has been a strong need to develop potent P2Y12 receptor antagonists with more favorable pharmacological properties. Prasugrel and ticagrelor are more potent and have a faster onset of action; however, they have shown an increased bleeding risk compared with clopidogrel. Cangrelor is highly potent and has a very rapid onset and offset of effect; however, its indication is limited to P2Y12 antagonist-naïve patients undergoing percutaneous coronary intervention. Two novel P2Y12 receptor antagonists are currently in clinical development, namely vicagrel and selatogrel. Vicagrel is an analog of clopidogrel with enhanced and more efficient formation of its active metabolite. Selatogrel is characterized by a rapid onset of action following subcutaneous administration and developed for early treatment of a suspected acute myocardial infarction. This review article describes the clinical pharmacology profile of marketed P2Y12 receptor antagonists and those under development focusing on pharmacokinetic, pharmacodynamic, and drug-drug interaction liability.

Non-P450 Drug-Metabolizing Enzymes: Contribution to Drug Disposition, Toxicity, and Development

Most clinically used drugs are metabolized in the body via oxidation, reduction, or hydrolysis reactions, which are considered phase I reactions. Cytochrome P450 (P450) enzymes, which primarily catalyze oxidation reactions, contribute to the metabolism of over 50% of clinically used drugs. In the last few decades, the function and regulation of P450s have been extensively studied, whereas the characterization of non-P450 phase I enzymes is still incomplete. Recent studies suggest that approximately 30% of drug metabolism is carried out by non-P450 enzymes. This review summarizes current knowledge of non-P450 phase I enzymes, focusing on their roles in controlling drug efficacy and adverse reactions as an important aspect of drug development. Expected final online publication date for the Annual Review of Pharmacology and Toxicology, Volume 62 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Human carboxylesterases and fluorescent probes to image their activity in live cells

Human carboxylesterases (CESs) are serine hydrolases that are responsible for the phase I metabolism of an assortment of ester, amide, thioester, carbonate, and carbamate containing drugs. CES activity is known to be influenced by a variety of factors including single nucleotide polymorphisms, alternative splicing, and drug-drug interactions. These different factors contribute to interindividual variability of CES activity which has been demonstrated to influence clinical outcomes among people treated with CES-substrate therapeutics. Detailed exploration of the factors that influence CES activity is emerging as an important area of research. The use of fluorescent probes with live cell imaging techniques can selectively visualize the real-time activity of CESs and have the potential to be useful tools to help reveal the impacts of CES activity variations on human health. This review summarizes the properties of the five known human CESs including factors reported to or that could potentially influence their activity before discussing the design aspects and use considerations of CES fluorescent probes in general in addition to highlighting several well-characterized probes.

Recent developments in predicting CYP-independent metabolism

As lead optimization efforts have successfully reduced metabolic liabilities due to cytochrome P450 (CYP)-mediated metabolism, there has been an increase in the frequency of involvement of non-CYP enzymes in the metabolism of investigational compounds. Although there have been numerous notable advancements in the characterization of non-CYP enzymes with respect to their localization, reaction mechanisms, species differences and identification of typical substrates, accurate prediction of non-CYP-mediated clearance, with a particular emphasis with the difficulties in accounting for any extrahepatic contributions, remains a challenge. The current manuscript comprehensively summarizes the recent advancements in the prediction of drug metabolism and the in vitro to in vitro extrapolation of clearance for substrates of non-CYP drug metabolizing enzymes.

Pig Liver Esterases Hydrolyze Endocannabinoids and Promote Inflammatory Response

Endocannabinoids are endogenous ligands of cannabinoid receptors and activation of these receptors has strong physiological and pathological significance. Structurally, endocannabinoids are esters (e.g., 2-arachidonoylglycerol, 2-AG) or amides (e.g., N-arachidonoylethanolamine, AEA). Hydrolysis of these compounds yields arachidonic acid (AA), a major precursor of proinflammatory mediators such as prostaglandin E₂. Carboxylesterases are known to hydrolyze esters and amides with high efficiency. CES1, a human carboxylesterase, has been shown to hydrolyze 2-AG, and shares a high sequence identity with pig carboxylesterases: PLE1 and PLE6 (pig liver esterase). The present study was designed to test the hypothesis that PLE1 and PLE6 hydrolyze endocannabinoids and promote inflammatory response. Consistent with the hypothesis, purified PLE1 and PLE6 efficaciously hydrolyzed 2-AG and AEA. PLE6 was 40-fold and 3-fold as active as PLE1 towards 2-AG and AEA, respectively. In addition, both PLE1 and PLE6 were highly sensitive to bis(4-nitrophenyl) phosphate (BNPP), an aryl phosphodiester known to predominately inhibit carboxylesterases. Based on the study with BNPP, PLEs contributed to the hydrolysis of 2-AG by 53.4 to 88.4% among various organs and cells. Critically, exogenous addition or transfection of PLE6 increased the expression and secretion of proinflammatory cytokines in response to the immunostimulant lipopolysaccharide (LPS). This increase was recapitulated in cocultured alveolar macrophages and PLE6 transfected cells in transwells. Finally, BNPP reduced inflammation trigged by LPS accompanied by reduced formation of AA and proinflammatory mediators. These findings define an innovative connection: PLE-endocannabinoid-inflammation. This mechanistic connection signifies critical roles of carboxylesterases in pathophysiological processes related to the metabolism of endocannabinoids.

Short-term standard alcohol consumption enhances platelet response to clopidogrel through inhibition of Nrf2/Ces1 pathway and induction of Cyp2c in mice

AIMS

Drinking alcohol is prevalent worldwide; however, it is unknown whether alcohol could affect the antiplatelet effects of clopidogrel in patients when taking both concomitantly. This study was designed to investigate the influence of short-term standard alcohol consumption on the metabolic activation of and platelet response to clopidogrel in mice as well as the mechanisms involved.

MAIN METHODS

Male C57BL/6J mice were administered with normal saline (vehicle control) or alcohol at 2 g/kg/day for 7 days, and then gavaged with vehicle control or a single dose of clopidogrel at 10 mg/kg. Inhibition of ADP-induced platelet aggregation and activation by clopidogrel, plasma concentrations of clopidogrel and its active metabolite H4, and changes in mRNA and protein expression of genes related to clopidogrel metabolism and its regulation were measured in mice pretreated with or without alcohol.

KEY FINDINGS

Compared with vehicle control, alcohol pretreatment significantly reduced hydrolysis of clopidogrel as a result of significant down-regulation of Nrf2-mediated Ces1 expression (responsible for the formation of clopidogrel carboxylate), increased metabolic activation of clopidogrel due to significant up-regulation of Cyp2c (for the formation of active thiol metabolite H4), and consequently enhanced inhibition of ADP-induced platelet aggregation and activation by clopidogrel.

SIGNIFICANCE

Short-term standard alcohol consumption would significantly enhance suppression of ADP-induced platelet aggregation and activation by clopidogrel through significant inhibition of Nrf2/Ces1 signaling pathway and induction of Cyp2c, suggesting that alcohol may interact with drugs that are predominantly metabolized by CES1 or CYP2C in patient care, including clopidogrel.

Analysis of Aspirin, Prasugrel and Clopidogrel in Counterfeit Pharmaceutical and Herbal Products: Plackett–Burman Screening and Box–Behnken Optimization

An isocratic reversed-phase high-performance liquid chromatographic method has been developed and validated for the simultaneous determination of aspirin, prasugrel HCl and clopidogrel bisulfate in the presence of clopidogrel-related compound (impurity-A) in focus on counterfeit. This method was used to determine counterfeited antiplatelet drugs in two substandard Indian pharmaceutical products sold on the market in Yemen and two traditional herbal medicines sold on the market in China. Thin layer chromatography and mass spectrometry of counterfeit herbal medicines have additionally been carried out to verify the identification of adulterants. Chromatographic separation was performed on Inertsil ® ODS-3 C18 (4.6 × 250 mm, 5 μm) with isocratic mobile phase elution containing a mixture of acetonitrile: (25 mM) potassium dihydrogen phosphate buffer, pH 2.7 adjusted with 0.1 M o-phosphoric acid (79: 21, v/v), at a flow rate of 1 mL/min and UV detection at 220 nm. Designs of experiment methodology, Plackett–Burman and Box–Behnken designs were used for the screening and optimization of the mobile phase composition. The method validation was also performed in accordance with the International Council on Harmonization (ICH) guidelines. The method developed for routine analysis was found to be sensitive, simple, accurate and highly robust. The results were statistically compared to reference methods using Student’s t-test and variance ratio F-test at P < 0.05.

Cyclic Peptides as Drugs for Intracellular Targets: The Next Frontier in Peptide Therapeutic Development

Developing macrocyclic peptides that can reach intracellular targets is a significant challenge. This review discusses the most recent strategies used to develop cell permeable cyclic peptides that maintain binding to their biological target inside the cell. Macrocyclic peptides are unique from small molecules because traditional calculated physical properties are unsuccessful for predicting cell membrane permeability. Peptide synthesis and experimental membrane permeability is the only strategy that effectively differentiates between cell permeable and cell impermeable molecules. Discussed are chemical strategies, including backbone N-methylation and stereochemical changes, which have produced molecular scaffolds with improved cell permeability. However, these improvements often come at the expense of biological activity as chemical modifications alter the peptide conformation, frequently impacting the compound's ability to bind to the target. Highlighted is the most promising approach, which involves side-chain alterations that improve cell permeability without impact binding events.

Rapalogues as hCES2A Inhibitors: In Vitro and In Silico Investigations

BACKGROUND AND OBJECTIVE

Rapamycin and its semi-synthetic analogues (rapalogues) are frequently used in combination with other prescribed medications in clinical settings. Although the inhibitory effects of rapalogues on cytochrome P450 enzymes (CYPs) have been well examined, the inhibition potentials of rapalogues on human esterases have not been investigated. Herein, the inhibition potentials and inhibitory mechanisms of six marketed rapalogues on human esterases are investigated.

METHODS

The inhibitory effects of six marketed rapalogues (rapamycin, zotarolimus, temsirolimus, everolimus, pimecrolimus and tacrolimus) on three major esterases, including human carboxylesterases 1 (hCES1A), human carboxylesterases 2 (hCES2A) and butyrylcholinesterase (BuChE), were assayed using isozyme-specific substrates. Inhibition kinetic analyses and docking simulations were performed to investigate the inhibitory mechanisms of the rapalogues with strong hCES2A inhibition potency.

RESULTS

Zotarolimus and pimecrolimus displayed strong inhibition of human hCES2A but these agents did not inhibit hCES1A or BuChE. Further investigation demonstrated that zotarolimus could strongly inhibit intracellular hCES2A in living HepG2 cells, with an estimated IC₅₀ value of 4.09 µM. Inhibition kinetic analyses revealed that zotarolimus inhibited hCES2A-catalyzed fluorescein diacetate hydrolysis in a mixed manner, with the K_i value of 1.61 µM. Docking simulations showed that zotarolimus could tightly bind on hCES2A at two district ligand-binding sites, consistent with its mixed inhibition mode.

CONCLUSION

Our findings demonstrate that several marketed rapalogues are potent and specific hCES2A inhibitors, and these agents can serve as leading compounds for the development of more efficacious hCES2A inhibitors to modulate the pharmacokinetic profiles and toxicity of hCES2A-substrate drugs (such as the anticancer agent irinotecan).

Per- and polyfluoroalkyl substances exert strong inhibition towards human carboxylesterases

PFASs are highly persistent in both natural and living environment, and pose a significant risk for wildlife and human beings. The present study was carried out to determine the inhibitory behaviours of fourteen PFASs on metabolic activity of two major isoforms of carboxylesterases (CES). The probe substrates 2-(2-benzoyl-3-methoxyphenyl) benzothiazole (BMBT) for CES1 and fluorescein diacetate (FD) for CES2 were utilized to determine the inhibitory potentials of PFASs on CES in vitro. The results demonstrated that perfluorododecanoic acid (PFDoA), perfluorotetradecanoic acid (PFTA) and perfluorooctadecanoic acid (PFOcDA) strongly inhibited CES1 and CES2. The half inhibition concentration (IC₅₀) value of PFDoA, PFTA and PFOcDA for CES1 inhibition was 10.6 μM, 13.4 μM and 12.6 μM, respectively. The IC₅₀ for the inhibition of PFDoA, PFTA and PFOcDA towards CES2 were calculated to be 9.56 μM, 17.2 μM and 8.73 μM, respectively. PFDoA, PFTA and PFOcDA exhibited noncompetitive inhibition towards both CES1 and CES2. The inhibition kinetics parameters (K_i) were 27.7 μM, 26.9 μM, 11.9 μM, 4.04 μM, 29.1 μM, 27.4 μM for PFDoA-CES1, PFTA-CES1, PFOcDA-CES1, PFDoA-CES2, PFTA-CES2, PFOcDA-CES2, respectively. In vitro-in vivo extrapolation (IVIVE) predicted that when the plasma concentrations of PFDoA, PFTA and PFOcDA were greater than 2.77 μM, 2.69 μM and 1.19 μM, respectively, it might interfere with the metabolic reaction catalyzed by CES1 in vivo; when the plasma concentrations of PFDoA, PFTA and PFOcDA were greater than 0.40 μM, 2.91 μM, 2.74 μM, it might interfere with the metabolic reaction catalyzed by CES2 in vivo. Molecular docking was used to explore the interactions between PFASs and CES. In conclusion, PFASs were found to cause inhibitory effects on CES in vitro, and this finding would provide an important experimental basis for further in vivo testing of PFASs focused on CES inhibition endpoints.

Type 2 diabetes mellitus decreases systemic exposure of clopidogrel active metabolite through upregulation of P-glycoprotein in rats

Patients with diabetic mellitus tend to have a poor response to clopidogrel (Clop) due to reduced generation of active metabolite (Clop-AM). However, the underlying mechanism is not elucidated. A type 2 diabetic mellitus (T2DM) rat model was established by combining high-fat diet feeding and low-dose streptozotocin (STZ) injection. The reduced Clop-AM exposure was observed in T2DM rats after oral administration of Clop. However, in vitro liver microsomes incubated with Clop exhibited increased Clop-AM levels in T2DM rats due to a significant decrease in carboxylesterase (CES)1 expression and activity and a significant increase in the expression or activity of CYP1A2 and CYP3A. Interestingly, different from oral administration, the significantly increased C_max of Clop-AM was observed in T2DM rats after intravenous injection, with no difference in AUC_0-t and t_1/2 values between the two strains. Meanwhile, in situ single -pass intestinal perfusion study showed lower absorption rate constant (Ka) and effective apparent permeability values (P_eff) of Clop in T2DM rats than in control rats. It is explained by the increased expression or function of P-glycoprotein (P-gp) and pregnane X receptor (PXR) in duodenum and jejunum of T2DM rats. Moreover, the decreased Clop-AM level in T2DM rats was eliminated by the pretreatment of cyclosporin A, a P-gp inhibitor. It suggests that intestinal absorption, not hepatic metabolism is responsible for the reduced Clop-AM exposure in T2DM rats. P-gp might be the key factor causing the reduction of Clop absorption, consequently making less Clop available for Clop-AM formation.

Dechlorination and demethylation of ochratoxin A enhance blocking activity of PXR activation, suppress PXR expression and reduce cytotoxicity

The pregnane X receptor (PXR) has been established to induce chemoresistance and metabolic diseases. Ochratoxin A (OTA), a mycotoxin, decreases the expression of PXR protein in human primary hepatocytes. OTA is chlorinated and has a methylated lactone ring. Both structures are associated with OTA toxicity. The study was to test the hypothesis that structural modifications differentially impact PXR blocking activity over cytotoxicity. To test this hypothesis, OTA-M and OTA-Cl/M were synthesized. OTA-M lacked the methyl group of the lactone-ring, whereas OTA-Cl/M had neither the methyl group nor the chlorine atom. The blocking activity of PXR activation was determined in a stable cell line, harboring both PXR (coding sequence) and its luciferase element reporter. OTA-Cl/M showed the highest blocking activity, followed by OTA-M and OTA. OTA-Cl/M was 60 times as potent as the common PXR blocker ketoconazole based on calculated IC₅₀ values. OTA-Cl/M decreased by 90 % the expression of PXR protein and was the least cytotoxic among the tested compounds. Molecular docking identified that OTA and its derivatives interacted with different sets of residues in PXR, providing a molecular basis for selectivity. Excessive activation of PXR has been implicated in chemoresistance and metabolic diseases. Downregulation of PXR protein expression likely delivers an effective mechanism against structurally diverse PXR agonists.

CYP2C19 and CYP3A4 activity and ADP-induced platelet reactivity in prasugrel- or ticagrelor-treated STEMI patients: monocentric study in PRAGUE-18 trial participants

We assessed the contribution of CYP2C19 and CYP3A4 metabolic activity to the ADP-induced platelet aggregation 1h and 24h after a loading dose of 60 mg prasugrel or 180 mg ticagrelor in patients with ST-elevation myocardial infarction (STEMI). Further, we assessed the contribution of CYP2C19 polymorphisms and medication to the CYP enzymatic activity.Patients with STEMI were randomly assigned to the treatment with prasugrel (n = 51) or ticagrelor (n = 46). Metabolic activity of CYP2C19 and CYP3A4 was assessed by the rate of 5-hydroxylation and sulfoxidation of lansoprazole. Further, patients were genotyped for CYP2C19 *2 and *17 alleles.In prasugrel-treated patients, high ADP-induced platelet reactivity 1h after the loading dose positively correlated with 5OH-lansoprazole/lansoprazole ratio (r = 0.44, p = 0.002), a marker of CYP2C19 metabolic activity, and negatively with lansoprazole-sulfone/lansoprazole ratio, which reflects CYP3A4 metabolic activity (r = -0.35, p = 0.018).CYP2C19 poor metabolizers had lower 5OH-lansoprazole/lansoprazole ratio and higher lansoprazole-sulfone/lansoprazole ratio, but without any effect on the ADP-induced platelet reactivity. The treatment with amiodarone, a CYP3A4 inhibitor, influenced neither the metabolic ratios nor the ADP-induced platelet reactivity.The CYP3A4 and CYP2C19 metabolic activity is associated with ADP-induced platelet reactivity in prasugrel-treated, but not ticagrelor-treated patients with STEMI.

Inhibition of human carboxylesterases by ginsenosides: structure-activity relationships and inhibitory mechanism

BACKGROUND

Human carboxylesterases (hCES) are key serine hydrolases responsible for the hydrolysis of a wide range of endogenous and xenobiotic esters. Although it has been reported that some ginsenosides can modulate the activities of various enzymes, the inhibitory effects of ginsenosides on hCES have not been well-investigated.

METHODS

In this study, more than 20 ginsenosides were collected and their inhibitory effects on hCES1A and hCES2A were assayed using the highly specific fluorescent probe substrates for each isoenzyme. Molecular docking simulations were also performed to investigate the interactions between ginsenosides and hCES.

RESULTS

Among all tested ginsenosides, Dammarenediol II (DM) and 20S-O-β-(d-glucosyl)-dammarenediol II (DMG) displayed potent inhibition against both hCES1A and hCES2A, while protopanaxadiol (PPD) and protopanaxatriol (PPT) exhibited strong inhibition on hCES2A and high selectivity over hCES1A. Introduction of O-glycosyl groups at the core skeleton decreased hCES inhibition activity, while the hydroxyl groups at different sites might also effect hCES inhibition. Inhibition kinetic analyses demonstrated that DM and DMG functioned as competitive inhibitors against hCES1A-mediated d-luciferin methyl ester (DME) hydrolysis. In contrast, DM, DMG, PPD and PPT inhibit hCES2A-mediated fluorescein diacetate (FD) hydrolysis via a mixed manner.

CONCLUSION

The structure-inhibition relationships of ginsenosides as hCES inhibitors was investigated for the first time. Our results revealed that DM and DMG were potent inhibitors against both hCES1A and hCES2A, while PPD and PPT were selective and strong inhibitors against hCES2A.

Pharmacometabolomics Informs About Pharmacokinetic Profile of Methylphenidate

Carboxylesterase 1 (CES1) metabolizes methylphenidate and other drugs. CES1 gene variation only partially explains pharmacokinetic (PK) variability. Biomarkers predicting the PKs of drugs metabolized by CES1 are needed. We identified lipids in plasma from 44 healthy subjects that correlated with CES1 activity as determined by PK parameters of methylphenidate including a ceramide (q value = 0.001) and a phosphatidylcholine (q value = 0.005). Carriers of the CES1 143E allele had decreased methylphenidate metabolism and altered concentration of this phosphatidylcholine (q value = 0.040) and several high polyunsaturated fatty acid lipids (PUFAs). The half‐maximal inhibitory concentration (IC₅₀) values of chenodeoxycholate and taurocholate were 13.55 and 19.51 μM, respectively, consistent with a physiological significance. In silico analysis suggested that bile acid inhibition of CES1 involved both binding to the active and superficial sites of the enzyme. We initiated identification of metabolites predicting PKs of drugs metabolized by CES1 and suggest lipids to regulate or be regulated by this enzyme.

Identification of novel agonists by high-throughput screening and molecular modelling of human constitutive androstane receptor isoform 3

Prediction of drug interactions, based on the induction of drug disposition, calls for the identification of chemicals, which activate xenosensing nuclear receptors. Constitutive androstane receptor (CAR) is one of the major human xenosensors; however, the constitutive activity of its reference variant CAR1 in immortalized cell lines complicates the identification of agonists. The exclusively ligand-dependent isoform CAR3 represents an obvious alternative for screening of CAR agonists. As CAR3 is even more abundant in human liver than CAR1, identification of its agonists is also of pharmacological value in its own right. We here established a cellular high-throughput screening assay for CAR3 to identify ligands of this isoform and to analyse its suitability for identifying CAR ligands in general. Proof-of-concept screening of 2054 drug-like compounds at 10 µM resulted in the identification of novel CAR3 agonists. The CAR3 assay proved to detect the previously described CAR1 ligands in the screened libraries. However, we failed to detect CAR3-selective compounds, as the four novel agonists, which were selected for further investigations, all proved to activate CAR1 in different cellular and in vitro assays. In primary human hepatocytes, the compounds preferentially induced the expression of the prototypical CAR target gene CYP2B6. Failure to identify CAR3-selective compounds was investigated by molecular modelling, which showed that the isoform-specific insertion of five amino acids did not impact on the ligand binding pocket but only on heterodimerization with retinoid X receptor. In conclusion, we demonstrate here the usability of CAR3 for screening compound libraries for the presence of CAR agonists.

The impact of CYP2C19 and CYP4F2 variants and clinical factors on treatment outcomes during antiplatelet therapy

Aim: The aim of this study was to determine the impact of genetic and nongenetic factors on treatment outcomes in patients receiving dual antiplatelet therapy after percutaneous coronary intervention and stent implantation. Materials & methods: Patients (n = 628) used clopidogrel or ticagrelor for at least 1 week before platelet aggregation test. Results: Multivariate binary regression analysis demonstrated that aspirin use and CYP4F2 T allele significantly increased odds for bleeding in clopidogrel users (OR: 2.488, 95% CI: 1.452-4.265; p = 0.001 and OR: 1.573, 95% CI: 1.066-2.320; respectively; p = 0.022). CYP4F2 T allele significantly increased odds for bleeding in ticagrelor users (OR: 8.270, 95% CI: 3.917-17.462; p < 0.001). Conclusion: Aspirin use and CYP4F2 T allele were significantly associated with bleeding during dual antiplatelet therapy.

Impact of the Chinese herbal medicines on dual antiplatelet therapy with clopidogrel and aspirin: Pharmacokinetics and pharmacodynamics outcomes and related mechanisms in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Dual antiplatelet therapy (DAPT) with aspirin (ASA) and clopidogrel (CLP) has been consistently shown clinical effectiveness in patients with coronary artery disease. According to the literature, four traditional Chinese medicine (TCM) herbs effective for prevention cardiovascular diseases, namely Radix Salvia Miltiorrhiza (Red sage root, Danshen), Radix Pueraria Lobata (Kudzu root, Gegen), Radix Angelica Sinensis (Angelica root, Danggui), and Rhizoma Ligusticum chuanxiong (Szehuan lovage rhizome, Chuanxiong), are of high potential to be co-administered during DAPT. Since all these herbs are blood vitalizing medicines and can promote blood circulation and eliminate blood stasis, it was hypothesized that they may potentially alter the clinical outcomes of DAPT with clopidogrel and aspirin.

AIM OF STUDY

The current study is proposed aiming to preliminarily evaluate the impact of these four commonly used Chinese medicinal herbs on the pharmacokinetics and pharmacodynamics of the combination therapy with clopidogrel and aspirin and its relevant outcomes and mechanisms.

MATERIALS AND METHODS

In order to mimic the standard dosing regimen for DAPT in human, various Sprague-Dawley rats treatment groups were received a bolus oral dose of DAPT on day 1 followed by DAPT for consecutive 13 days in absence and presence of orally co-administered four TCM herbs (Danshen, Gegen, Danggui and Chuanxiong) at their low and high doses. On day 14, serial blood samples were collected after dosing to obtain the plasma concentrations of ASA, CLP and their corresponding metabolites by LC/MS/MS. At the end of last blood sampling point of each rat, about 4.5 ml of whole blood were collected to estimate the prothrombin time from each treatment groups. After all the blood sampling, the rats were sacrificed followed by collecting their livers for evaluations of enzyme activities and expressions in the related liver microsome preparations and stomach tissues for evaluations of their potential ulcer index. In addition, gene expression and protein levels of related biomarkers (COX-1, COX-2, P2Y12) in rat livers were measured by RT-PCR and Western blot, respectively, and compared among different treatment groups.

RESULTS

Co-administration of Gegen and Danggui significantly altered the pharmacokinetics of ASA and CLP in DAPT with increased systemic exposure of ASA and CLP respectively. Although minimal impact on aspirin esterase activity for all co-administered herbs, significant inhibition on rCyp2c11 and carboxylesterase activities were observed for DAPT with Danshen, Gegen and Danggui co-treatment. In addition, significantly longer PT were found in all DAPT treatment groups. However, a trend of decrease in PT of DAPT in presence of Gegen, Danggui and Chuanxiong was noticed. Nevertheless, all the treatments did not cause detectable changes in COX and P2Y12 mRNA and protein expressions.

CONCLUSION

Among the four studied TCMs, it was demonstrated that co-administration of Gegen and Danggui could lead to altered pharmacokinetics of DAPT with significant inhibition on rCyp2c11 and carboxylesterase activities. Although Gegen, Danggui and Chuanxiong might potentially offset the anticoagulant activity of DAPT, the overall pharmacodynamics outcome was not considered to be harmful due to lack of risk in bleeding, which warrant further verification for its clinical impact.

Delivering bioactive cyclic peptides that target Hsp90 as prodrugs

The most challenging issue facing peptide drug development is producing a molecule with optimal physical properties while maintaining target binding affinity. Masking peptides with protecting groups that can be removed inside the cell, produces a cell-permeable peptide, which theoretically can maintain its biological activity. Described are series of prodrugs masked using: (a) O-alkyl, (b) N-alkyl, and (c) acetyl groups, and their binding affinity for Hsp90. Alkyl moieties increased compound permeability, P_app, from 3.3 to 5.6, however alkyls could not be removed by liver microsomes or in-vivo and their presence decreased target binding affinity (IC₅₀ of ≥10 µM). Thus, unlike small molecules, peptide masking groups cannot be predictably removed; their removal is related to the 3-D conformation. O-acetyl groups were cleaved but are labile, increasing challenges during synthesis. Utilising acetyl groups coupled with mono-methylated amines may decrease the polarity of a peptide, while maintaining binding affinity.