The metabolic activation of and platelet response to vicagrel vary with P-glycoprotein deficiency, rather than P-glycoprotein inhibition, in mice.

This study aimed to determine changes in the hydrolysis of vicagrel, a substrate drug of arylacetamide deacetylase (Aadac) and carboxylesterase 2 (Ces2), in P-glycoprotein (P-gp)-deficient or P-gp-inhibited mice and to elucidate the mechanisms involved.Male wild-type (WT) and P-gp knock-out (KO) mice were used to investigate the systemic exposure of vicagrel thiol active metabolite H4 and platelet response to vicagrel, and the mRNA and protein expression levels of intestinal Aadac and Ces2. Moreover, WT mice were administered vicagrel alone or in combination with elacridar (a potent P-gp inhibitor) to determine drug-drug interactions.Compared with WT mice, P-gp KO mice exhibited significant increases in the systemic exposure of H4, the protein expression levels of intestinal Aadac and Ces2, and inhibition of ADP-induced platelet aggregation by vicagrel. Further, the H4 exposure was positively correlated with intestinal Aadac protein expression levels but did not vary with short-term inhibition of P-gp efflux activity by elacridar.P-gp-deficient mice, rather than elacridar-treated mice, exhibited significant upregulation of intestinal Aadac and Ces2 and thus, enhanced metabolic activation of and platelet response to vicagrel, suggesting that the metabolic activation of vicagrel may vary with P-gp deficiency, not P-gp inhibition, in mice.

Vicagrel is hydrolyzed by Raf kinase inhibitor protein in human intestine.

As an analog of clopidogrel and prasugrel, vicagrel is completely hydrolyzed to intermediate thiolactone metabolite 2-oxo-clopidogrel (also the precursor of active thiol metabolite H4) in human intestine, predominantly by AADAC and CES2; however, other unknown vicagrel hydrolases remain to be identified. In this study, recombinant human Raf kinase inhibitor protein (rhRKIP) and pooled human intestinal S9 (HIS9) fractions and microsome (HIM) preparations were used as the different enzyme sources; prasugrel as a probe drug for RKIP (a positive control), vicagrel as a substrate drug of interest, and the rate of the formation of thiolactone metabolites 2-oxo-clopidogrel and R95913 as metrics of hydrolase activity examined, respectively. In addition, an IC50 value of inhibition of rhRKIP-catalyzed vicagrel hydrolysis by locostatin was measured, and five classical esterase inhibitors with distinct esterase selectivity were used to dissect the involvement of multiple hydrolases in vicagrel hydrolysis. The results showed that rhRKIP hydrolyzed vicagrel in vitro, with the values of Km , Vmax , and CLint measured as 20.04 ± 1.99 µM, 434.60 ± 12.46 nM/min/mg protein, and 21.69 ± 0.28 ml/min/mg protein, respectively, and that an IC50 value of locostatin was estimated as 1.24 ± 0.04 mM for rhRKIP. In addition to locostatin, eserine and vinblastine strongly suppressed vicagrel hydrolysis in HIM. It is concluded that RKIP can catalyze the hydrolysis of vicagrel in the human intestine, and that vicagrel can be hydrolyzed by multiple hydrolases, such as RKIP, AADAC, and CES2, concomitantly.

Antiplatelet effect, safety, and pharmacokinetics of vicagrel in patients with coronary artery disease undergoing percutaneous coronary intervention.

AIMS: Vicagrel, a novel antiplatelet prodrug to overcome the residual high platelet reactivity of clopidogrel induced by inactive metabolism and cytochrome P450 (CYP) 2C19 polymorphisms, provides favourable antiplatelet inhibition in healthy volunteers. However, its antiplatelet effect and safety in patients with coronary artery disease (CAD) are unclear. METHODS AND RESULTS: This was a multicentre, randomized, double-blind, triple-dummy, dose-exploring phase II trial comparing the antiplatelet activity and safety of vicagrel at different doses vs. those of clopidogrel in patients with CAD undergoing percutaneous coronary intervention (PCI). The primary endpoint was inhibition of adenosine diphosphate (ADP)-induced platelet aggregation (%IPA) after loading and maintenance doses (LD/MD) at 28 days. Safety endpoints included adverse events (AEs) and Bleeding Academic Research Consortium-defined any bleeding. Pharmacokinetic (PK) profiles and the influence of CYP2C19 polymorphisms were explored in subgroup analysis. Two hundred and seventy-nine patients diagnosed with stable CAD (51.97%), unstable angina (40.86%), and myocardial infarction (7.17%) were randomized to receive vicagrel 20/5 mg (LD/MD), 24/6 mg, or 30/7.5 mg or clopidogrel 300/75 mg in combination with aspirin. %IPAs on Day 28 were 30.19%, 35.02%, 45.61%, and 32.55% for vicagrel 20/5, 24/6, and 30/7.5 mg and clopidogrel, respectively, and were comparable across all groups (P = 0.0694). The plasma concentration of the vicagrel active metabolite M15-2 had a similar area under curve and Tmax to those of clopidogrel. There were no significant differences in AEs (4.35%, 0%, 1.45%, and 5.56% for vicagrel 20/5, 24/6, and 30/7.5 mg and clopidogrel, P = 0.6667) or any bleeding (13.04%, 14.06%, 11.59%, and 11.11% for vicagrel 20/5, 24/6, and 30/7.5 mg and clopidogrel, respectively, P = 0.95) across four groups. %IPAs and PK profiles of vicagrel did not vary significantly among different CYP2C19 metabolizers. CONCLUSION: Vicagrel had comparable antiplatelet effect and safety to clopidogrel in patients with CAD undergoing PCI.

Inhibition of cytochrome P450 enzymes and uridine 5'-diphospho-glucuronosyltransferases by vicagrel in human liver microsomes: A prediction of potential drug-drug interactions.

Vicagrel, an antiplatelet drug candidate targeting platelet P2Y12 receptor and has finished its phase II clinical trial. The inhibition of six major cytochrome P450 enzymes (P450) (CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, and CYP3A4) and six UDP-glucuronosyltransferases (UGT) (UGT1A1, UGT1A3, UGT1A4, UGT1A6, UGT1A9, and UGT2B7) by vicagrel was evaluated using pooled human liver microsomes and specific probe substrates. Physiology-based pharmacokinetic (PBPK) simulation was further applied to predict the in vivo drug-drug interaction (DDI) potential between vicagrel and bupropion as well as S-mephenytoin. The results suggested that vicagrel inhibited CYP2B6 and CYP2C19 potently with apparent IC50 values of 1.6 and 2.0 µM, respectively. In terms of mode of reversible inhibition, vicagrel exhibited mixed-type inhibition of CYP2B6-catalyzed bupropion hydroxylation and noncompetitive inhibition of CYP2C19-mediated S-mephenytoin 4'-hydroxylation with Ki values of 0.19 µM and 1.2 µM, respectively. Vicagrel displayed profound time-dependent inhibition towards CYP2B6 with maximal rate constant of inactivation (kinact) and half-maximal inactivator concentration (KI) values of 0.062 min-1 and 1.52 µM, respectively. No time-dependent inhibition by vicagrel was noted for CYP2C19. For UGT, negligible to moderate inhibition by vicagrel was observed with IC50 values of >50.0, >50.0, 28.2, 8.7, >50.0 and 28.2 µM for UGT1A1, UGT1A3, UGT1A4, UGT1A6, UGT1A9 and UGT2B7, respectively. In terms of mode of reversible inhibition, vicagrel exhibited mixed-type inhibition of UGT1A6-catalyzed N-Acetylserotonin ß-D-glucuronidation with a Ki value of 5.6 µM. No time-dependent inhibition by vicagrel was noted for UGT1A6. PBPK simulation indicated that neither altered AUC nor Cmax of bupropion and S-mephenytoin was observed in the presence of vicagrel. Our study provides inhibitory constants for future DDI prediction between vicagrel and drug substrates of CYP2B6, CYP2C19 and UGT1A6. In addition, our simulation suggests the lack of clinically important DDI between vicagrel and bupropion or S-mephenytoin.

Corrigendum: Predicting the Effects of CYP2C19 and Carboxylesterases on Vicagrel, a Novel P2Y12 Antagonist, by Physiologically Based Pharmacokinetic/Pharmacodynamic Modeling Approach.

[This corrects the article DOI: 10.3389/fphar.2020.591854.].

Pharmacokinetics, mass balance, and metabolism of [14C]vicagrel, a novel irreversible P2Y12 inhibitor in humans.

Vicagrel, a novel irreversible P2Y12 receptor inhibitor, is undergoing phase III trials for the treatment of acute coronary syndromes in China. In this study, we evaluated the pharmacokinetics, mass balance, and metabolism of vicagrel in six healthy male Chinese subjects after a single oral dose of 20 mg [14C]vicagrel (120 µCi). Vicagrel absorption was fast (Tmax = 0.625 h), and the mean t1/2 of vicagrel-related components was ~38.0 h in both plasma and blood. The blood-to-plasma radioactivity AUCinf ratio was 0.55, suggesting preferential distribution of drug-related material in plasma. At 168 h after oral administration, the mean cumulative excreted radioactivity was 96.71% of the dose, including 68.03% in urine and 28.67% in feces. A total of 22 metabolites were identified, and the parent vicagrel was not detected in plasma, urine, or feces. The most important metabolic spot of vicagrel was on the thiophene ring. In plasma pretreated with the derivatization reagent, M9-2, which is a methylated metabolite after thiophene ring opening, was the predominant drug-related component, accounting for 39.43% of the radioactivity in pooled AUC0-8 h plasma. M4, a mono-oxidation metabolite upon ring-opening, was the most abundant metabolite in urine, accounting for 16.25% of the dose, followed by M3-1, accounting for 12.59% of the dose. By comparison, M21 was the major metabolite in feces, accounting for 6.81% of the dose. Overall, renal elimination plays a crucial role in vicagrel disposition, and the thiophene ring is the predominant metabolic site.

Impacts of CYP2C19 genetic polymorphisms on bioavailability and effect on platelet adhesion of vicagrel, a novel thienopyridine P2Y12 inhibitor.

AIMS: We investigated the impacts of CYP2C19 polymorphisms on pharmacokinetics and pharmacodynamics of vicagrel in healthy Chinese subjects. METHODS: CYP2C19 extensive metabolizers (EMs), intermediate metabolizers (IMs) and poor metabolizers (PMs; 16 subjects/group) participated in a randomized, open-label, 2-period cross-over study. Each study period lasted 7 days, with a loading dose of 24 mg of vicagrel or 300 mg of clopidogrel on day 1, and maintenance doses of 6 mg of vicagrel or 75 mg of clopidogrel daily from day 2 to day 7. The pharmacokinetics and pharmacodynamics were assessed on day 1 and day 7. RESULTS: After a loading dose, the AUC0-t of the active metabolite H4 by vicagrel was slightly lower in IMs and PMs (decreased by 21 and 27%, respectively) compared to EMs. Similar results were found after maintenance doses. In EMs, the AUC0-t of H4 by vicagrel was somewhat higher than clopidogrel after the loading dose, and comparable with clopidogrel (90% confidence interval 0.94, 1.21) after the maintenance doses. However, it was much higher than clopidogrel in PMs, with a 1.28-fold (loading dose) and a 73% (maintenance doses) increases compared to clopidogrel (P < 0.001). Consequently, the inhibition of platelet aggregation by vicagrel was greater than clopidogrel after both loading dose (28.2 vs 12.4% at 4 hours, P < 0.01) and maintenance doses (42.8 vs 24.6% at 4 hours, P < 0.001) in PMs. CONCLUSIONS: CYP2C19 polymorphisms have less impact on vicagrel as compared to clopidogrel. Drug exposure and response to vicagrel in PMs were even higher than to clopidogrel in IMs.

Development and validation of a UPLC-MS/MS method for simultaneous determination of vicagrel and its major metabolites in rat or human plasma: An optimized novel strategy for the stabilization of vicagrel.

Vicagrel is a promising novel antiplatelet drug. However, the quantification of vicagrel in plasma is currently unavailable since it is liable to be hydrolyzed in plasma by esterases. In this study, an optimized strategy was developed and validated to stabilize vicagrel, 2-oxo-clopidogrel (thiolactone metabolite), and H4 (active thiol metabolite) before quantification of the analytes, such as addition of citric acid (for plasma acidification) and NaF (a non-specific esterase inhibitor) to inhibit esterase activity, immediate addition of a thiol-alkylating reagent MPB into blood samples to derivatize H4 for the formation of stable H4 derivative (i.e., MP-H4), use of the anticoagulant K2EDTA to minimize the conversion of 2-oxo-clopidogrel to H-endo, and keeping the analytes at 4 °C or on wet ice to minimize degradation of the analytes when processed and analyzed. The stability was measured as percent of each analyte remained in plasma samples after their storage for 4 h at 4 °C or in blood samples after 1 h at 4 °C. The results indicated that stability of vicagrel was increased significantly in stabilized plasma or blood samples compared with non-stabilized controls for rats and humans, respectively, and that the stability of 2-oxo-clopidogrel was increased to a certain extent. In contrast, MP-H4 formed was stable in plasma immediately after thorough mixture of MPB with blood. We conclude that the above strategy is useful for improving the stability of vicagrel, 2-oxo-clopidogrel, and H4 in rat or human plasma, and that vicagrel and its two major metabolites can be quantified accurately and simultaneously.

Predicting the Effects of CYP2C19 and Carboxylesterases on Vicagrel, a Novel P2Y12 Antagonist, by Physiologically Based Pharmacokinetic/Pharmacodynamic Modeling Approach.

Vicagrel, a novel acetate derivative of clopidogrel, exhibits a favorable safety profile and excellent antiplatelet activity. Studies aim at identifying genetic and non-genetic factors affecting vicagrel metabolic enzymes Cytochrome P450 2C19 (CYP2C19), Carboxylesterase (CES) 1 and 2 (CES1 and CES2), which may potentially lead to altered pharmacokinetics and pharmacodynamics, are warranted. A physiologically based pharmacokinetic/pharmacodynamic (PBPK/PD) model incorporating vicagrel and its metabolites was constructed, verified and validated in our study, which could simultaneously characterize its sequential two step metabolism and clinical response. Simulations were then performed to evaluate the effects of CYP2C19, CES1 and CES2 genetic polymorphisms as well as inhibitors of these enzymes on vicagrel pharmacokinetics and antiplatelet effects. Results suggested vicagrel was less influenced by CYP2C19 metabolic phenotypes and CES1 428 G > A variation, in comparison to clopidogrel. No pharmacokinetic difference in the active metabolite was also noted for volunteers carrying different CES2 genotypes. Omeprazole, a CYP2C19 inhibitor, and simvastatin, a CES1 and CES2 inhibitor, showed weak impact on the pharmacokinetics and pharmacodynamics of vicagrel. This is the first study proposing a dynamic PBPK/PD model of vicagrel able to capture its pharmacokinetic and pharmacodynamic profiles simultaneously. Simulations indicated that genetic polymorphisms and drug-drug interactions showed no clinical relevance for vicagrel, suggesting its potential advantages over clopidogrel for treatment of cardiovascular diseases. Our model can be utilized to support further clinical trial design aiming at exploring the effects of genetic polymorphisms and drug-drug interactions on PK and PD of this novel antiplatelet agent.

Vicagrel enhances aspirin-induced inhibition of both platelet aggregation and thrombus formation in rodents due to its decreased metabolic inactivation.

Both aspirin and vicagrel are effective antiplatelet drugs, with the potential for concomitant use as another dual-antiplatelet therapy for the prevention of recurrent thrombotic or ischemic events. Because they both are the substrates of carboxylesterase 2 (CES2), aspirin attenuated the metabolic activation of and platelet response to vicagrel in mice treated with the two drugs concomitantly. In this study, we sought to clarify whether vicagrel could affect platelet responses to aspirin and their underlying mechanisms. Plasma levels of aspirin and salicylic acid were determined by liquid chromatography-tandem mass spectrometry, inhibition of arachidonic acid (AA)-induced whole-blood platelet aggregation by aspirin was assessed with an aggregometer, and their antithrombotic effects were evaluated by arteriovenous shunt thrombosis model. The results showed that concomitant use of vicagrel (5, 10, or 20 mg/kg) led to an average of 55% and 77% increases in systemic exposure of aspirin (Cmax and AUC0-t) and 2.8-fold increase in suppression of AA-induced platelet aggregation in mice when compared with use of aspirin alone. In the rat thrombus formation model, vicagrel (1 mg/kg) enhanced inhibition of thrombosis formation by aspirin (5 mg/kg), but not vice versa. We conclude that vicagrel increases platelet responses to aspirin and also enhances inhibition of thrombus formation of aspirin due to decreased CES2-catalyzed aspirin inactivation in rodents, and that an integrated net effect on thrombus formation in vivo is superior to inhibition of AA- or ADP-induced platelet aggregation ex vivo by either of the two drugs if taken concomitantly.

Pharmacokinetics and pharmacokinetic/pharmacodynamic relationship of vicagrel, a novel thienopyridine P2Y12 inhibitor, compared with clopidogrel in healthy Chinese subjects following single oral dosing.

BACKGROUND AND OBJECTIVES: Vicagrel, a novel thienopyridine antiplatelet agent, is an analogue of clopidogrel in development for the treatment of acute coronary syndromes. This study investigated the pharmacokinetic properties of vicagrel after single oral dosing with a direct comparison with clopidogrel in healthy Chinese subjects in the first two phase I clinical studies. The relationship between the exposure to the active metabolite and the platelet reactivity was also assessed for vicagrel. METHODS: Study A was a single-ascending-dose study of vicagrel (5-75 mg) compared with clopidogrel (75 mg) in 67 healthy volunteers. Study B was a randomized, two-period, crossover, loading-dose study of vicagrel 20 mg compared with clopidogrel 300 mg in 12 healthy subjects. Plasma concentrations of three common metabolites of vicagrel and clopidogrel, the active thiol metabolite H4, the inactive thiol metabolite H3, and the S-methylated form of H3 (SM3, the major metabolite of vicagrel), were determined using a validated UHPLC-MS/MS method. The relationship between the AUC0-t of active H4 and the P2Y12 reaction units at 4 h after administration of vicagrel was investigated. Blood concentrations of vicagrel were determined after a single oral administration of vicagrel 25 mg to two healthy Chinese subjects. RESULTS: In the single-ascending-dose study, vicagrel was metabolized rapidly with the median tmax for the three metabolites, namely, H4, H3, and SM3, ranging from 0.25-1.75 h. The pharmacokinetics of the three metabolites for vicagrel were linear across the dose range of 5-75 mg, with the mean Cmax and AUCs for H4 and H3 increasing in an approximately 1:1 dose-proportional manner and for SM3 increasing in a <1:1 dose-proportional manner. The median tmax for active H4 in the vicagrel 5 mg group was slightly shorter than that in the clopidogrel 75 mg group (0.50 versus 0.75 h). The mean AUC0-t for H4 in the vicagrel 5 mg group was similar to that in the clopidogrel 75 mg group (11.7 versus 11.8 ng∙h/mL). The AUC0-t of active H4 was apparently associated with the P2Y12 reaction units at 4 h for vicagrel. In the loading-dose study, for active H4, the median tmax was slightly shorter (0.50 versus 0.75 h) and the mean AUC0-t was 29% higher in the vicagrel 20 mg group than those in the clopidogrel 300 mg group. After a single oral administration of vicagrel 25 mg to 2 subjects, vicagrel was detected in blood but in very low concentrations. CONCLUSIONS: Vicagrel was rapidly and extensively metabolized, and the levels of the parent drug in circulation were very low. The pharmacokinetics of the three metabolites of vicagrel were linear and predictable across the dose range of 5-75 mg. The AUC of active H4 was apparently associated with the P2Y12 reaction units for vicagrel. For active H4, vicagrel 5 mg produced similar exposure (AUC) with more rapid appearance compared with clopidogrel 75 mg, and vicagrel 20 mg produced even slightly higher exposure (AUC) with more rapid appearance compared with clopidogrel 300 mg in humans. TRIAL REGISTRATION: CTR20150346, CTR20160379.

Evaluation of Tolerability, Pharmacokinetics and Pharmacodynamics of Vicagrel, a Novel P2Y12 Antagonist, in Healthy Chinese Volunteers.

Background: Vicagrel is a novel anti-platelet drug and hydrolyzed to the same intermediate as clopidogrel via esterase, instead of CYP2C19. Here we report the first clinical trial on the tolerability, pharmacokinetics and pharmacodynamics of different doses of vicagrel, and comparison with clopidogrel in healthy Chinese volunteers. Methods: This study was conducted in two parts. Study I was a dose-escalating (5-15 mg) study. For each dose, 15 participants were randomized into three groups (total n = 45); nine participants were given vicagrel, three were given clopidogrel, and three were given a placebo. Study II was conducted to assess interactions between vicagrel and aspirin in 15 healthy participants. The plasma concentrations of the metabolites of vicagrel and clopidogrel were determined using a LC-MS/MS method. Platelet aggregation was assessed using the VerifyNow-P2Y12 assay. Results: Vicagrel (5-15 mg per day) dosing for 10 days or addition of aspirin was well tolerated in healthy volunteers. The exposure of the active metabolite increased proportionally across the dose range and was higher (~10-fold) than clopidogrel. The levels of IPA dosing 75 mg clopidogrel were between the responses of 5 mg and 10 mg vicagrel. After a single loading dose of vicagrel (30 mg) and a once-daily maintenance dose (7.5 mg) for 8 days, the maximum inhibition of platelet aggregation was similar to that seen with the combined use of vicagrel and aspirin (100 mg/day). Conclusion: Oral vicagrel demonstrated a favorable safety profile and excellent anti-platelet activity, which could be a promising P2Y12 antagonist as anti-platelet drug and can be further developed in phase II/III studies, and marketing for the unmet medical needs of cardiovascular diseases. The study was registered at http://www.chictr.org.cn (ChiCTR-IIR-16009260).

Development and validation of a sensitive and rapid UHPLC-MS/MS method for the simultaneous quantification of the common active and inactive metabolites of vicagrel and clopidogrel in human plasma.

Vicagrel, an analog of clopidogrel, is a novel thienopyridine P2Y12 antagonist in clinical development in China for the treatment of acute coronary syndromes. Vicagrel and clopidogrel are prodrugs requiring metabolic activation to produce a pharmacologically active thiol metabolite (H4) in vivo. The formation of H4 from vicagrel in humans is promising more efficient and consistent than that from clopidogrel. After oral dosing of vicagrel or clopidogrel to humans, the active thiol metabolite H4 and two inactive metabolites closely related to H4 formation (the thiol metabolite H3 and the S-methylated metabolite SM3) were observed in plasma; SM3 was the most abundant drug-related component of vicagrel in circulation. In this study, a sensitive, rapid, and reliable UHPLC-MS/MS method was developed for the simultaneous determination of derivatized H3 (MP-H3), derivatized H4 (MP-H4), and SM3 in human plasma to investigate the pharmacokinetics of vicagrel in healthy subjects compared with clopidogrel. After extracted from 50µL of plasma by simple protein precipitation, the analytes and stable isotope-labeled internal standards were separated on an Acquity UPLC BEH C18 column (100mm×2.1mm, 1.7µm). The mobile phase was acetonitrile-water-formic acid (45:55:0.0275, v/v/v) delivered at a flow rate of 0.45mL/min under isocratic elution. The total chromatographic run time was 6min. MP-H3, MP-H4, and SM3 were separated from their corresponding isomers under the chromatographic conditions. Mass spectrometric detection was conducted in multiple reaction monitoring mode on an AB Sciex Qtrap 5500 System using a positive electrospray ionization interface. The calibration curves were linear in the following ranges: 0.100-200ng/mL for MP-H3 and MP-H4 and 1.00-1000ng/mL for SM3. The intra- and inter-day accuracy and precision for each analyte at all concentrations were within acceptable limits (±15%). The validated method was successfully applied to compare the pharmacokinetics of vicagrel and clopidogrel after a single oral administration to healthy subjects in the first-in-human study of vicagrel.

Arylacetamide Deacetylase Is Involved in Vicagrel Bioactivation in Humans.

Vicagrel, a structural analog of clopidogrel, is now being developed as a thienopyridine antiplatelet agent in a phase II clinical trial in China. Some studies have shown that vicagrel undergoes complete first-pass metabolism in human intestine, generating the hydrolytic metabolite 2-oxo-clopidogrel via carboxylesterase-2 (CES2) and subsequently the active metabolite H4 via CYP450s. This study aimed to identify hydrolases other than CES2 that are involved in the bioactivation of vicagrel in human intestine. This study is the first to determine that human arylacetamide deacetylase (AADAC) is involved in 2-oxo-clopidogrel production from vicagrel in human intestine. In vitro hydrolytic kinetics were determined in human intestine microsomes and recombinant human CES and AADAC. The calculated contribution of CES2 and AADAC to vicagrel hydrolysis was 44.2 and 53.1% in human intestine, respectively. The AADAC-selective inhibitors vinblastine and eserine effectively inhibited vicagrel hydrolysis in vitro. In addition to CES2, human intestine AADAC was involved in vicagrel hydrolytic activation before it entered systemic circulation. In addition, simvastatin efficiently inhibited the production of both 2-oxo-clopidogrel and active H4; further clinical trials are needed to determine whether the hydrolytic activation of vicagrel is influenced by coadministration with simvastatin. This study deepens the understanding of the bioactivation and metabolism properties of vicagrel in humans, which can help further understand the bioactivation mechanism of vicagrel and the variations in the treatment responses to vicagrel and clopidogrel.

Species Comparison of Pre-systemic Bioactivation of Vicagrel, a New Acetate Derivative of Clopidogrel.

Previously we have found vicagrel, a new acetate derivative of clopidogrel, underwent hydrolysis to 2-oxo-clopidogrel and subsequent conversions to its pharmacological active metabolite (AM) and inactive carboxylic acid metabolite (CAM). This study demonstrated the interspecies differences of the vicagrel bioactivation by comparing the critical vicagrel metabolites formation in rats, dogs and human. The pharmacokinetic studies with rats and dogs were conducted after intragastric administration of vicagrel, followed by in vitro metabolism investigation in venous system, intestinal/hepatic microsomes from rats, dogs and human. An obvious disparity was observed in system exposure to AM (99.0 vs. 635.1 µg⋅h/L, p < 0.05) and CAM (10119 vs. 2634 µg⋅h/L, p < 0.05) in rats and dogs. It was shown that the cleavage of vicagrel was almost completed in intestine with great different clearance (53.28 vs. 3.643 L⋅h-1⋅kg-1, p < 0.05) in rats and dogs. With no further hydrolysis to CAM, the greatest clearance of AM (3.26 mL⋅h-1⋅kg-1) was found in dog intestine. In rat plasma, 2-oxo-clopidogrel was much more extensively hydrolyzed to CAM than in dog and human. Albeit similar hydrolysis clearance and AM production was observed among hepatic microsomes of the three species, the production velocity of CAM ranked highest in dogs (7.55 pmol/min/mg protein). Therefore, the unconformity of AM and CAM exposure cross species mainly came from the metabolism of 2-oxo-clopidogrel associated largely with tissue specificity and interspecies differences of esterases. In human, the pharmacokinetics of vicagrel might be more optimistic due to less inactivation hydrolysis before reaching liver.

Significant Improvement of Metabolic Characteristics and Bioactivities of Clopidogrel and Analogs by Selective Deuteration.

In the search for prodrug analogs of clopidogrel with improved metabolic characteristics and antiplatelet bioactivity, a group of clopidogrel and vicagrel analogs selectively deuterated at the benzylic methyl ester group were synthesized, characterized, and evaluated. The compounds included clopidogrel-d3 (8), 2-oxoclopidogrel-d3 (9), vicagrel-d3 (10a), and 12 vicagrel-d3 analogs (10b-10m) with different alkyl groups in the thiophene ester moiety. The D3C-O bond length in 10a was shown by X-ray single crystal diffraction to be shorter than the H3C-O bond length in clopidogrel, consistent with the slower rate of hydrolysis of 8 than of clopidogrel in rat whole blood in vitro. A study of the ability of the compounds to inhibit ADP-induced platelet aggregation in fresh rat whole blood collected 2 h after oral dosing of rats with the compounds (7.8 µmol/kg) showed that deuteration increased the activity of clopidogrel and that increasing the size of the alkyl group in the thiophene ester moiety reduced activity. A preliminary pharmacokinetic study comparing 10a with vicagrel administered simultaneously as single oral doses (72 µmol/kg of each drug) to male Wistar rats showed 10a generated more of its active metabolite than vicagrel. These results suggest that 10a is a potentially superior antiplatelet agent with improved metabolic characteristics and bioactivity, and less dose-related toxicity.