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Antiplatelet therapy is essential treatment for acute coronary syndromes (ACS). Current therapies, however, have important limitations affecting their clinical success. Ticagrelor, the first reversible oral P2Y(12) receptor antagonist, provides faster, greater, and more consistent adenosine diphosphate-receptor inhibition than clopidogrel. The phase III PLATelet inhibition and patient Outcomes (PLATO) trial is designed to test the hypothesis that ticagrelor compared with clopidogrel will result in a lower risk of recurrent thrombotic events in a broad patient population with ACS. PLATO is an international, randomized, double-blind, event-driven trial involving >18,000 patients hospitalized for ST-elevation ACS with scheduled primary percutaneous coronary intervention or for non-ST-elevation ACS. After loading doses of ticagrelor 180 mg or clopidogrel 300 mg in a double-blind, double-dummy fashion (with provision for additional 300 mg clopidogrel at percutaneous coronary intervention), patients will receive ticagrelor 90 mg twice daily or clopidogrel 75 mg once daily for 6 to 12 months on top of acetylsalicylic acid. The primary efficacy end point is time to first occurrence of death from vascular causes, myocardial infarction, or stroke. The primary safety variable is PLATO-defined major bleeding. An extensive substudy program will explore the pathophysiology of ACS, indicators of prognosis and response to treatment, mechanisms of effect and safety of the study medications, health economics, and quality of life. The PLATO study will provide a pivotal comparison of the efficacy and safety of ticagrelor with those of clopidogrel in ACS patients, together with extensive information on treatment outcomes in different subsets of ACS in a broad patient population.

Objective The objective of this study was to assess the pharmacokinetic and pharmacodynamic behavior of ticagrelor administered either as crushed (in the semi-upright sitting position) or as integral (in the supine position) tablets in ST-segment elevation myocardial infarction (STEMI) patients undergoing primary percutaneous coronary intervention (PCI). Methods We randomized 20 patients to ticagrelor 180 mg either as 2 integral tablets administered in the supine position (standard administration) or as 2 tablets crushed and dispersed, administered in the semi-upright sitting position. Blood samples were drawn for pharmacokinetic and pharmacodynamic assessment at randomization (0 h) and at 0.5, 1, 2, and 4 h. Results At 1 h, ticagrelor plasma exposure and area under the plasma concentration–time curve from time zero to 1 h (AUC 1 ) (co-primary endpoints) were higher in the crushed versus integral tablets group (median 586 vs. 70.1 ng/mL and 234 vs. 24.4 ng·h/mL, respectively), with a ratio of adjusted geometric means (95 % confidence interval [CI]) of 12.67 (2.34–68.51) [ p  = 0.005] and 19.28 (3.51–106.06) [ p  = 0.002], respectively. Time to maximum plasma concentration was shorter in the crushed versus integral tablets group (median 2 vs. 4 h), with a ratio of adjusted geometric means (95 % CI) of 0.69 (0.49–0.97) [ p  = 0.035]. Parallel findings were observed with AR-C124910XX (active metabolite). Platelet reactivity (VerifyNow ® ) at 1 h was lower with crushed versus standard administration with least squares estimates mean difference (95 % CI) of 92 (−158.4 to 26.6) P2Y 12 reaction units ( p  = 0.009). Conclusions In patients with STEMI undergoing primary PCI, ticagrelor crushed tablets administered in the semi-upright sitting position seems to lead to a faster—compared with standard administration—absorption, with stronger antiplatelet activity within the first hour. Trial registration: ClinicalTrials.gov identifier: NCT02046486.

Ticagrelor (AZD6140) is the first reversibly binding oral P2Y(12) receptor antagonist in development for reduction of clinical thrombotic events in patients with acute coronary syndromes. The purpose of our studies was to determine the effect of single-ascending doses of ticagrelor in healthy subjects. In two randomised, double-blind, placebo-controlled single ascending dose studies, healthy subjects received oral doses of 0.1-100 mg or placebo (n = 25) and 30-400 mg or placebo (n = 13). Absorption of ticagrelor was rapid [median time to peak plasma concentration (t(max)) 1.3-2 h], as was the formation of its main (active) metabolite, AR-C124910XX (t(max) 1.5-3 h). For both ticagrelor and AR-C124910XX, the peak plasma concentration (C(max)) and area under the plasma concentration-time curve from time 0 to infinity (AUC(0-infinity)) increased in an apparently dose-proportional manner over the dose range studied, indicating linear pharmacokinetics. The mean terminal-phase half-life (t(1/2)) was approximately 7-8.5 h for ticagrelor and 8.5-10 h for AR-C124910XX; AR-C124910XX exposure was approximately one third that of ticagrelor. Inhibition of platelet aggregation (IPA) was dose related and was nearly complete at 2 h (mean 88-95%; final extent, with 20 microM adenosine diphosphate ADP) at doses of 100-400 mg. Linear and predictable pharmacokinetics of ticagrelor and AR-C124910XX were observed. A consistent and high IPA was maintained over 2-12 h, gradually decreasing with declining plasma concentration starting around 12 h post-dose, indicating that the IPA is reversible. Ticagrelor was well tolerated, with no serious or dose-related adverse events or notable changes in laboratory values observed.

Purpose Interactions between ticagrelor and atorvastatin or simvastatin were investigated in two-way crossover studies. Methods Both studies were open-label for statin; the atorvastatin study was placebo-controlled for ticagrelor. For atorvastatin, volunteers ( n  = 24) received ticagrelor (loading dose 270 mg; 90 mg twice daily, 7 days) or placebo, plus atorvastatin calcium (80 mg; day 5). For simvastatin, volunteers ( n  = 24) received simvastatin 80 mg, or ticagrelor (loading dose 270 mg; 180 mg twice daily, 7 days) plus simvastatin (80 mg; day 5). In each study, volunteers received the alternate treatment after washout (≥7 days). Results Ticagrelor increased mean atorvastatin maximum plasma concentration (C max ) and area under the plasma concentration-time curve from zero to infinity (AUC) by 23 % and 36 %, respectively. Simvastatin C max and AUC were increased by 81 % and 56 % with ticagrelor. Ticagrelor also increased C max and AUC of analysed atorvastatin metabolites by 13–55 % and 32–67 %, respectively, and simvastatin acid by 64 % and 52 %, respectively. Co-administration of ticagrelor with each statin was well tolerated. Conclusions Exposure to ticagrelor and its active metabolite, AR-C124910XX, was generally unchanged by a single dose of either statin, except for a minor increase in ticagrelor C max in the presence of simvastatin. Effects of ticagrelor on atorvastatin pharmacokinetics were modest and unlikely clinically relevant, while with simvastatin, changes were slightly larger, and simvastatin doses >40 mg with ticagrelor should be avoided.

Remdesivir (RDV), a single diastereomeric monophosphoramidate prodrug that inhibits viral RNA polymerases, has potent in vitro antiviral activity against severe acute respiratory syndrome‐coronavirus 2 (SARS‐CoV‐2). RDV received the US Food and Drug Administration (FDA)’s emergency use authorization in the United States and approval in Japan for treatment of patients with severe coronavirus disease 2019 (COVID‐19). This report describes two phase I studies that evaluated the safety and pharmacokinetics (PKs) of single escalating and multiple i.v. doses of RDV (solution or lyophilized formulation) in healthy subjects. Lyophilized formulation was evaluated for potential future use in clinical trials due to its storage stability in resource‐limited settings. All adverse events were grade 1 or 2 in severity. Overall, RDV exhibited a linear profile following single‐dose i.v. administration over 2 hours of RDV solution formulation across the dose range of 3–225 mg. Both lyophilized and solution formulations provided comparable PK parameters. High intracellular concentrations of the active triphosphate (~ 220‐fold to 370‐fold higher than the in vitro half‐maximal effective concentration against SARS‐CoV‐2 clinical isolate) were achieved following infusion of 75 mg or 150 mg lyophilized formulation over 30 minutes or 2 hours. Following multiple‐doses of RDV 150 mg once daily for 7 or 14 days, RDV exhibited a PK profile similar to single‐dose administration. Metabolite GS‐441524 accumulated ~ 1.9‐fold after daily dosing. Overall, RDV exhibited favorable safety and PK profiles that supported once‐daily dosing.

BackgroundTicagrelor, the first reversible P2Y12 receptor antagonist, exhibits faster onset and offset of antiplatelet effects and more consistent platelet inhibition than clopidogrel in both healthy subjects and patients with stable coronary artery disease.ObjectiveThe objectives of this study were to establish a population pharmacokinetics (PK) and pharmacodynamics (PD) model of ticagrelor and to provide a theoretical basis for the optimization of ticagrelor treatment in clinic.MethodsA single oral dose of 180 mg ticagrelor was administered to 14 healthy male subjects in a randomized study. Common single-nucleotide polymorphisms (SNPs) in biotransformation enzymes CYP3A4 and CYP3A5 (CYP3A4*1G and CYP3A5*3) were genotyped by PCR-direct sequencing. Blood samples were collected to measure plasma concentrations of ticagrelor and its active metabolite AR-C124910XX and maximal platelet inhibition. Various models were evaluated to characterize the pharmacokinetics of ticagrelor and AR-C124910XX as well as their PK-PD relationship. Covariates that may potentially affect PK or PD of ticagrelor and AR-C124910XX were included and assessed. Simulation for dosage regimen was performed based on the final PK-PD model.ResultsTicagrelor and AR-C124910XX PK were best described by a two-compartment model with first-order transit absorption model. CYP3A4*1G increased clearance for AR-C124910XX, but had no significant effect on ticagrelor clearance. The relationship between concentration and platelet response of ticagrelor was best described by a turnover model. Simulation results indicated that a lower dosage regimen of 30 mg maintenance dose (MD) could produce an anticipated anti-platelet response in comparison to the routine clinical dosage regimen (180 mg loading dose (LD), 90 mg MD).ConclusionOur study developed a population PK-PD model for ticagrelor and further simulation for dosage regimen was performed based on the final model. Compared to the current recommended dosage regimen (180 mg LD, 90 mg MD), our simulation result of a relatively lower dose (30 mg MD) could also obtain an acceptable anti-platelet response, which may provide a reference for further dosage regimen design in Chinese population.

Background and Objectives: Ticagrelor, the first reversibly binding oral P2Y 12 receptor antagonist, improves outcomes in patients with acute coronary syndromes (ACS) compared with clopidogrel. In the ONSET-OFFSET study (parallel group trial) and the RESPOND study (crossover trial), the pharmacodynamic effects of ticagrelor were compared with clopidogrel in patients with coronary artery disease (CAD). We now report the pharmacokinetic analyses of ticagrelor, and the exposure-inhibition of platelet aggregation (IPA) relationships from these studies. Patients and Methods: Patients were treated with ticagrelor (180 mg loading dose, 90 mg twice daily maintenance dose) or clopidogrel (600 mg loading dose, 75 mg once daily maintenance dose) in addition to aspirin (acetylsalicylic acid) [75–100 mg once daily]. Ticagrelor administration was for 6 weeks in ONSET-OFFSET. In RESPOND, ticagrelor was given for 14 days before or after 2 weeks of clopidogrel in patients classified as clopidogrel responders or non-responders. Pharmacokinetics and IPA were evaluated following the loading and last maintenance doses. Exposure-IPA relationships were evaluated using a sigmoid maximum effect (E max ) model. Outcome Measures: The outcome measures were ticagrelor and AR-C124910XX (active metabolite) pharmacokinetics and exposure-IPA relationships in both trials, including the effect of prior clopidogrel exposure, and effects in clopidogrel responders and non-responders in RESPOND. Results: In ONSET-OFFSET, maximum (peak) plasma concentration (C max ), time to C max (t max ) and area under the plasma concentration-time curve from time 0 to 8 hours (AUC 8 ) for ticagrelor were 733 ng/mL, 2.0 hours and 4130 ng · h/mL, respectively; and for AR-C124910XX were 210 ng/mL, 2.1 hours and 1325 ng · h/mL, respectively. E max estimates were IPA > 97%. Trough plasma ticagrelor (305 ng/mL) and AR-C124910XX (121 ng/mL) concentrations were 5.2 and 7.7 times higher than respective concentration producing 50% of maximum effect (EC 50 ) estimates. In RESPOND, ticagrelor mean C max and AUC 8 following 2-week dosing were comparable between clopidogrel responders (724 ng/mL and 3983 ng · h/mL, respectively) and non-responders (764 ng/mL and 3986 ng · h/mL, respectively). Pharmacokinetics of ticagrelor were unaffected by prior clopidogrel dosing. E max estimates were IPA > 96% for both responders and non-responders. Trough plasma concentrations were sufficient to achieve high IPA. Conclusions: Ticagrelor pharmacokinetics in stable CAD patients were comparable to previous findings in stable atherosclerotic and ACS patients, and were not affected by prior clopidogrel exposure or clopidogrel responsiveness. Ticagrelor effectively inhibited platelet aggregation, and trough plasma concentrations of ticagrelor and AR-C124910XX were sufficient to result in high IPA in stable CAD patients.

The objective of the study was to determine the prevalence of high on-treatment platelet reactivity (HPR) in coronary artery disease patients enrolled in the ONSET/OFFSET and RESPOND studies. HPR has been linked to the occurrence of adverse events after stenting in patients treated with clopidogrel (C) and aspirin. Prevalence of HPR after treatment with ticagrelor (T), a reversible oral P2Y 12 receptor antagonist developed to overcome the limitations of C, is unknown. Patients were treated with T (n = 106) or C (n = 103) on top of aspirin therapy. HPR was defined by published cutoff points associated with post–percutaneous coronary intervention ischemic risk: >59% 20 μM adenosine diphosphate–induced aggregation (light transmittance aggregometry), >235 P2Y12 reaction unit by VerifyNow P2Y 12 assay (VerifyNow, San Diego, CA), and >50% platelet reactivity index by vasodilator-stimulated phosphoprotein phosphorylation assay (VASP-P). Proportion differences for T versus C were analyzed by χ 2 test for each time point. Correlations ( R) were analyzed by the Pearson method. Ticagrelor was associated with a significantly lower prevalence of HPR (0%-8%) compared with C (21%-81%) at 2, 4, 8, and 24 hours and ≥2 weeks postdosing ( P < .0001, for all assays). The R values between light transmittance aggregometry and VerifyNow/VASP-P were all ≥0.43, P < .0001. The above data represent the largest serial pharmacodynamic evaluation of the comparative effects of T versus C. Ticagrelor was rapidly and consistently associated with a very low prevalence of HPR compared with C, as determined by multiple established methods to measure platelet reactivity. These results provide a mechanism for the lower ischemic event rate associated with T therapy reported in the PLATO trial.

Ticagrelor has a greater antiplatelet efficacy than clopidogrel but may be accompanied by an increased risk of bleeding. This study evaluated the antiplatelet effect and pharmacokinetic profile of low-dose ticagrelor in healthy Chinese volunteers. Thirty healthy subjects were randomized to receive standard-dose ticagrelor (180-mg loading dose, 90-mg twice daily [bid] [n = 10]), low-dose ticagrelor (90-mg loading dose, 45-mg bid [n = 10]), or clopidogrel (600-mg loading dose, 75-mg once daily [n = 10]). Platelet reactivity was assessed by using the VerifyNow P2Y12 assay at baseline and 0.5, 1, 2, 4, 8, 24, 48 and 72 hours post-dosing. The ticagrelor and AR-C124910XX concentrations were measured for pharmacokinetic analysis. The percentage inhibition of P2Y12 reaction units was higher in the low-dose and standard-dose ticagrelor group than in the clopidogrel group at 0.5, 1, 2, 4, 8 and 48 hours post-dosing ( P  < 0.05 for all), but did not differ significantly between the two ticagrelor doses at any time-point ( P  > 0.05). The plasma ticagrelor and ARC124910XX concentrations were approximately 2-fold higher with standard-dose versus low-dose ticagrelor. No serious adverse events were reported. In conclusion, low-dose ticagrelor achieved faster and higher inhibition of platelet functions in healthy Chinese subjects than did clopidogrel, with an antiplatelet efficacy similar to that of standard-dose ticagrelor.

RNA viruses with pandemic potential pose a significant global health risk. The adenosine nucleoside analog GS-441524 is metabolized to its active GS-443902 triphosphate metabolite to inhibit a broad spectrum of RNA viruses. Intravenous (IV) remdesivir (RDV) and oral obeldesivir (ODV) are phosphoramidate and isobutyryl-ester prodrugs of GS-441524, respectively. Following administration, both RDV and ODV show rapid and broad tissue distribution, form the same GS-443902 metabolite in target tissues, and demonstrate promising in vivo efficacy across several RNA virus infection models. In an African green monkey SARS-CoV-2 infection model, respective RDV and ODV treatments yielded similar antiviral efficacy. Here, we compare the in vitro and in vivo pharmacokinetics (PK) and metabolism of RDV and ODV to highlight both similarities and differences in their absorption, metabolism, distribution, and excretion profiles. The distinct route of administration and metabolic fate of each prodrug produced in vivo PK and metabolism profiles with differential GS-441524 to tissue GS-443902 relationships, thereby supporting alternate methods for predicting human efficacious doses. Overall, a metabolism-directed prodrug design enabled optimized delivery of the identical active GS-443902 metabolite through different routes of administration, supporting broader applications of the same nucleoside analog across an expanded spectrum of potential antiviral indications.