title: Pharmacokinetics, pharmacodynamics, safety and tolerability of multiple ascending doses of ticagrelor in healthy volunteers.
abstract: BACKGROUND
  The antiplatelet agent clopidogrel is currently the recommended treatment for acute coronary syndrome (ACS). Inhibition of platelet aggregation (IPA) with clopidogrel is insufficient, which increases the risk for recurrent ischaemic events. Therefore, there is a need for antiplatelet agents with improved IPA. Ticagrelor (AZD6140) is a new antiplatelet agent in clinical development for reduction of thrombotic events in patients with ACS.
  
  
  CONCLUSIONS
  This study assesses the optimal dosing schedule for ticagrelor in healthy volunteers and compares the degree of IPA with clopidogrel. Our findings illustrate that the pharmacokinetics of ticagrelor are predictable and are associated with consistent inhibition of platelet activity. IPA with ticagrelor was greater and better sustained at high levels with twice daily ticagrelor than once daily regimens.
  
  
  OBJECTIVE
  To determine the pharmacokinetics, pharmacodynamics, safety and tolerability of multiple oral doses of ticagrelor, a P2Y(12) receptor antagonist, in healthy volunteers.
  
  
  METHODS
  This was a randomized, single-blind, placebo-controlled, ascending dose study. Thirty-two subjects received ticagrelor 50-600 mg once daily or 50-300 mg twice daily or placebo for 5 days at three dose levels in two parallel groups. Another group of 16 subjects received a clopidogrel 300 mg loading dose then 75 mg day(-1), or placebo for 14 days.
  
  
  RESULTS
  Ticagrelor was absorbed with median t(max) 1.5-3 h, exhibiting predictable pharmacokinetics over the 50-600 mg dose range. Mean C(max) and AUC for ticagrelor and its main metabolite, AR-C124910XX, increased approximately dose-proportionately (approximately 2.2- to 2.4-fold with a twofold dose increase) over the dose range. Inhibition of platelet aggregation (IPA) with ticagrelor was greater and better sustained at high levels with ticagrelor twice daily vs. once daily regimens. Throughout dosing, more consistent IPA was observed at doses > or = 300 mg once daily and > or = 100 mg twice daily compared with clopidogrel. Mean IPA with ticagrelor > or = 100 mg twice daily was greater and less variable (93-100%, range 65-100%) than with clopidogrel (77%, range 11-100%) at trough concentrations. No safety or tolerability issues were identified.
  
  
  CONCLUSIONS
  Multiple dosing provided predictable pharmacokinetics of ticagrelor and its metabolite over the dose range of 50-600 mg once daily and 50-300 mg twice daily with C(max) and AUC(0,t) increasing approximately dose-proportionally. Greater and more consistent IPA with ticagrelor at doses > or = 100 mg twice daily and > or = 300 mg once daily were observed than with clopidogrel. Ticagrelor at doses up to 600 mg day(-1) was well tolerated.
authors.affiliation: AstraZeneca LP, Wilmington, DE 19850-5437, USA.
authors.forename: Kathleen
authors.initials: K
authors.lastname: Butler
authors.forename: Renli
authors.initials: R
authors.lastname: Teng
mesh_terms: D000241:Adenosine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000493:pharmacokinetics / Q000494:pharmacology; D000328:Adult; D000077144:Clopidogrel; D004305:Dose-Response Relationship, Drug; D005215:Fasting / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010974:Platelet Aggregation / Q000187:drug effects*; D010975:Platelet Aggregation Inhibitors / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000494:pharmacology; D058925:Receptors, Purinergic P2Y12; D000077486:Ticagrelor; D013988:Ticlopidine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000493:pharmacokinetics / Q000494:pharmacology; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D010975:Platelet Aggregation Inhibitors; D058925:Receptors, Purinergic P2Y12; D000077144:Clopidogrel; D000077486:Ticagrelor; D000241:Adenosine; D013988:Ticlopidine