This study is being conducted to determine if smoking will influence the platelet aggregation inhibition ability of clopidogrel and prasugrel. It will also determine if smoking has any effect on the plasma concentrations of the active metabolite of prasugrel and the active and inactive metabolites of clopidogrel.

The primary hypothesis is that smoking status will influence the antiplatelet effects and active metabolite concentrations of clopidogrel but will have no impact on prasugrel's antiplatelet effects or active metabolite concentrations.

Subjects will be stratified according to smoking status prior to being randomized to 1 of the 2 treatment sequences: prasugrel 10 mg daily for 10 days followed by clopidogrel 75 mg daily for 10 days or clopidogrel 75 mg daily for 10 days followed by prasugrel 10 mg daily for 10 days. There will be a 14-day Washout Period between Active Treatment Period 1 (when subjects receive the first drug of the sequence) and the second Active Treatment Period 2 (Period 3) (when subjects receive the second drug of the sequence). All subjects will remain on the same dose of aspirin from baseline throughout the study.

Inclusion Criteria:

• Male or female subjects > or = 18 years and <75 years of age;

• Weight > or = 60 kg;

• On aspirin therapy (81 mg to 325 mg daily) at the time of screening and able to maintain a consistent aspirin dosing regimen from the baseline visit through the final study visit;

• Subjects who do not have contraindications for a thienopyridine (ie, prasugrel, clopidogrel, or ticlopidine) and have a history of stable atherosclerosis represented by CAD, defined as any of the following:

  • Chronic stable angina;
  • Documented prior ACS event > or = 30 days before screening and not currently prescribed or currently on thienopyridine therapy;
  • Previous coronary revascularization including percutaneous transluminal coronary angioplasty, stent, or coronary artery bypass graft;
  • Coronary Artery Disease (> or = 40% obstruction) in at least one coronary vessel after angiography;
  • Documented history of positive stress test; or
  • High coronary artery calcium score (> or = 90th percentile for age and gender) determined by cardiac computed tomography scan;

• Current smokers who smoke > or = ½ pack per day of cigarettes with a NicAlert™ level of 6;

• Non-smokers with a NicAlert level of 0, 1, or 2;

• Female subjects who meet one of the following:

  • Women of childbearing potential with a negative serum pregnancy test at screening, who are not breastfeeding, do not plan to become pregnant during the study, and agree to use an approved method of birth control during the study. Approved methods of birth control are intrauterine device, diaphragm plus spermicide, or female condom plus spermicide. Abstinence, partner's use of condoms, partner's vasectomy, and hormonal contraceptives are NOT acceptable methods of contraception;
  • Women who have been postmenopausal for at least 1 year or have had a hysterectomy, bilateral salpingo-oophorectomy, or tubal ligation at least 6 months prior to signing the Informed Consent Form (ICF); and

• Subjects with a competent mental condition to provide written informed consent before entering the study.

Exclusion Criteria:

• Subjects who received a bare metal stent and/or a drug-eluting stent within the last 12 months;

• Subjects who have had an angiogram < or = 7 days before randomization;

• Any other formal indication for the use of a thienopyridine;

• Subjects with a history of refractory ventricular arrhythmias;

• Subjects with a history of an implantable defibrillator device;

• Subjects with a history or evidence of congestive heart failure (New York Heart Association Class III or above) within 6 months prior to screening;

• Subjects with significant hypertension (systolic blood pressure >180 mmHg or diastolic blood pressure >110 mmHg) at either the time of screening or baseline assessment;

• Bleeding risk exclusion criteria:

  • Any known contraindication to treatment with an anticoagulant or antiplatelet agent;
  • Prior history or clinical suspicion of cerebral vascular malformations, intracranial tumor, transient ischemic attack, or stroke, or recent history (within 3 months) of head trauma;
  • Prior history or presence of significant bleeding disorders (eg, hematemesis, melena, severe or recurrent epistaxis, hemoptysis, hematuria, or intraocular bleeding);
  • History (within the last 5 years) or presence of gastric ulcers. Previous history of duodenal ulcer is acceptable but must have been successfully surgically or medically treated with no further evidence of disease in the past 6 months (from screening);
  • Prior history of abnormal bleeding tendency (ie, prolonged bleeding on dental extraction, tonsillectomy, or previous surgical procedure);
  • Known prior history or presence of thrombocytopenia (platelet count <100,000/mm3) or thrombocytosis (platelet count >500,000/mm3) or recent history (within 6 months) of hemoglobin <10 mg/dL;
  • International normalized ratio (INR) >1.5 or activated partial thromboplastin time (aPTT) > upper limit of normal (ULN) of laboratory reference range at screening;
  • History of major surgery, severe trauma, fracture, or organ biopsy within 3 months prior to enrollment;

• Prior/concomitant therapy exclusion criteria:

  • Subjects taking prasugrel, clopidogrel, ticlopidine, cilostazol, dipyridamole, warfarin, heparin, direct thrombin inhibitors, or GPIIb/IIIa inhibitors < or = 10 days prior to randomization or during study participation;
  • Use (or planned use) of fibrinolytic agents within 30 days before screening or during study participation;
  • Subjects receiving treatment with nonsteroidal anti-inflammatory drugs or cyclooxygenase-2 inhibitors exceeding 3 doses per week;
  • Subjects taking proton pump inhibitors (eg, lansoprazole, esomeprazole, omeprazole, pantoprazole, or rabeprazole) < or = 10 days prior to randomization or during study participation;
  • Use or planned use of any herbal supplements < or = 10 days prior to randomization or during study participation;
  • Use or planned use of the following strong inhibitors of various CYP pathways < or =10 days prior to randomization or during study participation: ciprofloxacin, cimetidine, fluvoxamine, estradiol, ethinylestradiol, fluconazole, amiodarone, indinavir, nelfinavir, ritonavir, saquinavir, clarithromycin, erythromycin, telithromycin, itraconazole, ketoconazole, fluconazole, nefazodone, or grapefruit-containing products;
  • Use or planned use of the following strong inducers of various CYP pathways < or = 10 days prior to randomization or during study participation: rifampin, barbiturates, carbamazepine, dexamethasone, or St. John's Wort;
  • Female subjects taking hormonal contraception or hormonal replacement therapy during study participation;

• General exclusion criteria:

  • Investigative site personnel directly affiliated with the study or immediate family of investigative site personnel directly affiliated with the study. Immediate family is defined as a spouse, parent, child, or sibling, whether biological or legally adopted;
  • Daiichi Sankyo or Eli Lilly employees;
  • Currently enrolled in, or discontinued within the last 30 days from, any clinical study involving an investigational drug or device;
  • Have previously completed or withdrawn from this study;
  • Women who are known to be pregnant and/or who receive a positive serum pregnancy test result, and/or who have given birth within the past 90 days, and/or who are breastfeeding;
  • Results of clinical laboratory tests at the time of screening that are judged to be clinically significant for the subject, as determined by the Investigator;
  • Known allergies or intolerance to aspirin and/or thienopyridines (prasugrel, clopidogrel, or ticlopidine);
  • Evidence of significant active neuropsychiatric disease, alcohol abuse, or drug abuse, in the Investigator's opinion;
  • Evidence of active hepatic disease or any of the following: positive human immunodeficiency virus antibodies; positive hepatitis C antibody; positive hepatitis B surface antigen; serum alanine transaminase, aspartate transaminase, or gamma-glutamyltransferase > or = 3 × ULN of laboratory reference range; or bilirubin > or = 2 × ULN of laboratory reference range at screening;
  • Subjects who are unwilling to make themselves available for the duration of the study and who will not abide by the research unit policy and procedure and study restrictions.

De-identified individual participant data (IPD) and applicable supporting clinical trial documents may be available upon request at https://vivli.org/. In cases where clinical trial data and supporting documents are provided pursuant to our company policies and procedures, Daiichi Sankyo will continue to protect the privacy of our clinical trial participants. Details on data sharing criteria and the procedure for requesting access can be found at this web address: https://vivli.org/ourmember/daiichi-sankyo/

Studies for which the medicine and indication have received European Union (EU) and United States (US), and/or Japan (JP) marketing approval on or after 01 January 2014 or by the US or EU or JP Health Authorities when regulatory submissions in all regions are not planned and after the primary study results have been accepted for publication.

Formal request from qualified scientific and medical researchers on IPD and clinical study documents from clinical trials supporting products submitted and licensed in the United States, the European Union and/or Japan from 01 January 2014 and beyond for the purpose of conducting legitimate research. This must be consistent with the principle of safeguarding study participants' privacy and consistent with provision of informed consent.