Disease Susceptibility Clinical Trial
Official title:
Clopidogrel Pharmacogenomics Project
Loss-of-function mutation of the gene encoding the CYP450 2C19 enzyme has emerged as a likely determinant of resistance to clopidogrel therapy. The primary hypothesis of the proposed research is that among patients with confirmed loss-of-function alleles of the CYP2C19 gene, increasing the maintenance clopidogrel dose from 75 to 150 mg will result in significant reduction in the rate of measured clopidogrel resistance defined by multiple measures of platelet function
The first phase of the clinical trial will involve subject recruitment and informed consent
for genetic testing. Because the target population is patients with stable coronary artery
disease, patients will be recruited from the outpatient setting during clinic visits or at
the time of outpatient cardiac catheterization. It is expected that all potential candidates
will be initially screened for eligibility by their treating cardiologist. If a patient
agrees to undergo formal screening, they will be approached by a member of the research team
and receive a written summary of the clinical trial protocol that will be reviewed with the
trial personnel. The initial informed consent will allow the patient to undergo genetic
testing and baseline VerifyNow assay, and will also give the trial personnel permission to
contact the patient by phone if they are found to be eligible for the interventional phase of
the trial. The goal for enrollment in the genetic testing portion of this clinical trial is
200 patients.
If the genetic testing results confirm that the patient is a candidate for the interventional
study, they will be contacted and asked to make an outpatient appointment to initiate the
interventional study protocol. The therapeutic portion of this study will be a randomized,
unblinded cross-over comparison of two clopidogrel dosing strategies. It is anticipated that
all eligible patients will have continued their previous chronic clopidogrel therapy with
standard dosing of 75 mg/day. Because all patients will be receiving chronic clopidogrel at
the initiation of the intervention protocol, steady state levels should be present in all
patients. Dose dependent inhibition of platelet aggregation can be seen two hours after a
single oral dose of clopidogrel. Repeated doses of 75mg daily produce steady state inhibition
between day 3 and day 7 of administration.
Patients who agree to participate in the therapeutic protocol, and who meet the eligibility
criteria, will be randomized to an initial dosing strategy of 75 or 150 mg daily for a
minimum of 30 days. At day 30 (+/- 5 days), patients will return for repeat platelet function
testing. In a randomly selected subset of 15 patients, blood will be tested for the active
metabolite of clopidogrel. At that time, there will be a crossover with those patients
receiving 75 mg qD increased to 150 mg qD and those receiving 150 mg qD decreased to 75 mg
qD. At day 60 (+/- 5 days), participants will again return for comprehensive platelet
function testing and a second randomly selected group of patients will undergo testing for
clopidogrel metabolites. Chronic clopidogrel dosing will be reduced to 75mg in all
participants. Please see the attached schedule of events for a summary of the trial schedule.
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