Pharmacodynamic Effect of Switching Therapy in Patients With High On-Treatment Platelet Reactivity and Genotype Variation With High Clopidogrel Dose Versus Prasugrel

BACKGROUND: High on-treatment platelet reactivity (HTPR) is associated with adverse outcomes. We aim to compare the novel thienopyridine prasugrel versus double-dose clopidogrel in patients with HTPR and explore the interaction between CYP2C19 genotype and both drugs. METHODS AND RESULTS: Consecutive stable patients undergoing percutaneous coronary intervention were screened with the Multiplate Analyzer P2Y12 assay, defining HTPR as area under the curve >450. Those with HTPR were randomized to prasugrel (10 mg/day) or high-dose clopidogrel (150 mg/day) for 2 weeks and then crossed-over to, respectively, clopidogrel and prasugrel, repeating the P2Y12 assay at the end of each cycle. Clinical follow-up (until 3 months) and CYP2C19 genotyping was performed in all patients. The primary end point was platelet reactivity after 14 days of prasugrel versus high-dose clopidogrel. Thirty-two patients were randomized to prasugrel and then high-dose clopidogrel or to high-dose clopidogrel followed by prasugrel. Prasugrel was associated with a significantly lower platelet reactivity than high-dose clopidogrel was (325.8 versus 478.5 area under the curve, P=0.028). No patient treated with prasugrel exhibited HTPR, whereas 9 (28.1%) receiving high-dose clopidogrel still had prevalence of HTPR (P=0.001). Similar findings were obtained changing cutoffs or considering platelet reactivity as a continuous variable. Genotyping showed the same efficacy between high-dose clopidogrel and prasugrel in the 18 (56.3%) CYP2C19*2 noncarriers (HTPR in 12.5% versus 0, P=0.274), whereas it was significantly worse in the 14 (43.7%) carriers (HTPR in 43.7% versus 0, P=0.003). CONCLUSIONS: HTPR is successfully abolished by therapy with prasugrel irrespective of CYP2C19 genotype. Conversely, high-dose clopidogrel can address HTPR only in CYP2C19*2 noncarriers. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT01465828.