Association of platelet response to cilostazol with clinical outcome and CYP genotype in patients with cerebral infarction.

INTRODUCTION: Cilostazol, an anti-platelet drug that inhibits phosphodiesterase 3, is beneficial for patients with atherothrombosis. In contrast to other anti-platelet drugs such as aspirin and thienopyridines, little information is available on the relationship between platelet responses to cilostazol and clinical outcomes.

MATERIALS AND METHODS: We conducted a prospective study on patients with cerebral infarction who were treated with cilostazol. The platelet response to cilostazol was assessed with our new assay for the phosphorylation of vasodilator-stimulated phosphoprotein (VASP) subsequent to the pharmacological action of cilostazol. Patients were followed up for 2 years and the relationship between VASP assay results and the recurrence of thrombotic events was examined. We also investigated the effects of CYP3A5 and CYP2C19 genotypes involved in the metabolism of cilostazol on the platelet response to cilostazol.

RESULTS: Among the 142 patients enrolled, 130 completed the 2-year follow-up and the recurrence of thrombotic events was noted in 8 (6.2%). VASP phosphorylation levels were significantly lower in patients with than in those without recurrence. The combined genotype of CYP3A5*1/*3 and CYP2C19*1/*1 was associated with a low level of VASP phosphorylation, while either genotype was not. A multivariate analysis showed that high residual platelet reactivity during the cilostazol treatment, which was defined by a low response of platelet VASP phosphorylation to cilostazol, was an independent risk factor for the recurrence of thrombotic events.

CONCLUSION: A low platelet response to cilostazol determined by a new platelet assay was associated with the recurrence of thrombotic events in patients with cerebral infarction.