Impact of platelet reactivity on long-term clinical outcomes and bleeding events in Japanese patients receiving antiplatelet therapy with aspirin.

AIM: Aspirin is an antiplatelet drug widely used for the prevention of cardiovascular disease; however, it is known to increase bleeding events. A low response to aspirin was reported to correlate with poor prognosis in patients undergoing antiplatelet therapy with aspirin. The aim of this study was to evaluate the impact of the antiplatelet activity of aspirin on cardiovascular and bleeding events in Japanese patients. METHODS: We analyzed the clinical course of 239 Japanese patients undergoing antiplatelet therapy with aspirin for a median of 64 months in this study. Their residual platelet reactivity was examined at enrollment and after 2 years. The co-primary endpoints were the occurrence of major adverse cardiac and cerebrovascular events (MACCEs) and bleeding events. RESULTS: The annual incidence of MACCEs and major bleeding events was 3.7% and 0.48%, respectively. With defined criteria, 67 patients (28%) were classified as low responders based on the platelet aggregability measured at enrollment. Low response to aspirin was not associated with increased MACCEs, while it clearly increased MACCEs in patients less than 70 years old (low responders 36.9% vs. responders 14.8%, log rank p=0.008). Five major types of bleeding occurred in the responders, but not in low responders, although the difference was not statistically significant (p= 0.07). CONCLUSION: Low response to aspirin was not associated with the increase of long-term MACCEs, while it increased MACCEs in patients less than 70 years old; however, it tended to decrease major bleeding events in Japanese patients.

Prediction of clopidogrel low responders by a rapid CYP2C19 activity test.

AIM: Clopidogrel, an essential drug for the prevention of stent thrombosis, is a prodrug activated by CYP enzyme family including CYP2C19. It is known that activity-defective polymorphisms of CYP2C19 (CYP2C19*2 and*3) are associated with reduced clopidogrel efficacy and poor prognosis. Recently, the (13)C-pantoprazole breath test is developed to evaluate the CYP2C19 activity. The aim of this study is to evaluated the efficiency of the CYP2C19 activity test as a predictor of antiplatelet effect of clopidogrel. METHODS: The CYP2C19 activity and the antiplatelet effect of clopidogrel were evaluated in 27 healthy volunteers. Change of the carbon isotope ratios ((13)CO(2)/(12)CO(2)) in expiration gas between before and after (13)C-pantoprazole intake was evaluated as delta over baseline (DOB) ratio (‰). RESULTS: DOB at 30 min was significantly lower in poor metabolizers (PMs) than extensive metabolizers (EMs) and intermediate metabolizers (IMs) (EM vs. PM, p=0.0108; IM vs. PM, p=0.016). The antiplatelet effect of clopidogrel was significantly different in three groups (inhibition of platelet aggregation: p=0.0148, P2Y12 reaction unit: p=0.0241). DOB at 30 min was correlated with the antiplatelet effect of clopidogrel. A cut-off value of DOB at 30 min below 1.0‰ predicted PMs with 96% specificity and 100% sensitivity. CONCLUSIONS: The (13)C-pantoprazole breath test can detect CYP2C19 PMs and predict low responders to clopidogrel rapidly.

Characterization of the antiplatelet effect of aspirin at enrollment and after 2-year follow-up in a real clinical setting in Japan.

BACKGROUND: Aspirin is an antiplatelet drug widely used for the prevention of cardiovascular diseases. It has been reported that some patients who exhibit a reduced antiplatelet effect of aspirin have higher cardiovascular risk. It is still controversial whether the antiplatelet effect of aspirin diminishes after a few years of treatment. This study aimed to evaluate the antiplatelet effect of aspirin and its 2-year change in Japanese patients. METHODS AND RESULTS: Collagen-induced platelet-aggregability was measured at enrollment by conventional optical aggregometer in 239 patients undergoing antiplatelet therapy with aspirin alone. Among them, 167 patients were evaluated after 2 years. Whole blood aggregability based on the screen-filtration method was also evaluated. Optical aggregometer studies showed that 27% of patients were low-responders. Multivariate analyses revealed that female sex and non-use of calcium-channel blockers were associated with low responsiveness. The antiplatelet effect of aspirin did not decrease after 2 years. Similar data were obtained with the whole blood aggregometer. CONCLUSIONS: In this Japanese patient group, 27% were low-responders to aspirin, and the antiplatelet effect of aspirin did not decrease after a 2-year interval.

Impact of CYP2C19 polymorphisms on the antiplatelet effect of clopidogrel in an actual clinical setting in Japan.

BACKGROUND: The P2Y(12) adenosine diphosphate (ADP) receptor blocker, clopidogrel, an essential drug for the prevention of stent thrombosis after percutaneous coronary intervention (PCI), is a prodrug that requires CYP2C19- and CYP3A4-mediating activation. CYP2C19*2 and *3 polymorphisms are known to lack enzymatic activity. CYP2C19 polymorphisms have been reported to exhibit weaker antiplatelet response to clopidogrel in healthy subjects. The effect of polymorphisms of CYP2C19, CYP3A4 and P2Y(12) on the antiplatelet effect of clopidogrel in clinical patients was examined in the present study. METHODS AND RESULTS: Single nucleotide polymorphisms of CYP2C19*2, *3, CYP3A4 (IVS10 +12G>A) and P2Y(12) (T744C) were determined in 25 PCI-scheduled patients who had been systematically analyzed for the antiplatelet effect of clopidogrel in a previous study. On the basis of CYP2C19 genotype, 11 patients (44%) were classified as extensive metabolizers (EMs), 8 (32%) as intermediate metabolizers (IMs) and 6 (24%) as poor metabolizers (PMs). The rates of inhibition of 5 micromol/L ADP-induced platelet aggregation by clopidogrel intake at 48 h were 31.6 +/-14.3% in EMs, 18.4 +/-10.0% in IMs (P=0.04 vs EMs) and 16.0 +/-13.0% in PMs (P=0.02 vs EMs). CONCLUSIONS: CYP2C19 polymorphisms are frequent in Japanese, and the antiplatelet effect of clopidogrel is strongly affected by them in the real-world clinical setting.

Clopidogrel resistance in Japanese patients scheduled for percutaneous coronary intervention.

BACKGROUND: Dual antiplatelet therapy with acetylsalicylic acid (ASA) and a P2Y(12) ADP-receptor blocker is standard for prevention of coronary stent thrombosis. Clopidogrel, a 2(nd)-generation P2Y(12) blocker, has recently become available in Japan and this study aimed to evaluate its antiplatelet effects in Japanese patients. METHODS AND RESULTS: Thirty Japanese patients scheduled for elective coronary stent implantation were enrolled. Under low-dose ASA therapy, 300 mg clopidogrel was loaded on the 1(st) day and a daily 75-mg dose was administered on the following days. Assessed by optical aggregometer, rapid inhibition occurred at 4 h, when the inhibition of platelet aggregation rate (IPA) was 16.4+/-12.8% using 5 mumol/L ADP as the stimulus. The antiplatelet efficacy of clopidogrel was reasonably constant in each patient throughout the study period, although there was a broad inter-individual variation. At 48 h after clopidogrel loading, the ratios of responders (IPA > or =30%), hypo-responders (10%< or =IPA<30%), and non-responders (IPA <10%) were 36%, 50%, and 14%, respectively. CONCLUSIONS: The antiplatelet effectiveness of clopidogrel appeared individual-specific with wide inter-individual variation. The rate of clopidogrel non-responders was 14% among the examined Japanese patients.

Evaluation of the antiplatelet effects of cilostazol, a phosphodiesterase 3 inhibitor, by VASP phosphorylation and platelet aggregation.

BACKGROUND: Cilostazol, a phosphodiesterase 3 inhibitor, is an antiplatelet drug that is widely used for preventing cardiovascular events, although, to date, there are few methods for evaluating its effects. METHODS AND RESULTS: Blood samples were taken at baseline and at 3 and 12 h in 10 healthy male subjects after 100 mg cilostazol intake. Each sample was examined by Western blot for phosphorylation levels of vasodilator-stimulated phosphoprotein (VASP), an abundant cAMP-dependent kinase substrate in platelets, and by the optical aggregometer for ADP- and collagen-induced aggregation, before and after 8 nmol/L prostaglandin E(1) (PGE(1)) treatment. Cilostazol intake did not affect VASP phosphorylation levels or the maximal aggregation rates without PGE(1) treatment. However, cilostazol intake apparently enhanced PGE(1)-induced VASP phosphorylation and PGE(1)-mediated reduction of ADP-and collagen-induced maximal aggregation rates. Levels of VASP phosphorylated at Ser157 were correlated and the maximal aggregation rates induced by ADP were inversely correlated with cilostazol concentrations in the plasma. CONCLUSION: The antiplatelet effects of cilostazol intake could be evaluated by measuring VASP phosphorylation levels and maximal aggregation rates in platelets by ex vivo treatment with a low concentration of PGE(1).