OBJECTIVE Genetic variants in the pharmacokinetic(PK)mechanism are the main underlying factors that modify the antiplatelet efficacy of clopidogrel.Hence,joint analysis of genetic variants that modify pharmacodynamic(PD)and PK responses to clopidogrel should be effective for identifying the genetic variants affecting the antiplatelet response to the drug.METHODS A genome-wide association study was conducted to identify new genetic loci that modify PD responses to clopidogrel and its active metabolite H4 in 115 Chinese patients with coronary heart disease(CHD).RESULTS We identified novel variants in two transporter genes(rs12456693 in SLC14A2 and rs2487032 in ABCA1)and in N6AMT1(rs2254638)associated with clopidogrel-treated P2Y12reaction unit(PRU)and plasma H4 concentration.The associations between these single nucleotide polymorphisms(SNPs)and PK parameters of clopidogrel and H4 were observed in 31 additional CHD patients(P<0.05).The new variants,together with CYP2C19*2 and clinical factors,dramatically improved the predictability of PRU variability to 37.7%compared with the published value of approximately 20%.The function of these SNPs on the activation of clopidogrel was validated in 32 liver S9 fractions,and the N6AMT1 rs2254638 T variant was found to be associated with decreased formation of H4(P=0.0386).Meanwhile,N6AMT1 rs2254638 was further identified to exert a marginal risk effect for MACE in an independent CHD patient cohort(OR:1.428,95%CI:0.978-2.086,P=0.0653,FDR=0.4726).In conclusion,we systematically identified new genetic variants as risk factors for the reduced efficacy of clopidogrel.CONCLUSION Our study findings enhanced the understanding of the absorption and metabolic mechanisms that influence PD responses to clopidogrel treatment. OBJECTIVE Genetic variants in the pharmacokinetic (PK) mechanism are the main underlying factors that modify the antiplatelet efficacy of clopidogrel .ence, joint analysis of genetic variants that modify pharmacodynamic (PD) and PK responses to clopidogrel should be effective for identifying the genetic variants affecting the antiplatelet response to the drug. METHODS A genome-wide association study was conducted to identify new genetic loci that modifies PD responses to clopidogrel and its active metabolite H4 in 115 Chinese patients with coronary heart disease (CHD) .RESULTS We identified novel variants in two transporter genes (rs12456693 in SLC14A2 and rs2487032 in ABCA1) and in N6AMT1 (rs2254638) associated with clopidogrel-treated P2Y12 reaction unit (PRU) and plasma H4 concentration.The associations between these single nucleotide polymorphisms (SNPs) and PK parameters of clopidogrel and H4 The new variants, together with CYP2C19 * 2 and clinical fa ctors, dramatically improved the predictability of PRU variability to 37.7% compared with the published value of approximately 20%. The function of these SNPs on the activation of clopidogrel was validated in 32 liver S9 fractions, and the N6AMT1 rs2254638 T variant was found to be associated with decreased formation of H4 (P = 0.0386) .Meanwhile, N6AMT1 rs2254638 was further identified to exert a marginal risk effect for MACE in an independent CHD patient cohort (OR: 1.428,95% CI: 0.978-2.086, FDR = 0.4726). In conclusion, we systematically identified new genetic variants as risk factors for the reduced efficacy of clopidogrel. CONCLUSION Our study findings enhanced the understanding of the absorption and metabolic mechanisms that influence PD responses to clopidogrel treatment.