Search

Peng-fei Tang,1,* Xiang Zheng,2,* Xiao-xia Hu,3 Cheng-cheng Yang,4 Zhe Chen,5 Jian-chang Qian,6 Jian-ping Cai,7 Guo-xin Hu1,6 1Affiliated Yueqing Hospital, Wenzhou Medical University, Wenzhou 325600, Zhejiang, People’s Republic of China; 2Dong Yang People’s Hospital, Jinhua, Zhejiang 322100, People’s Republic of China; 3Affiliated Jinhua Hospital, Zhejiang University School of Medicine, Jinhua, Zhejiang 321000, People’s Republic of China; 4Ningbo First Hospital, Ningbo 315010, Zhejiang, People’s Republic of China; 5Wenzhou People’s Hospital, Wenzhou, Zhejiang 325000, People’s Republic of China; 6School of Pharmaceutical Sciences, Wenzhou Medical University, Wenzhou 325000, Zhejiang, People’s Republic of China; 7The Key Laboratory of Geriatrics, Beijing Hospital and Beijing Institute of Geriatrics, Ministry of Health, Beijing 100730, People’s Republic of China*These authors contributed equally to this workCorrespondence: Guo-xin HuAffiliated Yueqing Hospital, Wenzhou Medical University, Wenzhou, Zhejiang 325600, People’s Republic of ChinaTel/Fax +865778668 9983Email hgx@wmu.edu.cnJian-ping CaiThe Key Laboratory of Geriatrics, Beijing Hospital and Beijing Institute of Geriatrics, Ministry of Health, Beijing 100730, People’s Republic of ChinaEmail caijp61@vip.sina.comAim: We aimed to systematically examine the effects of enzymatic activity of 38 human CYP2C9 alleles and 21 human CYP3A4 alleles, including wild-type CYP2C9.1 and CYP3A4.1, which contain the 24 CYP2C9 novel alleles (*36–*60) and 6 CYP3A4 novel alleles (*28–*34) newly found in the Chinese population, on sildenafil metabolism through in vitro experiment.Methods: The recombinant cytochrome P450 alleles protein of CYP2C9 and CYP3A4 expressed in insect baculovirus expression system were reacted with 10– 500 μM sildenafil for 30 minutes at 37°C, and the reaction was terminated by cooling to − 80°C immediately. Next, we used ultra-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) detection system to detect sildenafil and its active metabolite N-desmethyl sildenafil.Results: The intrinsic clearance (Vmax/Km) values of most CYP2C9 variants were significantly altered when compared with the wild-type CYP2C9*1, with most of these variants exhibiting either reduced Vmax and/or increased Km values. Four alleles (CYP2C9*11, *14, *31, *49) exhibited no markedly decreased relative clearance (1-fold). The relative clearance of the remaining thirty-three variants exhibited decrease in different levels, ranging from 1.81% to 88.42%. For the CYP3A4 metabolic pathway, when compared with the wild-type CYP3A4*1, the relative clearance values of four variants (CYP3A4*3, *10, *14 and *I335T) showed significantly higher relative clearance (130.7– 134.9%), while five variants (CYP3A4*2, *5, *24, *L22V and *F113I) exhibited sharply reduced relative clearance values (1.80– 74.25%), and the remaining nine allelic variants showed no statistical difference. In addition, the kinetic parameters of two CYP3A4 variants (CYP3A4*17 and CYP3A4*30) could not be detected, due to the defect of the CYP3A4 gene.Conclusion: These findings were the first evaluation of all these infrequent CYP2C9 and CYP3A4 alleles for sildenafil metabolism; when treating people who carry these CYP2C9 and CYP3A4 variants, there should be more focus on the relation of dose intensity, side effects and therapeutic efficacy when administering sildenafil. The study will provide fundamental data on effect of CYP2C9 and CYP3A4 allelic variation on sildenafil metabolism for further clinical research.Keywords: allelic variants, CYP2C9 polymorphisms, CYP3A4 polymorphisms, enzymatic activity, sildenafil, individual treatment