JAC Advance Access originally published online on August 26, 2009
Journal of Antimicrobial Chemotherapy 2009 64(5):1071-1079; doi:10.1093/jac/dkp317
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Original research |
Atazanavir pharmacokinetics in genetically determined CYP3A5 expressors versus non-expressors
1 Department of Pharmaceutical Sciences, University of Colorado Denver, Aurora, CO 80045, USA 2 Department of Medicine, University of Colorado Denver, Aurora, CO 80045, USA 3 Denver Health, 777 Bannock Street, Denver, CO 80204, USA 4 Department of Biostatistics and Informatics, University of Colorado Denver, Aurora, CO 80045, USA
Received 28 May 2009; returned 2 July 2009; revised 27 July 2009; accepted 3 August 2009
* Corresponding author. Tel: +1-303-724-6128; Fax: +1-303-724-6135; E-mail: Peter.anderson{at}ucdenver.edu
Objectives: The objective of this study was to compare atazanavir pharmacokinetics in genetically determined CYP3A5 expressors versus non-expressors.
Methods: HIV-negative adult volunteers were pre-screened for CYP3A5 *3, *6 and *7 polymorphisms and enrolment was balanced for CYP3A5 expressor status, gender and race (African-American versus non-African-American). Participants received atazanavir 400 mg daily for 7 days followed by atazanavir/ritonavir 300 mg/100 mg daily for 7 days with pharmacokinetic studies on days 7 and 14. Other measures collected were bilirubin, UGT1A1 *28, and ABCB1 1236C > T, 2677G > T/A and 3435C > T genotypes. Data analyses utilized least squares regression.
Results: Fifteen CYP3A5 expressors and 16 non-expressors participated. The day 7 atazanavir oral clearance (CL/F) was 1.39-fold faster (0.25 versus 0.18 L/h/kg; P = 0.045) and the Cmin was half (87 versus 171 ng/mL; P = 0.044) in CYP3A5 expressors versus non-expressors. Non-African-American CYP3A5 expressor males had 2.1-fold faster CL/F (P = 0.003) and <20% the Cmin (P = 0.0001) compared with non-African-American non-expressor males. No overall CYP3A5 expressor effects were observed during the ritonavir phase. One or two copies of wild-type ABCB1 haplotype (1236C/2677G/3435C) was predictive of slower atazanavir and ritonavir CL/F compared with zero copies (P < 0.06). Indirect bilirubin increased 1.6- to 2.8-fold more in subjects with UGT1A1 *28/*28 versus *1/*28 or *1/*1.
Conclusions: CYP3A5 expressors had faster atazanavir CL/F and lower Cmin than non-expressors. The effect was most pronounced in non-African-American men. Ritonavir lessened CYP3A5 expressor effects. The wild-type ABCB1 CGC haplotype was associated with slower CL/F and the UGT1A1 *28 genotype was associated with increased bilirubin. Thus, CYP3A5, ABCB1 and UGT1A1 polymorphisms are associated with atazanavir pharmacokinetics and pharmacodynamics in vivo.
Keywords: antiretroviral therapy , pharmacogenomics , drug metabolism , clinical pharmacology