Atazanavir pharmacokinetics in genetically determined CYP3A5 expressors versus non-expressors.
OBJECTIVE
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 enrollment 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 C(min) 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 C(min) (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 C(min) 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.
Anderson
Peter L
PL
Department of Pharmaceutical Sciences, University of Colorado-Denver, Aurora, CO 80045, USA. Peter.anderson@ucdenver.edu
Aquilante
Christina L
CL
Gardner
Edward M
EM
Predhomme
Julie
J
McDaneld
Patrick
P
Bushman
Lane R
LR
Zheng
Jia-Hua
JH
Ray
Michelle
M
MaWhinney
Samantha
S
D000328:Adult; D019380:Anti-HIV Agents / Q000008:administration & dosage / Q000493:pharmacokinetics*; D000069446:Atazanavir Sulfate; D051544:Cytochrome P-450 CYP3A / Q000096:biosynthesis* / Q000235:genetics*; D005260:Female; D015870:Gene Expression; D006239:Haplotypes; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000008:administration & dosage / Q000493:pharmacokinetics*; D010949:Plasma / Q000737:chemistry; D011110:Polymorphism, Genetic; D011725:Pyridines / Q000008:administration & dosage / Q000493:pharmacokinetics*; D019438:Ritonavir / Q000493:pharmacokinetics; D017422:Sequence Analysis, DNA; D055815:Young Adult
D019380:Anti-HIV Agents; D009842:Oligopeptides; D011725:Pyridines; D000069446:Atazanavir Sulfate; C510164:CYP3A5 protein, human; D051544:Cytochrome P-450 CYP3A; D019438:Ritonavir