Characterization of the steady state concentrations and pharmacogenetics of ritonavir boosted atazanavir in Kenyan HIV positive patients.
Abstract
Background
Atazanavir is a protease inhibitor currently recommended for use as a second
line agent in Human Immunodeficiency Virus (HIV) infected patients who have
failed therapy on a first line regimen. The pharmacokinetics of atazanavir are
highly variable and may be influenced by factors such as age, sex, weight and
genetics. In Kenya, there is a paucity of local HIV patient data on atazanavir
pharmacokinetics, the influence of cytochrome P450 subfamily 3A5 (CYP3A5)
genetic polymorphisms on its disposition and the prevalence of
hyperbilirubinemia in patients using the drug.
Objectives
We optimized and verified a high-performance liquid chromatographic method
with ultra-violet detection (HPLC-UV) for the determination of plasma
concentrations of atazanavir. We determined the prevalence of single nucleotide
polymorphisms in CYP3A5 and uridine diphosphate glucuronosyltransferase 1
family, polypeptide A1 (UGT1A1) enzymes. Thereafter, we examined whether
polymorphisms in CYP3A5 enzymes were associated with atazanavir steadystate plasma concentrations. We determined the prevalence and risk factors of
hyperbilirubinemia and investigated the effect of UGT1A1 polymorphisms on
bilirubin levels and the risk of hyperbilirubinemia.
Methods
We conducted a cross sectional study enrolling 110 male and female HIV positive
patients on ritonavir boosted atazanavir over two months from the Kenyatta
National Hospital. Participants were 18 years and older and provided written
informed consent. We abstracted data from patient files, conducted interviews
and drew five blood samples: one at 30 minutes before the morning dose then 2
and 4 hours after the morning dose. The two additional samples were for
genotyping and for determination of plasma bilirubin levels respectively.
Atazanavir quantification was achieved by high performance liquid
chromatography with ultraviolet detection at 261nm. Genetic analysis was
performed by fast real time polymerase chain reaction for CYP3A5 and UGT1A1
single nucleotide polymorphisms.
Statistical analysis was done in STATA version 13.1 and R i3.8.6 version 3.3.1
with the level of significance set at p value ≤ 0.05. Ethical approval was granted
by the Kenyatta National Hospital and University of Nairobi Ethics and Research
Review Committee (KNH-ERC/A/110).
Results
Optimization and verification of a HPLC-UV method for the quantification of
plasma atazanavir levels was achieved. The coefficient of determination was >
0.99 and was linear between 100 -10000 ng/mL. The precision (% relative
standard deviation) was 8,8% (SD 6.2) and the accuracy ranged from 91.3 -
120.8%. The limit of detection was 40 ng/mL whereas the limit of quantitation
was 120ng/mL.
The prevalence of single nucleotide polymorphisms was as follows: CYP3A5*3 TT
wild type genotype - 24%, heterozygous TC genotype - 70%, CC homozygous
genotype -6%; CYP3A5*6 CC wild type genotype - 2.7%, heterozygous CT
genotype - 97.3%; CYP3A5*7 AA wild type genotype – 1.8%, heterozygous A/-
genotype – 95.5%, -/- variant genotype - 2.7%; UGT1A1 CC genotype 16.4%,
heterozygous CT 83.6%.
A small proportion of participants had subtherapeutic plasma trough
concentrations of atazanavir (13%) whereas 39% had supratherapeutic levels.
CYP3A5*6 was found to influence the trough plasma concentrations of
atazanavir (adjusted estimate 2151.1 ng/mL, 95% CI 275.5, 4026.8). The
prevalence of grades III and IV hyperbilirubinemia among the participants was
12.7 and 1.8%. Hyperbilirubinemia of any grade was present in 57.3% of the
participants
Risk factors for hyperbilirubinemia were high atazanavir trough concentrations
(aOR 1.001, 95% CI 1.001, 1.002), UGT1A1 heterozygosity (aOR 7.01, 95% CI
1.86, 34.01) and a positive history of alcohol use (aOR 0.18, 95% CI 0.03, 0.78).
Conclusions
CYP3A5 and UGT1A1 polymorphisms exist in this population. A significant
proportion of participants had supratherapeutic trough plasma concentrations
of atazanavir. CYP3A5 polymorphisms have an influence on the troughxvii
concentrations of atazanavir. Hyperbilirubinemia is prevalent in patients on
atazanavir and is influenced by UGT1A1 status, trough plasma concentrations
of atazanavir pharmacokinetics and alcohol use.
Publisher
University of Nairobi
Rights
Attribution-NonCommercial-NoDerivs 3.0 United StatesUsage Rights
http://creativecommons.org/licenses/by-nc-nd/3.0/us/Collections
The following license files are associated with this item: