No Effect of PXR (8055C>T) Polymorphism on the Pharmacokinetic Profiles of Piperaquine in Healthy Chinese Subjects.

Background: Significant inter-subject variability in pharmacokinetics and clinical outcomes has been observed for the antimalarial agent piperaquine (PQ). PQ is metabolized by CYP3A4, mainly regulated by the pregnane X receptor (PXR). CYP3A4(*1B) polymorphism did not affect PQ clearance.

Objectives: The effect of PXR (8055C>T) polymorphism on the pharmacokinetic profiles of PQ was investigated.

Methods: The pharmacokinetic profiles of PQ and its major metabolite PQ N-oxide (PQM) were studied in healthy Chinese subjects after recommended oral doses of artemisinin-PQ. Twelve subjects were genotyped using PCRRFLP (six in each group with PXR 8055CC and 8055TT), and plasma concentrations were determined by a validated LC/MS/MS method. The dose-adjusted exposure (AUC and C) to PQ or PQM was investigated, and the metabolic capability of PQ N-oxidation was determined by AUC/AUC. The antimalarial outcome of PQ was evaluated using its day 7 concentration.

Results: PQM formation was mediated by CYP3A4/3A5. Interindividual variability in dose-adjusted AUC of PQ and PQM was relatively low (%CV, <30.0%), whereas a larger inter-variability was observed for C values (%CV, 68.1% for PQ). No polymorphic effect was found for PXR (C8055T) on the pharmacokinetic profiles of PQ or its Cday 7 concentrations.

Conclusion: Both CYP3A4 and CYP3A5 were involved in PQ clearance. The genotypes of PXR (C8055T) may not contribute to the variability in PQ pharmacokinetics as well as antimalarial outcomes. There might be a low risk of variable exposures to PQ in malaria patients carrying mutated PXR (8055C>T) genes, which deserves further study, especially in a larger sample size.