Background: Cytochrome P450 2B6 (CYP2B6)-G516T genotype is associated with altered activity of hepatic CYP2B6 and efavirenz pharmacokinetics, but the relationship between the CYP2B6-G516T genotype and nevirapine (NVP) pharmacokinetics in plasma and cerebrospinal fluid (CSF) is limited.
Methods: In 126 children who received NVP and protease inhibitors from PACTG 366 and 377 cohorts, CYP2B6 and ATP-binding cassette, sub-family B, member 1 (ABCB1) gene polymorphisms were analyzed using real-time PCR. Plasma NVP pharmacokinetics and clinical data were collected and levels of NVP in CSF were evaluated in children with HIV-related neurologic diseases.
Results: NVP oral clearance in children with the CYP2B6-516-T/T genotype (homozygous variant, n = 14) was 1.6 l/h per m2, which was significantly decreased compared to 2.3 l/h per m2 in those with the -G/G (wild type, n = 49, P = 0.002) and 2.1 l/h per m2 in those with the -G/T genotype (heterozygous variants, n = 63, P = 0.008). Furthermore, children with the -T/T genotype had a significant increase in CD4+ T-cell percentage (+9.0%) compared with those with the -G/G (+3.2%, P = 0.01) and -G/T genotype (+5.0%, P = 0.04) from baseline to week 12. The same trend continued at week 24. Although ABCB1-C3435T genotypes did not affect plasma NVP pharmacokinetics (P = 0.39), the NVP CSF: plasma ratios were significantly higher in children with the ABCB1-3435-C/T or -T/T genotypes (0.62, n = 9) in comparison with those with the ABCB1-3435-C/C genotype (0.43, n = 5) (P = 0.01).
Conclusions: The CYP2B6-G516T genotype alters NVP pharmacokinetics and the immunologic response to NVP-containing HAART regimens in children. These data suggest that the CYP2B6-G516T is an important genetic variant that alters the pharmacokinetics and response to HAART regimens containing NVP.