Quantitation of five nevirapine oxidative metabolites in human plasma using liquid chromatography–tandem mass spectrometry

Sulfation of 12-hydroxy-nevirapine by human SULTs and the effects of genetic polymorphisms of SULT1A1 and SULT2A1

Nevirapine (NVP) is an effective drug for the treatment of HIV infections, but its use is limited by a high incidence of severe skin rash and liver injury. 12-Hydroxynevirapine (12-OH-NVP) is the major metabolite of nevirapine. There is strong evidence that the sulfate of 12-OH-NVP is responsible for the skin rash. While several cytosolic sulfotransferases (SULTs) have been shown to be capable of sulfating 12-OH-NVP, the exact mechanism of sulfation in vivo is unclear. The current study aimed to clarify human SULT(s) and human organs that are capable of sulfating 12-OH-NVP and investigate the metabolic sulfation of 12-OH-NVP using cultured HepG2 human hepatoma cells. Enzymatic assays revealed that of the thirteen human SULTs, SULT1A1 and SULT2A1 displayed strong 12-OH-NVP-sulfating activity. 1-Phenyl-1-hexanol (PHHX), which applied topically prevents the skin rash in rats, inhibited 12-OH-NVP sulfation by SULT1A1 and SULT2A1, implying the involvement of these two enzymes in the sulfation of 12-OH-NVP in vivo. Among five human organ cytosols analyzed, liver cytosol displayed the strongest 12-OH-NVP-sulfating activity, while a low but significant activity was detected with skin cytosol. Cultured HepG2 cells were shown to be capable of sulfating 12-OH-NVP. The effects of genetic polymorphisms of SULT1A1 and SULT2A1 genes on the sulfation of 12-OH-NVP by SULT1A1 and SULT2A1 allozymes were investigated. Two SULT1A1 allozymes, Arg37Asp and Met223Val, showed no detectable 12-OH-NVP-sulfating activity, while a SULT2A1 allozyme, Met57Thr, displayed significantly higher 12-OH-NVP-sulfating activity compared with the wild-type enzyme. Collectively, these results contribute to a better understanding of the involvement of sulfation in NVP-induced skin rash and provide clues to the possible role of SULT genetic polymorphisms in the risk of this adverse reaction.

LC-MS/MS Quantification of Nevirapine and Its Metabolites in Hair for Assessing Long-Term Adherence

The adherence assessment based on the combination of nevirapine (NVP) and its two metabolites (2-hydroxynevirapine and 3-hydroxynevirapine) would more comprehensively and accurately reflect long-term adherence than that of a single prototype. This study aimed to develop a specific, sensitive and selective method for simultaneous detection of the three compounds in hair and explore whether there was consistency among the three compounds in assessing long-term adherence. Furthermore, 75 HIV-positive patients who were taking the NVP drug were randomly recruited and divided into two groups (high-and low-adherence group). All participants self-reported their days of oral drug administration per month and provided their hair strands closest to the scalp at the region of posterior vertex. The concentrations of three compounds in the hair were determined using a developed LC-MS/MS method in multiple reaction monitoring. This method showed good performances in limit of quantification and accuracy with the recoveries from 85 to 115% and in precision with the intra-day and inter-day coefficients of variation within 15% for the three compounds. The population analysis revealed that patients with high-adherence showed significantly higher concentrations than those with low-adherence for all three compounds. There were significantly moderate correlations of nevirapine with 2-hydroxynevirapine and 3-hydroxynevirapin and high correlation between 2-hydroxynevirapine and 3-hydroxynevirapin. The two NVP’s metabolites showed high consistency with NVP in evaluating long-term adherence.

Pharmacokinetic analysis of nevirapine extended release 400 mg once daily vs nevirapine immediate release 200 mg twice daily formulation in treatment-naïve patients with HIV-1 infection

BACKGROUND

VERxVE data showed non-inferior virologic efficacy with extended release nevirapine (NVP-XR) dosed 400 mg once daily (QD) versus immediate release nevirapine (NVP-IR) 200 mg twice daily in a double-blind, non-inferiority study in treatment-naïve HIV-1-positive patients.

OBJECTIVE

To study the pharmacokinetics (PK) of the NVP formulations and identify possible associations with demographic factors.

METHODS

Patients with viral load ≥1000 copies/mL and CD4+ count > 50- <400 cells/mm³ (males) and >50- <250 cells/mm³ (females) at screening received NVP-IR 200 mg QD during a 14-day lead-in and were then stratified by baseline viral load and randomized to NVP-XR or -IR. NVP trough concentrations at steady state (SS) (C_pre,ss,N) were measured up to week 48 for all participating patients. In a PK sub-study, SS parameters - AUC_0-24, C_max, C_min, and peak-to-trough fluctuation were obtained and analyzed with relative bioavailability assessed at week 4 by plasma collection over 24 h.

RESULTS

Trough concentrations were stable from week 4 to week 48 for all patients (n = 1011) with both formulations, with NVP-XR/IR ratios of 0.77-0.82. Overall, 49 patients completed the PK sub-study: 24 XR and 25 IR. NVP-XR showed less peak-to-trough fluctuation (34.5%) than IR (55.2%), and lower AUC_0-24, C_min, C_max, and trough concentrations than IR. However, no effect of SS trough concentrations was found on the virologic response proportion at least up to 1000 ng/mL. No significant association was found between NVP PK and gender, race, and viral load.

CONCLUSION

These data suggest NVP-XR achieves lower but effective NVP exposure compared with NVP-IR.

Quinoid derivatives of the nevirapine metabolites 2-hydroxy- and 3-hydroxy-nevirapine: activation pathway to amino acid adducts

Quinoid electrophiles from the nevirapine metabolites, 2-OH- and 3-OH-nevirapine, react with nitrogen-based bionucleophiles yielding covalent adducts.

Steady-state pharmacokinetics of nevirapine extended-release tablets in HIV-1-infected children and adolescents: an open-label, multiple-dose, cross-over study

BACKGROUND

To compare steady-state (ss) pharmacokinetic targets of nevirapine extended-release (NVP-XR) tablets once-daily (QD) with immediate-release (NVP-IR) tablet or oral suspension twice-daily in HIV-1-infected children and adolescents.

METHODS

Phase I, open-label, multidose, cross-over study with optional extension phase, in 85 patients 3 to <18 years of age, previously on an NVP-IR-based regimen for ≥18 weeks with baseline viral load <50 copies/mL. Patients were stratified by age, treated with NVP-IR twice-daily for 11 days, then NVP-XR QD for 10 days. Cpre,ss (steady-state, predose concentrations) was obtained from all, and 12-hour NVP-IR and 24-hour NVP-XR steady-state pharmacokinetic profiles were obtained in the pharmacokinetic substudy. Viral loads, CD4 counts and adverse events (AEs) were monitored.

RESULTS

Eighty patients completed the trial. Adjusted geometric mean (gMean) Cpre,ss for NVP-XR and NVP-IR exceeded the target of 3000 ng/mL, and the adjusted gMean NVP-XR:NVP-IR ratio (90% confidence interval) for QD normalized and un-normalized Cpre,ss were 91.2% (83.5-99.6%) and 91.8% (83.7-100.7%). gMean 24-hour area under the curve at steady-state NVP-XR:NVP-IR for un-normalized dose was 90.4% and un-normalized Cpre,ss NVP-XR:NVP-IR were 91.0%, 81.9% and 103.7% for the 3 age groups, 3 to <6, 6 to <12 and 12 to <18 years, respectively. gMean values indicated no exposure to subtherapeutic NVP concentrations and viral suppression was adequate and maintained in all QD groups. Most AEs were mild and similar between age groups. No serious or Division of AIDS Grade 4 AEs or AE related treatment discontinuations occurred.

CONCLUSIONS

NVP-XR exhibited adequate trough concentrations with equivalent area under the curve at steady-state relative to NVP-IR. NVP-XR was well-tolerated and is a valuable treatment option for HIV-infected children and adolescents.

A sensitive and specific liquid chromatography/tandem mass spectrometry method for quantification of nevirapine and its five metabolites and their pharmacokinetics in baboons

A highly sensitive and specific LC-MS/MS assay was developed and validated to quantify nevirapine (NVP) and its five metabolites [2-, 3-, 8-, 12-hydroxyl NVP (OHNVP) and 4-carboxyl NVP (CANVP)] simultaneously in baboon serum and the assay was used to characterize their pharmacokinetic studies of an oral-dose escalation study in baboon. The lower limit of quantification (LLOQ) for NVP and its four hydroxyl nevirapine metabolites was 1.0 ng/mL and for 4-CANVP was 5.0 ng/mL. The between-run and within-run precisions and accuracies at four quality control concentrations (1, 5, 50 and 500 ng/mL) were evaluated in baboon serum with less than 14% variation and 93-114% accuracies (n = 6), except for the LLOQ for 2-OHNVP, which had an accuracy of 115.8% for between-run validation. The pharmacokinetics of NVP and its five metabolites in non-pregnant baboons by a single-dose escalation study were also profiled. The major metabolites detected were 4-CANVP and 12-OHNVP. 3-OHNVP and 2-OHNVP were the minor metabolites with only a trace amount of 2-OHNVP detected in some pharmacokinetic samples. No 8-OHNVP was observed in all of the pharmacokinetic samples. In addition, the fragmentation for the four hydroxyl metabolite isomers is also discussed.

In vitro-in vivo correlation for nevirapine extended release tablets

An in vitro-in vivo correlation (IVIVC) for four nevirapine extended release tablets with varying polymer contents was developed. The pharmacokinetics of extended release formulations were assessed in a parallel group study with healthy volunteers and compared with corresponding in vitro dissolution data obtained using a USP apparatus type 1. In vitro samples were analysed using HPLC with UV detection and in vivo samples were analysed using a HPLC-MS/MS assay; the IVIVC analyses comparing the two results were performed using WinNonlin. A Double Weibull model optimally fits the in vitro data. A unit impulse response (UIR) was assessed using the fastest ER formulation as a reference. The deconvolution of the in vivo concentration time data was performed using the UIR to estimate an in vivo drug release profile. A linear model with a time-scaling factor clarified the relationship between in vitro and in vivo data. The predictability of the final model was consistent based on internal validation. Average percent prediction errors for pharmacokinetic parameters were <10% and individual values for all formulations were <15%. Therefore, a Level A IVIVC was developed and validated for nevirapine extended release formulations providing robust predictions of in vivo profiles based on in vitro dissolution profiles.

Pharmacokinetic assessment of nevirapine and metabolites in human immunodeficiency virus type 1-infected patients with hepatic fibrosis

Nevirapine is a nonnucleoside reverse transcriptase inhibitor used as part of combination therapy for human immunodeficiency virus (HIV) infection. Nevirapine may be prescribed for patients with hepatic fibrosis and cirrhosis. Significant autoinduction of cytochrome P450 3A4 and 2B6 following multiple dosing prompted an assessment of the metabolic profiles in patients with liver disease receiving chronic nevirapine therapy. HIV-infected patients with hepatic fibrosis who were receiving a stable antiretroviral regimen containing nevirapine for > or = 6 weeks had liver biopsy specimens assessed by Ishak histologic scoring and were grouped by severity (group 1, Ishak scores of 1 and 2; group 2, Ishak scores of 3 and 4; group 3, Ishak scores of 5 and 6). Steady-state trough nevirapine levels were determined for all patients, and additional measurements were obtained at 1, 2, and 4 h following nevirapine dosing for a subset of patients. The pharmacokinetics of nevirapine and its five metabolites were characterized, and a comparison of the results for the different Ishak groups was performed. Among 51 patients with hepatic fibrosis, the majority of whom were coinfected with hepatitis C virus or hepatitis B virus, differences between the maximum and the minimum observed plasma concentrations demonstrated a statistically significant flattening of the systemic exposure curves with progression from Ishak group 1 to Ishak group 2 or 3, suggesting a decrease in systemic clearance with the progression of liver disease. However, there were no significant differences in the trough and the maximum nevirapine concentrations between the Ishak groups. The metabolite profiles were also comparable across the Ishak groups. In HIV-infected patients who were chronically treated with nevirapine and who had various degrees of hepatic fibrosis, including cirrhosis, trough plasma nevirapine concentrations were not significantly increased, and thus, no dose adjustment is warranted.