Evidence for nevirapine bioactivation in man: Searching for the first step in the mechanism of nevirapine toxicity

Abstract

a b s t r a c tDespite its efficacy, including in the prevention of vertical transmission, the antiretroviral nevirapine is associated with severe idiosyncratic hepatotoxicity and skin rash. The mechanisms underlying nevirapine toxicity are not fully understood, but drug bioactivation to reactive metabolites capable of forming stable protein adducts is thought to be involved. This hypothesis is based on the paradigm that drug reactive metabolites have the potential to bind to self-proteins, which results in drug-modified proteins being perceived as foreign by the immune system. The aim of the present work was to identify hemoglobin adducts in HIV patients as biomarkers of nevirapine haptenation upon bioactivation. The ultimate goal is to develop diagnostic methods for predicting the onset of nevirapine-induced toxic reactions.All included subjects were adults on nevirapine-containing antiretroviral therapy for at least 1 month. The protocol received prior approval from the Hospital Ethics Committees and patients gave their written informed consent. Nevirapine-derived adducts with the N-terminal valine of hemoglobin were analyzed by an established liquid chromatography-electrospray ionization-tandem mass spectrometry method and characterized on the basis of retention time and mass spectrometric fragmentation pattern by comparison with adduct standards prepared synthetically. The nevirapine adducts were detected in 12/13 patient samples, and quantified in 11/12 samples (2.58 ± 0.8 fmol/g of hemoglobin).This work represents the first evidence of nevirapine-protein adduct formation in man and confirms the ability of nevirapine to modify self-proteins, thus providing clues to the molecular mechanisms underlying nevirapine toxicity. Moreover, the possibility of assessing nevirapine-protein adduct levels has the potential to become useful for predicting the onset of nevirapine-induced adverse reactions.© 2012 Published by Elsevier Ireland Ltd.Abbreviations: cART, combined antiretroviral therapy; CID, collision-induced dissociation; GSH, glutathione; Hb, hemoglobin; HIV, human immunodeficiency virus; HLA, human leukocyte antigen; 12-OH-NVP, 12-hydroxy-nevirapine; LC-ESI-MS/MS, liquid chromatography-electrospray ionization-tandem mass spectrometry; MHC, major histocompatibility complex; NNRTI, non-nucleoside reverse transcriptase inhibitor; NVP, nevirapine.* Corresponding author.

Nevirapine Inhibits the Anti-HIV Activity of CD8+ Cells

“…NVP can cause liver damage, skin reactions, and allergic reactions 21–23 . In some cases, hepatic injury progresses despite discontinuation of treatment.…”

HLA and Delayed Drug-Induced Hypersensitivity

“…Nevirapine DDAR appears to be mediated both by CD8+ and CD4+ T cells (which can explain its association with both MHC class I and II molecules) [22,66], and adverse reactions are more common and more severe in immunologically uncompromised patients undergoing HIV postexposure prophylaxis [67]. The risk of severe allergy is higher among patients with a CD4+ count >250 cells/μl (for females) or >400 cells/μl (for males).…”

“…Concerning the immunopathogenesis of nevirapine DDAR, 12-OH-NVP and other reactive metabolites formed during biotransformation phase I reactions act as haptens, which, unlike nevirapine, are able to bind a carrier protein and, therefore, trigger an immune response [67]. Although the specific mechanism of drug-HLA interaction largely remains to be discovered, it is known that 12-OH-NVP formation is influenced by the patient's genotype [63].…”

The importance of hapten–protein complex formation in the development of drug allergy

“…Isolation of HSA from serum samples of HIV-1 patients undergoing nevirapine therapy showed modification of a single-histidine residue (His146), the same residue identified by the in-vitro analysis [35 && ]. The N-terminal valine in haemoglobin was also modified in red blood cells from nevirapinetreated patients [36]. It should now be possible to investigate whether these hapten-protein complexes can act as T cell antigens in patients with nevirapine hypersensitivity syndrome.…”