Titre du document / Document title

CYP2C8 and CYP3A4 are the principal enzymes involved in the human in vitro biotransformation of the insulin secretagogue repaglinide

Auteur(s) / Author(s)

BIDSTRUP Tanja Busk ⁽¹⁾ ; BJØRNSDOTTIR Inga ⁽²⁾ ; SIDELMANN Ulla Grove ⁽²⁾ ; THOMSEN Mikael Søndergard ⁽³⁾ ; HANSEN Kristian Tage ⁽²⁾ ;

Affiliation(s) du ou des auteurs / Author(s) Affiliation(s)

⁽¹⁾ Clinical Pharmacology, Univeristy of Southern Denmark, Winslowparken 19, 5000 Odense, DANEMARK
⁽²⁾ Drug Metabolism, Novo Nordisk A/S, DANEMARK
⁽³⁾ Clinical Pharmacology, Novo Nordisk A/S, DANEMARK

Résumé / Abstract

Aims To identity the principal human cytochrome P450 (CYP) enzyme(s) responsible for the human in vitro biotransformation of repaglinide. Previous experiments have identified CYP3A4 as being mainly responsible for the in vitro metabolism of repaglinide but the results of clinical investigations have suggested that more than one enzyme may be involved in repaglinide biotransformation. Methods [1⁴C]-Repaglinide was incubated with recombinant CYP and with human liver microsomes (HLM) from individual donors in the presence of inhibitory antibodies specific for individual CYP enzymes. Metabolites, measured by high-performance liquid chromatography (HPLC) with on-line radiochemical detection, were identified by liquid chromatography-mass spectrophotometry (LC-MS) and LC-MS coupled on-line to a nuclear magnetic resonance spectrometer (LC-MS-NMR), Results CYP3A4 and CYP2C8 were found to be responsible for the conversion of repaglinide into its two primary metabolites, M4 (resulting from hydroxylation on the piperidine ring system) and Ml (an aromatic amine) Specific inhibitory monoclonal antibodies against CYP3A4 and CYP2C8 significantly inhibited (> 71%) formation of M4 and Ml in HLM. In a panel of HLM from 12 individual donors formation of M4 and Ml varied from approximately 160-880 pmol min^-1 mg^-1 protein and from 100-1110 pmol min^-1 mg^-1 protein, respectively. The major metabolite generated by CYP2C8 was found to be M4. The rate of formation of this metabolite in HLM correlated significantly with paclitaxel 6α-hydroxylation (r = 0.80; P = 0.0029). Two other minor metabolites were also detected. One of them was Ml and the other was repaglinide hydroxylated on the isopropyl moiety (M0-OH). The rate of formation of M4 in CYP2C8 Supersomes was 2.5 pmol min^-1 pmol^-1 CYP enzyme and only. about 0.1 pmol min^-1 pmol^-1 CYP enzyme in CYP3A4 Supersomes The major metabolite generated by CYP3A4 was M1. The rate of formation of this metabolite in HLM correlated significantly with testosterone 6β-hydroxylation (r_s = 0.90; P = 0.0002). Three other metabolites were identified, namely, M0-OH, M2 (a dicarboxylic acid formed by oxidative opening of the piperidine ring) and M5. The rate of M1 formation in CYP3A4 supersomes was 1.6 pmol min^-1 pmol^-1 CYP enzyme but in CYP2C8 Supersomes it was only approximately 0.4 pmol min^-1 pmol^-1 CYP enzyme. Conclusions The results confirm an important role for both CYP3A4 and CYP2C8 in the human in vitro biotransformation of repaglinide. This dual CYP biotransformation may have consequences for the clinical pharmacokinetics and drug-drug interactions involving repaglinide if one CYP pathway has sufficient capacity to compensate if the other is inhibited.

Revue / Journal Title

British journal of clinical pharmacology   ISSN 0306-5251   CODEN BCPHBM 

Source / Source

2003, vol. 56, n^o3, pp. 305-314 [10 page(s) (article)] (28 ref.)

Langue / Language

Anglais

Editeur / Publisher

Blackwell Science, London, ROYAUME-UNI  (1974) (Revue)

Mots-clés anglais / English Keywords

Digestive system ; Hypoglycemic agent ; In vitro ; Human ; Liver ; Microsome ; Isozyme ; Cytochrome P450 ; Metabolism ; Repaglinide ;

Mots-clés français / French Keywords

Appareil digestif ; Hypoglycémiant ; Cytochrome CYP2C8 ; Cytochrome CYP3A4 ; In vitro ; Homme ; Foie ; Microsome ; Isozyme ; Cytochrome P450 ; Métabolisme ; Répaglinide ;

Mots-clés espagnols / Spanish Keywords

Aparato digestivo ; Hipoglicemiante ; In vitro ; Hombre ; Hígado ; Microsoma ; Isozima ; Citocromo P450 ; Metabolismo ; Repaglinida ;

Mots-clés d'auteur / Author Keywords

CYP2C8 ; CYP3A4 ; cytochrome P450 inhibition ; human liver microsomes ; repaglinide ;

Localisation / Location

INIST-CNRS, Cote INIST : 16791, 35400011432821.0080