Biochemical Pharmacology, Vol. 41, No. 2, pp. 255-262, 1991. Printed in Great Britain. omx-2952/91 $3.00 + 0.00 @ 1990. Pergamon Press plc zyxwvu INTERSPECIES VARIABILITY IN MITOXANTRONE METABOLISM USING PRIMARY CULTURES OF HEPATOCYTES ISOLATED FROM RAT, RABBIT AND HUMANS zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPO BRUNO RICHARD,* GERARD FABRE,t GEORGES DE SOUSA, ISABELLE FABRE,$ ROGER RAHMANI and JEAN-PAUL CANot§ INSERM U-278, Laboratoire de Toxicocinktique et de Pharmacocinktique, FacultC de Pharmacie, 27, Bd Jean Moulin, 13385 Marseille Cedex 5; and Institut I. Paoli-J. Calmettes, 232, Bd de Sainte- Marguerite, 13273 Marseille CCdex 9, France (Receioed 21 March 1990; accepted 15 September 1990) Abstract-Metabolism of mitoxantrone was studied in primary cultures of hepatocytes freshly obtained from rat, rabbit and humans. Metabolic pattern was evaluated by a high performance liquid chromatographic method which specifically resolved mitoxantrone from its mono- and dicarboxylic acid derivatives. Studies were carried out over 48 hr and at [‘4C]mitoxantrone concentrations ranging between 1 and 20 PM. In all species studied, metabolism occurred: extracellular unchanged mitoxantrone concentrations represented around 50,25 and 20% of total extracellular radiolabel at 48 hr in rat, rabbit and humans, respectively. Although minor interspecies variability was observed in total amount of drug biotransformed by hepatocytes, large variability in the metabolic pattern occurred between the different species: hence, in rats the main derivatives were two polar compounds and only trace amounts of the mono- and dicarboxylic acid metabolites were present. In both rabbits and humans however, these polar derivatives represented minor metabolic pathways and the main metabolites were the mono- and dicarboxylic acid derivatives. While the percentage of total biotransformation was similar in these two latter species, the monocarboxylic acid derivative was the main metabolite in rabbits while the dicarboxylic acid was predominant in humans. Only small interindividual differences (N = 4) were observed in the metabolism of mitoxantrone by human hepatocytes in primary culture. These data demonstated that: (i) in all species, mitoxantrone was biotransformed into metabolites which rapidly effluxed in the extracellular compartment, (ii) there were low interspecies differences between rat, rabbit and humans in terms of total biotransformed drug, but (iii) large interspecies variability was demonstrated in the qualitative (rat versus both rabbit and human) and relative (rabbit versus man) patterns of the metabolites. Furthermore, the metabolism of mitoxantrone was linear over a wide range of concentrations (i.e. l-20pM). In conclusion, rabbit appears to be the animal species most closely related to humans in terms of mitoxantrone metabolism. Mitoxantrone (NovantroneR, 1,4-dihydroxy-5,8- bis[(2-[(2-hydroxyethyl)-amino]-ethyl)amino]-9,10- anthracenedione dihydrochloride) isanew anticancer drug currently used for the treatment of metastatic breast cancer and acute leukemias [l, 21. It is an anthracenedione drug which can be compared to doxorubicin, but its toxic side-effects, particularly cardiotoxicity, are much less pronounced. Numerous pharmacokinetic studies conducted in phases I and II clinical trials [3-51 have shown that (a) plasma concentration time-curves are adequately described by an open two- or three-compartment model, (b) total distribution volume is very large, (c) urinary elimination is very low, and (d) terminal half-life values show marked interpatient variability and are much longer in case of hepatic impairment11 [3]. Experimental studies undertaken in rat [6-81 and * Present address: Service de MBdecine Interne B, CHRU Caremeau, BP 26, 30006 NEmes Ctdex, France. t Present address: SANOFI Recherche, 371 rue du Pr J. Blavac, 34184 Montwllier Ctdex 4, France. $ Present address: IkSERM U-128, Route de Mende, B.P. 5051. 34033 Montoellier Ctdex. France. B To whom requests ‘for reprints should be addressed. 11 B. Richard, unpublished observation. rabbit [9] demonstrated that the biliary route was the main elimination pathway for mitoxantrone and/ or its metabolites. In agreement with these observations, fecal elimination represents 18.3% of injected dose in man [4] and urinary elimination is very low (5-10%) [3-51. Another study conducted in a single patient showed that biliary elimination was very low (2.7% of injected dose) [3]. However in this patient, hepatic metastases induced a very large decrease in hepatic functions. Althodgh numerous studies were performed to determine the main pathways for drug elimination, only little is known about the importance of its biotransformation. Using the isolated perfused rat liver model, Ehninger et al. [8] demonstrated that mitoxantrone was slowly metabolized and that main observed derivatives were more hydrophilic than the respective mono- and dicarboxylic acid derivatives. HPLC analysis of the urine or bile following mitoxantrone i.v. injection has revealed different metabolic profiles in rat [7], rabbit [9] and man [4,5]. Indeed, using rabbit hepatocytes both in suspension and in primary culture but also bile-duct cannulated rabbit [9], we reported that the main metabolites were the carboxylic acid derivatives. Both quantitative and 255