An iminium ion metabolite hampers the production of the pharmacologically active metabolite of a multikinase inhibitor KW‐2449 in primates: irreversible inhibition of aldehyde oxidase and covalent binding with endogenous proteins

Abstract

We previously reported that KW-2449, (E)-1-{4-[2-(1H-Indazol-3-yl)vinyl]benzoyl}piperazine, a novel multikinase inhibitor developed for the treatment of leukemia patients, was oxidized to an iminium ion intermediate by monoamine oxidase B (MAO-B) and then converted to its oxo-piperazine form (M1) by aldehyde oxidase (AO). However, it was found that the significant decrease in the pharmacologically active metabolite M1 following repeated administration of KW-2449 in primates might hamper the effectiveness of the drug. The mechanism underlying this phenomenon was investigated and it was found that the AO activity was inhibited in a time-dependent manner in vitro under the co-incubation of KW-2449 and MAO-B, while neither KW-2449 nor M1 strongly inhibited MAO-B or AO activity. These results clearly suggest that MAO-B catalysed iminium ion metabolite inhibited AO, prompting us to investigate whether or not the iminium ion metabolite covalently binds to endogenous proteins, as has been reported with other reactive metabolites as a cause for idiosyncratic toxicity. The association of the radioactivity derived from C-KW-2449 with endogenous proteins both in vivo and in vitro was confirmed and it was verified that this covalent binding was inhibited by the addition of sodium cyanide, an iminium ion-trapping reagent, and pargyline, a MAO-B inhibitor. These findings strongly suggest that the iminium ion metabolite of KW-2449 is highly reactive in inhibiting AO irreversibly and binding to endogenous macromolecules covalently.

Metabolism by Aldehyde Oxidase: Drug Design and Complementary Approaches to Challenges in Drug Discovery

“…The piperazine ring of KW-2449, a multikinase inhibitor developed for treatment of leukemia, was oxidized to iminium ion by MAO-B and then by AO to the pharmacodynamically active piperazinone metabolite (Figure A) . The iminium ion intermediate of KW-2449 was also an irreversible inhibitor of AO, possibly through covalent binding to the enzyme . A similar metabolic pathway was observed for 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), a dopaminergic pro-neurotoxin which induces parkinsonism in humans and other primates (Figure B). , The morpholine ring of momelotinib, an inhibitor of Janus kinase 1/2 and activin A receptor type 1, was first oxidized by CYPs to iminium ion and then by AO to the corresponding morpholin-3-one metabolite (Figure C) .…”

Roles of selected non-P450 human oxidoreductase enzymes in protective and toxic effects of chemicals: review and compilation of reactions

“…KW-2449 is a multikinase inhibitor that was previously under investigation for the treatment of leukemia. The drug, which has been discontinued from further development, displayed unexpected rapid metabolism to an oxo-piperazine metabolite in clinical trials (Hosogi et al 2018 ). The pharmacologically active metabolite was determined to be generated via sequential metabolism by MAO B to an iminium ion intermediate, followed by AOX-mediated oxidation to the oxo-piperazine metabolite (Table 15 , Fig.…”

Cyanide Trapping of Iminium Ion Reactive Metabolites: Implications for Clinical Hepatotoxicity

“…33,76 A mechanism for the time-dependent inhibition (TDI) of CYP1A2 by proprietary compound DSP-1053 and the irreversible inhibition of AO by proprietary compound KW-2449 have both been attributed to iminium ion intermediates. 66,77,78 Rimonabant has been reported to be metabolized by CYP3A4 to form a highly cytotoxic reactive iminium ion metabolite that covalently binds to cellular proteins. 48,49 Recently, Tang et al reported the iminium ion intermediates formed from pemigatinib caused mechanism-based inactivation of P450 CYP3A.…”