title: Identification of the in vitro metabolites of 3,4-dihydro-2,2-dimethyl-2H-naphthol[1,2-b]pyran-5,6-dione (ARQ 501; beta-lapachone) in whole blood.
abstract: 3,4-Dihydro-2,2-dimethyl-2H-naphthol[1,2-b]pyran-5,6-dione (ARQ 501; beta-lapachone) showed promising anticancer activity in phase I clinical trials as monotherapy and in combination with cytotoxic drugs. ARQ 501 is currently in multiple phase II clinical trials. In vitro incubation in fresh whole blood at 37 degrees C revealed that ARQ 501 is stable in plasma but disappears rapidly in whole blood. Our data showed that extensive metabolism in red blood cells (RBCs) was mainly responsible for the rapid disappearance of ARQ 501 in whole blood. By comparison, covalent binding of ARQ 501 and/or its metabolites to whole blood components was a minor contributor to the disappearance of this compound. Sequestration of intact ARQ 501 in RBCs was not observed. Cross-species metabolite profiles from incubating [(14)C]ARQ 501 in freshly drawn blood were characterized using a liquid chromatography-mass spec-trometry-accurate radioactivity counter. The results show that ARQ 501 was metabolized more rapidly in mouse and rat blood than in dog, monkey, and human blood, with qualitatively similar metabolite profiles. Six metabolites were identified in human blood using ultra-high performance liquid chromatography/time-of-flight mass spectrometry, and the postulated structure of five metabolites was confirmed using synthetic standards. We conclude that the primary metabolic pathway of ARQ 501 in human blood involved oxidation of the two adjacent carbonyl groups to produce dicarboxylic and monocarboxylic metabolites, elimination of a carbonyl group to form a ring-contracted metabolite, and lactonization to produce two metabolites with a pyrone ring to form a ring-contracted metabolite. Metabolism by RBCs may play a role in clearance of ARQ 501 from the blood compartment in cancer patients.
authors.affiliation: Department of Preclinical Development and Clinical Pharmacology, ArQule, Inc., Woburn, Massachusetts 01801, USA.
authors.forename: Xiu-Sheng
authors.initials: XS
authors.lastname: Miao
authors.forename: Pengfei
authors.initials: P
authors.lastname: Song
authors.forename: Ronald E
authors.initials: RE
authors.lastname: Savage
authors.forename: Caiyun
authors.initials: C
authors.lastname: Zhong
authors.forename: Rui-Yang
authors.initials: RY
authors.lastname: Yang
authors.forename: Darin
authors.initials: D
authors.lastname: Kizer
authors.forename: Hui
authors.initials: H
authors.lastname: Wu
authors.forename: Erika
authors.initials: E
authors.lastname: Volckova
authors.forename: Mark A
authors.initials: MA
authors.lastname: Ashwell
authors.forename: Jeffrey G
authors.initials: JG
authors.lastname: Supko
authors.forename: Xiaoying
authors.initials: X
authors.lastname: He
authors.forename: Thomas C K
authors.initials: TC
authors.lastname: Chan
mesh_terms: D000818:Animals; D004285:Dogs; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods; D000882:Haplorhini; D006801:Humans; D051379:Mice; D009285:Naphthoquinones / Q000097:blood* / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D051381:Rats; D013045:Species Specificity
chemical_list: D009285:Naphthoquinones; C014638:beta-lapachone