Identification of the in Vitro Metabolites of 3,4-Dihydro-2,2-dimethyl-2H-naphthol[1,2-b]pyran-5,6-dione (ARQ 501; β-Lapachone) in Whole Blood

Abstract

ABSTRACT:3,4-Dihydro-2,2-dimethyl-2H-naphthol[1,2-b]pyran-5,6-dione (ARQ 501; ␤-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°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 spectrometry-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.

The chemical and biological activities of quinones: overview and implications in analytical detection

“…Using LC-MS coupled to a radioisotope counting system it has been shown that b-lapachone (24) is extensively metabolized in whole blood under in vitro conditions and that the enzymatic activity is located in the RBC. By determining the percent of radioactivity present in protein pellet prepared from whole blood spiked with 14 C b-lapachone, it has been proven that covalent protein binding of b-lapachone and/or its metabolites is a minor contributor in the failure of its detection in blood (Miao et al 2008). …”

“…Miao et al (Miao et al 2008) have shown in an in vitro study that b-lapachone (24), a promising anticancer compound, is metabolized by red blood cells (RBCs). While studying its in vitro metabolism in plasma and whole blood, the compound could not be detected with conventional LC-MS.…”

A Naphthoquinone Derivative Can Induce Anemia through Phosphatidylserine Exposure-Mediated Erythrophagocytosis

“…Considering the vulnerability of erythrocytes to oxidative stress, toxicity of ␤L to erythrocytes could be easily foreseeable. The recent finding of Miao et al (2008) that a ␤L derivative could be rapidly sequestered into and metabolized in erythrocytes further supports the specific and selective toxicities of ␤L to erythrocyte. Besides ␤L, many ROS-generating drugs are being developed or marketed for therapeutic uses in cancer and other diseases (Davis et al, 2001;Fibach and Rachmilewitz, 2008;Trachootham et al, 2009).…”

Impact of protein binding on the analytical detectability and anticancer activity of thymoquinone

“…While studying the in vitro metabolism of β-lapachone in plasma and whole blood, the compound could not be detected with ESI-LC/ MS. The failure in the detection of β-lapachone in blood by conventional analytical methods led to the use of the radiolabeled 14 C β-lapachone that was necessary in studying its metabolic profile [37].…”