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Xenobiotica. 2013 Sep;43(9):780-4. doi: 10.3109/00498254.2013.767481. Epub 2013 Feb 4.

Activation of the anti-cancer agent upamostat by the mARC enzyme system.

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Department of Pharmaceutical and Medicinal Chemistry, Pharmaceutical Institute, Christian-Albrechts-University of Kiel, Kiel, Germany.


Upamostat (Mesupron®) is a new small molecule serine protease inhibitor. The drug candidate was developed to inhibit the urokinase-type plasminogen activator (uPA) system, which plays a major role in tumor invasion and metastasis. Upamostat is currently in clinical development as an anti-metastatic and non-cytotoxic agent against pancreatic and breast cancer. Upamostat is the orally available amidoxime- (i.e. hydroxyamidine-) prodrug of the pharmacologically active form, WX-UK1. In this study, the reductive enzymatic activation of upamostat to its corresponding amidine WX-UK1 was analyzed. The recently discovered molybdenum enzyme "mitochondrial Amidoxime Reducing Component" (mARC) catalyses together with its electron transport proteins cytochrome b₅ and NADH cytochrome b₅ reductase the reduction of N-hydroxylated prodrugs. In vitro biotransformation assays with porcine subcellular fractions and the reconstituted human enzymes demonstrate an mARC-dependent N-reduction of upamostat.

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