A practical synthesis of a novel DPAGT1 inhibitor, aminouridyl phenoxypiperidinbenzyl butanamide (APPB) for in vivo studies
Immunotherapy that targets N-linked glycans has not yet been developed due in large part to the lack of specificity of N-linked glycans between normal and malignant cells. N-Glycan chains are synthesized by the sequential action of glycosyl transferases in the Golgi apparatus. It is an overwhelming task to discover drug-like inhibitors of glycosyl transferases that block the synthesis of specific branching processes in cancer cells, killing tumor cells selectively. It has long been known that N-glycan biosynthesis can be inhibited by disruption of the first committed enzyme, dolichyl-phosphate N-acetylglucosaminephosphotransferase 1 (DPAGT1). Selective DPAGT1 inhibitors have the promising therapeutic potential for certain solid cancers that require increased branching of N-linked glycans in their growth progressions. Recently, we discovered that an anti-Clostridium difficile molecule, aminouridyl phenoxypiperidinbenzyl butanamide (APPB) showed DPAGT1 inhibitory activity with the IC_(50) value of 0.25 μM. It was confirmed that APPB inhibits N-glycosylation of β-catenin at 2.5 nM concentration. A sharp difference between APPB and tunicamycin was that the hemolytic activity of APPB is significantly attenuated (IC_(50) > 200 μM RBC). Water solubility of APPB is >350-times greater than that of tunicamycin (78.8 mg/mL for APPB, <0.2 mg/mL for tunicamycin). A novel DPAGT1 inhibitor, APPB selectively inhibits growth of the solid tumors (e.g. KB, LoVo, SK-OV-3, MDA-MB-432S, HCT116, Panc-1, and AsPC-1) at low μM concentrations, but does not inhibit growth of a leukemia cell (L1210) and the healthy cells (Vero and HPNE) at these concentrations. In vitro metabolic stability using rat liver microsomes indicated that a half-life (t_(1/2)) of APPB is sufficiently long (>60 min) for in vivo studies (PK/PD, safety profiles, and in vivo efficacy) using animal models. We have refined all steps in the previously reported synthesis for APPB for larger-scale. This article summarizes protocols of gram-scale synthesis of APPB and its physicochemical data, and a convenient DPAGT1 assay.
© 2019 Published by Elsevier B.V. Under an Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) Received 6 December 2018, Accepted 23 September 2019, Available online 27 September 2019. The National Institutes of Health is greatly acknowledged for financial support of this work (Grant GM114611). MK also thank University of Tennessee Health Science Center for generous financial support (CORNET award). NMR data were obtained on instruments supported by the NIH Shared Instrumentation Grant.
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