ABSTRACT
NAMPT expression is elevated in many cancers, making this protein a potential target for anticancer therapy. We have carried out both NMR based and TR-FRET based fragment screens against human NAMPT and identified six novel binders with a range of potencies. Co-crystal structures were obtained for two of the fragments bound to NAMPT while for the other four fragments force-field driven docking was employed to generate a bound pose. Based on structural insights arising from comparison of the bound fragment poses to that of bound FK866 we were able to synthetically elaborate one of the fragments into a potent NAMPT inhibitor.
Subject(s)
Acrylamides/pharmacology , Cytokines/antagonists & inhibitors , Drug Discovery , Enzyme Inhibitors/pharmacology , Nicotinamide Phosphoribosyltransferase/antagonists & inhibitors , Piperidines/pharmacology , Acrylamides/chemical synthesis , Acrylamides/chemistry , Cytokines/genetics , Cytokines/metabolism , Dose-Response Relationship, Drug , Drug Evaluation, Preclinical , Enzyme Inhibitors/chemical synthesis , Enzyme Inhibitors/chemistry , Fluorescence Resonance Energy Transfer , Humans , Molecular Docking Simulation , Molecular Structure , Nicotinamide Phosphoribosyltransferase/genetics , Nicotinamide Phosphoribosyltransferase/metabolism , Piperidines/chemical synthesis , Piperidines/chemistry , Structure-Activity RelationshipABSTRACT
Herein we disclose SAR studies that led to a series of isoindoline ureas which we recently reported were first-in-class, non-substrate nicotinamide phosphoribosyltransferase (NAMPT) inhibitors. Modification of the isoindoline and/or the terminal functionality of screening hit 5 provided inhibitors such as 52 and 58 with nanomolar antiproliferative activity and preclinical pharmacokinetics properties which enabled potent antitumor activity when dosed orally in mouse xenograft models. X-ray crystal structures of two inhibitors bound in the NAMPT active-site are discussed.
Subject(s)
Antineoplastic Agents/chemistry , Antineoplastic Agents/pharmacology , Cytokines/antagonists & inhibitors , Enzyme Inhibitors/chemistry , Enzyme Inhibitors/pharmacology , Nicotinamide Phosphoribosyltransferase/antagonists & inhibitors , Urea/analogs & derivatives , Urea/pharmacology , Animals , Antineoplastic Agents/pharmacokinetics , Antineoplastic Agents/therapeutic use , Cell Line, Tumor , Cell Proliferation/drug effects , Crystallography, X-Ray , Cytokines/chemistry , Cytokines/metabolism , Drug Discovery , Enzyme Inhibitors/pharmacokinetics , Enzyme Inhibitors/therapeutic use , Humans , Isoindoles/chemistry , Isoindoles/pharmacokinetics , Isoindoles/pharmacology , Isoindoles/therapeutic use , Mice , Models, Molecular , Neoplasms/drug therapy , Neoplasms/metabolism , Neoplasms/pathology , Nicotinamide Phosphoribosyltransferase/chemistry , Nicotinamide Phosphoribosyltransferase/metabolism , Structure-Activity Relationship , Urea/pharmacokinetics , Urea/therapeutic useABSTRACT
Cancer cells are highly reliant on NAD+-dependent processes, including glucose metabolism, calcium signaling, DNA repair, and regulation of gene expression. Nicotinamide phosphoribosyltransferase (NAMPT), the rate-limiting enzyme for NAD+ salvage from nicotinamide, has been investigated as a target for anticancer therapy. Known NAMPT inhibitors with potent cell activity are composed of a nitrogen-containing aromatic group, which is phosphoribosylated by the enzyme. Here, we identified two novel types of NAM-competitive NAMPT inhibitors, only one of which contains a modifiable, aromatic nitrogen that could be a phosphoribosyl acceptor. Both types of compound effectively deplete cellular NAD+, and subsequently ATP, and produce cell death when NAMPT is inhibited in cultured cells for more than 48 hours. Careful characterization of the kinetics of NAMPT inhibition in vivo allowed us to optimize dosing to produce sufficient NAD+ depletion over time that resulted in efficacy in an HCT116 xenograft model. Our data demonstrate that direct phosphoribosylation of competitive inhibitors by the NAMPT enzyme is not required for potent in vitro cellular activity or in vivo antitumor efficacy. Mol Cancer Ther; 16(7); 1236-45. ©2017 AACR.
