ABSTRACT
NAMPT, an enzyme essential for NAD+ biosynthesis, has been extensively studied as an anticancer target for developing potential novel therapeutics. Several NAMPT inhibitors have been discovered, some of which have been subjected to clinical investigations. Yet, the on-target hematological and retinal toxicities have hampered their clinical development. In this study, we report the discovery of a unique NAMPT inhibitor, LSN3154567. This molecule is highly selective and has a potent and broad spectrum of anticancer activity. Its inhibitory activity can be rescued with nicotinic acid (NA) against the cell lines proficient, but not those deficient in NAPRT1, essential for converting NA to NAD+ LSN3154567 also exhibits robust efficacy in multiple tumor models deficient in NAPRT1. Importantly, this molecule when coadministered with NA does not cause observable retinal and hematological toxicities in the rodents, yet still retains robust efficacy. Thus, LSN3154567 has the potential to be further developed clinically into a novel cancer therapeutic. Mol Cancer Ther; 16(12); 2677-88. ©2017 AACR.
Subject(s)
Cytokines/antagonists & inhibitors , Niacin/therapeutic use , Nicotinamide Phosphoribosyltransferase/antagonists & inhibitors , Retinal Pigment Epithelium/drug effects , Animals , Humans , Mice , Niacin/pharmacology , Retinal Pigment Epithelium/pathologyABSTRACT
Nicotinamide phosphoribosyltransferase (NAMPT) catalyzes the first rate-limiting step in converting nicotinamide to NAD(+), essential for cellular metabolism, energy production, and DNA repair. NAMPT has been extensively studied because of its critical role in these cellular processes and the prospect of developing therapeutics against the target, yet how it regulates cellular metabolism is not fully understood. In this study we utilized liquid chromatography-mass spectrometry to examine the effects of FK866, a small molecule inhibitor of NAMPT currently in clinical trials, on glycolysis, the pentose phosphate pathway, the tricarboxylic acid (TCA) cycle, and serine biosynthesis in cancer cells and tumor xenografts. We show for the first time that NAMPT inhibition leads to the attenuation of glycolysis at the glyceraldehyde 3-phosphate dehydrogenase step due to the reduced availability of NAD(+) for the enzyme. The attenuation of glycolysis results in the accumulation of glycolytic intermediates before and at the glyceraldehyde 3-phosphate dehydrogenase step, promoting carbon overflow into the pentose phosphate pathway as evidenced by the increased intermediate levels. The attenuation of glycolysis also causes decreased glycolytic intermediates after the glyceraldehyde 3-phosphate dehydrogenase step, thereby reducing carbon flow into serine biosynthesis and the TCA cycle. Labeling studies establish that the carbon overflow into the pentose phosphate pathway is mainly through its non-oxidative branch. Together, these studies establish the blockade of glycolysis at the glyceraldehyde 3-phosphate dehydrogenase step as the central metabolic basis of NAMPT inhibition responsible for ATP depletion, metabolic perturbation, and subsequent tumor growth inhibition. These studies also suggest that altered metabolite levels in tumors can be used as robust pharmacodynamic markers for evaluating NAMPT inhibitors in the clinic.
Subject(s)
Enzyme Inhibitors/pharmacology , NAD/biosynthesis , Neoplasms/metabolism , Neoplasms/pathology , Nicotinamide Phosphoribosyltransferase/antagonists & inhibitors , Acrylamides/pharmacology , Adenosine Triphosphate/deficiency , Adenosine Triphosphate/metabolism , Animals , Carbon Isotopes , Cell Death/drug effects , Cell Line, Tumor , Citric Acid Cycle/drug effects , Female , Glycolysis/drug effects , Humans , Isotope Labeling , Mice , Mice, SCID , Nicotinamide Phosphoribosyltransferase/metabolism , Pentose Phosphate Pathway/drug effects , Piperidines/pharmacology , Serine/biosynthesis , Xenograft Model Antitumor AssaysABSTRACT
The synthesis and structure-activity relationship (SAR) trends of a new class of N-(azacycloalkyl)bisindolylmaleimides 1, acyclic derivatives of staurosporine, is described. The representative compound for this series (1e) exhibits an IC(50) of 40-50 nM against the human PKCbeta(1) and PKCbeta(2) isozymes and selectively inhibits the PKCbeta isozymes in comparison to other PKC isozymes (alpha, gamma, delta, epsilon, lambda, and eta). The series is also kinase selective for PKC in comparison to other ATP-dependent kinases. A comparison of the PKC isozyme and kinase activity of the series is made to the kinase inhibitor staurosporine.
