Abstract
Inhibiting NAD biosynthesis by blocking the function of nicotinamide phosphoribosyl transferase (NAMPT) is an attractive therapeutic strategy for targeting tumor metabolism. However, the development of drug resistance commonly limits the efficacy of cancer therapeutics. This study identifies mutations in NAMPT that confer resistance to a novel NAMPT inhibitor, GNE-618, in cell culture and in vivo, thus demonstrating that the cytotoxicity of GNE-618 is on target. We determine the crystal structures of six NAMPT mutants in the apo form and in complex with various inhibitors and use cellular, biochemical and structural data to elucidate two resistance mechanisms. One is the surprising finding of allosteric modulation by mutation of residue Ser165, resulting in unwinding of an α-helix that binds the NAMPT substrate 5-phosphoribosyl-1-pyrophosphate (PRPP). The other mechanism is orthosteric blocking of inhibitor binding by mutations of Gly217. Furthermore, by evaluating a panel of diverse small molecule inhibitors, we unravel inhibitor structure activity relationships on the mutant enzymes. These results provide valuable insights into the design of next generation NAMPT inhibitors that offer improved therapeutic potential by evading certain mechanisms of resistance.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, U.S. Gov't, Non-P.H.S.
MeSH terms
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Antineoplastic Agents / pharmacology*
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Catalytic Domain
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Cell Line, Tumor
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Cytokines / antagonists & inhibitors*
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Cytokines / chemistry*
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Cytokines / genetics
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Drug Resistance, Neoplasm*
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Enzyme Inhibitors / pharmacology*
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Humans
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Models, Molecular
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Mutation
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Nicotinamide Phosphoribosyltransferase / antagonists & inhibitors*
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Nicotinamide Phosphoribosyltransferase / chemistry*
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Nicotinamide Phosphoribosyltransferase / genetics
Substances
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Antineoplastic Agents
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Cytokines
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Enzyme Inhibitors
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Nicotinamide Phosphoribosyltransferase
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nicotinamide phosphoribosyltransferase, human
Grants and funding
The authors received no specific funding for this work. Forma Therapeutics provided support in the form of salaries for Y-CH, XZ and KWB, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the ‘author ontributions’ section. Genentech, Inc. provided support in the form of salaries for WW, KE, AO, JW, HL, YX, MK, MC, BB, EC, LC, PSD, DS, TO'B, LDB, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the ‘author contributions’ section.