Nicotinamide phosphoribosyltransferase (NAMPT; also known as Pre-B cell-enhancing factor PBEF) catalyzes the synthesis of nicotinamide mononucleotide (NMN) from nicotinamide and 5-phosphoribosylpyrophosphate (PRPP), the rate-limiting step in the NAD biosynthesis pathway starting from nicotinamide (1,2). NAD biosynthesis mediated by NAMPT plays a critical role in glucose-stimulated insulin secretion in pancreatic beta cells (3). Both NAMPT inhibitors and activators have been sought for clinical applications (4,5). NAMPT has intra- and extracellular forms (iNAMPT and eNAMPT), and deacetylation of iNAMPT by SIRT1 promotes eNAMPT secretion through a nonclassical secretory pathway (3,6). eNAMPT, independent of its enzymatic activity, can induce epithelial-to-mesenchymal transition in mammary epithelial cells and promote monocyte differentiation into tumor-supporting M2 macrophage (7,8).