Nicotinamide phosphoribosyltransferase is a molecular target of potent anticancer agents identified from phenotype-based drug screening.

Phenotypic screening in drug discovery has been revived with the expectation of providing promising lead compounds and drug targets and improving the success rate of drug approval. However, target identification remains a major bottleneck in phenotype-based drug discovery. We identified the lead compounds K542 and K405 with a selective inhibition of cell viability against sphingosine-1-phosphate lyase 1 (SGPL1)-transduced ES-2 cells by phenotypic screening. We therefore performed an in vivo pharmacological examination and observed the antitumor activity of K542 in an HT-1080 tumor-bearing mouse xenograft model. SGPL1 was expected to be a therapeutic target in some cancers, suggesting that these lead molecules might be promising candidates; however, their mechanisms of action still remain unexplained. We therefore synthesized the affinity probe Ind-tag derived from K542 and identified the proteins binding to Ind-tag via a pull-down experiment. Proteomics and biochemical analyses revealed that the target molecule of these lead compounds was Nicotinamide phosphoribosyltransferase (NAMPT). We established K542-resistant DLD-1 and HT-1080 cells, and genetic analyses of these cells identified a missense mutation in the NAMPT-encoding gene. This enzymatic experiment clearly showed that K393 exerts enzymatic inhibition against NAMPT. These proteomics, genetics and biochemical analyses clarified that compounds K542 and K405 were NAMPT inhibitors.

Effect of orally administered KF66490, a phosphodiesterase 4 inhibitor, on dermatitis in mouse models.

Due to the broad anti-inflammatory and immunomodulatory actions of phosphodiesterase (PDE) 4 inhibitors, it has been proposed that PDE4 inhibitors might be efficacious for skin disorders such as atopic dermatitis. KF66490 is a newly developed PDE4 inhibitor that inhibits PDE4B (IC(50)=220 nM) and the production of tumor necrosis factor (TNF)-alpha by mouse peritoneal exudated cells stimulated with lipopolysaccharide (IC(50)=855 nM). To evaluate efficacy of KF66490 in atopic dermatitis (AD) models, on skin inflammation induced by repeated application of 2,4,6-trinitro-1-chlorobenzene (TNCB) on ear in BALB/c mice and on spontaneously AD-like skin diseases in NC/Nga mice. BALB/c mice were sensitized with 0.3% w/v TNCB applied to the ear on day-7, followed by application three times a week from days 0 to 21. NC/Nga mice spontaneously developed dermatitis symptoms under conventional conditions. Test compounds were administered orally once daily during experiments. In the TNCB-induced dermatitis model, KF66490 significantly inhibited the increase in ear thickness and interleukin (IL)-4 and IL-1beta levels in the ear. Histopathological and immunohistochemical analysis revealed that KF66490 significantly inhibited the proliferation of fibroblasts and CD3-positive T cells infiltration into the ear. In addition, KF66490 significantly suppressed the development of dermatitis in NC/Nga mice on all observation days, except for 5 and 6 weeks after the first dose. Furthermore, KF66490 produced less potent emetic effects than the first generation PDE4 inhibitor, rolipram. The present results suggest that KF66490 has excellent potential as an oral medicine for the treatment of atopic dermatitis.