NAMPT and hepatocellular carcinoma: After incubation with human hepatocellular carcinoma cell line HepG2 for 24 hours, MS0 decreased the cellular NAD level by ~70% at 1 μM, while the structurally similar compound 733had no inhibition on NAMPT activity and did not show any effect on cellular NAD level even at 100 μM (Fig. 2A).