FK866 is an inhibitor of nicotinamide phosphoribosyltransferase (NMPRTase) with IC50 values ranging between 0.09 nM and 27.2 nM [1].

NAD plays a vital role in numerous biochemical and biologic processes. Targeting NAD synthesis is thought to be a selective manner to kill cancer cells since cancer cells have a higher rate of NAD turnover compared with normal cells. In the in vitro MTT assay using a panel of 41 human hematologic cancer

cell lines, most cancer cells are sensitive to low concentrations of FK866. Among these cancer cells, AML cells are most sensitive. FK866 is shown selective to human hematologic malignant cells and the normal human HPCs are resistant to FK866 treatment. It is found that FK866 induces cell death in a caspase-independent pathway but in a dose-dependent manner to induce mitochondrial membrane depolarization. Additionally, FK866 induces cell autophagy dependenting on de novo protein synthesis. FK866 also reduces ATP levels in ML-2 cells due to the inhibition of NAD synthesis. The antitumor efficacy of FK866 is also shown in the in vivo models. FK866 significantly prevents tumor growth both in mice xenografted subcutaneously with AML-M4 and Namalwa cells. Furthermore, FK866 clears tumor cells to below detectable levels and results in 80% survival for a long-term [1].

References:
[1] Nahimana A, Attinger A, Aubry D, Greaney P, Ireson C, Thougaard AV, Tjørnelund J, Dawson KM, Dupuis M, Duchosal MA. The NAD biosynthesis inhibitor APO866 has potent antitumor activity against hematologic malignancies. Blood. 2009 Apr 2; 113 (14): 3276-86.