NAMPT and cancer: FK866 treatment does not affect the NAD+ mitochondrial pool; therefore, cancer cells may be more sensitive than noncancerous cells to FK866.194 Moreover, FK866 cytotoxicity seems to be higher in tumors that express higher NAMPT levels and are relatively more glycolysis-dependent.223,234 NAMPT is also essential for normal cells; therefore, the adverse side effects of NAMPT inhibitors are important in clinical trials.