NAMPT and cancer: Yet, we feel important to briefly outline four aspects of these inhibitors that are often overlooked in medicinal chemistry programs: (i) their potential toxicity; (ii) the fact that the target protein is dual-faced, with an intracellular form and an extracellular form that may have different physiopathological roles; (iii) the fact that the tumoral cell might not be the sole target, or the most important target, of these inhibitors in cancer; (iv) the possible role of NAPRT in determining NAMPT inhibitor sensitivity or resistance.