Nicotinic Acid Restriction Enhances the Therapeutic Benefit of <scp>NAMPT</scp> Inhibition in Small‐Cell Lung Cancer Models

ABSTRACT Small‐cell lung cancer (SCLC) is an aggressive malignancy with limited therapeutic options. We previously showed that nicotinic acid riboside (NAR) sustains NAD biosynthesis in vivo and compensates for NAMPT inhibition in SCLC models. Here, we evaluated combining NAMPT inhibition with dietary nicotinic acid (NA) restriction to suppress NAR‐dependent NAD biosynthesis. This combination showed enhanced antitumor activity consistent with synthetic lethality in SCLC CDX models and showed robust efficacy in PDX models, including those derived from chemotherapy‐refractory tumors. In most CDX models examined, combination therapy showed greater antitumor activity than standard chemotherapy with cisplatin and etoposide. Although we did observe transient leukopenia, the treatment was otherwise better tolerated than chemotherapy, with less impact on body weight and platelet counts. These findings support NAD metabolism–targeted therapy as a promising strategy to treat SCLC.