Abstract 6921: NAMPT inhibition impacts energy metabolism, induces DNA damage, and mediates tumor regression in preclinical neuroblastoma models

Abstract Cancer cell metabolism is altered to meet increased metabolic demands of proliferating cancer cells. Reprogrammed metabolic pathways represent potential cell type and context specific therapeutic opportunities. Targeting NAD+ production via inhibition of the NAD+ salvage pathway presents one such potential opportunity, as NAD+ is essential for energy metabolism and other downstream processes. Presently, nicotinamide phosphoribosyltransferase (NAMPT) is the only clinically targetable enzyme in this pathway. We conducted a high-throughput cancer cell line screen and identified that neuroblastoma (NB) cells are significantly more sensitive to NAMPT inhibitors (NAMPTis) than most other solid tumors, with IC50 values >20-fold less than the cell line panel average. NB is the most common extracranial solid tumor in children and a tumor of high unmet need, accounting for 15% of pediatric cancer deaths. We used two clinical NAMPTis under early phase study (OT-82 and KPT-9274) to validate our drug screen results in 10 molecularly diverse NB cell lines including 2 NB PDX-derived cell lines. We investigated the mechanistic effects of NAMPT inhibition on NAD+-dependent pathways and analyzed the in vivo effects of OT-82 in 3 orthotopic NB models. Treatment of NB cell lines with NAMPTis resulted in non-apoptotic cell death within 48 hours and failure of cells to proliferate even following replacement with drug-free media. NAMPTis reduced intracellular NAD+ levels and co-treatment with NMN, the product of NAMPT, fully rescued cell viability, verifying NAD+-dependence and on-target activity of each NAMPTi. Moreover, reductions in ATP of 50% and >90% were observed after 24 hours and 72 hours of treatment, respectively. Examination of drug effects on glucose metabolism using extracellular flux and metabolomics analyses demonstrated cell line-specific effects, including reduction in oxidative phosphorylation and/or glycolysis with depletion of metabolites produced via NAD+-consuming enzymes. Investigation of the effects of NAMPTis on other key NAD+ consuming enzymes including sirtuin 1 (SIRT1) and poly (ADP-ribose) polymerase (PARP), demonstrated significant loss of activity of both enzymes in a time-dependent manner. As loss of PARP and SIRT1 activity can compromise DNA repair, comet assays were used to assess the extent of DNA damage and revealed an increase in DNA damage upon NAMPTi treatment in all models. In vivo studies testing OT-82 in orthotopic xenografts demonstrated significant tumor shrinkage. Across models, 23/26 mouse tumors had average volume reductions of 67% (range 10%-99%). Tissue studies from these experiments are ongoing and will be reported. Together, these data demonstrate that in NB, multiple critical pathways are impacted by the loss of NAD+ mediated by NAMPT inhibition and suggest NAMPTis may have translational potential as a novel agent against NB. Citation Format: Amy Yu, Sophia Varriano, Amy James, Kristine Isanogle, Nimit Patel, Caleb Kim, Unsun Lee, Victor J. Collins, Ariana E. Nelson, Ming Sun, Ye Yang, Bhushan L. Thakur, Arnulfo Mendoza, Sameer H. Issaq, John F. Shern, Mirit I. Aladjem, Daniel R. Crooks, Joseph D. Kalen, Simone Difilippantonio, Craig J. Thomas, Rosa Nguyen, Carol J. Thiele, Christine M. Heske. NAMPT inhibition impacts energy metabolism, induces DNA damage, and mediates tumor regression in preclinical neuroblastoma models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 6921.