Inhibition of nicotinamide phosphoribosyltransferase (NAMPT) with OT-82 induces DNA damage, cell death, and suppression of tumor growth in preclinical models of Ewing sarcoma

Anna E Gibson; Choh Yeung; Sameer H Issaq; Victor J Collins; Michael Gouzoulis; Yiping Zhang; Jiuping Ji; Arnulfo Mendoza; Christine M Heske

doi:10.1038/s41389-020-00264-0

Inhibition of nicotinamide phosphoribosyltransferase (NAMPT) with OT-82 induces DNA damage, cell death, and suppression of tumor growth in preclinical models of Ewing sarcoma

Oncogenesis. 2020 Sep 10;9(9):80. doi: 10.1038/s41389-020-00264-0.

Authors

Anna E Gibson¹, Choh Yeung¹, Sameer H Issaq^{1

2}, Victor J Collins¹, Michael Gouzoulis¹, Yiping Zhang³, Jiuping Ji³, Arnulfo Mendoza¹, Christine M Heske⁴

Affiliations

¹ Pediatric Oncology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA.
² Urologic Oncology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA.
³ National Clinical Target Validation Laboratory, Division of Cancer Treatment and Diagnosis, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA.
⁴ Pediatric Oncology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA. [email protected].

Abstract

NAMPT mediates the rate-limiting step of the NAD salvage pathway, which maintains cellular bioenergetics and provides a necessary substrate for functions essential to rapidly proliferating cancer cells. In this study, we evaluated the efficacy and mechanisms of action of OT-82, a novel, high-potency NAMPT inhibitor with a favorable toxicity profile, in preclinical models of Ewing sarcoma (EWS), an aggressive pediatric malignancy with previously reported selective sensitivity to NAMPT inhibition. We show that OT-82 decreased NAD concentration and impaired proliferation of EWS cells in a dose-dependent manner, with IC₅₀ values in the single-digit nanomolar range. Notably, genetic depletion of NAMPT phenocopied pharmacological inhibition. On-target activity of OT-82 was confirmed with the addition of NMN, the product of NAMPT, which rescued NAD concentration and EWS cellular viability. Mechanistically, OT-82 treatment resulted in impaired DNA damage repair through loss of PARP activity, G2 cell-cycle arrest, and apoptosis in EWS cells. Additional consequences of OT-82 treatment included reduction of glycolytic and mitochondrial activity. In vivo, OT-82 impaired tumor growth and prolonged survival in mice bearing EWS xenografts. Importantly, antitumor effect correlated with pharmacodynamic markers of target engagement. Furthermore, combining low-dose OT-82 with low doses of agents augmenting DNA damage demonstrated enhanced antitumor activity in vitro and in vivo. Thus, OT-82 treatment represents a potential novel targeted approach for the clinical treatment of EWS.