Abstract 6254: Identification of nicotinic acid phosphoribosyltransferase inhibitors with anticancer properties by in silico drug design
Authors: Ghanem Moustafa , Khalifa Amr , Caffa Irene , Nahimana Aimable , Duchosal Michel , Rio Alberto Del , Bruzzone Santina , Piancente Francesco , Nencioni Alessio 
Published: June 2022

Abstract
Cancer cells rely heavily on sustained NAD levels to support their survival and proliferation. Thus, depleting NAD levels in tumor cells through interference with their NAD-biosynthetic machinery has been proposed as a promising anticancer strategy. Several pathways contribute to NAD production in mammals, such as the de novo and the Preiss-Handler (PH) pathways, which generate NAD from tryptophan and from nicotinic acid, respectively. In addition, the NAD salvage pathway, which utilizes nicotinamide as a substrate, is also a major NAD-producing route and its rate-limiting enzyme, nicotinamide phosphoribosyltransferase (NAMPT), is commonly overexpressed in a multitude of human cancers. Over the past two decades, several potent NAMPT inhibitors have been developed, such as FK866. However, their clinical efficacy has proven limited, suggesting that the other NAD-producing routes are frequently also active in cancer cells and are responsible for causing resistance to NAMPT inhibitors. Recently, we have shown nicotinic acid phosphoribosyl transferase (NAPRT), the key enzyme in the PH pathway, to play an important role in NAD metabolism in cancer cells. We demonstrated that NAPRT is amplified and overexpressed in several types of solid tumors and that its expression is a critical determinant of cancer cell susceptibility to NAMPT inhibitors. Although several NAPRT inhibitors have been reported, including 2-hydroxy nicotinic acid (2-HNA), their low potency and/or poor solubility limit their clinical applicability. To identify new NAPRT inhibitors with enhanced pharmacological profiles, we performed a high-throughput molecular docking screen, taking advantage of the availability of NAPRT crystal structure. The first 500 hits were visually inspected to prioritize compounds that reproduced, at least in part, the putative binding mode of known substrates and inhibitors and complied with simple physicochemical rules such as Lipinski’s rule of five. In addition, several 2-HNA analogs were selected. Altogether, this led to a final list of 50 compounds that were tested in vitro. We show that four compounds from this list were able to sensitize NAPRT-overexpressing ovarian cancer cells to FK866, resulting in a more significant reduction in intracellular NAD levels, as well as in a much more pronounced cytotoxicity as compared to FK866 alone. The inhibitory constant (Ki) of the new NAPRT inhibitors was found to be in the micromolar range. In conclusion, in silico molecular docking screens are a promising approach to identify new NAPRT inhibitors with anticancer effects.
Citation Format: Moustafa Ghanem, Amr Khalifa, Irene Caffa, Aimable Nahimana, Michel Duchosal, Alberto Del Rio, Santina Bruzzone, Francesco Piancente, Alessio Nencioni. Identification of nicotinic acid phosphoribosyltransferase inhibitors with anticancer properties by in silico drug design [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6254.