Abstract 481: Investigating molecular glues as a new therapeutic approach to high-risk neuroblastoma

Abstract High-risk neuroblastoma (NB) is the most common extracranial solid tumor of childhood. Despite extensive study, treatments remain highly toxic and are often insufficient to cure. Thus, there is an urgent need to develop more effective and less toxic treatments for children with NB. NB commonly displays reliance on a relatively small cohort of transcription factors (TFs) and epigenetic proteins to drive cell growth, however, many of these targets are inaccessible with conventional small molecules. In recent years, new modalities such as targeted protein degradation (TPD) have emerged. TPD may permit small molecule degradation of traditionally “undruggable” targets, such as TFs. This makes TPD a particularly attractive modality for defining new therapeutic strategies for high-risk NB. One category of TPD agents are molecular glues (MGs). MGs are monovalent small molecules capable of simultaneously binding to an E3 ligase receptor such as CRBN (cereblon), and a target protein of interest. Importantly, in comparison to conventional protein inhibitors, MGs do not require a conventional binding pocket on the protein of interest to bind to it, and can be utilized in sub-stoichiometric concentrations. Thus, this may result in the recruitment, polyubiquitination, and subsequent proteasomal degradation of proteins previously thought to be “undruggable.” Here, we demonstrate that high-risk NB cells are critically sensitive to a cluster of previously unknown MGs. We performed high-throughput screening of a proprietary library (>4000 unique compounds) of MGs in two MYCN-amplified NB cell lines, Kelly and MHHNB11. These two cell lines demonstrate a strikingly close correlation in Cell-Titer Glo-based growth response to MGs, as compared with an outgroup of other MG-responsive cancer cell lines. We identified a unique subcluster of 112 common MGs that display >70% growth inhibition in both cell lines. To identify the mechanism of cell growth inhibition, we established Kelly cells with stable knockout of CRBN, and coupled these with screening to confirm that the majority of these MGs (84%; 94/112) require CRBN expression. To rule out common off-target effects of MGs, candidate compounds were then tested in cells transgenically expressing either wild-type or degradation-resistant GSPT1 (G575N) constructs, revealing a subset of MGs retaining cytotoxicity without effecting GSPT1 protein levels. Current studies are focused on determining the targets of these high confidence MGs, as a foundation for preclinical in vivo studies. These studies will identify new compounds with defined mechanisms of action, with an ultimate goal of developing new treatments that are more effective and less toxic for children with NB. Citation Format: Ian Delahunty, Gisele Nishiguchi, Yang Zhang, Abigail Fish, Anand Mayasundari, Jun Qi, Brian Abraham, Anang Shelat, Zoran Rankovic, Adam Durbin. Investigating molecular glues as a new therapeutic approach to high-risk neuroblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 481.