Abstract 1137: Identification of a high selective SMARCA2 degrader which effectively suppresses the SMARCA4-deficient tumors in vitro and in vivo

Abstract

Abstract The SWI/SNF chromatin-remodeling complex plays essential roles in a variety of cellular processes including differentiation, proliferation and DNA repair. Mammalian SWI/SNF complexes always contain one of two mutually exclusive and structurally highly related ATPases: SMARCA2/BRM or SMARCA4/BRG1, as its catalytic subunit, which hydrolyze ATP to drive nucleosome movement. It is reported that absence of SMARCA4 are present in several cancers and these SMARCA4 deficient cells highly depend on its paralog SMARCA2 for survival. Furthermore, concurrent inhibition of SMARCA2 and SMARCA4 is fatal to normal cells. Therefore, it holds great therapeutic promise to treat SMARCA4 deficient cancers with selective SMARCA2 degraders while leaving SMARCA4 wild type cells unaffected. Here, we report that SCR-9140 is a high selective SMARCA2 degrader which demonstrates superior anti-tumor activity and low cytotoxicity against non-malignant cells. SCR-9140 strongly degrades SMARCA2 with DC50 of <1 nM and achieves the complete protein degradation (Dmax of >95%) and also shows 100-fold degradation selectivity over SMARCA4 with DC50 of around 100 nM and Dmax of <60% in HiBiT knock-in SW1573 cells. Across a panel of SMARCA4 deficient tumor cell lines, SCR-9140 potently inhibits proliferation with IC50 values ranging from 1 to 50 nM. Due to the high selectivity over SMARCA4, SCR-9140 neither inhibits proliferation of SW1573 (SMARCA2-WT SMARCA4-WT) cells nor NCI-H1581 (SMARCA2-DEL SMARCA4-DEL) cells with IC50s of over 2000 nM. The degraders with poor selectivity of SMARCA2/4 (DC50 ratio: < 10 folds, Dmax of SMARCA4 > 80%) strongly inhibit the SW1573 cells proliferation with IC50s < 100nM, while there are no significant effects on the NCI-H1581 cells ascribing to the absence of targets. Furthermore, SCR-9140 demonstrates weak cytotoxicity on non-malignant cells, such as WI-38 (human lung fibroblast cells), THLE-2 (human liver cells), and human PBMC, rendering it the greater therapeutic window. In a CDX model of NSCLC, SCR-9140 effectively inhibits tumor growth and TGI correlates well with SMARCA2 degradation in tumors. In conclusion, our potent and selective SMARCA2 degrader, SCR-9140 induces strong synthetic lethality in SMARCA4 deficient cells in vitro and in vivo and shows great safety margin in normal cells. Citation Format: Feng Zhou, Zhiyong Yu, Ruonan Chen, Feng Tang, Peng Gu, Wenqing Yang, Liting Xue, Ping Chen, Renhong Tang. Identification of a high selective SMARCA2 degrader which effectively suppresses the SMARCA4-deficient tumors in vitro and in vivo [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 1137.