Abstract 3964: Co-targeting MDM2-p53 and BCL-2 apoptosis pathways overcomes resistance conferred by acquired BCL-2 gene mutations in preclinical models
Authors: Deng Jing , Zhang Kaixiang , Tang Qiuqiong , Huang Xiaojing , Wang Qixin , Li Na , Fang Douglas D. , Yang Dajun , Zhai Yifan 
Published: June 2022

Abstract
The BCL-2 inhibitor venetoclax has shown impressive efficacy in patients with chronic lymphocytic leukemia, but its clinical benefits are limited by acquired BCL-2 gene mutations that confer drug resistance. Among acquired mutations, those proximal to BH3 binding motifs (e.g., G101V, D103E, and V156D) have the most significant impact on BCL-2 binding to BH3-only prodeath proteins and BH3 mimetics (e.g., venetoclax). Hence, it is important to identify novel therapeutics that address this emerging unmet need. To this end, we investigated the effect of co-targeting BCL-2 and MDM2-p53 apoptosis pathways in preclinical models of acute lymphoblastic leukemia (ALL) with BCL-2 mutations. We first genetically engineered cell lines that express clinically relevant BCL-2 gene mutations in ALL cell line RS4;11, which shows greater expression of mutants, compared to endogenous wild-type BCL-2 protein. Relative to parental cells, sensitivity to venetoclax and investigational, clinical-stage BCL-2 inhibitor lisaftoclax (APG-2575) in mutant cell lines was reduced 160-fold. Using these BCL-2-inhibitor-resistant cell lines, we assessed the effect of combining lisaftoclax with investigational, clinical-stage MDM2-p53 inhibitor alrizomadlin (APG-115). Alrizomadlin inhibits the MDM2-p53 interaction and activates the prodeath p53 tumor suppressor signaling pathways (Aguilar A et al. J Med Chem 2017). Also potentially consequential was the observation that combining alrizomadlin with lisaftoclax synergistically inhibited proliferation and induced apoptosis in RS4:11 cells carrying G101V, V156D, or D103E mutations. Treatment with this combination also synergistically enhanced antitumor activity in mouse xenograft tumor models derived from RS4:11 cells carrying G101V or V156D mutations. In these animal models, lisaftoclax alone exhibited no or limited activity, with T/C (%; i.e., relative tumor volume of treatment group vs. control) values ranging from 86.40% to 99.15%. In contrast, single-agent alrizomadlin exerted slightly more potent activity, with T/C values ranging from 57.25% to 62.35%. Importantly, the combination of lisaftoclax and alrizomadlin demonstrated synergy, with T/C values ranging from 12.30% to 32.16%. Mechanistically, alrizomadlin likely induced expression of prodeath BCL-2 family proteins BAX, PUMA, and Noxa, which are p53 target genes. Further, lisaftoclax plus alrizomadlin more effectively blocked cell cycle entry into the G2/M phase, resulting in accumulation of sub-G1 apoptotic cells. In summary, our study demonstrates, for the first time, that co-targeting BCL-2 and MDM2-p53 apoptosis pathways overcame resistance to BCL-2 inhibitors conferred by acquired BCL-2 gene mutations, potentially offering a viable strategy to overcome drug resistance and thus providing a rationale for clinical investigation.
Citation Format: Jing Deng, Kaixiang Zhang, Qiuqiong Tang, Xiaojing Huang, Qixin Wang, Na Li, Douglas D. Fang, Dajun Yang, Yifan Zhai. Co-targeting MDM2-p53 and BCL-2 apoptosis pathways overcomes resistance conferred by acquired BCL-2 gene mutations in preclinical models [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 3964.