Abstract 678: Experimental therapy of triple negative breast cancer with next-generation of MDM2 inhibitors

Abstract Patients with triple-negative breast cancer (TNBC) typically experience minimal benefits from the existing hormonal or trastuzumab-based therapies, necessitating reliance on chemotherapy as the predominant treatment approach, which, unfortunately, is limited by insufficient efficacy, significant side effects, and the development of drug resistance. These issues highlight an urgent demand for the discovery and development of more effective and safer therapeutics for TNBC. Overexpression and amplification of the MDM2 oncogene frequently occur in TNBC, which is associated with invasive and high-grade/late-stage tumors, metastasis, and recurrence, and is an independent negative prognostic factor for TNBC patients. Extensive studies have indicated that MDM2 represents a novel molecular target for TNBC. Thus far, multiple strategies aiming at MDM2 inhibition have not succeeded in Phase II-III clinical trials, largely due to factors like inadequate efficacy, significant drug toxicity, and emergence of resistance. In addition, TNBC tumors commonly harbor mutant p53, and the existing MDM2 inhibitors that block p53-MDM2 binding and depend on wild-type p53 expression in the tumor to exert anticancer effects would have little or no clinical responses or even induce resistant clones by increasing MDM2 expression and its oncogenic activity. Therefore, there is a need for developing new-generation MDM2 inhibitors that are p53-independent. We recently discovered a novel class of MDM2 degraders, representing a paradigm shift in the strategy of targeting MDM2. One of these analogs, WW68, was identified as a potent and selective MDM2 inhibitor. Its in vitro and in vivo anti-breast cancer activities and underlying mechanisms of action were evaluated in breast cancer cell lines with various p53 backgrounds. Our results demonstrate that WW68 effectively induces MDM2 protein degradation. It selectively inhibits breast cancer cell growth, decreases cell proliferation, and induces G2/M phase arrest and apoptosis in breast cancer cells, regardless of p53 status. Notably, in clinically relevant TNBC PDX models, WW68 inhibited MDM2 and suppressed tumor growth without causing host toxicity. In conclusion, WW68 represents a new class of MDM2 inhibitor that exerts its anticancer activity through directly down-regulating MDM2, and may be developed as a novel anti-TNBC therapeutic agent. (Supported by NIH R01CA214019 and R01CA240447; and DoD W81XWH2010011) Citation Format: Wei Wang, Hao Chen, Yang Xie, Sayantap Datta, Wei Li, Ruiwen Zhang. Experimental therapy of triple negative breast cancer with next-generation of MDM2 inhibitors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 678.