Abstract 4605: Brigatinib based degraders as a therapeutic strategy for triple negative breast cancer

Abstract Background: Treatment of patients with triple-negative breast cancer (TNBC) has been challenging due to the absence of well-defined molecular targets and high invasive and proliferative capabilities of these cells. Therefore, new therapeutic strategies for treatment of TNBC are urgently needed. Protease-targeted chimeras (PROTACs) are a class of emerging therapeutic inhibitors that recruit the ubiquitin E3 ligase to selectively degrade proteins. PROTAC degrader technology has shown robust results in inhibiting TNBC progression. Methods: RNA sequencing and analysis were done. Samples were submitted to PamGene for kinome profiling and analysis. Western blotting was performed to visualize protein expression. MTT assays were carried out to evaluate cell viability. Colony formation assays assessed changes in clonogenicity. Data were analyzed using Graph Pad Prism Software 8 using one-way ANOVA and the unpaired two-tailed Students t-test. All data were evaluated in triplicate against control cells. Results: Analysis of RNA sequencing in LM2-4175 TNBC cells treated with our target degrader showed increased genes associated with apoptosis and a decrease in genes associated with cell cycle checkpoint, DNA replication, and regulation of P53 signal transduction pathways. Kinase activity profiling of MDAMB231-LM2-4175 TNBC cells treated with our degrader showed a significant reduction in serine/threonine kinases (STKs) associated with Mitogen-activated protein kinase (MAPK) and cyclin-dependent kinase (CDK) families. In addition, we noticed a significant decrease in protein tyrosine kinases (PTK) associated with ephrin receptor proteins. Western blot analysis confirmed targeted degradation of Focal Adhesion Kinase in multiple TNBC cell lines (MDAMB-231-LM2-4175, MDAMB-468, and 4QXTB). MTT analysis of cell proliferation showed our degrader selectively targeted MDAMB231, MDAMB231-LM2-4175, MDAMB-468, and 4QXTB (Primary)TNBC cells over our non-neoplastic cell line, MCF10A, in a nanomolar range. Colony formation assays also showed our degrader was able to reduce clonogenicity in TNBC cell lines MDAMB231-LM2-4175, MDAMB-468, and 4QXTB. Conclusions: Breast cancer is a diverse and intricate disease which is known to have unique inter- and intra-tumoral characteristics. We have identified a candidate PROTAC which can selectively target TNBC cells while minimally affecting normal bystander cells at nanomolar ranges in vitro. The further development of this degrader can serve as the fundamental basis for a novel therapeutic treatment in TNBC. Citation Format: Manu Khosla, Suresh Alahari, Guangdi Wang. Brigatinib based degraders as a therapeutic strategy for triple negative breast cancer abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 4605.