Abstract 515: Repurposing nebivolol with dasatinib and CPI-613: A synergistic strategy to combat triple-negative breast cancer

Abstract Triple-negative breast cancer (TNBC) is a relentless and aggressive disease, posing significant challenges due to its high recurrence rates and poor prognosis. Existing treatments, such as chemotherapy and radiation, often cause long-term side effects, and over half of patients experience relapse within a few years of diagnosis. This study investigates the novel approach of repurposing nebivolol (NEB), a beta-blocker with a well-established safety profile, in combination with dasatinib (DAS) or Devimistat (CPI) to potentially enhance anti-tumor efficacy in TNBC. Dasatinib targets multiple kinases involved in cancer cell proliferation and metastasis, while CPI-613 induces metabolic stress and apoptosis in cancer cells. We evaluated the cytotoxic effects of NEB, DAS, and CPI, both individually and in combination, across TNBC cell lines (MDA-MB-231, 4T1, BT-549) using MTT assays. IC50 values were determined, and optimal drug ratios were identified using the Chou-Talalay method and 3D surface plots. Drug ranges were selected below and above determined IC50 values and used in a two-system matrix design. Combination Index (CI) plots were generated to assess synergistic interactions. Additionally, a migration assay was performed to evaluate the effects of the combinations on cell migration. NEB, DAS, and CPI individually reduced cell viability with IC50 values of 6.3 µM, 76.4 nM, and 71.1 µM in MDA-MB-231 cells; 12.8 µM, 91.2 nM, and 41.4 µM in 4T1 cells; and 2.7 µM, 33.2 nM, and 24.8 µM in BT-549 cells. The NEB-DAS combination exhibited significant synergy in BT-549 cells, with a CI of 0.35 at 800 nM NEB and 3 nM DAS (p < 0.002 compared to each drug alone). Similarly, NEB-CPI demonstrated additive effects in BT-549 cells, with a CI of 1.0 at 800 nM NEB and 20 µM CPI (p < 0.003 compared to each drug alone). In MDA-MB-231 cells, the NEB (3 µM)-DAS (50 nM) combination showed significant synergy only with NEB (p = 0.0007, CI 0.85), while the NEB (3 µM) -CPI (15 µM) combination was synergistic compared to either drug alone (p < 0.001, CI 0.49). For 4T1 cells, NEB (6 µM) and CPI (20 µM) was significantly more potent compared to each drug alone (p < 0.0001, CI 0.32), and NEB (3 µM) and DAS (30 nM) was more potent compared to each drug alone (p < 0.004). Most combinations using Chou-Talalay had CI values predominantly below 1, confirming synergy. The migration assay indicated that NEB and CPI significantly reduced migration in MB-231 cells compared to either drug alone (p < 0.03). Interestingly, the NEB-DAS combination did not show a significant difference compared to DAS alone (p=0.17) but was more effective than NEB alone (p = 0.0009). These findings highlight the potential of NEB in combination with DAS or CPI as a promising therapeutic strategy for TNBC. Ongoing in vivo studies using a TNBC mouse model aim to validate these findings and further explore the clinical potential of these combinations to improve TNBC patient outcomes. Citation Format: Mikayla Skillman, Airong Li, Fatima Dagher, Diana Chow, Meghana Trivedi. Repurposing nebivolol with dasatinib and CPI-613: A synergistic strategy to combat triple-negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 515.