(T1330-05-31) Anti-Tumor Efficacy, Safety, and Ongoing Pharmacokinetic Evaluation of Nebivolol in a Syngeneic Mouse Model of Triple-Negative Breast Cancer

Purpose: Triple-negative breast cancer (TNBC) is a highly aggressive subtype of breast cancer, characterized by high relapse rates and poor prognosis due to the absence of targeted therapies. While chemotherapy and radiation remain the standard of care, they are often associated with significant long-term side effects and limited efficacy in preventing recurrence, highlighting the urgent need for safer, more effective treatment options. This study investigates nebivolol (NEB), a cardioselective β1-adrenergic blocker with vasodilatory and antioxidant properties, as a novel therapeutic strategy for TNBC. Beyond its cardiovascular indications, NEB has demonstrated potential anti-cancer activities, including inhibition of tumor proliferation and induction of apoptosis.

Methods: Using a 4T1-luc syngeneic TNBC model in 9-week-old female BALB/c mice, mice were randomized into 2 groups, and tumors were established by inoculating 500,000 cells in 50 µL. Treatments with NEB at 10 mg/kg in 20% Captisol and DMSO (9:1, v/v) or vehicle intraperitoneally began 7 days post-inoculation and was administered once per day, five days per week, for three weeks (N = 5 per group). Tumor volume was measured with a caliper three days a week and mice were weighed every day. Mice were sacrificed on day 28 and tumors were harvested.

Results: Assessment of systemic toxicity showed that mean body weight at Day 28 remained stable, with no significant difference between NEB-treated and vehicle groups (22.18 ± 0.66 g in vehicle vs. 22.32 ± 2.60 g NEB group, unpaired t-test, P > 0.05), indicating no observable toxicity at the administered dose. At study endpoint, mean tumor volume was reduced in NEB-treated mice (595.8 ± 134.6 mm³) compared to vehicle controls (1,540.4 ± 536.9 mm³). Further analysis of tumor growth revealed a significant reduction in tumor growth rate by Day 21 (P < 0.05, unpaired t-tests), with NEB at 701.3 ± 133.9 % as compared to the vehicle at 1,070.9 ± 147.9 %, demonstrating NEB’s ability to effectively slow tumor progression (Figure 1). Final tumor weight measurements confirmed these observations, with the vehicle group showing a mean tumor weight of 2,146.7 ± 519.6 mg, while NEB-treated mice exhibited a markedly lower tumor weight of 503.8 ± 86.5 mg, indicating substantial suppression of tumor burden (Figure 2). To further characterize NEB’s pharmacological profile, a robust LC-MS/MS method was developed for precise quantification of NEB in plasma and tumor with LLOQ 0.5 ng/ml. An ongoing pharmacokinetic (PK) study is being conducted to define systemic exposure and local exposure in tumor, and key PK parameters, including C_max, t_max, AUC_0-∞, CL and Vd.

Conclusion: These findings demonstrate that NEB is well-tolerated, capable of significantly suppressing TNBC growth without inducing systemic toxicity. Future studies are required to identify optimal dose of NEB.

Acknowledgements: Award #: HT94252410011