Pharmacokinetic and biodistribution evaluation of nebivolol and dasatinib in the 4T1 triple-negative breast cancer model: Implications for drug-drug interaction

Background: In our recent in-vitro study, nebivolol (NEB) and dasatinib (DAS) synergistically inhibited the growth of 4T1 cell line, which is a murine mammary carcinoma cell line used to study triple-negative breast cancer (TNBC). However, the in vivo disposition and potential for drug-drug interactions (DDI) are not well defined. This study aimed to characterize the pharmacokinetics (PK) and biodistribution of NEB and DAS in 4T1 tumor-bearing mice and evaluate whether co-administration modifies plasma or tissue concentrations. Methods: Female BALB/c mice (7-8 weeks) were implanted with 4T1 cells orthotopically and treated with NEB (n=5), DAS (n=5), or NEB+DAS (n=6). The regimen was NEB 10 mg/kg once a day and DAS 20 mg/kg twice a day, 5 days/week for 3 weeks. After the last dose, blood was collected at multiple time points and tissues (tumor, liver, kidney, lung, spleen, heart, pancreas, and brain) were harvested at the end. Drug concentration was quantified using a validated LC-MS/MS method. PK parameters were generated by Phoenix (8.5.1) and GraphPad 10 was used to generate the PK profile and statistical analysis. Results: Co-administration significantly increased NEB exposure in blood, of which the area under curve (AUC normalized by dose) was 229.45±150.98 hr*ng/mL/(mg/kg), compared to 44.51±10.21 hr*ng/mL/(mg/kg) in the NEB alone group (p<0.05). The NEB clearance was decreased from 24.06±7.13 to 5.59±2.88 L/(kg*hr) (p<0.05). DAS concentration and parameters were not changed significantly in combination group vs. DAS alone group. Biodistribution analysis modified tissue partitioning in the combination group. NEB concentrations in all tissues were higher in combination group than NEB alone group (p>0.05 due to the large variance). Tissue-to-blood (T/B) ratios interpreted the tissue uptake of drugs. T/B ratios of both drugs in tumor, liver, lung, spleen, kidney and pancreas were over 1, indicating preferential tissue accumulation. Even though the T/B ratios in tumor were higher in NEB (32.27±61.87) and DAS (99.45±179.53) alone groups than the combination group (2.53±2.25, 3.73±2.41, respectively), no significant difference was observed due to the large variance, suggesting that co-administration can influence intratumoral delivery. The ratio (T/B) of DAS in the kidney was significantly elevated under combination dosing compared with DAS alone, which indicated more DAS accumulation in combination treatment. Conclusions: Combination dosing led to a higher exposure of NEB in blood with a lower clearance, and an increased renal distribution of DAS. Distribution shifts indicated a drug-drug interaction. These findings provide a foundational framework for mechanistic PK/PD modeling and support further investigation of NEB+DAS combination for TNBC treatment.