Benchmarking of pH-responsive mixed micelles for repurposed breast cancer therapy of ibrutinib with molecular modeling and pharmacokinetic insights

Abstract

Ibrutinib (IBT) is a well-known Bruton's tyrosine kinase (BTK) inhibitor molecule approved for the treatment of B-cell malignancies. The off-target potential of IBT opens up the door for its repurposing against different solid tumors including breast cancer (BC). However, clinical success of the drug was found to be compromised due to poor bioavailability and toxicity issues associated with its existing commercial dosage forms. Therefore, in the present study, a pH-sensitive polymeric mixed micellar (PMM) system was fabricated for intravenous (i.v.) delivery of IBT. The generation of PMMs using vitamin E-TPGS and Solutol® HS 15 was assured through the in silico binding affinity of the drug, and freeze-drying assisted development was optimized by applying a 3-level, 3-factor Box–Behnken Design (BBD). The optimized formulation exhibited a smooth spherical morphology with an average particle size of 103.19 ± 14.92 nm, a PDI of 0.387 ± 0.03, and a zeta-potential of −13.97 ± 1.51 mV. Furthermore, it provides an encapsulation efficiency of 97.73 ± 2.40%, a burst release of 57.86 ± 2.22% after 2 h at pH 6.5, and 60 days of stability at 5 ± 3 °C. The solid form of IBT-PMMs was characterized through FT-IR, DSC, PXRD, and SEM. The developed IBT-PMMs showed excellent efficacy for BC cell lines with a reduction in IC₅₀ of around 15-fold in MCF-7 and 10-fold in MDA MB-231 compared to free IBT. Apart from that, the developed micellar system exhibited a significant cellular accumulation, ROS dependent-MMP mediated apoptosis, and inhibition of cell migration in both cell lines. In western blot, relative expression of Bax (apoptic protein)/Bcl-2(anti-apoptic protein) was also found to be elevated. The anti-angiogenic potential of the formulation was confirmed through a reduction in vessel formation in an ex vivo chick embryo assay. In addition, the drug-loaded PMMs were also found to be hemocompatible, safe for i.v. administration with an LD₅₀ of 25 mg kg⁻¹ in female BALB/c mice and long-acting with a high plasma half-life (t_1/2) of 18.76 ± 3.83 h. In short, findings of the study suggest that the developed PMMs serve as a proficient carrier system in augmenting the anti-cancer effect of IBT against BC treatment with an improved pharmacokinetic profile.