β-cyclodextrin-enzalutamide self-assembly complexes for prostate cancer therapy
Introduction
Enzalutamide (Enza, Xtandi®, AR inhibitor) is a clinically proven, second generation non-steroidal anti-androgen oral medication for the treatment of castration-resistant prostate cancer (CRPC). Enzalutamide helps to reduce 61% of disease progression and extend overall survival. However, this oral medication not only exhibits limited bioavailability but displays systemic side effects at high doses. Thus, new approaches that can enhance the tumor delivery while reducing systemic side effects are urgently needed. In this work, we developed and characterized β-cyclodextrin-enzalutamide (Enz-β-CD) self-assembly complexes for improved therapeutic benefit for CRPC treatment.
Methods
Enz-loaded self-assembly complexes (enz-β-CD) formulation was developed using solvent evaporatin method utilizing β-cyclodextrin (β-CD) as a solubilizer, which has a well-documented safety profile and FDA approval. The inclusion complex formation has been confirmed from dynamic light scattering, Fourier-transformed infrared spectroscopy, scanning electron microscopy, X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, and nuclear magnetic resonance spectral analysis, respectively. The cellular internalization capacity of this formulation was evaluated using flow cytometry and fluorescent microscopy methods. The therapeutic efficacy of enz-β-CD self-assembly complexes was evaluated using clinically relevant PC cell lines (C4-2B, and 22-RV1) through cell proliferation and colony formation assays. CaCo2 cell permeability assay was performed to evaluate the suitability of enz-β-CD complexes for oral dosing.
Results
Our characterization studies demonstrated that enzalutamide was entrapped in the inner cavity of β-CD and the inclusion complex formed in an amorphous state. The particle size of the inclusion complex was found less than 100 nm, while zeta potential and PDI were −7.6 mV and 0.2, respectively. Moreover, inclusion complexes have the characteristic structure of an adduct, in which one enzalutamide guest molecule, is enclosed to the host molecule i.e. β-CD. Interestingly the guest molecule is situated in the cavity of the host without significantly affecting the host framework structure. The flow cytometry and fluorescence microscopy analysis confirmed a dose-dependant cellular uptake of enz-β-CD self-assembly complexes in PC cells. The CCK-8 assay confirms that enz-β-CD self-assembly complexes exhibited anticancer effects in C42B and 22RV1 cells, like bare enzalutamide. A similar clonogenic potential was noticed with the enz-β-CD self-assembly complexes. The permeability assays demonstrated the drug flux that would allow for intestinal permeability.
Conclusion
Taken together, our results demonstrate that enz-β-CD self-assembly complexes exhibit superior anti-cancer potential than free enzalutamide. Thus, this formulation may serve as a novel therapeutic modality for the management of CRPC therapy.