Enhanced in vitro cytotoxicity and anti-tumor activity of vorinostat-loaded pluronic micelles with prolonged release and reduced hepatic and renal toxicities.

Vorinostat is the first histone deacetylase inhibitor approved by US FDA for use in cancer therapy. However, its limited aqueous solubility, low permeability, and suboptimal pharmacokinetics hinder its delivery. Thus, in this study, micelles of vorinostat with each of pluronic F68 (PF68) and pluronic F127 (PF127) were developed and optimized based on drug loading and entrapment. The optimized micelles were characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometry (XRD), differential scanning calorimetry (DSC), zeta analyzer, and electron transmission microscopy. Their in vitro release, stability, in vitro cytotoxicity against HepG2, Caco-2, and MCF-7 cell lines, and finally, in vivo antitumor activity in mice bearing Ehrlich Ascites Carcinoma (EAC) were assessed. The highest entrapment efficiency was 99.09±2.16% and 94.19±2.37% for micelles of 1:50 drug to polymer ratio with each of PF127 and PF68, respectively. These micelles were nearly spherical with nanoscopic mean diameters of 72.61±10.66nm for PF68 and 91.88±10.70nm for PF127 with narrow size distribution. The micelles provided prolonged release at phosphate buffer saline pH7.4 up to 24h for PF68 and 72h for PF127. Potentiation of in vitro cytotoxicity of vorinostat was more pronounced with PF127 micelles particularly against MCF-7 cells. Compared with free vorinostat, the micelles with PF127 were more effective in inhibiting tumor growth as well as exhibiting significantly (p<0.05) diminished hepatic and renal toxicities. In conclusion, 1:50 vorinostat-PF127 micelles may facilitate i.v. formulations and can be suggested as a promising stable and safe nanoparticulate delivery system with prolonged release and potentiated cytotoxicity.