Nanostructured Lipid Carriers for Oral Bioavailability Enhancement of Exemestane: Formulation Design, In Vitro, Ex Vivo, and In Vivo Studies.

Exemestane (EXE) is a novel oral steroidal aromatase inhibitor approved for the treatment of breast cancer. However, its oral clinical application is limited because of low aqueous solubility and low oral bioavailability. Here, we aim to design and fabricate nanostructured lipid carriers (NLCs) using Precirol® ATO 5 and flaxseed oil as the solid lipid and liquid lipid, respectively. EXE-loaded NLCs were spherical in shape and with a hydrodynamic diameter of 131.3 ± 2.43 nm, polydispersity index 0.205 ± 0.06, and percentage entrapment efficiency 85.6 ± 1.20%. In vitro release study demonstrated a sustained release pattern for 24 h, with relative burst release at the initial time point. Differential scanning calorimetry and powder X-ray diffraction studies showed reduced crystallinity and complete encapsulation of drug within the lipid matrix. Ex vivo gut permeation study and confocal laser scanning microscopy revealed that NLCs comprising a lipid blend and surfactant enhanced intestinal permeability of EXE. Moreover, in vivo pharmacokinetic study on female Wistar rats found to augment 3.9-fold in oral bioavailability of EXE through NLCs compared with EXE suspension. Herein, we depict that loading of EXE into NLCs hold promising approach for the oral delivery of EXE in cancer therapy.