Bypassing P-glycoprotein mediated efflux of afatinib by cyclodextrin complexation - Evaluation of intestinal...

A cyclodextrin complex of afatinib, a FDA-approved pan-ErbB inhibitor and known P-gp substrate, was developed to enhance its bio-activity while also reducing p-glycoprotein (P-gp) efflux, thereby improving its transport across the intestinal membrane. A sulfobutyl ether derivative of β-cyclodextrin (SBE-β-CD, pharmaceutical grade) was selected based on preliminary phase solubility studies and molecular modeling to prepare an afatinib-cyclodextrin inclusion complex. Various solid-state characterization studies were performed to confirm complex formation and to evaluate its physicochemical properties. Results showed that complexation with SBE-β-CD enhanced afatinib's stability in PBS (pH 7.4), as well as in simulated gastric (pH 2.0) and intestinal fluids (pH 6.5). In addition, the cytotoxicity (reduced IC₅₀ after complexation across multiple cancer cell lines with varied P-gp expression) and tumor volume retraction ability (in-vitro 3D-spheroids of P-gp overexpressing cell lines) of afatinib were both enhanced through cyclodextrin complexation. CD complexation effect of afatinib on P-gp efflux as well as transport was assessed using in-vitro permeability studies (Caco-2 and EpiIntestinal^® tissue models). Results demonstrated that cyclodextrin complexation significantly increased the transport of afatinib across the gut membrane while also reducing its efflux ratio, indicating its vital role in P-gp efflux modulation.