Improved epirubicin delivery selectivity to bladder cancer achieved by functionalized hydroxyethyl starch-based prodrug

Bladder instillation of chemo-therapeutic agents is common for bladder cancer (BC) treatment, however, due to the poor tissue selectivity of chemotherapeutic agents, this method suffers from bladder irritation or even chemical cystitis. Here, we designed a hydroxyethyl starch-based prodrug for epirubicin (EPI) using a pH-sensitive hydrazone linker and folate as the active targeting moiety (FA-HES-hyd-EPI) to achieve delivery selectivity. Prodrug micelles decorated with FA (FA-m), with diameter of 203.6 ± 7.1 nm and EPI loading of 5.80 ± 0.129 %, were prepared by self-assemble method. FA-m was found with improved cellular uptake and stronger cytotoxicity over EPI. An orthotopic BC model was established with FA receptor over-expression, and FA-m showed significantly higher accumulation at tissue and cell levels compared with the FA-free counterpart. Besides, the systemic exposure of FA-m was significantly lower than EPI (AUC 0-t : 28.11 ± 7.23 ng/mL/h versus 11.60 ± 4.27 ng/mL/h). More importantly, FA-m showed stronger in vivo tumor growth inhibition with average tumor weight of 0.26 ± 0.21 mg (EPI group: 1.695 ± 0.62 mg), and better safety according to body weight and HE staining data. Overall, the combination of active targeting and pH responsive prodrug strategies was a feasible way to achieve selective EPI delivery to BC via instillation that improved both therapeutic effect and safety.