Sustained and cancer cell targeted cytosolic delivery of Onconase results in potent antitumor effects

The unfavorable pharmacokinetics and low tumor specificity hampered the potential clinical utility of Onconase, a promising modality in anticancer treatment with unique targets and novel mechanism of action. In this study, a modular and multi-stage drug delivery system (DDS) that can break down organ (renal accumulation), cellular (cancer cell specific uptake) and sub-cellular (endosomal escape) level barriers encountered by Onconase during its long journey from injection site to the cytoplasm of cancer cell was designed. Human serum albumin fusion extended the half-life of Onconase and significantly decreased its kidney accumulation. Epithelial cell adhesion molecular (EpCAM) specific antibody fragment appending enhanced binding and internalization of Onconase toward EpCAM positive cancer cell and increased its tumor accumulation and retention. Tethering Onconase to its carrier by cleavable disulfide linker prompted endosomal escape and restored its cytotoxicity. In vivo antitumor efficacy assay in human tumor xenograft model revealed that only when the entire organ, cellular and sub-cellular level barriers had been broken down, will Onconase turn into a potent antitumor agent. (C) 2012 Elsevier B.V. All rights reserved.