Design, Synthesis, and Biological Evaluation of New Cathepsin B-Sensitive Camptothecin Nanoparticles Equipped with a Novel Multifuctional Linker

Traditional antitumor drugs such as camptothecin and paclitaxel derivatives are widely used in cancer chemotherapy. However, the major defects of those agents include severe toxicity and poor water solubility. With these in mind, a novel multifunctional linker was designed and two Cathepsin B (CTB) sensitive CPT conjugates (9a and 9b) were synthesized. Through click chemistry, additional functional group mPEG₂₀₀₀ can be easily introduced into these conjugates. The introduction of mPEG₂₀₀₀ fragment resulted in the formation of nanoparticles 1a and 1b (average particle sizes were 216.9 and 257.9 nm, respectively) with significantly increased water solubility (more than 19 000-fold). The release of therapeutic drug SN-38 in the presence of CTB was confirmed by HPLC and prodrug 1a showed potent in vitro cytotoxicity against all tested cell lines. Impressively, compared with irinotecan, CTB sensitive prodrug 1a displayed similar in vivo efficacy with remarkable decreased in vivo toxicity.