As the second most common cause of cancer‐related death worldwide, colorectal cancer (CRC) requires novel therapy strategies. Biodegradable polymers are used as drug carriers for treating CRC and other cancers. However, one of the limitations for the polymeric drug carriers is that they do not directly involve the treating procedure. Herein, to develop a polymeric drug delivery system with additional therapeutic effect from that of the polymer itself, poly(ursolic acid) (PUA) is, for the first time, simply synthesized via polycondensation of ursolic acid (UA), a bioactive ingredient widely distributed in herbal medicine. PUA can self‐assemble into nanoparticles (PUA‐NPs) with a diameter of ≈122 nm and an effective load of ≈10.1%, and deliver drugs, such as paclitaxel (PUA‐NPs@PTX). In vitro studies show that PUA‐NPs@PTX have strong cytotoxicity against colorectal cancer CT26 cells, while in vivo results indicate that these NPs have a prolonged blood circulation time, enhanced tumor accumulation, and significantly improved antitumor efficacy in CT26 tumor‐bearing mice. Furthermore, both in vitro and in vivo results confirm that the PUA‐NPs themselves have therapeutic effects on CT26 cells, without causing obvious toxicity to main organs, such as bledding or necrosis. In summary, such a therapeutic polymer platform provides a new therapeutic strategy for treating cancer.

A novel H2O2-responsive prodrug, POD-PEG NPs, for controlled drug delivery and cancer therapy.

Schematic illustration of the development of long-circulating pH-responsive polysaccharide–DOX prodrug nanoparticles for antitumor applications.