Degradable water-soluble polymer prodrugs for subcutaneous delivery of irritant anticancer drugs

Chemotherapy is primarily administered intravenously (IV), but this route poses significant challenges (e.g., high costs, patient discomfort, logistical difficulties, side effects such as infections from catheter use). Although oral and subcutaneous (SC) routes are preferred for their convenience and have the potential for better patient comfort and cost reduction, oral chemotherapy faces issues like poor bioavailability and adherence, while SC delivery is unsuitable for irritant or vesicant drugs due to local toxicity. To overcome these limitations, the polymer prodrug strategy has been explored, where drugs are linked to a polymer, reducing toxicity and enhancing drug delivery. Recent work has focused on creating water-soluble polymer prodrugs for SC delivery of paclitaxel (Ptx), a hydrophobic and vesicant drug, which was successfully conjugated to polyacrylamide (PAAm), a very hydrophilic biocompatible polymer, resulting in safer SC injection and enhanced therapeutic efficacy in tumor-bearing mice. However, this strategy's potential depends on adapting it to other vesicant anticancer drugs. Making the polymer degradable for facilitated excretion would also be a key improvement. In this work, this approach has been successfully extended to gemcitabine (Gem), a widely used but irritant anticancer drug, and to a degradable PAAm-based promoiety, having cleavable ester groups in the main chain. The resulting Gem-based prodrugs featured upper critical solution temperature to ensure complete solubility at the temperature of the SC tissue, sustained Gem release, significant degradation under physiological conditions, improved systemic toxicity and absence of local toxicity compared to free Gem. Remarkably, Gem-PAAm polymer prodrugs exhibited significant anticancer efficacy in mice bearing Mia Pa-Ca 2 tumors, outperforming Gemzar®, the commercial formulation of Gem. These advances suggest the potential of these hydrophilic polymer prodrugs to transform SC chemotherapy, enabling the use of a broader range of anticancer drugs while reducing side effects and improving patient outcomes.