Long-circulating enzyme-activated HSP90–targeted camptothecin derivatives

Drug delivery technology has emerged as an effective strategy to enhance the anti-tumor potential of camptothecins. In this study, we constructed an enzyme-activated targeted drug release system employing a stable valine–alanine linker in combination with a highly cytotoxic camptothecin derivative, AZ′0132. The prodrug, named HC07, was successfully delivered to the tumor site via eHSP90, where it underwent specific cleavage, thereby enhancing its therapeutic window and reducing ocular toxicity. In order to further improve its metabolic properties, we innovatively combined HC07 with plasma endogenous albumin to construct albumin-binding prodrugs HC08 and HC09 for the first time. These prodrugs demonstrated prolonged circulation times in vivo and significantly improved tumor selectivity and anti-tumor efficacy. This work presents a promising eHSP90-based long-circulating drug delivery system, providing new avenues for the design of future anti-cancer drugs.