Mitochondria-targeting artesunate-rhein conjugates: Linker-modulated cell-permeability, heme-affinity and anticancer activity

Heme, abundant in the mitochondria of cancer cells, is a key target for the anticancer activity of artemisinin (ART). Current strategies to enhance the anticancer activity of ART focus solely on its delivery to heme-enriched subcellular localizations while overlooking the decisive effects of ART-heme interactions. Here, we propose an ingenious strategy that synergizes mitochondria-targeted drug delivery and linker-mediated drug conformation modulation, thereby significantly enhancing the anticancer activity of ART. By strategically conjugating artemisinin (ART) with the mitochondria-targeting rhein (R) using different linkers, we aimed to precisely adjust the conformation of the conjugates. Comprehensive computational analysis revealed that the conjugate with the optimal linker length (C₄) displayed a favorable conformation that facilitated cell permeability and exhibited the highest binding affinity to heme and Fe ions. Moreover, it exhibited superior tumor suppression capabilities both in vitro and in vivo, overcoming the uncertainty of in vivo application caused by the rapid clearance of the conventional mitochondria-targeted cation TPP⁺, and even inducing immunogenic cell death associated with immunotherapy. This novel strategy opens up a new avenue for the development of drug conjugate systems.