Esterase‐Responsive Mitochondria‐Targeted Hydropersulfide Donors Mitigate Doxorubicin Cardiotoxicity While Preserving Anticancer Activity

Therapeutic agents that protect the heart from doxorubicin (DOX) toxicity without reducing its anticancer efficacy remain a critical unmet need. We report esterase-activated hydropersulfide (RSSH) donors, alkyl sulfenyl thiocarbonate (AST-2), and acetoxy perthiocarbamate (APT-1), together with their mitochondria-targeted analogs, AST-2-TPP and APT-1-TPP, which bear a triphenylphosphonium (TPP⁺) moiety. These compounds release RSSH upon esterase activation with tunable half-lives (20-125 min in PBS, pH 7.4). LC-MS/MS analysis revealed that APT-1 elevates hydropersulfide levels in the cytosol of H9c2 cardiomyoblasts, whereas its mitochondrial analog, APT-1-TPP, increases levels in mitochondria. All donors attenuated DOX-induced toxicity in H9c2 cells, but in cancer cell lines (HepG2, MDA-MB-468, MCF-7), APT-1 did not blunt DOX cytotoxicity and APT-1-TPP synergistically enhanced its activity. Mechanistic studies revealed that both APT-1 and APT-1-TPP rescue DOX-induced mitochondrial membrane depolarization and ATP depletion in H9c2 cells but not in HepG2 cells. Further characterization indicated that cancer cells exhibit higher basal sulfane sulfur levels and mitochondrial membrane potentials compared to H9c2 cells, suggesting that divergent redox environments may underlie these contrasting effects. Collectively, these findings demonstrate that redox heterogeneity between cardiac and cancer cells can be exploited to develop cardioprotective interventions that preserve or enhance DOX's anticancer efficacy.