Small-Molecule Ferritin Degrader as a Pyroptosis Inducer.

Exploring the response of malignant cells to intracellular metabolic stress is critical for understanding pathologic processes and developing anticancer therapies. Herein, we developed ferritin-targeting proteolysis targeting chimeras (PROTACs) to establish the iron excess stress inside cancer cells and investigated subsequent cellular behaviors. We conjugated oleic acid that binds to the ferritin dimer to the ligand of von Hippel-Lindau (VHL) E3 ligase through an alkyl linker. The screened chimera, DeFer-2, degraded ferritin and then rapidly elevated the free iron content, thereby initiating the caspase 3-GSDME-mediated pyroptosis in cancer cells rather than typical ferroptosis that is always associated with iron ion overload. According to its structural and physicochemical characteristics, DeFer-2 was loaded into a tailored albumin-based nano-formulation, which substantially inhibited tumor growth and prolonged the survival time of mice bearing B16F10 subcutaneous tumors with negligible adverse effects. This study developed a ferritin-targeting PROTAC for iron overload stress, revealed iron metabolic dysregulation-mediated pyroptosis, and provided a PROTAC-based pyroptosis inducer for anticancer treatment.