Mitochondria-Targeted Prodrug Nanoassemblies Elicit Antitumor Immunity via Mitophagy-Boosted Ferroptosis in Triple-Negative Breast Cancer.

Ferroptosis, an immunogenic iron-dependent cell death driven by lipid peroxidation, holds promise for treating triple-negative breast cancer (TNBC). However, its efficacy is severely compromised by restricted iron availability and the potent GPX4/GSH defense system. Herein, we developed a mitochondria-targeted prodrug by conjugating sulfasalazine (SAS) to triphenylphosphonium (TPP) via a disulfide-containing linker, which self-assembles into carrier-free nanoassemblies (ASSP). After cellular internalization and lysosomal release, SAS-SS-TPP accumulates in mitochondria, where thiol-disulfide exchange depletes GSH, orchestrates GPX4 antiferroptosis system failure, and liberates SAS. The released SAS elicits PINK1-dependent mitophagy, unleashing mitochondrial iron stores, amplifying the labile iron pool, and driving Fenton-reaction-mediated lipid peroxidation. By synergizing "mitophagy-fueled iron surge" and "GPX4/GSH defense disruption", ASSP evokes potent ferroptosis and antitumor immunity, dramatically suppressing TNBC tumor growth and metastasis. This work presents a nanotherapeutic strategy that leverages mitophagy to potentiate ferroptosis and immunotherapy, offering a promising approach for cancer therapy.