Spatiotemporal orchestration of a ferroptosis-immunotherapy “cycle” via a sequential drug delivery system for antitumor immunity

Interferon-gamma (IFN-γ) and iron can induce ferroptosis; however, distinct target sites restrict their synergistic therapeutic efficacy in simple combination therapy. Herein, two nanoplatforms are constructed with the same polymeric skeleton but different payloads to separately target antigen-presenting cells (APCs) and tumor cells for amplified ferroptosis in immunotherapy. Negatively charged 2′,3′-cyclic GMP-AMP is electronically loaded in pH-responsive nanoparticles (PNPs@cGAMP), which activates the stimulator of interferon gene (STING) pathway in APCs, accompanied by an immune response activation cascade with IFN-γ secretion for tumor ferroptosis. Gossypol is conjugated to the polymer chain by forming a pH-sensitive Schiff base that further coordinates with ferric iron (Fe³⁺) to self-assemble into another size-switchable nanoprodrug (PGNPs@Fe). In the acidic tumor microenvironment, PGNPs@Fe shrinks into Gos@Fe for deeper tumor penetration, which disassembles into Fe³⁺ and gossypol for lipid peroxide generation, resulting in ferroptosis and immunogenic cell death. Compared to multiple administrations of a single nanoformulation, this ferroptosis-immunotherapy "cycle" exhibits notably improved antitumor activity in subcutaneous xenograft and distal metastatic B16F10 tumor models. The mouse survival rate is significantly prolonged after combination with immune checkpoint blockade. This design emphasizes the spatiotemporal orchestration of payloads and provides novel perspectives on intelligent nanotherapeutics combinations for future clinical applications.