Checkpoint blockade
immunotherapy has broad application prospects in the clinical treatment of malignant
tumors. However, the low response rate of the checkpoint blockade is due to low
tumor immunogenicity and immunosuppression within the tumor microenvironment. Herein, the authors design an amphiphilic bifunctional PD-1/PD-L1
peptide antagonist PCP, and co-deliver
doxorubicin (DOX) and R848 through co-assembly of a multi-agent
prodrug (PCP@R848/DOX), which can be specifically cleaved by fibroblast activation
protein-α (FAP-α) in the
tumor stroma. Upon reaching the
tumor tissue, the PCP@R848/DOX
prodrug nanostructure is disassembled by FAP-α. The localized release of DOX and R848 triggers immunogenic cell death (ICD) and reprograms tumor-associated macrophages (TAMs) to elicit antitumor immunity. Furthermore, sustained release of PD-1 or PD-L1
peptide antagonists mediates the PD-L1 pathway blockade for further propagated activation of cytotoxic T lymphocytes. Notably, a tumor microenvironment activatable
prodrug nanoparticle is presented for triple-modality
cancer therapy that functions by simultaneously activating ICD and altering the phenotype of TAMs when combined with PD-1 blockade
therapy, which efficiently elicits a strong systemic antitumor immune response. This strategy may emerge as a new paradigm in the treatment of
cancer by combination
immunotherapy.