Tumor‐Targeting Co‐Delivery of T‐Cell Antigen and Camptothecin Guided by Cascade‐Responsive Peptide Self‐Assembly to Reshape Tumor Antigenicity for Cancer Immunotherapy

Antigen presentation deficiency restricted by class I major histocompatibility complex (MHC-I) causes low antigenicity and antigen escape in tumors, thereby limiting T-cell immunotherapy outcomes. Here, a combined tumor immunotherapy is developed, in which tumors can present exogenous non-tumor antigens, and adoptively transferred CD8⁺ T cells specific for these antigens are re-targeted to attack tumors. The approach leverages a cascade-responsive peptide self-assembly to co-deliver suitable antigens and the chemotherapeutic drug camptothecin (CPT) to tumors. As a proof-of-concept, to re-target ovalbumin (OVA)-specific OT-I CD8⁺ T cells against tumors, PSA (Nap-GFFpYE-ss-Ag) and CPSA (CPT-GFFpYE-ss-Ag) are constructed, containing an OVA-derived epitope OVA_257-264 and/or CPT. The design enables the release of a unique N-terminal extended OVA_257-264 and CPT into the cytosol. As a result, the extended antigen is efficiently presented on the tumor surface by MHC-I, and CPT further enhances this presentation. When combined with adoptively transferred OT-I CD8⁺ T cells, the approach effectively facilitates CD8⁺ T cell infiltration and tumor inhibition. Additionally, CPSA treatment sensitizes immune responses to programmed cell death-ligand 1 (PD-L1) blockade, allowing the approach to synergize with an anti-PD-L1 antibody for improved tumor eradication.