Fully human anti-B7-H4 antibody induces lysosome-dependent ferroptosis to reverse primary resistance to PD-1 blockade

Background Although immune checkpoint inhibitors (ICIs) have significantly improved outcomes for patients with certain cancers, their efficacy is largely confined to “hot” tumors characterized by robust infiltration of tumor-specific CD8 + T cells. Conversely, tumors expressing B7-H4 often exhibit an immunologically “cold” tumor microenvironment with poor T cell infiltration, contributing to primary resistance to programmed cell death protein 1 (PD-1) blockade. Methods We evaluated the association between B7-H4 expression and clinical outcomes in ICI-treated patients using public immunotherapy datasets. The role of B7-H4 in mediating resistance to PD-1 therapy was examined in mouse tumor models. A fully human anti-B7-H4 monoclonal antibody (clone A8) was generated via phage display screening from a non-immunized human single-chain variable fragment library. In vitro assays assessed antibody-induced tumor cell death and immune activation, while in vivo efficacy was tested in MC38-mH4 and SKOV3-hH4 tumor models, as well as human colorectal cancer organoids. Statistical analyses included Student’s t-test, one-way analysis of variance, and Kaplan-Meier survival analysis, with p