Targeting Stage-Specific Embryonic Antigen 4 (SSEA-4) in Triple Negative Breast Cancer by CAR T Cells Results in Unexpected on Target/off Tumor Toxicities in Mice.

Due to the paucity of targetable antigens, triple-negative breast cancer (TNBC) remains a challenging subtype of breast cancer to treat. In this study, we developed and evaluated a chimeric antigen receptor (CAR) T cell-based treatment modality for TNBC by targeting stage-specific embryonic antigen 4 (SSEA-4), a glycolipid whose overexpression in TNBC has been correlated with metastasis and chemoresistance. To delineate the optimal CAR configuration, a panel of SSEA-4-specific CARs containing alternative extracellular spacer domains was constructed.