MAGEA3 and neoplasm: Furthermore, antigen heterogeneity in solid tumors complicates the efficacy of CAR-T cells, as tumor-associated antigens (TAAs) are also expressed in normal cells in other regions, causing tumor off-target effects [91]. This is particularly perilous in the brain, where off-tumor targeting of normal cells can result in severe toxicity, as observed with MAGE-A3 TCR-engineered T cells [92].