With the knowledge of peptide–HLA complexes, a third approach could utilize a TCR mimic (TCRm) antibody to target ESR1 peptide–HLA complexes, as was shown preclinically in breast cancer models with E75 peptide targeting TCRm antibody (19) and in the setting of leukemia targeting WT1 and PR1 peptides with TCRm antibodies (51, 52). This evidence concerns the gene ESR1 and breast cancer.