Patients with synovial sarcoma were heavily pre-treated; all received prior ifosfamide, 16/20 (80%) received prior anthracycline, and in the 100–300 μg cohorts, 6/9 (66%) received prior MAGE-A4 (n = 3) or NY-ESO-1 (n = 3) TCR-T treatment. Here, MAGEA4 is linked to synovial sarcoma.