TPS11569 Background: ADP-A2M4 specific peptide enhanced affinity receptor (SPEAR) T-cells are genetically engineered to target MAGE-A4+ tumors in the context of HLA-A*02. MAGE-A4 has been described as having high expression in synovial sarcoma (SS) and myxoid/round cell liposarcoma (MRCLS) [1, 2]. This Phase 2 trial was initiated based on the favorable benefit:risk profile of ADP-A2M4 observed in a Phase 1 trial (NCT03132922) of ADP-A2M4 which demonstrated compelling clinical responses in patients with SS. Methods: This Phase 2, open-label trial (SPEARHEAD-1; NCT04044768) is designed to evaluate the efficacy, safety and tolerability of ADP-A2M4 in patients with advanced/metastatic SS or MRCLS who are HLA-A*02 positive and whose tumors express the MAGE-A4 protein. Enrolled patients are to undergo apheresis, and their isolated T-cells are then transduced with the MAGE-A4c1032 TCR, and expanded. Prior to ADP-A2M4 infusion, patients are to receive lymphodepleting chemotherapy consisting of fludarabine (30 mg/m2/day x 4 days) and cyclophosphamide (600 mg/m2/day x 3 days). Patients are to receive 1 – 10 × 109 transduced T-cells. An independent Data Safety Monitoring Board will review ongoing safety and benefit:risk during the interventional phase of the study. Disease will be assessed by independent review per RECIST v1.1 by CT/MRI at weeks 4, 8, 12, 16, 24, and every 2 months thereafter until confirmed disease progression. As of 24 Jan 2020, there were 17 clinical sites open in the US, one in Canada, and two in Spain.