Background: MAGE-A4 is a cancer/testis antigen with expression in many solid tumors promoting cell growth by preventing cell cycle arrest and apoptosis. This study (NCT03132922) evaluated safety and efficacy of SPEAR T-cells directed against the MAGE-A4 peptide expressed in 9 tumor types. Methods: This Phase I dose-escalation, expansion trial evaluated patients (pt) who were HLA-A*02 positive with advanced cancers that expressed the MAGE-A4 protein. Autologous T-cells from eligible patients were isolated, transduced with a lentiviral vector containing the MAGE-A4^c1032 TCR, and expanded. Prior to ADP-A2M4 infusion, pts received a lymphodepletion regimen of cyclophosphamide and fludarabine. Cohorts 1, 2, 3, and expansion were to receive transduced cell doses of up to: 0.12 × 10⁹, 1.2 × 10⁹, 6 × 10⁹, and 10 x 10⁹, respectively. Results: As of 23 October 2019, 9 pts were treated in dose escalation with no DLTs; 25 pts were treated in expansion. Median age was 56.5 yr (range: 31-78). All pts received prior chemotherapy. Most common ( > 30%) AEs ≥Grade 3 were lymphopenia, leukopenia, neutropenia, anemia, thrombocytopenia, and febrile neutropenia. Two pts had trial-related deaths (aplastic anemia and CVA) leading to modification of the lymphodepletion regimen and eligibility criteria. In Cohort 3/expansion (28 pts), Best Overall Response was PR (7), SD (11), PD (5), non-evaluable (5). All PRs, at the time of data cut-off, were in patients with synovial sarcoma. Transduced T-cells were detectable in all patients. Tumor infiltration of SPEAR T-cells was detectable in several cohort 3/expansion pts. Conclusions: The Phase I single agent ADP-A2M4 trial will complete enrollment shortly and updated data will be presented. ADP-A2M4 shows promising efficacy and a manageable safety profile at a dose range of 1.2 – 10 × 10⁹. Clinical activity in various tumors has led to a separate on-going low dose radiation sub-study of this trial, a Phase II trial in sarcoma (SPEARHEAD-1, NCT04044768), and a Phase I trial (SURPASS, NCT04044859) with ADP-A2M4CD8, a next-generation SPEAR T-cell targeting MAGE-A4. Clinical trial information: NCT03132922