Preliminary clinical outcomes of ADP-A2M4CD8, a next-generation autologous T-cell receptor T-cell therapy, in patients with advanced urothelial cancer.

517 Background: ADP-A2M4CD8 is a specific peptide enhanced affinity receptor mixed CD4+ and CD8+ T-cell therapy targeting the cancer testis antigen MAGE-A4 and modified with addition of a CD8α co-receptor designed to provide additional functionality to CD4+ T-cells. ADP-A2M4CD8 has demonstrated an acceptable benefit to risk profile in the Phase 1 SURPASS trial (NCT04044859) in HLA A*02–eligible patients with unresectable or metastatic tumors positive for MAGE-A4.1 Here we report updated clinical outcomes in patients with urothelial cancer (UC). Methods: SURPASS is a first-in-human trial consisting of a modified 3+3 dose-escalation design and an expansion cohort. Autologous T-cells are obtained by leukapheresis, transduced with a self-inactivating lentiviral vector expressing the MAGE-A4-specific T-cell receptor and the CD8α co-receptor, and infused back to the patients as ADP-A2M4CD8 following lymphodepleting chemotherapy. Primary and secondary objectives are safety and anti-tumor activity, respectively. Results: At ESMO 2022, we reported promising results from SURPASS in several tumour types.2 In the 43 evaluable patients, the overall response rate was 28%, including 1 complete response and 11 partial responses (PR), and an additional 2 unconfirmed PRs awaiting confirmatory scans (as of August 1, 2022). Data from the 7 evaluable patients in the UC subset (updated September 6, 2022) showed that 3 (43%) had a best overall response of PR, and 1 (14%) had an unconfirmed PR. Disease control rate was 100% (3 PR + 1 unconfirmed PR + 3 stable disease). Adverse events have been consistent with those typically observed with lymphodepletion chemotherapy or cellular therapy. This trial is ongoing; data from additional patients with UC treated by January 2023 and updated translational data will be presented. Conclusions: ADP-A2M4CD8 continues to show an acceptable benefit to risk profile in multiple MAGE-A4+ unresectable or metastatic tumors, and preliminary encouraging evidence of efficacy in UC. An additional treatment cohort has been included in the updated trial protocol to evaluate ADP-A2M4CD8 combined with nivolumab. 1. Hong DS, et al. E-poster 540P: ESMO 2021; Virtual. 2. Hong DS, et al. Ann Oncol 33(suppl_7); S331-S355, Abstract 735MO. ESMO 2022. Clinical trial information: NCT04044859 .