Abstract 2562: Affinity-enhanced T-cell receptor (TCR) for adoptive T-cell therapy targeting MAGE-A4

Melanoma-associated antigens-A (MAGE-A) are members of an extensive family of cancer/testis (CT) antigens. Although emerging studies highlight the potential role of MAGE-A family members in promoting cancer growth, the biological function of MAGE-A4 remains poorly understood. MAGE-A4 is an attractive target because it has a high frequency of expression in multiple solid tumors according to The Cancer Genome Atlas (https://cancergenome.nih.gov/). In an attempt to further characterize its expression in solid tumors, immunohistochemistry analysis was performed in 534 resected non-small cell lung carcinoma (NSCLC) cases, stage I to IV with clinicopathological information including overall survival and recurrence. MAGE-A4 expression was observed in 24% of all NSCLC cases, with higher frequency observed in squamous cell carcinoma (SCC) (51%) versus adenocarcinoma (8%). MAGE-A4 expression was observed in 23% of the primary tumors and 48% of the recurrent tumor samples. Log-rank (Mantel-Cox) analysis showed that histology diagnosis, pathological stage, and MAGE-A4 expression are independent prognostic factors in NSCLC. However, no MAGE-A4 prognostic value was observed when analyzing the SCC subtype. An HLA-A*02-restricted MAGE-A4 TCR specific for MAGE-A4 230-239 peptide GVYDGREHTV was identified from a pool of parental TCRs and engineered to optimize specificity and activity (MAGE-A4 c1032 ). TCR fine specificity was assessed initially by mapping the response of the MAGE-A4 c1032 T-cells to panels of synthetic peptides with combinatorial substitutions at each amino acid with every other possible amino acid (X-Scan), to identify potentially cross-reactive peptides in the human and common pathogen proteomes. Secondly, MAGE-A4 c1032 T-cells were screened against a wide panel of normal primary cells from multiple organ systems, induced pluripotent stem cell-derived cells (iCells), and autologous whole blood to test for off-target reactivity, and against a panel of EBV-derived B-lymphoblastic cell lines expressing a wide range of HLA molecules to assess the risk of alloreactivity. Alloreactivity was observed in antigen negative cells expressing HLA-A*02:05, and therefore this allele is exclusionary. MAGE-A4 c1032 T-cell potency was assessed by a variety of in vitro assays, including proliferation, IFN-γ release and cytotoxicity in response to antigen-positive tumor lines in 2D and 3D culture, and cytokine release in response to freshly prepared antigen-positive primary tumor material. In conclusion, MAGE-A4 is a promising target for SPEAR T-cell therapy, and clinical trial opened this year to treat patients with inoperable or metastatic (advanced) NSCLC (SCC, adenosquamous, or large cell carcinoma), ovarian, head and neck SCC, gastric, esophageal (SCC or adenocarcinoma), urothelial tumors and melanoma (NCT03132922). Citation Format: Joana Senra, Pamela Villalobos, Barbara Mino, Luisa Solis, Carmen Behrens, Joseph P. Sanderson, Manoj Saini, Andrew B. Gerry, Nicholas J. Pumphrey, Miguel Maroto, Boris Sepesi, Patrick Hwu, David S. Hong, Elizabeht A. Mittendorf, George S. Blumenschein, Ignacio I. Wistuba, Gwendolyn Binder-Scholl, Rafael Amado. Affinity-enhanced T-cell receptor (TCR) for adoptive T-cell therapy targeting MAGE-A4 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2562.