Abstract LB359: OBX-115 TIL from non-small cell lung cancer (NSCLC) are enriched for putative tumor-reactive, stem-like T cells with enhanced tumor cytotoxicity: Results from multimodal phenotyping analysis

Abstract Background: Response to TIL cell therapy is associated with presence of tumor-reactive clonotypes in the infusion product (Chiffelle Immunity 2024, Dean SITC 2024). Incorporating 4-1BB agonism in the pre-rapid expansion protocol (pre-REP) phase of non-engineered TIL manufacturing has been shown to increase TIL expansion and enrich for putative tumor-specific T cells (Frank SITC 2021); TIL engineering and modifications of the REP process may further drive such enrichment. OBX-115 TIL are engineered with regulatable, membrane-bound interleukin 15 (mbIL15), a cytokine that supports expansion of memory CD8+ T cells (Zhang Immunity 1998) in a manufacturing process that includes 4-1BB agonism in both pre-REP and REP (Frank SITC 2021). We sought to determine the phenotype and tumor reactivity of OBX-115 TIL compared with conventional non-engineered TIL in NSCLC. Methods: TIL were generated from paired NSCLC tumor samples using either the OBX-115 process or an IL2-based conventional process. Tumor digests were sequenced using combined single-cell RNA & TCR sequencing. Using a validated tumor-reactive TIL gene-expression profile (Meng Sci Trans Med 2023, Lowery Science 2022), we computationally predicted putative tumor-reactive clonotypes in OBX-115 vs conventional non-engineered TIL. Bulk TCR Vbeta sequencing was used to track the dynamics of these clonotypes throughout TIL expansion. TIL were phenotyped via flow cytometry and assessed for functional reactivity against autologous tumor digests or patient tumor-derived cell lines (PDc) in 3D co-cultures. Results: The OBX-115 process generated a greater number of pre-REP TIL per tumor fragment vs conventional process (average 1.4 × 107 vs 2.3 × 105 cells, p=0.04, n=7), indicative of manufacturing success. Post-REP, OBX-115 TIL displayed higher proportion of CD39-CD69- “stem-like” progenitor cells (Krishna Science 2020) (57±9.6% vs 22±9.0%, p=0.010) and trends toward increased proportion of CD8+ T cells (94±2% vs 57±37%, p=0.133) and lower proportion of PD-1+ cells (3.8±1.6% vs 17±9.8%, p=0.054), relative to conventional TIL. OBX-115 was enriched for putative tumor-reactive TCR clonotypes compared to the conventional TIL, even when sorted for CD8+ cells (tumor-reactive signature score [Meng Sci Trans Med 2023], p<0.05). Moreover, OBX-115 demonstrated superior functional tumor reactivity relative to conventional TIL, marked by increased cytotoxicity against autologous tumor cell lines in 3D co-cultures (p<0.05) and similar or higher IFNγ secretion upon co-culture with autologous tumor digests. Conclusions: Here, we demonstrate that the OBX-115 manufacturing process from NSCLC tumor tissue, incorporating cell-armored-mbIL15-driven expansion and 4-1BB agonism, generates higher TIL yield and a more stem-like phenotype than conventional non-engineered TIL process. Computational analysis reveals the OBX-115 process enriches for putative tumor-reactive TCR clonotypes, which is further supported by in vitro co-culture assays. Together, these favorable attributes support further investigation of OBX-115 in patients with metastatic NSCLC (NCT06060613). Citation Format: Adam J. Schoenfeld, Alonso Villasmil Ocando, Zheng Ao, Bulent A. Aksoy, Ngoc Ly, Nishita Roy, Anand Veerapathran, Giridharan Ramsingh, Jan ter Meulen, Michelle Ols, Matthew Bott. OBX-115 TIL from non-small cell lung cancer (NSCLC) are enriched for putative tumor-reactive, stem-like T cells with enhanced tumor cytotoxicity: Results from multimodal phenotyping analysis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_2):Abstract nr LB359.