Abstract LB093: Engineering tumor infiltrating lymphocytes from sarcoma and colorectal tumors with membrane bound IL-15 for IL-2 independent expansion and enhanced cytotoxicity against autologous tumor cell lines

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Abstract Tumor infiltrating lymphocytes (TIL) have shown promising efficacy in immunologically “hot” solid tumors that have a high level of T cell infiltration, such as melanoma. However, current treatment regimens require high dose IL-2 administration to support TIL survival, which limits their clinical applications due to IL-2 related toxicity. Obsidian Therapeutics is engineering TIL with membrane bound IL-15 (mbIL15) to eliminate the dependence of TIL on exogenous IL-2, potentially enhancing the tolerability of TIL therapies. Because there is a high unmet medical need in patients with tumors colder than melanoma, we evaluated mbIL15-engineered TIL expansion and functionality from colorectal cancer (CRC) and sarcoma biopsies. Using an IL2-independent, proprietary rapid expansion process (REP) we successfully expanded mbIL15-engineered TIL from both CRC and sarcoma, despite significantly lower T-cell numbers in the tumor tissues (average of 12-15% CD45+ TIL versus 64% in melanoma). mbIL15-engineered TIL showed an enrichment for CD8+ T cells throughout the REP and high T cell receptor variable beta chain (TCR Vbeta) diversity. mbIL15-engineered TIL also exhibited lower immune checkpoint expression (LAG3/PD-1) and higher activation marker expression (CD25/CD27/CD28) when compared with unengineered TIL expanded from the same tumors using a conventional REP with IL-2. mbIL15-engineered TIL were polyfunctional, as defined by expression of more than one effector molecules (CD107a, perforin, interferon gamma (IFN-γ), tumor necrosis factor alpha (TNF-α), and granzyme b) in response to CD3/CD28 stimulation. To examine the cytotoxic function of mbIL15-engineered TIL, we developed autologous cell lines from the same tumors that were used to generate the TIL. Using whole exome and RNA sequencing we found that the autologous tumor cell lines maintained expression of conserved tumor antigens and HLA-expression when compared with the primary tumor. When co-cultured with the autologous tumor cell lines, mbIL15-engineered TIL secreted higher levels of IFN-γ and induced higher cytotoxicity as compared to unengineered TIL cultured with IL-2. Taken together, these data demonstrate that mbIL15-engineered TIL can successfully be expanded from comparatively “cold” tumors with low T-cell infiltration, such as CRC and sarcoma, while maintaining high TCR diversity and polyfunctionality and demonstrating higher cytokine production and cytotoxic activity against autologous tumor lines, compared to conventional TIL with IL2. Citation Format: Zheng Ao, Carmela Passaro, Bulent A. Aksoy, Balazs Koscso, Rachel Burga, Kyle Pedro, Natasha Ly, Nirzari Shah, Alonso V. Ocando, Gauri Kulkarni, Trisha Timpug, Seth M. Pollack, Jan ter Meulen, Michelle L. Ols. Engineering tumor infiltrating lymphocytes from sarcoma and colorectal tumors with membrane bound IL-15 for IL-2 independent expansion and enhanced cytotoxicity against autologous tumor cell lines [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB093.