Abstract LB096: IL15-engineered tumor infiltrating lymphocytes (cytoTIL15TM) exhibit activity against autologous tumor cells from multiple solid tumor indications without IL2

Tumor infiltrating lymphocyte (TIL) therapy has shown promising results in the treatment of metastatic melanoma. However, TIL therapy has conventionally required co-administration of IL2, which is associated with toxicity in patients. We previously showed that melanoma TILs engineered to express membrane-bound IL15 (mbIL15) under the control of the ligand acetazolamide (ACZ) can achieve IL2-independent expansion during manufacturing, antigen-independent persistence in vitro and anti-tumor efficacy in vivo. In the current study, we extend the cytoTIL15 cell therapy product concept to indications beyond melanoma including non-small cell lung cancers (NSCLC), triple-negative breast cancers (TNBC) and head and neck squamous cell carcinomas (HNSCC), tumor types which represent significant unmet medical needs, particularly in the post-checkpoint inhibitor refractory setting. TILs from primary NSCLC, HNSCC and TNBC were engineered to express mbIL15 in the presence of ACZ and expanded in the absence of IL2 using our proprietary rapid expansion protocol (REP). CytoTIL15 cells were predominantly CD8 positive, enriched for mbIL15 expression and maintained T cell receptor variable beta chain (TCRVβ) diversity throughout expansion. In vitro antigen- and cytokine-independent survival and polyfunctionality of cytoTIL15 cells was measured from cultures that included ACZ. To assess anti-tumor activity, cytoTIL15 cells were co-cultured with autologous patient-derived cell lines (PDc) or tumor digests from patient-derived xenografts (PDx), and cytotoxicity and IFNγ release into supernatant was measured. In vitro, cytoTIL15 cells + ACZ exhibited similar or increased polyfunctionality compared to unengineered TIL + IL2. Unlike unengineered TILs, cytoTIL15 cells + ACZ persisted in an antigen-free setting without IL2, were cytotoxic to autologous PDc and released IFNγ in response to autologous PDx tumor digest. Taken together, these data show that IL2-independent, fully functional cytoTIL15 cells can successfully be generated from tumors such as NSCLC, HNSCC & TNBC, which afflict large numbers of patients. Citation Format: Kyle D. Pedro, Rachel Burga, Alonso Villasmil Ocando, Meghan Langley, Gauri Kulkarni, Zheng Ao, Benjamin Primack, Theresa Ross, Violet Young, Jeremy Tchaicha, Michelle Ols, Jan Ter Meulen. IL15-engineered tumor infiltrating lymphocytes (cytoTIL15TM) exhibit activity against autologous tumor cells from multiple solid tumor indications without IL2 [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 LB096.