47 Generation and Characterization of Ex Vivo Expanded Tumor-Infiltrating Lymphocytes from Renal Cell Carcinoma Tumors for Adoptive Cell Therapy

Abstract Background Autologous therapeutic tumor-infiltrating lymphocyte (TIL) therapy is a promising strategy to enhance anti-tumor immunity. Optimization of ex vivo TIL expansion could expand current immunotherapy options. Previous attempts to generate TIL in renal cell carcinoma (RCC) have been technically challenging. We applied a second-generation manufacturing process, currently used to generate the melanoma TIL product lifileucel, in RCC. Methods Resected primary and metastatic RCC samples were processed using the Gen 2 manufacturing process comprising of pre-Rapid Expansion Protocol (pre-REP) and REP steps. We assessed REP TILs for viability and performed phenotypic and functional characterization. We correlated the tumor immune microenvironment (TIME) with successful TIL expansion. Results Eight of 11 RCC samples underwent successful REP. Three failed cases demonstrated low CD8/FoxP3 ratio and high expression of PD-1 within FoxP3 cells. Expression of exhaustion markers differed between the TIME and expanded TILs; the latter had a TIM3-high/PD-1-low phenotype but retained functional capacity comparable to lifileucel. Figure: Assessment of tumor immune microenvironment (TIME) via multiplex immunofluorescence (IF). Cases that failed REP are indicated in red. (A) Representative image at 60x magnification, fluorophore colors as indicated. (B) Density of tumor-infiltrating CD8+ and FoxP3+ cells. (C) Expression of co-inhibitory exhaustion markers as a percentage of total CD8+ cells. (D) Expression of PD-1 in FoxP3+ cells. (E) Comparison of tissue TIME (dots) with TIL product post-REP (open circles) exhaustion profiles as a percentage of total CD8+ cells. Conclusions The Gen 2 manufacturing process used for lifileucel successfully expanded functional TILs from RCC samples, enabling further study in a clinical trial. TIME features such as low CD8/FoxP3 ratio and high PD-1 expression within FoxP3 cells warrant study as potential biomarkers of successful TIL expansion.