An Engineered IL-15 Cytokine Mutein Fused to an Anti-PD1 Antibody Improves Intratumoral T Cell Function and Anti-tumor Immunity (human)

Background: Cancer Immunotherapy with cytokines has demonstrated clinical efficacy but is frequently accompanied with severe adverse events caused by excessive and systemic immune activation. Here, we addressed these challenges by engineering a fusion protein of a single, potency-reduced, IL-15 mutein and an anti-PD1 antibody (αPD1-IL15m). This immunocytokine is designed to deliver PD1-mediated avidity-driven IL-2/15 receptor stimulation preferentially to PD1-positive tumor-infiltrating lymphocytes (TILs) while reducing the natural preference of IL-15 for circulating peripheral NK or T cell Methods: We isolated human lymphocytes from resected hepatocellular carcinoma tissue and cultured these tumor-infiltrating lymphocytes (TILs) in vitro in the presence or absence of an PD1-targeted IL15 mutein, anti-PD1 antibody or IL-15 agonist. After 9 days, CD4+ TILs and CD8+ TILs were sorted by FACS and RNA of 3,000 to 150,000 cells was isolated. Results: The PD1-IL15 fusion cytokine enhanced pro-survival, proliferation and activation pathways in tumor-infiltrating CD4+ and CD8+ cells compared to untreated controls as well as to the combined treatment of single agents (anti-PD1 antibody and IL-15 agonist) RNA-Seq of HCC-derived TILs after 9 days in vitro in the absence (ctrl) or presence of PD1-IL15 (m2) or the combined treatment of anti-PD1 and IL-15 agonist (comb).