LAUSR

Background The overall survival rate for pediatric osteosarcoma (OS), neuroblastoma (NB) and glioblastoma (GBM) in children with relapsed/refractory and metastatic disease remains dismal. Our group has successfully expanded peripheral blood Natural Killer cells (exPBNK) with irradiated feeder cells (Chu/Cairo, et al, Can Imm Res 2015). ALT-803 (N-803) is a superagonist of an IL-15 variant bound to an IL-15RαSu-Fc fusion with enhanced IL-15 biological activity (Zhu et al. 2009 J Immunol). Tim-3 was found expressed on active NK cells and its expression in cancer patientsO NK cells correlated with disease stage and prognosis. Objective To determine if the combination of N-803 and TIM-3 blockage significantly enhances exPBNK cell cytotoxicity against OS, GBM and NB Method PBMCs were expanded with lethally irradiated K562-mbIL21-41BBL cells. CD56+CD3− exPBNK cells were isolated using Miltenyi NK cell isolation kit. N-803 was generously provided by Altor BioScience. ExPBNK were cultured with 3.5ng/ml N-803 and 10 or 20ug/ml anti-TIM-3 antibody. NK proliferation, NK receptors expression and cytotoxicity were examined (Chu/Cairo, oncoimmunology, 2017). Results N-803 increased NK activating receptorO expression: NKG2D, NKp30, NKp44, and NKp46. N-803 significantly enhanced exPBNK in vitro cytotoxicity against OS, NB and GBM (p Conclusions The combination of N-803 and anti-Tim-3 blockage significantly enhanced exPBNK in-vitro cytotoxicity against OS, NB and GBM cells. In-vivo effects of the combination are under investigation.