Intratumoral (IT) injection of hu14.18-IL2 immunocytokine (IC) enhances antitumor activity and augments NK infiltration into tumors: analyses of cellular internalization of hu14.18-IL2 by human NK cells (41.44)

• Published in: The Journal of immunology (1950) 2009-04, Vol.182 (1_Supplement), p.41-41.44
• Main Authors: Buhtoiarov, Ilia N., Neal, Zane C., Gan, Jacek, Buhtoiarova, Tatiana N., Hank, Jacquelyn A., Yamane, Brett H., Rakhmilevich, Alexander L., Patankar, Manish S., Gubbels, Jennifer A. A., Gillies, Stephen D, Sondel, Paul M.
• Format: Article
• Language: English
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.182.Supp.41.44

Hu14.18-IL2 (EMD 273063) IC, consisting of GD2-specific mAb and IL2, is in trials for treatment of melanoma and neuroblastoma. Preclinical studies showed augmented antitumor activity when IC is injected IT vs. IV. Human IL2R+CD16+NK cells mediate ex vivo ADCC in the presence of IC that binds them to GD2+ tumor cells. We studied the kinetics of IC presence on the surface of human M21 melanoma and CD25+CD16-NK cell lines, NKL and RL12, after IC binding to the cells via GD2 and IL2R, respectively. For NK cells, ~50% of IC was internalized by 6 h, and ~90% by 24 h of cell culture. Excess free IL2 in the culture did not slow internalization kinetics for these NK cells. IL2-deprivation for 24 h prior to IC arming of NK cells decreased IL2Rα expression and overall IC binding but did not affect internalization kinetics of the bound IC. For NK cells that were prelabeled with IC, the decrease of surface IC levels over 24 h correlated with reduction of ADCC in vitro. Unlike NK cells, M21 cells retained ~70% of IC on the surface following 24 h of culture. When CFSE-labeled NKL cells were injected IV into M21-bearing SCID mice, they migrated better into the tumor when IC was delivered IT than when they were pre-armed with IC before implantation. These preliminary studies suggest that once IC gets to tumor sites, it may stay on the tumor surface for a prolonged time, and that IT injections of IC enhance the recruitment of NK cells to the tumor site.