412. Development of GD2-Specific Immunoliposomes for Immunotherapy of Neuroblastoma

Abstract

Tumor growth creates a highly immunosuppressive tumor microenvironment (TME) that impairs T-cell localization, persistence, or the execution of their effector function. This represents a major and as yet unsolved critical challenge to the development of effective adoptive immunotherapy of solid tumors. To selectively target TME in neuroblastoma and make it permissible for survival and function of tumor-specific T cells, we have developed a novel nanoparticle (NP) delivery platform which consists of 150 nm immunoliposomes rendered specific for neuroblastoma cells using the Fab fragment obtained from the anti-GD2 mAb clone 14g2a. To ensure high density surface coverage and correct orientation of anti-GD2 Fab on the NPs, we synthesized a fusion protein consisting of 14g2a Fab and folate receptor (Fab14g2a-FR) and attached it on the outer layer of the immunoliposomes enriched with folic acid. Rhodamine-labeled GD2-specific but not control NPs could specifically bind GD2-positive CHLA-255 neuroblastoma cells but not GD2-negative LA-N-6 neuroblastoma cells in vitro as determined by FACS. To examine the in vivo biodistribution of NPs, DiR-labeled GD2-specific or non-specific NPs were injected to NOD/SCID mice implanted with CHLA-255 cells. Tumor tissues and normal organs were imaged after 72 hours using ex vivo fluorescence imaging. Up to 58% of GD2-specific NPs accumulated at the tumor sites. The only other organ with significant accumulation of NPs was the liver. Minor traceable portions were detected in the spleen and lung. To utilize the observed targeting capabilities of GD2-specific NPs to achieve antitumor effects, we are now loading NPs with recombinant human (rhIL-7) and will test whether the preferential delivery of rhIL-7 to the tumor site and liver, a major site of NB metastasis, will increase the survival and anti-tumor activity of T and NKT cells engineered to express a GD2-specific chimeric antigen receptor with IL-7Rα. The results of this study will inform design of immunotherapy of neuroblastoma and other tumors in combination with TME-modifying NPs.