Anti-GD2 Antibodies Conjugated to IL15 and IL21 Mediate Potent Antitumor Cytotoxicity against Neuroblastoma

Purpose: Half of the patients with high-risk neuroblastoma who receive GD2-targeted mAb do not achieve long-term remissions. Recently, the antibody hu14.18 has been linked to IL2 (hu14.18-IL2) to enhance its efficacy and shown promising preclinical and clinical activity. We developed two new immunocytokines (IC) by linking two other gamma(c) cytokines, IL15 and IL21, to hu14.18. The purpose of this study was to compare hu14.18-IL15 and-IL21 with hu14.18-IL2 in their ability to induce antibody-dependent cell-mediated cyto-toxicity (ADCC) against neuroblastoma. Experimental Design: We assessed ADCC of hu14.18-IL15 and-IL2 (human cytokines, cross-reactive to mouse) against GD2(low )and GD2(high) neuroblastoma cell lines in vitro. T-cell-deficient mice with orthotopic patient-derived xenografts (PDX) and immuno-competent mice with transplantable orthotopic neuroblastoma were used to test all three ICs, including hu14.18-IL21 (murine IL21, not cross-reactive to human). Mechanistic studies were performed using single-cell RNA-sequencing (scRNA-seq). Results: hu14.18-IL15 and hu14.18-IL2 mediated equivalent in vitro ADCC by human NK cells. When combined with chemo-therapy, all three ICs similarly controlled the growth of PDXs in nude mice with murine NK effector cells. However, hu14.18-IL15 and-IL21 outperformed hu14.18-IL2 in immunocompetent mice with syngeneic neuroblastoma, inducing complete tumor regressions and extending survival. scRNA-seq data revealed an increase in CD8 thorn T cells and M1 tumor-associated macrophages and decreased regulatory T cells and myeloid-derived suppressor cells in the tumor microenvironment. Conclusions: Hu14.18-IL15 and Hu14.18-IL21 exhibit robust preclinical activity, warranting further consideration for clinical testing in patients with GD2-expressing neuroblastoma.