Combinatorial immunotherapy of anti-MCAM CAR-modified expanded natural killer cells and NKTR-255 against neuroblastoma

Pediatric patients with recurrent metastatic neuroblastoma (NB) have a dismal 5-year survival. Novel therapeutic approaches are urgently needed. The melanoma cell adhesion molecule (MCAM/CD146/MUC18) is expressed in a variety of pediatric solid tumors, including NB, and constitutes a novel target for immunotherapy. Here, we developed a chimeric antigen receptor (CAR) expressing natural killer (NK) cell-targeting MCAM by non-viral electroporation of CAR mRNA into <i>ex vivo</i> expanded NK cells. Expression of anti-MCAM CAR significantly enhanced NK cell cytotoxic activity compared to mock NK cells against MCAM^high but not MCAM^low/knockout NB cells <i>in vitro</i>. Anti-MCAM-CAR-NK cell treatment significantly decreased tumor growth and prolonged animal survival in an NB xenograft mouse model. NKTR-255, a polymer-conjugated recombinant human interleukin-15 agonist, significantly stimulated NK cell proliferation and expansion and further enhanced the <i>in vitro</i> cytotoxic activity and <i>in vivo</i> anti-tumor efficacy of anti-MCAM-CAR-NK cells against NB. Our preclinical studies demonstrate that <i>ex vivo</i> expanded and modified anti-MCAM-CAR-NK cells alone and/or in combination with NKTR-255 are promising novel alternative therapeutic approaches to targeting MCAM^high malignant NB.