Abstract IA09: Harnessing natural and engineered properties of NKT cells for cancer immunotherapy
Authors: Heczey Andras , Courtney Amy N. , Ngai Ho , Tian Gengwen , Robinson Simon N. , Dotti Gianpietro , Metelitsa Leonid S. 
Published: February 2019

Abstract
Due to their natural anti-tumor properties and ability to preferentially localize to the neuroblastoma (NB) tumor site, Vα24-invariant natural killer T cells (NKTs) are promising candidate immune effectors for chimeric antigen receptor (CAR)-based immunotherapies targeting NB and other solid tumors. We have previously demonstrated that human NKTs expressing a CAR specific for ganglioside GD2 (CAR.GD2) mediated potent anti-tumor activity in a xenogeneic NB model in NOD/SCID/IL-2Rγnull mice. In comparison with CAR.GD2 T cells, CAR.GD2 NKTs localized more effectively to the tumor tissues and did not induce graft-versus-host disease (GvHD). Clinical development of NKT cell-based therapeutics requires overcoming two fundamental challenges: 1) the low frequency of NKTs in human peripheral blood, and 2) the limited ability of adoptively transfered NKTs/CAR-NKTs to persist in tumor-bearing animals. To address the first limitation, we have developed a cGMP protocol to isolate NKT cells from leukapheresis products using NKT-specific magnetic beads with the CliniMAX® system (Miltenyi). Isolated NKTs then undergo stimulation with CD1d-expressing antigen-presenting cells pulsed with α-galactosylceramide, retroviral transduction with a CAR-expressing vector, and rapid numeric expansion in cytokine-supplemented culture. This protocol routinely produces more than 109 CAR-NKTs within 17 days with average NKT cell purity and CAR expression of 96% and 54%, respectively. To overcome the second limitation, we incorporated the primary NKT homeostatic cytokine, IL-15, into the CAR.GD2 construct and evaluated its ability to enhance NKT cell in vivo persistence and therapeutic efficacy. Following adoptive transfer into mice bearing human NB xenografts, NKTs expressing CAR.GD2 were undetectable by three weeks whereas CAR.GD2/IL-15 NKTs underwent progressive expansion at sites of NB metastasis, reaching 32% of bone marrow cells two months after a single injection. Treatment with CAR.GD2/IL-15 NKTs resulted in a median survival of 70 days versus 48 days for mice treated with CAR.GD2 NKTs (P &lt; 0.001). Importantly, the robust in vivo expansion and potent anti-tumor activity of CAR.GD2/IL-15 NKTs did not produce off-target toxicity or induce GvHD based on detailed pathological analysis of mouse tissues. These results have enabled the initiation of a first-in-human CAR-NKT clinical trial evaluating the safety of autologous NKTs expressing the GD2-specific CAR with IL-15 in children with relapsed or refractory neuroblastoma (NCT03294954).
Citation Format: Andras Heczey, Amy N. Courtney, Ho Ngai, Gengwen Tian, Simon N. Robinson, Gianpietro Dotti, Leonid S. Metelitsa. Harnessing natural and engineered properties of NKT cells for cancer immunotherapy [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr IA09.