First-in-human comparison of second- versus third-generation L1CAM-specific CAR T cells in patients with primary refractory or relapsed neuroblastoma

Abstract

Abstract Outcomes for children with relapsed and refractory neuroblastoma are dismal. ENCIT-01 is our first-in-human experience in patients with relapsed and refractory neuroblastoma using chimeric antigen receptor (CAR) T cells targeting L1-CAM, an adhesion molecule that is overexpressed in neuroblastoma with limited normal tissue expression. This trial evaluated three different CAR constructs: a short spacer second-generation 4-1BB CAR (Arm A), a short spacer third-generation 4-1BB+CD28 CAR (Arm B) and a long spacer second-generation 4-1BB CAR (Arm C). Thirty-six patients were enrolled and 22 were treated (Arm A n=11, Arm B n=8 and Arm C n=3). Cytokine-release syndrome, skin rash and dose-limiting hyponatremia were recurrently encountered toxicities. Patterns of toxicity appeared at lower dose levels on Arm B and Arm C compared to Arm A, suggesting enhanced potency of the third generation and long spacer products. No objective responses were seen. Correlative analyses demonstrated CAR T cells infiltration into tumor and skin, with evidence of macrophage tumor infiltration. In addition, enhanced CD107a production in the third-generation products when compared to patient matched second generation product, potentially explaining the observation of toxicities at lower dose levels. While feasible to manufacture in a heavily pretreated population, additional engineering safety of L1CAM CAR T cells and/or strategies to target the immunosuppressive tumor microenvironment may be needed to prevent toxicity and provide durable anti-tumor effects.