The First-in-Human ENCIT01 Trial Comparing Second- versus Third-Generation L1CAM-specific CAR T Cells in Patients with Primary Refractory or Relapsed Neuroblastoma

PURPOSE: Outcomes for children with relapsed and refractory neuroblastoma are dismal. ENCIT-01 (NCT02311621) was a first-in-human clinical trial for patients with relapsed and refractory neuroblastoma using chimeric antigen receptor (CAR) T cells targeting L1CAM, an adhesion molecule that is overexpressed in neuroblastoma with limited normal tissue expression. PATIENTS AND METHODS: This trial evaluated three different CAR constructs: a short-spacer second-generation 4-1BB CAR (2GS, arm A), a short-spacer third-generation 4-1BB + CD28 CAR (3GS, arm B), and a long-spacer second-generation 4-1BB CAR (2GL, arm C). RESULTS: Thirty-six patients were enrolled, of whom 22 were treated (arm A/2GS n = 11, arm B/3GS n = 8, and arm C/2GL n = 3). Thirty-four of 36 patients had a CAR T-cell product successfully manufactured. Cytokine release syndrome, skin rash, and hyponatremia were common ≥ grade 2 toxicities. Hyponatremia was dose-limiting in three patients [dose level (DL); DL5 arm A/2GS, DL3 arm B/3GS, and DL2 arm C/2GL]. Patterns of toxicity appeared at lower DLs on arms B and C compared with arm A, suggesting differential potency of the third generation and long-spacer products. No objective responses were seen. Correlative analyses demonstrated CAR T-cell presence in tumor and skin, with evidence of macrophage tumor infiltration. CONCLUSIONS: Although feasible to manufacture in a heavily pretreated population, L1CAM may not be an appropriate target in neuroblastoma. Additional engineering strategies may be needed to prevent toxicity and provide durable antitumor effects.