Abstract Effective cellular therapies for solid tumors are limited by the lack of tumor-specific antigens. We previously showed that non-mutated self-peptides from essential intracellular neuroblastoma (NB) oncoproteins are presented by common HLA allotypes, enabling selective targeting (Nature 2023). Here, we report IND-enabling studies of second-generation PHOX2B PC-CAR T cells incorporating a 4-1BB costimulatory domain. A GMP-grade lentiviral vector encoding the PHOX2B peptide-HLA-specific CAR was produced at CHOP and used to transduce healthy donor and patient T cells. PHOX2B expression and epitope heterogeneity were analyzed across solid tumors, NB xenografts, and cell lines by RNA-seq, IHC, and a PHOX2B scFv assembled with klickmer detecting the QYNPIRTTF/HLA complex. Safety was evaluated using the X-scan and sCRAP cross-reactivity algorithms integrated with experimental testing across 25 normal HLA-A24/23 primary cell lines and HLA-matched PHOX2B negative cancers. Functional activity was assessed via IncuCyte based cytotoxicity, multiplex cytokine profiling, and T-cell activation/proliferation by flow cytometry. Efficacy was tested in four HLA-A24/23 NB xenografts (including chemotherapy-resistant models) and one non HLA-A*24:02/23:01 NB control in NSG MHC-I/II deficient mice receiving a single ∼7×106 PC-CAR T-cell infusion. Longitudinal expansion, immunophenotype, and transcriptional states were characterized by flow cytometry and single-cell RNA-seq. PHOX2B was highly expressed in all neuroblastomas and pheochromocytomas and not expressed in other cancers. Klickmer staining revealed variable epitope density correlating with PC-CAR T cell activation. PHOX2B PC-CAR T cells mediated potent, dose-dependent killing of HLA-A24/23 neuroblastomas, sparing antigen-negative non-HLA-A24/23 cancer cells unless peptide-pulsed. Antigen engagement triggered proliferation, effector cytokine release, and IFN-γ dependent upregulation of HLA-I, significantly increasing antigen density. No cross-reactivity was detected in co-culture assays. A single dose of PC-CAR T cells induced complete regression (50 days) across all xenografts. One relapse in each of two models either regressed spontaneously with re-emergence of PC-CAR T cells or after re-treatment. Responses were durable 120 days, whereas PHOX2B+ non-HLA-A24:02/23:01 controls showed progressive disease. Expansion peaked at day 14 with CD8+ effector-memory predominance transitioning to central-memory persistence. PHOX2B-directed PC-CAR T cells show stringent specificity, potent cytotoxicity, and curative efficacy in preclinical patient-derived NB models. These IND-enabling data supported the ongoing first-in-human/child Phase 1 trial (NCT07007117), validating PHOX2B as a lineage-restricted immunotherapeutic target in high-risk neuroblastoma. Citation Format: Muzamil Y. Want, Richa Kapoor, David Groff, Keelan O’Reilly, Liron Grossmann, Alvin Farrel, Rebeca A. Ventura, Peiyao Li, Quinlen Marshall, Jenny pogoriler, Daniel Martinez, Matt Beasley, Ben Kiefel, Mark Yarmarkovich, John Maris. Durable remission of high-risk and refractory neuroblastoma by PHOX2B derived peptide-HLA directed CAR T cells: An IND enabling study abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 3707.
Want et al. (2026) studied this question.