Improving T-cell therapies for neuroblastoma

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DESCRIPTION (provided by applicant): The intent of this project is to improve the therapeutic potential of T-cell therapy targeting neuroblastoma (NB) by co-expressing a tumor-specific chimeric antigen receptor (CAR) and a cytokine receptor. NB is the most common malignant extracranial tumor of childhood, and children with high-risk disease continue to have a poor outcome despite intensive therapy. New treatment strategies are therefore required. We have recently demonstrated that adoptive transfer of Epstein-Barr-virus-specific CTLs (EBV-CTLs), genetically modified to express a chimeric antigen receptor (CAR) targeting GD2 expressed by neuroblasts, persisted in the circulation for 6 weeks and determined objective tumor responses in 4/8 patients with refractory/relapsed NB. Since it is now evident that tumor responses to CTL infusions correlate with the persistence/expansion of these CTLs, we propose a new strategy to improve the growth of adoptively transferred CAR-GD2-EBV-CTLs. Although in vivo expansion of CTLs can be accomplished in the acutely lymphodepleted host, profund lymphodepletion may be excessively toxic to the majority of refractory/resistant NB patients who have already received significant doses of chemotherapy and radiation. Moreover, the administration of high-doses of IL-2 significantly contributes in increasing the toxicity and in favoring the expansion of regulatory T cells (Tregs) that inhibit the function of anti-tumor CTLs. In contrast to IL-2, the administration of recombinant IL-7 (rIL-7) seems well tolerated and produces polyclonal expansion of naive CD4+ and CD8+ T lymphocytes, without evident increase of Tregs, suggesting that this cytokine can be used to improve the persistence/expansion of adoptively transferred CTLs. Unfortunately, IL-7 has only limited activity on ex vivo expanded tumor-directed CTLs because the expression of IL-7 receptor alpha (IL-7Ra) is rapidly down-regulated once T cells are exposed to antigen stimulation. We found that gene transfer can be used to restore functional IL-7Ra in EBV- CTLs without affecting their antigen specificity and effector function. Based on these data, we propose to evaluate in a preclinical model and then in a phase I clinical trial whether EBV-CTLs co-expressing CAR-GD2 and IL-7Ra infused into refractory/relapsed NB patients safely expand and persist in response to the administration of rIL-7, and whether such engineered CTLs have anti-tumor activity.