PROJECT SUMMARY Primary central nervous system lymphoma (PCNSL) is a rare hematologic maligancy in which non-Hodgkin lymphoma (NHL) initially presents in the central nervous system (CNS). Therapeutic options for PCNSL are limited; standard of care high-dose methotrexate-containing regimens have been unchanged for over 40 years, and are not curative in most patients. Chimeric antigen receptor (CAR) T cell therapy targeting CD19 (CD19- CAR T cells) is a powerful form of immunotherapy that has an established safety profile when delivered intravenously (IV) to treat patients with NHL. Our clinical platform for manufacturing CD19-CAR T cells at City of Hope (COH) has been evaluated in a series of phase 1 clinical trials for B cell acute lymphoblastic leukemia (ALL) and for NHL. To date, all previous and ongoing CD19-CAR T cell trials have infused the CAR T cell product IV. We have preliminary evidence that IV-administered CD19-CAR T cells can be detected in the CNS and have anti-tumor activity in treating patients with PCNSL. However, the efficacy of IV CAR T cell therapies for patients with PCNSL is limited, possibly due to poor trafficking of CAR T cells from blood to CNS that may result in reduced activity against PCNSL compared to systemic NHL. In phase 1 trials at COH, locoregional delivery of CAR T cells to treat CNS malignancies such as glioblastoma has led to improved outcomes. Studies in our animal models show improved disease response, durability and resistence to tumor rechallenge using intracerebroventricular (ICV)- vs IV- delivered CD19-CAR T cells in xenograft mouse models of CNS lymphoma. Thus, to optimize the efficacy of CD19-CAR T cells and improve the outcomes of patients with PCNSL, we propose to administer CD19-CAR T cells via ICV delivery. We hypothesize that ICV-delivered CD19-CAR T cells will be safe and demonstrate high anti-PCNSL activity. In Specific Aim 1, we will conduct a phase 1 clinical trial to assess the safety and activity, and determine the recommended phase 2 dose (RP2D) of ICV delivered CD19-CAR T cells in participants with PCNSL. In Specific Aim 2, we will conduct a series of correlative studies to assess mechanisms of toxicity, CAR T cell persistance, trafficking to the peripheral blood, immune cell phenotype, and effect on tumor. We plan to examine the effects of ICV-delivered CAR T cells on normal CD19+ B cells in the peripheral blood to determine whether CAR T cells traffic from the CNS to the blood, as we expect based on our preclinical animal models of PCNSL. Activity against normal B cells in the blood would indicate that ICV delivery could be a viable treatment option for patients with secondary CNS lymphoma, who have both CNS and systemic disease. Successful completion of the proposed clinical trial and correlative studies will expand therapeutic options for patients with PCNSL and could inform the design of a potential subsequent clinical trial to evaluate the safety and efficacy of treating patients wit...