VLA-4–targeted 67Cu-LLP2A preconditioning enhances efficacy of T-cell-based adoptive immunotherapy

Project Summary & Abstract Adoptive T cell therapies (ACT) including chimeric antigen receptor (CAR) T cells are novel immunotherapies with unparalleled successes, especially in patients with leukemia. However, they have limited efficacy in solid tumors. One barrier to success is the ability of ACT to penetrate the solid tumor microenvironment (TME), where adoptive T cells often encounter resident suppressive immune cell lineages. The administration of lymphodepleting conditioning in the form of chemotherapy, fludarabine/cyclophosphamide (FLU/CY) prior to the infusion of T cells is a critical step to ensure T cell engraftment and persistence. The addition of total body irradiation (TBI) to FLU/CY can further enhance lymphodepletion but comes at a cost of off-target toxicity. Thus, the use of an agent that can more selectively lymphodeplete may improve the efficacy of ACT without increased off-target toxicity. LLP2A is a peptidomimetic small molecule with a high affinity for very late antigen- 4 (VLA-4), expressed at high levels in lymphocytes and several cancers including melanoma and neuroblastoma. Here, we propose to test VLA-4–targeted 67Cu-LLP2A radionuclide therapy (TRT) as a single agent or in combination with dose-reduced (DR)-FLU/CY prior to ACT in two syngeneic solid tumor models (pmel-1/hgp100 B16 melanoma and GD2 CAR/NXS-2 neuroblastoma model). We hypothesize that the combination of 67Cu-LLP2A + DR-FLU/CY is a more effective lymphodepleting regimen than FLU/CY alone (Hypothesis 1). We also hypothesize that 67Cu-LLP2A TRT can reduce tumor burden through direct radiation- induced cell death and can facilitate T-cell mediated killing. We hypothesize that this new 67Cu-LLP2A conditioning regimen will extend the survival of mice with VLA-4–expressing solid tumors treated with ACT through greater penetration and activity of adoptive T cells within solid tumors (Hypothesis 2). To prove this, in Aim 1, we will use state-of-the-art dosimetry and biodistribution studies to determine the dose where 67Cu- LLP2A as a single agent or combined with DR-FLU/CY can achieve adequate lymphodepletion for ACT without causing toxicity as well reduce tumor burden through direct cytotoxic effects. Then in Aim 2, we will examine the ability of systemically administered 67Cu-LLP2A to enhance the efficacy of ACT in two syngeneic solid tumor models. After completion of these aims, we will demonstrate that 67Cu-LLP2A TRT has the potential to redefine current conditioning approaches for ACT and improve the outcomes of patients with solid tumors.