NT-I7, a novel long-acting interleukin-7, in combination with anti-PD-1 checkpoint blockade for the treatment of glioablastoma - PROJECT SUMMARY Patients with glioblastoma (GBM) are routinely treated with radiation (RT), temozolomide (TMZ), and glucocorticoids. However, these treatments often result in long lasting treatment-related lymphopenia (TRL) that is associated with shorter survival. In addition, lymphopenia is associated with unresponsiveness to checkpoint inhibitors. Here, we explore a novel approach to mitigate TRL in order to enhance response to immunotherapy and improve survival in GBM. Interleukin 7 (IL-7) is a hematopoietic growth factor and homeostatic cytokine that preferentially supports the growth and survival of the B and T lymphocytes. NT-I7 is a novel long-acting form of recombinant human IL-7 fused with hybrid Fc. We recently reported that NT-I7 significantly prolonged survival in glioma murine models through increasing cytotoxic CD8 T cells and decreasing regulatory T cells in the tumor. The survival advantage from NT-I7 is CD8 dependent in our model. Additionally, we conducted a first in-human phase I/II clinical trial to evaluate the safety and effect of NT-I7 on absolute lymphocyte counts (ALC) in patients with gliomas following standard RT and TMZ therapy. We found that NT-I7 is well tolerated and significantly increased ALC. Immunophenotyping of peripheral blood suggested predominately CD8 expansion following NT-I7 administration. In addition, preliminary data from an immune resistant CT2A murine glioma model demonstrated that combination of NT-I7 with anti-PD-1 blockade increased survival. Thus, we have developed a new phase II study with a safety run-in cohort evaluating the safety and efficacy of neoadjuvant and adjuvant NT-I7 plus pembrolizumab in patients with recurrent GBM. Here we are requesting funding for obtaining and processing specimens and for conducting proposed correlative studies associated with this trial as outlined in Aim 1. In addition, we will be conducting preclinical studies to dissect the mechanisms of NT-I7 immunotherapeutic effect. We hypothesize that NT-I7 can enhance immune response through antigen specific priming CD8 response and improve anti-tumor efficacy of checkpoint blockade in GBM. In Aim 1, we will collect pre- and post-treatment tumor tissues and peripheral blood to conduct comprehensive immuno-profiling using state-of-the-art CyTOF and Hyperion Imaging Mass Cytometry. Additionally, we will assess CD8 T cell infiltration within the CNS and evaluate the predictive performance of peripheral CD4 and CD8 Tscm as a biomarker of therapeutic efficacy. In Aim 2, we will dissect the mechanisms of NT-I7 on enhancing CD8 T cell trafficking and infiltration into the CNS in glioma murine models. Our group has generated novel transgenic mice that enable conditional silencing of the MHC class I molecules, H-2Kb on specific cell types. We will employ these transgenic mice to define the specific antigen presenting cell subsets (macrophages, microglia, and dendritic cells) contribute to the generation of distinct brain infiltrating CD8 T cell responses with NT-I7 treatment.
