NT-I7, A LONG-ACTING INTERLEUKIN-7, PROMOTES EXPANSION OF CD8 T CELLS AND NK CELLS AND IMMUNE ACTIVATION IN PATIENTS WITH NEWLY DIAGNOSED HIGH-GRADE GLIOMAS AFTER CHEMORADIATION

Background Lymphopenia is common after chemoradiation for treatment of high-grade gliomas (HGG) and is associated with reduced survival.1 Interleukin-7 (IL-7) promotes T-cell maturation and proliferation and is inappropriately low in lymphopenic patients with HGG.2 We previously demonstrated that first-in-class long-acting IL-7, NT-I7 (efineptakin alfa), reverses lymphopenia and improves survival in murine glioma models.3 This study reports the correlative immune changes after NT-I7 treatment in patients with newly diagnosed HGG in a Phase I/II clinical trial. Methods Enrolled patients had newly diagnosed HGG treated with concurrent radiotherapy (RT) and temozolomide (TMZ) plus adjuvant TMZ every 4 weeks. NT-I7 was administered intramuscularly 1 week after completion of RT/TMZ and then every 12 weeks, for up to 4 total doses. Phase I utilized the 3+3 design to identify the maximum tolerated dose (MTD). Phase II is a double-blinded, placebo-controlled study with 10 patients in each arm. Immune profiling of patients from the Phase I study was performed with multiparametric flow cytometry and multiplex cytokine analysis. Results Phase I was completed with 19 patients. The most common adverse events were grade 1 or 2 injection site reactions (42%). Two patients had dose-limiting toxicities at 960 µg/kg (grade 3 elevated alanine aminotransferase and grade 3 back pain), prompting the selection of MTD as 720 µg/kg. Preliminary analysis of Phase I subjects demonstrated dose-dependent increases in absolute lymphocyte count (ALC; 1.3X-4.1X fold increase from pre-therapy measurements) that peaked at week 4, before adjuvant TMZ. Flow cytometry analysis of peripheral blood showed a significant increase in the frequency of CD8+ T-cells, CD4+ T-cells, and CD56bright natural killer (NK) cells after NT-I7 administration. There was no change in B cell counts. Expression of the IL-7 receptor (CD127) was downregulated on most immune subsets within 1 week after NT-I7 administration and recovered to baseline by week 4. Serum cytokine analysis showed a rapid and significant increase in tumor necrosis factor (TNF), chemokine ligand 9 (CXCL9), and a trend to higher interferon-gamma (IFNγ), 1 week after NT-I7 administration. Conclusions NT-I7 is well tolerated when administered after RT/TMZ for HGG patients. NT-I7 administration prompted an increase in ALC, especially cytotoxic T-cells and NK cells. We also observed rapid increases in key cytokines and chemokines, suggesting immune activation. These findings provide insight into the mechanism of action for NT-I7. Phase II enrollment and additional immune profiling correlates are ongoing. Trial Registration NCT03687957 References Mendez JS, Govindan A, Leong J, Gao F, Huang J, Campian JL. Association between treatment-related lymphopenia and overall survival in elderly patients with newly diagnosed glioblastoma. J Neurooncol 2016;127:329. Campian JL, Ye X, Gladstone DE, Ambady P, Nirschl TR, Borrello I, Golightly M, king KE, Holdhoff M, Karp J, Drake CG, Grossman SA. Pre-radiation lymphocyte harvesting and post-radiation reinfusion in patients with newly diagnosed high grade gliomas. J Neuro-Oncology 2015 1242. 2015;124:307–316. Ghosh S, Yan R, Thotala S, Jash A, Mahadevan A, Hu T, Lee B, Yang SH, Hallahan D, Chheda M, Thotala D, Campian J. 565 a novel long-acting interleukin-7 agonist, NT-I7, increases cytotoxic CD8+ T cells and enhances survival in mouse glioma models. J Immunother Cancer 2020;8(Suppl 3):A599–A599. Ethics Approval This study was approved by Washington University’s ethics board (the Human Research Protection Office); approval number 201810185. Study participants provided written informed consent.