Long-acting interleukin-7 Improves the Efficacy of Oncolytic Viral Therapy in Glioblastoma

Introduction: Despite advances in immunotherapy, the prognosis for patients with glioblastoma (GBM) remains poor. The efficacy of GBM-targeted immunotherapies is limited by the paucity of functional T-cells in the tumor microenvironment, a consequence of the local and systemic immunosuppression prevalent in patients with GBM. To address these challenges, we developed a treatment strategy we term "expand and pull," utilizing systemic rhIL-7-hyFc (efineptakin alfa, NT-I7), a long-acting recombinant human interleukin-7, to boost peripheral T-cell numbers ("expand"), followed by intratumoral oncolytic virus treatment to attract these cells to the tumor ("pull").

Methods: 1×10^3 SB28 tumor cells were implanted intracranially in C57BL/6J mice. Mice were injected subcutaneously with rhIL-7-hyFc on day 7 and 10, followed by intratumoral Zika virus (ZIKV), Δ10 3′-UTR ZIKV, or D24-RGD adenovirus on day 14. Brain, cervical lymph nodes, and blood were collected and analyzed via flow cytometry on days 17 and 21. On day 21, intratumoral CD45-high cells were sorted for single-cell RNA sequencing to further characterize the immune microenvironment.

Results: rhIL-7-hyFc increased systemic T-cell abundance (5,623 cells/uL vs. 136 cells/uL, p< 0.05), particularly cytotoxic CD8+ T-cells (4,776 cells/uL vs. 47 cells/uL, p< 0.05). While ZIKV or rhIL-7-hyFc alone showed no survival benefit, their combination resulted in 40% long-term survivors (p < 0.05). Immunoprofiling demonstrated that treatment with rhIL-7-hyFc and ZIKV increases tumor-infiltrating effector memory CD8+ T-cells, enhances the expression of CD8+ cytotoxic effectors, and expands TCR clonal populations. Adding anti-PD1 antibody further increased long-term survival to 80% (p < 0.05). Similar survival improvements were obtained with the safer, genetically modified Δ10 3′-UTR ZIKV and the oncolytic adenovirus D24-RGD.

Conclusion : The combination of rhIL-7-hyFc and ZIKV increases systemic T-cell levels and enhances T-cell infiltration and function within tumors, resulting in long-term tumor-free survival. Overall, our findings indicate that augmentation of both the systemic and local immune responses improves the efficacy of GBM-targeted viral therapies.