Agonist OX40 Immunotherapy Improves Survival in Glioma-Bearing Mice and is Complementary with Vaccination with Irradiated GM-CSF – Expressing Tumor Cells

Abstract

Background-

Glioma immunotherapy is an active area of clinical investigation. Glioma-associated immunosuppression remains an obstacle to efficacious immunotherapy and combination approaches are likely necessary for durable success. OX40 is a member of the tumor necrosis factor receptor superfamily that is upregulated on activated lymphocytes, ligation of which results in enhanced activity and may be active against cancer. We sought to confirm the efficacy of agonist anti-OX40 immunotherapy against glioma and hypothesized that it is complementary with irradiated whole tumor cell vaccination.

Methods-

GL261 tumor cells were implanted into the right frontal lobes of syngeneic mice, which were then treated with controls, agonist anti-OX40 monoclonal antibody, vaccination with subcutaneous injection of irradiated Granulocyte Macrophage Colony Stimulating Factor (GM-CSF) - expressing GL261 cells (GVAX) or vaccination + agonist anti-OX40 therapy. Animals were followed for survival. On day 18, splenocytes were harvested for ELISPOT analyses and brains were harvested for immunohistochemistry and flow cytometry analyses of infiltrating lymphocytes.

Results-

Combination immunotherapy with GVAX and systemic agonist anti-OX40 monoclonal antibody improved survival by 14 days over controls (median survival 36 vs 22 days, p < 0.00005). Systemically, Th1 antitumor immunity was enhanced significantly by combination therapy. In the brain, combination immunotherapy increased the percentage of Th1 CD4+ T lymphocytes and reduced the fraction that were Th2. In the brain, vaccination improved the ratio of CD8+ to FoxP3+ T lymphocytes, while combination immunotherapy reversed intracranial T lymphocyte exhaustion, reducing their co-expression of PD-1 and TIM-3 as well as PD-1 and LAG-3.

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