EXTH-85. ASSESSMENT OF ANTI-CD69 ANTIBODY THERAPY ALONE OR IN COMBINATION WITH ANTI-PD-1 IN MURINE GBM

Abstract BACKGROUND Glioblastoma multiforme (GBM) is an aggressive central nervous system malignancy with a dismal prognosis. There is continued interest in trying multiple immunotherapy modalities for this intractable cancer. Cluster of differentiation 69 (CD69), is an early marker of T and NK cell activation. CD69 play multiple roles in T cell-mediated immunoregulation with immune inhibitory role in antitumor immunity. Previous preclinical work in non-CNS malignancies has demonstrated that targeting CD69 can improve clinical outcome and anti-tumor immunity. We aimed to assess anti-CD69 Ab therapy alone or in combination with anti-PD-1 in murine GBM. METHODS We explored transcriptomic data from 163 GBM patients using the TCGA database. We then tested the therapeutic value of anti-CD69 immunotherapy in a preclinical model of GBM and assessed the ideal timing of treatment with anti-CD69 Ab by evaluating survival and immune tumor-microenvironment by flow cytometry. Two treatment-timings with anti-CD69 Ab were further evaluated either alone, or in combination with anti-PD1 Abs and compared to control and to anti-PD1 only treatment. Survival data was collected. RESULTS CD69 expression was significantly increased in GBM patients tissues as compared with normal brains and increased CD69 expression was associated with worse progression-free survival. Treatment-timing with single dose anti-CD69 Ab at day 1 or three doses at days 4, 8 and 12 post tumor-injection minimally improved the median survival time of animals. In addition, effective CD69 blockage and significantly elevated PD-1 expression on NK cells was found in these timings, making them good candidates to evaluate anti-CD69 Ab therapy alone or in combination with anti-PD-1 Ab. However, when assessing these treatment-timings with anti-CD69 Ab alone or in combination with anti-PD1 no survival benefit was found. CONCLUSION This is the first study assessing anti-CD69 Ab therapy alone or in combination with anti-PD-1 in murine GBM. While some effect was found on the cellular level, this didn’t translate to survival benefit and results are overall negative.