Abstract LB-235: Delta-24-RGD oncolytic adenovirus treatment downmodulates the key regulator of T-cell exhaustion TIM3 in malignant gliomas

Abstract

Abstract T cell exhaustion is a key mechanism of tumor immune suppression and is commonly observed in several cancers. The exhausted T cells in the tumor microenvironment overexpress inhibitory receptors, show decreased effector cytokine production, and exhibit diminished cytolytic capabilities, resulting in the failure to eliminate cancer cells. Restoring the activity of exhausted T cells is a desirable strategy to improve immune-based anti-cancer therapies, and has yielded encouraging results. Exhausted T cells are characterized by the expression of high levels of PD-1 and TIM3, which cooperate to induce T-cell hyporesponsiveness. In this study, we sought to determine whether the infection of human gliomas with oncolytic viruses modifies the expression of T cell markers. As part of a phase 1, dose-escalation, biological-endpoint clinical study (NCT00805376) of Delta-24-RGD, a Rb-targeted, tumor-selective, replication-competent oncolytic adenovirus, conducted in 37 patients with recurrent malignant glioma, 12 patients received an intratumoral injection through an implanted catheter, followed 14-days later by en bloc resection and Delta-24-RGD injections into the post-resection tumor bed. 10 surgical post-treatment specimens and 5 pre-treated tumors were examined for markers of immune response. From all selected cases, formalin fixed, paraffin embedded tissue blocks were examined. IHC was performed using a Leica Bond Max automated stainer as previously described. The slides were scanned in an Aperio AT2 scanner (Leica Biosystems). The IHC scores for CD3, CD4, CD8, CD45Ro, FOXP3, TIM3, LAG-3, VISTA, CD20, CD57, CD68, and OX40 were expressed as cell density in the inflammatory cell population (number of positive cells per mm square of tumor area), except PD-L1, PD-L2, B7-H3, B7-H4, IDO-1, which were expressed using percentage of positive tumor cells, and also as H-Score of the tumor cells (which integrates percentage of tumor cells and intensity of staining, with a final H-score ranging from 0 to 300). Correlations between immunostaining marker values and survival and dose level were assessed using Spearman rank correlation analysis. Differences in immunostaining marker values before and after treatment were assessed using the Wilcoxon rank sum test. These analyses demonstrated that all the target proteins are expressed in gliomas in different patterns and tumor regions. Although, we did not observe significant treatment-related changes in the expression of PD-1 in lymphocytes and PD-L1 in glioma cells, TIM3, a marker for T cell exhaustion, was downregulated after Delta-24-RGD treatment. In addition, expression of B7-H3, a marker of poor prognosis in other tumors, correlated with poorer survival. Because PD-1 and TIM3 cooperate to maintain T-cell exhaustion our data provide a rationale for the combination of Delta-24-RGD and anti-PD-1 antibodies for the treatment of malignant gliomas. Importantly, a multicenter clinical trial to test this strategy has already been open (NCT02798406). Citation Format: Juan Fueyo, Candelaria Gomez-Manzano, Pamela Villalobos, Jaime Rodriguez-Canales, Barbara Mino, Ignacio Wistuba, Kenneth Hess, Marta Alonso, Sonia Tejada, Ricardo Diez-Valle, Brett Ewald, Frank Tufaro, Frederick Lang. Delta-24-RGD oncolytic adenovirus treatment downmodulates the key regulator of T-cell exhaustion TIM3 in malignant gliomas [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr LB-235. doi:10.1158/1538-7445.AM2017-LB-235