Activation of T Cells upon Treatment with Bispecific Antibodies Correlates with the Expression of Co-Inhibitory Receptors on Tumor-Infiltrating Lymphocytes in Human Lung Cancer

Abstract

ABSTRACT Introduction T cell bispecific antibodies (TCB) are designed to recruit and simultaneously activate T cells against target cells such as tumor cells expressing a particular surface antigen. However, it is currently unknown how immuno-modulatory mechanisms active in the tumor microenvironment such as the expression of T cell co-inhibitory receptors may influence the therapeutic effect of TCBs. Methods We performed a comprehensive phenotypic analysis of tumor infiltrating immune cells from lung carcinoma digests by multicolour flow cytometry. In particular, expression of T cell co-inhibitory and -stimulatory receptors was analyzed. Tumor digests were treated with catumaxomab, a TCB directed against CD3 and EpCAM. T cell activation and effector functions were assessed upon exposure to catumaxomab. Results CD8+ T cells in lung carcinoma showed a broad heterogeneity in expression of the T cell co-inhibitory receptors PD-1, Tim-3, CTLA-4, Lag-3 and BTLA. Tumor stage and nodal status correlated with number and intensity of expressed receptors. Upon exposure to catumaxomab, a considerable heterogeneity in T cell activation among different tumors was observed. Of note, T cells expressing high levels and multiple co-inhibitory receptors were more impaired in their activation and effector functions after treatment with catumaxomab indicating a higher level of exhaustion. In a further analysis of CD8+ TIL subsets we found that BTLA+ T cells expressed more additional inhibitory receptors than all other subsets, namely PD-1, Tim-3, CTLA-4 and Lag-3, whereas only a small part of PD-1+ T cells expressed another receptor. Tim-3+ T cells usually co-expressed PD-1, but multiple receptors were found only on a low number of cells. Conclusion In summary, our data suggest that the activity of TCBs is largely affected by the expression of T cell co-inhibitory receptors on tumor-infiltrating immune cells. Furthermore, these data provide a clinical rationale for combining bispecific antibodies with compounds which antagonize T cell exhaustion. Disclosure D. Thommen, J. Schreiner, P. Herzig, P. Mueller and A. Zippelius: received research funding from Roche Glycart; V. Karanikas: is employed by Roche Glycart. All other authors have declared no conflicts of interest.