Abstract A21: Activation of 4-1BB on liver myeloid cells triggers hepatitis via an interleukin-27 dependent pathway

Purpose: Agonist antibodies targeting the T cell co-stimulatory receptor 4-1BB (CD137) are among the most effective immunotherapeutic agents across multiple preclinical models of cancer. In the clinic, however, development of these agents has been stymied by dose-limiting liver toxicity. Lack of knowledge of the mechanisms underlying this toxicity has limited the potential to separate 4-1BB agonist driven anti-tumor immunity from hepatotoxicity. Experimental Design: The capacity of 4-1BB agonist antibodies to induce liver toxicity was investigated in immune competent mice, with or without co-administration of checkpoint blockade, via measurement of serum transaminase levels, through imaging of liver immune infiltrates, and via qualitative and quantitative assessment of liver myeloid and T cells via flow cytometry. Knockout mice were used to clarify the contribution of specific cell subsets, cytokines and chemokines. Results: We find that activation of 4-1BB on liver myeloid cells is essential to initiate hepatitis. Once activated, these cells produce interleukin-27, which is required for liver toxicity. CD8 T cells infiltrate the liver in response to this myeloid activation and mediate tissue damage triggering transaminase elevation. FoxP3+ regulatory T cells limit liver damage and their removal dramatically exacerbates 4-1BB agonist hepatitis. Co-administration of CTLA-4 blockade ameliorates transaminase elevation, whereas PD-1 blockade exacerbates it. Loss of the chemokine receptor CCR2 blocks 4-1BB agonist hepatitis without diminishing tumor-specific immunity against B16 melanoma. Conclusions: 4-1BB agonist antibodies trigger hepatitis via activation of myeloid cells to produce Interleukin-27. Co-administration of CTLA-4 and/or CCR2 blockade may minimize hepatitis but yields equal or greater antitumor immunity. Citation Format: Ashvin R. Jaiswal, Todd Bartkowiak, Casey R. Ager, Renee Chin, Chao Hsien Chen, Pratha Budhani, Midan Ai, Matthew J. Reilley, Manu M. Sebastian, David Hong, Michael A. Curran. Activation of 4-1BB on liver myeloid cells triggers hepatitis via an interleukin-27 dependent pathway [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2017 Oct 1-4; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2018;6(9 Suppl):Abstract nr A21.