Abstract B18: Novel treatment of cutaneous T cell lymphoma: Targeting TNFR2, an oncogene and marker of potent Tregs, with anti-TNFR2 antibodies (2018)

Abstract Background: Tumor necrosis factor receptor 2 (TNFR2, or TNFRSF1B) is a lymphoid marker of the most potent regulatory T cell (Treg) subtype and a commonly expressed oncogene in human tumors. TNFR2 Tregs are also enriched in the tumor microenvironment. Recently, TNFR2 antagonistic antibodies have been made that inhibit NFkB-driven growth through the TNFR2 receptor. These antagonists have shown both Treg and tumor inhibition with specificity for the tumor microenvironment (Science Signaling 2017). Cutaneous T cell lymphoma (CTCL) currently has few effective treatments. Recent data shows that TNFR2 is a candidate oncogene in CTCL with recurrent point mutations and gain of function alteration of TNFR2, resulting in abnormal expression of TNFR2 on CD4+CD26- tumor cells (Nature Genetics 2015). We studied the effectiveness of TNFR2 antagonistic antibodies for direct CTCL tumor killing, direct Treg killing and ability to unleash effector T cell (Teffector) proliferation. Stage IV CTCL (Sézary syndrome) subjects with failure on diverse drug regimens were recruited to understand in vitro the effectiveness of adding TNFR2 antagonism to the treatment regimen to restore immune balance. Methods: We designed monoclonal antibodies to target the TNFR2 oncogene and directly kill human tumor cells. TNFR2-directed antibodies were screened for their ability to induce the death of leukemic cells in patients with Sézary syndrome on a diversity of prior treatment regimens, as well as their ability to induce killing of tumor-associated Tregs and induce Teffector proliferation. Treg tumor specific killing and Teffector induced proliferation. Studies were performed in vitro on sorted CD4+CD26- Sézary cells or V-beta specific populations when a tumor was typed. Results: Baseline blood samples from patients with CTCL showed significant burdens of tumor cells within the CD26- subset of CD4 cells, averaging 45-95% of this cellular subfraction, in contrast to control blood cells demonstrating on average 18% CD26- cells. In CTCL subjects, numbers of Tregs (CD4+CD25hiFoxp3) were also elevated at baseline (CTCL vs Control, 11% vs 7%, p&amp;lt; 0.05), numbers of Teffectors were depressed (CTCL vs Control, 3% vs 8%, p&amp;lt; 0.05), and Treg/Teffector ratios were abnormally elevated (CTCL vs Control, 8% vs 1%, p&amp;lt; 0.05). Remarkably, regardless of the underlying therapy being used in vivo, TNFR2 antagonism showed dose responsive killing of the tumor cells within the CD26- fraction of peripheral CD4 T cells. TNFR2 antibody antagonism also showed specificity for the cells of the tumor over CD26- cells from paired controls. In vivo treatment of CTCL subjects with an antiproliferative agent such as methotrexate hindered TNFR2 antagonism driven killing, demonstrating the specificity of TNFR2 antagonism for rapidly proliferating cells, which may explain why this antibody-directed immune intervention has tumor microenvironment specificity. TNFR2 antagonism was also studied in the same subjects in the context of the impact on killing tumor-associated Tregs and enhancing Teffector mediated proliferation. In dose response experiments in vitro, TNFR2 antagonism had the desired dual effect of potent Treg killing combined with potent unleashing of Teffector proliferation in 48-72 hours. Conclusions: TNFR2 is a recurrent genomic gain alteration in CTCL that can potentially be targeted to directly stop the growth of tumor cells by antibody-induced cell death. The recently discovered TNFR2 oncogene is also expressed on many other human tumor cells, including in colon cancer, multiple myeloma, renal cell carcinoma, Hodgkin’s lymphoma, ovarian cancer, and non-cutaneous T cell lymphomas. This feature makes TNFR2 an advantageous molecular target for direct tumor killing. TNFR2 antagonism also provides the ability to eliminate the potent Tregs of the tumor microenvironment and unleash Teffector proliferation. Citation Format: Heather Torrey, Audrey Defusco, Danielle Baum, Ziba Rhabar, Michael Khodadoust, Youn H. Kim, Denise L. Faustman. Novel treatment of cutaneous T cell lymphoma: Targeting TNFR2, an oncogene and marker of potent Tregs, with anti-TNFR2 antibodies [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 B18.