Inactivation of highly potent regulatory T cells (Tregs) with TNFR2 antagonist antibodies as a novel cancer immunotherapy approach.

Abstract

e14020 Background: Regulatory T cells (Tregs) are considered a barrier to cancer immunotherapy success due to their suppression of antitumor immune responses. Both murine and human data support the development of a Treg inhibition approach to enhance various oncology treatments. In particular, therapies that eliminate TNFR2hi Tregs, which are highly abundant in human tumors, show favorable clinical responses. The restricted tissue distribution of human TNFR2, with very high TNFR2 expression, make this cell surface target highly desirable. Recent ovarian and AML human tumor data verifies the potency of TNFR2-expressing Tregs in vivo. TNFR2 also determines Treg fate: in vitro blockage in murine models prevents Treg development. Therefore, TNFR2 antagonism may be an effective, targeted way to inhibit Tregs and boost cancer immunotherapy efficacy. Methods: Monoclonal antibodies (moAbs) against human TNFR2 were produced using a hybridoma line and screened on fresh human CD4+ T cells from > 500 healthy human subjects. MoAb functional capacity and mechanism of action were assessed in in vitro human assays by incubating expanded human Tregs with moAb candidates. Inhibition of TNFR2 transcript signaling was one readout to verify identification of TNFR2 antagonistic antibodies. Results: Several moAbs were identified as TNFR2 antagonists that suppressed the baseline or induced CD4 proliferation. After incubation with human Tregs for 24 hrs, TNFR2 antagonists turned off NFkB signaling in Tregs, rapidly inhibiting proliferation and resulting in selective Treg death. Important transcription factors such as TRAF2, IL2R and Foxp3 were downregulated. Remaining Tregs appeared unaltered in surface markers but showed low TNFR2 expression. Conclusions: Select anti-TNFR2 moAbs can be identified to this receptor and safely inactivate human TNFR2hi Tregs. Antibody antagonism through TNFR2 may be a targeted method to deplete and inactivate these potent Tregs, providing a novel way to enhance the efficacy of cancer immunotherapies.