Regulatory T cells have a critical role in the maintenance of immune homeostasis in mice and man. However, despite their role in maintaining host integrity, their function is known to be hijacked in the context of cancer. The murine and human tumour microenvironment actively recruits regulatory T cells bearing features of activation such as upregulation of the high affinity IL2Ra (CD25) and the immune-regulatory receptor CTLA-4. In mice, anti-CTLA-4 antibodies are able to promote depletion of Tregs and enhanced tumour control whilst in humans this remains less clear. That said, in human cancers, the number of tumour infiltrating regulatory T cells and their spatial distribution with regards to effector T cells has been negatively associated to patient outcomes, underscoring their negative role in anti-tumour immunity and the need for tools that tamper with their function and number. In this talk I will discuss the role of regulatory T cells in the context of cancer, as well as old and new strategies to target this compartment including the development of a new CD25-targeting Treg depleting antibody for mice and man.

Citation Format: Sergio Quezada. Targeting regulatory T cells in cancer: From mechanisms to new therapies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr PL04-02.