Abstract 2633: Identification of novel T cell co-inhibitory and co-stimulatory receptors from screening a comprehensive library of extracellular proteins

Abstract

Abstract Antibody blockade of immune checkpoint regulators such as PD-1 and CTLA-4 has been shown to be an effective cancer treatment strategy; however, a large percentage of patients still do not respond to existing therapies. Discovery of additional immune checkpoints and co-stimulatory receptors and development of antibody therapeutics against them are likely critical to address this unmet patient need. We generated a comprehensive library of essentially all human extracellular proteins and have used this library to screen for new agents that modulate the function of various immune cell subsets both in vitro and in vivo. Using primary T effector and regulatory T cells, we have identified new targets that modulate the activities of these T cell populations in vitro and are currently evaluating these proteins as possible targets for cancer immunotherapy. In addition, we have expressed a subset of the library in three different models of tumor-bearing mice and have identified several proteins that modulate anti-tumor immunity in vivo. Several of the proteins identified in these screens have activity across multiple primary cell and in vivo tumor model screens and we are rapidly evaluating them as possible targets for novel immuno-oncology therapeutics. Taken together, we believe that we have developed robust in vitro and in vivo platforms that will allow us to discover novel cancer immuno-therapeutics that will help address the needs of cancer patients that fail to respond to current immunomodulatory therapies. Citation Format: Arthur Brace, Nathan Sallee, Justin Chou, Lindsay Garrenton, Diana Chen, Ryan Liang, Greg Kemper, David Yang, Marina Jaquez, Janine Powers, Mikayel Mkrtichyan, Thomas Brennan, Luis Borges. Identification of novel T cell co-inhibitory and co-stimulatory receptors from screening a comprehensive library of extracellular proteins [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2633. doi:10.1158/1538-7445.AM2017-2633