Developing the Next Generation of Universal Immune Receptors

Chimeric antigen receptor (CAR) T cell therapy has produced impressive clinical results in the treatment of human cancers; however, their broad use is limited due to the restriction of targeting to a single tumor associated antigen (TAA), as well as the inability to control effector function post-infusion. We hypothesized that these limitations can be addressed through the development of a receptor system that dissociates TAA targeting and T cell signaling. These receptors, termed universal immune receptors (UIRs), function through the binding of an extracellular adapter domain which acts as a bridge between intracellular T cell signaling domains and a soluble TAA targeting ligand (TL). This modular receptor design allows for dose-control of effector function, as well as the ability to target multiple antigens with a single receptor. In this thesis we describe the preclinical development of two novel UIRs, each designed with components that permit unique functionalities. First, we detail the development of a UIR based on the SpyCatcher/SpyTag protein bioconjugation system. We hypothesized that genetically engineering T cells to express an immune receptor containing the SpyCatcher protein as its extracellular domain would allow for covalent loading of SpyTag labeled TLs. We demonstrate that covalent loading of the receptor does occur with the addition of SpyTag-labeled TLs, and these new receptor architectures are capable of redirecting T cells against a range of TAAs, either individually or simultaneously, in a dose-dependent manner. Additionally, dose-controlled effector function was demonstrated in vivo. Many UIRs are comprised of components derived from non-human proteins or use TL-tags that have never been clinically injected. To address these potential issues, we developed a UIR comprised of an extracellular humanized scFv that binds the clinically validated positron emission tomography (PET) imaging agent DOTA. Our preliminary data shows that T cells expressing the αDOTA receptor can be redirected against multiple TAAs through the use of DOTA-conjugated clinical grade antibodies. Additionally, potency of the T cell response can be titrated by alterations to the DOTA molecule or through chelation of various metals to DOTA. Our results suggest that with further assessment the DOTA UIR is uniquely poised for clinical translation