Development and characterization of novel a TCRm antibody and its application as an immune checkpoint blocker

Abstract

Immunotherapy, the treatment of diseases via targeted immune system activation, has recently shown extraordinary success in clinical trials for multiple malignancies. In contrast to a routine therapeutic regimen for cancer, effective immunotherapies can stimulate the innate and adaptive immune system to marsh specific and durable responses against tumors. Immunotherapies come in many shapes and forms. Immune checkpoint blockade (ICB) is an example of immunotherapy that revolutionized the field of immuno-oncology. Considering the recent success of ICB therapies, the scientific community tried to discover new inhibitory molecules and pathways as a new target for cancer immunotherapy. Indeed, CD94/NKG2A receptor is an inhibitory checkpoint molecule with a high affinity for its ligand non-classical MHC-I, Qa-1b (mouse), or HLAE (human). The result of this interaction is often a suppression of activated lymphocytes, natural kills cells, and antigen-presenting cells, along with the up-regulation of inhibitory T cells. Thus, this dissertation's general goal is to better understand the nature of this interaction and develop a new therapeutic agent to unleash the suppressed immune system as a means of eliciting a more robust response. In other to reach out to this goal: First, we developed a single domain (VhH) TCR-like monoclonal antibody named EXX-1 with high affinity and selectivity for Qa-1b/Qdm complex. We evaluated the specificity and avidity effect of our monoclonal antibodies in an in-vitro assay. We used a commercially available monoclonal antibody to Qa-1b complex (clone 6a8.6f10.1a6) developed by Dr. Soloski's group (Johns Hopkins University, Baltimore, MD) as a positive control for our antibody. During this phase, we noticed that our commercial antibody (clone 6A8) only recognizes the Qa-1b molecule regardless of the presence or absence of the Qdm peptide. Thus, interaction NKG2A to its ligand couldn't be blocked as the presence of the QDM peptide is crucial for this interaction. However, EXX-1 can recognize a Qdm peptide expressed by the Qa-1b protein. We found that in the presence of EXX-1, Qa-1b/ Qdm interaction with CD94/NKG2A will be interrupted. This blockade caused higher immune cell (NK and CD8+ T cell) proliferation and increased tumor kill rates. Second, we tried to develop an in vivo model for this concept. Thus, we evaluated several mouse tumor models for the expression level of the Qa1b/Qdm complex. During this phase, we realized that this expression is highly dependent on the cytokines such as IFN-γ. We also observed tumor regression and therefore extended life span of the mice treated with EXX-1 (ES) compared to its isotype control. Third, we tried to enhance the efficacy of our therapy through. 1- Combination of EXX-1 with tumor vaccination, 2- Antibody dependent cellular cytotoxicity (ADCC). We observed tumor clearance in 40-45% of the mice treated with EXX-1 compared to its isotype. Moreover, we noticed that EXX-1 treated mice were develop a tumor specific immunity compared to isotype control treated groups.