Developing anti-p53/HLA-A*0201 T-cell receptor mimic antibodies for cancer immunotherapy

T-cell receptor mimic (TCRm) antibodies target a dual antigen epitope consisting of a peptide derived from an intracellular protein, and the major histocompatibility complex class I (MHC-I) molecule that presents the peptide at the cell surface. As traditional antibodies typically target cell surface or secreted antigens, TCRm antibodies advantageously expand the range of targetable antigens to include peptides derived from intracellular proteins. This thesis describes the development of TCRm antibodies targeting peptides that are derived from the wild type p53 protein and are presented by human leukocyte antigen (HLA)-A2. We further characterised the specificity and safety of the T1-116C TCRm antibody, which was the most extensively studied TCRm antibody in the laboratory prior to the start of this DPhil project. We showed that T1-116C labels primary AML and myeloma cells. We investigated the specificity of the T1-116C TCRm antibody for the p5365-73 peptide, RMPEAAPPV, by substituting each amino acid within the peptide individually, and showed that T1-116C recognises multiple tumour antigens. Using in silico analysis we identified 271 potentially cross-reactive peptides. We tested a panel of 25 peptides that are conserved in mice in vitro, showing that T1-116C binds peptides derived from a broad range of normal tissues. Despite these findings, in vivo testing of T1-116C cross-reactivity in human HLA-A2 transgenic mice demonstrated that T1-116C does not cause toxicity to normal mouse tissues. We also generated chimeric antigen receptors (CARs) for T-cell therapy using the single chain variable fragment of p53-targeting TCRm antibodies to provide the CAR specificity. We found that the CAR derived from T2-2A, a TCRm antibody that targets the p53187-197 peptide, GLAPPQHLIRV, demonstrated superior specificity for target peptide-HLA-A2 tetramers and cell lines to the T1-116C CAR. Through these studies, the T2-2A TCRm antibody has emerged as a potential therapeutic agent when used in the CAR format.