Engineered Antibody and Monobody Domains with T Cell Receptor-Like Selectivity for Tumor Associated Peptide-MHC Antigens

Citation

Hamdouche, Samy (2014) Engineered Antibody and Monobody Domains with T Cell Receptor-Like Selectivity for Tumor Associated Peptide-MHC Antigens. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/Z9WH2N02. https://resolver.caltech.edu/CaltechTHESIS:06062014-175608943

Abstract

Monoclonal antibody (mAb)-based therapeutics have established themselves as meaningful components of the treatment paradigm for a variety of tumors. However, since the approval of rituximab in 1997 as the first mAb-based therapy for cancer, there has been a paucity of novel, validated cancer targets for therapeutic intervention by mAbs. In effect, numerous challenges lie in the discovery of suitable extracellular or transmembrane antigens that permit the differentiation of tumor from healthy tissue. The adaptive immune system, though, mediates recognition of foreign antigens derived from the intracellular proteome by T cell receptor (TCR) binding to peptide-loaded major histocompatibility complex (pMHC) molecules. Because cancer is associated with large-scale alterations in the genome, there are a vast number of novel epitopes presented to the adaptive immune system. Although natural TCRs have exquisite functionality in distinguishing these foreign epitopes, and several tumor-reactive TCRs have, in fact, been characterized, the molecules themselves are poorly developable as therapeutic candidates. Thus, in order to enable TCR-like binding of a broader class of protein agents, this study explores the transfer of TCR binding domains to other mAb-based scaffolds, including the fibronectin-derived Fn3 and the IgG-derived 4D5 scaffolds. By using a combination of rational design and directed evolution to guide binding domain transfer, evidence for TCR-like binding was demonstrated for several engineered molecules. In addition to conferring binding functionality, the grafted TCR domains had a deleterious effect on the biophysical properties of these inherently robust protein scaffolds. Thus, this work provides novel insight into the objective of developing mAb-based agents with TCR-like binding specificity for pMHC antigens, informing future efforts to target the abundance of intracellular tumor epitopes.

Thesis Files