Owing to their high clinical success rate, advancements in biotechnology, and increased understanding of disease mechanisms, therapeutic antibodies have become an important modality for the treatment of many diseases. Therapeutic antibodies are engineered and recombinantly produced immunoproteins that specifically recognize cell surface proteins to, for example, block proliferation signaling or activate and target immune cells toward tumor cells. In addition to having high specificity and affinity towards their intended target, therapeutic antibodies must exhibit low aggregation propensity, high thermal and colloidal stability, and high solubility to ensure efficient drug manufacturing, storage, and administration.

Recent reports have shown the correlation between antibody display level achieved on mammalian cell surface and the biophysical properties of the antibody. To facilitate the high-throughput selection of developable antibodies, a novel mammalian display platform utilizing a Bxb1 integrase-based landing pad in Chinese hamster ovary (CHO) cells was developed in this thesis. As the primary limitation of mammalian display is its limited library size, the genomic integration efficiency of the developed platform was substantially improved by enhancing the nuclear localization of Bxb1 integrase. To provide further evidence supporting the ability of mammalian display to distinguish between antibodies with differing biophysical properties, the correlation between these properties and the display level on mammalian cells was assessed using 37 clinical-stage antibodies. Additionally, the applicability of the platform was demonstrated by improving the biophysical properties of two antibodies using both rational and random mutagenesis strategies. Finally, to overcome the stable genomic integration bottleneck, a method for inducing random mutations near the complementary determining regions of the antibody in situ was developed. This was achieved by incorporating G-quadruplex structures in the antibody gene and coupling somatic hypermutation with mammalian display.

As demonstrated in this thesis, this novel mammalian display platform can be adopted by biopharmaceutical laboratories to discover and engineer antibodies with favorable biophysical properties.