(381b) Tumor Targeting Fibronectin Domains

The ability to potently and specifically target tumor cells is valuable for many approaches to oncology diagnostics and therapeutics. Fibronectin domains provide multiple advantages over traditional antibody-based approaches including small size for in vivo imaging; facile cysteine- and amine-based chemical conjugation for attachment of imaging agents, drug payloads, nanoparticles, etc.; single-domain architecture for construction of protein fusions; production in bacterial culture; and often improved stability and solubility. We have developed a fibronectin domain engineering platform using synthetic library design, magnetic- and fluorescence-activated cell sorting via yeast surface display, and affinity maturation by directed evolution. Using this system, we have engineered picomolar to nanomolar affinity binders to a variety of tumor markers including epidermal growth factor receptor, carcinoembryonic antigen, and CD276. Bacterial production, fluorophore conjugation, and protein fusion production have been demonstrated. Insights gained from protein engineering will be presented as well as utility of the engineered domains.