The effects of protein-protein interactions on in vitro and in vivo behavior of protein solutions

Protein-based therapeutics such as monoclonal antibodies (mAbs) and related fragments are increasingly attractive modalities to treat a variety of diseases due to the ability to engineer their biochemical and biophysical properties, streamlined manufacturing processes, minimal toxicity, and low immunogenicity/low risk of adverse side effects. Research in the methods used to deliver these treatments are limited when compared to small molecule drugs, as it is difficult to administer proteins orally and the high concentrations required for subcutaneous delivery are associated with high viscosities precluding syringe injection. Therefore, most protein therapeutics are delivered intravenously over long periods of time (>30 min) at dilute concentrations under medical supervision. Subcutaneous self-administration is a major objective in the field as it is expected to increase patient accessibility and compliance in addition to reducing pain and cost. Two common approaches under active investigation are 1) engineering the primary amino acid sequence for such traits as increased solubility and aggregation resistance, as well as 2) optimizing solution parameters for reduced viscosity via addition of excipients or optimizing manufacturing parameters. These approaches are unable to achieve stable protein solutions at concentrations sufficient for self-administration due to the dominant role of attractive forces at high concentration where even single amino acid mutations can drastically alter solution properties and thus solution optimization becomes protein-specific in nature. My overarching goals for this document are to systematically determine the dominant effects of protein-specific properties on this protein delivery technology in vitro and in vivo. Specifically, (1) investigate the role of protein-protein interactions on protein solution properties, and (2) investigate the effect of protein therapeutics can have on the immune system in vivo.