Novel drug candidates are continuously being developed
to combat
the most life-threatening diseases; however, many promising protein
therapeutics are dropped from the pipeline. During biological and
industrial processes, protein therapeutics are exposed to various
stresses such as fluctuations in temperature, solvent pH, and ionic
strength. These can lead to enhanced protein aggregation propensity,
one of the greatest challenges in drug development. Recently, ionic
liquids (ILs), in particular, biocompatible choline chloride ([Cho]Cl)-based
ILs, have been used to hinder stress-induced protein conformational
changes. Herein, we develop an IL-based strategy to predict protein
aggregation propensity and thermodynamic stability. We examine three
key variables influencing protein misfolding: pH, ionic strength,
and temperature. Using dynamic light scattering, zeta potential, and
variable temperature circular dichroism measurements, we systematically
evaluate the structural, thermal, and thermodynamic stability of fresh
immunoglobin G4 (IgG4) antibody in water and 10, 30, and 50 wt % [Cho]Cl.
Additionally, we conduct molecular dynamics simulations to examine
IgG4 aggregation propensity in each system and the relative favorability
of different [Cho]Cl-IgG4 packing interactions. We re-evaluate each
system following 365 days of storage at 4 °C and demonstrate
how to predict the thermodynamic properties and protein aggregation
propensity over extended storage, even under stress conditions. We
find that increasing [Cho]Cl concentration reduced IgG4 aggregation
propensity both fresh and following 365 days of storage and demonstrate
the potential of using our predictive IL-based strategy and formulations
to radically increase protein stability and storage.