Estimation of the Viscosity of an Antibody Solution from the Diffusion Interaction Parameter

Understanding a monoclonal antibody's (MAb) physicochemical properties early in drug discovery is important for determining developability. Viscosity is important because antibodies with high viscosity have limited administration routes. Predicting the viscosity of highly concentrated MAb solutions is therefore essential for assessing developability. Here, we measured the viscosity and diffusion interaction coefficient (k_Diff) of 3 MAbs under 15 different formulation conditions (pH and salt) and evaluated correlations between parameters. We also used a computational approach to identify the key factors underlying differences in concentration-dependent curves for viscosity among the MAbs and formulation conditions. Results showed that viscosity increased exponentially at high concentrations, and that this concentration-dependency could be predicted from k_Diff. Attempts to set viscosity criterion for use by subcutaneous (SC) and intramuscular (IM) administration suggested that solutions with k_Diff greater than -20 mL/g may be candidates. Computational analysis suggested that the presence of a large negative charge in the complementarity determining region (CDR) is a major factor underlying the difference in concentration-dependency among the three MAbs under different formulation conditions. Because it is possible to predict the administration form of antibody solutions, determination of k_Diff at the early discovery stage may be essential for effective antibody development.