Simple Hydrodynamic Molecular Weight Model for Rapid Assessment of Therapeutic Protein Oligomerization States in Formulation.

Therapeutic peptides and proteins form higher-order structures (HOS) including oligomeric forms in formulation, critical for drug efficacy, safety, and stability. To quickly assess protein oligomerization, dynamic light scattering (DLS) was applied to measure a series of protein standards with molecular weight (MW) range of 1.3-660 kDa, yielding translational diffusion coefficients (D_dls), which were corrected to D_corr using water diffusion data. A correlation between D_corr and protein monomeric MW, representing their hydrodynamic MW (MW_hd), was established as $log\left(D_{corr}\right)=-0.428log\left({MW}_{hd}\right)-5.412$ . This DLS/MW_hd model was subsequently applied to therapeutic protein formulations with monomeric MW ranging from 3.8 to 149 kDa. The resulting MW_hd values were several-fold greater than the corresponding monomeric MW of the glucagon-like peptide-1/2 (GLP-1/2) analogs, insulin analogs, and the monoclonal antibodies (mAbs) infliximab and bevacizumab, indicating varying degrees of oligomerization. The observed oligomerization states were largely consistent with those reported in literature. For insulin and mAb oligomers, pseudo-spherical diffusion coefficients (D_s) back calculated from the oligomer MW agreed within 6% of experimental D_corr values, except for the insulin dimer. Incorporation of Perrin's anisotropic correction reduced insulin dimer discrepancy from 9 to 5%. Overall, the established MW_hd model, incorporating a larger exponent of 0.428 that accounts for protein anisotropy, provides a rapid, non-invasive method to factually assess protein oligomerization in as-is formulations, aiding drug development and quality control. Minor discrepancies relative to size exclusion chromatograph (SEC) or prior biophysical studies may arise from experimental differences in protein concentration, oligomeric equilibrium, pH, excipients or modeling assumptions, warranting further investigation.