Assessing the impact of viscosity-lowering excipients on liquid-liquid phase separation for high-concentration monoclonal antibody solutions

Abstract

Microfluidic Modulation Spectroscopy (MM-IR) was used to determine the secondary structure of four different monoclonal antibody (mAb) formulations after a liquid-liquid phase separation (LLPS) event.

The analysis was done to see if the LLPS event caused any structural changes to the protein. The results showed that by MMS (MM-IR) spectra for all four formulations were identical, which indicated no observable changes in the secondary structure of the mAbs. This finding was crucial because it suggested that the phase separation did not disrupt the protein's folding or conformation. The study concluded that the LLPS was a reversible thermodynamic process that did not negatively impact the IgG structure or its functional integrity.

This non-disruptive nature of LLPS on protein structure was further supported by the consistent ratio of beta-sheets to alpha-helical structures across all formulations. This implied that MMS (MM-IR) spectroscopy helped confirm that the LLPS could be a concentrating technique for mAb formulations without compromising the protein's bioactivity.

While CD could have been used for this experiment,  MMS was the preferred method to avoid the spectral interference caused by their specific buffer formulation.