Characterization of IgG monomers & their aggregates

Characterization of IgG monomers & their aggregates

Determining the components, and their proportion, in a protein sample is essential for the improvement of candidate formulations and characterization of final formulations.

Introduction

In biopharmaceutical formulations one of the key factors that manufacturers need to understand is the propensity of their samples to aggregate. Aggregates in biologic drugs are undesirable for two reasons. They reduce the amount of active ingredient in the sample, thereby reducing efficacy, and they can stimulate immunogenic responses in the body. This in turn can lead to more rapid clearance of the drug and again reduce efficacy, or in some cases can lead to severe immune responses. Full characterization of protein drug samples is therefore necessary both for those developing formulations and those characterizing final products. It is therefore extremely important to have a technique which can both measure the amount of different protein aggregate components and identify and characterize each of them. In this way a sample can be fully characterized and understood.

Traditionally, the determination of such information has employed size exclusion chromatography (SEC). Using SEC, sample components can be identified by their molecular weights in a process that compares the retention volume of analyte molecules through a size exclusion column against that of a series of standards with known molecular weights. In addition, the relative amounts of each component can be simply extracted from the respective peak areas providing that a concentration detector is used to record the elution and the relevant extinction coefficients are known.