Immunoaffinity capture coupled with capillary electrophoresis - mass spectrometry to study therapeutic protein stability in vivo.

Protein engineering is at an all-time high in biopharmaceutics. As a result, absorption, distribution, metabolism and excretion (ADME) of proteins has become more important to understand in the context of engineering strategies to optimize therapeutic properties of potential lead constructs. Immunoaffinity capture coupled with a newly developed capillary electrophoresis - mass spectrometry (CE-MS) system was used to characterize intact protein mass analysis of a wild type Fc-FGF21 construct and a sequence re-engineered Fc-FGF21 construct from an in vivo study. A number of truncated forms were observed and the time courses of the various proteolytic products were identified and compared between the two constructs. The abundances of the intact and truncated forms were used to provide the basis to semi-quantify ADME properties of the two protein forms. The use of this immunoaffinity capture followed by CE-MS based intact mass analysis workflow provided a qualitative and quantitative analysis of the pharmacokinetic profiles of the two proteins. The platform presented here holds great potential in characterization of the ADME properties of proteins.