The In Vitro Biotransformation of the Fusion Protein Tetranectin-Apolipoprotein A1.

As more and more protein biotherapeutics enter the drug discovery pipelines, there is an increasing interest in tools for mechanistic drug metabolism investigations of biologics in order to identify and prioritize the most promising candidates. Understanding or even predicting the in vivo clearance of biologics and to support translational pharmacokinetic modeling activities is essential, however there is a lack of effective and validated in vitro cellular tools. Although different mechanisms have to be adressed in the context of biologics disposition, the scope is not comparable to the nowadays widely established tools for early characterization of small molecule disposition. Here, we describe a biotransformation study of the fusion protein tetranectin apolipoprotein A1 by cellular systems. The in vivo biotransformation of tetranectin apolipoprotein A1 has been described previously, and the same major biotransformation product could also be detected in vitro, by a targeted and highly sensitive detection method based on chymotrypsin digest. In addition, the protease responsible for the formation of this biotransformation product could be elucidated to be DPP4. To our knowledge, this is one of the first reports of an in vitro biotransformation study by cells of a therapeutic protein.