Biopharmaceuticals are gaining interest in therapy due to their high target selectivity. Most of the recently approved biopharmaceuticals represent drugs that are produced by biotechnological processes involving recombinant DNA. Thus, this review article mainly focusses on protein therapeutics. However analogous considerations also apply for other large molecule therapeutics. As early approved blockbuster biopharmaceuticals run out of patent protection shortly, a growing interest in biosimilar production results in the need of proper analytical characterization and comparison of inventor and biosimilar. In contrast to small molecule drugs small variations in the production process may strongly impact the final biological. Thus, quality assurance of biopharmaceuticals results in much higher analytical effort compared to small molecules.
This review gives an overview on analytical methods for characterization of protein biologicals. Classical methods such as gel electrophoresis and liquid chromatography are summarized and complemented with state-of-the-art mass spectrometric investigations. Full molecule investigations of native or denaturized proteins as well as methods including digestion (middle-down and bottom-up) are discussed. Furthermore, literature on glycoprotein analysis using glycopeptide, released glycan and monosaccharide analysis is reviewed.