Innovative Pharmaceutical Stabilization and Formulation Processes for Protein Drugs and Their Impact on Sequence and Structure. Part: Analytics

Peptide and protein design for biopharmaceutical and food applications gained considerable attention in recent years. Numerous peptides and proteins are approved every year, however, their quality and long-term stability as e.g., a pharmaceutical product is still a matter of concern. Innovative methods in drug formulation were developed, including hot-melt extrusion and spray freeze drying, which have been tested to study their potential for protein stabilisation. Since the formulation procedures could also influence the features of the carried entity, it is also required to provide appropriate analysis methods to test stability, structural integrity, and activity of the peptide or protein cargo after formulation. In addition, many proteins carry post-translational modifications, such as disulfide bridges, which are crucial for the protein’s fold and specificity and should thus be sustained throughout the formulation process. To address both issues, the development of a bioanalytical workflow for the analysis of hot-melt lysozyme extrudates as well as an Edman sequencing protocol for determining the disulfide connectivity in peptides and proteins were investigated and reported in this chapter. The latter study included the establishment of suitable cysteine standards for sequencing and their examination in the context of suitable model peptides before investigating relevant functionally active representatives.