Still today, high-concentration protein formulations are often developed based on high-throughput experimental screening approaches. Although likely delivering working formulations, these approaches do not lead to a deep/mechanistic understanding of the protein phase behavior in solution. Within this work, we thus optimized and enhanced a recent approach for an initial low effort selection of potential excipients and excipient mixtures to be used in high-concentration protein formulations. This approach considers both: molecular interactions and thermodynamic determinants to access the phase behavior of the proteins in solution, as well as pharmaceutical engineering boundaries (such as osmotic pressure and osmolality) to deliver on optimal formulation conditions. Water activity coefficient γW-calculations (used to describe the protein environment in solution), unfolding temperature (conformational stability) and protein-protein interactions (colloidal stability) are used as determinants. Amino acids (20 proteinogenic amino acids), selected amino acid mixtures, as well as mixtures of amino acids and trehalose (l-arginine-trehalose; l-histidine-trehalose) are considered as model excipients. The approach is extends by studying the long-term stability of the predicted formulation conditions for a γ-globulin from human blood and denosumab. The results reveal, that by combining protein-specific experiments as well as model-based studies for the selection of excipient mixtures in high concentration protein formulations, the effort as well as the resource requirements can be reduced significantly.
Keywords: Aggregate fraction; Aggregation temperature; Amino acids; Formulation design; IgG antibody; L-arginine; L-histidine; Potential excipient mixture; Second osmotic virial coefficient; Solution osmolality; Sugar; Trehalose; Unfolding temperature; Water activity.
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