Development of highly concentrated protein formulations and evaluation of absorption kinetics after subcutaneous administration

Over the past several decades, protein therapeutics, and monoclonal antibodies (MAbs) have contributed to better therapeutic success in a wide range of diseases. Especially formulations for subcutaneous administration are gaining in importance and represent one of the most significant areas in the field of pharmaceutical industry. Subcutaneous administration presents with many advantages compared to intravenous administration, however, there are many lingering technological challenges in terms of preparation of highly concentrated protein formulations intended for subcutaneous dosing. Particularly the protein stability and appropriate viscosity should not be overlooked, considering it may otherwise result in a limited syringeability. Thus, the initial objective of the proposed research work, will be the identification of novel excipients for reducing the viscosity of formulations for subcutaneous administration. At the beginning, promising new excipients will first be identified through the computational screening and subsequently synthesized. The most suitable excipients will then be incorporated in highly concentrated formulations and evaluated in terms of protein stability and viscosity. Simultaneously, new depot systems for controlled release of proteins with limited duration of action will be established and characterized for physico-chemical properties and biological acceptability. In addition, a novel in vitro absorption model will be developed for the purpose of studying the subcutaneous absorption kinetics of selected highly concentrated formulations. The bioavailability and absorption rate constant will be predicted based on the estimated in vitro diffusion and convection processes, which were highlighted as two main biological mechanisms of the subcutaneous protein absorption. The best performing in vitro formulations will be chosen for the in vivo study, which will be the basis for the extensive in silico modeling of the pharmacokinetics (PK) of subcutaneously administered MAbs. Through the development of a population PK model, the most important factors governing PK of protein drugs will be identified. A more detailed model of subcutaneous absorption of macromolecules will be developed through mechanistic physiologically-based pharmacokinetic modeling. The in vivo absorption data analyzed by PK modelling will be related with the results from in vitro testing. Namely, the diffusion and convection parameters of the same formulations obtained in the in vitro study will be compared with the absorption rate constants and fraction of the absorbed dose in vivo. The predictive in vitro in vivo correlation will be established for future forecasting of protein absorption kinetics. We anticipate that the study will have an academic, as well as practical and economic impact, with the direct applicability into the current setting of the pharmaceutical industry. The results will contribute to a deeper understanding about protein formulations for subcutaneous administration, as well as mechanisms of subcutaneous absorption process. Our project will contribute to optimized production costs through the enhanced absorption screening for new potential lead drugs, upgraded predictive ability of the absorption models, and reduced necessary animal testing. This project will be a steppingstone for the future development of increasingly complex drug formulation systems.