Several case studies of QbD principles applied to formulation robustness of therapeutic monoclonal antibodies (mAb) have been described recently in the open literature and at conferences. These examples have shown elegantly the translation of QbD concepts into practice, but have generally dealt with relatively stable molecules and simple formulations. This presentation will describe a case study of a non-mAb protein susceptible to oxidation and aggregation illustrating how a QbD-inspired approach was applied to demonstrate compositional robustness and container closure compatibility with a new fixed needle prefilled syringe.