The role of formulation in insulin comparability assessments

The concept of comparability can be applied when changes are made to manufacturing processes for biotechnology products subsequent to pivotal clinical trial studies. For many process changes, comparability can be demonstrated based entirely on relevant in vitro data provided that a detailed knowledge of the process/product exists, suitable analytical methodology is employed, and historical data are available for the assessment. Insulin provides an excellent model system to illustrate many important considerations when dealing with comparability exercises for biotechnology products. The physicochemical properties of insulin demonstrate the numerous chemical reactions and physical transformations that are exclusive to proteins. These properties are heavily influenced by formulation conditions and must be carefully evaluated when process changes are made. In addition, physical and chemical testing performed on representative formulations can provide valuable insight when assessing the comparability between pre- and post-change materials. This paper reviews our experience with manufacturing changes involving insulin emphasizing the important role of formulation in the comparability exercise for protein biopharmaceuticals.