Mammalian cell-produced therapeutic proteins: heterogeneity derived from protein degradation.

•Mammalian cell-produced therapeutic glycoproteins are heterogeneous in nature.•Causes of product heterogeneity are highlighted.•Examples of protein degradation by non-enzymatic and enzymatic pathways are reviewed.•Strategies used for controlling protein degradation are described.•Possible development of host cell lines with minimal degradative properties is discussed.