“… 26 , 27 , 28 As many therapeutic proteins, such as fusion proteins etanercept, abatacept, atacicept, hormone erythropoietin (EPO), recombinant coagulation factor VIII, granulocyte macrophage colony stimulating factor, and others are both O-glycosylated and N-glycosylated. 19 , 29 , 30 , 31 , 32 , 33 , 34 The role of N-glycosylation in quality and safety of those protein drugs are well known. However, the effects of O-glycosylation on critical quality attributes of these therapeutic proteins are currently largely uninvestigated.…”