The influence of Arginine and counter-ions: Antibody stability during freeze-drying.

Amino acids, for example L-arginine, are used in lyophilisation as crystalline bulking, buffering, viscosity reducing or stabilising excipients. In this study, arginine was formulated with different counter ions (hydrochloride, citrate, lactobionate, phosphate, and succinate). A monoclonal antibody was investigated in sugar-free arginine formulations and mixtures with sucrose regarding to cake appearance and protein stability with respect to protein aggregation and fragmentation. Arginine hydrochloride formulations collapsed during the selected lyophilisation process, and partially crystallised during storage, but provided the best protein stability at low antibody concentration, followed by arginine succinate formulations. Arginine citrate/ phosphate/ lactobionate formulations resulted in amorphous elegant cakes, but lacked in protein stability. Increasing pH from 5.0 to 7.0 resulted in decreased protein stability. Addition of sucrose to the arginine formulations improved cake appearance and protein stability. Arginine phosphate with sucrose resulted in similar protein stability to the sucrose reference. At 2 mg/ml antibody, arginine hydrochloride (± sucrose) provided very good protein stabilising characteristics. Mixing sucrose with arginine hydrochloride/ lactobionate/ succinate were superior to pure sucrose. While 50 mg/ml antibody improved cake appearance, only arginine lactobionate provided sufficient protein stability next to sucrose. So, sugar-freearginine formulations were able to stabilise the antibody in lyophilisates in a comparable or better way than sucrose formulations depending on counter ion, specifically the hydrochloride and the lactobionate, and antibody concentration. Best protein stability was found for mixtures of arginine hydrochloride/ lactobionate/ succinate with sucrose.