期刊
JOURNAL OF PHARMACEUTICAL SCIENCES
卷 107, 期 1, 页码 42-56出版社
ELSEVIER SCIENCE INC
DOI: 10.1016/j.xphs.2017.09.003
关键词
amorphous; deamidation; dehydration; freeze drying/lyophilization; formulation; peptides; physical characterization; protein formulation; solid state Stability; acid/base
Role of water in chemical (in) stability is revisited, with focus on deamidation in freeze-dried amorphous proteins and peptides. Two distinct patterns for deamidation versus water have been reported, that is, a consistent increase in rate constant with water, and a hockey stick etype behavior. For the latter, deamidation is essentially independent of water at lower water contents and accelerates when water content increases above a threshold value. Two simple kinetic models are developed to analyze literature-reported relationships between water content and deamidation rate constants. One model is based on catalytic role of water clusters in enabling proton transfer, which is a critical reaction step. Water clusters are formed when water content increases above a threshold value, while unclustered (and less catalytically-active) water molecules are predominant at lower water levels. The second model considers the dual role of water, as both a destabilizer via catalysis and a stabilizer of protein native structure. Considering that both models emphasize the importance of local structure and that local structure is intrinsically related to fast (and non-cooperative) relaxation modes, it is plausible to expect correlations between local mobility, such as beta-relaxation, and amorphous chemical instability. (c) 2018 American Pharmacists Association (R). Published by Elsevier Inc. All rights reserved.
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