Effects of additives on the stability of recombinant human factor XIII during freeze-drying and storage in the dried solid

Freeze-drying is often used to improve storage stability of therapeutic pro teins. In order to obtain a product with optimal storage stability it is im portant to understand the mechanisms by which solutes protect the protein a gainst freeze-drying-induced stresses and also against damage induced durin g subsequent storage. The objective of the current study was to examine the importance of various mechanisms proposed to account for acute and long-te rm storage stability using recombinant human Factor XIII (rFXIII)(4) as a m odel protein. Initially, for acute stability during freeze-drying, it was f ound that solutes which formed an amorphous phase stabilized rFXIII to a gr eater degree than solutes which crystallized during freeze-drying. However, only amorphous solutes which were able to hydrogen bond to the protein, an d thus preserve the native protein structure in the dried solid, provided o ptimal acute stability. Thus, in addition to forming an amorphous phase, it was also important to possess the ability to hydrogen bond to the protein. Long-term storage stability was found to be optimal in the presence of sol utes which formed and maintained amorphous phases with T-g values above the storage temperature and which also preserved the native protein structure during freeze-drying. Solute crystallization during storage compromised sto rage stability. (C) 1998 Academic Press.