Mechanistic studies of glass vial breakage for frozen formulations. II. Vial breakage caused by amorphous protein formulations.

In an accompanying article we have described parameters that influence vial breakage in freeze-thaw operations when using crystalizable mannitol formulations, and further provided a practical approach to minimize the breakage in manufacturing settings. Using two diagnostic tools-thermal mechanical analysis (TMA) and strain gage, we investigated the mechanism of mannitol vial breakage and concluded that the breakage is related to sudden volume expansions in the frozen plug due to crystallization events. Glass vial breakage has also been observed with a number of frozen protein formulations consisting of only amorphous ingredients. Therefore, in this study, we applied the methodologies and learnings from the prior investigation to further explore the mechanism of vial breakage during freeze-thaw of amorphous protein products. It was found that temperature is a critical factor, as breakage typically occurred when the products were frozen to -70 degrees C, while freezing only to -30 degrees C resulted in negligible breakage. When freezing to -70 degrees C, increased protein concentration and higher fill volume induced more vial breakage, and the breakage occurred mostly during freezing. In contrast to the previous findings for crystallizable formulations, an intermediate staging step at -30 degrees C did not reduce breakage for amorphous protein formulations, and even slightly increased the breakage rate. The TMA profiles revealed substantially higher thermal contraction of frozen protein formulations when freezing below -30 degrees C, as compared to glass. Such thermal contraction of frozen protein formulations caused inward deformation of glass and subsequent rapid movement of glass when the frozen plug separates from the vial. Increasing protein concentration caused more significant inward glass deformation, and therefore a higher level of potential energy was released during the separation between the glass and frozen formulation, causing higher breakage rates. The thermal expansion during thawing generated moderate positive strain on glass and explained the thaw breakage occasionally observed. The mechanism of vial breakage during freeze-thaw of amorphous protein formulations is different compared to crystallizable formulations, and accordingly requires different approaches to reduce vial breakage in manufacturing. Storing and shipping at no lower than -30 degrees C effectively prevents breakage of amorphous protein solutions. If lower temperature such as -70 degrees C is unavoidable, the risk of breakage can be reduced by lowering fill volume.