Freeze/Thaw of IGG Solutions.

In this communication, the effect of mannitol and trehalose crystallization on the unfolding of IgG1 , a monoclonal antibody, in the frozen state with repeat freeze/thaw under different pH conditions was explored. Formulations were annealed at -20°C for 20hours five times (interrupted by freeze/thaw). This was done to induce excipient crystallization. Characterization of the frozen-thawed samples was performed by circular dichroism, particle analysis, and size exclusion chromatography. At a pH of 3, formation of insoluble and soluble aggregates was observed however, these could be reduced by the use of a surfactant. Cryoprotectant free formulations showed higher monomer content after freeze/thaw. At pH5, a single freeze/thaw cycle did not result in a significant increase in particle numbers. At pH range of 4-7 however, aggregate formation in the size range of 1-25 µm was observed after 5freeze/thaw cycles.