Use of microcalorimetry and its correlation with Size Exclusion Chromatography for rapid screening of the physical stability of large pharmaceutical proteins in solution

The utility of microcalorimetry as a rapid screening tool for assessing the solution stability of high molecular weight pharmaceutical proteins was evaluated using model recombinant antibodies, Protein I and Protein II. Changes in the transition midpoint, Tm, were monitored as a function of pH and/or in the presence of excipients, and results were compared with traditional accelerated stability data from samples that were analyzed by size exclusion chromatography (SEC). The data from microcalorimetry were well correlated with those from SEC for predicting both optimal solution pH as well as excipient effects on solution stability. These results indicate that microcalorimetry can be an efficient screening tool useful in identifying optimal pH conditions and excipients to stabilize pharmaceutical proteins in solution formulations.

During the past two decades, there has been a rapidly increasing interest in development and commercialization of protein-based therapeutics. One of the greatest challenges during development for such products is the stabilization of proteins in solution. To address this issue, many proteins are formulated as a lyophile that must be reconstituted with a suitable vehicle just prior to use. However, the preference for simpler administration procedures and reduced production costs make development of ready-to-use (RTU) solutions a particularly attractive approach for clinical and commercial drug product formulations, provided sufficient solution stability and adequate shelf life can be achieved. In addition, a large number of protein-based bulk drug substances are provided to development in solubilized form following purification, making identification of an appropriate buffer composition for storage and handling of the bulk protein an important step in the early development process. The studies required to support storage buffer recommendations and RTU solution development for protein pharmaceuticals can be timeconsuming and tedious and often require a significant amount of drug substance to conduct. The design of traditional solution stability studies involves storage of protein solutions of different concentrations in various buffer systems (with or without added excipients) under several stress temperature and/or lighting conditions.