Control of leached beta-glucan levels from depth filters by an improved depth filtration flush strategy

Beta-glucans are polysaccharides of D-glucose monomers linked by (1-3) beta-glycosidic bonds, are found to have a potential immunogenicity risk in biotherapeutic products, and are labeled as process contaminants. A common source of beta-glucans is from the cellulose found in traditional depth filter media. Typically, beta-glucan impurities that leach into the product from the primary clarification depth filters can be removed by the subsequent bind-and-elute affinity chromatography capture step. Beta-glucans can also be removed by a bind-and-elute cation exchange chromatography step, which is useful for removing beta-glucans introduced by a post-Protein A depth filtration step. However, the increasing prevalence of flowthrough polishing chromatography poses a challenge for beta-glucan removal due to the lack of any bind-and-elute chromatography steps after the post-Protein A depth filter. In this work, a depth filter flush strategy was developed to control beta-glucan leaching into the product pool. Different loading conditions for the depth filtration and subsequent chromatography steps were evaluated to determine the robustness of the optimized flush strategy. Carry through runs demonstrated greater than two-fold reduction in beta-glucan levels using the optimized wash as compared to standard filter flush conditions.