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The blocking model theory with consideration of the multilayer membrane structure elucidates "Planova™" virus removal filter performance

Jun 16, 2022

June 16, 2022
Asahi Kasei Medical Co., Ltd.
Asahi Kasei Medical Corporation is pleased to announce that research findings of the blocking model theory elucidated a more rigorous verification of the filtration behavior of "Planova™" virus removal filter.

Asahi Kasei Medical is the global market leader in virus filtration, with its "Planova™" having an unrivaled 30-year history of trusted use in the production of biotherapeutics. We aim to provide "Assurance Beyond Expectation" to ensure product safety and manufacturing efficiency for therapeutics within the biopharmaceutical industry in the form of innovative yet exceptionally reliable purification consumables, equipment and support services.

"Planova™" effectively removes viruses by a size-exclusion mechanism without denaturing proteins. However, virus filtration behavior is not adequately described by the equations and analysis methods of the conventional four blocking models, i.e., complete blocking, standard blocking, intermediate blocking and cake filtration models. The assumptions of the conventional blocking model, i.e., the membrane structure consisting of a single active layer with single pore size, are not applicable for virus removal filters.

For high filterability virus filter behavior, a modified approach is proposed using a generalized equation derived from the characteristic form of the blocking model with consideration of the multilayer membrane structure with pore size distribution (Manabe model). As a result, this generalized equation rigorously shed light on the actual filtration behavior and verified the multilayer membrane structure model proposed from the initial stages of development of "Planova™". The Manabe model is vital for explaining the stable filtration of virus removal filters.

This study enables detailed verification of virus removal filter performance to contribute to basic research and biopharmaceutical manufacturing. Asahi Kasei Medical will continue to contribute to the greater safety of biotherapeutic products by developing high-quality and high-performance products in accordance with market needs while proactively investing in manufacturing facilities.

The article "Analysis of filtration with virus removal filters using the characteristic form of blocking model" has been published in Biochemical Engineering Journal on May 2, 2022. On publication, the paper has been freely available online at
Fig. 1. Schematic representation of virus filter with multiple layers of membrane with pore size distribution and protein product smaller than the pore sizes (r1 and r2) and particles targeted for removal larger than the small size pore size (r1) (Manabe model).