Repligen Corporation is a bioprocessing company. The Company is focused on the development, manufacture and commercialization of products used to improve the interconnected phases of the biological drug manufacturing process. The Company's portfolio includes protein products, chromatography products, and filtration products. It provides Protein A ligands, a component of Protein A chromatography resins (media) used in the purification of virtually all monoclonal antibody (mAb)-based drugs on the market or in development. Its chromatography portfolio includes various products used in the downstream purification and quality control of biological drugs. Its OPUS pre-packed chromatography columns (PPCs) are used in the purification of clinical-stage biologics. Its filtration products include XCell Alternating Tangential Flow (ATF) Systems and Sius tangential flow filtration (TFF) cassettes. Sius TFF cassettes are used to concentrate clinical and commercial-stage biologic drugs.