Antithrombin alfa is a recombinant human antithrombin developed as an anticoagulant treatment for people with hereditary antithrombin deficiency who are undergoing surgical or childbirth procedures (1). Marketed under the ATryn brand name by LFB SA (Les Ulis, France), antithrombin alfa was approved for use in adults by the US Food and Drug Administration (FDA) in February 2009 (2). Antithrombin alfa is expressed in the milk of transgenic goats and purified through a multistep downstream process encompassing both filtration and chromatography.…