Pathogen safety profile of a 10% IgG preparation manufactured using a depth filtration-modified process Deborah Barnette * , Nathan J. Roth, JoAnn Hotta, Kang Cai, Michelle Gall, Randy Hartwell, Jonathan D. Kent, Todd Willis Grifols Therapeutics Inc, 79 TW Alexander Drive, Research Triangle Park, NC 27709, USA article info Article history: Received 15 July 2011 Received in revised form 3 April 2012 Accepted 4 April 2012 Keywords: Gamunex Cloth filtration Depth filtration IGIV Viral safety Prion abstract Gamunex Ò -C is a highly purified liquid 10% IgG preparation manufactured by a process that includes caprylate precipitation and incubation, and chromatography steps. In the original process, caprylate precipitation was followed by cloth filtration to remove impurities. The highly porous cloth filter has since been replaced with a tight depth filter. The impact of this process modification on pathogen reduction and product is presented. Virus and prion reduction was determined under set-point conditions using scaled-down models of the manufacturing process, and at or outside operating limits to determine robustness. Product protein compositions before and after the process modification were compared directly using manufacturing data. Filtration through a tight depth filter substantially increased nonenveloped virus reduction, and virus reduction was maintained even when a compromised depth filter was used. In addition, prion reduction was improved by about three logs. The product IgG content, purity, and IgG subclass distribution remained comparable to the original cloth filtration process. The replacement of cloth filtration with depth filtration increased the pathogen safety margin of the manufacturing process without impacting the product composition. Ó 2012 The International Alliance for Biological Standardization. Published by Elsevier Ltd. All rights reserved. 1. Introduction Immunoglobulin G (IgG) was first isolated from pooled human plasma on a large scale in the 1940s using cold-ethanol fraction- ation [1,2]. Over time, additional purification steps were added, integrated with automation, quality control, and other good manufacturing practices to improve the safety, purity, and efficacy of the products [3]. The Gamunex Ò -C (IGIV 10% caprylate/chro- matography purified) process includes a “caprylate precipitation” step at low temperature that is followed by a filtration step to remove impurities and pathogens (Fig. 1). Initially, a reusable cloth filter was used but it has since been replaced with a tighter porosity single-use depth filter to selectively enhance pathogen removal while maintaining the protein purification function (Fig. 1). The current report describes the improved virus and prion reduction capability of the depth filtration-modified caprylate precipitation process, as well as the consistent product composition before and after the modification. 2. Materials and methods 2.1. Manufacturing process The Gamunex Ò -C manufacturing process has been described in detail elsewhere [4]. Briefly, Fraction II þ III paste produced via the Cohn-Oncley fractionation process is suspended in water and pH adjusted before the first addition of caprylate. The material in caprylate-1 (MIC-1) Suspension is then held to precipitate lipids and lipoproteins, aka “caprylate precipitation”. In the original process, the resulting precipitate was separated from the product stream by filtration through a reusable Freudenberg cloth filter with a nominal porosity of >1 mm to yield MIC-1 Filtrate. In the modified process, a tighter disposable cellulose ester depth filter pad (CUNO 90SP, Meriden, CT, USA) with a 0.2 mm nominal pore size is used. All steps downstream of MIC-1 Filtrate are the same in the original and modified processes. There is a second caprylate Abbreviations: IgG, immunoglobulin G; GamunexÒ-C, 10% IgG purified using caprylate and chromatography; MIC-1, material in caprylate-1; MIC-2, material in caprylate-2; BVDV, bovine viral diarrhea virus; HCV, hepatitis C virus; HAV, hepa- titis A; HIV-1, human immunodeficiency virus-1; LRV, log 10 reduction value; PPV, porcine parvovirus; PRV, pseudorabies virus; Reo3, reovirus type 3; TCID 50 , median tissue culture infective dose. * Corresponding author. Tel.: þ1 919 359 4601; fax: þ1 919 359 4280. E-mail address: deborah.barnette@grifols.com (D. Barnette). Contents lists available at SciVerse ScienceDirect Biologicals journal homepage: www.elsevier.com/locate/biologicals 1045-1056/$36.00 Ó 2012 The International Alliance for Biological Standardization. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.biologicals.2012.04.003 Biologicals 40 (2012) 247e253