Considerations During Development of a Protein A-Based Antibody Purification Process

purification development for antibodies with affinity, hydrophobic-interaction, and ionexchange chromatography (1). Fahrner et al. discuss the importance of considering the optimal flow rate on protein A affinity chromatography and suggest that higher flow rates will reduce process time significantly without significantly affecting process capacity (2). Notwithstanding these good publications, the best arena for keeping abreast of developments in the field continues to be national and international conferences on the subject (for example, references 3–5). In this article, we draw a holistic picture of the different considerations involved in developing a protein A-based antibody purification process. These considerations are as diverse as operational limits (process time and flow rate), chemical– equipment compatibility considerations (stainless steel), and regulatory constraints (the source of raw materials). Since Rituxan appeared on the market, IDEC developed several other antibodies that are now in various stages of clinical testing. Because the pipeline of antibody products has expanded, the purification process development has been improved in several ways. The purification scheme for Rituxan included a protein A Sepharose FF capture step followed by ultrafiltration/diafiltration (UF/DF) concentration, anion exchange, and final formulation steps. We discussed the development of the Rituxan purification process at a recent conference (6). Important to that process are a wash to remove bovine IgG from harvested cell culture fluid during the protein A chromatography step and a test of the anion-exchange membrane adsorber to provide espite the initial “magic bullet” potential of monoclonal antibodies, the first antibody for the treatment of cancer was not approved by FDA until 1997 (Rituxan, from IDEC Pharmaceuticals Corporation and Genentech, Inc., a chimeric antiCD20 for non-Hodgkin’s lymphoma). Since the late 1990s, several other antibodies have won approval from FDA for indications as diverse as breast cancer (Herceptin from Genentech), respiratory syncytial virus (RSV) in children (Synagis from MedImmune, Inc.), and Crohn’s disease (Remicade from Centocor, Inc.). Several papers have detailed various aspects of developing a purification process for antibodies. Gagnon describes various practical aspects of Harish Iyer, Felicia Henderson, Eric Cunningham, James Webb, John Hanson, Christopher Bork, and Lynn Conley