Abstract: To provide a method for purifying an antibody to a sufficient degree of purity for therapeutic use in humans by removing impurities contained in a solution efficiently while reducing production cost and the purification period in the purification of the antibody. It was found that an antibody can be reliably purified to a high degree of purity by an activated carbon material, regardless of the amounts or species of impurities co-present, and that high viral clearance can be attained reliably. Based on the finding, a treatment with an activated carbon material could be used in place of AEX chromatography achieving viral clearance in a step of purifying a therapeutic antibody using CHO cells. As a result, an antibody can be simply and effectively purified to a sufficient degree of purity for therapeutic use in humans compared to a conventional purification method, while reducing production cost.

Abstract: A method for reducing the formation of a byproduct polypeptide containing an O-acetylserine residue in place of a serine residue by adding at least one of histidine, methionine or glycine to the medium in a method for producing a polypeptide containing a serine residue by culturing transformed cells, and a method for producing a polypeptide containing a serine residue by culturing transformed cells, characterized by reducing the formation of a byproduct polypeptide containing an O-acetylserine residue in place of a serine residue by adding at least one of histidine, methionine or glycine to the medium.