Removal of endotoxin from antibody preparations for clinical use

Abstract

Despite attempts to maintain asepsis, good manufacturing practices, and the use of terminal sterilization by millipore filtration, the nuclear practitioner is always worried about the possibility of endotoxin contamination. Methods, such as ion-exchange chromatography, have been tried for removing endotoxins during the preparation of radiolabeled antibodies, and so on. As suggested by Stevenson (1990), we evaluated the Issekutz technique (1) of endotoxin removal by affinity chromatography using a polymyxin cyanogen bromide (CNBr) Sepharose column. The endotoxin content of millipore filtrates of heat killed/sonicated suspensions ofPseudomonas pyocyaneus, E. coli were measured using a Sigma (St. Louis, MO) Endotoxin Assay Kit before and after filtration through such columns and compared with the results obtained using gel exclusion and ion-exchange columns of the same length and diameter. Reduction of endotoxin content to undetectable levels by the polymyxin column was observed. The use of such columns for terminal endotoxin removal analogous to terminal sterilization is advocated especially when developing a radiopharmaceutical such as radiolabeled antibodies for in house use.