Endotoxin reduction in monoclonal antibody preparations using arginine

A monoclonal antibody preparation was found to be contaminated with endotoxin. Several commercial endotoxin removal steps were attempted but failed to produce a significant reduction due to the fact that the endotoxin was associated with the antibody. Here, several methods for endotoxin removal based on immobilizing monoclonal antibodies to chromatographic media have been evaluated. A crucial step in this process was to dissociate the endotoxin from the protein surface for subsequent removal. This was accomplished by introducing different buffer additives in the mobile phase. In agreement with previous reports, non-ionic detergents efficiently removed endotoxin, but it was also found that 0.5M arginine performed equally well. Since arginine is a non-toxic common amino acid that can be readily removed, it was selected and successfully used in large-scale experiments. With this method, endotoxin could be reduced to <0.2 EU mg(-1) with recovery of the target protein being >95%. Since this procedure is easily integrated into the existing processes of mAb purification, it offers advantages in speed, cost and effort.