Rapid method for monitoring galactosylation levels during recombinant antibody production by electrospray mass spectrometry with selective-ion monitoring

This report describes a simple and rapid method to determine the relative a mounts of glycoforms differing in terminal galactose on a recombinant antib ody produced in Chinese hamster ovary (CHO) cells. The method uses a single quadrupole mass spectrometer coupled to an HPLC system to quantify the gly coform amounts found on a recombinant antibody that binds to the human CD20 antigen. Samples from the recombinant antibody process are reduced and inj ected directly into the HPLC system where the heavy and light chain antibod y fragments, as well as host-cell protein contaminants, are separated chrom atographically. Mass-selective detection is performed in the selected-ion m onitoring (SIM) mode to monitor the most abundant (38(+)) ions correspondin g to the glycoforms found on the heavy chain of the recombinant antibody. R esults obtained using the assay demonstrate good sensitivity, linearity and reproducibility, Comparison to a method using capillary electrophoresis (C B) of the labeled free oligosaccharides demonstrates similar quantitation o f the glycoforms in the recombinant antibody. The LC-MS method provides a s imple and rapid means for accurately quantifying antibody glycoforms direct ly from cell culture and other process samples. (C) 2001 Elsevier Science B .V. All rights reserved.