Evaluation of product equivalence during process optimization for manufacture of a human IgM monoclonal antibody.

We have developed a battery of tests to characterize monoclonal antibodies and assess the effect of potential manufacturing process changes. Tryptic peptide mapping, molecular weight determination by HPLC and classical light scattering, isoelectric focussing, oligosaccharide mapping by HPAE-PAD chromatography, circular dichroism spectra and differential scanning calorimetry were applied as sensitive assays of antibody structure. Biological activity was assessed by measurement of specific antigen binding activity, binding spectrum and opsonic activity. Pharmacokinetics was assessed by clearance rate studies in rats. The sensitivity of this battery of assays was demonstrated by the ability to readily detect differences between a human monoclonal antibody (IgM-2) produced by in vitro cell culture versus ascites culture. These same tests support equivalence of a second monoclonal antibody (IgM-1) produced before and after in vitro cell culture process improvements which resulted in a twofold increase in product titer.