Mechanism of low molecular weight impurity formation in an IgG1 monoclonal antibody formulation.

Formulation robustness study was performed for a biosimilar monoclonal antibody (IgG1) manufactured at Dr. Reddy's Laboratory, where the pH and concentration level of excipients in the drug product formulation were systematically varied from the target formulation. It was observed that the IgG1 formulation having relatively low pH and high citrate (buffer salt) concentration were predisposed to the formation of low molecular weight impurities. Mass spectrometry analysis of the mAb1 fragments detected the pyroglutamate species from LC-LC dimer and fragmentation in the -DKTH- amino acid sequence of the heavy chain. Blind docking indicated binding of citrate with Lysine 222 residue in the proximity of Cys224 could have potentially fragmented IgG1.