Characterization of the photodegradation of a human IgG1 monoclonal antibody formulated as a high-concentration liquid dosage form

The photodegradation of a human IgG1 monoclonal antibody has been examined in a high concentration (100 mg/mL) liquid formulation. It was observed that a yellowish color is generated when the formulation is exposed to intense and prolonged light exposure, and this discoloration occurs along with a loss in bioactivity. Extensive analytical characterization was performed to determine light induced degradation pathways that occur during exposure to intense light of ICH photodegradation conditions. It has been shown that the monoclonal antibody undergoes a combination of physical and chemical reactions under these conditions, including covalent aggregate formation, fragmentation at the hinge region, oxidation of Trp, His, and Met residues, and deamidation of Asn residues. Oxidation of Trp 94 and deamidation of Asn 93, located in the light chain CDR region, correlates with loss of bioactivity under these conditions. A series of formulation experiments were performed to elucidate the impact of the extent of light exposure, oxygen, protein concentration, and solution pH on the photostability of the formulation. Results demonstrated that photodegradation of the IgG, after intensive light exposure, can be prevented by proper secondary packaging. In addition, it is also shown that a high concentration, liquid dosage form of a human monoclonal antibody is stable upon exposure to the ambient light conditions encountered during routine manufacturing, long-term storage, and administration with proper design of formulation conditions, the primary container as well as the secondary package. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:3117–3130, 2009