ABSTRACT
Analysis of oxidation of monoclonal antibodies (mAbs) in most cases relies on peptide mapping and LC-MS, which is time consuming and labor-intensive. A robust chromatography based method that is able to resolve and quantitate mAb oxidation variants due to oxidized methionine or tryptophan is highly desired. Here we developed a novel mixed mode chromatography method using the unique property of Sepax Zenix SEC-300MK column to analyze mAb oxidation levels. The separation of oxidized species relied upon the mixed mode of size exclusion and hydrophobic interaction between the resin and antibodies. The chromatography was performed in a regular SEC mobile phase, PBS, containing NaCl at a concentration (0-2.4M) specific for individual antibodies. This method was able to resolve and quantitate the oxidized antibodies as prepeaks, of either methionine-oxidized species induced by the common oxidants TBHP, tryptophan-oxidized species triggered by AAPH, or oxidized species by UV photo-irradiation. The prepeaks were further characterized by SEC-MALLS as monomers and confirmed by LC-MS as oxidized antibody variants with a mass increase of 16 or 32Da. This method has been successfully applied to monitor multiple monoclonal antibodies of IgG1, IgG2, and IgG4 subclasses.
Subject(s)
Antibodies, Monoclonal/metabolism , Chemistry Techniques, Analytical/methods , Chromatography, Liquid , Animals , Antibodies, Monoclonal/chemistry , CHO Cells , Cricetulus , Light , Mass Spectrometry , Methionine/chemistry , Molecular Weight , Oxidation-Reduction , Tryptophan/chemistryABSTRACT
PURPOSE: To investigate the cause of unexpected and erratic increase in aggregation during long-term storage of an IgG2 monoclonal antibody in a trehalose formulation at -20°C. METHODS: Frozen matrix was sampled, stored frozen at various temperatures and analyzed by SEC over time. RESULTS: Aggregation increased with time at -20°C but not at -40°C or -10°C. The cause of the instability was the crystallization of freeze-concentrated trehalose from the frozen solute when the storage temperature exceeds the glass transition temperature of the matrix (-29°C). Crystallization at -20°C deprives the protein of the cryoprotectant, leading to a slow increase in aggregation. Storage at -10°C also leads to crystallization of trehalose but no increase in aggregation. It is hypothesized that significantly higher mobility in the matrix at -10°C allows protein molecules that are unfolded at the ice interface on freezing to refold back before significant aggregation can occur. In contrast, lack of mobility at -40°C prevents crystallization, refolding, and aggregation. CONCLUSIONS: Aggregation in the frozen state when stored above the glass transition temperature is a consequence of balance between rate of crystallization leading to loss of cryoprotectant, rate of aggregation of the unfolded protein molecules, and rate of refolding that prevents aggregation.
Subject(s)
Antibodies, Monoclonal/chemistry , Freezing , Immunoglobulin G/chemistry , Trehalose/chemistry , Crystallization , Drug Stability , Drug Storage , Protein Folding , Protein Stability , Protein Unfolding , Thermodynamics , Time Factors , ViscosityABSTRACT
DNA-plasmid-based vaccines are a promising class of next generation therapeutics. Particle-mediated epidermal delivery is an attractive method for the administration of DNA plasmid vaccines. This technology utilizes minute quantities of DNA plasmid which have been deposited onto the surface of 2-3-microm gold particles, and so the development of this technology requires the use of analytical methods that can accurately quantitate the amount of the DNA on the particle. Spectroscopic methods are generally insufficient for this task due to interference from the gold particle. ICP-MS circumvents this issue while allowing for the sensitive, reproducible, and accurate determination of the quantity of DNA on the particle surface. This report will detail the development and application of such a method.
