A Series of Collaborations between Various Pharmaceutical Companies and Regulatory Authorities Concerning the Analysis of Biomolecules Using Capillary Electrophoresis: Additional Instruments/Buffer

Native fluorescence detection with a laser driven light source for protein analysis in capillary electrophoresis

While ultraviolet light (UV) absorbance detection is the most widely used detection mode in capillary electrophoresis (CE), it can yield poor concentration sensitivity and has tendencies to exhibit baseline fluctuations. In order to overcome these challenges, alternative detection strategies, including the use of dedicated wavelength lasers, have been applied, resulting in enhancements of concentration sensitivity as well as decreased baseline disturbance. In this work, using a laser driven light source for excitation, we reported a native fluorescence detection (NFD) scheme for use in a commercial CE platform, PA 800 Plus Pharmaceutical Analysis System, for protein analysis. The CE-NFD system was characterized using tryptophan and a reduced IgG. We compared NFD with UV absorbance detection as applied to sodium dodecyl sulfate-capillary gel electrophoresis (SDS-CGE) and capillary isoelectric focusing (cIEF). In SDS-CGE, with the reported NFD a non-reduced IgG standard sample yielded a signal-to-noise ratio which was 14.6 times higher than with UV absorbance detection at 214 nm. In cIEF analysis of NISTmAb, Humanized IgG1_k, with NFD ∼170 times less sample mass was needed to obtain similar profile quality to that with UV absorbance detection at 280 nm. NFD also eliminated baseline anomalies observed with UV absorbance detection and showed less interference by other absorbing species. These results suggest that CE-NFD is a practical and powerful tool for protein characterization in the biopharmaceutical industry.

Interlaboratory method validation of capillary electrophoresis sodium dodecyl sulfate (CE-SDS) methodology for analysis of mAbs

Capillary electrophoresis sodium dodecyl sulfate (CE-SDS) is an analytical method to assess the purity of proteins, commonly applied to monoclonal antibodies (mAbs) in the biopharmaceutical industry. To address the need to standardize the CE-SDS method in the pharmaceutical industry and to enhance the confidence in method transfer between laboratories operating different commercial capillary electrophoresis (CE) instrument platforms, an interlaboratory CE-SDS method validation was organized involving 13 laboratories in 13 companies on four different types of commercial capillary electrophoresis instruments. In the validation, a commercial mAb therapeutic was used as the sample. The validation process followed the analytical guidelines set by the ICH guidelines (International Conference for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use). The method's precision, accuracy, linearity and range, and limit of quantitation (LOQ) were validated in the study. Variations of all the parameters validated in the study passed the pre-set criteria defined at the beginning of the study. The definition was based on previously published works and the intended application purpose of the CE-SDS method for mAbs. The study proved that the CE-SDS method fits its intended application purpose as a size impurity assay and size heterogeneity characterization assay for mAb therapeutic products. This study is the first time a CE-SDS method is validated by multiple laboratories using different commercial CE instrument platforms and on a commercial mAb therapeutic. Its results will enhance the confidence of the biopharmaceutical industry to develop CE-SDS methods and transfer CE-SDS methods between different laboratories.

Integration of liquid chromatography mass spectrometry with a heavy peptide response curve accurately measures unprocessed C-terminal lysine during peptide mapping analysis of therapeutic antibodies in a single run

Therapeutic monoclonal and bispecific antibodies are susceptible to modification after protein biosynthesis. These post-translational modifications (PTMs) not only contribute to mass and charge heterogeneity, but they can also negatively impact the molecule's activity, half-life, and immunogenicity. Therefore, identification and quantification of PTMs are critical to ensure the safety and efficacy of an antibody therapeutic as well as demonstrate product consistency and process control. Unprocessed C-terminal lysine on the heavy chain (HC) is a prevalent modification that contributes to this charge heterogeneity in antibodies. Peptide mapping through liquid chromatography tandem mass spectrometry (LC-MS²) enjoys higher selectivity and sensitivity for measuring this PTM relative to global PTM methods, but differences in the ionization efficiencies of the unprocessed C-terminal K peptide and the truncated C-terminal K peptide result in its overestimation. Consequently, large discrepancies in this PTM's measured abundance may exist between different characterization assays used in regulatory filings, which can be further compounded by large variability when multiple mass spectrometers are used to quantify C-terminal K during a therapeutic's lifespan. In this study, we propose a simple new method to quantify unprocessed C-terminal K in antibodies in a single LC-MS² run that incorporates heavy isotopic standards for both the unprocessed and truncated C-terminal K peptide to build a response curve and correct for the disparity in ionization efficiency between these two different peptide sequences. The approach was evaluated across two different Orbitrap-based mass spectrometers using multiple monoclonal and bispecific therapeutic antibodies, resulting in accurate (<10% error, as determined with peptide standards) and precise C-terminal K quantification during peptide mapping analysis.

Capillary Electrophoresis Method for the Assessment of Erythropoiesis-Stimulating Agents in Final Formulations

Capillary electrophoresis (CE) comprises several separation modes that can be used to characterize proteins in terms of physico-chemical properties such as isoelectric point or molecular weight, or in terms of purity/heterogeneity for the presence of charge or size variants. In glycoproteins the heterogeneity occurring as a consequence of variable amounts of terminal sialic acid residues on glycan moieties can be detected by CE. As such, a capillary zone electrophoresis (CZE) method was found suitable for the detection of isoforms of several erythropoiesis-stimulating agents (Bietlot and Girard, J Chromatogr A 759:177-184, 1997; Boucher et al., J Pharm Biomed Anal 71:207-213, 2012). In particular, the method can be used to analyze finished products containing erythropoietin-α, erythropoietin-β, or darbepoetin-α regardless of the formulation and without the need for sample pretreatment. The major excipients encountered in the various formulations included polysorbate 80, polysorbate 20, or human serum albumin. The ability of the method to resolve isoforms of the active ingredient in finished product enables the comparison of the isoform profile with that of the corresponding drug substance, allowing the assessment of the structural integrity and content of the active ingredients in finished products.

Recent advances in capillary electrophoretic migration techniques for pharmaceutical analysis

Since the introduction about 30 years ago, CE techniques have gained a significant impact in pharmaceutical analysis. The present review covers recent advances and applications of CE for the analysis of pharmaceuticals. Both small molecules and biomolecules such as proteins are considered. The applications range from the determination of drug-related substances to the analysis of counterions and the determination of physicochemical parameters. Furthermore, general considerations of CE methods in pharmaceutical analysis are described.