The influence of methods of production, purification and storage of monoclonal antibodies upon their observed specificities

Recent advancements, challenges, and practical considerations in the mass spectrometry-based analytics of protein biotherapeutics: A viewpoint from the biosimilar industry

The extensive analytical characterization of protein biotherapeutics, especially of biosimilars, is a critical part of the product development and registration. High-resolution mass spectrometry became the primary analytical tool used for the structural characterization of biotherapeutics. Its high instrumental sensitivity and methodological versatility made it possible to use this technique to characterize both the primary and higher-order structure of these proteins. However, even by using high-end instrumentation, analysts face several challenges with regard to how to cope with industrial and regulatory requirements, that is, how to obtain accurate and reliable analytical data in a time- and cost-efficient way. New sample preparation approaches, measurement techniques and data evaluation strategies are available to meet those requirements. The practical considerations of these methods are discussed in the present review article focusing on hot topics, such as reliable and efficient sequencing strategies, minimization of artefact formation during sample preparation, quantitative peptide mapping, the potential of multi-attribute methodology, the increasing role of mass spectrometry in higher-order structure characterization and the challenges of MS-based identification of host cell proteins. On the basis of the opportunities in new instrumental techniques, methodological advancements and software-driven data evaluation approaches, for the future one can envision an even wider application area for mass spectrometry in the biopharmaceutical industry.

Affinity-based precipitation via a bivalent peptidic hapten for the purification of monoclonal antibodies

In a previous study, we demonstrated a non-chromatographic affinity-based precipitation method, using trivalent haptens, for the purification of mAbs. In this study, we significantly improved this process by using a simplified bivalent peptidic hapten (BPH) design, which enables facile and rapid purification of mAbs while overcoming the limitations of the previous trivalent design. The improved affinity-based precipitation method (ABP(BPH)) combines the simplicity of salt-induced precipitation with the selectivity of affinity chromatography for the purification of mAbs. The ABP(BPH) method involves 3 steps: (i) precipitation and separation of protein contaminants larger than immunoglobulins with ammonium sulfate; (ii) selective precipitation of the target-antibody via BPH by inducing antibody-complex formation; (iii) solubilization of the antibody pellet and removal of BPH with membrane filtration resulting in the pure antibody. The ABP(BPH) method was evaluated by purifying the pharmaceutical antibody trastuzumab from common contaminants including CHO cell conditioned media, DNA, ascites fluid, other antibodies, and denatured antibody with >85% yield and >97% purity. Importantly, the purified antibody demonstrated native binding activity to cell lines expressing the target protein, HER2. Combined, the ABP(BPH) method is a rapid and scalable process for the purification of antibodies with the potential to improve product quality while decreasing purification costs.

The production of more useful monoclonal antibodies 2. The use of somatic-cell genetic and recombinant-DNA technology to tailor-make monoclonal antibodies

In last month's issue(1) Matthew Scharff and his colleagues discussed recent improvements in the technique of making monoclonal antibodies by cell fusion. However, not all the monoclonal antibodies generated by hybridoma technology have all of the properties required for a particular task. This second part of a two-part review deals with ways in which these first-generation reagents can be improved by identifying somatic-cell mutants with the desired properties or by engineering new and even novel molecules using recombinant DNA technology.

Small-molecule-based affinity chromatography method for antibody purification via nucleotide binding site targeting

The conserved nucleotide binding site (NBS), found within the Fab variable domain of antibodies, remains a not-so-widely known and underutilized site. Here we describe a novel affinity chromatography method that utilizes the NBS as a target for selectively purifying antibodies from complex mixtures. The affinity column was prepared by coupling indole butyric acid (IBA), which has a monovalent affinity for the NBS with a K(d) ranging between 1 and 8 μM, to ToyoPearl resin resulting in the NBS targeting affinity column (NBS(IBA)). The proof-of-concept studies performed using the chimeric pharmaceutical antibody rituximab demonstrated that antibodies were selectively captured and retained on the NBS(IBA) column and were successfully eluted by applying a mild NaCl gradient at pH 7.0. Furthermore, the NBS(IBA) column consistently yielded >95% antibody recovery with >98% purity, even when the antibody was purified from complex mixtures such as conditioned cell culture supernatant, hybridoma media, and mouse ascites fluid. The results presented in this study establish the NBS(IBA) column as a viable small-molecule-based affinity chromatography method for antibody purification with significant implications in industrial antibody production. Potential advantages of the NBS(IBA) platform are improved antibody batch quality, enhanced column durability, and reduced overall production cost.

Stabilization and surface modification of monoclonal antibodies by 'bi-layer encagement'

A two step simple procedure for antibody stabilization in soluble form was developed. The antibody is first treated with low molecular weight polyaldehyde (polyglutaraldehyde). Following removal of non-bound polyaldehyde the antibody-polyaldehyde conjugate is crosslinked by polyamine (alkyl amine derivative of polyglutaraldehyde). Feasibility studies were successfully conducted employing monoclonal antibody raised against horseradish peroxidase as model system. The stabilized antibody preparation exhibited improved thermal stability, enhanced resistance to proteolytic digestion and higher 'specific binding activity' in ELISA test, without losing its capability to bind large antigen (enzyme) or being recognized by another antibody (goat anti-mouse IgG).

Analytical quality control in neonatal screening

This critical review questions the present understanding in monitoring of analytical quality control in neonatal screening. Current status and historical background of the analytical quality control, particularly of the tests intended for the screening of congenital hypothyroidism and some inborn errors of metabolism, is reviewed. The reasons why attempts to standardize immunoassays through the preparation of a so-called "gold standard" (e.g. for thyrotropin) will not resolve noncomparability of results are discussed. The review presents arguments for the necessity of elaboration of international guidelines for methods assessment and comparison with an emphasis on their clinical relevance.

The influence of sucrose, dextran, and hydroxypropyl-beta-cyclodextrin as lyoprotectants for a freeze-dried mouse IgG2a monoclonal antibody (MN12)

The influence of lyophilization on the stability of a monoclonal antibody (MN12) was investigated. MN12 was freeze-dried in different formulations [without lyoprotectant or in the presence of sucrose, dextran, or hydroxypropyl-beta-cyclodextrin (HP beta CD)] and under varying conditions (with or without secondary drying). Subsequently, the monoclonal antibody was stored for 18 or 32 days at various temperatures (4, 37, or 56 degrees C). For comparison, solutions of MN12 were stored under the same conditions. Regardless of the lyoprotectant used, precipitation and a concomitant reduction of the antigen-binding capacity by about 10% were observed upon reconstitution of lyophilized MN12. HP beta CD proved to be the most effective stabilizer to prevent degradation of lyophilized MN12 during storage. Compared with MN12 solutions, HP beta CD-containing lyophilized MN12 cakes were more resistant to heat-induced charge alterations and loss of antigen-binding capacity.

Analytical approaches to the study of monoclonal antibody stability

The stability of two purified monoclonal antibodies, MN12 and WT31, was investigated. The monoclonal antibodies were incubated for 32 days at different pH values (ranging from 3.0 to 10.0) at 4 and 37 degrees C. Various analytical methods were used to assess changes in physicochemical properties of the proteins. The monoclonal antibodies were more susceptible to degradation at 37 degrees C than at 4 degrees C. At low pH irreversible precipitation occurred. Decomposition of the proteins was enhanced at increasing pH values in the alkaline range. This was concluded from mouse IgG-specific and antigen-specific enzyme-linked immunosorbent assays, flow cytometry, analytical gel permeation chromatography, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, isoelectric focusing, and immunoblotting. No substantial change in the apparent affinity constant of MN12 was observed, as determined by an affinity enzyme-linked immunosorbent assay. Fluorescence spectra, fluorescence polarization values, and fluorescence quenching parameters of MN12 and WT31 were not substantially affected, indicating that no major irreversible conformational changes had occurred. It was concluded that each of the techniques used has only limited value for stability assessment of monoclonal antibodies and, hence, that the application of several analytical techniques is essential to gain insight into monoclonal antibody stability.

Immunologic and pharmacologic concepts of monoclonal antibodies

While monoclonal antibodies have solved many of the difficulties of using immunologic reagents for radioimmunodiagnosis and therapy, in the 13 years since their introduction a number of persistent problems remain, most notably a low yield of antibody-producing cells from the fusion process, difficulty in obtaining high-affinity antibodies, and the potential immunogenicity of murine immunoglobulins (Igs). Several solutions are under development, including fusion techniques that enrich for cells producing desired antibodies, production of human-mouse chimeric antibodies by recombinant DNA technology, and the generation of human monoclonal antibodies by promising new approaches. Until these upcoming methodologies are established, and to better direct their development and application, a sound understanding of the pharmacology of presently available native and modified monoclonal antibodies is crucial. Although much has been already determined in this area, a great deal of further clarification remains necessary.

Protein purification

This monograph summarizes recent developments in the purification and analysis of natural and recombinant proteins. The basic strategies employed in protein purification are reviewed with regards to the characteristics of the protein of interest that may aid its isolation, choice of the starting material, and use of denaturants. Preparation of cell-free extracts followed by bulk precipitation and/or phase partition constitute the initial steps of many purification schemes. Chromatographic methods (size exclusion, ion exchange, hydroxylapatite, reversed phase, hydrophobic interaction and affinity based) utilizing either traditional, low pressure or high-performance liquid chromatography instrumentation are discussed. Electrophoretic techniques used to analyze the homogeneity of the protein product include SDS-PAGE, isotachophoresis, IEF and two dimensional gel electrophoresis.

Hazards of the limiting-dilution method of cloning hybridomas

Three hybridoma clones, which were shown to change the characteristics of their antibody specificities when grown under different culturing conditions, are described in detail. This phenomenon was shown to be due to the persistence of mixed clones, even under conditions where standard statistical treatment indicated a high probability of monoclonality. Such mixed clones persisted, sometimes undetected, through repeated cycles of re-cloning. It was shown that the assumption that every viable clone has the same random chance of monoclonality, is invalid, and can lead to misleadingly high estimates for the probability of monoclonality. Verification of seeding of individual wells with single cells is recommended and the relative merits of this versus repeated limiting-dilution cloning are discussed.

Evaluation of a method of production and purification of monoclonal antibodies for clinical applications

A procedure is described for the purification of monoclonal antibodies (Mab) from ascitic fluids, which meets the quality control required for in vivo applications of immunoglobulins (Ig) in man. Additional assays were performed to calculate viral and DNA content of the purified Mab. These studies are important to prevent the possible side effects, oncogenic events and virus-related diseases which could follow immunotherapy with Mab.

Determination of antigen-specific immunoglobulin content in ascitic fluids and antisera

A rapid and sensitive method is described for the determination of the antigen-specific immunoglobulin contents of ascitic fluids and/or antisera. Immunoglobulins are quantitatively separated from the biological fluid by immunoaffinity chromatography on the insolubilized antigen using the Millipore Millititer filtration system to perform the simultaneous assay of multiple samples. The specific immunoglobulins are then eluted at acidic pH and their concentration is estimated by solid-phase competitive radioimmunoassay. Radioimmunoassay values, corrected for dilutions, give the antigen-specific immunoglobulin concentration of ascitic fluids and/or antisera.