Characterization of Monoclonal Antibody Aggregates and Emerging Technologies

Using Digestion by IdeS Protease to Improve Quantification of Degradants in Monoclonal Antibodies by Non-Reducing Capillary Gel Electrophoresis

Monoclonal antibodies (mAbs) have become predominant therapeutics by providing highly specific mechanisms of action enabling treatment of complex diseases. However, mAbs themselves are highly complex and require thorough testing and characterization to ensure efficacy and patient safety. In this regard, fragmentation is a degradation product of concern. The biotechnology industry uses capillary gel electrophoresis (CGE) to quantify fragmentation by electrophoretically resolving size variants, such as products resulting from partial reduction of interchain disulfides. However, standard CGE methods may not adequately separate less typical fragments, particularly when there is minimal size difference to the parent molecule. For mAb-1, a degradant only ∼11 kDa smaller than the intact mAb (∼149 kDa) was unable to be resolved under typical non-reducing conditions, preventing an accurate purity assessment and precluding tracking of product purity within stability studies. To address these deficiencies, a subunit-based non-reducing CGE method was developed to employ IdeS protease to produce F(ab')2 and Fc fragments, which resulted in baseline resolution of the clipped subunit species from its parent species. This enabled more accurate trending of purity throughout stability studies. Method characterization ensured that this subunit method monitored expected impurities observed by intact non-reducing CGE and thus could suitably replace non-reducing CGE in the release and stability testing panel. It also has the potential to replace reducing CGE based on its tracking of the deglycosylated Fc species. We believe this approach of utilizing proteases to develop subunit CGE methods for release and stability can be applied to other molecules when in need of resolving analogous fragments.

Ion Mobility-Mass Spectrometry Reveals the Structures and Stabilities of Biotherapeutic Antibody Aggregates

Stability is a key critical quality attribute monitored throughout the development of monoclonal antibody (mAb) therapeutics. Minor changes in their higher order structure (HOS) caused by stress or environment may alter mAb aggregation, immunogenicity, and efficacy. In addition, the structures of the resulting mAb aggregates are largely unknown, as are their dependencies on conditions under which they are created. In this report, we investigate the HOS of mAb monomers and dimers under a variety of forced degradation conditions with ion mobility-mass spectrometry (IM-MS) and collision-induced unfolding (CIU) technologies. We evaluate two model IgG1 antibodies that differ significantly only in their complementarity-determinant regions: IgG1α and IgG1β. Our data covering both heat- and pH-based forced degradation conditions, aquired on two different IM-MS platforms, show that these mAbs undergo global HOS changes at both monomer and dimer levels upon degradation, but shifts in collision cross section (CCS) differ under pH or heat degradation conditions. In addition, the level of CCS change detected is different between IgG1α and IgG1β, suggesting that differences in the CDR drive differential responses to degradation that influence the antibody HOS. Dramatically different CIU fingerprints are obtained for IgG1α and IgG1β monomers and dimers for both degradation conditions. Finally, we constructed a series of computational models of mAb dimers for comparison with experimental CCS values and found evidence for a compact, overlapped dimer structure under native and heat degradation conditions, possibly adopting an inverted or nonoverlapped quaternary structure when produced through pH degredation. We conclude by discussing the potential impact of our findings on ongoing biotherapeutic discovery and development efforts.

In Silico Analysis of Therapeutic Antibody Aggregation and the Influence of Glycosylation

The aggregation of therapeutic antibodies is a major issue for the pharmaceutical industry leading to loss of drug quality, increased dosage, and unwanted immune responses such as the production of anti-drug antibodies (ADA). As aggregation can occur at various stages of development and storage, much work has been performed to reduce or eliminate it. In this report we analyzed four antibodies available in the PDB (1IGT, 1IGY, 1HZH, and 5DK3) using the online software UCSF Chimera to study the structural features of the proteins and the associated N-linked glycans in the CH2 domains of the Fc region. To study antibody aggregation in silico we used the online software TANGO and AGGRESCAN to identify aggregation prone regions (APR) in the antibodies and the influence of the Fc glycans on hydrophobic and aromatic residues present in the APRs. In the 3D structures of 1IGT and 1IGY the glycan chains are in close enough proximity to influence and protect these hydrophobic regions. However, in the 3D structures of 1HZH and 5DK3 the glycans do not appear to influence the likely APRs of the antibodies. Therefore, in these structures we modified the Fc glycan regions by adjusting the glycosylated asparagine side chains and glycosidic bonds. We successfully adjusted the glycan chains of 1HZH and 5DK3 and reduced the distance between them and the APRs to show potential influence on aggregation. However, similar to 5DK3, the influence of glycosylation on the APRs of the antibody was limited due to the size of the glycans present in the 3D structure. This report is based on in silico studies to show how antibody glycans can influence aggregation.

Development of orthogonal NISTmAb size heterogeneity control methods

The NISTmAb is a monoclonal antibody Reference Material from the National Institute of Standards and Technology; it is a class-representative IgG1κ intended to serve as a pre-competitive platform for harmonization and technology development in the biopharmaceutical industry. The publication series of which this paper is a part describes NIST's overall control strategy to ensure NISTmAb quality and availability over its lifecycle. In this paper, the development of a control strategy for monitoring NISTmAb size heterogeneity is described. Optimization and qualification of size heterogeneity measurement spanning a broad size range are described, including capillary electrophoresis-sodium dodecyl sulfate (CE-SDS), size exclusion chromatography (SEC), dynamic light scattering (DLS), and flow imaging analysis. This paper is intended to provide relevant details of NIST's size heterogeneity control strategy to facilitate implementation of the NISTmAb as a test molecule in the end user's laboratory. Graphical abstract Representative size exclusion chromatogram of the NIST monoclonal antibody (NISTmAb). The NISTmAb is a publicly available research tool intended to facilitate advancement of biopharmaceutical analytics. HMW = high molecular weight (trimer and dimer), LMW = low molecular weight (2 fragment peaks). Peak labeled buffer is void volume of the column from L-histidine background buffer.

The NISTmAb Reference Material 8671 lifecycle management and quality plan

Comprehensive analysis of monoclonal antibody therapeutics involves an ever expanding cadre of technologies. Lifecycle-appropriate application of current and emerging techniques requires rigorous testing followed by discussion between industry and regulators in a pre-competitive space, an effort that may be facilitated by a widely available test metric. Biopharmaceutical quality materials, however, are often difficult to access and/or are protected by intellectual property rights. The NISTmAb, humanized IgG1κ Reference Material 8671 (RM 8671), has been established with the intent of filling that void. The NISTmAb embodies the quality and characteristics of a typical biopharmaceutical product, is widely available to the biopharmaceutical community, and is an open innovation tool for development and dissemination of results. The NISTmAb lifecyle management plan described herein provides a hierarchical strategy for maintenance of quality over time through rigorous method qualification detailed in additional submissions in the current publication series. The NISTmAb RM 8671 is a representative monoclonal antibody material and provides a means to continually evaluate current best practices, promote innovative approaches, and inform regulatory paradigms as technology advances. Graphical abstract The NISTmAb Reference Material (RM) 8671 is intended to be an industry standard monoclonal antibody for pre-competitive harmonization of best practices and designing next generation characterization technologies for identity, quality, and stability testing.