Liquid-liquid phase separation causes high turbidity and pressure during low pH elution process in Protein A chromatography

Stability of Protein Pharmaceuticals: Recent Advances

There have been significant advances in the formulation and stabilization of proteins in the liquid state over the past years since our previous review. Our mechanistic understanding of protein-excipient interactions has increased, allowing one to develop formulations in a more rational fashion. The field has moved towards more complex and challenging formulations, such as high concentration formulations to allow for subcutaneous administration and co-formulation. While much of the published work has focused on mAbs, the principles appear to apply to any therapeutic protein, although mAbs clearly have some distinctive features. In this review, we first discuss chemical degradation reactions. This is followed by a section on physical instability issues. Then, more specific topics are addressed: instability induced by interactions with interfaces, predictive methods for physical stability and interplay between chemical and physical instability. The final parts are devoted to discussions how all the above impacts (co-)formulation strategies, in particular for high protein concentration solutions.'

Molecular Serum Albumin Unmask Nanobio Properties of Molecular Graphenes in Shungite Carbon Nanoparticles

Serum albumin is a popular macromolecule for studying the effect of proteins on the colloidal stability of nanoparticle (NP) dispersions, as well as the protein-nanoparticle interaction and protein corona formation. In this work, we analyze the specific conformation-dependent phase, redox, and fatty acid delivery properties of bovine albumin in the presence of shungite carbon (ShC) molecular graphenes stabilized in aqueous dispersions in the form of NPs in order to reveal the features of NP bioactivity. The formation of NP complexes with proteins (protein corona around NP) affects the transport properties of albumin for the delivery of fatty acids. Being acceptors of electrons and ligands, ShC NPs are capable of exhibiting both their own biological activity and significantly affecting conformational and phase transformations in protein systems.

The role of long noncoding RNAs in liquid-liquid phase separation

Long noncoding RNAs (lncRNAs), which are among the most well-characterized noncoding RNAs, have attracted much attention due to their regulatory functions and potential therapeutic options in many types of disease. Liquid-liquid phase separation (LLPS), the formation of droplet condensates, is involved in various cellular processes, but the molecular interactions of lncRNAs in LLPS are unclear. In this review, we describe the research development on LLPS, including descriptions of various methods established to identify LLPS, summarize the physiological and pathological functions of LLPS, identify the molecular interactions of lncRNAs in LLPS, and present the potential applications of leveraging LLPS in the clinic. The aim of this review is to update the knowledge on the association between LLPS and lncRNAs, which might provide a new direction for the treatment of LLPS-mediated disease.

Combined Liquid-State and Solid-State Nuclear Magnetic Resonance at Natural Abundance for Comparative Higher Order Structure Assessment in the Formulated-State of Biphasic Biopharmaceutics

A higher-order structure (HOS) is critical to a biopharmaceutical drug as the three-dimensional structure governs its function. Even the partial perturbation in the HOS of the drug can alter the biological efficiency and efficacy. Due to current limitations in analytical technologies, it is imperative to develop a protocol to characterize the HOS of biopharmaceuticals in the native formulated state. This becomes even more challenging for the suspension formulations where solution and solid phases co-exist. Here, we have used a combinatorial approach using liquid (1D ¹H) and solid-state (¹³C CP MAS) NMR methodology to demonstrate the HOS in the biphasic microcrystalline suspension drug in its formulated state. The data were further assessed by principal component analysis and Mahalanobis distance (D_M) calculation for quantitative assessment. This approach is sufficient to provide information regarding the protein HOS and the local dynamics of the molecule when combined with orthogonal techniques such as X-ray scattering. Our method can be an elegant tool to investigate batch-to-batch variation in the process of manufacture and storage as well as a biosimilarity comparison study for biphasic/microcrystalline suspension.

Phase separation of a plant virus movement protein and cellular factors support virus-host interactions

Both cellular and viral proteins can undergo phase separation and form membraneless compartments that concentrate biomolecules. The p26 movement protein from single-stranded, positive-sense Pea enation mosaic virus 2 (PEMV2) separates into a dense phase in nucleoli where p26 and related orthologues must interact with fibrillarin (Fib2) as a pre-requisite for systemic virus movement. Using in vitro assays, viral ribonucleoprotein complexes containing p26, Fib2, and PEMV2 genomic RNAs formed droplets that may provide the basis for self-assembly in planta. Mutating basic p26 residues (R/K-G) blocked droplet formation and partitioning into Fib2 droplets or the nucleolus and prevented systemic movement of a Tobacco mosaic virus (TMV) vector in Nicotiana benthamiana. Mutating acidic residues (D/E-G) reduced droplet formation in vitro, increased nucleolar retention 6.5-fold, and prevented systemic movement of TMV, thus demonstrating that p26 requires electrostatic interactions for droplet formation and charged residues are critical for nucleolar trafficking and virus movement. p26 readily partitioned into stress granules (SGs), which are membraneless compartments that assemble by clustering of the RNA binding protein G3BP following stress. G3BP is upregulated during PEMV2 infection and over-expression of G3BP restricted PEMV2 RNA accumulation >20-fold. Deletion of the NTF2 domain that is required for G3BP condensation restored PEMV2 RNA accumulation >4-fold, demonstrating that phase separation enhances G3BP antiviral activity. These results indicate that p26 partitions into membraneless compartments with either proviral (Fib2) or antiviral (G3BP) factors.

Comprehensive Assessment of Protein and Excipient Stability in Biopharmaceutical Formulations Using 1H NMR Spectroscopy

Biopharmaceutical proteins are important drug therapies in the treatment of a range of diseases. Proteins, such as antibodies (Abs) and peptides, are prone to chemical and physical degradation, particularly at the high concentrations currently sought for subcutaneous injections, and so formulation conditions, including buffers and excipients, must be optimized to minimize such instabilities. Therefore, both the protein and small molecule content of biopharmaceutical formulations and their stability are critical to a treatment's success. However, assessing all aspects of protein and small molecule stability currently requires a large number of analytical techniques, most of which involve sample dilution or other manipulations which may themselves distort sample behavior. Here, we demonstrate the application of 1H nuclear magnetic resonance (NMR) spectroscopy to study both protein and small molecule content and stability in situ in high-concentration (100 mg/mL) Ab formulations. We show that protein degradation (aggregation or fragmentation) can be detected as changes in 1D 1H NMR signal intensity, while apparent relaxation rates are specifically sensitive to Ab fragmentation. Simultaneously, relaxation-filtered spectra reveal the presence and degradation of small molecule components such as excipients, as well as changes in general solution properties, such as pH. 1H NMR spectroscopy can thus provide a holistic overview of biopharmaceutical formulation content and stability, providing a preliminary characterization of degradation and acting as a triaging step to guide further analytical techniques.

Process optimization and protein engineering mitigated manufacturing challenges of a monoclonal antibody with liquid-liquid phase separation issue by disrupting inter-molecule electrostatic interactions

We report a case study in which liquid-liquid phase separation (LLPS) negatively impacted the downstream manufacturability of a therapeutic mAb. Process parameter optimization partially mitigated the LLPS, but limitations remained for large-scale manufacturing. Electrostatic interaction driven self-associations and the resulting formation of high-order complexes are established critical properties that led to LLPS. Through chain swapping substitutions with a well-behaved antibody and subsequent study of their solution behaviors, we found the self-association interactions between the light chains (L_Cs) of this mAb are responsible for the LLPS behavior. With the aid of in silico homology modeling and charged-patch analysis, seven charged residues in the L_C complementarity-determining regions (CDRs) were selected for mutagenesis, then evaluated for self-association and LLPS properties. Two charged residues in the light chain (K30 and D50) were identified as the most significant to the LLPS behaviors and to the antigen-binding affinity. Four adjacent charged residues in the light chain (E49, K52, R53, and R92) also contributed to self-association, and thus to LLPS. Molecular engineering substitution of these charged residues with a neutral or oppositely-charged residue disrupted the electrostatic interactions. A double-mutation in CDR2 and CDR3 resulted in a variant that retained antigen-binding affinity and eliminated LLPS. This study demonstrates the critical nature of surface charged resides on LLPS, and highlights the applied power of in silico protein design when applied to improving physiochemical characteristics of therapeutic antibodies. Our study indicates that in silico design and effective protein engineering may be useful in the development of mAbs that encounter similar LLPS issues.

High-Throughput Analytical Light Scattering for Protein Quality Control and Characterization

We present a review of high-throughput techniques for the characterization and quality control of proteins in the course of purification, evaluation, and formulation, based on static and dynamic light scattering. Multi-angle static light scattering (MALS) in combination with rapid, low-volume UHPLC size exclusion chromatography is effective in characterizing key biophysical properties, while dynamic light scattering (DLS) in high-throughput microwell-plate format provides large quantities of data in a short time to screen many conditions, excipients, cell lines, or candidate biotherapeutics.

Effective filter screening approach with fractionation for enabling inline filtration of protein A eluate

Filtration of protein A eluates inline with a chromatography column is a common challenge for monoclonal antibody (mAb) purification due to the high system backpressure during elution, which can result in system shut down or require a decreased elution flow rate. The inability to filter inline not only poses a risk for process deviations, but can also lead to tank constraints and microbial ingress risk. Here, we evaluated and described a novel approach for identifying filters for inline filtration of protein A eluates at pilot scale. We fractionated the protein A eluates into 0.25 column volume fractions to screen filters under constant pressure or constant flow conditions. We observed that filtration properties for eluate fractions are significantly different from the offline eluate, and the conventional filter sizing study using elution pool is not able to predict inline filtration behavior. Through the submicron particle counts and size distribution in pre- and post-filtration samples, we determined that both attributes contribute to the high pressure across the filters. A successful proof-of-concept experiment on a column 10 cm in diameter inline with the filter train selected validated this fractionation method, and the approach was applied to a different mAb molecule to confirm effectiveness.

Determination of Interaction Parameters for Reversibly Self-Associating Antibodies: A Comparative Analysis

Monoclonal antibodies (mAbs) represent a major class of biotherapeutics and are the fastest growing category of biologic drugs on the market. However, mAb development and formulation are often impeded by reversible self-association (RSA), defined as the dynamic exchange of monomers with native-state oligomers. Here, we present a comparative analysis of the self-association properties for 5 IgG mAbs, under matched conditions and using orthogonal methods. Concentration-dependent dynamic light scattering and sedimentation velocity studies revealed that the majority of mAbs examined exhibited weak to moderate RSA. However, because these studies were carried out at mAb concentrations in the mg/mL range, we also observed significant nonideality. Noting that nonideality frequently masks RSA and vice versa, we conducted direct boundary fitting of the sedimentation velocity data to determine stoichiometric binding models, interaction affinities, and nonideality terms for each mAb. These analyses revealed equilibrium constants from micromolar to millimolar and stoichiometric models from monomer-dimer to isodesmic. Moreover, even for those mAbs described by identical models, we observed distinct kinetics of self-association. The accuracy of the models and their corresponding equilibrium constants were addressed using sedimentation equilibrium and simulations. Overall, these results serve as the starting point for the comparative dissection of RSA mechanisms in therapeutic mAbs.