Real-Time Assessment of the Size Changes of Individual Sub-Visible Protein Particles under Buffer Variations: A Microfluidic Study.

Protein particles in biological drugs can significantly impact drug efficacy and carry the risk of adverse effects. Despite advancements, the understanding and control of particle formation in biopharmaceutical manufacturing remain incomplete. Therefore, further investigation into protein particles is warranted, especially considering that novel formats of biological drugs may be more susceptible to aggregation and particle formation than conventional monoclonal antibodies. In this study, we introduce a microfluidic approach for the real-time analysis of individual sub-visible protein particles during buffer exchange. We find that the modulation of intermolecular forces, achieved by changing the buffer pH or urea concentration, leads to the reversible swelling and shrinkage of particles by up to 50%, which is a consequence of altered intermolecular distances. Additionally, we identify a discrepancy in the biophysical behavior of protein particles compared to monomeric protein. This finding highlights the limited predictive power of commonly applied biophysical characterization methods for particle formation in early formulation development. Moreover, the observed particle swelling may be associated with manufacturing deviations, such as filter clogging. These results highlight the importance of studying individual particles to gain a comprehensive insight into particle behavior and the impact of formulation variations in the biopharmaceutical industry.

Real-time imaging of monoclonal antibody film reconstitution after mechanical stress at the air-liquid interface by Brewster angle microscopy.

Monoclonal antibodies (mAbs) represent an important part of biological pharmaceutics. A serious challenge in their development is the formation of protein particles, which are often formed through protein aggregation at the air-liquid interface and then introduced into solution by interfacial stresses. In this paper, protein films formed at the air-liquid interface by two mAbs were disrupted by puncturing them with a microscopic needle, and the subsequent reconstitution of the film was observed in real-time by Brewster angle microscopy. Our results indicate that film reconstitution pace depends on mAb bulk concentration. Numerical modeling gives a quantitative prediction of the surface reconstitution. By extrapolating the model to concentrations typical for pharmaceutical formulations (>30 mg/mL) reconstitution timescales of the protein films can be estimated to be shorter than 0.01 s. Moreover, the effect of polysorbate 80 addition on protein film was studied. Film reconstitution measurements revealed that polysorbate 80 inhibits the film reconstitution process and breaks up the previously formed film.

Long-term stability predictions of therapeutic monoclonal antibodies in solution using Arrhenius-based kinetics.

Long-term stability of monoclonal antibodies to be used as biologics is a key aspect in their development. Therefore, its possible early prediction from accelerated stability studies is of major interest, despite currently being regarded as not sufficiently robust. In this work, using a combination of accelerated stability studies (up to 6 months) and first order degradation kinetic model, we are able to predict the long-term stability (up to 3 years) of multiple monoclonal antibody formulations. More specifically, we can robustly predict the long-term stability behaviour of a protein at the intended storage condition (5 °C), based on up to six months of data obtained for multiple quality attributes from different temperatures, usually from intended (5 °C), accelerated (25 °C) and stress conditions (40 °C). We have performed stability studies and evaluated the stability data of several mAbs including IgG1, IgG2, and fusion proteins, and validated our model by overlaying the 95% prediction interval and experimental stability data from up to 36 months. We demonstrated improved robustness, speed and accuracy of kinetic long-term stability prediction as compared to classical linear extrapolation used today, which justifies long-term stability prediction and shelf-life extrapolation for some biologics such as monoclonal antibodies. This work aims to contribute towards further development and refinement of the regulatory landscape that could steer toward allowing extrapolation for biologics during the developmental phase, clinical phase, and also in marketing authorisation applications, as already established today for small molecules.

Application of lectin immobilized on polyHIPE monoliths for bioprocess monitoring of glycosylated proteins.

In-process monitoring of glycosylated protein concentration becomes very important with the introduction of perfusion bioprocesses. Affinity chromatography based on lectins allows selective monitoring when carbohydrates are accessible on the protein surface. In this work, we immobilized lectin on polyHIPE type of monoliths and implemented it for bioprocess monitoring. A spacer was introduced to lectin, which increased binding kinetics toward Fc-fusion protein, demonstrated by bio-layer interferometry. Furthermore, complete desorption using 0.25 M galactose was shown. Affinity column exhibited linearity in the range between 0.5 and 8 mg/ml and flow-unaffected binding for the flow-rates between 0.5 and 8 ml/min. Long-term stability over at least four months period was demonstrated. No unspecific binding of culture media components, including host cell proteins and DNA, was detected. Results obtained by affinity column matched concentration values obtained by a reference method.

Surfaces Affect Screening Reliability in Formulation Development of Biologics.

PURPOSE: The ability to predict an antibody's propensity for aggregation is particularly important during product development to ensure the quality and safety of therapeutic antibodies. We demonstrate the role of container surfaces on the aggregation process of three mAbs under elevated temperature and long-term storage conditions in the absence of mechanical stress. METHODS: A systematic study of aggregation is performed for different proteins, vial material, storage temperature, and presence of surfactant. We use size exclusion chromatography and micro-flow imaging to determine the bulk concentration of aggregates, which we combine with optical and atomic force microscopy of vial surfaces to determine the effect of solid-liquid interfaces on the bulk aggregate concentration under different conditions. RESULTS: We show that protein particles under elevated temperature conditions adhere to the vial surfaces, causing a substantial underestimation of aggregation propensity as determined by common methods used in development of biologics. Under actual long-term storage conditions at 5°C, aggregate particles do not adhere to the surface, causing an increase in bulk concentration of particles, which cannot be predicted from elevated temperature screening tests by common methods alone. We also identify specific protein - surface interactions which promote oligomer formation in the nanometre range. CONCLUSIONS: Special care should be taken when interpreting size exclusion and particle count data from stability studies if different temperatures and vial types are involved. We propose a novel combination of methods to characterise vial surfaces and bulk solution for a full understanding of protein aggregation processes in a sample.

Correction to: Impact of Buffer, Protein Concentration and Sucrose Addition on the Aggregation and Particle Formation during Freezing and Thawing.

The statement in the caption to Fig. 1 "Data taken from reference (38)." (Kolhe P, Holding E, Lary A, Chico S, Singh SK. Large-scale freezing of biologics: understanding protein and solute concentration changes in a Cryovessel-part 2. Biopharm International. 2010;23(7):40-9) is erroneous.

Characterisation of protein aggregation with the Smoluchowski coagulation approach for use in biopharmaceuticals.

Protein aggregation is a field of increasing importance in the biopharmaceutical industry. Aggregated particles decrease the effectiveness of the drug and are associated with other risks, such as increased immunogenicity. This article explores the possibility of using the Smoluchowski coagulation equation and similar models in the prediction of aggregate-particle formation. Three different monoclonal antibodies, exhibiting different aggregation pathways, are analysed. Experimental data are complemented with aggregation dynamics calculated by a coagulation model. Different processes are implemented in the coagulation equation approach, needed to cover the actual phenomena observed in the aggregation of biopharmaceuticals, such as the initial conformational change of the native monomer and reversibility of smaller oligomers. When describing the formation of larger particles, the effect of different aggregation kernel parameters on the corresponding particle size distribution is studied. A significant impact of the aggregate fractal nature on overall particle size distribution is also analysed. More generally, this work is aimed to establish a mesoscopic phenomenological approach for characterisation of protein aggregation phenomena in the context of biopharmaceuticals, capable of covering various aggregate size scales from nanometres to micrometres and reach large time-scales, up to years, as needed for drug development.

Impact of Buffer, Protein Concentration and Sucrose Addition on the Aggregation and Particle Formation during Freezing and Thawing.

PURPOSE: This study addresses the effect of freezing and thawing on a therapeutic monoclonal antibody (mAb) solution and the corresponding buffer formulation. Particle formation, crystallization behaviour, morphology changes and cryo-concentration effects were studied after varying the freezing and thawing rates, buffer formulation and protein concentration. The impact of undergoing multiple freeze/thaw (FT)-cycles at controlled and uncontrolled temperature rates on mAb solutions was investigated in terms of particle formation. METHODS: Physicochemical characteristics were analysed by Differential Scanning Calorimetry whereas morphology changes are visualized by cryomicroscopy measurements. Micro Flow Imaging, Archimedes and Dynamic Light Scattering were used to investigate particle formation. RESULTS: Data retrieved in the present study emphasizes the damage caused by multiple FT-cyles and the need for sucrose as a cryoprotectant preventing cold-crystallization specifically at high protein concentrations. Low protein concentrations cause an increase of micron particle formation. Low freezing rates lead to a decreased particle number with increased particle diameter. CONCLUSION: The overall goal of this research is to gain a better understanding of the freezing and thawing behaviour of mAb solutions with the ultimate aim to optimize this process step by reducing the unwanted particle formation, which also includes protein aggregates.

High Throughput Prediction Approach for Monoclonal Antibody Aggregation at High Concentration.

PURPOSE: Characterization of the monoclonal antibody aggregation process and identification of stability factors that could be used as indicators of aggregation propensity with an emphasis on a large number of samples and low protein material consumption. METHODS: Differential scanning calorimetry, dynamic light scattering and size exclusion chromatography were used as the main methodological approaches. Conformational stability, colloidal stability and aggregation kinetics were assessed for two different IgG monoclonal antibody (mAbs) subclasses. Aggregation was induced by exposing the mAbs to 55°C for 3 weeks. mAb samples were prepared in different formulations and concentrations from 1 mg/mL to 50 mg/mL. RESULTS: High temperature stress of mAb samples revealed that monoclonal antibodies followed first order aggregation kinetics, which suggests that the rate-limiting step of monomer loss was unimolecular. Conformational stability of mAbs was estimated with denaturation temperature measurements. Colloidal stability was assessed with dynamic interaction parameter k D . The correlation between aggregation kinetics and colloidal and conformational stability factors was evaluated and the dynamic interaction parameter was found to be a promising predictor of aggregation propensity of monoclonal antibodies. The meaning of using an intermolecular interaction parameter for prediction of what is essentially a unimolecular process is also discussed. CONCLUSIONS: This work estimates the significance of different predictors of aggregation propensity at high concentrations as a part of a high throughput, low resource screening method and is a contribution towards determining protein aggregation phenomena in actual systems used for the development and production of biopharmaceuticals.

Biosimilar structural comparability assessment by NMR: from small proteins to monoclonal antibodies.

Biosimilar drug products must have a demonstrated similarity with respect to the reference product's molecules in order to ensure both the effectiveness of the drug and the patients' safety. In this paper the fusion framework of a highly sensitive NMR fingerprinting approach for conformational changes and mathematically-based biosimilarity metrics is introduced. The final goal is to translate the complex spectral information into biosimilarity scores, which are then used to estimate the degree of similarity between the biosimilar and the reference product. The proposed method was successfully applied to a small protein, i.e., filgrastim (neutropenia treatment), which is the first biosimilar approved in the United States, and a relatively large protein, i.e., monoclonal antibody rituximab (lymphoma treatment). This innovative approach introduces a new level of sensitivity to structural changes that are induced by, e.g., a small pH shift or other changes in the protein formulation.

Extracellular vesicles concentration is a promising and important parameter for industrial bioprocess monitoring.

Extracellular vesicles (EVs) are membrane vesicles that are produced by cells to be released into their microenvironment. In this study, we present the EV concentration as a new factor for optimization of industrial bioprocess control. The release of EVs depends on many cell properties, including cell activation and stress status, and cell death. Therefore, the EV concentration might provide a readout for identification of the cell state and the conditions during a bioprocess. Our data show that the EV concentration increased during the bioprocess, which indicated deteriorating conditions in the bioreactor. This increase in EV concentration in the fermentation broth was the consequence of two different processes: cell activation, and cell death. However, the release of EVs from activated living cells had a much weaker impact on EV concentration in the bioreactor than those released during cell death. EVs and cells in the bioprocess environment were quantified by flow cytometry. The most accurate data were obtained directly from unprocessed samples, making the monitoring of the EV concentration a rapid, easy, and cheap method. These EV concentrations reflect the conditions in the bioreactor and provide new information regarding the state of the bioprocess. Therefore, we suggest EV concentration as a new and important parameter for the monitoring of industrial bioprocesses.

Hofmeister Effects in Monoclonal Antibody Solution Interactions.

By using static and dynamic light scattering (SLS and DLS), we investigate the effect of ion specificity and solution conditions on the solution behavior of monoclonal antibodies (mAbs). The extracted second virial coefficient, a global measure of the strength of protein-protein interactions, shows a complicated, nonmonotonic behavior. It can be connected on one side with the Hofmeister effect, and on the other with the interplay of screening and charge fluctuations in inhomogeneous, patchy charge distribution of these particular proteins. Although direct quantification in terms of the underlying long and short-range potentials is out of reach, the observed effects do point toward important features of mAbs solution aggregation processes that are governed by the identity of the solution ions as well as by details of the charge distribution of interacting proteins.

Colloidal interactions between monoclonal antibodies in aqueous solutions.

Colloidal interactions between proteins determine the behavior and stability of globular proteins such as monoclonal antibodies (mAbs) against their propensity to cluster formation in solution. We study interactions between these proteins through their dilute solution behavior. Experiments to quantify intermolecular interactions were done using Dynamic and Static Light Scattering (DLS and SLS) in a high-throughput manner in parallel with zeta potential measurements with Laser Doppler Electrophoresis method (M3-PALS). This approach offers a rapid indirect determination of colloidal interactions through their measured second virial coefficient. Electrostatic part of the DLVO interaction was conveniently parameterized via the corresponding surface charge and/or surface potential, while the van der Waals interactions were parameterized via their Hamaker coefficient, both as functions of ionic strength and pH of the bathing solution. This parametrization of protein-protein interactions improves our understanding of mAb assembly and provides a means for its control by solution parameter variation. Additionally, our results also provide a consistency check and validation of applicability of the DLVO theory in mAbs solution assembly processes.

Recognition of human tumor necrosis factor α (TNF-α) by therapeutic antibody fragment: energetics and structural features.

Human tumor necrosis factor α (TNF-α) exists in its functional state as a homotrimeric protein and is involved in inflammation processes and immune response of a human organism. Overproduction of TNF-α results in the development of chronic autoimmune diseases that can be successfully treated by inhibitors such as monoclonal antibodies. However, the nature of antibody-TNF-α recognition remains elusive due to insufficient understanding of its molecular driving forces. Therefore, we studied the energetics of binding of a therapeutic antibody fragment (Fab) to the native and non-native forms of TNF-α by employing calorimetric and spectroscopic methods. Global thermodynamic analysis of data obtained from the corresponding binding and urea-induced denaturation experiments has been supported by structural modeling. We demonstrate that the observed high affinity binding of Fab to TNF-α is an enthalpy-driven process due mainly to specific noncovalent interactions taking place at the TNF-α-Fab binding interface. It is coupled to entropically unfavorable conformational changes and accompanied by entropically favorable solvation contributions. Moreover, the three-state model analysis of TNF-α unfolding shows that at physiological concentrations, TNF-α may exist not only as a biologically active trimer but also as an inactive monomer. It further suggests that even small changes of TNF-α concentration could have a considerable effect on the TNF-α activity. We believe that this study sets the energetic basis for understanding of TNF-α inhibition by antibodies and its unfolding linked with the concentration-dependent activity regulation.

Revealing fosfomycin primary effect on Staphylococcus aureus transcriptome: modulation of cell envelope biosynthesis and phosphoenolpyruvate induced starvation.

BACKGROUND: Staphylococcus aureus is a highly adaptable human pathogen and there is a constant search for effective antibiotics. Fosfomycin is a potent irreversible inhibitor of MurA, an enolpyruvyl transferase that uses phosphoenolpyruvate as substrate. The goal of this study was to identify the pathways and processes primarily affected by fosfomycin at the genome-wide transcriptome level to aid development of new drugs. RESULTS: S. aureus ATCC 29213 cells were treated with sub-MIC concentrations of fosfomycin and harvested at 10, 20 and 40 minutes after treatment. S. aureus GeneChip statistical data analysis was complemented by gene set enrichment analysis. A visualization tool for mapping gene expression data into biological pathways was developed in order to identify the metabolic processes affected by fosfomycin. We have shown that the number of significantly differentially expressed genes in treated cultures increased with time and with increasing fosfomycin concentration. The target pathway - peptidoglycan biosynthesis - was upregulated following fosfomycin treatment. Modulation of transport processes, cofactor biosynthesis, energy metabolism and nucleic acid biosynthesis was also observed. CONCLUSIONS: Several pathways and genes downregulated by fosfomycin have been identified, in contrast to previously described cell wall active antibiotics, and was explained by starvation response induced by phosphoenolpyruvate accumulation. Transcriptomic profiling, in combination with meta-analysis, has been shown to be a valuable tool in determining bacterial response to a specific antibiotic.

Drug interaction potential of 2-((3,4-dichlorophenethyl)(propyl)amino)-1-(pyridin-3-yl)ethanol (LK-935), the novel nonstatin-type cholesterol-lowering agent.

The widely prescribed lipid-lowering statins are considered to be relatively safe drugs. However, the risk of severe myopathy and drug interactions as a consequence of statin therapy provides a challenge for development of novel cholesterol-lowering agents, targeting enzymes other than HMG-CoA reductase. The novel pyridylethanol-(phenylethyl)amine derivative, (2-((3,4-dichlorophenethyl)(propyl)-amino)-1-(pyridin-3-yl)ethanol (LK-935), blocking lanosterol 14alpha-demethylase, was demonstrated to efficiently reduce cholesterol biosynthesis. The drug interaction potential of LK-935 was investigated and compared with that of atorvastatin and rosuvastatin in primary human hepatocytes. Clear evidence was provided for the induction of CYP3A4 by LK-935. LK-935 was proved to be a potent human pregnane X receptor (hPXR) activator as a prerequisite for the transcriptional activation of CYP3A4 gene; however, the rapid metabolism of LK-935 in primary hepatocytes prevented maximal CYP3A4 induction. Therefore, the induction of CYP3A4 by LK-935 may be prone to mild or negligible drug interactions. However, because CYP3A4 and also CYP2C9 play a significant role in LK-935 metabolism, the inhibition of these cytochromes P450 by coadministered drugs may lead to some increase in the LK-935 concentration required for the potent induction of CYP3A4. Rosuvastatin was found to increase human constitutive androstane receptor (hCAR)-mediated transcription of CYP3A4, CYP2C9, and CYP2B6 genes, predicting the consequent potential for drug interactions with several coadministered drugs. Activation of hCAR and hPXR by atorvastatin and the subsequent induction of not only CYP2B6 and CYP3A4 but also of CYP2C9 present an additional target by which atorvastatin, a widely used cholesterol-lowering drug, can modify the kinetics of numerous drugs.

The Sterolgene v0 cDNA microarray: a systemic approach to studies of cholesterol homeostasis and drug metabolism.

BACKGROUND: Cholesterol homeostasis and xenobiotic metabolism are complex biological processes, which are difficult to study with traditional methods. Deciphering complex regulation and response of these two processes to different factors is crucial also for understanding of disease development. Systems biology tools as are microarrays can importantly contribute to this knowledge and can also discover novel interactions between the two processes. RESULTS: We have developed a low density Sterolgene v0 cDNA microarray dedicated to studies of cholesterol homeostasis and drug metabolism in the mouse. To illustrate its performance, we have analyzed mouse liver samples from studies focused on regulation of cholesterol homeostasis and drug metabolism by diet, drugs and inflammation. We observed down-regulation of cholesterol biosynthesis during fasting and high-cholesterol diet and subsequent up-regulation by inflammation. Drug metabolism was down-regulated by fasting and inflammation, but up-regulated by phenobarbital treatment and high-cholesterol diet. Additionally, the performance of the Sterolgene v0 was compared to the two commercial high density microarray platforms: the Agilent cDNA (G4104A) and the Affymetrix MOE430A GeneChip. We hybridized identical RNA samples to the commercial microarrays and showed that the performance of Sterolgene is comparable to commercial arrays in terms of detection of changes in cholesterol homeostasis and drug metabolism. CONCLUSION: Using the Sterolgene v0 microarray we were able to detect important changes in cholesterol homeostasis and drug metabolism caused by diet, drugs and inflammation. Together with its next generations the Sterolgene microarrays represent original and dedicated tools enabling focused and cost effective studies of cholesterol homeostasis and drug metabolism. These microarrays have the potential of being further developed into screening or diagnostic tools.

TNF-alpha interferes with lipid homeostasis and activates acute and proatherogenic processes.

The interaction between disrupted lipid homeostasis and immune response is implicated in the pathogenesis of several diseases, but the molecular bridges between the major players are still a matter of controversy. Our systemic study of the inflammatory cytokine tumor necrosis factor-alpha (TNF-alpha) in the livers of mice exposed to 20-h cytokine/fasting for the first time shows that TNF-alpha interferes with adaptation to fasting and activates harmful proatherogenic pathways, partially through interaction with the insulin-Insig-sterol regulatory element binding protein (Srebp) signaling pathway. In addition to the increased expression of acute-phase inflammatory genes, the most prominent alterations represent modified lipid homeostasis observed on the gene expression and metabolite levels. These include reduction of HDL-cholesterol, increase of LDL-cholesterol, and elevated expression of cholesterogenic genes, accompanied by increase of potentially harmful precholesterol metabolites and suppression of cholesterol elimination through bile acids, likely by farnesoid X receptor-independent mechanisms. On the transcriptional level, a shift from fatty oxidation toward fatty acid synthesis is observed. The concept of the influence of TNF-alpha on the Srebp regulatory network, followed by downstream effects on sterol metabolism, is novel. Observed acute alterations in lipid metabolism are in agreement with chronic disturbances found in patients.

The cooperative role of membrane skeleton and bilayer in the mechanical behaviour of red blood cells.

Red blood cell (RBC) shape, behaviour and deformability can be consistently accounted for by a model for the elastic properties of the RBC membrane that includes the elasticity of the membrane skeleton in dilation and shear, and the local and nonlocal resistance of the bilayer to bending. The role of the corresponding energy terms in different RBC shape and deformation situations is analyzed. RBC shape transformations are compared to the shape transformations of phospholipid vesicles that are driven by the difference between the equilibrium areas of the bilayer leaflets (DeltaA0). It is deduced that the skeleton energy contributions play a crucial role in the formation of an echinocyte. The effect of a transformation of the natural biconcave RBC shape into an echinocyte on its resistance to entry into capillary-sized cylindrical tubes is analyzed. It is shown that, during the aspiration of an echinocyte into a pipette, there are two competing skeleton deformation effects, which arise due to skeleton density changes, one due to spicule formation and the other due to deformation induced by micropipette aspiration. Furthermore, the shift of the observed dependence of the projection length on the aspiration pressure of more crenated cells towards higher aspiration pressures can be accounted for by an increase of the equilibrium area difference DeltaA0 and consequent modification of the nonlocal contribution to the cell elastic energy.

Erythrocyte deformability and microhematuria in children and adolescents.

The aim of this study was to investigate whether erythrocyte deformability is higher in otherwise healthy children and adolescents with asymptomatic isolated glomerular microhematuria and no clinical or laboratory signs indicating renal disorder. Erythrocyte deformability in 33 children and adolescents with unexplained asymptomatic isolated glomerular microhematuria (study group) was compared with erythrocyte deformability in 133 individuals without urinary tract disease and without microhematuria (control group), 26 patients with microhematuria and IgA nephropathy (IgA nephropathy group), and 31 children and adolescents with benign familial hematuria (benign familial hematuria group). The erythrocyte and buffer filtration time was measured, the erythrocyte-to-buffer filtration time ratio calculated, and, on the basis thereof, erythrocyte deformability was estimated as an inverse proportion of the erythrocyte-to-buffer filtration time ratio in all subjects. The erythrocyte-to-buffer filtration time ratio increased with age in all groups (P<0.001). In the study group, the mean erythrocyte-to-buffer filtration time ratio, corrected for age of subjects, was significantly lower than in the control (P=0.042), IgA nephropathy (P=0.004), and benign familial hematuria groups (P= 0.048). Erythrocytes with higher deformability probably pass more easily through the glomerular basement membrane that is assumed to be normal, in which case the mechanism of asymptomatic isolated glomerular microhematuria could be explained by higher erythrocyte deformability.