Analytical Platform for Monitoring Aggregation of Monoclonal Antibody Therapeutics

Aggregation of therapeutic monoclonal antibodies due to thermal and air/liquid interfacial agitation stress: Occurrence, stability assessment strategies, aggregation mechanism, influencing factors, and ways to enhance stability

Therapeutic proteins, such as monoclonal antibodies (mAbs) are known to undergo stability related issues during various stages of product life cycle resulting in the formation of aggregates and fragments. Aggregates of mAb might result in reduced therapeutic activity and could cause various adverse immunogenic responses. Sample containing mAb undergo aggregation due to various types of stress factors, and there is always a continuous interest among researchers and manufacturers to determine the effect of different factors on the stability of mAb. Thermal stress and air/liquid interfacial agitation stress are among two of the common stress factors to which samples containing mAb are exposed to during various stages. Initial part of this review articles aims to provide a generalized understanding of aggregation of mAb such as size ranges of aggregates, aggregate types, stress factors, analytical techniques, permissible aggregate limits, and stability assessment methods. This article further aims to explain different aspects associated with aggregation of mAb in liquid samples due to thermal and air/liquid interfacial agitation stress. Under each stress category, the occurrence of stress during product life cycle, type of aggregates formed, mechanism of aggregation, strategies used by various researchers to expose mAb containing samples to stress, different factors affecting aggregation, fate of aggregates in human body fluids, and strategies used to enhance mAb stability has been explained in detail. The authors hope that this article provides a detailed understanding about stability of mAb due to thermal and air/liquid interfacial stress with relevance to product life cycle from manufacturing to administration into patients.

Impact of stirring material on formation of submicron and subvisible aggregates in mAbs by quantitative laser diffraction, dynamic light scattering and background membrane imaging

Aggregation of monoclonal antibodies (mAbs) is the driving force for their undesirable immunogenic effects. There are multiple factors responsible for aggregation in therapeutic proteins. One significant cause is the process-related shear and interfacial stress generated due to impellers and stirrers. This investigation focuses on understanding the possible aggregation arising upon stirring mAb formulations using stirrers made of different materials. We used quantitative laser diffraction (qLD) to monitor and quantify the stirring induced formation of submicron and subvisible aggregates in the size range from 100 nm to 10 µm. We analysed various aspects of aggregate generation, such as onset of aggregation, particle size distribution, and concentration of aggregates generated using stirrers of different materials. We observed that mixing with stainless steel stirrers resulted in a quicker onset of aggregation and led to significantly higher concentrations of aggregates. Analysis of the stirred samples using dynamic light scattering (DLS) and background imaging technique (BMI) were conducted to complement the qLD analysis. All the three techniques resulted in a similar trend, showing presence of larger and higher quantities of aggregates in steel stirred samples, as compared to those stirred using PEEK and glass. Additionally, we performed SEC-HPLC to quantify the soluble fraction of monomer and recorded that the least amount was present in the steel stirred samples. This work highlights the need for optimizing the materials used for fabricating the stirrers/impellers.

Direct Affinity Ligand Immobilization onto Bare Iron Oxide Nanoparticles Enables Efficient Magnetic Separation of Antibodies

Magnetic separation is a promising alternative to chromatography for enhancing the downstream processing (DSP) of monoclonal antibodies (mAbs). However, there is a lack of efficient magnetic particles for successful application. Aiming to fill this gap, we demonstrate the suitability of bare iron oxide nanoparticles (BION) with physical site-directed immobilization of an engineered Protein A affinity ligand (rSpA) as an innovative magnetic material. The rSpA ligand contains a short peptide tag that enables the direct and stable immobilization onto the uncoated BION surface without commonly required laborious particle activation. The resulting BION@rSpA have beneficial characteristics outperforming conventional Protein A-functionalized magnetic particles: a simple, fast, low-cost synthesis, a particle size in the nanometer range with a large effective specific surface area enabling large immunoglobulin G (IgG) binding capacity, and a high magnetophoretic velocity advantageous for fast processing. We further show rapid interactions of IgG with the easily accessible rSpA ligands. The binding of IgG to BION@rSpA is thereby highly selective and not impeded by impurity molecules in perfusion cell culture supernatant. Regarding the subsequent acidic IgG elution from BION@rSpA@IgG, we observed a hampering pH increase caused by the protonation of large iron oxide surfaces after concentrating the particles in 100 mM sodium acetate buffer. However, the pH can be stabilized by adding 50 mM glycine to the elution buffer, resulting in recoveries above 85% even at high particle concentrations. Our work shows that BION@rSpA enable efficient magnetic mAb separation and could help to overcome emerging bottlenecks in DSP.

A High Threshold of Biotherapeutic Aggregate Numbers is Needed to Induce an Immunogenic Response In Vitro, In Vivo, and in the Clinic

BACKGROUND AND PURPOSE

There is concern that subvisible aggregates in biotherapeutic drug products pose a risk to patient safety. We investigated the threshold of biotherapeutic aggregates needed to induce immunogenic responses.

METHODS AND RESULTS

Highly aggregated samples were tested in cell-based assays and induced cellular responses in a manner that depended on the number of particles. The threshold of immune activation varied by disease state (cancer, rheumatoid arthritis, allergy), concomitant therapies, and particle number. Compared to healthy donors, disease state patients showed an equal or lower response at the late phase (7 days), suggesting they may not have a higher risk of responding to aggregates. Xeno-het mice were used to assess the threshold of immune activation in vivo. Although highly aggregated samples (~ 1,600,000 particles/mL) induced a weak and transient immunogenic response in mice, a 100-fold dilution of this sample (~ 16,000 particles/mL) did not induce immunogenicity. To confirm this result, subvisible particles (up to ~ 18,000 particles/mL, containing aggregates and silicone oil droplets) produced under representative administration practices (created upon infusion of a drug product through an IV catheter) did not induce a response in cell-based assays or appear to increase the rate of adverse events or immunogenicity during phase 3 clinical trials.

CONCLUSION

The ability of biotherapeutic aggregates to elicit an immune response in vitro, in vivo, and in the clinic depends on high numbers of particles. This suggests that there is a high threshold for aggregates to induce an immunogenic response which is well beyond that seen in standard biotherapeutic drug products.

What should next-generation analytical platforms for biopharmaceutical production look like?

Biotherapeutic products, particularly complex products such as monoclonal antibodies (mAbs), have as many as 20-30 critical quality attributes (CQAs), thereby requiring a collection of orthogonal, high-resolution analytical tools for characterization and making characterization a resource-intensive task. As discussed in this Opinion, the need to reduce the cost of developing biotherapeutic products and the need to adopt Industry 4.0 and eventually Industry 5.0 paradigms are driving a reappraisal of existing analytical platforms. Next-generation platforms will have reduced offline testing, renewed focus on online testing and real-time monitoring, multiattribute monitoring, and extensive use of advanced data analytics and automation. They will be more complex, more sensitive, resource lean, and more responsive compared with existing platforms.

Real-time detection of mAb aggregates in an integrated downstream process

The implementation of continuous processing in the biopharmaceutical industry is hindered by the scarcity of process analytical technologies (PAT). To monitor and control a continuous process, PAT tools will be crucial to measure real-time product quality attributes such as protein aggregation. Miniaturizing these analytical techniques can increase measurement speed and enable faster decision-making. A fluorescent dye (FD)-based miniaturized sensor has previously been developed: a zigzag microchannel which mixes two streams under 30 s. Bis-ANS and CCVJ, two established FDs, were employed in this micromixer to detect aggregation of the biopharmaceutical monoclonal antibody (mAb). Both FDs were able to robustly detect aggregation levels starting at 2.5%. However, the real-time measurement provided by the microfluidic sensor still needs to be implemented and assessed in an integrated continuous downstream process. In this work, the micromixer is implemented in a lab-scale integrated system for the purification of mAbs, established in an ÄKTA™ unit. A viral inactivation and two polishing steps were reproduced, sending a sample of the product pool after each phase directly to the microfluidic sensor for aggregate detection. An additional UV sensor was connected after the micromixer and an increase in its signal would indicate that aggregates were present in the sample. The at-line miniaturized PAT tool provides a fast aggregation measurement, under 10 min, enabling better process understanding and control.

Efficient separation of IgG from IgM antibodies via conjugated surfactant micelles

Immunoglobulin-G (IgG) (∼150 kDa) antibodies confer longer term immunity against bacterial or viral infections than the heavier IgM's (∼900 kDa), which are generally detectable in blood circulation in response to more recently acquired infections. There may be, however, a time overlap, which is problematic for diagnostic purposes, in the interests of which it is essential to separate IgM's from IgG's. We describe a purification platform, functioning at pH 6.5, containing Tween-20, or Brij-O20, non-ionic detergent micelles, mixed with the sugar-rich detergent dodecyl maltoside (DDM), amino acid monomer tyrosine (Tyr), and conjugated by the amphiphilic complex [(bathophenanthroline)₃: Fe²⁺]. Using conjugated Brij-O20 micelles, with input molar ratio IgG: IgM 9:1, IgG is recovered at 10 °C with 85-90% yield, (by SDS-PAGE densitometry) and ≥95% purity (also by SDS-PAGE), while IgM's are recovered at lower yields (28-34%) and contain small amounts of co-extracted IgG's. Addition of E. coli lysate as an artificial contamination background does not reduce the yield or purity of the recovered IgG. Tween-20/DDM/Tyr micelles lead to IgG purity ≥95% similar to that of Brij-O20, but with lower process yields (64-70%, by densitometry). Chromatographic separation with Protein A or Protein G resins leads to yields comparable to those obtained with Brij-O20 micelles, but with lower purity.

Rapid Estimation of Size-Based Heterogeneity in Monoclonal Antibodies by Machine Learning-Enhanced Dynamic Light Scattering

Aggregation of monoclonal antibody therapeutics is a serious concern that is believed to impact product safety and efficacy. There is a need for analytical approaches that enable rapid estimation of mAb aggregates. Dynamic light scattering (DLS) is a well-established technique for estimating the average size of protein aggregates or for evaluating sample stability. It is usually used to measure the size and size distribution over a wide range of nano- to micro-sized particles using time-dependent fluctuations in the intensity of scattered light arising from the Brownian motion of particles. In this study, we present a novel DLS-based approach that allows us to quantify the relative percentage of multimers (monomer, dimer, trimer, and tetramer) in a monoclonal antibody (mAb) therapeutic product. The proposed approach uses a machine learning (ML) algorithm and regression to model the system and predict the amount of relevant species such as monomer, dimer, trimer, and tetramer of a mAb in the size range of 10-100 nm. The proposed DLS-ML technique compares favorably to all potential alternatives with respect to the key method attributes, including per sample cost of analysis, per sample time of data acquisition along with ML-based aggregate prediction (<2 min), sample requirements (<3 μg), and user-friendliness of analysis. The proposed rapid method can serve as an orthogonal tool to size exclusion chromatography, which is the current industry workhorse for aggregate assessment.

Sensitivity and Uncertainty Analysis of Micro-Flow Imaging for Sub-Visible Particle Measurements Using Artificial Neural Network

PURPOSE

During biopharmaceutical drug manufacturing, storage, and distribution, proteins in both liquid and solid dosage forms go through various processes that could lead to protein aggregation. The extent of aggregation in the sub-micron range can be measured by analyzing a liquid or post-reconstituted powder sample using Micro-Flow Imaging (MFI) technique. MFI is widely used in biopharmaceutical industries due to its high sensitivity in detecting and analyzing particle size distribution. However, the MFI's sensitivity to various factors makes accurate measurement challenging. Therefore, in light of the inherent variability of the method, this work aims to explore the capabilities of an adopted coupled sensitivity analysis and machine learning algorithm to quantify the influencing factors on the formed sub-visible particles and method variability.

METHODS

The proposed algorithm consists of two interconnected components, namely a surrogate model with a neural network and a sensitivity analyzer. A machine learning tool based on artificial neural networks (ANN) is constructed with MFI data. The best fit with an optimized configuration is found. Sensitivity and uncertainty analysis is performed using this network as the surrogate model to understand the impacts of input parameters on MFI data.

RESULTS

Results reveal the most impactful reconstitution preparation factors and others that are masked by the instrument variabilities. It is shown that instrument inaccuracy is a function of size category, with higher variabilities associated with larger size ranges.

CONCLUSION

Utilizing this tool while assessing the sensitivity of outputs to various parameters, measurement variabilities for analytical characterization tests can be quantified.

Identification of Hetero-aggregates in Antibody Co-formulations by Multi-dimensional Liquid Chromatography Coupled to Mass Spectrometry

Antibody combination therapies have become viable therapeutic treatment options for certain severe diseases such as cancer. The co-formulation production approach is intrinsically associated with more complex drug product variant profiles and creates more challenges for analytical control of drug product quality. In addition to various individual quality attributes, those arising from the interactions between the antibodies also potentially emerge through co-formulation. In this study, we describe the development of a widely applicable multi-dimensional liquid chromatography coupled to tandem mass spectrometry method for antibody homo- versus hetero-aggregate characterization. The co-formulation of trastuzumab and pertuzumab was used, a challenging model system, comprising two monoclonal antibodies with very similar physicochemical properties. The data presented demonstrate the high stability of the co-formulation, where only minor aggregate formation is observed upon product storage and accelerated temperature or light-stress conditions. The results also show that the homo- and hetero-aggregates, formed in low and comparable proportions, are only marginally impacted by the formulation and product storage conditions. No preferential formation of hetero-aggregates, in comparison to the already existing pertuzumab and trastuzumab homo-aggregates, was observed.

Bioprocessing of recombinant proteins from Escherichia coli inclusion bodies: insights from structure-function relationship for novel applications

The formation of inclusion bodies (IBs) during expression of recombinant therapeutic proteins using E. coli is a significant hurdle in producing high-quality, safe, and efficacious medicines. The improved understanding of the structure-function relationship of the IBs has resulted in the development of novel biotechnologies that have streamlined the isolation, solubilization, refolding, and purification of the active functional proteins from the bacterial IBs. Together, this overall effort promises to radically improve the scope of experimental biology of therapeutic protein production and expand new prospects in IBs usage. Notably, the IBs are increasingly used for applications in more pristine areas such as drug delivery and material sciences. In this review, we intend to provide a comprehensive picture of the bio-processing of bacterial IBs, including assessing critical gaps that still need to be addressed and potential solutions to overcome them. We expect this review to be a useful resource for those working in the area of protein refolding and therapeutic protein production.

Practical Use of Quartz Crystal Microbalance Monitoring in Cartilage Tissue Engineering

Quartz crystal microbalance (QCM) is a real-time, nanogram-accurate technique for analyzing various processes on biomaterial surfaces. QCM has proven to be an excellent tool in tissue engineering as it can monitor key parameters in developing cellular scaffolds. This review focuses on the use of QCM in the tissue engineering of cartilage. It begins with a brief discussion of biomaterials and the current state of the art in scaffold development for cartilage tissue engineering, followed by a summary of the potential uses of QCM in cartilage tissue engineering. This includes monitoring interactions with extracellular matrix components, adsorption of proteins onto biomaterials, and biomaterial–cell interactions. In the last part of the review, the material selection problem in tissue engineering is highlighted, emphasizing the importance of surface nanotopography, the role of nanofilms, and utilization of QCM as a “screening” tool to improve the material selection process. A step-by-step process for scaffold design is proposed, as well as the fabrication of thin nanofilms in a layer-by-layer manner using QCM. Finally, future trends of QCM application as a “screening” method for 3D printing of cellular scaffolds are envisioned.

Simultaneous quantification of oligo-nucleic acids and a ferritin nanocage by size-exclusion chromatography hyphenated to inductively coupled plasma mass spectrometry for developing drug delivery systems

An analytical methodology, which can quantify nucleic acids, ferritin nanocages, and their complexes in a single injection, was established by means of size-exclusion chromatography hyphenated with inductively coupled plasma mass spectrometry (SEC-ICP-MS). In this study, several oligo-nucleic acids and ferritin (a human-derived cage-shaped protein) were used as model compounds of nucleic acid drugs (NAD) and drug delivery system (DDS) carriers, respectively. A fraction based on the nucleic acid-ferritin complex was completely distinguished from one based on free nucleic acids by SEC separation. The nucleic acids and ferritin were quantified based on the number of phosphorus and sulfur atoms, respectively. The quantification was carried out by an external calibration method using a series of elemental standard solutions without preparing designated standard materials for each drug candidate. The analytical performance, including sensitivity and accuracy, was evaluated to be appropriate for evaluating the medicines already launched in the market. As demonstrated in the latter part of this study, the encapsulation mechanism is possibly regulated by not only the averaged molecular size of nucleic acids but also the surface charge related to the number of (deoxy-) ribonucleotides. We believe that the methodology presented in this study has the potential to accelerate the development of new modalities based on NAD-DDS to realize therapies in the future.

Image Analysis Algorithm-Based Platform for Determining Micron and Higher Aggregate Size Distribution of Therapeutic IgG Using Brightfield and Fluorescence Microscope Images

A platform for determining size distribution of micron (1-100 μm) and larger (> 100 μm) aggregates of therapeutic IgG has been established by using image processing algorithms for brightfield and fluorescence microscope images. The algorithm for brightfield images involved conversion to grayscale followed by pixel-based and size-based thresholding. Morphological operations were then applied and the size distribution of aggregates were extracted. Fluorescence images of the aggregates of mAb tagged by a fluorescent dye were captured using widefield fluorescence microscope, confocal laser scanning microscope, and Cytell Cell Imaging System and the images were processed using a series of denoising steps followed by thresholding and morphological operations. The samples were subjected to different stresses, among which the aggregates were visible in the microscope for sample subjected to bubbling, stirring, and temperature. The images of these aggregates were effectively denoised and the size distribution of aggregates was analyzed using the algorithm. The overall aggregate size distribution obtained by image processing ranged in the micron and higher size range. The size obtained from brightfield image processing was validated using images of liquid chromatography resins. Further, the aggregate size distribution obtained using image processing was compared with experimental techniques such as Mastersizer 2000 and Micro Flow Imaging. It was found that analysis of IgG aggregates using image processing could serve as an orthogonal methodology to the existing approaches.

Rapid aggregation of therapeutic monoclonal antibodies by bubbling induced air/liquid interfacial and agitation stress at different conditions

Degradation of therapeutic monoclonal antibodies (mAb) due to interfacial agitation through air bubbling was investigated. Samples containing mAb in phosphate buffered saline were subjected to rapid bubbling by using a peristaltic pump at an air flow rate of 11.5 mL/min. Samples were analyzed by visual observation, UV-Vis, fluorescence, circular dichroism and infrared spectroscopy, size-exclusion chromatography (SEC), dynamic light scattering, microscopy, and cell-based activity assays. The stressed samples showed increasing turbidity with bubbling time, with mAb1 showing a protein loss of 53% in the supernatant at the latest time point (240 min), indicating formation of sub-visible and visible aggregates. Aggregate rich samples exhibited altered secondary structure and higher hydrophobicity with 40% reduction in activity. The supernatants of the stressed samples showed unchanged secondary and tertiary structure without the presence of any oligomers in SEC. Furthermore, the impact of various factors that could affect aggregation was investigated and it was found that the extent of aggregation was affected by protein concentration, sample volume, presence of surfactants, temperature, air flow rate, and presence of silicone oil. In conclusion, exposure to air/liquid interfacial stress through bubbling into liquid mAb samples effectively generated sub-visible and visible aggregates, making air bubbling an attractive approach for interfacial stress degradation studies of mAbs.

Sensitive, homogeneous, and label-free protein-probe assay for antibody aggregation and thermal stability studies

Protein aggregation is a spontaneous process affected by multiple external and internal properties, such as buffer composition and storage temperature. Aggregation of protein-based drugs can endanger patient safety due, for example, to increased immunogenicity. Aggregation can also inactivate protein drugs and prevent target engagement, and thus regulatory requirements are strict regarding drug stability monitoring during manufacturing and storage. Many of the current technologies for aggregation monitoring are time- and material-consuming and require specific instruments and expertise. These types of assays are not only expensive, but also unsuitable for larger sample panels. Here we report a label-free time-resolved luminescence-based method using an external Eu³⁺-conjugated probe for the simple and fast detection of protein stability and aggregation. We focused on monitoring the properties of IgG, which is a common format for biological drugs. The Protein-Probe assay enables IgG aggregation detection with a simple single-well mix-and-measure assay performed at room temperature. Further information can be obtained in a thermal ramping, where IgG thermal stability is monitored. We showed that with the Protein-Probe, trastuzumab aggregation was detected already after 18 hours of storage at 60°C, 4 to 8 days earlier compared to SYPRO Orange- and UV250-based assays, respectively. The ultra-high sensitivity of less than 0.1% IgG aggregates enables the Protein-Probe to reduce assay time and material consumption compared to existing techniques.

Size-based Degradation of Therapeutic Proteins - Mechanisms, Modelling and Control

Protein therapeutics are in great demand due to their effectiveness towards hard-to-treat diseases. Despite their high demand, these bio-therapeutics are very susceptible to degradation via aggregation, fragmentation, oxidation, and reduction, all of which are very likely to affect the quality and efficacy of the product. Mechanisms and modelling of these degradation (aggregation and fragmentation) pathways is critical for gaining a deeper understanding of stability of these products. This review aims to provide a summary of major developments that have occurred towards unravelling the mechanisms of size-based protein degradation (particularly aggregation and fragmentation), modelling of these size-based degradation pathways, and their control. Major caveats that remain in our understanding and control of size-based protein degradation have also been presented and discussed.

The application of laboratory-based analytical tools and techniques for the quality assessment and improvement of commercial antivenoms used in the treatment of snakebite envenomation

Snakebite envenomation is a public health problem of high impact, particularly for the developing world. Antivenom, which contains whole or protease-digested immunoglobulin G, purified from the plasma of hyper-immunized animals (mainly horses), is the mainstay for the treatment of snakebite envenomation. The success of antivenom therapy depends upon its ability to abrogate or reduce the local and systemic toxicity of envenomation. In addition, antivenom administration must be safe for the patients. Therefore, antivenom manufacturers must ensure that these products are effective and safe in the treatment of envenomations. Antivenom efficacy and safety are determined by the physicochemical characteristics of formulations, purity of the immunoglobulin fragments and antibodies, presence of protein aggregates, endotoxin burden, preservative load, and batch to batch variation, as well as on the ability to neutralize the most important toxins of the venoms against which the antivenom is designed. In this context, recent studies have shown that laboratory-based simple analytical techniques, for example, size exclusion chromatography, sodium dodecyl sulphate polyacrylamide gel electrophoresis, mass spectrometry, immunological profiling including immuno-turbidimetry and enzyme-linked immunosorbent assays, Western blotting, immune-chromatographic technique coupled to mass spectrometry analysis, reverse-phase high performance liquid chromatography, spectrofluorometric analysis, in vitro neutralization of venom enzymatic activities, and other methodologies, can be applied for the assessment of antivenom quality, safety, stability, and efficacy. This article reviews the usefulness of different analytical techniques for the quality assessment of commercial antivenoms. It is suggested that these tests should be applied for screening the quality of commercial antivenoms before their preclinical and clinical assessment.

Novel semi-automated fluorescence microscope imaging algorithm for monitoring IgG aggregates in serum

Analysis of therapeutic IgG aggregates in serum is a potential area of investigation as it can give deeper insights about the function, immunogenic issues and protein interaction associated with the aggregates. To overcome various complexities associated with the existing analytical techniques for analyzing aggregates in serum, a novel florescence microscopy-based image processing approach was developed. The monoclonal antibody (mAb) was tagged with a fluorescent dye, fluorescein isothiocyanate (FITC). Aggregates, generated by stirring, were spiked into serum and images were captured at various time points. After denoising, thresholding by weighted median, 1D Otsu, and 2D Otsu was attempted and a modified 2D Otsu, a new mode of thresholding, was developed. This thresholding method was found to be highly effective in removing noises and retaining analyte sizes. Out of 0–255, the optimized threshold value obtained for the images discussed in modified 2D Otsu was 9 while 2D Otsu’s overestimated values were 38 and 48. Other morphological operations were applied after thresholding and the area, perimeter, circularity, and radii of the aggregates in these images were calculated. The proposed algorithm offers an approach for analysis of aggregates in serum that is simpler to implement and is complementary to existing approaches.

Freeze thaw and lyophilization induced alteration in mAb therapeutics: Trastuzumab as a case study

Long-term stability of therapeutic monoclonal antibody (mAb) products is necessary for their successful commercialization. Freeze-thaw (F/T) operations are often performed for a mAb product during processing, storage and distribution. Lyophilization (Lyo) is another unit operation that is commonly used for drug product manufacturing of mAbs. This paper aims to explore the impact of these operations on structure and function of a mAb therapeutic, as well as of biosimilars. Trastuzumab innovator and its five biosimilars were analysed for aggregation, charge heterogeneity, secondary structure, binding kinetics, and potency after each freeze-thaw and lyophilization cycle. It is observed that both F/T and Lyo induce protein aggregation, which in turn causes perturbations in the biological potency of the mAb therapeutic. The average value of the percentage of aggregation increased from 0.6 % (week 1) to 5.3 % (week 10) in F/T study and from 0.8 % (week 1) to 10.1 % (week 10) in Lyo study. The acidic pool increased from 26.5 % (week 1) to 44.4 % (week 10) and the basic variants from 13.9 % (week 1) to 24.0 % (week 10) in F/T study. Similarly, acidic pool increased from 27.1 % (week 1) to 42.0 % (week 10) and basic variants from 14.8 % (week 1) to 24.4 % (week 10) in Lyo study. The average percentage of beta-sheet increased from 58.4 % (week 1) to 60.9 % (week 10) in F/T study and from 59.7 % (week 1) to 72.6 % (week 10) in Lyo study. Lower binding affinity was found in week 7 as compared to week 1 in Lyo study whereas no change in binding affinity was observed in the F/T study. The average potency value gradually decreased from 0.97IU/ ml (week 1) to 0.75IU/ ml (week 10) in F/T study and from 1.0IU/ ml (week 1) to 0.66IU/ ml (week 10) in Lyo study. Results indicate that lyophilization has a bigger impact on binding affinity than freeze thaw and as expected, the impact was comparable across the innovator and biosimilar products.

Raman spectroscopy for in situ, real time monitoring of protein aggregation in lyophilized biotherapeutic products

Quality of biotherapeutic products is of paramount importance for ensuring patient safety. Analytical tools that can facilitate rapid quality assessment of the therapeutic product at the point of care are very much in demand. In this article, we apply chemometrics based analysis of Raman spectra towards quantitative prediction of protein aggregation in lyophilized biotherapeutic products. Two commercially available therapeutic proteins, erythropoietin (EPO) and human growth hormone (HGH), have been used to demonstrate the applicability of the proposed approach. Thermally induced protein aggregation was monitored by size exclusion chromatography as well as Raman spectroscopy with a 785 nm wavelength laser. Partial least square (PLS) regression was used to analyse the Raman spectra and create a model for quantitative determination of aggregate. Satisfactory performance was observed with both EPO and HGH with R² of 0.91 and 0.94, cross-validation correlation coefficient of 0.85 and 0.89, and Root Mean Square Error computed from cross calibration (RMSEcv) of 5.25 and 1.92, respectively. The developed approach can enable rapid and accurate assessment of aggregation in lyophilized samples of biotherapeutic products. The study also demonstrates novel use of Raman spectroscopy for protein quantification through a vial.

Monitoring size and oligomeric-state distribution of therapeutic mAbs by NMR and DLS: Trastuzumab as a case study

Monoclonal antibodies (mAbs) are the modalities of choice for immunotherapy. This class of products are known to exhibit considerable heterogeneity with respect to size, aggregation states, and charge. This makes it challenging for biopharmaceutical manufacturers, in particular biosimilar producers, to maintain consistency in product quality. In order to fingerprint these biotherapeutic products, multiple, high-resolution analytical tools are used to characterize the numerous critical quality attributes. Recently, there has been growing interest in enhancing adaptability of 1D and 2D NMR platforms for characterization of higher order structure with emphasis on 1D ¹H, 2D ¹H-¹⁵N and ¹H-¹³C NMR experiments at natural abundance. In this communication, we report the applicability of 2D-DOSY NMR for quantification of colloidal diffusivities, namely diffusion coefficient (and associated hydrodynamic radius) for monomeric IgG1 mAb formulations at physiological conditions. Similarity assessment has been performed for trastuzumab originator (multiple batches) and marketed biosimilars to showcase the applicability of this approach. While dynamic light scattering measurements are known to be sensitive to presence of larger particles with a concentration dependence for estimation of colloidal diffusivities, size estimated by NMR experiments was found to be more in agreement with the computational hydrodynamic size estimations derived from the published crystal structures of intact mAb at formulation concentration.

Development challenges of high concentration monoclonal antibody formulations

High concentration monoclonal antibody drug products represent a special segment of biopharmaceuticals. In contrast to other monoclonal antibody products, high concentration monoclonal antibodies are injected subcutaneously helping increase patient compliance and reduce the number of hospital patient visits. It is important to note that a high protein concentration (≥50 mg/mL) poses a challenge from a product development perspective. Colloidal properties, physical and chemical protein stability should be considered during formulation, primary packaging and manufacturing process development as well as optimization of other dosage form-related parameters. The aim of such development work is to obtain a drug product capable of maintaining appropriate protein structure throughout its shelf-life and ensure proper and accurate dosage upon administration.

Electron microscopy-based semi-automated characterization of aggregation in monoclonal antibody products

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Size-based quantification of small heterogeneous proteins using electron microscopy.

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Electron microscopy as an orthogonal tool for characterizing protein aggregates.

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Quick assessment of small heterogeneous proteins via softEM, a GUI-based algorithm.

Aggregation is a critical parameter for protein-based therapeutics, due to its impact on the immunogenicity of the product. The traditional approach towards characterization of such products is to use a collection of orthogonal tools. However, the fact that none of these tools is able to completely classify the distribution and physical characteristics of aggregates, implies that there exists a need for additional analytical methods. We report one such method for characterization of heterogeneous population of proteins using transmission electron microscopy. The method involves semi-automated, size-based clustering of different protein species from micrographs. This method can be utilized for quantitative characterization of heterogeneous populations of antibody/protein aggregates from TEM images of proteins, and may also be applicable towards other instances of protein aggregation.

Melatonin improves mitochondrial biogenesis through the AMPK/PGC1α pathway to attenuate ischemia/reperfusion-induced myocardial damage

Cardiac ischemia/reperfusion injury is associated with reduced mitochondrial turnover and regeneration. There is currently no effective approach to stimulate mitochondrial biogenesis in the reperfused myocardium. In this study, we investigated whether melatonin could increase mitochondrial biogenesis and thus promote mitochondrial homeostasis in cardiomyocytes. Cardiomyocytes were subjected to hypoxia/reoxygenation (H/R) injury with or without melatonin treatment, and various mitochondrial functions were measured. H/R injury repressed mitochondrial biogenesis in cardiomyocytes, whereas melatonin treatment restored mitochondrial biogenesis through the 5’ adenosine monophosphate-activated protein kinase (AMPK)/peroxisome proliferator-activated receptor-gamma coactivator 1 alpha (PGC1α) pathway. Melatonin enhanced mitochondrial metabolism, inhibited mitochondrial oxidative stress, induced mitochondrial fusion and prevented mitochondrial apoptosis in cardiomyocytes subjected to H/R injury. The melatonin-induced improvement in mitochondrial biogenesis was associated with increased cardiomyocyte survival during H/R injury. On the other hand, silencing of PGC1α attenuated the protective effects of melatonin on cardiomyocyte viability, thereby impairing mitochondrial bioenergetics, disrupting the mitochondrial morphology, and activating mitochondrial apoptosis. Thus, H/R injury suppressed mitochondrial biogenesis, while melatonin activated the AMPK/PGC1α pathway and restored mitochondrial biogenesis, ultimately protecting the reperfused heart.

Accelerated Aggregation Studies of Monoclonal Antibodies: Considerations for Storage Stability

Aggregation of mAbs is a crucial concern with respect to their safety and efficacy. Among the various properties of protein aggregates, it is emerging that their size can potentially impact their immunogenicity. Therefore, stability studies of antibody formulations should not only evaluate the rate of monomer loss but also determine the size distribution of the protein aggregates, which in turn depends on the aggregation mechanism. Here, we study the aggregation behavior of different formulations of 2 monoclonal immunoglobulins (IgGs) in the temperature range from 5°C to 50°C over 52 weeks of storage. We show that the aggregation kinetics of both antibodies follow non-Arrhenius behavior and that the aggregation mechanisms change between 40°C and 5°C, leading to different types of aggregates. Specifically, for a given monomer conversion, dimer formation dominates at low temperatures, while larger aggregates are formed at higher temperatures. We further show that the stability ranking of different molecules as well as of different formulations is drastically different at 40°C and 5°C while it correlates better between 30°C and 5°C. Our findings have implications for the level of information provided by accelerated aggregation studies with respect to protein stability under storage conditions.