Characterization of N-Terminal Asparagine Deamidation and Clipping of a Monoclonal Antibody

This study presents a novel degradation pathway of a human immunoglobulin G (IgG) molecule featuring a light chain N-terminal asparagine. We thoroughly characterize this pathway and investigate its charge profiles using cation exchange chromatography (CEX) and capillary isoelectric focusing (cIEF). Beyond the well-documented asparagine deamidation into isoaspartic acid, aspartic acid, and succinimide intermediate, a previously unreported clipping degradation pathway is uncovered. This newly identified clipped N-terminal IgG variant exhibits a delayed elution in CEX, categorized as a "basic variant", while retaining the same main peak isoelectric point (pI) in cIEF. The influence of temperature and pH on N-terminal asparagine stability is assessed across various stressed conditions. A notable correlation between deamidation percentage and clipped products is established, suggesting a potential hydrolytic chemical reaction underlying the clipping process. Furthermore, the impact of N-terminal asparagine modifications on potency is evaluated through ELISA binding assays, revealing minimal effects on binding affinity. Sequence alignment reveals homology to a human IgG with the germline gene from Immunoglobulin Lambda Variable 6-57 (IGLV6-57), which has implications for amyloid light-chain (AL) amyloidosis. This discovery of the N-terminal clipping degradation pathway contributes to our understanding of immunoglobulin light chain misfolding and amyloid fibril deposition under physiological conditions.

Combining Machine Learning and Backgrounded Membrane Imaging: A Case Study in Comparing and Classifying Different Types of Biopharmaceutically Relevant Particles

This study investigates how backgrounded membrane imaging (BMI) can be used in combination with convolutional neural networks (CNNs) in order to quantitatively and qualitatively study subvisible particles in both protein biopharmaceuticals and samples containing synthetic model particles. BMI requires low sample volumes and avoids many technical complications associated with imaging particles in solution, e.g., air bubble interference, low refractive index contrast between solution and particles of interest, etc. Hence, BMI is an attractive technique for characterizing particles at various stages of drug product development. However, to date, the morphological information encoded in brightfield BMI images has scarcely been utilized. Here we show that CNN based methods can be useful in extracting morphological information from (label-free) brightfield BMI particle images. Images of particles from biopharmaceutical products and from laboratory prepared samples were analyzed with two types of CNN based approaches: traditional supervised classifiers and a recently proposed fingerprinting analysis method. We demonstrate that the CNN based methods are able to efficiently leverage BMI data to distinguish between particles comprised of different proteins, various fatty acids (representing polysorbate degradation related particles), and protein surrogates (NIST ETFE reference material) only based on BMI images. The utility of using the fingerprinting method for comparing morphological differences and similarities of particles formed in distinct drug products and/or laboratory prepared samples is further demonstrated and discussed through three case studies.

Strategies to Reduce Reconstitution Time of Lyophilized Biotherapeutics

Lyophilized biotherapeutics with high protein concentration may have long reconstitution times, which pose an inconvenience to the end user. This report describes 2 approaches that lead to reduction of reconstitution time: (1) incorporation of tert-butyl alcohol (TBA) in the prelyophilization formulation and (2) decreased headspace pressure in the final lyophilized vial. Cakes made from prelyophilization formulations containing a range of TBA concentrations were physically characterized. The stability of antibodies with TBA in the liquid and lyophilized states was evaluated under stress conditions. Reconstitution time was minimized (>50% reduction) at a TBA concentration of 5% w/v. Reduced headspace pressure in the lyophilized vial demonstrated greater than 50% reduction in reconstitution time at headspace pressures of less than 50 Torr.

Excipients for Room Temperature Stable Freeze-Dried Monoclonal Antibody Formulations

Sucrose is a common cryoprotectant and lyoprotectant to stabilize labile biopharmaceuticals during freeze-drying and storage. Sucrose-based formulations require low primary drying temperatures to avoid collapse and monoclonal antibody (mAb) containing products need to be stored refrigerated. The objective of this study is to investigate different excipients enabling storage at room temperature and aggressive, shorter lyophilization cycles. We studied combinations of 2-hydroxypropyl-beta-cyclodextrin (CD), recombinant human albumin, polyvinylpyrroldione (PVP), dextran 40 kDa (Dex), and sucrose (Suc) using 2 mAbs. Samples were characterized for collapse temperature (Tc), glass transition temperature of the liquid (Tg') and freeze-dried formulation (Tg), cake appearance, residual moisture, and reconstitution time. Freeze-dried formulations were stored at 5°C, 25°C, and 40°C for up to 9 months and mAb stability was analyzed for color, turbidity, visible and sub-visible particles, and monomer content. Formulations with CD/Suc or CD/PVP/Suc were superior to pure Suc formulations for long-term storage at 40°C. When using aggressive freeze-drying cycles, these formulations were characterized by pharmaceutically elegant cakes, short reconstitution times, higher Tg', Tc, and Tg. We conclude that the addition of CD allows for shorter freeze-drying cycles with improved cake appearance and enables storage at room temperature, which might reduce costs of goods substantially.

Suck-Back Impact on Fluid Behavior at Filling Needle Tip

Needle clogging induces several issues during the filling step of injectable drugs, which makes essential to avoiding it to ensure a favorable outcome for the process. The suck-back function, present in peristaltic pumps, is often used empirically to that end. This study aims at describing and understanding the fluid behavior after suck-back application, which provides some quantitative specifications to prevent needle clogging.

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.

Fcγ Receptor Activation by Human Monoclonal Antibody Aggregates

Protein aggregates are a potential risk factor for immunogenicity. The measurement, characterization, and control of protein aggregates in drug products are indispensable for the development of biopharmaceuticals, including therapeutic mAbs. In this study, Fcγ receptor (FcγR)-expressing reporter cell lines were used to analyze the FcγR-activation properties of mAb aggregates. Comparison of aggregates of mAbs harboring different IgG subclasses revealed that the FcγR-activation profiles of the mAb aggregates were dependent on IgG subclass. In addition, aggregates of Fc-engineered mAb with enhanced FcγR-activation properties exhibited stronger activation of FcγRs than was observed in the wild-type aggregates, whereas aggregates of Fc-engineered mAb with decreased FcγR-activation properties showed reduced activation. These results suggest that FcγR activation by mAb aggregates depends greatly on the Fc functions of the native (nonaggregated) mAbs. We also showed that aggregates of mAbs smaller than 1 μm in size have the potential to directly activate FcγRs. Unintended immune cell activation can be induced on account of FcγR activation by mAb aggregates and such FcγR activation may contribute to immunogenicity, and therefore, analysis of the FcγR-activation properties of mAb aggregates using FcγR-expressing reporter cell lines is a promising approach for the characterization of mAb aggregates.

Standardization of the Reconstitution Procedure of Protein Lyophilizates as a Key Parameter to Control Product Stability

Lyophilization of protein formulations is an essential tool for stabilization and is becoming increasingly important for pharmaceutical development. Reconstitution of the lyophilized cakes is crucial to obtain an applicable product. Nowadays, manual reconstitution by patients or medical staff is the common method defined in instructions for marketed lyophilized drug products. Even though this step is influencing the quality of the final solution, it can represent a challenge to develop a standardized manual protocol and the performance is highly dependent on human factors. This study summarizes the implementation and performance of controlled reconstitution studies for protein lyophilizates applying a mechanical reconstitution device. Using automated and standardized protocols, reconstitution time of a bispecific antibody lyophilizate could be reduced effectively from 25 to below 5 min compared to the predeveloped manual protocol. It was shown that the reconstitution protocol is influencing the stability of sensitive proteins. Monomer content as well as formation of subvisible particles differed considerably between the tested protocols emphasizing the relevance of standardized procedures.

What Makes Polysorbate Functional? Impact of Polysorbate 80 Grade and Quality on IgG Stability During Mechanical Stress

Polysorbate 80 (PS80) is a commonly used surfactant in therapeutic protein formulations to mitigate adsorption and interface-induced protein aggregation. Several PS80 grades and qualities are available on the market for parenteral application. The role of PS80 grade on protein stability remains debatable, and the impact of (partially) degraded PS on protein aggregation is not yet well understood. In our study, a monoclonal antibody (IgG) was subjected to 3 different mechanical stress conditions in the presence of multicompendial (MC) and Chinese pharmacopeia (ChP) grade PS80. Furthermore, IgG formulations were spiked with (partly) hydrolyzed PS80 to investigate the effect of PS80 degradants on protein stability. PS80 functionality was assessed by measuring the extent of protein aggregation and particle formation induced during mechanical stress by using size-exclusion chromatography, dynamic light scattering, backgrounded membrane imaging, and flow imaging microscopy. No distinguishable differences in PS80 functionality between MC and ChP grade were observed in the 3 stress tests. However, with increasing degree of PS80 hydrolysis, higher counts of subvisible particles were measured after stress. Furthermore, higher levels of PS80 degradants at a constant PS80 concentration may destabilize the IgG. In conclusion, MC and ChP grade PS80 are equally protective, but PS80 degradants compromise IgG stability.

Development of a Pertactin-Coated Beads Approach for Screening of Functional Monoclonal Antibodies

Vaccine manufacturers have recently focused on the development of in vitro potency assays to promote 3R's strategy to replace animal testing. To be able to develop an in vitro potency assay, the immunological characteristics of the monoclonal antibodies used in the assay should be well understood as these antibodies likely reflect the biological activity of a vaccine product. The PRN antigen is one of the immunogenic antigens included in many commercialized acellular pertussis vaccines. Development of an in vitro potency assay for PRN is challenging as the biological properties of PRN are not well understood. In addition, binding of Bordetella pertussis to human cells occurs through multiple bacterial molecules, which makes it very challenging to assess if antibodies contribute to prevention of bacterial adhesion. To overcome these challenges, the functionality of several in-house anti-PRN mAbs has been investigated through a novel approach using PRN-coated beads. We were able to consistently quantify the inhibition of PRN-mediated adhesion for each anti-PRN mAb. Application of the protein-coated beads model has not only enabled screening of functional anti-PRN mAbs but can also be expanded for screening of antibodies against other bacterial or viral antigens.

Near-Infrared Spectroscopy to Determine Residual Moisture in Freeze-Dried Products: Model Generation by Statistical Design of Experiments

Moisture content (MC) is a critical quality attribute of lyophilized biopharmaceuticals and can be determined by near-infrared (NIR) spectroscopy as nondestructive alternative to Karl-Fischer titration. In this study, we create NIR models to determine MC in mAb lyophilisates by use of statistical design of experiments (DoE) and multivariate data analysis. We varied the composition of the formulation as well as lyophilization parameters covering a large range of representative conditions, which is commonly referred to as "robustness testing" according to quality-by-design concepts. We applied principles of chemometrics with partial least squares and principal component analysis. The NIR model excluded samples with complete collapse and MC > 6%. The 2 main components in the principal component analysis were MC (91%) and protein:sugar ratio (6%). The third component amounted to only 3% and remained unspecified but may include variations in process parameters and cake structure. In contrast to traditional approaches for NIR model creation, the DoE-based model can be used to monitor MC during drug product development work including scale-up, and transfer without the need to update the NIR model if protein:sugar ratio and MC stays within the tested limits and cake structure remains macroscopically intact. The use of the DoE approach and multivariate data analysis ensures product consistency and improves understanding of the manufacturing process.

Shifting Paradigms Revisited: Biotechnology and the Pharmaceutical Sciences

In 2003, Crommelin et al. published an article titled: "Shifting paradigms: biopharmaceuticals versus low molecular weight drugs" (https://doi.org/10.1016/S0378-5173(03)00376-4). In the present commentary, 16 years later, we discuss pharmaceutically relevant aspects of the evolution of biologics since then. First, we discuss the increasing repertoire of biologics, in particular, the rapidly growing monoclonal antibody family and the advent of advanced therapy medicinal products. Next, we discuss trends in formulation and characterization as well as summarize our current insights into immunogenicity of biologics. We spend a separate section on new product(ion) paradigms for biologics, such as cell-free production systems, production of advanced therapy medicinal products, and downscaled production approaches. Furthermore, we share our views on issues related to reaching the patient, including routes and techniques of administration, alternative development models for affordable biologics, biosimilars, and handling of biologics. In the concluding section, we outline outstanding issues and make some suggestions for resolving those.

Considerations for the Design of Antibody-Based Therapeutics

Antibody-based proteins have become an important class of biologic therapeutics, due in large part to the stability, specificity, and adaptability of the antibody framework. Indeed, antibodies not only have the inherent ability to bind both antigens and endogenous immune receptors but also have proven extremely amenable to protein engineering. Thus, several derivatives of the monoclonal antibody format, including bispecific antibodies, antibody-drug conjugates, and antibody fragments, have demonstrated efficacy for treating human disease, particularly in the fields of immunology and oncology. Reviewed here are considerations for the design of antibody-based therapeutics, including immunological context, therapeutic mechanisms, and engineering strategies. First, characteristics of antibodies are introduced, with emphasis on structural domains, functionally important receptors, isotypic and allotypic differences, and modifications such as glycosylation. Then, aspects of therapeutic antibody design are discussed, including identification of antigen-specific variable regions, choice of expression system, use of multispecific formats, and design of antibody derivatives based on fragmentation, oligomerization, or conjugation to other functional moieties. Finally, strategies to enhance antibody function through protein engineering are reviewed while highlighting the impact of fundamental biophysical properties on protein developability.

Monoclonal Antibody Dimers Induced by Low pH, Heat, or Light Exposure Are Not Immunogenic Upon Subcutaneous Administration in a Mouse Model

The presence of protein aggregates is commonly believed to be an important risk factor for immunogenicity of therapeutic proteins. Among all types of aggregates, dimers are relatively abundant in most commercialized monoclonal antibody (mAb) products. The aim of this study was to investigate the immunogenicity of artificially created mAb dimers relative to that of unstressed and stressed mAb monomers. A monoclonal murine IgG1 (mIgG1) antibody was exposed to low pH, elevated temperature, or UV irradiation to induce dimerization. Dimers and monomers were purified via size-exclusion chromatography. Physicochemical analysis revealed that upon all stress conditions, new deamidation or oxidation or both of amino acids occurred. Nevertheless, the secondary and tertiary structures of all obtained dimers were similar to those of unstressed mIgG1. Isolated dimers were administered subcutaneously in Balb/c mice, and development of antidrug antibodies and accumulation of follicular T helper cells in draining lymph nodes and spleens were determined. None of the tested dimers or stressed monomers were found to be more immunogenic than the unstressed control in our mouse model. In conclusion, both dimers and monomers generated by using 3 different stress factors have a low immunogenicity similar to that of the unstressed monomers.

Variance Between Different Light Obscuration and Flow Imaging Microscopy Instruments and the Impact of Instrument Calibration

Subvisible particles (SVPs) are an obligatory critical quality attribute of the product, and yet, they are found in all biopharmaceutical products intended for infusion or injection. Light obscuration (LO) is the primary pharmacopeial method used to quantify SVPs. However, the method may not be equally sensitive toward all particles that can possibly occur. Calibration of LO instruments is usually performed using polystyrene beads suspended in water. In this study, the dependence of the sizing accuracy of LO analysis was evaluated by using a calibration suspension of lower refractive index beads made of silica suspended in sucrose solution. It was demonstrated that the sizing accuracy was strongly dependent on the reference material's properties used for calibration. It was also demonstrated that flow imaging microscopy suffered from the same artifact, albeit to a smaller extent. We further tested different LO sensors and instruments. Interestingly, our results show that the sizing accuracy varied from instrument to instrument, strongly depending on the properties of the sensor. To summarize, sizing and counting accuracies were dependent on the material used for calibration and its optical properties as well as the calibration curve, the sensor, and the instrument supplier. Closer match of optical properties between calibration system and test system seems to improve the sensitivity of the measurement. The results of this study raise the following major practical implications: (1) LO and flow imaging microscopy are not truly orthogonal analytical methods, (2) while matching optimal properties of material used for calibration and test items increased sensitivity, this is of poor practical applicability given that analytes contain multiple particles, and (3) setting product-specific limits for SVPs require special considerations with regard to the data sets used.

Submicron Size Particles of a Murine Monoclonal Antibody Are More Immunogenic Than Soluble Oligomers or Micron Size Particles Upon Subcutaneous Administration in Mice

Protein aggregates are one of the several risk factors for undesired immunogenicity of biopharmaceuticals. However, it remains unclear which features determine whether aggregates will trigger an unwanted immune response. The aim of this study was to determine the effect of aggregates' size on their relative immunogenicity. A monoclonal murine IgG1 was stressed by exposure to low pH and elevated temperature followed by stirring to obtain aggregates widely differing in size. Aggregate fractions enriched in soluble oligomers, submicron size particles and micron size particles were isolated via centrifugation or size-exclusion chromatography and characterized physicochemically. The secondary and tertiary structures of aggregates were altered in a similar way for all the fractions, while no substantial chemical degradation was observed. Development of anti-drug antibodies was measured after subcutaneous administration of each enriched fraction to BALB/c mice. Among all tested fractions, the most immunogenic was the one highly enriched in submicron size particles (∼100-1000 nm). Fractions composed of micron size (>1-100 μm) particles or soluble oligomers (<100 nm) were not immunogenic under the dosing regimen studied in this work. These results show that aggregate size is an important factor for protein immunogenicity.