A comparison of biophysical characterization techniques in predicting monoclonal antibody stability

Extrapolating differential scanning calorimetry data for monoclonal antibodies to low temperatures

For irreversible denaturation transitions such as those exhibited by monoclonal antibodies, differential scanning calorimetry provides the denaturation temperature, Tm, the rate of denaturation at Tm, and the activation energy at Tm. These three quantities are essential but not sufficient for an accurate extrapolation of the rate of denaturation to temperatures of 25 °C and below. We have observed that the activation energy is not constant but temperature dependent due to the existence of an activation heat capacity, Cp,a. It is shown in this paper that a model that incorporates Cp,a is able to account for previous observations like, for example, that increasing the Tm does not always improve the stability at low temperatures; that some antibodies exhibit lower stabilities at 5 °C than at 25 °C; or that low temperature stabilities do not follow the rank order derived from Tm values. Most importantly, the activation heat capacity model is able to reproduce time dependent stabilities measured by size exclusion chromatography at low temperatures.

Stability of Protein Pharmaceuticals: Recent Advances

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

Effect of surfactants on lactate dehydrogenase aqueous solutions: A comparative study of poloxamer 188, polysorbate 20 and 80

The effect of three commonly used surfactants, poloxamer 188 (P188), polysorbate 20 and 80 (PS20 and PS80), on the stability of a model protein, lactate dehydrogenase (LDH), was compared in aqueous solutions. In the absence of a surfactant, protein solution revealed a gradual decrease in surface tension as a function of time. The addition of surfactant resulted in a rapid decrease in the surface tension. This suggested that the surface behavior was dictated by the surfactant. PS20 and PS80 were more effective than P188 in preventing LDH adsorption on the solution surface. The advantage of polysorbates over P188 was also evident from the higher LDH tetramer recovery after shaking (room temperature, 30 h), especially when the surfactants were used at concentrations ≤ 0.01% w/v. However, PS20 and PS80 accelerated protein unfolding during quiescent storage at 40 °C. Based on circular dichroism results, polysorbates perturbed the tertiary structure of LDH but not the secondary structure, while P188 did not impact the protein structure and stability. Polysorbates were more effective in stabilizing LDH against mechanical stress (shaking), but their adverse effects on protein conformational stability need to be carefully evaluated.

Designing Robust Monoclonal Antibody Drug Products: Pitfalls of Simplistic Approaches for Stability Prediction

Thermal stability attributes including unfolding onset (Tonset) and mid-point (Tm) are often utilized for efficient development of monoclonal antibody (mAb) products during lead selection and formulation screening workflows. An assumption of direct correlation between thermal and kinetic physical stability underpins this basic approach. While literature reports have substantiated this general approach under specific conditions, clear exceptions have been highlighted alongside. Herein, a set of mAbs formulated under diverse solution conditions to generate a broad array of thermal and kinetic stability profiles were systematically analyzed. Sequence modifications in the Fc region were purposefully engineered to generate a set of low-melting mAbs. A diverse set of excipients were subsequently utilized and shown to modulate the Tm over a wide range. While a general correlation between high Tm and low aggregation rate was observed under accelerated conditions, the predictive utility of Tm under relevant product storage conditions was inadequate at best. Critically, Tm data did not correlate with long-term aggregation rates under refrigerated or room temperature conditions. Even under accelerated conditions, Tm appeared to be a poor predictor of aggregation once it exceeded the solution storage temperature (40°C) by ∼15°C, similar to conditions routinely encountered in the development of canonical mAbs (Tm > 60°C). Pitfalls of simplistic correlative approaches are discussed in the context of practical biologics product development.

Taurine, a Naturally Occurring Amino Acid, as a Physical Stability Enhancer of Different Monoclonal Antibodies

Degradation of therapeutic monoclonal antibodies (mAbs) is a major concern as it affects efficacy, shelf-life, and safety of the product. Taurine, a naturally occurring amino acid, is investigated in this study as a potential mAb stabilizer with an extensive analytical characterization to monitor product degradation. Forced degradation of trastuzumab biosimilar (mAb1)-containing samples by thermal stress for 30 min resulted in high-molecular-weight species by more than 65% in sample without taurine compared to the sample with taurine. Samples containing mAb1 without taurine also resulted in higher Z-average diameter, altered protein structure, higher hydrophobicity, and lower melting temperature compared to samples with taurine. The stabilizing effect of taurine was retained at different mAb and taurine concentrations, time, temperatures, and buffers, and at the presence of polysorbate 80 (PS80). Even the lowest taurine concentration (10 mM) considered in this study, which is in the range of taurine levels in amino acid injections, resulted in enhanced mAb stability. Taurine-containing samples resulted in 90% less hemolysis than samples containing PS80. Additionally, mAb in the presence of taurine showed enhanced stability upon subjecting to stress with light of 365 nm wavelength, combination of light and H2O2, and combination of Fe2+ and H2O2, as samples containing mAb without taurine resulted in increased degradation products by more than 50% compared to samples with taurine upon subjecting to these stresses for 60 min. In conclusion, the presence of taurine enhanced physical stability of mAb by preventing aggregate formation, and the industry can consider it as a new mAb stabilizer.

Prolonging the stability of cetuximab (Erbitux®) and panitumumab (Vectibix®): An orthogonal assessment of physicochemical, biological and microbiological properties of original opened glass vials and diluted saline preparations

The two anti-epidermal growth factor receptor monoclonal antibodies (mAbs) cetuximab and panitumumab are the pillars for the treatment of EGFR-positive, KRAS wild-type metastatic colorectal cancers. However, stability data of these mAbs are generally missing or incomplete. Here, we report for the first time an orthogonal analysis of the stability of cetuximab (Erbitux®) and panitumumab (Vectibix®), either undiluted vial leftovers or saline dilutions in polyolefin/polyamide infusion bags. All samples were stored at 2-8 °C protected from light, according to their summary of product characteristics (SmPCs). Alternatively, opened vials and preparations were maintained at 25 °C for 15 h, and then stored again at 2-8 °C protected from light to mimic a temporary interruption of the cold chain. Vial leftovers proved stable up to 180 days when stored according to their SmPCs, while compounded preparations in infusion bags maintained their physiochemical, biological and microbiological stability up to 30 days. Additionally, no changes were detected up to 30 days for the same samples undergoing a thermal excursion. Our results provide additional rationale to the SmPCs, crucial especially in the case of reassignment and pre-preparation of bags. This information will allow hospitals to achieve significant cost savings, and better organization of the entire therapeutic process.

Production of Antibodies to Peptide Targets Using Hybridoma Technology

Hybridoma technology is a well-established and indispensable tool for generating high-quality monoclonal antibodies and has become one of the most common methods for monoclonal antibody production. In this process, antibody-producing B cells are isolated from mice following immunization of mice with a specific immunogen and fused with an immortal myeloma cell line to form antibody-producing hybridoma cell lines. Hybridoma-derived monoclonal antibodies not only serve as powerful research and diagnostic reagents but have also emerged as the most rapidly expanding class of therapeutic biologicals. In spite of the development of new high-throughput monoclonal antibody generation technologies, hybridoma technology still is applied for antibody production due to its ability to preserve innate functions of immune cells and to preserve natural cognate antibody paring information. In this chapter, an overview of hybridoma technology and the laboratory procedures used for hybridoma production and antibody screening of peptide-specific antibodies are presented.

Interfacial Pressure and Viscoelasticity of Antibodies and Their Correlation to Long-Term Stability in Formulation

Monoclonal antibodies (mAbs) form viscoelastic gel-like layers at the air-water interface due to their amphiphilic nature, and this same protein characteristic can lead to undesired aggregation of proteins in therapeutic formulations. We hypothesize that the interfacial viscoelasticity and surface pressure of mAbs at the air-water interface will correlate with their long-term stability. To test this hypothesis, the interfacial viscoelastic rheology and surface pressure of five different antibodies with varying visible particle counts from a three-year stability study were measured. We find that both the surface pressures and interfacial elastic moduli correlate well with the long-time mAb solution stability within a class of mAbs with the interfacial elastic moduli being particularly sensitive to discriminate between stable and unstable mAbs across a range of formulations. Furthermore, X-ray reflectivity was used to gain insight into the interfacial structure of mAbs at the air-water interface, providing a possible molecular mechanism to explain the relationship between interfacial elastic moduli and the long-term stability.

Site-Specific Structural Changes in Long-Term-Stressed Monoclonal Antibody Revealed with DEPC Covalent-Labeling and Quantitative Mass Spectrometry

Studies of structural changes in mAbs under forced stress and storage conditions are essential for the recognition of degradation hotspots, which can be further remodeled to improve the stability of the respective protein. Herein, we used diethyl pyrocarbonate (DEPC)-based covalent labeling mass spectrometry (CL-MS) to assess structural changes in a model mAb (SILuMAb). Structural changes in the heat-stressed mAb samples were confirmed at specific amino acid positions from the DEPC label mass seen in the fragment ion mass spectrum. The degree of structural change was also quantified by increased or decreased DEPC labeling at specific sites; an increase or decrease indicated an unfolded or aggregated state of the mAb, respectively. Strikingly, for heat-stressed SILuMAb samples, an aggregation-prone area was identified in the CDR region. In the case of longterm stress, the structural consequences for SILuMAb samples stored for up to two years at 2-8 °C were studied with SEC-UV and DEPC-based CL-MS. While SEC-UV analysis only indicated fragmentation of SILuMAb, DEPC-based CL-MS analysis further pinpointed the finding to structural disturbances of disulfide bonds at specific cysteines. This emphasized the utility of DEPC CL-MS for studying disulfide rearrangement. Taken together, our data suggests that DEPC CL-MS can complement more technically challenging methods in the evaluation of the structural stability of mAbs.

COVID-19 impedimetric biosensor based on polypyrrole nanotubes, nickel hydroxide and VHH antibody fragment: specific, sensitive, and rapid viral detection in saliva samples

SARS-CoV-2 rapid spread required urgent, accurate, and prompt diagnosis to control the virus dissemination and pandemic management. Several sensors were developed using different biorecognition elements to obtain high specificity and sensitivity. However, the task to achieve these parameters in combination with fast detection, simplicity, and portability to identify the biorecognition element even in low concentration remains a challenge. Therefore, we developed an electrochemical biosensor based on polypyrrole nanotubes coupled via Ni(OH)₂ ligation to an engineered antigen-binding fragment of heavy chain-only antibodies (VHH) termed Sb#15. Herein we report Sb#15-His6 expression, purification, and characterization of its interaction with the receptor-binding domain (RBD) of SARS-CoV-2 in addition to the construction and validation of a biosensor. The recombinant Sb#15 is correctly folded and interacts with the RBD with a dissociation constant (K_D) of 27.1 ± 6.4 nmol/L. The biosensing platform was developed using polypyrrole nanotubes and Ni(OH)₂, which can properly orientate the immobilization of Sb#15-His6 at the electrode surface through His-tag interaction for the sensitive SARS-CoV-2 antigen detection. The quantification limit was determined as 0.01 pg/mL using recombinant RBD, which was expressively lower than commercial monoclonal antibodies. In pre-characterized saliva, both Omicron and Delta SARS-CoV-2 were accurately detected only in positive samples, meeting all the requirements recommended by the World Health Organization for in vitro diagnostics. A low sample volume of saliva is needed to perform the detection, providing results within 15 min without further sample preparations. In summary, a new perspective allying recombinant VHHs with biosensor development and real sample detection was explored, addressing the need for accurate, rapid, and sensitive biosensors.

Lot-to-Lot Variance in Immunoassays-Causes, Consequences, and Solutions

Immunoassays, which have gained popularity in clinical practice and modern biomedical research, play an increasingly important role in quantifying various analytes in biological samples. Despite their high sensitivity and specificity, as well as their ability to analyze multiple samples in a single run, immunoassays are plagued by the problem of lot-to-lot variance (LTLV). LTLV negatively affects assay accuracy, precision, and specificity, leading to considerable uncertainty in reported results. Therefore, maintaining consistency in technical performance over time presents a challenge in reproducing immunoassays. In this article, we share our two-decade-long experience and delve into the reasons for and locations of LTLV, as well as explore methods to mitigate its effects. Our investigation identifies potential contributing factors, including quality fluctuation in critical raw materials and deviations in manufacturing processes. These findings offer valuable insights to developers and researchers working with immunoassays, emphasizing the importance of considering lot-to-lot variance in assay development and application.

Comprehensive physicochemical characterization of a peptide-based medicine: Teduglutide (Revestive®) structural description and stress testing

Teduglutide (Revestive®) is a glucagon-like peptide-2 analogue used for the treatment of short bowel syndrome, a rare life-threatening condition in which the amount of functional gut is too short to enable proper absorption of nutrients and fluids. During handling prior to administration to the patient in hospital, it is possible that peptide-based medicines may be exposed to environmental stress conditions that could affect their quality. It is therefore essential to carry out stress testing studies to evaluate how such medicines respond to these stresses. For this reason, in this paper we present a strategy for a comprehensive analytical characterization of a peptide and a stress testing study in which it was subjected to various stress conditions: heating at 40 °C and 60 °C, light exposure and shaking. Several complementary analytical techniques were used throughout this study: Far UV circular dichroism, intrinsic protein fluorescence spectroscopy, dynamic light scattering, size-exclusion chromatography and intact and peptide mapping reverse-phase chromatography coupled to mass spectrometry. To the best of our knowledge, this is the first study to offer an in-depth description of the chemical structure of teduglutide peptide and its physicochemical characteristics after stress stimuli were applied to the reconstituted medicine Revestive®.

Bioprocess Development and Characterization of a 13C-Labeled Hybrid Bispecific Antibody Produced in Escherichia coli

Monoclonal antibodies (mAbs) are highly efficacious therapeutics; however, due to their large, dynamic nature, structural perturbations and regional modifications are often difficult to study. Moreover, the homodimeric, symmetrical nature of mAbs makes it difficult to elucidate which heavy chain (HC)-light chain (LC) pairs are responsible for any structural changes, stability concerns, and/or site-specific modifications. Isotopic labeling is an attractive means for selectively incorporating atoms with known mass differences to enable identification/monitoring using techniques such as mass spectrometry (MS) and nuclear magnetic resonance (NMR). However, the isotopic incorporation of atoms into proteins is typically incomplete. Here we present a strategy for incorporating ¹³C-labeling of half antibodies using an Escherichia coli fermentation system. Unlike previous attempts to generate isotopically labeled mAbs, we provide an industry-relevant, high cell density process that yielded >99% ¹³C-incorporation using ¹³C-glucose and ¹³C-celtone. The isotopic incorporation was performed on a half antibody designed with knob-into-hole technology to enable assembly with its native (naturally abundant) counterpart to generate a hybrid bispecific (BsAb) molecule. This work is intended to provide a framework for producing full-length antibodies, of which half are isotopically labeled, in order to study the individual HC-LC pairs.

A Review of Protein- and Peptide-Based Chemical Conjugates: Past, Present, and Future

Over the past few decades, the complexity of molecular entities being advanced for therapeutic purposes has continued to evolve. A main propellent fueling innovation is the perpetual mandate within the pharmaceutical industry to meet the needs of novel disease areas and/or delivery challenges. As new mechanisms of action are uncovered, and as our understanding of existing mechanisms grows, the properties that are required and/or leveraged to enable therapeutic development continue to expand. One rapidly evolving area of interest is that of chemically enhanced peptide and protein therapeutics. While a variety of conjugate molecules such as antibody-drug conjugates, peptide/protein-PEG conjugates, and protein conjugate vaccines are already well established, others, such as antibody-oligonucleotide conjugates and peptide/protein conjugates using non-PEG polymers, are newer to clinical development. This review will evaluate the current development landscape of protein-based chemical conjugates with special attention to considerations such as modulation of pharmacokinetics, safety/tolerability, and entry into difficult to access targets, as well as bioavailability. Furthermore, for the purpose of this review, the types of molecules discussed are divided into two categories: (1) therapeutics that are enhanced by protein or peptide bioconjugation, and (2) protein and peptide therapeutics that require chemical modifications. Overall, the breadth of novel peptide- or protein-based therapeutics moving through the pipeline each year supports a path forward for the pursuit of even more complex therapeutic strategies.

An Intercompany Perspective on Practical Experiences of Predicting, Optimizing and Analyzing High Concentration Biologic Therapeutic Formulations

Developing high-dose biologic drugs for subcutaneous injection often requires high-concentration formulations and optimizing viscosity, solubility, and stability while overcoming analytical, manufacturing, and administration challenges. To understand industry approaches for developing high-concentration formulations, the Formulation Workstream of the BioPhorum Development Group, an industry-wide consortium, conducted an inter-company collaborative exercise which included several surveys. This collaboration provided an industry perspective, experience, and insight into the practicalities for developing high-concentration biologics. To understand solubility and viscosity, companies desire predictive tools, but experience indicates that these are not reliable and experimental strategies are best. Similarly, most companies prefer accelerated and stress stability studies to in-silico or biophysical-based prediction methods to assess aggregation. In addition, optimization of primary container-closure and devices are pursued to mitigate challenges associated with high viscosity of the formulation. Formulation strategies including excipient selection and application of studies at low concentration to high-concentration formulations are reported. Finally, analytical approaches to high concentration formulations are presented. The survey suggests that although prediction of viscosity, solubility, and long-term stability is desirable, the outcome can be inconsistent and molecule dependent. Significant experimental studies are required to confirm robust product definition as modeling at low protein concentrations will not necessarily extrapolate to high concentration formulations.

Optimizing and determining the click chemistry mediated Cu-64 radiolabeling and physiochemical characteristics of trastuzumab conjugates

Over the last decade, ⁶⁴Cu-labeling of monoclonal antibody (mAb) via inverse electron demand Diels-Alder click chemistry (IEDDA) have received much attention. Despite the tetrazine-transcyclooctene (Tz-TCO) click chemistry's convenience and efficiency in mAb labeling, there is limited information about the ideal parameters in the development of click chemistry mediated (radio)immunoconjugates. This encourages us to conduct a systematic optimization while concurrently determining the physiochemical characteristics of the model mAb, trastuzumab, and TCO conjugates. To accomplish this, we investigated a few critical parameters, first, we determined the degree of conjugations with varying molar equivalents (eq.) of TCO (3, 5, 10, and 15 eq.). Through analytical techniques like size exclusion chromatography, dynamic light scattering, and zeta potential, qualitative analysis were performed to determine the purity, degree of aggregation and net charge of the conjugates. We found that as the degree of conjugation increased the purity of intact mAb fraction is compromised and net charge of conjugates became less positive. Next, all trastuzumab-PEG₄-TCO conjugates with varying molar ratio and quantity (30, 50, 100, 200, 250 μg) were radiolabeled with ⁶⁴Cu-NOTA-PEG₄-Tz via IEDDA click chemistry and radiochemical yields were determined by radio-thin layer chromatography. The radiochemical yields of trastuzumab conjugates improved with increased amount and molar ratio. Next, we investigated the effect of the radioprotectant ascorbic acid (AA) of varied concentrations (0.25, 0.5, 0.75, 1 mM) on radiochemical yields and subsequent pharmacokinetics. A concentration of 0.25 mM of AA was found to be optimal for click reaction and in vivo biodistribution. Finally, we investigated the indirect influence of bioconjugation buffers on radiochemical yields and biodistribution in NIH3T6.7 tumor models that resulted approximately ∼11 %ID/g tumor uptake.

Development of in silico models to predict viscosity and mouse clearance using a comprehensive analytical data set collected on 83 scaffold-consistent monoclonal antibodies

Biologic drug discovery pipelines are designed to deliver protein therapeutics that have exquisite functional potency and selectivity while also manifesting biophysical characteristics suitable for manufacturing, storage, and convenient administration to patients. The ability to use computational methods to predict biophysical properties from protein sequence, potentially in combination with high throughput assays, could decrease timelines and increase the success rates for therapeutic developability engineering by eliminating lengthy and expensive cycles of recombinant protein production and testing. To support development of high-quality predictive models for antibody developability, we designed a sequence-diverse panel of 83 effector functionless IgG1 antibodies displaying a range of biophysical properties, produced and formulated each protein under standard platform conditions, and collected a comprehensive package of analytical data, including in vitro assays and in vivo mouse pharmacokinetics. We used this robust training data set to build machine learning classifier models that can predict complex protein behavior from these data and features derived from predicted and/or experimental structures. Our models predict with 87% accuracy whether viscosity at 150 mg/mL is above or below a threshold of 15 centipoise (cP) and with 75% accuracy whether the area under the plasma drug concentration-time curve (AUC0-672 h) in normal mouse is above or below a threshold of 3.9 × 106 h x ng/mL.

Blueprint for antibody biologics developability

Large-molecule antibody biologics have revolutionized medicine owing to their superior target specificity, pharmacokinetic and pharmacodynamic properties, safety and toxicity profiles, and amenability to versatile engineering. In this review, we focus on preclinical antibody developability, including its definition, scope, and key activities from hit to lead optimization and selection. This includes generation, computational and in silico approaches, molecular engineering, production, analytical and biophysical characterization, stability and forced degradation studies, and process and formulation assessments. More recently, it is apparent these activities not only affect lead selection and manufacturability, but ultimately correlate with clinical progression and success. Emerging developability workflows and strategies are explored as part of a blueprint for developability success that includes an overview of the four major molecular properties that affect all developability outcomes: 1) conformational, 2) chemical, 3) colloidal, and 4) other interactions. We also examine risk assessment and mitigation strategies that increase the likelihood of success for moving the right candidate into the clinic.

Advancing humanized monoclonal antibody for counteracting fentanyl toxicity towards clinical development

Innovative therapies to complement current treatments are needed to curb the growing incidence of fatal overdoses related to synthetic opioids. Murine and chimeric monoclonal antibodies (mAb) specific for fentanyl and its analogs have demonstrated pre-clinical efficacy in preventing and reversing drug-induced toxicity in rodent models. However, mAb-based therapeutics require extensive engineering as well as in vitro and in vivo characterization to advance to first-in-human clinical trials. Here, novel murine anti-fentanyl mAbs were selected for development based on affinity for fentanyl, and efficacy in counteracting the pharmacological effects of fentanyl in mice. Humanization and evaluation of mutations designed to eliminate predicted post-translational modifications resulted in two humanized mAbs that were effective at preventing fentanyl-induced pharmacological effects in rats. These humanized mAbs showed favorable biophysical properties with respect to aggregation and hydrophobicity by chromatography-based assays, and thermostability by dynamic scanning fluorimetry. These results collectively support that the humanized anti-fentanyl mAbs developed herein warrant further clinical development for treatment of fentanyl toxicity.

Challenges and Strategies for a Thorough Characterization of Antibody Acidic Charge Variants

Heterogeneity of therapeutic Monoclonal antibody (mAb) drugs are due to protein variants generated during the manufacturing process. These protein variants can be critical quality attributes (CQAs) depending on their potential impact on drug safety and/or efficacy. To identify CQAs and ensure the drug product qualities, a thorough characterization is required but challenging due to the complex structure of biotherapeutics. Past characterization studies for basic and acidic variants revealed that full characterizations were limited to the basic charge variants, while the quantitative measurements of acidic variants left gaps. Consequently, the characterization and quantitation of acidic variants are more challenging. A case study of a therapeutic mAb1 accounted for two-thirds of the enriched acidic variants in the initial characterization study. This led to additional investigations, closing the quantification gaps of mAb1 acidic variants. This work demonstrates that a well-designed study with the right choices of analytical methods can play a key role in characterization studies. Thus, the updated strategies for more complete antibody charge variant characterization are recommended.

Developability Assessments of Monoclonal Antibody Candidates to Minimize Aggregation During Large-Scale Ultrafiltration and Diafiltration (UF-DF) Processing

Therapeutic proteins are subjected to a variety of stresses during manufacturing, storage or administration, that often lead to undesired protein aggregation and particle formation. Ultrafiltration-diafiltration (UF-DF) processing of monoclonal antibodies (mAbs) is one such manufacturing step that has been shown to result in such physical degradation. In this work, we explore the use of different analytical techniques and lab-scale setups as methodologies to predict and rank-order the aggregation potential of four different mAbs during large-scale UF-DF processing. In the first part of the study, a suite of biophysical techniques was applied to assess differences in their inherent bulk protein properties including conformational and colloidal stability in a PBS buffer. Additionally, the inherent interfacial properties of these mAbs in PBS were measured using a Langmuir trough technique. In the next part of the study, several different scale-down lab models were evaluated including a lab bench-scale UF-DF setup, mechanical stress (shaking/stirring) studies in vials, and application of interfacial dilatational stress using a Langmuir trough to assess protein particle formation in different UF-DF processing buffers. Taken together, our results demonstrate the ability of a Langmuir-trough methodology to accurately predict the mAb instability profile observed during large scale UF-DF processing.

NMR Reveals Functionally Relevant Thermally Induced Structural Changes within the Native Ensemble of G-CSF

Structure–function relationships in proteins refer to a trade-off between stability and bioactivity, molded by evolution of the molecule. Identifying which protein amino acid residues jeopardize global or local stability for the benefit of bioactivity would reveal residues pivotal to this structure–function trade-off. Here, we use ¹⁵N–¹H heteronuclear single quantum coherence (HSQC) nuclear magnetic resonance (NMR) spectroscopy to probe the microenvironment and dynamics of residues in granulocyte colony-stimulating factor (G-CSF) through thermal perturbation. From this analysis, we identified four residues (G4, A6, T133, and Q134) that we classed as significant to global stability, given that they all experienced large environmental and dynamic changes and were closely correlated to each other in their NMR characteristics. Additionally, we observe that roughly four structural clusters are subject to localized conformational changes or partial unfolding prior to global unfolding at higher temperature. Combining NMR observables with structure relaxation methods reveals that these structural clusters concentrate around loop AB (binding site III inclusive). This loop has been previously implicated in conformational changes that result in an aggregation prone state of G-CSF. Residues H43, V48, and S63 appear to be pivotal to an opening motion of loop AB, a change that is possibly also important for function. Hence, we present here an approach to profiling residues in order to highlight their potential roles in the two vital characteristics of proteins: stability and bioactivity.

Hydroxylpropyl-β-cyclodextrin as Potential Excipient to Prevent Stress-Induced Aggregation in Liquid Protein Formulations

Due to the growing demand for patient-friendly subcutaneous dosage forms, the ability to increasing protein solubility and stability in formulations to deliver on the required high protein concentrations is crucial. A common approach to ensure protein solubility and stability in high concentration protein formulations is the addition of excipients such as sugars, amino acids, surfactants, approved by the Food and Drug Administration. In a best-case scenario, these excipients fulfil multiple demands simultaneously, such as increasing long-term stability of the formulation, reducing protein adsorption on surfaces/interfaces, and stabilizing the protein against thermal or mechanical stress. 2-Hydroxylpropyl-β-cyclodextrin (derivative of β-cyclodextrin) holds this potential, but has not yet been sufficiently investigated for use in protein formulations. Within this work, we have systematically investigated the relevant molecular interactions to identify the potential of Kleptose^®HPB (2-hydroxylpropyl-β-cyclodextrin from Roquette Freres, Lestrem, France) as “multirole” excipient within liquid protein formulations. Based on our results three factors determine the influence of Kleptose^®HPB on protein formulation stability: (1) concentration of Kleptose^®HPB, (2) protein type and protein concentration, and (3) quality of the protein formulation. Our results not only contribute to the understanding of the relevant interactions but also enable the target-oriented use of Kleptose^®HPB within formulation design.

Effect of the ADCC-modulating mutations and the selection of human IgG isotypes on physicochemical properties of Fc

Monoclonal antibodies, particularly IgGs and Ig-based molecules, are a well-established and growing class of biotherapeutic drugs. In order to improve efficacy, potency and pharmacokinetics of these therapeutic drugs, pharmaceutical industries have investigated significantly in engineering fragment crystallizable (Fc) domain of these drugs to optimize the interactions of these drugs and Fc gamma receptors (FcγRs) in recent ten years. The biological function of the therapeutics with the antibody-dependent cellular cytotoxicity (ADCC) enhanced double mutation (S239D/I332E) of isotype IgG1, the ADCC reduced double mutation (L234A/L235A) of isotype IgG1, and ADCC reduced isotype IgG4 has been well understood. However, limited information regarding the effect of these mutations or isotype difference on physicochemical properties (PCP), developability, and manufacturability of therapeutics bearing these different Fc regions is available. In this report, we systematically characterize the effects of the mutations and IgG4 isotype on conformation stability, colloidal stability, solubility, and storage stability at accelerated conditions in two buffer systems using six Fc variants. Our results provide a basis for selecting appropriate Fc region during development of IgG or Ig-based therapeutics and predicting effect of the mutations on CMC development process.

Temperature and pH-Dependent Behaviors of mAb Drugs: A Case Study for Trastuzumab

The distortions in the high-order structure of therapeutic monoclonal antibodies (mAbs) under different environmental conditions acutely affect mAb stability, resulting in altered safety, efficacy, and shelf-life profiles. The overall stability of mAbs depends on many factors, and it requires complementary techniques for an in-depth analysis. The stability of mAbs can be characterized by differential centrifugal sedimentation (DCS), differential scanning calorimetry (DSC), differential scanning fluorimetry (DSF), and size exclusion chromatography (SEC) techniques. In this report, temperature-ramped dynamic light scattering (DLS), and circular dichroism (CD) spectroscopy were employed as complementary tools to show how temperature and pH affect the aggregation of a model mAb, trastuzumab, in solution. The results showed that the aggregation onset temperature of trastuzumab defined by DLS was 75 °C, which decreases the amount of β-sheets and causes a slight increase in helix structures. Moreover, the melting temperature of trastuzumab was determined to be between 80–83 °C by temperature-ramped CD spectrophotometry, which is in line with the Tm of trastuzumab’s Fab region tested with DSC. Thus, unfolding and aggregation of trastuzumab start simultaneously at 75 °C, and unfolding triggers the aggregation. The temperature-ramped CD and DLS methods are robust tools to determine the thermal behavior of biosimilars in various solution conditions. Their complementary usage provides solid scientific background for regulatory applications and a better understanding of mAb instability and its relationship with structural changes.

Multiscale pharmacokinetic modeling of systemic exposure of subcutaneously injected biotherapeutics

Subcutaneously injected formulations have been developed for many biological products including monoclonal antibodies (mAbs). A knowledge gap nonetheless remains regarding the absorption and catabolism mechanisms and kinetics of a large molecule at the administration site. A multiscale pharmacokinetic (PK) model was thus developed by coupling multiphysics simulations of subcutaneous (SC) absorption kinetics with whole-body pharmacokinetic (PK) modeling, bridged by consideration of the presystemic clearance by the initial lymph. Our local absorption simulation of SC-injected albumin enabled the estimation of its presystemic clearance and led to the whole-body PK modeling of systemic exposure. The local absorption rate of albumin was found to be influential on the PK profile. Additionally, nineteen mAbs were explored via this multiscale simulation and modeling framework. The computational results suggest that stability propensities of the mAbs are correlated with the presystemic clearance, and electrostatic charges in the complementarity-determining region influence the local absorption rate. Still, this study underscores a critical need to experimentally determine various biophysical characteristics of a large molecule and the biomechanical properties of human skin tissues.

Physicochemical and biological similarity assessment of LBAL, a biosimilar to adalimumab reference product (Humira®)

LBAL was developed as an adalimumab (Humira®) biosimilar using Chinese hamster ovary cell lines. Comparable quality, safety, and efficacy between a biosimilar and its reference product should be ensured for regulatory approval. Here, we present the results of a comprehensive physicochemical and biological characterization between LBAL and Humira®. As physicochemical attributes, primary and higher-order structure, N-glycan profile, and disulfide linkage were investigated. Biological attributes were evaluated by target/receptor binding analysis and in vitro/ex vivo cell-based assays, which are linked to mechanisms of action. As a result, LBAL had the identical amino acid sequence, similar post-translational modifications and N-/C-terminal variants, and comparable primary, secondary, and tertiary structures and disulfide linkage profile. However, some differences in N-glycan profiles were observed. Biological activities, including tumor necrosis factor (TNF) binding, TNF-neutralization, apoptosis, Fc receptor binding, and complement-dependent cytotoxicity, were largely consistent. Despite a slightly lower antibody-dependent cellular cytotoxicity activity in LBAL, this difference was not significant under physiological conditions. As indicated, this extensive analytical characterization and functional comparison assessment showed that LBAL was similar to Humira®, with minor differences of no clinical relevance. Taken together, our comparative assessment of physicochemical and biological attributes demonstrated that LBAL is structurally and functionally very similar to Humira®, supporting the biosimilarity of clinical efficacy and safety.

Reversibility and irreversibility in the temperature denaturation of monoclonal antibodies

There have been numerous studies of the temperature denaturation of monoclonal antibodies (mAbs) using differential scanning calorimetry (DSC). In general, mAbs are characterized by complex temperature denaturation transitions in which the various domains (CH2, CH3, Fab) give rise to different peaks in the heat capacity function. The complexity and overall irreversibility of the temperature denaturation transition is well known and has limited the number of publications with an in-depth analysis of the data. Here we report that the temperature denaturation of the CH2 domain is reversible and only becomes irreversible after denaturation of the Fab domain, which is intrinsically irreversible. For these studies we have used the HIV neutralizing monoclonal antibody 17b. To account for the experimental heat capacity function, a mixed denaturation model that combines multiple reversible and irreversible transitions has been developed. This model accounts well for the DSC data and for the pH dependence of the heat capacity function of 17b and other monoclonal antibodies for which data is available in the literature. It is expected that a more detailed analysis of the stability of monoclonal antibodies will contribute to the development of better approaches to understand and optimize the structural viability of these therapeutic macromolecules.

Pragmatic mAb lead molecule engineering from a developability perspective

As the number of antibody drugs being approved and marketed increases, our knowledge of what makes potential drug candidates a successful product has increased tremendously. One of the critical parameters that have become clear in the field is the importance of mAb "developability." Efforts are being increasingly focused on simultaneously selecting molecules that exhibit both desirable biological potencies and manufacturability attributes. In the current study mutations to improve the developability profile of a problematic antibody that inconsistently precipitates in a batch scale-dependent fashion using a standard platform purification process are described. Initial bioinformatic analysis showed the molecule has no obvious sequence or structural liabilities that might lead it to precipitate. Subsequent analysis of the molecule revealed the presence of two unusual positively charged mutations on the light chain at the interface of VH and VL domains, which were hypothesized to be the primary contributor to molecule precipitation during process development. To investigate this hypothesis, straightforward reversion to the germline of these residues was carried out. The resulting mutants have improved expression titers and recovered stability within a forced precipitation assay, without any change to biological activity. Given the time pressures of drug development in industry, process optimization of the lead molecule was carried out in parallel to the "retrospective" mutagenesis approach. Bespoke process optimization for large-scale manufacturing was successful. However, we propose that such context-dependent sequence liabilities should be included in the arsenal of in silico developability screening early in development; particularly since this specific issue can be efficiently mitigated without the requirement for extensive screening of lead molecule variants.

Machine learning reveals hidden stability code in protein native fluorescence

Conformational stability of a protein is usually obtained by spectroscopically measuring the unfolding melting temperature. However, optical spectra under native conditions are considered to contain too little resolution to probe protein stability. Here, we have built and trained a neural network model to take the temperature-dependence of intrinsic fluorescence emission under native-only conditions as inputs, and then predict the spectra at the unfolding transition and denatured state. Application to a therapeutic antibody fragment demonstrates that thermal transitions obtained from the predicted spectra correlate highly with those measured experimentally. Crucially, this work reveals that the temperature-dependence of native fluorescence spectra contains a high-degree of previously hidden information relating native ensemble features to stability. This could lead to rapid screening of therapeutic protein variants and formulations based on spectroscopic measurements under non-denaturing temperatures only.

Critical reagent generation, characterization, handling and storage workflows: impact on ligand binding assays

The foundation of pharmacokinetics and antidrug antibodies assay robustness relies on the use of high-quality reagents. Over the past decade, there has been increasing interest within the pharmaceutical industry, as well as regulators, on defining best practices and scientific approaches for generation, characterization and handling of critical reagents. In this review, we will discuss current knowledge and practices on critical reagent workflows and state-of-the-art approaches for characterization, generation, stability and storage and how each of these steps can impact ligand-binding assay robustness.

Stability of the Retinoid X Receptor-α Homodimer in the Presence and Absence of Rexinoid and Coactivator Peptide

Differential scanning calorimetry and differential scanning fluorimetry were used to measure the thermal stability of human retinoid X receptor-α ligand binding domain (RXRα LBD) homodimer in the absence or presence of rexinoid and coactivator peptide, GRIP-1. The apo-RXRα LBD homodimer displayed a single thermal unfolding transition with a T_m of 58.7 °C and an unfolding enthalpy (ΔH) of 673 kJ/mol (12.5 J/g), much lower than average value (35 J/g) of small globular proteins. Using a heat capacity change (ΔC_p) of 15 kJ/(mol K) determined by measurements at different pH values, the free energy of unfolding (ΔG) of the native state was 33 kJ/mol at 37 °C. Rexinoid binding to the apo-homodimer increased T_m by 5 to 9 °C and increased the ΔG of the native homodimer by 12 to 20 kJ/mol at 37 °C, consistent with the nanomolar dissociation constant (K_d) of the rexinoids. GRIP-1 binding to holo-homodimers containing rexinoid resulted in additional increases in ΔG of 14 kJ/mol, a value that was the same for all three rexinoids. Binding of rexinoid and GRIP-1 resulted in a combined 50% increase in unfolding enthalpy, consistent with reduced structural fluidity and more compact folding observed in other published structural studies. The complexes of UAB110 and UAB111 are each more stable than the UAB30 complex by 8 kJ/mol due to enhanced hydrophobic interactions in the binding pocket because of their larger end groups. This increase in thermodynamic stability positively correlates with their improved RXR activation potency. Thermodynamic measurements are thus valuable in predicting agonist potency.

Toward a Suite of Coarse-Grained Models for Molecular Simulation of Monoclonal Antibodies and Therapeutic Proteins

A series of coarse-grained models for molecular simulation of proteins are considered, with emphasis on the application of predicting protein-protein self-interactions for monoclonal antibodies (MAbs). As an illustrative example and for quantitative comparison, the models are used to predict osmotic virial coefficients over a broad range of attractive and repulsive self-interactions and solution conditions for a series of MAbs where the second osmotic virial coefficient has been experimentally determined in prior work. The models are compared based on how well they can predict experimental behavior, their computational burdens, and scalability. An intermediate-resolution model is also introduced that can capture specific electrostatic interactions with improved efficiency and similar or improved accuracy when compared to the previously published models. Guidance is included for the selection of coarse-grained models more generally for capturing a balance of electrostatic, steric, and short-ranged nonelectrostatic interactions for proteins from low to high concentrations.

High-Throughput Screening for Colloidal Stability of Peptide Formulations Using Dynamic and Static Light Scattering

Selection of an appropriate formulation to stabilize therapeutic proteins against aggregation is one of the most challenging tasks in early-stage drug product development. The amount of aggregates is more difficult to quantify in the case of peptides due to their small molecular size. Here, we investigated the suitability of diffusion self-interaction parameters (k_D) and osmotic second virial coefficients (B₂₂) for high-throughput (HT) screening of peptide formulations regarding their aggregation risk. These parameters were compared to the effect of thermal stress on colloidal stability. The formulation matrix comprised six buffering systems at two selected pH values, four tonicity agents, and a common preservative. The results revealed that electrostatic interactions are the main driver to control colloidal stability. Preferred formulations consisted of acetate and succinate buffer at pH 4.5 combined with glycerol or mannitol and optional m-cresol. k_D proved to be a suitable surrogate for B₂₂ as an indicator of high colloidal stability in the case of peptides as was previously described for globular proteins and antibodies. Formulation assessment solely based on k_D obtained by HT methods offers important insights into the optimization of colloidal stability during the early development of peptide-based liquid formulations and can be performed with a limited amount of peptide (∼360 mg).

Application of Affinity-Capture Self-Interaction Nanoparticle Spectroscopy in Predicting Protein Stability, Especially for Co-Formulated Antibodies

PURPOSE

From traditional monoclonal antibodies to more and more complex mAb-based formulations, biopharmaceutical faces one challenge after another. To avoid these issues, identification of therapeutic proteins in the initial discovery process that has high stability and low self-interaction would simplify the development of safe and effective antibody therapeutics.

METHOD

Affinity-capture self-interaction nanoparticle spectroscopy (AC-SINS) is a new prediction method capable of identifying mAbs with different self-association propensity. In this study, 10 formulated monoclonal antibody (mAb) therapeutics include different mAb isotypes and co-formulated antibodies were measured by AC-SINS and some biophysical methods to predict protein stability. The prediction results of all 10 mAbs were compared to their stability data (Δ%monomer and Δ%HMWs) at accelerated (25°C and 40°C) and long-term storage conditions (4°C) as measured by size exclusion chromatography.

RESULT

AC-SINS method has a good predictive correlation with each mAbs and co-formulated antibodies. There were no physicochemical, intermolecular, or biological interactions that occurred between the two components of co-formulated antibodies which confirmed by Analytical ultracentrifugation (AUC).

CONCLUSION

Here we discuss the correlation between each method and protein stability, and also use AC-SINS assay to predict the stability of co-formulated antibodies for the first time. This may be an effective way to predict the stability of these complex mAb-based formulations such as co-formulated mAbs.

Stability of antibody drug conjugate formulations evaluated using solid-state hydrogen-deuterium exchange mass spectrometry

Antibody drug conjugates (ADCs) have been at the forefront in cancer therapy due to their target specificity. All the FDA approved ADCs are developed in lyophilized form to minimize instability associated with the linker that connects the cytotoxic drug and the antibody during shipping and storage. We present here solid-state hydrogen-deuterium exchange with mass spectrometric analysis (ssHDX-MS) as a tool to analyze protein structure and matrix interactions for formulations of an ADC with and without commonly used excipients. We compared results of the ssHDX-MS with accelerated stability results using size-exclusion chromatography and determined that the former technique was able to successfully identify the destabilizing effects of mannitol and polysorbate 80. In comparison, Fourier-transform infrared spectroscopy results were inconclusive. The agreement between ssHDX-MS and stressed stability studies supports the potential of ssHDX-MS as a method of predicting relative stability of different formulations.

Predicting Antibody Developability Profiles Through Early Stage Discovery Screening

Monoclonal antibodies play an increasingly important role for the development of new drugs across multiple therapy areas. The term 'developability' encompasses the feasibility of molecules to successfully progress from discovery to development via evaluation of their physicochemical properties. These properties include the tendency for self-interaction and aggregation, thermal stability, colloidal stability, and optimization of their properties through sequence engineering. Selection of the best antibody molecule based on biological function, efficacy, safety, and developability allows for a streamlined and successful CMC phase. An efficient and practical high-throughput developability workflow (100 s-1,000 s of molecules) implemented during early antibody generation and screening is crucial to select the best lead candidates. This involves careful assessment of critical developability parameters, combined with binding affinity and biological properties evaluation using small amounts of purified material (<1 mg), as well as an efficient data management and database system. Herein, a panel of 152 various human or humanized monoclonal antibodies was analyzed in biophysical property assays. Correlations between assays for different sets of properties were established. We demonstrated in two case studies that physicochemical properties and key assay endpoints correlate with key downstream process parameters. The workflow allows the elimination of antibodies with suboptimal properties and a rank ordering of molecules for further evaluation early in the candidate selection process. This enables any further engineering for problematic sequence attributes without affecting program timelines.

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

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

Washing with alkaline solutions in protein A purification improves physicochemical properties of monoclonal antibodies

Protein A affinity chromatography has been widely used for both laboratory scale purification and commercial manufacturing of monoclonal antibodies and Fc-fusion proteins. Protein A purification is specific and efficient. However, there still remain several issues to be addressed, such as incomplete clearance of impurities including host cell proteins, DNA, aggregates, etc. In addition, the effects of wash buffers in protein A purification on the physicochemical characteristics of antibodies have yet to be fully understood. Here we found a new purification protocol for monoclonal antibodies that can improve physicochemical properties of monoclonal antibodies simply by inserting an additional wash step with a basic buffer after the capture step to the conventional protein A purification. The effects of the alkaline wash on monoclonal antibodies were investigated in terms of physicochemical characteristics, yields, and impurity clearance. The simple insertion of an alkaline wash step resulted in protection of antibodies from irreversible aggregation, reduction in free thiols and impurities, an improvement in colloidal and storage stability, and enhanced yields. This new procedure is widely applicable to protein A affinity chromatography of monoclonal antibodies.

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.

Room Temperature Intrinsic Emission Ratio of BSA Correlates With Percent Aggregates During Long-Term Storage

Successful formulation development hinges on the ability to screen and identify excipients that stabilize drug products during long-term storage. Biophysical and accelerated stability studies are used to screen for excipients that stabilize protein drug products. However, these studies are not always predictive of aggregation during long-term storage. In this study, we used multivariate experimentation to compare the effectiveness of intrinsic fluorescence and size exclusion chromatography accelerated stability parameters to predict excipients that stabilized bovine serum albumin (BSA) against aggregation on long-term storage at 4 °C. Emission intensity ratio (IR_330/350) data was more sensitive than emission maxima (λ_max) or intensity measurements in identifying significant factors and interactions. We observed the expected inverse correlation between the mid-points of fluorescence thermal transitions (T_ms) and insoluble aggregates at 4 and 40 °C. However, there were positive correlations between T_ms and % aggregates at 4 °C, indicating that if T_m was used as a predictive tool, it would select formulations that promoted soluble aggregates on long-term storage. Ambient temperature IR_330/350 measurements identified excipients that reduced BSA soluble aggregates on long-term storage. The results show ambient temperature emission ratio measurements can be useful for protein formulation development.

Developability assessment for monoclonal antibody drug candidates: a case study

Various screening approaches are used by industry to evaluate development risks associated with discovery candidates. This process has become more complicated with biological therapeutics, a class dominated by monoclonal antibodies (mAb), and, increasingly, their derivative constructs. Effective early assessment for drug-like properties (DLP) can save time and costs by allowing a more complete consideration of issues that could impact the desired end result of a stable drug product. Here we report a case study of four IgG1 mAbs, with sequence variations in the variable domain region, screened as a set of possible drug candidates. Our comprehensive, tiered approach used a battery of analytical tools to assess molecular characteristics, conformational stability, colloidal stability, and short-term storage stability. While most DLP for the four candidates were developmentally acceptable and comparable, mAb-2 was associated with adverse colloidal properties. Further investigation of mAb-2 in an expanded pH range revealed a propensity for phase separation, indicating a need for the additional product development effort. Our results support that comprehensive DLP assessments in an expanded pH range are beneficial in identifying development options for promising molecules that show challenging stability trends. This adaptable approach may be especially useful in the development of increasingly complex antibody constructs.

In Pursuit of Stability Enhancement of a Prostate Cancer Targeting Antibody Derived from a Transgenic Animal Platform

Accelerated timelines necessitate the discovery of fully human antibodies as biotherapeutics using transgenic animals with a notion that such mAbs bypass humanization. A transgenic animal derived mAb (PCa75) targeted against a prostate cancer antigen had several ‘unusual residues’ (rare somatic hypermutations, rSHM, with positional frequency of <1%) that resulted in compromised biophysical properties (Tm = 61 °C and intrinsic stability ΔGu = 24.3 kJ/mol) and a sub-optimal immunogenicity profile. In our quest for quality medicine, we pursued antibody engineering strategies to enhance the stability of PCa75. PCa62, an engineered variant of PCa75, retained function while significantly improving the drug-like attributes of the molecule (Tm = 75 °C and intrinsic stability ΔGu = 63.5 kJ/mol). rSHM is rather prevalent, 18 out the 21 approved transgenic animal-derived antibodies have at least one ‘unusual residue’. Thus, engineering of rSHM remains critical to enhance the stability and minimize immunogenicity risk of biotherapeutics.

Use of Target-Specific Liposome and Magnetic Nanoparticle Conjugation for the Amplified Detection of Norovirus

Viral diseases are one of the most life-threatening diseases as they can erupt unpredictably and spread rapidly in any medium with a very small number of particles. Therefore, the key for lethal virus detection should be highly sensitive in the early-stage detection, which can help increase the chance of survival. Amplification of the detecting signal is one of the most promising mechanisms for the detection of low-concentration analytes. A proper amplification can develop such a kind of system where a small number of particles can produce intense signals for a prominent detection. Keeping this in mind, in this report, we have presented a fluorometric method to detect norovirus (NoV) by a newly developed fluorophore-labeled liposome and a magnetically modified Fe₃O₄ combined system. Homogeneously distributed amine-functionalized liposomes have been constructed filled with a strong fluorophore of calcein. Simultaneously, (3-aminopropyl)-triethoxysilane (APTES)-functionalized Fe₃O₄ nanoparticles are also synthesized by the standard silanization process, and these two separately synthesized nanoparticles were functionalized with an antibody to achieve specificity. The Fe₃O₄ and calcein-liposome system has been applied for NoV detection, which was magnetically separated from the analyte medium and then externally burst to release the fluorophores from the core of the liposome. The easiness, rapidity, and sensitivity in a wide linear range can offer a huge potential of this method in point-of-care diagnostics.