A role for protein misfolding in immunogenicity of biopharmaceuticals

Immune response profiles induced by silk-based biomaterials: a journey from 'immunogenicity' towards 'immuno-compatibility

Silk is a widely accepted biomaterial for tissue regeneration owing to its tunable biomechanical properties and ease of chemical modification. However, a number of aspects associated with its clinical use are still debated. Indeed, to achieve clinical success, a biomaterial must favorably interact with host tissues without evoking local or systemic immuno-inflammatory responses. The analysis of immune responses associated with silk under in vitro and in vivo conditions provides useful insights, improving the understanding of the functional characteristics of silk biomaterials and further promoting their clinical application. Silk evokes moderate immune responses upon implantation in vivo, depending on the material structure, fabrication method, degradation time, and implantation in soft or hard tissue sites, which rapidly subside within a few days/weeks. In vitro studies indicate that its immune-stimulatory properties are largely due to inherent protein conformation and differential processing parameters. Strategically controlled levels of immune responses in vivo with marginal immunogenicity of silk-based biomaterials may contribute to matrix remodeling and replacement by native tissue matrix around the implanted site. Therefore, immunomodulatory strategies should be developed to promote the use of silk-based biomaterials as promising candidates for numerous clinical applications.

Basic regulatory science behind drug substance and drug product specifications of monoclonal antibodies and other protein therapeutics

In this review, we focus on providing basics and examples for each component of the protein therapeutic specifications to interested pharmacists and biopharmaceutical scientists with a goal to strengthen understanding in regulatory science and compliance. Pharmaceutical specifications comprise a list of important quality attributes for testing, references to use for test procedures, and appropriate acceptance criteria for the tests, and they are set up to ensure that when a drug product is administered to a patient, its intended therapeutic benefits and safety can be rendered appropriately. Conformance of drug substance or drug product to the specifications is achieved by testing an article according to the listed tests and analytical methods and obtaining test results that meet the acceptance criteria. Quality attributes are chosen to be tested based on their quality risk, and consideration should be given to the merit of the analytical methods which are associated with the acceptance criteria of the specifications. Acceptance criteria are set forth primarily based on efficacy and safety profiles, with an increasing attention noted for patient-centric specifications. Discussed in this work are related guidelines that support the biopharmaceutical specification setting, how to set the acceptance criteria, and examples of the quality attributes and the analytical methods from 60 articles and 23 pharmacopeial monographs. Outlooks are also explored on process analytical technologies and other orthogonal tools which are on-trend in biopharmaceutical characterization and quality control.

An Adjuvanted Vaccine-Induced Pathogenesis Following Influenza Virus Infection

An incomplete Freund's adjuvant elicited an overt pathogenesis in vaccinated mice following the intranasal challenge of A/California/07/2009 (H1N1) virus despite the induction of a higher specific antibody titer than other adjuvanted formulations. Aluminum hydroxide adjuvants have not induced any pathogenic signs in a variety of formulations with glycolipids. A glycolipid, α-galactosyl ceramide, improved a stimulatory effect of distinct adjuvanted formulations on an anti-influenza A antibody response. In contrast to α-galactosyl ceramide, its synthetic analogue C34 was antagonistic toward a stimulatory effect of an aluminum hydroxide adjuvant on a specific antibody response. The aluminum hydroxide adjuvant alone could confer complete vaccine-induced protection against mortality as well as morbidity caused by a lethal challenge of the same strain of an influenza A virus. The research results indicated that adjuvants could reshape immune responses either to improve vaccine-induced immunity or to provoke an unexpected pathogenic consequence. On the basis of these observations, this research connotes the prominence to develop a precision adjuvant for innocuous vaccination aimed at generating a protective immunity without aberrant responses.

Impact of Stress on the Immunogenic Potential of Adalimumab

Monoclonal antibodies against tumor necrosis factor-alpha (TNFα) are widely used for treatment of inflammatory diseases. However, despite the inhibitory effect this class of drugs has on the immune system, anti-drug antibodies are often formed with continuous use. Particles formed during stress conditions, which can be used to simulate storage and handling conditions of commercial antibodies, have previously been associated with the formation of anti-drug antibodies. This study investigates the relationship between particles, oligomerization, folding and chemical degradation on the in vitro cytokine response toward the TNFα inhibitor adalimumab. Adalimumab aggregates generated using stir and heat stress were fractionated into distinct sub-populations, and their structure and immunogenic potential were evaluated. A chemically degraded sample of adalimumab was included to compare particle composition with the milder accelerated heat and stir stressed conditions. Particles from stressed adalimumab samples induced elevated cytokine levels and CD4+ T cell proliferation in vitro compared to non-stressed samples. Samples enriched with both submicron and subvisible particles of adalimumab induced the strongest cytokine release and the strongest CD4+ T cell proliferation despite maintaining some TNFα inhibitory functionality. Samples that were stressed and subsequently purified of subvisible and submicron particles did not elicit a significantly higher cytokine response or show increased CD4+ T cell proliferation compared to a non-stressed sample. Oxidation-induced chemical modifications in adalimumab, mainly in Met, His, Trp, and Tyr, were not found to be sufficient in absence of particle formation to induce increased CD4+ T cell proliferation or cytokine release despite less decreased TNFα inhibitory activity of adalimumab. These observations provide further evidence that particles do indeed potentiate the immunogenic potential of adalimumab.

Surface-Induced Protein Aggregation and Particle Formation in Biologics: Current Understanding of Mechanisms, Detection and Mitigation Strategies

Protein stability against aggregation is a major quality concern for the production of safe and effective biopharmaceuticals. Amongst the different drivers of protein aggregation, increasing evidence indicates that interactions between proteins and interfaces represent a major risk factor for the formation of protein aggregates in aqueous solutions. Potentially harmful surfaces relevant to biologics manufacturing and storage include air-water and silicone oil-water interfaces as well as materials from different processing units, storage containers, and delivery devices. The impact of some of these surfaces, for instance originating from impurities, can be difficult to predict and control. Moreover, aggregate formation may additionally be complicated by the simultaneous presence of interfacial, hydrodynamic and mechanical stresses, whose contributions may be difficult to deconvolute. As a consequence, it remains difficult to identify the key chemical and physical determinants and define appropriate analytical methods to monitor and predict protein instability at these interfaces. In this review, we first discuss the main mechanisms of surface-induced protein aggregation. We then review the types of contact materials identified as potentially harmful or detected as potential triggers of proteinaceous particle formation in formulations and discuss proposed mitigation strategies. Finally, we present current methods to probe surface-induced instabilities, which represent a starting point towards assays that can be implemented in early-stage screening and formulation development of biologics.

Identification of tyrosine sulfation in the variable region of a bispecific antibody and its effect on stability and biological activity

Despite tyrosine sulfation being a relatively common post-translational modification (PTM) on the secreted proteins of higher eukaryotic organisms, there have been surprisingly few reports of this modification occurring in recombinant monoclonal antibodies (mAbs) expressed by mammalian cell lines and even less information regarding its potential impact on mAb efficacy and stability. This discrepancy is likely due to the extreme lability of this modification using many of the mass spectrometry methods typically used within the biopharmaceutical industry for PTM identification, as well as the possible misidentification as phosphorylation. Here, we identified sulfation on a single tyrosine residue located within the identical variable region sequence of a 2 + 1 bispecific mAbs heavy and heavy-heavy chains using a multi-enzymatic approach in combination with mass spectrometry analysis and examined its impact on binding, efficacy, and physical stability. Unlike previous reports, we found that tyrosine sulfation modestly decreased the mAb cell binding and T cell-mediated killing, primarily by increasing the rate of antigen disassociation as determined from surface plasmon resonance-binding experiments. We also found that, while this acidic modification had no significant impact on the mAb thermal stability, sulfation did modestly increase its rate of aggregation, presumably by lowering the mAb's colloidal stability as indicated by polyethylene glycol induced liquid-liquid phase separation experiments.

An update on the pathogenesis and diagnosis of thrombotic thrombocytopenic purpura

INTRODUCTION

Severe ADAMTS13 deficiency defines thrombotic thrombocytopenic purpura (TTP). ADAMTS13 is responsible for VWF cleavage. In the absence of this enzyme, widespread thrombi formation occurs, causing microangiopathic anemia and thrombocytopenia and leading to ischemic organ injury. Understanding ADAMTS13 function is crucial to diagnose and manage TTP, both in the immune and hereditary forms.

AREAS COVERED

The role of ADAMTS13 in coagulation homeostasis and the consequences of its deficiency are detailed. Other factors that modulate the consequences of ADAMTS13 deficiency are explained, such as complement system activation, genetic predisposition, or the presence of an inflammatory status. Clinical suspicion of TTP is crucial to start prompt treatment and avoid mortality and sequelae. Available techniques to diagnose this deficiency and detect autoantibodies or gene mutations are presented, as they have become faster and more available in recent years.

EXPERT OPINION

A better knowledge of TTP pathophysiology is leading to an improvement in diagnosis and follow-up, as well as a customized treatment in patients with TTP. This scenario is necessary to define the role of new targeted therapies already available or coming soon and the need to better diagnose and monitor at the molecular level the evolution of the disease.

Efficient Production of Fc Fusion Proteins in the Cytoplasm of Escherichia coli: Dissecting and Mitigating Redox Heterogeneity

Cost-effective production of therapeutic proteins in microbial hosts is an indispensable tool towards accessible healthcare. Many of these heterologously expressed proteins, including all antibody formats, require disulfide bond formation to attain their native and functional state. A system for catalyzed disulfide bond formation (CyDisCo) has been developed allowing efficient production of recombinant proteins in the cytoplasm of one of the most used microbial expression systems, Escherichia coli. Here, we report high-yield production (up to 230 mg/L from 3 mL cultures) of in-demand therapeutics such as IgG₁-based Fc fusion proteins in the E. coli cytoplasm. However, the production of this drug class using the CyDisCo system faces bottlenecks related to redox heterogeneity during oxidative folding. Our investigations identified and addressed one of the major causes of redox heterogeneity during CyDisCo-based production of Fc fusion proteins, i.e., disulfide bond formation in the IgG₁ C_H3 domain. Here, we communicate that mutating the cysteines in the C_H3 domain of target Fc fusion proteins allows their production in a homogeneous redox state in the cytoplasm of E. coli without compromising on yields and thermal stability.

Morphological integrity of insulin amyloid-like aggregates depends on preparation methods and post-production treatments

Protein aggregates are often varying extensively in their morphological characteristics, which may lead to various biological outcomes, such as increased immunogenicity risk. However, isolation of aggregates with a specific morphology within an ensemble is often challenging. To gain vital knowledge on the effects of aggregate characteristics, samples containing a single morphology must be produced by direct control of the aggregation process. Moreover, the formed aggregates need to be in an aqueous solution suitable for biological assays, while keeping their morphology intact. Here we evaluated the dependence of morphology and integrity of amyloid-like fibrils and spherulites on preparation conditions and post-treatment methods. Samples containing either amyloid-like fibrils or spherulites produced from human insulin in acetic acid solutions are dependent on the presence of salt (NaCl). Moreover, mechanical shaking (600 rpm) inhibits spherulite formation, while only affecting the length of the formed fibrils compared to quiescent conditions. Besides shaking, the initial protein concentration in the formulation was found to control fibril length. Surprisingly, exchanging the solution used for aggregate formation to a physiologically relevant buffer, had a striking effect on the morphological integrity of the fibril and spherulite samples. Especially the secondary structure of one of our spherulite samples presented dramatic changes of the aggregated β-sheet content after exchanging the solution, emphasizing the importance of the aggregate stability. These results and considerations have profound implications on the data interpretation and should be implemented in the workflow for both fundamental characterization of aggregates as well as assays for evaluation of their corresponding biological effects.

Poloxamer 188 as surfactant in biological formulations - An alternative for polysorbate 20/80?

Surfactants are used to stabilize biologics. Particularly, polysorbates (Tween® 20 and Tween® 80) dominate the group of surfactants in protein and especially antibody drug products. Since decades drug developers rely on the ethoxylated sorbitan fatty acid ester mixtures to stabilize sensitive molecules such as proteins. Reasons are (i) excellent stabilizing properties, and (ii) well recognized safety and tolerability profile of these polysorbates in humans, especially for parenteral applications. However, over the past decade concerns regarding the stability of these two polysorbates were raised. The search of alternatives with preferably less reservations concerning degradation and product quality reducing issues leads, among others, to poloxamer 188 (e.g. Kolliphor® P188), a nonionic triblock-copolymer surfactant. This review sums up our current knowledge related to the characterization and physico-chemical properties of poloxamer 188, its analytics and stability properties for biological formulations. Furthermore, the advantages and disadvantages as a suitable polysorbate-alternative for the stabilization of biologics are discussed.

Is it possible to make a common reference standard for D-dimer measurements? Communication from the ISTH SSC Subcommittee on Fibrinolysis

BACKGROUND

D-dimer antigen is a heterogeneous mixture of fibrin degradation products that when present at high levels in plasma indicate ongoing coagulation and fibrinolysis. The heterogeneous nature of the target D-dimer antigen and the variety of assay systems means that it is difficult to compare results from different methods.

OBJECTIVES

To identify a universally agreed D-dimer standard that could help harmonize results from different methods.

METHODS

A pool of patient plasma with high D-dimer levels was freeze-dried and investigated as a long-term World Health Organization international standard for D-dimer. Fibrin degradation products from clot lysis reactions were also freeze-dried in various formulations and investigated in commutability studies with patient plasma.

RESULTS

Problems of instability of D-dimer plasma emerged suggesting loss of reactivity after freeze-drying and storage at -20°C of 10%-18% per year. Freeze-dried fibrin degradation products added to plasma were also unstable, but the sugar trehalose was found to improve stability. However, this preparation was not suitable as a standard in widely used assay platforms. Previous studies suggest fibrin degradation products are prone to structural rearrangements and amyloid formation, which may explain the instability of candidate D-dimer standards.

CONCLUSIONS

The known difficulties of D-dimer standardization are compounded by instability of D-dimer antigen after freeze-drying, described in this report. Fibrin degradation products added to plasma and stabilized by trehalose are not suitable as a standard for D-dimer measurement harmonization. Trehalose stabilization of pooled patient plasma containing high D-dimer levels may produce a useful standard, but this requires confirmation.

Suppression of Electrostatic Mediated Antibody Liquid-Liquid Phase Separation by Charged and Noncharged Preferentially Excluded Excipients

Isotonic concentrations of inert cosolutes or excipients are routinely used in protein therapeutic formulations to minimize physical instabilities including aggregation, particulation, and precipitation that are often manifested during drug substance/product manufacture and long-term storage. Despite their prevalent use within the biopharmaceutical industry, a more detailed understanding for how excipients modulate the specific protein-protein interactions responsible for these instabilities is still needed so that informed formulation decisions can be made at the earliest stages of development when protein supply and time are limited. In the present report, subisotonic concentrations of the five common formulation excipients, sucrose, proline, sorbitol, glycerol, arginine hydrochloride, and the denaturant urea, were studied for their effect on the room temperature liquid-liquid phase separation of a model monoclonal antibody (mAb-B). Although each excipient lowered the onset temperatures of mAb-B liquid-liquid phase separation to different extents, all six were found to be preferentially excluded from the native state monomer by vapor pressure osmometry, and no apparent correlations to the excipient dependence of mAb-B melting temperatures were observed. These results and those of the effects of solution pH, addition of salt, and impact of a small number of charge mutations were most consistent with a mechanism of local excipient accumulation, to an extent dependent on their type, with the specific residues that mediate mAb-B electrostatic protein-protein interactions. These findings suggest that selection of excipients on the basis of their interaction with the solvent exposed residues of the native state may at times be a more effective strategy for limiting protein-protein interactions at pharmaceutically relevant storage conditions than choosing those that are excluded from the residues of the native state interior.

The Impact of Product and Process Related Critical Quality Attributes on Immunogenicity and Adverse Immunological Effects of Biotherapeutics

The pharmaceutical industry has experienced great successes with protein therapeutics in the last two decades and with novel modalities, including cell therapies and gene therapies, more recently. Biotherapeutics are complex in structure and present challenges for discovery, development, regulatory, and life cycle management. Biotherapeutics can interact with the immune system that may lead to undesired immunological responses, including immunogenicity, hypersensitivity reactions (HSR), injection site reactions (ISR), and others. Many product and process related critical quality attributes (CQAs) have the potential to trigger or augment such immunological responses to the product. Tremendous efforts, both clinically and preclinically, have been invested to understand the impact of product and process related CQAs on adverse immunological effects. The information and knowledge are critical for the implementation of Quality by Design (QbD), which requires risk assessment and establishment of specifications and control strategies for CQAs. A quality target product profile (QTPP) that identifies the key CQAs through process development can help assign severity scores based on safety, immunogenicity, pharmacokinetics (PK) and pharmacodynamics (PD) of the molecule. Gaps and future directions related to biotherapeutics and emerging novel modalities are presented.

Multivariate Optimization of the Refolding Process of an Incorrectly Folded Fc-Fusion Protein in a Cell Culture Broth

BACKGROUND

Protein misfolding is a common problem in large-scale production of recombinant proteins, which can significantly reduce the yield of the process.

OBJECTIVE

In this work, we aimed at treating a cell culture broth containing high levels (>45%) of incorrectly folded Fc-fusion proteins by a simple redox buffer system in order to increase the proportion of the protein with correct conformation.

METHODS

Multi-variable process optimization was firstly conducted at a small scale (25 mL), employing an experimental design methodology. After identifying the key variables using a resolution IV Fractional Factorial Design (FFD), the process was then optimized by the Central Composite Design (CCD).

RESULTS

The optimal conditions for the refolding reaction were 340 mM Tris-base, 6.0 mM L-cysteine, 0.5 mM L-cystine, a buffer pH of 9.0, a reaction temperature of 8.5ºC and a reaction time of 24 h. Based on the treatment conditions obtained at a small scale, the process was further scaled up to 4500- L. The misfolded content was always less than 20%. The reaction can proceed well in the absence of chemical additives, such as chaotropic agents, aggregation suppressors, stabilizers and chelators.

CONCLUSION

The refolding process increases the fraction of active protein in the original broth reducing the burden on downstream purification steps markedly.

Advances in the Development of Pharmacological Chaperones for the Mucopolysaccharidoses

The mucopolysaccharidoses (MPS) are a group of 11 lysosomal storage diseases (LSDs) produced by mutations in the enzymes involved in the lysosomal catabolism of glycosaminoglycans. Most of the mutations affecting these enzymes may lead to changes in processing, folding, glycosylation, pH stability, protein aggregation, and defective transport to the lysosomes. It this sense, it has been proposed that the use of small molecules, called pharmacological chaperones (PCs), can restore the folding, trafficking, and biological activity of mutated enzymes. PCs have the advantages of wide tissue distribution, potential oral administration, lower production cost, and fewer issues of immunogenicity than enzyme replacement therapy. In this paper, we will review the advances in the identification and characterization of PCs for the MPS. These molecules have been described for MPS II, IVA, and IVB, showing a mutation-dependent enhancement of the mutated enzymes. Although the results show the potential of this strategy, further studies should focus in the development of disease-specific cellular models that allow a proper screening and evaluation of PCs. In addition, in vivo evaluation, both pre-clinical and clinical, should be performed, before they can become a real therapeutic strategy for the treatment of MPS patients.

Isotonic concentrations of excipients control the dimerization rate of a therapeutic immunoglobulin G1 antibody during refrigerated storage based on their rank order of native-state interaction

Inert co-solutes, or excipients, are often included in protein biologic formulations to adjust the tonicity of liquid dosage forms intended for subcutaneous delivery. Despite the low concentration of their use, many of these excipients alter protein-protein interactions such as dimerization and aggregation rates of high concentration monoclonal antibody (mAb) therapeutics to varying extents during long-term refrigerated clinical storage, challenging the formulation scientist to make informed excipient selections at the earliest stages of development when protein supply and time are often limited. The objectives of this study were to better understand how isotonic concentrations of excipients influence the dimerization rates of a model mAb stored at refrigerated and room temperatures and explore protein sparing biophysical methods capable of predicting this dependence. Despite their prevalence of use in the biopharmaceutical industry, methods for assessing conformational stability such differential scanning calorimetry and isothermal equilibrium unfolding showed little predictive power and we highlight some of the assumptions and technical challenges of their use with mAbs. Conversely, measures of colloidal stability of the native-state such as preferential interaction coefficients measured by vapor pressure osmometry and solubility assessed by polyethylene-glycol induced precipitation correlated reasonably well with the mAb dimerization data and are most consistent with the excipients tested minimizing dimerization by interacting favorably with the residues comprising the protein-protein association interface.

Identification of Ezetimibe and Pranlukast as Pharmacological Chaperones for the Treatment of the Rare Disease Mucopolysaccharidosis Type IVA

Mucopolysaccharidosis type IVA (MPS IVA) is a rare disease caused by mutations in the gene encoding the lysosomal enzyme N-acetylgalactosamine-6-sulfate sulfatase (GALNS). We report here two GALNS pharmacological chaperones, ezetimibe and pranlukast, identified by molecular docking-based virtual screening. These compounds bound to the active cavity of GALNS and increased its thermal stability as well as the production of recombinant GALNS in bacteria, yeast, and HEK293 cells. MPS IVA fibroblasts treated with these chaperones exhibited increases in GALNS protein and enzyme activity and reduced the size of enlarged lysosomes. Abnormalities in autophagy markers p62 and LC3B-II were alleviated by ezetimibe and pranlukast. Combined treatment of recombinant GALNS with ezetimibe or pranlukast produced an additive effect. Altogether, the results demonstrate that ezetimibe and pranlukast can increase the yield of recombinant GALNS and be used as a monotherapy or combination therapy to improve the therapeutic efficacy of MPS IVA enzyme replacement therapy.

Stabilized Interleukin-4-Loaded Poly(lactic-co-glycolic) Acid Films Shift Proinflammatory Macrophages toward a Regenerative Phenotype in Vitro

Macrophages are immune cells involved in wound healing and tissue regeneration; however, the sustained presence of proinflammatory macrophages in wound sites impairs healing. In this study, we shifted peritoneal macrophage polarization away from a proinflammatory (M1) phenotype through exposure to stabilized interleukin-4 (IL-4) in poly(lactic-co-glycolic acid) films in combination with topographical guidance from electrospun poly-L-lactic acid fibers. To our knowledge, this was the first study to stabilize IL-4 with bovine serum albumin (BSA) within a biomaterial. When IL-4 was coloaded with BSA for stabilization, we saw increased IL-4 bioactivity compared to no added stabilization, trehalose stabilization, or murine serum albumin stabilization. We observed increased elongation of peritoneal macrophages, increased RNA expression of anti-inflammatory marker arginase-1, increased ratio of interleukin-10/interleukin- 12 p40 RNA, and decreased protein expression of proinflammatory markers (interleukin-12 p40 and RANTES) compared to controls. Taken together, these results suggest the macrophages were less proinflammatory and were a more pro-resolving phenotype. When stabilized with BSA, IL-4-loaded films effectively shift macrophage polarization state and are thus promising scaffolds to reduce inflammation within in vivo injury models.

Therapeutic Fc fusion protein misfolding: A three-phasic cultivation experimental design

Cell culture process optimization is a critical solution to most of the challenges faced by the pharmaceutical manufacturing. One of the major problems encountered in large-scale production of therapeutic proteins is misfolded protein production. The accumulation of misfolded therapeutic proteins is an immunogenic signal and a risk factor for immunogenicity of the final product. The aim of this study was the statistical optimization of three-phasic temperature shift and timing for enhanced production of correctly folded Fc-fusion protein. The effect of culture temperatures were investigated using the biphasic culture system. Box-Behnken design was then used to compute temperature and time of shifting optimum. Response surface methodology revealed that maximum production with low level of misfolded protein was achieved at two-step temperature shift from 37°C to 30°C during the late logarithmic phase and 30°C to 28°C in the mid-stationary phase. The optimized condition gave the best results of 1860 mg L-1 protein titer with 24.5% misfolding level. The validation experiments were carried out under optimal conditions with three replicates and the protein misfolding level was decreased by two times while productivity increased by ~ 1.3-fold. Large-scale production in 250 L bioreactor under the optimum conditions was also verified the effectiveness and the accuracy of the model. The results showed that by utilizing two-step temperature shift, productivity and the quality of target protein have been improved simultaneously. This model could be successfully applied to other products.

Identification of B cell epitopes enhanced by protein unfolding and aggregation

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Aggregation of an exemplar therapeutic antibody fragment (scFv) enhances immunogenicity in vivo.

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Epitope mapping reveals immunogenicity is directed to a specific epitope in aggregate species.

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Molecular simulation demonstrates biophysical stress enhances epitope presentation.

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Protein aggregates have distinct immunological profiles to their native counterparts.

Aggregation of therapeutic proteins is a key factor in the generation of unwanted immunogenicity, and can result in reduced serum half-life, neutralization of function and adverse health effects. There is currently little information regarding how aggregates interact with B-cell receptors or cognate antibodies at the protein sequence level, or whether non-native, aggregate-induced epitopes predominate in these interactions. Using an antibody fragment (single chain antibody variable fragment; scFv) that forms aggregates readily at low temperature, anti-scFv IgG antibody responses were generated by intraperitoneal injection of BALB/c strain mice with monomer or aggregate preparations. Aggregate-specific immunosignatures were identified by oligo-peptide microarray fine epitope mapping, using overlapping 15mer peptides based on the linear sequence of scFv, printed onto glass slides. IgG antibodies from mice immunized with aggregated scFv preferentially recognized a patch of overlapping peptides. This region mapped to a β-strand located at the interface between the V_H and V_L domains. Molecular dynamics simulations indicated that the V_L domain is less stable than the V_H domain, suggesting the interface region between the two domains becomes exposed during partial unfolding of the scFv during aggregate formation. These data are consistent with the hypothesis that epitopes from partially unfolded states are revealed, or are more fully exposed, in the aggregated state, and that this can augment the IgG antibody response. This observation offers the theoretical possibility that epitopes preferentially associated with aggregates can be identified from the anti-drug antibody serum IgG response which may, in turn, lead to better methods for detection of anti-drug antibody responses, and improved design of therapeutic proteins to control immunogenicity.

Understanding Effects of PAMAM Dendrimer Size and Surface Chemistry on Serum Protein Binding with Discrete Molecular Dynamics Simulations

Polyamidoamine (PAMAM) dendrimers, a class of polymeric nanoparticles (NPs) with highly-controllable sizes and surface chemistry, are promising candidates for many biomedical applications, including drug and gene delivery, imaging, and inhibition of amyloid aggregation. In circulation, binding of serum proteins with dendritic NPs renders the formation of protein corona and alters the biological identity of the NP core, which may subsequently elicit immunoresponse and cytotoxicity. Understanding the effects of PAMAM size and surface chemistry on serum protein binding is, therefore, crucial to enable their broad biomedical applications. Here, by applying atomistic discrete molecular dynamics (DMD) simulations, we first uncovered the binding of PAMAM with HSA and Ig and detailed the dependences of such binding on PAMAM size and surface modification. Compared to either anionic or cationic surfaces, modifications with neutral phosphorylcholine (PC), polyethylene glycol (PEG), and hydroxyls (OH) significantly reduced binding with proteins. The relatively strong binding between proteins and PAMAM dendrimers with charged surface groups was mainly driven by electrostatic interactions as well as hydrophobic interactions. Using steered DMD (SDMD) simulations, we conducted a force-pulling experiment in silico estimating the critical forces separating PAMAM-protein complexes and deriving the corresponding free energy barriers for dissociation. The SDMD-derived HSA-binding affinities were consistent with existing experimental measurements. Our results highlighted the association dynamics of protein-dendrimer interactions and binding affinities, whose implications range from fundamental nanobio interfacial phenomena to the development of "stealth NPs".

Sustained delivery of vascular endothelial growth factor using a dextran/poly(lactic-co-glycolic acid)-combined microsphere system for therapeutic neovascularization

We hypothesize that the controlled delivery of vascular endothelial growth factor (VEGF) using a novel protein sustained-release system based on the combination of protein-loaded dextran microparticles and PLGA microspheres could be useful to achieve mature vessel formation in a rat hind-limb ischemic model. VEGF-loaded dextran microparticles were fabricated and then encapsulated into poly(lactic-co-glycolic acid) (PLGA) microspheres to prepare VEGF-dextran-PLGA microspheres. The release behavior and bioactivity in promoting endothelial cell proliferation of VEGF from PLGA microspheres were monitored in vitro. VEGF-dextran-PLGA microsphere-loaded fibrin gel was injected into an ischemic rat model, and neovascularization at the ischemic site was evaluated. The release of VEGF from PLGA microspheres was in a sustained manner for more than 1 month in vitro with low level of initial burst release. The released VEGF enhanced the proliferation of endothelial cells in vitro, and significantly promoted the capillaries and smooth muscle α-actin positive vessels formation in vivo. The retained bioactivity of VEGF released from VEGF-dextran-PLGA microspheres potentiated the angiogenic efficacy of VEGF. This sustained-release system may be a promising vehicle for delivery of multiple angiogenic factors for therapeutic neovascularization.

Characterization of Aptamer BC 007 Substance and Product Using Circular Dichroism and Nuclear Magnetic Resonance Spectroscopy

Possible unwanted folding of biopharmaceuticals during manufacturing and storage has resulted in analysis schemes compared to small molecules that include bioanalytical characterization besides chemical characterization. Whether bioanalytical characterization is required for nucleotide-based drugs, may be decided on a case-by-case basis. Nucleotide-based pharmaceuticals, if chemically synthesized, occupy an intermediate position between small-molecule drugs and biologics. Here, we tested whether a physicochemical characterization of a nucleotide-based drug substance, BC 007, was adequate, using circular dichroism (CD) spectroscopy. Nuclear magnetic resonance confirmed CD data in one experimental setup. BC 007 forms a quadruplex structure under specific external conditions, which was characterized for its stability and structural appearance also after denaturation using CD and nuclear magnetic resonance. The amount of the free energy (ΔG⁰) involved in quadruplex formation of BC 007 was estimated at +8.7 kJ/mol when dissolved in water and +1.4 kJ/mol in 154 mM NaCl, indicating structural instability under these conditions. However, dissolution of the substance in 5 mM of KCl reduced the ΔG⁰ to -5.6 kJ/mol due to the stabilizing effect of cations. These results show that positive ΔG⁰ of quadruplex structure formation in water and aqueous NaCl prevents BC 007 from preforming stable 3-dimensional structures, which could potentially affect drug function.

Optical Detection of Degraded Therapeutic Proteins

The quality of therapeutic proteins such as hormones, subunit and conjugate vaccines, and antibodies is critical to the safety and efficacy of modern medicine. Identifying malformed proteins at the point-of-care can prevent adverse immune reactions in patients; this is of special concern when there is an insecure supply chain resulting in the delivery of degraded, or even counterfeit, drug product. Identification of degraded protein, for example human growth hormone, is demonstrated by applying automated anomaly detection algorithms. Detection of the degraded protein differs from previous applications of machine-learning and classification to spectral analysis: only example spectra of genuine, high-quality drug products are used to construct the classifier. The algorithm is tested on Raman spectra acquired on protein dilutions typical of formulated drug product and at sample volumes of 25 µL, below the typical overfill (waste) volumes present in vials of injectable drug product. The algorithm is demonstrated to correctly classify anomalous recombinant human growth hormone (rhGH) with 92% sensitivity and 98% specificity even when the algorithm has only previously encountered high-quality drug product.

An open conformation of ADAMTS-13 is a hallmark of acute acquired thrombotic thrombocytopenic purpura

Essentials Conformational changes in ADAMTS-13 are part of its mode-of-action. The murine anti-ADAMTS-13 antibody 1C4 discriminates between folded and open ADAMTS-13. ADAMTS-13 conformation is open in acute acquired thrombotic thrombocytopenic purpura (TTP). Our study forms an important basis to fully elucidate the pathophysiology of TTP.

SUMMARY

Background Acquired thrombotic thrombocytopenic purpura (aTTP) is an autoimmune disorder characterized by absent ADAMTS-13 activity and the presence of anti-ADAMTS-13 autoantibodies. Recently, it was shown that ADAMTS-13 adopts a folded or an open conformation. Objectives As conformational changes in self-antigens play a role in the pathophysiology of different autoimmune diseases, we hypothesized that the conformation of ADAMTS-13 changes during acute aTTP. Methods Antibodies recognizing cryptic epitopes in the spacer domain were generated. Next, the conformation of ADAMTS-13 in 40 healthy donors (HDs), 99 aTTP patients (63 in the acute phase versus 36 in remission), 12 hemolytic-uremic syndrome (HUS) patients and 63 sepsis patients was determined with ELISA. Results The antibody 1C4 recognizes a cryptic epitope in ADAMTS-13. Therefore, we were able to discriminate between a folded and an open ADAMTS-13 conformation. We showed that ADAMTS-13 in HDs does not bind to 1C4, indicating that ADAMTS-13 circulates in a folded conformation. Similar results were obtained for HUS and sepsis patients. In contrast, ADAMTS-13 of acute aTTP patients bound to 1C4 in 92% of the cases, whereas, in most cases, this binding was abolished during remission, showing that the conformation of ADAMTS-13 is open during an acute aTTP episode. Conclusions Our study shows that, besides absent ADAMTS-13 activity and the presence of anti-ADAMTS-13 autoantibodies, an open ADAMTS-13 conformation is also a hallmark of acute aTTP. Demonstrating this altered ADAMTS-13 conformation in acute aTTP will help to further unravel the pathophysiology of aTTP and lead to improved therapy and diagnosis.

New therapeutic approaches for Krabbe disease: The potential of pharmacological chaperones

Missense mutations in the lysosomal hydrolase β‐galactocerebrosidase (GALC) account for at least 40% of known cases of Krabbe disease (KD). Most of these missense mutations are predicted to disrupt the fold of the enzyme, preventing GALC in sufficient amounts from reaching its site of action in the lysosome. The predominant central nervous system (CNS) pathology and the absence of accumulated primary substrate within the lysosome mean that strategies used to treat other lysosomal storage disorders (LSDs) are insufficient in KD, highlighting the still unmet clinical requirement for successful KD therapeutics. Pharmacological chaperone therapy (PCT) is one strategy being explored to overcome defects in GALC caused by missense mutations. In recent studies, several small‐molecule inhibitors have been identified as promising chaperone candidates for GALC. This Review discusses new insights gained from these studies and highlights the importance of characterizing both the chaperone interaction and the underlying mutation to define properly a responsive population and to improve the translation of existing lead molecules into successful KD therapeutics. We also highlight the importance of using multiple complementary methods to monitor PCT effectiveness. Finally, we explore the exciting potential of using combination therapy to ameliorate disease through the use of PCT with existing therapies or with more generalized therapeutics, such as proteasomal inhibition, that have been shown to have synergistic effects in other LSDs. This, alongside advances in CNS delivery of recombinant enzyme and targeted rational drug design, provides a promising outlook for the development of KD therapeutics. © 2016 The Authors. Journal of Neuroscience Research Published by Wiley Periodicals, Inc.

NanoEHS beyond Toxicity - Focusing on Biocorona

The first phase of environmental health and safety of nanomaterials (nanoEHS) studies has been mainly focused on evidence-based investigations that probe the impact of nanoparticles, nanomaterials and nano-enabled products on biological and ecological systems. The integration of multiple disciplines, including colloidal science, nanomaterial science, chemistry, toxicology/immunology and environmental science, is necessary to understand the implications of nanotechnology for both human health and the environment. While strides have been made in connecting the physicochemical properties of nanomaterials with their hazard potential in tiered models, fundamental understanding of nano-biomolecular interactions and their implications for nanoEHS is largely absent from the literature. Research on nano-biomolecular interactions within the context of natural systems not only provides important clues for deciphering nanotoxicity and nanoparticle-induced pathology, but also presents vast new opportunities for screening beneficial material properties and designing greener products from bottom up. This review highlights new opportunities concerning nano-biomolecular interactions beyond the scope of toxicity.

Biomaterials Made from Coiled-Coil Peptides

The development of biomaterials designed for specific applications is an important objective in personalized medicine. While the breadth and prominence of biomaterials have increased exponentially over the past decades, critical challenges remain to be addressed, particularly in the development of biomaterials that exhibit highly specific functions. These functional properties are often encoded within the molecular structure of the component molecules. Proteins, as a consequence of their structural specificity, represent useful substrates for the construction of functional biomaterials through rational design. This chapter provides an in-depth survey of biomaterials constructed from coiled-coils, one of the best-understood protein structural motifs. We discuss the utility of this structurally diverse and functionally tunable class of proteins for the creation of novel biomaterials. This discussion illustrates the progress that has been made in the development of coiled-coil biomaterials by showcasing studies that bridge the gap between the academic science and potential technological impact.

Main Quality Attributes of Monoclonal Antibodies and Effect of Cell Culture Components

The culture media optimization is an inevitable part of upstream process development in therapeutic monoclonal antibodies (mAbs) production. The quality by design (QbD) approach defines the assured quality of the final product through the development stage. An important step in QbD is determination of the main quality attributes. During the media optimization, some of the main quality attributes such as glycosylation pattern, charge variants, aggregates, and low-molecular-weight species, could be significantly altered. Here, we provide an overview of how cell culture medium components affects the main quality attributes of the mAbs. Knowing the relationship between the culture media components and the main quality attributes could be successfully utilized for a rational optimization of mammalian cell culture media for industrial mAbs production.

Mechanism of plasmin generation by S100A10

Plasminogen (Pg) is cleaved to form plasmin by the action of specific plasminogen activators such as the tissue plasminogen activator (tPA). Although the interaction of tPA and Pg with the surface of the fibrin clot has been well characterised, their interaction with cell surface Pg receptors is poorly understood. S100A10 is a cell surface Pg receptor that plays a key role in cellular plasmin generation. In the present report, we have utilised domain-switched/deleted variants of tPA, truncated plasminogen variants and S100A10 site-directed mutant proteins to define the regions responsible for S100A10-dependent plasmin generation. In contrast to the established role of the finger domain of tPA in fibrin-stimulated plasmin generation, we show that the kringle-2 domain of tPA plays a key role in S100A10-dependent plasmin generation. The kringle-1 domain of plasminogen, indispensable for fibrin-binding, is also critical for S100A10-dependent plasmin generation. S100A10 retains activity after substitution or deletion of the carboxyl-terminal lysine suggesting that internal lysine residues contribute to its plasmin generating activity. These studies define a new paradigm for plasminogen activation by the plasminogen receptor, S100A10.

Practically feasible production of sustained-release microspheres of granulocyte-macrophage colony-stimulating factor (rhGM-CSF)

Using recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) as a model drug, the present study demonstrated a practically feasible process to produce polymeric microspheres for sustained-release delivery of protein drugs with preserved integrity. This process is featured with pre-loading proteins into polysaccharide fine particles via a self-standing aqueous-aqueous "emulsion", prior to microencapsulation into the microspheres. The protein drug, rhGM-CSF, was partitioned thermodynamically into a dextran dispersed phase of the aqueous-aqueous emulsion, followed by lyophilization and removal of the polyethylene glycol (PEG) continuous phase (using an organic solvent not penetrating into dextran matrix). The harvested dextran particles were then suspended in a dichloromethane solution of polylatic-co-glyclic acids (PLGA) and emulsified in a polyvinyl alcohol (PVA) and NaCl solution of small volume to form embryonic microspheres. The emulsion was then transferred into a NaCl solution of large volume to extract the organic solvent and harden the embryonic microspheres. The obtained rhGM-CSF microspheres showed a satisfied release profile with the day-to-day variation within 9 folds over the multi-weeks long release period. At the same time, the integrity (defined freedom of aggregates measured by SEC-HPLC) and bioactivity (defined by TF-1 cell proliferation) of the proteins were well preserved. The present formulation process ensured good reproducibility and over 89% protein encapsulation efficiency, and practically feasible to adapt to scaled productions.

Assessment of disulfide and hinge modifications in monoclonal antibodies

During the last years there was a substantial increase in the use of antibodies and related proteins as therapeutics. The emphasis of the pharmaceutical industry is on IgG1, IgG2, and IgG4 antibodies, which are therefore in the focus of this article. In order to ensure appropriate quality control of such biopharmaceuticals, deep understanding of their chemical degradation pathways and the resulting impact on potency, pharmacokinetics, and safety is required. Criticality of modifications may be specific for individual antibodies and has to be assessed for each molecule. However, some modifications of conserved structure elements occur in all or at least most IgGs. In these cases, criticality assessment may be applicable to related molecules or molecule formats. The relatively low dissociation energy of disulfide bonds and the high flexibility of the hinge region frequently lead to modifications and cleavages. Therefore, the hinge region and disulfide bonds require specific consideration during quality assessment of mAbs. In this review, available literature knowledge on underlying chemical reaction pathways of modifications, analytical methods for quantification and criticality are discussed. The hinge region is prone to cleavage and is involved in pathways that lead to thioether bond formation, cysteine racemization, and iso‐Asp (Asp, aspartic acid) formation. Disulfide or sulfhydryl groups were found to be prone to reductive cleavage, trisulfide formation, cysteinylation, glutathionylation, disulfide bridging to further light chains, and disulfide scrambling. With regard to potency, disulfide cleavage, hinge cleavage, disulfide bridging to further light chains, and cysteinylation were found to influence antigen binding and fragment crystallizable (Fc) effector functionalities. Renal clearance of small fragments may be faster, whereas clearance of larger fragments appears to depend on their neonatal Fc receptor (FcRn) functionality, which in turn may be impeded by disulfide bond cleavage. Certain modifications such as disulfide induced aggregation and heterodimers from different antibodies are generally regarded critical with respect to safety. However, the detection of some modifications in endogenous antibodies isolated from human blood and the possibility of in vivo repair mechanisms may reduce some safety concerns.

Effect of growth hormone and IgG aggregates on dendritic cells activation and T-cells polarization

Patients treated with therapeutic biological products (BP) frequently develop anti-drug antibodies (ADA) with potential neutralizing capacities leading to loss of clinical response or serious side effects. BP aggregates have been suggested to promote immunogenicity, thus enhancing ADA production. Dendritic cells (DC) are key effectors in T-cell and B-cell fates, and the subsequent generation of immunogenicity. The objective of this work was to determine if BP aggregates can participate to DC maturation and T-cell activation. We compared aggregates from three different proteins: human growth hormone (hGH), Rituximab, a chimeric anti-CD20 antibody and a serum-purified human IgG1. All three proteins underwent a stir stress, generating comparable populations of aggregated particles. Maturation of human monocyte-derived DC (moDC) upon exposure to native BPs or aggregates was evaluated in vitro. Results showed that hGH aggregates induced an increased expression of moDC co-stimulation markers, and augmented levels of IL-6, IL-8, IL-12p40, CCL2, CCL3, CCL4 and CXCL10. Both antibodies aggregates were also able to modify DC phenotype, but cytokine and chemokine productions were seen only with IL-6, IL-8, IL-12p40 and CXCL10. Aggregates-treated moDC enhanced allogenic T-cell proliferation and cytokines production, suggesting Th1 polarization with hGH, and mixed T-cell responses with antibodies aggregates. These results showed that BP aggregates provoked DC maturation, thus driving adaptive T-cell responses and polarization.

Maillard reaction and immunogenicity of protein therapeutics

The recombinant DNA technology enabled the production of a variety of human therapeutic proteins. Accumulated clinical experience, however, indicates that the formation of antibodies against such proteins is a general phenomenon rather than an exception. The immunogenicity of therapeutic proteins results in inefficient therapy and in the development of undesired, sometimes life-threatening, side reactions. The human proteins, designed for clinical application, usually have the same amino acid sequence as their native prototypes and it is not yet fully clear what the reasons for their immunogenicity are. In previous studies we have demonstrated for the first time that interferon-β (IFN-β) pharmaceuticals, used for treatment of patients with multiple sclerosis, do contain advanced glycation end products (AGEs) that contribute to IFN-β immunogenicity. AGEs are the final products of a chemical reaction known as the Maillard reaction or glycation, which implication in protein drugs’ immunogenicity has been overlooked so far. Therefore, the aim of the present article is to provide a comprehensive overview on the Maillard reaction with emphasis on experimental data and theoretical consideration telling us why the Maillard reaction warrants special attention in the context of the well-documented protein drugs’ immunogenicity.

Limited proteolysis and peptide mapping for comparability of biopharmaceuticals: An evaluation of repeatability, intra-assay precision and capability to detect structural change

The use of limited proteolysis followed by peptide mapping for the comparability of the higher-order structure of biopharmaceuticals was investigated. In this approach the proteolysis is performed under non-reducing and non-denaturing conditions, and the resulting peptide map is determined by the samples primary and higher order structures. This allows comparability of biopharmaceuticals to be made in terms of their higher order structure, using a method that is relatively simple to implement. The digestion of a monoclonal antibody under non-denaturing conditions was analyzed using peptide mapping, circular dichroism (CD) and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). This allowed an optimal digestion time to be chosen. This method was then assessed for its ability to detect structural change using a monoclonal antibody, which had been subjected to a range of stresses; deglycosylation, mild denaturation and a batch that had failed specifications due to in-process reduction. The repeatability and inter-assay precision were assessed. It was demonstrated that the limited proteolysis peptide maps of the three stressed samples were significantly different to control samples and that the differences observed were consistent between the occasions when the assays were run. A combination of limited proteolysis and CD or SDS-PAGE analysis was shown to enhance the capacity of these techniques to detect structural change, which otherwise would not have been observed.

Basic mechanisms and regulation of fibrinolysis

Fibrinolysis appears in many diverse physiological situations, and the components of the system are well established, along with mechanistic details for the individual reactions and some high-resolution structures. Key questions in understanding the regulation of fibrinolysis surround mechanisms of initiation and propagation, the localization of fibrinolysis reactions to the fibrin clot, and the influence of fibrin structure and clot composition on thrombolysis. This review covers these key areas with a focus on recent developments on fibrin structure and binding, the effects of a variety of cell types, the consequences of histones and DNA released by neutrophils, and the influence of flow. A complete understanding of the regulation of fibrinolysis will come from the building of detailed mathematical models. Suitable models are at an early stage of development, but may improve as model clots increase in complexity to incorporate the components and interactions listed above.

Azasugar inhibitors as pharmacological chaperones for Krabbe disease

Krabbe disease is a devastating neurodegenerative disorder characterized by rapid demyelination of nerve fibers. This disease is caused by defects in the lysosomal enzyme β-galactocerebrosidase (GALC), which hydrolyzes the terminal galactose from glycosphingolipids. These lipids are essential components of eukaryotic cell membranes: substrates of GALC include galactocerebroside, the primary lipid component of myelin, and psychosine, a cytotoxic metabolite. Mutations of GALC that cause misfolding of the protein may be responsive to pharmacological chaperone therapy (PCT), whereby small molecules are used to stabilize these mutant proteins, thus correcting trafficking defects and increasing residual catabolic activity in cells. Here we describe a new approach for the synthesis of galacto-configured azasugars and the characterization of their interaction with GALC using biophysical, biochemical and crystallographic methods. We identify that the global stabilization of GALC conferred by azasugar derivatives, measured by fluorescence-based thermal shift assays, is directly related to their binding affinity, measured by enzyme inhibition. X-ray crystal structures of these molecules bound in the GALC active site reveal which residues participate in stabilizing interactions, show how potency is achieved and illustrate the penalties of aza/iminosugar ring distortion. The structure-activity relationships described here identify the key physical properties required of pharmacological chaperones for Krabbe disease and highlight the potential of azasugars as stabilizing agents for future enzyme replacement therapies. This work lays the foundation for new drug-based treatments of Krabbe disease.

Advances in phage display technology for drug discovery

INTRODUCTION

Over the past decade, several library-based methods have been developed to discover ligands with strong binding affinities for their targets. These methods mimic the natural evolution for screening and identifying ligand-target interactions with specific functional properties. Phage display technology is a well-established method that has been applied to many technological challenges including novel drug discovery.

AREAS COVERED

This review describes the recent advances in the use of phage display technology for discovering novel bioactive compounds. Furthermore, it discusses the application of this technology to produce proteins and peptides as well as minimize the use of antibodies, such as antigen-binding fragment, single-chain fragment variable or single-domain antibody fragments like VHHs.

EXPERT OPINION

Advances in screening, manufacturing and humanization technologies demonstrate that phage display derived products can play a significant role in the diagnosis and treatment of disease. The effects of this technology are inevitable in the development pipeline for bringing therapeutics into the market, and this number is expected to rise significantly in the future as new advances continue to take place in display methods. Furthermore, a widespread application of this methodology is predicted in different medical technological areas, including biosensing, monitoring, molecular imaging, gene therapy, vaccine development and nanotechnology.