Aggregation of protein therapeutics enhances their immunogenicity: causes and mitigation strategies

Design Principles for Immunomodulatory Biomaterials

The immune system is imperative to the survival of all biological organisms. A functional immune system protects the organism by detecting and eliminating foreign and host aberrant molecules. Conversely, a dysfunctional immune system characterized by an overactive or weakened immune system causes life-threatening autoimmune or immunodeficiency diseases. Therefore, a critical need exists to develop technologies that regulate the immune system to ensure homeostasis or treat several diseases. Accumulating evidence shows that biomaterials─artificial materials (polymers, metals, ceramics, or engineered cells and tissues) that interact with biological systems─can trigger immune responses, offering a materials science-based strategy to modulate the immune system. This Review discusses the expanding frontiers of biomaterial-based immunomodulation, focusing on principles for designing these materials. This Review also presents examples of immunomodulatory biomaterials, which include polymers and metal- and carbon-based nanomaterials, capable of regulating the innate and adaptive immune systems.

Anti-angiogenic biomolecules in neovascular age-related macular degeneration; therapeutics and drug delivery systems

Blindness in the elderly is often caused by age-related macular degeneration (AMD). The advanced type of AMD known as neovascular AMD (nAMD) has been linked to being the predominant cause of visual impairment in these people. Multiple neovascular structures including choroidal neovascular (CNV) membranes, fluid exudation, hemorrhages, and subretinal fibrosis, are diagnostic of nAMD. These pathological alterations ultimately lead to anatomical and visual loss. It is known that vascular endothelial growth factor (VEGF), a type of proangiogenic factor, mediates the pathological process underlying nAMD. Therefore, various therapies have evolved to directly target the disease. In this review article, an attempt has been made to discuss general explanations about this disease, all common treatment methods based on anti-VEGF drugs, and the use of drug delivery systems in the treatment of AMD. Initially, the pathophysiology, angiogenesis, and different types of AMD were described. Then we described current treatments and future treatment prospects for AMD and outlined the advantages and disadvantages of each. In this context, we first examined the types of therapeutic biomolecules and anti-VEGF drugs that are used in the treatment of AMD. These biomolecules include aptamers, monoclonal antibodies, small interfering RNAs, microRNAs, peptides, fusion proteins, nanobodies, and other therapeutic biomolecules. Finally, we described drug delivery systems based on liposomes, nanomicelles, nanoemulsions, nanoparticles, cyclodextrin, dendrimers, and composite vehicles that are used in AMD therapy.

Self-assembled nanonization of fatty acid-conjugated vaccine antigen for enhanced thermal stability

The aim of this study was to evaluate the enhanced thermal stability and physicochemical properties of fattigated vaccine antigens. High molecular weight influenza hemagglutinin (Heg) was used as a model antigen because of low heat stability requiring cold chamber. Heg was conjugated with long-chain oleic acid (C18) and short-chain 3-decenoic acid (C10) to prepare fattigated Heg. Circular dichroism analysis revealed no significant changes in the three-dimensional structure post-conjugation. In the liquid state, the fattigated Heg was self-assembled into nanoparticles (NPs) due to its amphiphilic nature, with sizes of 136.27 ± 12.78 nm for oleic acid-conjugated Heg (HOC) and 88.73 ± 3.27 nm for 3-decenoic acid-conjugated Heg (HDC). Accelerated thermal stability studies at 60 °C for 7 days demonstrated that fattigated Heg exhibited higher thermal stability than Heg in various liquid or solid states. The longer-chained HOC showed better thermal stability than HDC in the liquid state, attributed to increased hydrophobic interactions during self-assembly. In bio-mimicking liquid states at 37 °C, HOC exhibited higher thermal stability than Heg. Furthermore, solid-state HOC with cryoprotectants (trehalose, mannitol, and Tween® 80) had significantly increased thermal stability due to reduced exposure of protein surface area via nanonization behavior. The current fattigation platform could be a promising strategy for developing thermostable nano vaccines of heat-labile vaccine antigens.

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

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

A Review of Recent Developments in Biopolymer Nano-Based Drug Delivery Systems with Antioxidative Properties: Insights into the Last Five Years

In recent years, biopolymer-based nano-drug delivery systems with antioxidative properties have gained significant attention in the field of pharmaceutical research. These systems offer promising strategies for targeted and controlled drug delivery while also providing antioxidant effects that can mitigate oxidative stress-related diseases. Generally, the healthcare landscape is constantly evolving, necessitating the continual development of innovative therapeutic approaches and drug delivery systems (DDSs). DDSs play a pivotal role in enhancing treatment efficacy, minimizing adverse effects, and optimizing patient compliance. Among these, nanotechnology-driven delivery approaches have garnered significant attention due to their unique properties, such as improved solubility, controlled release, and targeted delivery. Nanomaterials, including nanoparticles, nanocapsules, nanotubes, etc., offer versatile platforms for drug delivery and tissue engineering applications. Additionally, biopolymer-based DDSs hold immense promise, leveraging natural or synthetic biopolymers to encapsulate drugs and enable targeted and controlled release. These systems offer numerous advantages, including biocompatibility, biodegradability, and low immunogenicity. The utilization of polysaccharides, polynucleotides, proteins, and polyesters as biopolymer matrices further enhances the versatility and applicability of DDSs. Moreover, substances with antioxidative properties have emerged as key players in combating oxidative stress-related diseases, offering protection against cellular damage and chronic illnesses. The development of biopolymer-based nanoformulations with antioxidative properties represents a burgeoning research area, with a substantial increase in publications in recent years. This review provides a comprehensive overview of the recent developments within this area over the past five years. It discusses various biopolymer materials, fabrication techniques, stabilizers, factors influencing degradation, and drug release. Additionally, it highlights emerging trends, challenges, and prospects in this rapidly evolving field.

Fibrillation of Human Serum Albumin Differentially Affected by Asp-, Arg-, and Tyr-Capped Gold Nanoparticles

Fibrillation of proteins is associated with a number of debilitating diseases, including various neurodegenerative disorders. Prevention of the protein fibrillation process is therefore of immense importance. We investigated the effect of amino acid-capped AuNPs on the prevention of the fibrillation process of human serum albumin (HSA), a model protein. Amino acid-capped AuNPs of varying sizes and agglomeration extents were synthesized under physiological conditions. The AuNPs were characterized by their characteristic surface plasmon resonance (SPR), and their interactions with HSA were investigated through emission spectroscopy in addition to circular dichroism (CD) spectral analyses. Fluorescence lifetime imaging (FLIM) as well as transmission electron microscopy (TEM) were used to observe the fibrillar network. Thermodynamic and kinetic analyses from CD and fluorescence emission spectra provided insights into the fibrillation pathway adopted by HSA in the presence of capped AuNPs. Kinetics of the fibrillation pathway followed by ThT fluorescence emission confirmed the sigmoidal nature of the process. The highest cooperativity was observed in the case of Asp-AuNPs with HSA. This was in accordance with the ΔG value obtained from the CD spectral analyses, where Arg-AuNPs with HSA showed the highest positive ΔG value and Asp-AuNPs with HSA showed the most negative ΔG value. The study provides information about the potential use of conjugate AuNPs to monitor the fibrillation process in proteins.

Improving product quality and productivity of an antibody-based biotherapeutic using inverted frustoconical shaking bioreactors

The Chinese hamster ovarian (CHO) cells serve as a common choice in biopharmaceutical production, traditionally cultivated in stirred tank bioreactors (STRs). Nevertheless, the pursuit of improved protein quality and production output for commercial purposes demand exploration into new bioreactor types. In this context, inverted frustoconical shaking bioreactors (IFSB) present unique physical properties distinct from STRs. This study aims to compare the production processes of an antibody-based biotherapeutic in both bioreactor types, to enhance production flexibility. The findings indicate that, when compared to STRs, IFSB demonstrates the capability to produce an antibody-based biotherapeutic with either comparable or enhanced bioprocess performance and product quality. IFSB reduces shear damage to cells, enhances viable cell density (VCD), and improves cell state at a 5-L scale. Consequently, this leads to increased protein expression (3.70 g/L vs 2.56 g/L) and improved protein quality, as evidenced by a reduction in acidic variants from 27.0% to 21.5%. Scaling up the culture utilizing the Froude constant and superficial gas velocity ensures stable operation, effective mixing, and gas transfer. The IFSB maintains a high VCD and cell viability at both 50-L and 500-L scales. Product expression levels range from 3.0 to 3.6 g/L, accompanied by an improved acidic variants attribute of 20.6%-22.7%. The IFSB exhibits superior productivity and product quality, underscoring its potential for incorporation into the manufacturing process for antibody-based biotherapeutics. These results establish the foundation for IFSB to become a viable option in producing antibody-based biotherapeutics for clinical and manufacturing applications.

Unraveling the Microscopic Mechanism of Molecular Ion Interaction with Monoclonal Antibodies: Impact on Protein Aggregation

Understanding and predicting protein aggregation represents one of the major challenges in accelerating the pharmaceutical development of protein therapeutics. In addition to maintaining the solution pH, buffers influence both monoclonal antibody (mAb) aggregation in solution and the aggregation mechanisms since the latter depend on the protein charge. Molecular-level insight is necessary to understand the relationship between the buffer-mAb interaction and mAb aggregation. Here, we use all-atom molecular dynamics simulations to investigate the interaction of phosphate (Phos) and citrate (Cit) buffer ions with the Fab and Fc domains of mAb COE3. We demonstrate that Phos and Cit ions feature binding mechanisms, with the protein that are very different from those reported previously for histidine (His). These differences are reflected in distinctive ion-protein binding modes and adsorption/desorption kinetics of the buffer molecules from the mAb surface and result in dissimilar effects of these buffer species on mAb aggregation. While His shows significant affinity toward hydrophobic amino acids on the protein surface, Phos and Cit ions preferentially bind to charged amino acids. We also show that Phos and Cit anions provide bridging contacts between basic amino acids in neighboring proteins. The implications of such contacts and their connection to mAb aggregation in therapeutic formulations are discussed.

Exploring the next generation of antibody-drug conjugates

Antibody-drug conjugates (ADCs) are a promising cancer treatment modality that enables the selective delivery of highly cytotoxic payloads to tumours. However, realizing the full potential of this platform necessitates innovative molecular designs to tackle several clinical challenges such as drug resistance, tumour heterogeneity and treatment-related adverse effects. Several emerging ADC formats exist, including bispecific ADCs, conditionally active ADCs (also known as probody-drug conjugates), immune-stimulating ADCs, protein-degrader ADCs and dual-drug ADCs, and each offers unique capabilities for tackling these various challenges. For example, probody-drug conjugates can enhance tumour specificity, whereas bispecific ADCs and dual-drug ADCs can address resistance and heterogeneity with enhanced activity. The incorporation of immune-stimulating and protein-degrader ADCs, which have distinct mechanisms of action, into existing treatment strategies could enable multimodal cancer treatment. Despite the promising outlook, the importance of patient stratification and biomarker identification cannot be overstated for these emerging ADCs, as these factors are crucial to identify patients who are most likely to derive benefit. As we continue to deepen our understanding of tumour biology and refine ADC design, we will edge closer to developing truly effective and safe ADCs for patients with treatment-refractory cancers. In this Review, we highlight advances in each ADC component (the monoclonal antibody, payload, linker and conjugation chemistry) and provide more-detailed discussions on selected examples of emerging novel ADCs of each format, enabled by engineering of one or more of these components.

Reducing Immunogenicity by Design: Approaches to Minimize Immunogenicity of Monoclonal Antibodies

Monoclonal antibodies (mAbs) have transformed therapeutic strategies for various diseases. Their high specificity to target antigens makes them ideal therapeutic agents for certain diseases. However, a challenge to their application in clinical practice is their potential risk to induce unwanted immune response, termed immunogenicity. This challenge drives the continued efforts to deimmunize these protein therapeutics while maintaining their pharmacokinetic properties and therapeutic efficacy. Because mAbs hold a central position in therapeutic strategies against an array of diseases, the importance of conducting comprehensive immunogenicity risk assessment during the drug development process cannot be overstated. Such assessment necessitates the employment of in silico, in vitro, and in vivo strategies to evaluate the immunogenicity risk of mAbs. Understanding the intricacies of the mechanisms that drive mAb immunogenicity is crucial to improving their therapeutic efficacy and safety and developing the most effective strategies to determine and mitigate their immunogenic risk. This review highlights recent advances in immunogenicity prediction strategies, with a focus on protein engineering strategies used throughout development to reduce immunogenicity.

Recent advances in generative biology for biotherapeutic discovery

Generative biology combines artificial intelligence (AI), advanced life sciences technologies, and automation to revolutionize the process of designing novel biomolecules with prescribed properties, giving drug discoverers the ability to escape the limitations of biology during the design of next-generation protein therapeutics. Significant hurdles remain, namely: (i) the inherently complex nature of drug discovery, (ii) the bewildering number of promising computational and experimental techniques that have emerged in the past several years, and (iii) the limited availability of relevant protein sequence-function data for drug-like molecules. There is a need to focus on computational methods that will be most practically effective for protein drug discovery and on building experimental platforms to generate the data most appropriate for these methods. Here, we discuss recent advances in computational and experimental life sciences that are most crucial for impacting the pace and success of protein drug discovery.

Streamlining biosimilar development based on 20 years' experience

INTRODUCTION

Biosimilar clinical programs could be streamlined by prudent application of improved methodologies and knowledge accumulated over the past 20 years. This review focuses on whether complex comparative efficacy trials are routinely needed and how to achieve a more tailored approach to biosimilar development.

AREAS COVERED

Key learnings over the past 20 years are summarized. It is noted that a one size fits all approach to biosimilar development is not appropriate: biological medicines fall within a wide spectrum of complexity, with blurring at the interface between biological products and small molecules. The interrelationship between quality, potency, pharmacokinetics, pharmacology, immunogenicity, efficacy, and safety are reviewed. Current regulatory thinking is reviewed with a look into what future challenges lie ahead.

EXPERT OPINION

To tailor regulatory requirements for marketing approval of biosimilars, it is proposed that a biosimilarity report be introduced. This report would integrate quality, pharmacology, immunogenicity, efficacy and safety findings and address how the clinical program could be tailored based on the totality of evidence.

Complexing Protein-Free Botulinum Neurotoxin A Formulations: Implications of Excipients for Immunogenicity

The formation of neutralizing antibodies is a growing concern in the use of botulinum neurotoxin A (BoNT/A) as it may result in secondary treatment failure. Differences in the immunogenicity of BoNT/A formulations have been attributed to the presence of pharmacologically unnecessary bacterial components. Reportedly, the rate of antibody-mediated secondary non-response is lowest in complexing protein-free (CF) IncobotulinumtoxinA (INCO). Here, the published data and literature on the composition and properties of the three commercially available CF-BoNT/A formulations, namely, INCO, Coretox® (CORE), and DaxibotulinumtoxinA (DAXI), are reviewed to elucidate the implications for their potential immunogenicity. While all three BoNT/A formulations are free of complexing proteins and contain the core BoNT/A molecule as the active pharmaceutical ingredient, they differ in their production protocols and excipients, which may affect their immunogenicity. INCO contains only two immunologically inconspicuous excipients, namely, human serum albumin and sucrose, and has demonstrated low immunogenicity in daily practice and clinical studies for more than ten years. DAXI contains four excipients, namely, L-histidine, trehalosedihydrate, polysorbate 20, and the highly charged RTP004 peptide, of which the latter two may increase the immunogenicity of BoNT/A by introducing neo-epitopes. In early clinical studies with DAXI, antibodies against BoNT/A and RTP004 were found at low frequencies; however, the follow-up period was critically short, with a maximum of three injections. CORE contains four excipients: L-methionine, sucrose, NaCl, and polysorbate 20. Presently, no data are available on the immunogenicity of CORE in human beings. It remains to be seen whether all three CF BoNT/A formulations demonstrate the same low immunogenicity in patients over a long period of time.

QTY code designed antibodies for aggregation prevention: A structural bioinformatic and computational study

Therapeutic monoclonal antibodies are the most rapidly growing class of molecular medicine, and they are beneficial to the treatment of a broad spectrum of human diseases. However, the aggregation of antibodies during the process of manufacture, distribution, and storage poses significant challenges, potentially compromising efficacy and inducing adverse immune responses. We previously conceived a QTY (glutamine, threonine, tyrosine) code, a simple tool for enhancing protein water-solubility by systematically pairwise replacing hydrophobic residues L (leucine), V (valine)/I (isoleucine), and F (phenylalanine). The QTY code offers a promising alternative to traditional methods of controlling aggregation in integral transmembrane proteins. In this study, we designed variants of four antibodies applying the QTY code, changing only the β-sheets. Through the structure-based aggregation analysis, we found that these QTY antibody variants demonstrated significantly decreased aggregation propensity compared to their wild-type counter parts. Our results of molecular dynamics simulations showed that the design by QTY code is capable of maintaining the antigen-binding affinity and structural stability. Our structural informatic and computational study suggests that the QTY code offers a significant potential in mitigating antibody aggregation.

Comprehensive physicochemical and functional analysis of pembrolizumab based on controlled degradation studies: Impact on antigen-antibody binding

Monoclonal antibodies-based medicines are widely used in the treatment of different diseases. These medicines are very sensitive to exposure to different environmental conditions and their handling in hospitals may affect their safety and efficacy. This is the case for pembrolizumab (Keytruda®, 25 mg/mL), for which there is not yet much information on its risk behaviour associated with routine handling or unintentional mishandling. Here we performed a wider physicochemical and functional analysis of pembrolizumab medicine including controlled degradation studies: heat, freeze/thaw, agitation, accelerated light exposure and high hypertonic solution. After that, the samples were analysed by a set of analytical techniques to evaluated critical quality attributes: Far-UV CD, IT-FS, DLS, RP/UHPLC(UV)-MS, SE/UHPLC(UV), RP/UHPLC(UV)-MS/MS and ELISA. The results provide an in-depth understanding of the biochemical and biophysical properties of pembrolizumab, showing that the medicine is affected by accelerated light exposure and temperature of 60 °C, demonstrated by the detection of non-natural dimers and HMWS. Light exposure also revealed different isoform profile and increase in oxidations. Regarding functionality by means of the interaction antigen-antibody binding, all the stressors promoted a decrease in pembrolizumab capacity to bind to PD-1 receptor, although the biological activity remained still high for all of them, being 60 °C and accelerated light exposure the most affected.

Enrichment strategy and initial characterization of heterodimers enriched from a co-formulated cocktail of therapeutic antibodies against SARS-COV-2

Co-formulation of multiple drug products is an efficient and convenient approach to simultaneously deliver multiple biotherapeutics with the potentially added benefit of a synergistic therapeutic effect. However, co-formulation also increases the risk of heteromeric interactions, giving rise to unique impurities with unknown efficacy and immunogenicity. Therefore, it is critical to develop methods to evaluate the risk of heteromers as an impurity that could affect potency, efficacy, and/or immunogenicity. The most direct strategy to evaluate antibody heteromers is via specific enrichment. However, the fact that antibody heterodimers generated from the co-formulated cocktail share highly similar molar mass and size properties as homodimers natively present in each individual antibody drug product poses a unique purification challenge. Here, we report the path to successful enrichment of heterodimers from co-formulated REGEN-COVⓇ and discuss its potential impacts on drug quality.

tANCHOR fast and cost-effective cell-based immunization approach with focus on the receptor-binding domain of SARS-CoV-2

Successful induction of antibodies in model organisms like mice depends strongly on antigen design and delivery. New antigen designs for immunization are helpful for developing future therapeutic monoclonal antibodies (mAbs). One of the gold standards to induce antibodies in mice is to express and purify the antigen for vaccination. This is especially time-consuming when mAbs are needed rapidly. We closed this gap and used the display technology tetraspanin anchor to develop a reliable immunization technique without the need to purify the antigen. This technique is able to speed up the immunization step enormously and we have demonstrated that we were able to induce antibodies against different proteins with a focus on the receptor-binding domain of SARS-CoV-2 and the extracellular loop of canine cluster of differentiation 20 displayed on the surface of human cells.

Influence of pneumatic transportation on the stability of monoclonal antibodies

Pneumatic transportation systems (PTS) were recently proposed as a method to carry ready-for-injection diluted monoclonal antibodies (mAbs) from the pharmacy to the bedside of patients. This method reduces transportation time and improves the efficiency of drug distribution process. However, mAbs are highly sensitive molecules for which subtle alterations may lead to deleterious clinical effects. These alterations can be caused by various external factors such as temperature, pH, pressure, and mechanical forces that may occur during transportation. Hence, it is essential to ensure that the mAbs transported by PTS remain stable and active throughout the transportation process. This study aims to determine the safety profile of PTS to transport 11 routinely used mAbs in a clinical setting through assessment of critical quality attributes (CQA) and orthogonal analysis. Hence, we performed aggregation/degradation profiling, post-translational modifications identification using complementary mass spectrometry-based methods, along with visible and subvisible particle formation determination by light absorbance and light obscuration analysis. Altogether, these results highlight that PTS can be safely used for this purpose when air is removed from the bags during preparation.

Stabilization challenges and aggregation in protein-based therapeutics in the pharmaceutical industry

Protein-based therapeutics have revolutionized the pharmaceutical industry and become vital components in the development of future therapeutics. They offer several advantages over traditional small molecule drugs, including high affinity, potency and specificity, while demonstrating low toxicity and minimal adverse effects. However, the development and manufacturing processes of protein-based therapeutics presents challenges related to protein folding, purification, stability and immunogenicity that should be addressed. These proteins, like other biological molecules, are prone to chemical and physical instabilities. The stability of protein-based drugs throughout the entire manufacturing, storage and delivery process is essential. The occurrence of structural instability resulting from misfolding, unfolding, and modifications, as well as aggregation, poses a significant risk to the efficacy of these drugs, overshadowing their promising attributes. Gaining insight into structural alterations caused by aggregation and their impact on immunogenicity is vital for the advancement and refinement of protein therapeutics. Hence, in this review, we have discussed some features of protein aggregation during production, formulation and storage as well as stabilization strategies in protein engineering and computational methods to prevent aggregation.

Comparative Analysis of Protein Surface Hydrophobicity Maps Determined by Sparse Sampling INDUS and Spatial Aggregation Propensity

Protein surface hydrophobicity plays a central role in various biological processes such as protein folding and aggregation, as well as in the design and manufacturing of biotherapeutics. While the hydrophobicity of protein surface patches has been linked to their constituent residue hydropathies, recent research has shown that protein surface hydrophobicity is more complex and characterized by the response of water to these surfaces. In this work, we employ water density perturbations to map the surface hydrophobicity of a set of model proteins using sparse indirect umbrella sampling simulations (SSI). This technique is used to identify hydrophobic surface patches for the set of model proteins, and the results are compared to those obtained from the widely adopted spatial aggregation propensity (SAP) technique. While SAP-based calculations show agreement with SSI in some cases, there are several examples of disagreement. We identify four general classes of difference in behavior and study factors that contribute to these differences. We find that the SAP method can sometimes mask the effect of weakly nonpolar or isolated nonpolar residues that can lead to strong hydrophobic patches on the protein surface. In addition, hydrophobic patches identified by SAP can exhibit shifts in both position and strength on the SSI map. Our results demonstrate that the combination of topography and chemical context controls the hydrophobicity of a given patch above and beyond the intrinsic polarity of the residues present on the patch surface. The availability of more accurate protein hydrophobicity maps in concert with new classes of hydrophobic molecular descriptors may create significant opportunities for in silico prediction of protein behavior for a range of applications, such as protein design, biomanufacturability, and downstream bioprocessing.

Experimental procedures to investigate fibrillation of proteins

The unwanted phenomenon of protein fibrillation is observed in vivo and during therapeutic protein development in the industry. Protein aggregation is associated with various degenerative disorders and might induce immune-related challenges post-administration of biopharmaceutics. A pipeline for early detection, identification, and removal of pre-formed fibrils is needed to improve the quality, efficacy, and effectiveness of the formulation. Protein fibril formation is accompanied by unfolding, secondary structural changes and the formation of larger aggregates. However, most detection processes come with extensive sample preparation steps and inefficient repeatability, incurring a financial burden on research. The current article summarizes and critically discusses six simple yet powerful methods to detect aggregation phenomena in the line of detecting fibrillar aggregates in heat-induced bovine serum albumin protein. Comparing the native and heat-induced protein samples would provide insights about aggregates. Easy, inexpensive and optimized protocols for detecting the fibrillation of proteins are explained. The procedures mentioned here detected the appearance of β-sheet-rich fibrils in the heat-induced protein sample. The aggregation is characterized by enhanced thioflavin-T fluorescence, alteration in the intrinsic fluorescence, decrease in helicity and subsequent increase in β-sheet and appearance of particles with larger hydrodynamic diameters. •This article summarizes various analytical techniques to easily characterize the fibrillation of proteins.•Various techniques to detect the formation of β-sheet rich structures, changes in the secondary structures and size of aggregates have been discussed.•The stated methodologies are validated on a model protein, albumin.

Protein-based Nanoparticles: From Drug Delivery to Imaging, Nanocatalysis and Protein Therapy

Proteins and enzymes are versatile biomaterials for a wide range of medical applications due to their high specificity for receptors and substrates, high degradability, low toxicity, and overall good biocompatibility. Protein nanoparticles are formed by the arrangement of several native or modified proteins into nanometer-sized assemblies. In this review, we will focus on artificial nanoparticle systems, where proteins are the main structural element and not just an encapsulated payload. While under natural conditions, only certain proteins form defined aggregates and nanoparticles, chemical modifications or a change in the physical environment can further extend the pool of available building blocks. This allows the assembly of many globular proteins and even enzymes. These advances in preparation methods led to the emergence of new generations of nanosystems that extend beyond transport vehicles to diverse applications, from multifunctional drug delivery to imaging, nanocatalysis and protein therapy.

Characterization and root cause analysis of immunogenicity to pasotuxizumab (AMG 212), a prostate-specific membrane antigen-targeting bispecific T-cell engager therapy

Introduction

In oncology, anti-drug antibody (ADA) development that significantly curtails response durability has not historically risen to a level of concern. The relevance and attention ascribed to ADAs in oncology clinical studies have therefore been limited, and the extant literature on this subject scarce. In recent years, T cell engagers have gained preeminence within the prolific field of cancer immunotherapy. These drugs whose mode of action is expected to potently stimulate anti-tumor immunity, may potentially induce ADAs as an unintended corollary due to an overall augmentation of the immune response. ADA formation is therefore emerging as an important determinant in the successful clinical development of such biologics.

Methods

Here we describe the immunogenicity and its impact observed to pasotuxizumab (AMG 212), a prostate-specific membrane antigen (PSMA)-targeting bispecific T cell engager (BiTE®) molecule in NCT01723475, a first-in-human (FIH), multicenter, dose-escalation study in patients with metastatic castration-resistant prostate cancer (mCRPC). To explain the disparity in ADA incidence observed between the SC and CIV arms of the study, we interrogated other patient and product-specific factors that may have explained the difference beyond the route of administration.

Results

Treatment-emergent ADAs (TE-ADA) developed in all subjects treated with at least 1 cycle of AMG 212 in the subcutaneous (SC) arm. These ADAs were neutralizing and resulted in profound exposure loss that was associated with contemporaneous reversal of initial Prostate Surface Antigen (PSA) responses, curtailing durability of PSA response in patients. Pivoting from SC to a continuous intravenous (CIV) administration route remarkably yielded no subjects developing ADA to AMG 212. Through a series of stepwise functional assays, our investigation revealed that alongside a more historically immunogenic route of administration, non-tolerant T cell epitopes within the AMG 212 amino acid sequence were likely driving the high-titer, sustained ADA response observed in the SC arm.

Discussion

These mechanistic insights into the AMG 212 ADA response underscore the importance of performing preclinical immunogenicity risk evaluation as well as advocate for continuous iteration to better our biologics.

Zwitterionic Polymer: A New Paradigm for Protein Conjugation beyond PEG

To render protein drugs more suitable for clinical treatment, PEGylation has been widely used to ameliorate their inherent deficiencies, such as poor stability, rapid elimination in the bloodstream, and high immunogenicity. While increasingly PEGylated protein drugs have been approved by the FDA, the non-degradability of PEG and the emergence of anti-PEG antibodies after injection raise concerns about their cumulative chronic toxicity and long-term therapeutic efficacy. Zwitterionic polymer, with a unique structure containing equal amounts of positively charged and negatively charged groups, shows a different hydration behavior to PEG, which may be a superior PEG alternative for protein conjugation. In this concept review, a series of features beyond that of PEGylated protein exhibited by protein-zwitterionic polymer conjugate are discussed and some suggestions are presented for their future direction.

Understanding and controlling the molecular mechanisms of protein aggregation in mAb therapeutics

In antibody development and manufacturing, protein aggregation is a common challenge that can lead to serious efficacy and safety issues. To mitigate this problem, it is important to investigate its molecular origins. This review discusses (1) our current molecular understanding and theoretical models of antibody aggregation, (2) how various stress conditions related to antibody upstream and downstream bioprocesses can trigger aggregation, and (3) current mitigation strategies employed towards inhibiting aggregation. We discuss the relevance of the aggregation phenomenon in the context of novel antibody modalities and highlight how in silico approaches can be exploited to mitigate it.

Glycosylation shapes the efficacy and safety of diverse protein, gene and cell therapies

Over recent decades, therapeutic proteins have had widespread success in treating a myriad of diseases. Glycosylation, a near universal feature of this class of drugs, is a critical quality attribute that significantly influences the physical properties, safety profile and biological activity of therapeutic proteins. Optimizing protein glycosylation, therefore, offers an important avenue to developing more efficacious therapies. In this review, we discuss specific examples of how variations in glycan structure and glycoengineering impacts the stability, safety, and clinical efficacy of protein-based drugs that are already in the market as well as those that are still in preclinical development. We also highlight the impact of glycosylation on next generation biologics such as T cell-based cancer therapy and gene therapy.

Discovery and Characterization of an Acid-Labile Serine-Lysine Cross-Link in Antibody High-Molecular-Weight Species Using a Multipronged Mass Spectrometry Approach

Characterizing the cross-links responsible for the covalent high-molecular-weight (HMW) species in therapeutic monoclonal antibodies (mAbs) is of great importance as it not only provides a framework for risk assessment but also offers insights for process improvement. However, owing to the complexity and low abundance, identification of novel and unknown cross-links in mAb products can be very challenging. Here, applying a multipronged MS-based approach, we report the discovery of a novel covalent cross-link formed via an imine bond between lysine and serine residues. In particular, this Ser-Lys cross-link was found to be acid-labile and can be easily overlooked by conventional LC-MS techniques operated at low pH. It is worth noting that although imine-based cross-link has been previously reported in collagen protein cross-linking, this is the first time that a Ser-Lys cross-link has been found in a mAb product that contributes to covalent HMW species formation.

Target-independent Immune-cell Activation by Aggregates of T Cell-redirecting Bispecific Antibodies

T cell-redirecting bispecific antibodies (bsAbs) have been under development as a new class of biotherapeutics for cancer immunotherapy. T cell-redirecting bsAbs simultaneously bind tumor-associated antigens on tumor cells and CD3 on T cells, resulting in T cell-mediated cytotoxicity against tumor cells. In this study, we prepared a tandem scFv-typed bsAb targeting HER2 and CD3 (HER2-CD3), and evaluated the impact of aggregation of HER2-CD3 on the in vitro immunotoxicity. A cell-based assay using CD3-expressing reporter cells revealed that the aggregates of HER2-CD3 directly activated CD3-expressing immune cells in the absence of target antigen (HER2)-expressing cells. Comparison of the aggregates generated under various stress conditions indicated the possibility that insoluble protein particles, which were detected by qLD analysis and contained non-denatured functional domains, contributed to the activation of CD3-expressing immune cells. In addition, HER2-CD3 aggregates stimulated hPBMCs and strongly induced the secretion of inflammatory cytokines and chemokines. The cytokine/chemokine-release profiles suggested that the aggregates could induce inflammatory responses not only by CD3-mediated T cell activation but also by other immune cell activations. These results indicated the potential risk of aggregation of T cell-redirecting bsAbs, which could induce unwanted immune cell activation and inflammation and thereby immune-mediated adverse reactions.

In vitro and in vivo studies of plant-produced Atezolizumab as a potential immunotherapeutic antibody

Immune checkpoint inhibitors are a well-known class of immunotherapeutic drugs that have been used for effective treatment of several cancers. Atezolizumab (Tecentriq) was the first antibody to target immune checkpoint PD-L1 and is now among the most commonly used anticancer therapies. However, this anti-PD-L1 antibody is produced in mammalian cells with high manufacturing costs, limiting cancer patients' access to the antibody treatment. Plant expression system is another platform that can be utilized, as they can synthesize complex glycoproteins, are rapidly scalable, and relatively cost-efficient. Herein, Atezolizumab was transiently produced in Nicotiana benthamiana and demonstrated high expression level within 4-6 days post-infiltration. After purification by affinity chromatography, the purified plant-produced Atezolizumab was compared to Tecentriq and showed the absence of glycosylation. Furthermore, the plant-produced Atezolizumab could bind to PD-L1 with comparable affinity to Tecentriq in ELISA. The tumor growth inhibitory activity of plant-produced Atezolizumab in mice was also found to be similar to that of Tecentriq. These findings confirm the plant's capability to serve as an efficient production platform for immunotherapeutic antibodies and suggest that it could be used to alleviate the cost of existing anticancer products.

Probing the Biosafety of Implantable Artificial Secretory Granules for the Sustained Release of Bioactive Proteins

Among bio-inspired protein materials, secretory protein microparticles are of clinical interest as self-contained, slow protein delivery platforms that mimic secretory granules of the human endocrine system, in which the protein is both the drug and the scaffold. Upon subcutaneous injection, their progressive disintegration results in the sustained release of the building block polypeptides, which reach the bloodstream for systemic distribution and subsequent biological effects. Such entities are easily fabricated in vitro by Zn-assisted cross-molecular coordination of histidine residues. Using cationic Zn for the assembly of selected pure protein species and in the absence of any heterologous holding material, these granules are expected to be nontoxic and therefore adequate for different clinical uses. However, such presumed biosafety has not been so far confirmed and the potential protein dosage threshold not probed yet. By selecting the receptor binding domain (RBD) from the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein as a model protein and using a mouse lab model, we have explored the toxicity of RBD-made secretory granules at increasing doses up to ∼100 mg/kg of animal weight. By monitoring body weight and biochemical blood markers and through the histological scrutiny of main tissues and organs, we have not observed systemic toxicity. Otherwise, the bioavailability of the material was demonstrated by the induction of specific antibody responses. The presented data confirm the intrinsic biosafety of artificial secretory granules made by recombinant proteins and prompt their further clinical development as self-contained and dynamic protein reservoirs.

Characterizing Silicone Oil-Induced Protein Aggregation with Stimulated Raman Scattering Imaging

Particles in biopharmaceutical products present high risks due to their detrimental impacts on product quality and safety. Identification and quantification of particles in drug products are important to understand particle formation mechanisms, which can help develop control strategies for particle formation during the formulation development and manufacturing process. However, existing analytical techniques such as microflow imaging and light obscuration measurement lack the sensitivity and resolution to detect particles with sizes smaller than 2 μm. More importantly, these techniques are not able to provide chemical information to determine particle composition. In this work, we overcome these challenges by applying the stimulated Raman scattering (SRS) microscopy technique to monitor the C-H Raman stretching modes of the proteinaceous particles and silicone oil droplets formed in the prefilled syringe barrel. By comparing the relative signal intensity and spectral features of each component, most particles can be classified as protein-silicone oil aggregates. We further show that morphological features are poor indicators of particle composition. Our method has the capability to quantify aggregation in protein therapeutics with chemical and spatial information in a label-free manner, potentially allowing high throughput screening or investigation of aggregation mechanisms.

Strategies for overcoming protein and peptide instability in biodegradable drug delivery systems

The global pharmaceutical market has recently shifted its focus from small molecule drugs to peptide, protein, and nucleic acid drugs, which now comprise a majority of the top-selling pharmaceutical products on the market. Although these biologics often offer improved drug specificity, new mechanisms of action, and/or enhanced efficacy, they also present new challenges, including an increased potential for degradation and a need for frequent administration via more invasive administration routes, which can limit patient access, patient adherence, and ultimately the clinical impact of these drugs. Controlled-release systems have the potential to mitigate these challenges by offering superior control over in vivo drug levels, localizing these drugs to tissues of interest (e.g., tumors), and reducing administration frequency. Unfortunately, adapting controlled-release devices to release biologics has proven difficult due to the poor stability of biologics. In this review, we summarize the current state of controlled-release peptides and proteins, discuss existing techniques used to stabilize these drugs through encapsulation, storage, and in vivo release, and provide perspective on the most promising opportunities for the clinical translation of controlled-release peptides and proteins.

Oligomerization and Adjuvant Activity of Peptides Derived from the VirB4-like ATPase of Clostridioides difficile

In a previous study, we demonstrated that the Clostridioides difficile VirB4-like ATPase forms oligomers in vitro. In the current investigation, to study the observed phenomenon in more detail, we prepared a library of VirB4-derived peptides (delVirB4s) fused to a carrier maltose-binding protein (MBP). Using gel chromatography and polyacrylamide gel electrophoresis, we found a set of overlapping fragments that contribute most significantly to protein aggregation, which were represented as water-soluble oligomers with molecular masses ranging from ~300 kD to several megadaltons. Membrane filtration experiments, sucrose gradient ultracentrifugation, and dynamic light scattering measurements indicated the size of the soluble complex to be 15-100 nm. It was sufficiently stable to withstand treatment with 1 M urea; however, it dissociated in a 6 M urea solution. As shown by the changes in GFP fluorescence and the circular dichroism spectra, the attachment of the delVirB4 peptide significantly altered the structure of the partner MBP. The immunization of mice with the hybrid consisting of the selected VirB4-derived peptide and MBP, GST, or GFP resulted in increased production of specific antibodies compared to the peptide-free carrier proteins, suggesting significant adjuvant activity of the VirB4 fragment. This feature could be useful for the development of new vaccines, especially in the case of "weak" antigens that are unable to elicit a strong immune response by themselves.

Long-term effects of immunotherapy with a brain penetrating Aβ antibody in a mouse model of Alzheimer's disease

BACKGROUND

Brain-directed immunotherapy is a promising strategy to target amyloid-β (Aβ) deposits in Alzheimer's disease (AD). In the present study, we compared the therapeutic efficacy of the Aβ protofibril targeting antibody RmAb158 with its bispecific variant RmAb158-scFv8D3, which enters the brain by transferrin receptor-mediated transcytosis.

METHODS

App^NL-G-F knock-in mice received RmAb158, RmAb158-scFv8D3, or PBS in three treatment regimens. First, to assess the acute therapeutic effect, a single antibody dose was given to 5 months old App^NL-G-F mice, with evaluation after 3 days. Second, to assess the antibodies' ability to halt the progression of Aβ pathology, 3 months old App^NL-G-F mice received three doses during a week, with evaluation after 2 months. Reduction of RmAb158-scFv8D3 immunogenicity was explored by introducing mutations in the antibody or by depletion of CD4⁺ T cells. Third, to study the effects of chronic treatment, 7-month-old App^NL-G-F mice were CD4⁺ T cell depleted and treated with weekly antibody injections for 8 weeks, including a final diagnostic dose of [¹²⁵I]RmAb158-scFv8D3, to determine its brain uptake ex vivo. Soluble Aβ aggregates and total Aβ42 were quantified with ELISA and immunostaining.

RESULTS

Neither RmAb158-scFv8D3 nor RmAb158 reduced soluble Aβ protofibrils or insoluble Aβ1-42 after a single injection treatment. After three successive injections, Aβ1-42 was reduced in mice treated with RmAb158, with a similar trend in RmAb158-scFv8D3-treated mice. Bispecific antibody immunogenicity was somewhat reduced by directed mutations, but CD4⁺ T cell depletion was used for long-term therapy. CD4⁺ T cell-depleted mice, chronically treated with RmAb158-scFv8D3, showed a dose-dependent increase in blood concentration of the diagnostic [¹²⁵I]RmAb158-scFv8D3, while concentration was low in plasma and brain. Chronic treatment did not affect soluble Aβ aggregates, but a reduction in total Aβ42 was seen in the cortex of mice treated with both antibodies.

CONCLUSIONS

Both RmAb158 and its bispecific variant RmAb158-scFv8D3 achieved positive effects of long-term treatment. Despite its ability to efficiently enter the brain, the benefit of using the bispecific antibody in chronic treatment was limited by its reduced plasma exposure, which may be a result of interactions with TfR or the immune system. Future research will focus in new antibody formats to further improve Aβ immunotherapy.

Automated optimisation of solubility and conformational stability of antibodies and proteins

Biologics, such as antibodies and enzymes, are crucial in research, biotechnology, diagnostics, and therapeutics. Often, biologics with suitable functionality are discovered, but their development is impeded by developability issues. Stability and solubility are key biophysical traits underpinning developability potential, as they determine aggregation, correlate with production yield and poly-specificity, and are essential to access parenteral and oral delivery. While advances for the optimisation of individual traits have been made, the co-optimization of multiple traits remains highly problematic and time-consuming, as mutations that improve one property often negatively impact others. In this work, we introduce a fully automated computational strategy for the simultaneous optimisation of conformational stability and solubility, which we experimentally validate on six antibodies, including two approved therapeutics. Our results on 42 designs demonstrate that the computational procedure is highly effective at improving developability potential, while not affecting antigen-binding. We make the method available as a webserver at www-cohsoftware.ch.cam.ac.uk.

Design of self-assembled glycopolymeric zwitterionic micelles as removable protein stabilizing agents

Developing stabilizers that protect proteins from denaturation under stress, and are easy to remove from solutions, is a challenge in protein therapeutics. In this study, micelles made of trehalose, a zwitterionic polymer (poly-sulfobetaine; poly-SPB), and polycaprolactone (PCL) were synthesized by a one-pot reversible addition-fragmentation chain-transfer (RAFT) polymerization reaction. The micelles protect lactate dehydrogenase (LDH) and human insulin from denaturation due to stresses like thermal incubation and freezing, and help them retain higher-order structures. Importantly, the protected proteins are readily isolated from the micelles by ultracentrifugation, with over 90% recovery, and almost all enzymatic activity is retained. This suggests the great potential of poly-SPB-based micelles for use in applications requiring protection and removal as required. The micelles may also be used to effectively stabilize protein-based vaccines and drugs.

The handling of biopharmaceuticals used in home-based therapy for cancer patients

BACKGROUND

Due to their low bioavailability, biopharmaceuticals are typically administered via injection or infusion in a hospital setting. Home-based therapy could be a valuable alternative for cancer patients. However, when exposed to stressors, such as high or low temperatures, particles can form in the biopharmaceutical solution, compromising the safety and efficacy of the biopharmaceutical.

AIM

This research investigated current practises with ready-to-administer biopharmaceuticals to determine if it is possible to offer cancer patients home-based therapy with monoclonal antibodies.

METHODS

First, a questionnaire was conducted with the survey tool Survalyzer among Amsterdam UMC patients receiving immunoglobulins at home. Secondly, a web-based questionnaire (Survalyzer) was sent to pharmacists throughout Europe with a home-based therapy programme in place.

RESULTS

The patient questionnaire (n = 52) showed that the biopharmaceutical is stored outside the recommended temperature range by 38% of the patients. Additionally, 17% of the patients do not recall getting any information on how to store their biopharmaceuticals, and 23% would like more information on the subject. Furthermore, the questionnaire amongst pharmacists (n = 21) showed that there is a lack of resources and logistical challenges when home-based therapy is applied to biopharmaceuticals used in cancer therapy.

CONCLUSION

Home-based therapy with monoclonal antibodies for cancer patients is challenging to implement.

A proteome scale study reveals how plastic surfaces and agitation promote protein aggregation

Protein aggregation in biotherapeutics can reduce their activity and effectiveness. It may also promote immune reactions responsible for severe adverse effects. The impact of plastic materials on protein destabilization is not totally understood. Here, we propose to deconvolve the effects of material surface, air/liquid interface, and agitation to decipher their respective role in protein destabilization and aggregation. We analyzed the effect of polypropylene, TEFLON, glass and LOBIND surfaces on the stability of purified proteins (bovine serum albumin, hemoglobin and α-synuclein) and on a cell extract composed of 6000 soluble proteins during agitation (P = 0.1-1.2 W/kg). Proteomic analysis revealed that chaperonins, intrinsically disordered proteins and ribosomes were more sensitive to the combined effects of material surfaces and agitation while small metabolic oligomers could be protected in the same conditions. Protein loss observations coupled to Raman microscopy, dynamic light scattering and proteomic allowed us to propose a mechanistic model of protein destabilization by plastics. Our results suggest that protein loss is not primarily due to the nucleation of small aggregates in solution, but to the destabilization of proteins exposed to material surfaces and their subsequent aggregation at the sheared air/liquid interface, an effect that cannot be prevented by using LOBIND tubes. A guidance can be established on how to minimize these adverse effects. Remove one of the components of this combined stress - material, air (even partially), or agitation - and proteins will be preserved.

Unique structure of ozoralizumab, a trivalent anti-TNFα NANOBODY® compound, offers the potential advantage of mitigating the risk of immune complex-induced inflammation

Biologics have become an important component of treatment strategies for a variety of diseases, but the immunogenicity of large immune complexes (ICs) and aggregates of biologics may increase risk of adverse events is a concern for biologics and it remains unclear whether large ICs consisting of intrinsic antigen and therapeutic antibodies are actually involved in acute local inflammation such as injection site reaction (ISR). Ozoralizumab is a trivalent, bispecific NANOBODY^® compound that differs structurally from IgGs. Treatment with ozoralizumab has been shown to provide beneficial effects in the treatment of rheumatoid arthritis (RA) comparable to those obtained with other TNFα inhibitors. Very few ISRs (2%) have been reported after ozoralizumab administration, and the drug has been shown to have acceptable safety and tolerability. In this study, in order to elucidate the mechanism underlying the reduced incidence of ISRs associated with ozoralizumab administration, we investigated the stoichiometry of two TNFα inhibitors (ozoralizumab and adalimumab, an anti-TNFα IgG) ICs and the induction by these drugs of Fcγ receptor (FcγR)-mediated immune responses on neutrophils. Ozoralizumab-TNFα ICs are smaller than adalimumab-TNFα ICs and lack an Fc portion, thus mitigating FcγR-mediated immune responses on neutrophils. We also developed a model of anti-TNFα antibody-TNFα IC-induced subcutaneous inflammation and found that ozoralizumab-TNFα ICs do not induce any significant inflammation at injection sites. The results of our studies suggest that ozoralizumab is a promising candidate for the treatment of RA that entails a lower risk of the IC-mediated immune cell activation that leads to unwanted immune responses.

Molecular Bases of Protein Antigenicity and Determinants of Immunogenicity, Anergy, and Mitogenicity

BACKGROUND

The immune system is able to recognize substances that originate from inside or outside the body and are potentially harmful. Foreign substances that bind to immune system components exhibit antigenicity and are defined as antigens. The antigens exhibiting immunogenicity can induce innate or adaptive immune responses and give rise to humoral or cell-mediated immunity. The antigens exhibiting mitogenicity can cross-link cell membrane receptors on B and T lymphocytes leading to cell proliferation. All antigens vary greatly in physicochemical features such as biochemical nature, structural complexity, molecular size, foreignness, solubility, and so on.

OBJECTIVE

Thus, this review aims to describe the molecular bases of protein-antigenicity and those molecular bases that lead to an immune response, lymphocyte proliferation, or unresponsiveness.

CONCLUSION

The epitopes of an antigen are located in surface areas; they are about 880-3,300 Da in size. They are protein, carbohydrate, or lipid in nature. Soluble antigens are smaller than 1 nm and are endocytosed less efficiently than particulate antigens. The more the structural complexity of an antigen increases, the more the antigenicity increases due to the number and variety of epitopes. The smallest immunogens are about 4,000-10,000 Da in size. The more phylogenetically distant immunogens are from the immunogen-recipient, the more immunogenicity increases. Antigens that are immunogens can trigger an innate or adaptive immune response. The innate response is induced by antigens that are pathogen-associated molecular patterns. Exogenous antigens, T Dependent or T Independent, induce humoral immunogenicity. TD protein-antigens require two epitopes, one sequential and one conformational to induce antibodies, whereas, TI non-protein-antigens require only one conformational epitope to induce low-affinity antibodies. Endogenous protein antigens require only one sequential epitope to induce cell-mediated immunogenicity.

High-Throughput Counting and Sizing of Therapeutic Protein Aggregates in the Nanometer Size Range by Nano-Flow Cytometry

Protein aggregation is one of the greatest challenges in biopharmaceuticals as it could decrease therapeutic efficacy, induce immunogenicity, and reduce shelf life of protein drugs. However, there lacks high-throughput methods than can count and size protein aggregates in the nanometer size range, especially for those smaller than 100 nm. Employing a laboratory-built nano-flow cytometer (nFCM) that enables light scattering detection of single silica nanoparticles as small as 24 nm with sizing resolution and accuracy comparable to those of electron microscopy, here, we report a new benchmark to analyze single protein aggregates as small as 40 nm. With an analysis rate of up to 10,000 particles/min, the size distribution and particle concentration of nanometer protein aggregates can be acquired in 2-3 min. Employing heat-induced aggregation of bovine serum albumin (BSA) at high concentrations as the model system, effects of different categories of excipients, including sugars, polyols, salts, and amino acids on the inhibition of protein aggregation were investigated. Strikingly enough, as high as 10¹⁰ to 10¹² particles/mL of protein aggregates were observed in the size range of 40 to 200 nm for therapeutic proteins of human serum albumin injection, reconstituted recombinant human interieukin-2 solution, and human immunoglobulin injection. nFCM opens a new avenue to count and size nanometer protein aggregates, suggesting its future usability in the quality assessment and formulation promotion of therapeutic proteins.

Instability Challenges and Stabilization Strategies of Pharmaceutical Proteins

Maintaining the structure of protein and peptide drugs has become one of the most important goals of scientists in recent decades. Cold and thermal denaturation conditions, lyophilization and freeze drying, different pH conditions, concentrations, ionic strength, environmental agitation, the interaction between the surface of liquid and air as well as liquid and solid, and even the architectural structure of storage containers are among the factors that affect the stability of these therapeutic biomacromolecules. The use of genetic engineering, side-directed mutagenesis, fusion strategies, solvent engineering, the addition of various preservatives, surfactants, and additives are some of the solutions to overcome these problems. This article will discuss the types of stress that lead to instabilities of different proteins used in pharmaceutics including regulatory proteins, antibodies, and antibody-drug conjugates, and then all the methods for fighting these stresses will be reviewed. New and existing analytical methods that are used to detect the instabilities, mainly changes in their primary and higher order structures, are briefly summarized.

Pre-Clinical In-Vitro Studies on Parameters Governing Immune Complex Formation

The success of biotherapeutics is often challenged by the undesirable events of immunogenicity in patients, characterized by the formation of anti-drug antibodies (ADA). Under specific conditions, the ADAs recognizing the biotherapeutic can trigger the formation of immune complexes (ICs), followed by cascades of subsequent effects on various cell types. Hereby, the connection between the characteristics of ICs and their downstream impact is still not well understood. Factors governing the formation of ICs and the characteristics of these IC species were assessed systematically in vitro. Classic analytical methodologies such as SEC-MALS and SV-AUC, and the state-of-the-art technology mass photometry were applied for the characterization. The study demonstrates a clear interplay between (1) the absolute concentration of the involved components, (2) their molar ratios, (3) structural features of the biologic, (4) and of its endogenous target. This surrogate study design and the associated analytical tool-box is readily applicable to most biotherapeutics and provides valuable insights into mechanisms of IC formation prior to FIH studies. The applicability is versatile—from the detection of candidates with immunogenicity risks during developability assessment to evaluation of the impact of degraded or post-translationally modified biotherapeutics on the formation of ICs.

Molecular Docking, Dynamics, and WaterSwap Analysis to Identify Anti-aggregating Agents of Insulin and IFN-β

There are several challenges in the development, and formulation of biologics, particularly concerning their physical stabilities. The self-assembly of peptides like human insulin and interferon beta (IFN-β) has potential to form aggregates in pharmaceutical formulation. Therefore, it is a significant problem in the manufacturing, storage, and delivery of insulin and IFN-β formulations. Amino acids as aggregation suppressing additives have been used to stabilize proteins during manufacturing and storage. Several changes to the B chain's C-terminus have been proposed in an attempt to improve insulin formulation. The core segments of the A and B chains (SLYQLENY and LVEALYLV) have recently been identified as sheet-forming areas, and their microcrystalline structures have been exploited to construct a high-resolution insulin amyloid fibril model. Here, we have chosen twenty-one amino acids to develop as additives in rendering the insulin and IFN-β aggregations. Thereafter, integrated molecular docking studies of single layer monomers of full-length insulin and IFN-β have been performed to identify structural elements (amino acids) that can act as disaggregating agents. The stability of the best-docked amino acid complexes was judged using molecular dynamics studies. Finally, phenylalanine was identified as a disaggregation agent for insulin, and lysine, tyrosine, phenylalanine, and tryptophan were identified as disaggregation agents for IFN-β from the molecular dynamics study. These findings may open a novel proposal to explore further in vitro studies to increase the stability of the insulin and IFN-β formulation.

US FDA-approved therapeutic antibodies with high-concentration formulation: summaries and perspectives

Thirty four (34) of the total US FDA approved 103 therapeutic antibody drugs, accounts for one third of the total approved mAbs, are formulated with high protein concentration (100 mg/mL or above) which are the focus of this article. The highest protein concentration of these approved mAbs is 200 mg/mL. The dominant administration route is subcutaneous (76%). Our analysis indicates that it may be rational to implement a platform formulation containing polysorbate, histidine and sucrose to accelerate high concentration formulation development for antibody drugs. Since 2015, the FDA approval numbers are significantly increased which account for 76% of the total approval numbers, i.e., 26 out of 34 highly concentrated antibodies. Thus, we believe that the high concentration formulations of antibody drugs will be the future trend of therapeutic antibody formulation development, regardless of the challenges of highly concentrated protein formulations.

Facile Synthesis of Peptide-Conjugated Gold Nanoclusters with Different Lengths

The synthesis of ultra-small gold nanoclusters (Au NCs) with sizes down to 2 nm has received increasing interest due to their unique optical and electronic properties. Like many peptide-coated gold nanospheres synthesized before, modified gold nanoclusters with peptide conjugation are potentially significant in biomedical and catalytic fields. Here, we explore whether such small-sized gold nanoclusters can be conjugated with peptides also and characterize them using atomic force microscopy. Using a long and flexible elastin-like polypeptide (ELP)₂₀ as the conjugated peptide, (ELP)₂₀-Au NCs was successfully synthesized via a one-pot synthesis method. The unique optical and electronic properties of gold nanoclusters are still preserved, while a much larger size was obtained as expected due to the peptide conjugation. In addition, a short and rigid peptide (EAAAK)₃ was conjugated to the gold nanoclusters. Their Yong’s modulus was characterized using atomic force microscopy (AFM). Moreover, the coated peptide on the nanoclusters was pulled using AFM-based single molecule-force spectroscopy (SMFS), showing expected properties as one of the first force spectroscopy experiments on peptide-coated nanoclusters. Our results pave the way for further modification of nanoclusters based on the conjugated peptides and show a new method to characterize these materials using AFM-SMFS.