Use of In Vitro Assays to Assess Immunogenicity Risk of Antibody-Based Biotherapeutics

Immunogenicity Risk Assessment of Process-Related Impurities in An Engineered T Cell Receptor Cellular Product

Cell therapies such as genetically modified T cells have emerged as a promising and viable treatment for hematologic cancers and are being aggressively pursued for a wide range of diseases and conditions that were previously difficult to treat or had no cure. The process development requires genetic modifications to T cells to express a receptor (engineered T cell receptor (eTCR)) of specific binding qualities to the desired target. Protein reagents utilized during the cell therapy manufacturing process, to facilitate these genetic modifications, are often present as process-related impurities at residual levels in the final drug product and can represent a potential immunogenicity risk upon infusion. This manuscript presents a framework for the qualification of an assay for assessing the immunogenicity risk of AA6 and Cas9 residuals. The same framework applies for other residuals; however, AAV6 and Cas9 were selected as they were residuals from the manufacturing of an engineered T cell receptor cellular product in development. The manuscript: 1) elucidates theoretical risks, 2) summarizes analytical data collected during process development, 3) describes the qualification of an in vitro human PBMC cytokine release assay to assess immunogenicity risk from cellular product associated process residuals; 4) identifies a multiplexed inflammatory innate and adaptive cytokine panel with pre-defined criteria using relevant positive controls; and 5) discusses qualification challenges and potential solutions for establishing meaningful thresholds. The assessment is not only relevant to establishing safe exposure levels of these residuals but also in guiding risk assessment and CMC strategy during the conduct of clinical trials.

A Human Skin Explant Test as a Novel In Vitro Assay for the Detection of Skin Sensitization to Aggregated Monoclonal Antibodies

Introduction: Monoclonal antibodies (mAbs) are important therapeutics. However, the enhanced potential for aggregation has become a critical quality parameter during the production of mAbs. Furthermore, mAb aggregation may also present a potential health risk in a clinical setting during the administration of mAb therapeutics to patients. While the extent of immunotoxicity in patient populations is uncertain, reports show it can lead to immune responses via cell activation and cytokine release. In this study, an autologous in vitro skin test designed to predict adverse immune events, including skin sensitization, was used as a novel assay for the assessment of immunotoxicity caused by mAb aggregation. Material and Methods: Aggregation of mAbs was induced by a heat stress protocol, followed by characterization of protein content by analytical ultra-centrifugation and transmission electron microscopy, revealing a 4% aggregation level of total protein content. Immunotoxicity and potential skin sensitization caused by the aggregates, were then tested in a skin explant assay. Results: Aggregated Herceptin and Rituximab caused skin sensitization, as shown by histopathological damage (grade II-III positive response) together with positive staining for Heat Shock Protein 70 (HSP70). Changes in T cell proliferation were not observed. Cytokine analysis revealed a significant increase of IL-10 for the most extreme condition of aggregation (65 °C at pH3) and a trend for an overall increase of IFN-γ, especially in response to Rituximab. Conclusions: The skin explant assay demonstrated that aggregated mAbs showed adverse immune reactions, as demonstrated as skin sensitization, with histopathological grades II-III. The assay may, therefore, be a novel tool for assessing immunotoxicity and skin sensitization caused by mAb aggregation.

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

BACKGROUND AND PURPOSE

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

METHODS AND RESULTS

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

CONCLUSION

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

Phase 1, first-in-human study of TYRP1-TCB (RO7293583), a novel TYRP1-targeting CD3 T-cell engager, in metastatic melanoma: active drug monitoring to assess the impact of immune response on drug exposure

Introduction

Although checkpoint inhibitors (CPIs) have improved outcomes for patients with metastatic melanoma, those progressing on CPIs have limited therapeutic options. To address this unmet need and overcome CPI resistance mechanisms, novel immunotherapies, such as T-cell engaging agents, are being developed. The use of these agents has sometimes been limited by the immune response mounted against them in the form of anti-drug antibodies (ADAs), which is challenging to predict preclinically and can lead to neutralization of the drug and loss of efficacy.

Methods

TYRP1-TCB (RO7293583; RG6232) is a T-cell engaging bispecific (TCB) antibody that targets tyrosinase-related protein 1 (TYRP1), which is expressed in many melanomas, thereby directing T cells to kill TYRP1-expressing tumor cells. Preclinical studies show TYRP1-TCB to have potent anti-tumor activity. This first-in-human (FIH) phase 1 dose-escalation study characterized the safety, tolerability, maximum tolerated dose/optimal biological dose, and pharmacokinetics (PK) of TYRP1-TCB in patients with metastatic melanoma (NCT04551352).

Results

Twenty participants with cutaneous, uveal, or mucosal TYRP1-positive melanoma received TYRP1-TCB in escalating doses (0.045 to 0.4 mg). All participants experienced ≥1 treatment-related adverse event (TRAE); two participants experienced grade 3 TRAEs. The most common toxicities were grade 1-2 cytokine release syndrome (CRS) and rash. Fractionated dosing mitigated CRS and was associated with lower levels of interleukin-6 and tumor necrosis factor-alpha. Measurement of active drug (dual TYPR1- and CD3-binding) PK rapidly identified loss of active drug exposure in all participants treated with 0.4 mg in a flat dosing schedule for ≥3 cycles. Loss of exposure was associated with development of ADAs towards both the TYRP1 and CD3 domains. A total drug PK assay, measuring free and ADA-bound forms, demonstrated that TYRP1-TCB-ADA immune complexes were present in participant samples, but showed no drug activity in vitro.

Discussion

This study provides important insights into how the use of active drug PK assays, coupled with mechanistic follow-up, can inform and enable ongoing benefit/risk assessment for individuals participating in FIH dose-escalation trials. Translational studies that lead to a better understanding of the underlying biology of cognate T- and B-cell interactions, ultimately resulting in ADA development to novel biotherapeutics, are needed.

Does Aggregation of Therapeutic IgGs in PBS Offer a True Picture of What Happens in Models Derived from Human Body Fluids?

Therapeutic proteins such as monoclonal antibodies (mAb) are known to form aggregates due to various factors. Phosphate buffered saline (PBS), human serum, and human serum filtrate (HSF) are some of the models used to analyze mAb stability in physiologically relevant in-vitro conditions. In this study, aggregation of mAb in PBS and models derived from body fluids seeded with mAb samples subjected to various stresses were compared. Samples containing mAb subjected to pH, temperature, UV light, stirring, and interfacial agitation stress were seeded into different models for 2 case studies. In the first case study, %HMW (high molecular weight species) of mAb in PBS and HSF were compared using size exclusion chromatography. It was found that change in %HMW was higher in PBS compared to HSF. For example, PBS containing mAb that was subjected to UV light stress showed change in HMW by >10 % over 72 h, but the change was <5 % in HSF. In second case study, aggregates particles of FITC tagged mAb were monitored in PBS and serum using fluorescence microscope image processing. It was found that PBS and serum containing mAb subjected to stirring and interfacial agitation resulted in aggregates of >2 µm size, and average size and percentage number of particles having >10 µm size was higher in serum compared to PBS at all analysis time point. Overall, it was found that aggregation of mAb in PBS was different from that in human body fluids. Second case study also showed the importance of advanced strategies for further characterization of mAb in serum.

A novel Shiga toxin 2a neutralizing antibody therapeutic with low immunogenicity and high efficacy

Shiga toxin-producing Escherichia coli infections are difficult to treat due to the risk of antibiotic-induced stress upregulating the production of toxins, medical treatment is consequently limited to supportive care to prevent the development of hemolytic uremic syndrome (HUS). Here, we introduce a potentially therapeutic humanized mouse monoclonal antibody (Hu-mAb 2-5) targeting Stx2a, the most common Shiga toxin subtype identified from outbreaks. We demonstrate that Hu-mAb 2-5 has low immunogenicity in healthy adults ex vivo and high neutralizing efficacy in vivo, protecting mice from mortality and HUS-related tissue damage.

Assessing MAPPs assay as a tool to predict the immunogenicity potential of protein therapeutics

MHC-II-associated peptide proteomics (MAPPs) is a mass spectrometry-based (MS) method to identify naturally presented MHC-II-associated peptides that could elicit CD4+T cell activation. MAPPs assay is considered one of the assays that better characterize the safety of biotherapeutics by driving the selection of the best candidates concerning their immunogenicity risk. However, there is little knowledge about the impact of bead material on the recovery of MHC-II MS-eluted ligands in MAPPs assays. Here, we firstly describe a robust MAPPs protocol by implementing streptavidin magnetic beads for the isolation of these peptides instead of commonly used NHS-activated beads. Moreover, we assessed the impact of the cell medium used for cell cultures on the morphology and recovery of the in vitro-generated APCs, and its potential implications in the amount of MHC-II isolated peptides. We also described an example of a MAPPs assay application to investigate drug-induced immunogenicity of two bispecific antibodies and compared them with monospecific trastuzumab IgG1 control. This work highlighted the importance of MAPPs in the preclinical in vitro strategy to mitigate the immunogenicity risk of biotherapeutics.

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.

Infliximab aggregates produced in severe and mild elevated temperature stress conditions induce an extended specific CD4 T-cell response

Aggregation has been widely described as a factor contributing to therapeutic antibody immunogenicity. Although production of high-affinity anti-drug antibodies depends on the activation of CD4 T lymphocytes, little is known about the T-cell response induced by antibody aggregates, especially for aggregates produced in mild conditions resulting from minor handling errors of vials. Large insoluble infliximab (IFX) aggregates produced in severe elevated temperature stress conditions have been previously shown to induce human monocyte-derived dendritic cell (moDC) maturation. We here showed that large IFX aggregates recruit in vitro a significantly higher number of CD4 T-cells compared to native IFX. Moreover, a larger array of T-cell epitopes encompassing the entire variable regions was evidenced compared to the native antibody. We then compared the responses of moDCs to different types of aggregates generated by submitting IFX to mild conditions of various times of incubation at an elevated temperature. Decreasing stress duration reduced aggregate size and quantity, and subsequently altered moDC activation. Of importance, IFX aggregates generated in mild conditions and not altering moDC phenotype generated an in vitro T-cell response with a higher frequency of CD4 T cells compared to native IFX. Moreover, cross-reactivity studies of aggregate-specific T cells showed that some T cells could recognize both native and aggregated IFX, while others responded only to IFX aggregates. Taken together, our results suggest that aggregation of antibodies in mild elevated temperature stress conditions is sufficient to alter moDC phenotype in a dose-dependent manner and to increase T-cell response.

Immunogenicity risk assessment of synthetic peptide drugs and their impurities

Peptide drugs play an important part in medicine owing to their many therapeutic applications. Of the 80 peptide drugs approved for use in humans, at least five are now off-patent and are consequently being developed as generic alternatives to the originator products. To accelerate access to generic products, the FDA has proposed new regulatory pathways that do not require direct comparisons of generics to originators in clinical trials. The 'Abbreviated New Drug Application' (ANDA) pathway recommends that sponsors provide information on any new impurities in the generic drug, compared with the originator product, because the impurities can have potential to elicit unwanted immune responses owing to the introduction of T-cell epitopes. This review describes how peptide drug impurities can elicit unexpected immunogenicity and describes a framework for performing immunogenicity risk assessment of all types of bioactive peptide products. Although this report primarily focuses on generic peptides and their impurities, the approach might also be of interest for developers of novel peptide drugs who are preparing their products for an initial regulatory review.

Degranulation of Mast Cells as a Target for Drug Development

Mast cells act as key effector cells of inflammatory responses through degranulation. Mast cell degranulation is induced by the activation of cell surface receptors, such as FcεRI, MRGPRX2/B2, and P2RX7. Each receptor, except FcεRI, varies in its expression pattern depending on the tissue, which contributes to their differing involvement in inflammatory responses depending on the site of occurrence. Focusing on the mechanism of allergic inflammatory responses by mast cells, this review will describe newly identified mast cell receptors in terms of their involvement in degranulation induction and patterns of tissue-specific expression. In addition, new drugs targeting mast cell degranulation for the treatment of allergy-related diseases will be introduced.

Patient-Centric Product Development: A Summary of Select Regulatory CMC and Device Considerations

Patient-centric drug development describes the systematic approach to incorporating the patient's perspectives and preferences into the design, assessment, and production of a therapeutic product. While a patient centric approach can be applied at any stage of the drug development lifecycle, an integrated end-to-end strategy is often most effective to create an optimized product for the patient at the earliest possible timepoint. The importance of patient centricity is well recognized by health authorities and biopharmaceutical organizations which have established toolsets, guidances, and methodologies for incorporating patient input during the clinical stage of development. However, in addition to clinical research, there are other significant aspects of product development that profoundly impact the patient experience. Specifically, chemistry, manufacturing, and control (CMC) and device aspects must also be acknowledged and addressed as part of a cohesive patient-centric development strategy. This review explores current applications and regulatory considerations for patient-centric approaches across the product lifecycle, including R&D, early product development, clinical development, device and combination product development, and post-approval change management. Specific topics of discussion include the contributions of product modality, formulation, and devices to the patient experience; usage of the Quality Target Product Profile (QTPP) as a patient-centered design tool; and post-approval product optimization. Future advancements in regulatory data management and information exchange are also explored as potential enablers of patient engagement which support enhanced communication and interconnectivity between stakeholders. Multidisciplinary collaboration between patients, health authorities, health care providers, and the biopharmaceutical industry is ultimately necessary for ensuring that medicinal products, and their corresponding regulatory processes, take on a patient-first mindset that prioritizes patient needs, values, and preferences.

Optimizing human α-galactosidase for treatment of Fabry disease

Fabry disease is caused by a deficiency of α-galactosidase A (GLA) leading to the lysosomal accumulation of globotriaosylceramide (Gb3) and other glycosphingolipids. Fabry patients experience significant damage to the heart, kidney, and blood vessels that can be fatal. Here we apply directed evolution to generate more stable GLA variants as potential next generation treatments for Fabry disease. GLAv05 and GLAv09 were identified after screening more than 12,000 GLA variants through 8 rounds of directed evolution. Both GLAv05 and GLAv09 exhibit increased stability at both lysosomal and blood pH, stability to serum, and elevated enzyme activity in treated Fabry fibroblasts (19-fold) and GLA^-/- podocytes (10-fold). GLAv05 and GLAv09 show improved pharmacokinetics in mouse and non-human primates. In a Fabry mouse model, the optimized variants showed prolonged half-lives in serum and relevant tissues, and a decrease of accumulated Gb3 in heart and kidney. To explore the possibility of diminishing the immunogenic potential of rhGLA, amino acid residues in sequences predicted to bind MHC II were targeted in late rounds of GLAv09 directed evolution. An MHC II-associated peptide proteomics assay confirmed a reduction in displayed peptides for GLAv09. Collectively, our findings highlight the promise of using directed evolution to generate enzyme variants for more effective treatment of lysosomal storage diseases.

A review of therapeutic failures in late-stage clinical trials

INTRODUCTION

The process of drug approval involves extensive and expensive preclinical and clinical examination. Most drugs entering late-stage clinical trials get terminated for a variety of reasons including inability to achieve the primary endpoints or intolerable adverse effects. Only one-tenth of the drugs that enter clinical trials progress to Food and Drug Administration (FDA) regulatory submission.

AREAS COVERED

This review offers insight into some of the attributes that may be responsible for a drug's failure in late-stage trials. Information from multiple open sources including PubMed articles published between 1989 and 2019, recent articles from authentic websites like www.ClinicalTrials.gov, www.fda.gov, and pharmaceutical news articles for the years between 2017 and 2021 were accumulated and summarized. Further, a few drug candidates that reached the phase III clinical trials but were discontinued at later stages have been presented as case studies.

EXPERT OPINION

Ineluctable failures were observed due to insufficient knowledge about the mechanism of action where the disease progression stages are unclear. Other reasons were choice of patient population, late-stage treatment, and dosage. Adhering to the guidelines and recommendations provided by the regulatory authorities and learning from past failures, considerably reduce failure rates.

In vitro and in vivo immunogenicity assessment of protein aggregate characteristics

The immunogenicity risk of therapeutic protein aggregates has been extensively investigated over the past decades. While it is established that not all aggregates are equally immunogenic, the specific aggregate characteristics, which are most likely to induce an immune response, remain ambiguous. The aim of this study was to perform comprehensive in vitro and in vivo immunogenicity assessment of human insulin aggregates varying in size, structure and chemical modifications, while keeping other morphological characteristics constant. We found that flexible aggregates with highly altered secondary structure were most immunogenic in all setups, while compact aggregates with native-like structure were found to be immunogenic primarily in vivo. Moreover, sub-visible (1-100 µm) aggregates were found to be more immunogenic than sub-micron (0.1-1 µm) aggregates, while chemical modifications (deamidation, ethylation and covalent dimers) were not found to have any measurable impact on immunogenicity. The findings highlight the importance of utilizing aggregates varying in few characteristics for assessment of immunogenicity risk of specific morphological features and may provide a workflow for reliable particle analysis in biotherapeutics.

Rapid in vitro assessment of the immunogenicity potential of engineered antibody therapeutics through detection of CD4+ T cell interleukin-2 secretion

Therapeutic antibodies sometimes elicit anti-drug antibodies (ADAs) that can affect efficacy and safety. Engineered antibodies that contain artificial amino acid sequences are potentially highly immunogenic, but this is currently difficult to predict. Therefore, it is important to efficiently assess immunogenicity during the development of complex antibody-based formats. Here, we present an in vitro peripheral blood mononuclear cell-based assay that can be used to assess immunogenicity potential within 3 days. This method involves examining the frequency and function of interleukin (IL)-2-secreting CD4+ T cells induced by therapeutic antibodies. IL-2-secreting CD4+ T cells seem to be functionally relevant to the immunogenic potential due to their proliferative activity and the expression of several cytokines. The rates of the donors responding to low and high immunogenic proteins, mAb1, and keyhole limpet hemocyanin were 1.3% and 93.5%, respectively. Seven antibodies with known rates of immunogenicity (etanercept, emicizumab, abciximab, romosozumab, blosozumab, humanized anti-human A33 antibody, and bococizumab) induced responses in 1.9%, 3.8%, 6.4%, 10.0%, 29.2%, 43.8%, and 89.5% of donors, respectively. These data are comparable with ADA incidences in clinical settings. Our results show that this assay can contribute to the swift assessment and mechanistic understanding of the immunogenicity of therapeutic antibodies.

Combined IgE neutralization and Bifidobacterium longum supplementation reduces the allergic response in models of food allergy

IgE is central to the development of allergic diseases, and its neutralization alleviates allergic symptoms. However, most of these antibodies are based on IgG1, which is associated with an increased risk of fragment crystallizable-mediated side effects. Moreover, omalizumab, an anti-IgE antibody approved for therapeutic use, has limited benefits for patients with high IgE levels. Here, we assess a fusion protein with extracellular domain of high affinity IgE receptor, FcεRIα, linked to a IgD/IgG4 hybrid Fc domain we term IgE_TRAP, to reduce the risk of IgG1 Fc-mediated side effects. IgE_TRAP shows enhanced IgE binding affinity compared to omalizumab. We also see an enhanced therapeutic effect of IgE_TRAP in food allergy models when combined with Bifidobacterium longum, which results in mast cell number and free IgE levels. The combination of IgE_TRAP and B. longum may therefore represent a potent treatment for allergic patients with high IgE levels.

IgE is a critical component of the allergic response and therapeutic targeting can alleviate symptomology. Here the authors propose the combined use of Bifidobacterium longum and a FcεRIα extracellular domain linked to a IgD/IgG4 hybrid Fc domain fusion protein called IgE_TRAP and show reduction of mast cell and IgE levels in models of food allergy.

Navigating regulatory pathways for translation of biologic cartilage repair products

Long-term clinical repair of articular cartilage remains elusive despite advances in cartilage tissue engineering. Only one cartilage repair therapy classified as a "cellular and gene therapy product" has obtained Food and Drug Administration (FDA) approval within the past decade although more than 200 large animal cartilage repair studies were published. Here, we identify the challenges impeding translation of strategies and technologies for cell-based cartilage repair, such as the disconnect between university funding and regulatory requirements. Understanding the barriers to translation and developing solutions to address them will be critical for advancing cell therapy products for cartilage repair to clinical use.

Scientific Rationale for Waiving Clinical Efficacy Testing of Biosimilars

After 18 years and the administration of billions of doses, there is little doubt about biosimilars’ safety and efficacy. Yet, only 14 molecules in the EU and 9 in the US are available as biosimilars, among the 200+ targets, due mainly to the high development cost attributed to clinical efficacy testing after extensive analytical assessment, nonclinical testing, and clinical pharmacology comparisons. So far, none of the hundreds of clinical efficacy testing has failed because it cannot fail due to its lack of sensitivity for multiple reasons, as argued in this paper. This analysis is unique since biosimilars are the first category of products that are put to comparative testing as if these were new biological drugs. Clinical efficacy testing used to overcome differences in the analytical, nonclinical, and clinical pharmacology comparisons can lead to the approval of unsafe products. Only recently the regulatory agencies have begun to talk about this risk and shown their willingness to waive these studies. However, a clear change in the regulatory guidelines is required to change the mindset of all biosimilar stakeholders to bring a pivotal change in the availability of affordable biosimilars.

Long-acting injectable formulation technologies: Challenges and opportunities for the delivery of fragile molecules

INTRODUCTION

The development of long acting injectables (LAIs) for protein and peptide therapeutics has been a key challenge over the last 20 years. If these molecules offer advantages due to their high specificity and selectivity, their controlled release may confer several additional benefits in terms of extended half-life, local delivery, and patient compliance.

AREA COVERED

This manuscript aims to give an overview of peptide and protein based LAIs from an industrial perspective, describing both approved and promising technologies (with exceptions of protein engineering strategies and devices), their advantages and potential improvements to aid their access to the market.

EXPERT OPINION

Many LAIs have been developed for peptides, with formulations on the market for several decades. On the contrary, LAIs for proteins are still far from the market and issues related to manufacturing and sterilization of these products still need to be overcome. In situ forming depots (ISFDs), whose simple manufacturing conditions and easy administration procedures (without reconstitution) are strong advantages, appear as one of the most promising technologies for the delivery of these molecules. In this regard, the approval of ELIGARD® in the early 2000's (which still requires a complex reconstitution process), paved the way for the development of second-generation, ready-to-use ISFD technologies like BEPO® and FluidCrystal®.

Immunogenicity Risk Assessment of Spontaneously Occurring Therapeutic Monoclonal Antibody Aggregates

Aggregates of therapeutic proteins have been associated with increased immunogenicity in pre-clinical models as well as in human patients. Recent studies to understand aggregates and their immunogenicity risks use artificial stress methods to induce high levels of aggregation. These methods may be less biologically relevant in terms of their quantity than those that occur spontaneously during processing and storage. Here we describe the immunogenicity risk due to spontaneously occurring therapeutic antibody aggregates using peripheral blood mononuclear cells (PBMC) and a cell line with a reporter gene for immune activation: THP-1 BLUE NFκB. The spontaneously occurring therapeutic protein aggregates were obtained from process intermediates and final formulated drug substance from stability retains. Spontaneously occurring aggregates elicited innate immune responses for several donors in a PBMC assay with cytokine and chemokine production as a readout for immune activation. Meanwhile, no significant adaptive phase responses to spontaneously occurring aggregate samples were detected. While the THP-1 BLUE NFκB cell line and PBMC assays both responded to high stress induced aggregates, only the PBMC from a limited subset of donors responded to processing-induced aggregates. In this case study, levels of antibody aggregation occurring at process relevant levels are lower than those induced by stirring and may pose lower risk in vivo. Our methodologies can further inform additional immunogenicity risk assessments using a pre-clinical in vitro risk assessment approach utilizing human derived immune cells.

Holistic Analytical Characterization and Risk Assessment of Residual Host Cell Protein Impurities in an Active Pharmaceutical Ingredient (API) Synthesized by Biocatalysts

Host cell proteins (HCPs) are a significant class of process-related impurities commonly associated with the manufacturing of biopharmaceuticals. However, due to the increased use of crude enzymes as biocatalysts for modern organic synthesis, HCPs can also be introduced as a new class of impurities in chemical drugs. In both cases, residual HCPs need to be adequately controlled to ensure product purity, quality, and patient safety. Although a lot of attentions have been focused on defining a universally acceptable limit for such impurities, the risks associated with residual HCPs on product quality, safety, and efficacy often need to be determined on a case-by-case basis taking into consideration the residual HCP profile in the product, the dose, dosage form, and administration route etc. Here we describe the unique challenges for residual HCP control presented by the biocatalytic synthesis of a Merck investigational stimulator of interferon genes protein (STING) agonist, MK-1454, which is a cyclic dinucleotide synthesized using E. coli cell lysate overexpressing cyclic GMP-AMP synthase (cGAS) as a biocatalyst. In this study, a holistic characterization of residual protein impurities using a variety of analytical tools including nano-LC-MS/MS, together with in silico immunogenicity prediction of identified proteins, facilitated risk assessment and guided process development to achieve adequate removal of residual protein impurities in MK-1454 API. This article is protected by copyright. All rights reserved.

Implementing a Clinical Immunogenicity Strategy using Preclinical Risk Assessment Outputs

Immunogenicity to biologics is often observed following dosing in human subjects during clinical trials. Both product and host specific factors may be implicated in contributing to a potential immune response. However, even if such risk factors are identified and eliminated as part of the rational quality by design approaches, the outcome in clinic can be uncertain and challenging to predict. Several tools have been employed to identify these risk factors and consequent mitigation approaches implemented prior to dosing in humans. However, the complexity of the immune system with an interplay of network of immune cells involved in driving a long- term immune response as well as patient characteristics, can make it challenging to predict the outcome in clinic. This perspective will provide an insight into recent advances in the risk assessment approaches that are utilized during preclinical stage of development of a biologic. The outputs from such tools can help to rank order and select the most optimal candidate with the least likelihood of an immune response and can further drive the development of a clinical bioanalytical and immunogenicity monitoring strategy. Such a strategy can be proactively shared with the regulators along with the proposal to streamline clinical immunogenicity and personalizing the outcome based on pharmacogenomics and other patient-related factors. This paper provides a roadmap on performing risk assessments through a systematic identification of risks and their mitigations wherever possible. Recommendations on incorporating the key components of such risk assessments as part of the new regulatory submissions are also provided. Shorter abstract Immunogenicity to biologics is common during clinical trials. Both product and host specific factors have been implicated. Several risk assessment tools can be used to identify and mitigate the risk factors responsible for immunogenicity. An insight into recent advances in the risk assessment approaches will be presented. The outputs can define a risk score and guide the clinical bioanalytical and immunogenicity monitoring strategy. A roadmap on performing risk assessments through a systematic identification of risks and their mitigations wherever possible is provided. Best practices for a risk assessment strategy and recommendations on the content for IND and the Integrated summary of Immunogenicity are also provided.

Assay format diversity in pre-clinical immunogenicity risk assessment: Toward a possible harmonization of antigenicity assays

A major impediment to successful use of therapeutic protein drugs is their ability to induce anti-drug antibodies (ADA) that can alter treatment efficacy and safety in a significant number of patients. To this aim, in silico, in vitro, and in vivo tools have been developed to assess sequence and other liabilities contributing to ADA development at different stages of the immune response. However, variability exists between similar assays developed by different investigators due to the complexity of assays, a degree of uncertainty about the underlying science, and their intended use. The impact of protocol variations on the outcome of the assays, i.e., on the immunogenicity risk assigned to a given drug candidate, cannot always be precisely assessed. Here, the Non-Clinical Immunogenicity Risk Assessment working group of the European Immunogenicity Platform (EIP) reviews currently used assays and protocols and discusses feasibility and next steps toward harmonization and standardization.

Nanovesicles released by OKT3 hybridoma express fully active antibodies

Recent findings have shown that nanovesicles preparations from either primary immune cells culture supernatants or plasma contain immunoglobulins, suggesting that a natural way of antibody production may be through exosome release. To verify this hypothesis, we used the OKT3 hybridoma clone, which produces a murine IgG2a monoclonal antibody used to reduce rejection in patients undergoing organ transplantation. We showed exosome-associated immunoglobulins in hybridoma supernatants, by Western blot, nanoscale flow cytometry and immunocapture-based ELISA. The OKT3-exo was also being able to trigger cytokines production in both CD4 and CD8 T cells. These results show that nanovesicles contain immunoglobulin and could be used for immunotherapy. These data could lead to a new approach to improve the effectiveness of therapeutic antibodies by exploiting their natural property to be expressed on nanovesicle membrane, that probably render them more stable and as a consequence more capable to interact with their specific ligand in the best way.

A general evidence-based sequence variant control limit for recombinant therapeutic protein development

Sequence variants (SVs) resulting from unintended amino acid substitutions in recombinant therapeutic proteins have increasingly gained attention from both regulatory agencies and the biopharmaceutical industry given their potential impact on efficacy and safety. With well-optimized production systems, such sequence variants usually exist at very low levels in the final protein products due to the high fidelity of DNA replication and protein biosynthesis process in mammalian expression systems such as Chinese hamster ovary cell lines. However, their levels can be significantly elevated in cases where the selected production cell line has unexpected DNA mutations or the manufacturing process is not fully optimized, for example, if depletion of certain amino acids occurs in the cell culture media in bioreactors. Therefore, it is important to design and implement an effective monitoring and control strategy to prevent or minimize the possible risks of SVs during the early stage of product and process development. However, there is no well-established guidance from the regulatory agencies or consensus across the industry to assess and manage SV risks. A question frequently asked is: What levels of SVs can be considered acceptable during product and process development, but also have no negative effects on drug safety and efficacy in patients? To address this critical question, we have taken a holistic approach and conducted a comprehensive sequence variant analysis. To guide biologic development, a general SV control limit of 0.1% at individual amino acid sites was proposed and properly justified based on extensive literature review, SV benchmark survey of approved therapeutic proteins, and accumulated experience on SV control practice at Regeneron.

In vitro immunogenicity prediction: bridging between innate and adaptive immunity

Development of antidrug antibodies (ADAs) is an undesirable potential outcome of administration of biotherapeutics and involves the innate and adaptive immune systems. ADAs can have detrimental clinical consequences: they can reduce biotherapeutic efficacy or produce adverse events. Because animal models are considered poor predictors of immunogenicity in humans, in vitro assays with human innate and adaptive immune cells are commonly used alternatives that can reveal cell-mediated unwanted immune responses. Multiple methods have been developed to assess the immune cell response following exposure to biotherapeutics and estimate the potential immunogenicity of biotherapeutics. This review highlights the role of innate and adaptive immune cells as the drivers of immunogenicity and summarizes the use of these cells in assays to predict clinical ADA.

Managing the Impact of Immunogenicity in an Era of Immunotherapy: From Bench to Bedside

Biotherapeutics have revolutionized our ability to treat life-threatening diseases. Despite clinical success, the use of biotherapeutics has sometimes been limited by the immune response mounted against them in the form of anti-drug antibodies (ADAs). The multifactorial nature of immunogenicity has prevented a standardized approach for assessing this and each of the assessment methods developed so far does not exhibit high enough reliability to be used alone, due to limited predictiveness. This prompted the Roche Pharma Research and Early Development (pRED) Immunogenicity Working Group to establish an internal preclinical immunogenicity toolbox of in vitro/in vivo approaches and accompanying guidelines for a harmonized assessment and management of immunogenicity in early development. In this article, the complex factors influencing immunogenicity and their associated clinical ramifications are discussed to highlight the importance of an end-to-end approach conducted from lead optimization to clinical candidate selection. We then examine the impact of the resulting lead candidate categorization on the design and implementation of a multi-tiered ADA/immunogenicity assay strategy prior to phase I (entry into human) through early clinical development. Ultimately, the Immunogenicity Toolbox ensures that Roche pRED teams are equipped to address immunogenicity in a standardized manner, paving the way for lifesaving products with improved safety and efficacy.

An IgG-based bispecific antibody for improved dual targeting in PSMA-positive cancer

The prostate-specific membrane antigen (PSMA) has been demonstrated in numerous studies to be expressed specifically on prostate carcinoma cells and on the neovasculature of several other cancer entities. However, the simultaneous expression of PSMA on both, tumor cells as well as tumor vessels remains unclear, even if such "dual" expression would constitute an important asset to facilitate sufficient influx of effector cells to a given tumor site. We report here on the generation of a PSMA antibody, termed 10B3, which exerts superior dual reactivity on sections of prostate carcinoma and squamous cell carcinoma of the lung. 10B3 was used for the construction of T-cell recruiting bispecific PSMAxCD3 antibodies in Fab- and IgG-based formats, designated Fabsc and IgGsc, respectively. In vitro, both molecules exhibited comparable activity. In contrast, only the larger IgGsc molecule induced complete and durable elimination of established tumors in humanized mice due to favorable pharmacokinetic properties. Upon treatment of three patients with metastasized prostate carcinoma with the IgGsc reagent, marked activation of T cells and rapid reduction of elevated PSA levels were observed.

Immunogenicity risk assessment for biotherapeutics through in vitro detection of CD134 and CD137 on T helper cells

Biotherapeutics, which are biologic medications that are natural or bioengineered products of living cells, have revolutionized the treatment of many diseases. However, unwanted immune responses still present a major challenge to their widespread adoption. Many patients treated with biotherapeutics develop antigen-specific anti-drug antibodies (ADAs) that may reduce the efficacy of the therapy or cross-react with the endogenous counterpart of a protein therapeutic, or both. Here, we describe an in vitro method for assessing the immunogenic risk of a biotherapeutic. We found a correlation between clinical immunogenicity and the frequency with which a biotherapeutic stimulated an increase in CD134, CD137, or both cell surface markers on CD4+ T cells. Using high-throughput flow cytometry, we examined the effects of 14 biotherapeutics with diverse rates of clinical immunogenicity on peripheral blood mononuclear cells from 120 donors with diverse human leukocyte antigen class II-encoding alleles. Biotherapeutics with high rates of ADA development in the clinic had higher proportions of CD4+ T cells positive for CD134 or CD137 than biotherapeutics with low clinical immunogenicity. This method provides a rapid and simple preclinical test of the immunogenic potential of a new candidate biotherapeutic or biosimilar. Implementation of this approach during biotherapeutic research and development enables rapid elimination of candidates that are likely to cause ADA-related adverse events and detrimental consequences.

Discovery-stage identification of drug-like antibodies using emerging experimental and computational methods

There is intense and widespread interest in developing monoclonal antibodies as therapeutic agents to treat diverse human disorders. During early-stage antibody discovery, hundreds to thousands of lead candidates are identified, and those that lack optimal physical and chemical properties must be deselected as early as possible to avoid problems later in drug development. It is particularly challenging to characterize such properties for large numbers of candidates with the low antibody quantities, concentrations, and purities that are available at the discovery stage, and to predict concentrated antibody properties (e.g., solubility, viscosity) required for efficient formulation, delivery, and efficacy. Here we review key recent advances in developing and implementing high-throughput methods for identifying antibodies with desirable in vitro and in vivo properties, including favorable antibody stability, specificity, solubility, pharmacokinetics, and immunogenicity profiles, that together encompass overall drug developability. In particular, we highlight impressive recent progress in developing computational methods for improving rational antibody design and prediction of drug-like behaviors that hold great promise for reducing the amount of required experimentation. We also discuss outstanding challenges that will need to be addressed in the future to fully realize the great potential of using such analysis for minimizing development times and improving the success rate of antibody candidates in the clinic.

The blood endothelial cell chamber - An innovative system to study immune responses in drug development

The risk for adverse immune-mediated reactions, associated with the administration of certain immunotherapeutic agents, should be mitigated early. Infusion reactions to monoclonal antibodies and other biopharmaceuticals, known as cytokine release syndrome, can arise from the release of cytokines via the drug target cell, as well as the recruitment of immune effector cells. While several in vitro cytokine release assays have been proposed up to date, many of them lack important blood components, required for this response to occur. The blood endothelial cell chamber model is an in vitro assay, composed of freshly drawn human whole blood and cultured human primary endothelial cells. Herein, its potential to study the compatibility of immunotherapeutics with the human immune system was studied by evaluating three commercially available monoclonal antibodies and bacterial endotoxin lipopolysaccharide. We demonstrate that the anti-CD28 antibody TGN1412 displayed an adaptive cytokine release profile and a distinct IL-2 response, accompanied with increased CD3⁺ cell recruitment. Alemtuzumab exhibited a clear cytokine response with a mixed adaptive/innate source (IFNγ, TNFα and IL-6). Its immunosuppressive nature is observed in depleted CD3⁺ cells. Cetuximab, associated with low infusion reactions, showed a very low or absent stimulatory effect on proinflammatory cytokines. In contrast, bacterial endotoxin demonstrated a clear innate cytokine response, defined by TNFα, IL-6 and IL-1β release, accompanied with a strong recruitment of CD14⁺CD16⁺ cells. Therefore, the blood endothelial cell chamber model is presented as a valuable in vitro tool to investigate therapeutic monoclonal antibodies with respect to cytokine release and vascular immune cell recruitment.

Globally deimmunized lysostaphin evades human immune surveillance and enables highly efficacious repeat dosing

There is a critical need for novel therapies to treat methicillin-resistant Staphylococcus aureus (MRSA) and other drug-resistant pathogens, and lysins are among the vanguard of innovative antibiotics under development. Unfortunately, lysins' own microbial origins can elicit detrimental antidrug antibodies (ADAs) that undermine efficacy and threaten patient safety. To create an enhanced anti-MRSA lysin, a novel variant of lysostaphin was engineered by T cell epitope deletion. This "deimmunized" lysostaphin dampened human T cell activation, mitigated ADA responses in human HLA transgenic mice, and enabled safe and efficacious repeated dosing during a 6-week longitudinal infection study. Furthermore, the deimmunized lysostaphin evaded established anti-wild-type immunity, thereby providing significant anti-MRSA protection for animals that were immune experienced to the wild-type enzyme. Last, the enzyme synergized with daptomycin to clear a stringent model of MRSA endocarditis. By mitigating T cell-driven antidrug immunity, deimmunized lysostaphin may enable safe, repeated dosing to treat refractory MRSA infections.

Humanized bispecific antibody (mPEG × HER2) rapidly confers PEGylated nanoparticles tumor specificity for multimodality imaging in breast cancer

Background

Developing a universal strategy to improve the specificity and sensitivity of PEGylated nanoaparticles (PEG-NPs) for assisting in the diagnosis of tumors is important in multimodality imaging. Here, we developed the anti-methoxypolyethylene glycol (mPEG) bispecific antibody (BsAb; mPEG × HER2), which has dual specificity for mPEG and human epidermal growth factor receptor 2 (HER2), with a diverse array of PEG-NPs to confer nanoparticles with HER2 specificity and stronger intensity.

Result

We used a one-step formulation to rapidly modify the nanoprobes with mPEG × HER2 and optimized the modified ratio of BsAbs on several PEG-NPs (Lipo-DiR, SPIO, Qdot and AuNP). The αHER2/PEG-NPs could specifically target MCF7/HER2 cells (HER2⁺⁺) but not MCF7/neo1 cells (HER2^+/−). The αHER2/Lipo-DiR and αHER2/SPIO could enhance the sensitivity of untargeted PEG-NPs on MCF7/HER2 (HER2⁺⁺). In in vivo imaging, αHER2/Lipo-DiR and αHER2/SPIO increased the specific targeting and enhanced PEG-NPs accumulation at 175% and 187% on 24 h, respectively, in HER2-overexpressing tumors.

Conclusion

mPEG × HER2, therefore, provided a simple one-step formulation to confer HER2-specific targeting and enhanced sensitivity and contrast intensity on HER2 positive tumors for multimodality imaging.

Fit-for-Purpose Validation and Establishment of Assay Acceptance and Reporting Criteria of Dendritic Cell Activation Assay Contributing to the Assessment of Immunogenicity Risk

Validation of key analytical and functional performance characteristics of in vitro immunogenicity risk assessment assays increases our confidence in utilizing them for screening biotherapeutics. Herein, we present a fit-for-purpose (FFP) validation of a dendritic cell (DC) activation assay designed to assess the immunogenicity liability of protein biotherapeutics. Characterization of key assay parameters was achieved using monocyte-derived DCs (MoDCs) treated with cell culture medium only (i.e., background control (BC)), keyhole limpet hemocyanin (KLH) as system positive control (SPC), and 2 therapeutic monoclonal antibodies (mAbs) with known clinical immunogenicity profiles (bococizumab and TAM163) as therapeutic controls (TCs). In the absence of established validation guidelines for primary cell-based assays, the present DC activation assay was validated using a novel FFP approach which allows more flexibility in selection of validation parameters and designing of experiments based on the intended use of the assay. The present FFP validation allowed us to understand the impact of experimental variables on assay precision, develop a clear concise readout for DC activation results, establish a reliable response threshold to define a result as a positive DC activation response, and define in-study donor acceptance criteria and cohort size. FFP validation of this DC activation assay indicated that the assay is sufficient to support its context of use, a preclinical immunogenicity risk management tool.

T-Cell Dependent Immunogenicity of Protein Therapeutics Pre-clinical Assessment and Mitigation-Updated Consensus and Review 2020

Immune responses to protein and peptide drugs can alter or reduce their efficacy and may be associated with adverse effects. While anti-drug antibodies (ADA) are a standard clinical measure of protein therapeutic immunogenicity, T cell epitopes in the primary sequences of these drugs are the key drivers or modulators of ADA response, depending on the type of T cell response that is stimulated (e.g., T helper or Regulatory T cells, respectively). In a previous publication on T cell-dependent immunogenicity of biotherapeutics, we addressed mitigation efforts such as identifying and reducing the presence of T cell epitopes or T cell response to protein therapeutics prior to further development of the protein therapeutic for clinical use. Over the past 5 years, greater insight into the role of regulatory T cell epitopes and the conservation of T cell epitopes with self (beyond germline) has improved the preclinical assessment of immunogenic potential. In addition, impurities contained in therapeutic drug formulations such as host cell proteins have also attracted attention and become the focus of novel risk assessment methods. Target effects have come into focus, given the emergence of protein and peptide drugs that target immune receptors in immuno-oncology applications. Lastly, new modalities are entering the clinic, leading to the need to revise certain aspects of the preclinical immunogenicity assessment pathway. In addition to drugs that have multiple antibody-derived domains or non-antibody scaffolds, therapeutic drugs may now be introduced via viral vectors, cell-based constructs, or nucleic acid based therapeutics that may, in addition to delivering drug, also prime the immune system, driving immune response to the delivery vehicle as well as the encoded therapeutic, adding to the complexity of assessing immunogenicity risk. While it is challenging to keep pace with emerging methods for the preclinical assessment of protein therapeutics and new biologic therapeutic modalities, this collective compendium provides a guide to current best practices and new concepts in the field.

Regulatory and strategic considerations for addressing immunogenicity and related responses in biopharmaceutical development programs

The last three decades have seen the biotherapeutic drug market evolve from promising concept to market dominance in a range of clinical indications. This growth has been spurred by the success of established drug classes like monoclonal antibodies, but also by the introduction of biosimilars, and more recently, multiple novel cell and gene therapies. Biotherapeutic drug development presents many unique challenges, but unintended immune responses are among the most common reasons for program attrition. Anti-drug antibodies can impact the safety and efficacy of drug products, and related immune responses, like the cytokine release syndrome that occurred in the infamous TGN-1412 clinical trial, can be challenging to predict with nonclinical models. For this reason, it is important that development programs proceed with a scientifically grounded and measured approach to these responses. This process begins at the discovery stage with the application of “quality by design,” continues into the clinic with the development of quality assays and management strategies, and culminates in the effective presentation of this information in regulatory documents. This review provides an overview of some of the key strategic and regulatory considerations for biotherapeutics as they pertain to immunogenicity and related responses.

Immunogenicity of Bioproducts: Cellular Models to Evaluate the Impact of Therapeutic Antibody Aggregates

Patients treated with bioproducts (BPs) frequently develop anti-drug antibodies (ADAs) with potential neutralizing capacities leading to loss of clinical response or potential hypersensitivity reactions. Many factors can influence BP immunogenicity and could be related to the patient, the treatment, as well as to the product itself. Among these latter factors, it is now well accepted that BP aggregation is associated with an increased potential for immunogenicity, as aggregates seem to be correlated with ADA development. Moreover, the presence of high-affinity ADAs suggests a CD4 T-cell dependent adaptive immune response and therefore a pivotal role for antigen-presenting cells (APCs), such as dendritic cells (DCs). In this review, we address the in vitro methods developed to evaluate how monoclonal antibodies could trigger the immunization process by focusing on the role of aggregated antibodies in the establishment of this response. In particular, we will present the different cell-based assays that have been used to assess the potential of antibodies and their aggregates to modulate cellular mechanisms leading to activation and the biological parameters (cellular activation markers, proliferation and secreted molecules) that can be measured to evaluate the different cell activation stages and their consequences in the propagation of the immune response. Indeed, the use of such strategies could help evaluate the risk of BP immunogenicity and their role in mitigating this risk.

In vitro human helper T-cell assay to screen antibody drug candidates for immunogenicity

Monoclonal antibody (mAb) drugs offer a number of valuable treatments. Many newly developed mAb drugs include artificial modification of amino acid sequences from human origin, which may cause higher immunogenicity to induce anti-drug antibodies (ADA). If the immunogenicity of a new candidate can be understood in the nonclinical phase, clinical studies will be safer and the success rate of development improved. Empirically, in vitro immunogenicity assays with human cells have proved to be sufficiently sensitive to nonhuman proteins, but not to human/humanized mAb. To detect the weaker immunogenicity of human-based mAb, a more sensitive biomarker for in vitro assays is needed. The in vitro study here developed a proliferation assay (T_H cell assay) using flow cytometry analysis that can detect a slight increase in proliferating T_H cells. Samples from 218 donors treated with a low-immunogenic drug (etanercept) were measured to determine a positive threshold level. With this threshold, positive donor percentages among PBMC after treatment with higher-immunogenicity mAb drugs were noted, that is, 39.5% with humanized anti-human A33 antibody (hA33), 27.3% with abciximab, 25.9% with adalimumab, and 14.8% with infliximab. Biotherapeutics with low immunogenicity yielded values of 0% for basiliximab and 3.7% for etanercept. These data showed a good comparability with previously reported incidences of clinical ADA with the evaluated drugs. Calculations based on the data here showed that a T_H cell assay with 40 donors could provide statistically significant differences when comparing low- (etanercept) versus highly immunogenic mAb (except for infliximab). Based on the outcomes here, for screening purposes, a practical cutoff point of 3/20 positives with 20 donors was proposed to alert immunogenicity of mAb drug candidates.

Discovery of lixisenatide analogues as long-acting hypoglycemic agents using novel peptide half-life extension technology based on mycophenolic acid

Noncovalent binding of peptides to human serum albumin protects against renal clearance and enzymatic degradation. Herein, we investigated the effect of mycophenolic acid (MPA) albumin binders for improving the stability of peptides. For proof-of-principle, the short acting glucagon-like peptide-1 (GLP-1) receptor agonist lixisenatide was selected and functionalized with different MPA albumin binders. In vitro, all lixisenatide analogues showed well preserved GLP-1 receptor activation potency. High performance affinity chromatography (HPAC) and ultrafiltration analyses indicated that DiMPA was able to confer high albumin affinity to lixisenatide and revealed that affinity is increased for DiMPA modified lixisenatide analogues containing OEG spacers. In db/db mice, the selected peptide 2c showed comparable efficacies to lixisenatide with respect to glucose-lowering and insulinotropic activities. Furthermore, the duration of action of glucose homeostasis of 2c was comparable to semaglutide in db/db mice. Importantly, DiMPA albumin binder did not bring significant toxicity of lixisenatide, as reflected by the comparable toxicity indexes in 2c and semaglutide groups after 2 weeks dosing in normal Kunming mice. Short-term study (21 days) conducted on db/db mice showed the better therapeutic efficacies of 2c than semaglutide on pancreas islets protection. Importantly, in chronic studies (84 days) on db/db mice, 2c exhibited a sustained improvement in glycaemic control, to a greater extent than that of semaglutide. Thus, we propose DiMPA modification as a novel and general method for development of long-acting GLP-1 receptor agonists for type 2 diabetes treatments, and 2c as a promising antidiabetic candidate.

DiMPA albumin binders were effectively applied to lixisenatide to make 2c as a long-acting antidiabetic agent.

Clinical Immunogenicity Risk Assessment Strategy for a Low Risk Monoclonal Antibody

This article provides a theoretical case-study risk assessment report for a low-risk monoclonal antibody (mAb) therapeutic. In terms of risk, there are considerations around risks to safety, but also risks regarding effects on pharmacokinetics (PK), pharmacodynamics (PD), and efficacy. Much of the discussion in this document is around the risk of immunogenicity incidence. A higher incidence of immunogenicity would necessitate a detailed review of the PK, efficacy and safety in anti-drug antibody (ADA) positive and ADA negative subjects, in order to evaluate potential effects. The publication is intended to provide a framework of some the current thought processes around assessing immunogenicity risk and for building strategies to mitigate those risks. For this example, we have created a hypothetical antibody, ABC-123, targeting a membrane protein on antigen presenting cells, for the treatment of rheumatoid arthritis (RA). This hypothetical antibody therapeutic is provided as an example for the purposes of risk assessment for a low risk molecule, although any application of similar approach would be case by case.

Immunostimulatory effects on THP-1 cells by peptide or protein pharmaceuticals associated with injection site reactions

Injection site reaction (ISR) is a common side-effect associated with the use of peptide or protein pharmaceuticals. These types of pharmaceuticals-induced activation of antigen-presenting cells is assumed to be a key step in the pathogenesis of immune-mediated ISR. The present study was designed to evaluate the immunostimulatory properties of peptide or protein pharmaceuticals using human monocytic THP-1 cells. Here, THP-1 cells, with or without phorbol-12-myristate-13-acetate (PMA) pretreatment, were exposed to enfuvirtide and glatiramer acetate (positive controls) or evolocumab (negative control) for 6 or 24 h. PMA treatment differentiated non-adherent monocytic THP-1 (nTHP-1) cells into adherent macrophagic THP-1 (pTHP-1) cells that highly express CD11b and CD36. Enfuvirtide increased the release of cytokines, e.g. TNFα, MIP-1β, and MCP-1, and expression of CD86 and CD54 on nTHP-1 cells at 24 h. Similar immunostimulatory properties of glatiramer acetate were observed both in the nTHP-1 and pTHP-1 cells at 6 h, but the responses were very weak in the pTHP-1 cells. Evolocumab did not affect cytokine secretion or cell surface marker expression in either cell type. Taken together, these in vitro THP-1 cell assays revealed the immunostimulatory properties of enfuvirtide and glatiramer acetate. This assay platform thus could serve as a powerful tool in evaluating potential immune-related ISR risks of peptide or protein pharmaceuticals in humans.

In Vitro ELISA and Cell-Based Assays Confirm the Low Immunogenicity of VNAR Therapeutic Constructs in a Mouse Model of Human RA: An Encouraging Milestone to Further Clinical Drug Development

Anti-drug antibodies (ADAs), specific for biotherapeutic drugs, are associated with reduced serum drug levels and compromised therapeutic response. The impact of ADA on the bioavailability and clinical efficacy of blockbuster anti-hTNF-α monoclonal antibodies is well recognised, especially for adalimumab and infliximab treatments, with the large and complex molecular architecture of classical immunoglobulin antibody drugs, in part, responsible for the immunogenicity seen in patients. The initial aim of this study was to develop solid-phase enzyme-linked immunosorbent assays (ELISA) and an in vitro cell-based method to accurately detect ADA and estimate its impact on the preclinical in vivo efficacy outcomes of two novel, nonimmunoglobulin VNAR fusion anti-hTNF-α biologics (Quad-X™ and D1-NDure™-C4) and Humira®, a brand of adalimumab. Serum drug levels and the presence of ADA were determined in a transgenic mouse model of polyarthritis (Tg197) when Quad-X™ and Humira® were dosed at 1 mg/kg and D1-NDure™-C4 was dosed at 30 mg/kg. The serum levels of the Quad-X™ and D1-NDure™-C4 modalities were consistently high and comparable across all mice within the same treatment groups. In 1 mg/kg and 3 mg/kg Quad-X™- and 30 mg/kg D1-NDure™-C4-treated mice, an average trough drug serum concentration of 8 μg/mL, 50 μg/mL, and 350 μg/mL, respectively, were estimated. In stark contrast, Humira® trough serum concentrations in the 1 mg/kg treatment group ranged from <0.008 μg/mL to 4 μg/mL with trace levels detected in 7 of the 8 animals treated. Trough serum Humira® and Quad-X™ concentrations in 3 mg/kg treatment samples were comparable; however, the functionality of the detected Humira® serum was significantly compromised due to neutralising ADA. The impact of ADA went beyond the simple and rapid clearance of Humira®, as 7/8 serum samples also showed no detectable capacity to neutralise hTNF-α-mediated cytotoxicity in a murine fibrosarcoma (L929) cell assay. The neutralisation capacity of all the VNAR constructs remained unchanged at the end of the experimental period (10 weeks). The data presented in this manuscript goes some way to explain the exciting outcomes of the previously published preclinical in vivo efficacy data, which showed complete control of disease at Quad-X™ concentrations of 0.5 mg/kg, equivalent to 10x the in vivo potency of Humira®. This independent corroboration also validates the robustness and reliability of the assay techniques reported in this current manuscript, and while it comes with the caveat of a mouse study, it does appear to suggest that these particular VNAR constructs, at least, are of low inherent immunogenicity.

Quantification of protein glycation using vibrational spectroscopy

FTIR-ATR and Raman spectroscopy can distinguish between glycated and non-glycated proteins.

Induction of NK Cell Reactivity against B-Cell Acute Lymphoblastic Leukemia by an Fc-Optimized FLT3 Antibody

Antibody-dependent cellular cytotoxicity (ADCC) is a major mechanism by which antitumor antibodies mediate therapeutic efficacy. At present, we evaluate an Fc-optimized (amino acid substitutions S239D/I332E) FLT3 antibody termed 4G8-SDIEM (FLYSYN) in patients with acute myeloid leukemia (NCT02789254). Here we studied the possibility to induce NK cell ADCC against B-cell acute lymphoblastic leukemia (B-ALL) by Fc-optimized FLT3 antibody treatment. Flow cytometric analysis confirmed that FLT3 is widely expressed on B-ALL cell lines and leukemic cells of B-ALL patients. FLT3 expression did not correlate with that of CD20, which is targeted by Rituximab, a therapeutic monoclonal antibody (mAb) employed in B-ALL treatment regimens. Our FLT3 mAb with enhanced affinity to the Fc receptor CD16a termed 4G8-SDIE potently induced NK cell reactivity against FLT3-transfectants, the B-ALL cell line SEM and primary leukemic cells of adult B-ALL patients in a target-antigen dependent manner as revealed by analyses of NK cell activation and degranulation. This was mirrored by potent 4G8-SDIE mediated NK cell ADCC in experiments with FLT3-transfectants, the cell line SEM and primary cells as target cells. Taken together, the findings presented in this study provide evidence that 4G8-SDIE may be a promising agent for the treatment of B-ALL, particularly in CD20-negative cases.