The protection receptor for IgG catabolism is the beta2-microglobulin-containing neonatal intestinal transport receptor

Efgartigimod as a promising add-on therapy for myasthenic crisis: a prospective case series

Introduction

Efgartigimod is effective and well-tolerated in patients with anti-acetylcholine receptor (AChR) antibody-positive generalized myasthenia gravis (MG). However, the therapeutic potential and the safety profile of efgartigimod in myasthenic crisis (MC) remained largely unknown.

Methods

This is an observational, prospective, multicenter, real-world study to follow 2 MC patients who initiated efgartigimod as a first-line rescue therapy and 8 cases who used it as an add-on therapy. Baseline demographic features and immunotherapies were collected, and the MG-activities of daily living (MG-ADL) scale was evaluated every week since efgartigimod treatment for 8 weeks. Additionally, serum IgG and anti-AChR antibody levels and the peripheral CD4+ T lymphocytes were measured before and after one cycle of treatment.

Results

Ten patients with MC were enrolled in the study, including 9 anti-AChR antibody positive and 1 anti-muscle-specific kinase (MuSK) positive. All patients were successfully weaned from the ventilation after receiving efgartigimod treatment, with a length of 10.44 ± 4.30 days. After one cycle of infusions, the MG-ADL score reduced from 15.6 ± 4.4 at the baseline to 3.4 ± 2.2, while the corticosteroid dose was tapered from 55.0 ± 20.7 mg to 26.0 ± 14.1 mg. The proportions of regulatory T cells and naïve T cells (% in CD4+ T) significantly decreased post-efgartigimod treatment (5.48 ± 1.23 vs. 6.90 ± 1.80, P=0.0313, and 34.98 ± 6.47 vs. 43.68 ± 6.54, P=0.0313, respectively).

Conclusion

These findings validated the rapid action of efgartigimod in facilitating the weaning process with a good safety profile in patients with MC.

Development of a predictive algorithm for the efficacy of half-life extension strategies

A challenge in development of peptide and protein therapeutics is rapid elimination from the body, necessitating frequent dosing that may lead to toxicities and/or poor patient compliance. To solve this issue, there has been great investment into half-life extension of rapidly eliminated drugs using approaches such as albumin binding, fusion to albumin or Fc, or conjugation to polyethylene glycol. Despite clinical successes of half-life extension products, no clear relationship has been drawn between properties of drugs and the pharmacokinetic parameters of their half-life extended analogues. In this study, non-compartmentally derived pharmacokinetic parameters (half-life, clearance, volume of distribution) were collected for 186 half-life extended drugs and their unmodified parent molecules. Statistical testing and regression analysis was performed to evaluate relationships between pharmacokinetic parameters and a matrix of variables. Multivariate linear regression models were developed for each of the three pharmacokinetic parameters and model predictions were in good agreement with observed data with r2 values for each parameter being: half-life: 0.879, clearance: 0.820, volume of distribution: 0.937. Significant predictors for each parameter included the corresponding pharmacokinetic parameter of the parent drug and descriptors related to molecular weight. This model represents a useful tool for prediction of the potential benefits of half-life extension.

Cellular Neonatal Fc Receptor Recycling Efficiencies can Differentiate Target-Independent Clearance Mechanisms of Monoclonal Antibodies

In vivo clearance mechanisms of therapeutic monoclonal antibodies (mAbs) encompass both target-mediated and target-independent processes. Two distinct determinants of overall mAb clearance largely separate of target-mediated influences are non-specific cellular endocytosis and subsequent pH-dependent mAb recycling mediated by the neonatal Fc receptor (FcRn), where inter-mAb variability in the efficiency of both processes is observed. Here, we implemented a functional cell-based FcRn recycling assay via Madin-Darby canine kidney type II cells stably co-transfected with human FcRn and its light chain β2-microglobulin. Next, a series of pH-dependent internalization studies using a model antibody demonstrated proper function of the human FcRn complex. We then applied our cellular assays to assess the contribution of both FcRn and non-specific interactions in the cellular turnover for a panel of 8 clinically relevant mAbs exhibiting variable human pharmacokinetic behavior. Our results demonstrate that the interplay of non-specific endocytosis rates, pH-dependent non-specific interactions, and engagement with FcRn all contribute to the overall recycling efficiency of therapeutic monoclonal antibodies. The predictive capacity of our assay approach was highlighted by successful identification of all mAbs within our panel possessing clearance in humans greater than 5 mL/day/kg. These results demonstrate that a combination of cell-based in vitro assays can properly resolve individual mechanisms underlying the overall in vivo recycling efficiency and non-target mediated clearance of therapeutic mAbs.

Advancements in Bullous Pemphigoid Treatment: A Comprehensive Pipeline Update

ABASTRACT

Bullous pemphigoid (BP) is a common autoimmune bullous disease affecting mainly the elderly, with rising incidence due to increased life expectancy. This disease is characterized by tense bullous lesions on normal or erythematous skin, accompanied by pruritus. BP pathogenesis involves autoantibodies against hemidesmosomal proteins BP180 and BP230, leading to detachment at the dermo-epidermal junction as well as blister formation. BP is associated with coexisting comorbidities and drug exposure, and its management often requires high doses or chronic use of systemic glucocorticoids, posing risks of adverse effects. This review focuses on novel treatment options for BP, exploring therapies targeting different immune pathways. Rituximab, a CD20 monoclonal antibody, depletes B-lymphocytes and has shown efficacy in severe cases. Dupilumab, targeting interleukin (IL)-4 receptor α and thus blocking IL-4 and IL-13, downregulates type 2 helper (Th2) responses and has demonstrated promising results. Targeting eosinophil-related molecules using bertilimumab and AKST4290 has yielded positive results in clinical trials. Omalizumab, an immunoglobulin (Ig) E antibody, can reduce disease severity and allows corticosteroid tapering in a number of cases. Complement inhibitors such as nomacopan and avdoralimab are being investigated. IL-17 and IL-23 inhibitors such as secukinumab and tildrakizumab have shown potential in a limited number of case reports. Neonatal Fc receptor antagonists such as efgartigimod are under investigation. Additionally, topical therapies and Janus kinase inhibitors are being explored as potential treatments for BP. These novel therapies offer promising alternatives for managing BP, with potential to improve outcomes and reduce high cumulative doses of systemic corticosteroids and related toxicities. Further research, including controlled clinical trials, is needed to establish their efficacy, safety, and optimal dosing regimens for BP management.

Next generation of multispecific antibody engineering

Multispecific antibodies recognize two or more epitopes located on the same or distinct targets. This added capability through protein design allows these man-made molecules to address unmet medical needs that are no longer possible with single targeting such as with monoclonal antibodies or cytokines alone. However, the approach to the development of these multispecific molecules has been met with numerous road bumps, which suggests that a new workflow for multispecific molecules is required. The investigation of the molecular basis that mediates the successful assembly of the building blocks into non-native quaternary structures will lead to the writing of a playbook for multispecifics. This is a must do if we are to design workflows that we can control and in turn predict success. Here, we reflect on the current state-of-the-art of therapeutic biologics and look at the building blocks, in terms of proteins, and tools that can be used to build the foundations of such a next-generation workflow.

Structural, nonclinical, and clinical features of ozoralizumab: A novel tumour necrosis factor inhibitor

Tumour necrosis factor (TNF) inhibitors are currently the most widely used biological agents to treat rheumatoid arthritis. Ozoralizumab (OZR), a novel TNF inhibitor, is an antibody using variable heavy-chain domains of heavy-chain antibody (VHHs) and became the first VHH drug approved for the treatment of rheumatoid arthritis in September 2022. VHHs isolated from camelid heavy-chain antibodies can bind antigens with a single molecule. OZR is a trivalent VHH that consists of two anti-human TNFα VHHs and one anti-human serum albumin (anti-HSA) VHH. This review summarizes OZR's unique structural characteristics and nonclinical and clinical data. The clinical data outline the pharmacokinetics, efficacy, relationship between efficacy and pharmacokinetics, and safety of OZR, focusing on a Phase II/III confirmatory study (OHZORA trial).

Intravenous immunoglobulin in kidney transplantation: Mechanisms of action, clinical applications, adverse effects, and hyperimmune globulin

Intravenous immunoglobulin (IVIG) has been developed for over 40 years. The mechanisms of action of IVIG are complex and diverse, and there may be multiple mechanisms that combine to influence it. IVIG has been used in kidney transplantation for desensitization, treatment of antibody-mediated rejection, and ABO-incompatible transplantation. and treatment or prevention of some infectious diseases. Hyperimmune globulins such as cytomegalovirus hyperimmune globulin (CMV-IG) and hepatitis B hyperimmune globulin (HBIG) have also been used to protect against cytomegalovirus and hepatitis B virus, respectively. However, IVIG is also associated with some rare but serious adverse effects and some application risks, and clinicians need to weigh the pros and cons and develop individualized treatment programs to benefit more patients. This review will provide an overview of the multiple mechanisms of action, clinical applications, adverse effects, and prophylactic measures of IVIG, and hyperimmune globulin will also be introduced in it.

Serum immunoglobulin and the threshold of Fc receptor-mediated immune activation

Antibodies can mediate immune recruitment or clearance of immune complexes through the interaction of their Fc domain with cellular Fc receptors. Clustering of antibodies is a key step in generating sufficient avidity for efficacious receptor recognition. However, Fc receptors may be saturated with prevailing, endogenous serum immunoglobulin and this raises the threshold by which cellular receptors can be productively engaged. Here, we review the factors controlling serum IgG levels in both healthy and disease states, and discuss how the presence of endogenous IgG is encoded into the functional activation thresholds for low- and high-affinity Fc receptors. We discuss the circumstances where antibody engineering can help overcome these physiological limitations of therapeutic antibodies. Finally, we discuss how the pharmacological control of Fc receptor saturation by endogenous IgG is emerging as a feasible mechanism for the enhancement of antibody therapeutics.

mAb therapy controls CNS-resident lyssavirus infection via a CD4 T cell-dependent mechanism

Infections with rabies virus (RABV) and related lyssaviruses are uniformly fatal once virus accesses the central nervous system (CNS) and causes disease signs. Current immunotherapies are thus focused on the early, pre-symptomatic stage of disease, with the goal of peripheral neutralization of virus to prevent CNS infection. Here, we evaluated the therapeutic efficacy of F11, an anti-lyssavirus human monoclonal antibody (mAb), on established lyssavirus infections. We show that a single dose of F11 limits viral load in the brain and reverses disease signs following infection with a lethal dose of lyssavirus, even when administered after initiation of robust virus replication in the CNS. Importantly, we found that F11-dependent neutralization is not sufficient to protect animals from mortality, and a CD4 T cell-dependent adaptive immune response is required for successful control of infection. F11 significantly changes the spectrum of leukocyte populations in the brain, and the FcRγ-binding function of F11 contributes to therapeutic efficacy. Thus, mAb therapy can drive potent neutralization-independent T cell-mediated effects, even against an established CNS infection by a lethal neurotropic virus.

Response-Adapted Therapy for Newly Diagnosed Multiple Myeloma

PURPOSE OF REVIEW

The development of potent novel agents has improved outcomes for patients with multiple myeloma (MM). Heterogeneity of response to therapy, an expanding arsenal of treatment options, and cost are however major challenges for physicians making treatment decisions. Response-adapted therapy is hence an attractive strategy for sequencing of therapy in MM. Despite its successful application in other haematologic malignancies, response-adapted therapy is yet to become a standard of care for MM. We provide our perspective on response-adapted therapeutic strategies evaluated thus far and how they may be implemented and improved on in treatment algorithms of the future.

RECENT FINDINGS

While older studies suggested that early response based on International Myeloma Working Group response criteria could impact long-term outcomes, recent data have contradicted these findings. The advent of minimal residual disease (MRD) as a powerful prognostic factor in MM has raised the promise of MRD-adapted treatment strategies. The development of more sensitive techniques for paraprotein quantification as well as imaging modalities to detect extramedullary disease is likely to change response assessment in MM. These techniques combined with MRD assessment may provide sensitive and holistic response assessments which could be evaluated in clinical trials. Response-adapted treatment algorithms have the potential to allow an individualised treatment strategy, maximising efficacy, while minimising toxicities and cost. Standardisation of MRD methodology, incorporation of imaging into response assessment, and the optimal management of MRD positive patients are key questions to be addressed in future trials.

FcRN receptor antagonists in the management of myasthenia gravis

Myasthenia gravis (MG) is an autoimmune disorder characterized by autoantibodies specifically directed against proteins located within the postsynaptic membrane of the neuromuscular junction. These pathogenic autoantibodies can be reduced by therapies such as plasma exchange, IVIG infusions and other immunosuppressive agents. However, there are significant side effects associated with most of these therapies. Since there is a better understanding of the molecular structure and the biological properties of the neonatal Fc receptors (FcRn), it possesses an attractive profile in treating myasthenia gravis. FcRn receptors prevent the catabolism of IgG by impeding their lysosomal degradation and facilitating their extracellular release at physiological pH, consequently extending the IgG half-life. Thus, the catabolism of IgG can be enhanced by blocking the FcRn, leading to outcomes similar to those achieved through plasma exchange with no significant safety concerns. The available studies suggest that FcRn holds promise as a versatile therapeutic intervention, capable of delivering beneficial outcomes in patients with distinct characteristics and varying degrees of MG severity. Efgartigimod is already approved for the treatment of generalized MG, rozanolixizumab is under review by health authorities, and phase 3 trials of nipocalimab and batoclimab are underway. Here, we will review the available data on FcRn therapeutic agents in the management of MG.

The Role of Cytokines in Neutrophil Development, Tissue Homing, Function and Plasticity in Health and Disease

Neutrophils are crucial innate immune cells and comprise 50-70% of the white blood cell population under homeostatic conditions. Upon infection and in cancer, blood neutrophil numbers significantly increase because of the secretion of various chemo- and cytokines by, e.g., leukocytes, pericytes, fibroblasts and endothelial cells present in the inflamed tissue or in the tumor microenvironment (TME). The function of neutrophils in cancer has recently gained considerable attention, as they can exert both pro- and anti-tumorigenic functions, dependent on the cytokine milieu present in the TME. Here, we review the effect of cytokines on neutrophil development, tissue homing, function and plasticity in cancer and autoimmune diseases as well as under physiological conditions in the bone marrow, bloodstream and various organs like the spleen, kidney, liver, lung and lymph nodes. In addition, we address several promising therapeutic options, such as cytokine therapy, immunocytokines and immunotherapy, which aim to exploit the anti-tumorigenic potential of neutrophils in cancer treatment or block excessive neutrophil-mediated inflammation in autoimmune diseases.

Barriers for orally inhaled therapeutic antibodies

INTRODUCTION

Respiratory diseases represent a worldwide health issue. The recent Sars-CoV-2 pandemic, the burden of lung cancer, and inflammatory respiratory diseases urged the development of innovative therapeutic solutions. In this context, therapeutic antibodies (Abs) offer a tremendous opportunity to benefit patients with respiratory diseases. Delivering Ab through the airways has been demonstrated to be relevant to improve their therapeutic index. However, few inhaled Abs are on the market.

AREAS COVERED

This review describes the different barriers that may alter the fate of inhaled therapeutic Abs in the lungs at steady state. It addresses both physical and biological barriers and discusses the importance of taking into consideration the pathological changes occurring during respiratory disease, which may reinforce these barriers.

EXPERT OPINION

The pulmonary route remains rare for delivering therapeutic Abs, with few approved inhaled molecules, despite promising evidence. Efforts must focus on the intertwined barriers associated with lung diseases to develop appropriate Ab-formulation-device combo, ensuring optimal Ab deposition in the respiratory tract. Finally, randomized controlled clinical trials should be carried out to establish inhaled Ab therapy as prominent against respiratory diseases.

IgA antibody immunotherapy targeting GD2 is effective in preclinical neuroblastoma models

BACKGROUND

Immunotherapy targeting GD2 is very effective against high-risk neuroblastoma, though administration of anti-GD2 antibodies induces severe and dose-limiting neuropathic pain by binding GD2-expressing sensory neurons. Previously, the IgG1 ch14.18 (dinutuximab) antibody was reformatted into the IgA1 isotype, which abolishes neuropathic pain and induces efficient neutrophil-mediated antibody-dependent cellular cytotoxicity (ADCC) via activation of the Fc alpha receptor (FcαRI/CD89).

METHODS

To generate an antibody suitable for clinical application, we engineered an IgA molecule (named IgA3.0 ch14.18) with increased stability, mutated glycosylation sites and substituted free (reactive) cysteines. The following mutations were introduced: N45.2G and P124R (CH1 domain), C92S, N120T, I121L and T122S (CH2 domain) and a deletion of the tail piece P131-Y148 (CH3 domain). IgA3.0 ch14.18 was evaluated in binding assays and in ADCC and antibody-dependent cellular phagocytosis (ADCP) assays with human, neuroblastoma patient and non-human primate effector cells. We performed mass spectrometry analysis of N-glycans and evaluated the impact of altered glycosylation in IgA3.0 ch14.18 on antibody half-life by performing pharmacokinetic (PK) studies in mice injected intravenously with 5 mg/kg antibody solution. A dose escalation study was performed to determine in vivo efficacy of IgA3.0 ch14.18 in an intraperitoneal mouse model using 9464D-GD2 neuroblastoma cells as well as in a subcutaneous human xenograft model using IMR32 neuroblastoma cells. Binding assays and PK studies were compared with one-way analysis of variance (ANOVA), ADCC and ADCP assays and in vivo tumor outgrowth with two-way ANOVA followed by Tukey's post-hoc test.

RESULTS

ADCC and ADCP assays showed that particularly neutrophils and macrophages from healthy donors, non-human primates and patients with neuroblastoma are able to kill neuroblastoma tumor cells efficiently with IgA3.0 ch14.18. IgA3.0 ch14.18 contains a more favorable glycosylation pattern, corresponding to an increased antibody half-life in mice compared with IgA1 and IgA2. Furthermore, IgA3.0 ch14.18 penetrates neuroblastoma tumors in vivo and halts tumor outgrowth in both 9464D-GD2 and IMR32 long-term tumor models.

CONCLUSIONS

IgA3.0 ch14.18 is a promising new therapy for neuroblastoma, showing (1) increased half-life compared to natural IgA antibodies, (2) increased protein stability enabling effortless production and purification, (3) potent CD89-mediated tumor killing in vitro by healthy subjects and patients with neuroblastoma and (4) antitumor efficacy in long-term mouse neuroblastoma models.

The therapeutic age of the neonatal Fc receptor

IgGs are essential soluble components of the adaptive immune response that evolved to protect the body from infection. Compared with other immunoglobulins, the role of IgGs is distinguished and enhanced by their high circulating levels, long half-life and ability to transfer from mother to offspring, properties that are conferred by interactions with neonatal Fc receptor (FcRn). FcRn binds to the Fc portion of IgGs in a pH-dependent manner and protects them from intracellular degradation. It also allows their transport across polarized cells that separate tissue compartments, such as the endothelium and epithelium. Further, it is becoming apparent that FcRn functions to potentiate cellular immune responses when IgGs, bound to their antigens, form IgG immune complexes. Besides the protective role of IgG, IgG autoantibodies are associated with numerous pathological conditions. As such, FcRn blockade is a novel and effective strategy to reduce circulating levels of pathogenic IgG autoantibodies and curtail IgG-mediated diseases, with several FcRn-blocking strategies on the path to therapeutic use. Here, we describe the current state of knowledge of FcRn-IgG immunobiology, with an emphasis on the functional and pathological aspects, and an overview of FcRn-targeted therapy development.

Fc-competent multispecific PDL-1/TIGIT/LAG-3 antibodies potentiate superior anti-tumor T cell response

The landscape of current cancer immunotherapy is dominated by antibodies targeting PD-1/PD-L1 and CTLA-4 that have transformed cancer therapy, yet their efficacy is limited by primary and acquired resistance. The blockade of additional immune checkpoints, especially TIGIT and LAG-3, has been extensively explored, but so far only a LAG-3 antibody has been approved for combination with nivolumab to treat unresectable or metastatic melanoma. Here we report the development of a PDL1 × TIGIT bi-specific antibody (bsAb) GB265, a PDL1 × LAG3 bsAb GB266, and a PDL1 × TIGIT × LAG3 tri-specific antibody (tsAb) GB266T, all with intact Fc function. In in vitro cell-based assays, these antibodies promote greater T cell expansion and tumor cell killing than benchmark antibodies and antibody combinations in an Fc-dependent manner, likely by facilitating T cell interactions (bridging) with cancer cells and monocytes, in addition to blocking immune checkpoints. In animal models, GB265 and GB266T antibodies outperformed benchmarks in tumor suppression. This study demonstrates the potential of a new generation of multispecific checkpoint inhibitors to overcome resistance to current monospecific checkpoint antibodies or their combinations for the treatment of human cancers.

Antibody blockade of Jagged1 attenuates choroidal neovascularization

Antibody-based blocking of vascular endothelial growth factor (VEGF) reduces choroidal neovascularization (CNV) and retinal edema, rescuing vision in patients with neovascular age-related macular degeneration (nAMD). However, poor response and resistance to anti-VEGF treatment occurs. We report that targeting the Notch ligand Jagged1 by a monoclonal antibody reduces neovascular lesion size, number of activated phagocytes and inflammatory markers and vascular leakage in an experimental CNV mouse model. Additionally, we demonstrate that Jagged1 is expressed in mouse and human eyes, and that Jagged1 expression is independent of VEGF signaling in human endothelial cells. When anti-Jagged1 was combined with anti-VEGF in mice, the decrease in lesion size exceeded that of either antibody alone. The therapeutic effect was solely dependent on blocking, as engineering antibodies to abolish effector functions did not impair the therapeutic effect. Targeting of Jagged1 alone or in combination with anti-VEGF may thus be an attractive strategy to attenuate CNV-bearing diseases.

Efficacy of intravenous immunoglobulin (IVIg) on COVID-19-related neurological disorders over the last 2 years: an up-to-date narrative review

Introduction

Among the clinical manifestations of SARS-CoV-2 infection, neurological features have been commonly reported and the state-of-the-art technique suggests several mechanisms of action providing a pathophysiological rationale for central and peripheral neurological system involvement. However, during the 1st months of the pandemic, clinicians were challenged to find the best therapeutic options to treat COVID-19-related neurological conditions.

Methods

We explored the indexed medical literature in order to answer the question of whether IVIg could be included as a valid weapon in the therapeutic arsenal against COVID-19-induced neurological disorders.

Results

Virtually, all reviewed studies were in agreement of detecting an acceptable to great efficacy upon IVIg employment in neurological diseases, with no or mild adverse effects. In the first part of this narrative review, the interaction of SARS-CoV-2 with the nervous system has been discussed and the IVIg mechanisms of action were reviewed. In the second part, we collected scientific literature data over the last 2 years to discuss the use of IVIg therapy in different neuro-COVID conditions, thus providing a summary of the treatment strategies and key findings.

Discussion

Intravenous immunoglobulin (IVIg) therapy is a versatile tool with multiple molecular targets and mechanisms of action that might respond to some of the suggested effects of infection through inflammatory and autoimmune responses. As such, IVIg therapy has been used in several COVID-19-related neurological diseases, including polyneuropathies, encephalitis, and status epilepticus, and results have often shown improvement of symptoms, thus suggesting IVIg treatment to be safe and effective.

Efficacy and pharmacokinetics of ozoralizumab, an anti-TNFα NANOBODY® compound, in patients with rheumatoid arthritis: 52-week results from the OHZORA and NATSUZORA trials

INTRODUCTION

Ozoralizumab (OZR), a tumor necrosis factor alpha (TNFα) inhibitor, is a NANOBODY^® compound that binds to TNFα and human serum albumin. The main objective of this study was to analyze the pharmacokinetics (PK) of the drug and its correlation with clinical efficacy in patients with rheumatoid arthritis (RA).

METHODS

Efficacy data were analyzed from the OHZORA trial, in which OZR 30 or 80 mg was administered to Japanese patients with RA at 4-week intervals for 52 weeks in combination with methotrexate (MTX; n = 381), and the NATSUZORA trial, in which OZR 30 or 80 mg was administered without concomitant MTX (n = 140). Effects of patient baseline characteristics and anti-drug antibodies (ADAs) on the PK and efficacy of OZR were investigated, and a post hoc analysis of PK effects on drug efficacy was performed.

RESULTS

The maximum plasma concentration (C_max) was reached in 6 days in both the 30 and 80 mg groups, with an elimination half-life of 18 days. The C_max and area under the plasma concentration-time curve increased in a dose-dependent manner, and the trough concentration reached steady state by week 16. The exposure of OZR correlated negatively with patient body weight and was not affected by other patient baseline characteristics. Effects of ADAs on the exposure and efficacy of OZR were limited in both trials. However, antibodies that neutralize the binding to TNFα had some effect on the exposure and efficacy of OZR in the NATSUZORA trial. The receiver operating characteristic analysis of the effect of trough concentration on the American College of Rheumatology 20% and 50% improvement rates was retrospectively performed, and a cutoff trough concentration of approximately 1 μg/mL at week 16 was obtained in both trials. The efficacy indicators in the subgroup with trough concentration ≥ 1 μg/mL were higher than those in the < 1 μg/mL subgroup at week 16, while no clear cutoff was obtained at week 52 in both trials.

CONCLUSIONS

OZR showed a long half-life and favorable PK properties. A post hoc analysis suggested sustained efficacy independent of trough concentration by subcutaneous administration of OZR 30 mg at 4-week intervals for 52 weeks.

TRIAL REGISTRATION

JapicCTI, OHZORA trial: JapicCTI-184029, registration date July 9, 2018; NATSUZORA trial: JapicCTI-184031, registration date July 9, 2018.

Bullous pemphigoid-What do we know about the most recent therapies?

INTRODUCTION

Bullous pemphigoid (BP) is the most common subtype of autoimmune blistering diseases that primarily affects the elderly and is classically defined by the presence of IgG and/or complement C3 against the BP180 and BP230 hemidesmosome proteins. However, most recent studies have introduced the role of specific eosinophil receptors and chemokine mediators in the pathogenesis of BP which are helpful in identifying new targets for future treatments.

AREAS COVERED

This review will focus on the involvement of eosinophils in BP, including the processes that lead to their recruitment, activation, and regulation. Subsequently, covering new therapeutic options in relation to the role of eosinophils. Eotaxin enhances the recruitment of eosinophils in BP, with CCR3 chemoreceptor that is expressed on eosinophils being identified as a key binding site for eotaxin-1. The pathogenic role of IgE and IL-4 in BP is corroborated by successful treatments with Omalizumab and Dupilumab, respectively. IL-5, IL-17 and IL-23 inhibitors may be effective given their roles in promoting eosinophilia.

EXPERT OPINION

Further research into inhibitors of eotaxin, IL-4, IL-5, IL-17, IL-23, CCR3, and specific complement factors are warranted as preliminary studies have largely identified success in treating BP with these agents. Learning from novel treatments for other IgG-mediated autoimmune diseases may be beneficial.

The Fab region of IgG impairs the internalization pathway of FcRn upon Fc engagement

Binding to the neonatal Fc receptor (FcRn) extends serum half-life of IgG, and antagonizing this interaction is a promising therapeutic approach in IgG-mediated autoimmune diseases. Fc-MST-HN, designed for enhanced FcRn binding capacity, has not been evaluated in the context of a full-length antibody, and the structural properties of the attached Fab regions might affect the FcRn-mediated intracellular trafficking pathway. Here we present a comprehensive comparative analysis of the IgG salvage pathway between two full-size IgG1 variants, containing wild type and MST-HN Fc fragments, and their Fc-only counterparts. We find no evidence of Fab-regions affecting FcRn binding in cell-free assays, however, cellular assays show impaired binding of full-size IgG to FcRn, which translates into improved intracellular FcRn occupancy and intracellular accumulation of Fc-MST-HN compared to full size IgG1-MST-HN. The crystal structure of Fc-MST-HN in complex with FcRn provides a plausible explanation why the Fab disrupts the interaction only in the context of membrane-associated FcRn. Importantly, we find that Fc-MST-HN outperforms full-size IgG1-MST-HN in reducing IgG levels in cynomolgus monkeys. Collectively, our findings identify the cellular membrane context as a critical factor in FcRn biology and therapeutic targeting.

Extending the performance of FcRn and FcγRIIIa affinity liquid chromatography for protein biopharmaceuticals

Affinity liquid chromatography using FcRn and FcγRIIIa columns can provide important information on the drug effector functions and the unique PK/PD properties of therapeutic mAbs. In this study, we propose a unique strategy to improve the performance of affinity chromatography by applying pH-gradient programs that incorporate multi-isocratic and negative gradient segments. These alternative gradient programs are known to greatly improve the separation of large solutes that follow a "bind-and-elute" type retention behavior. First, judicious optimization of the mobile phase compositions was performed to obtain a linear pH response. Then, with the developed strategy using multi-isocratic analysis conditions, the FcRn affinity separation selectivity for the analysis of oxidized mAb species was greatly improved. Furthermore, the introduction of negative gradient segments after each eluted peak improved the resolution between multiple glycosylated mAb species on the FcγRIIIa column. Therefore, this work provides a new strategy to improve the performance of affinity chromatography with mAb species, and could assist in the development of more accurate binding assays for important critical quality attributes related to FcRn and FcγRIIIa binding.

Toward Understanding How Staphylococcal Protein A Inhibits IgG-Mediated Phagocytosis

IgG molecules are crucial for the human immune response against bacterial infections. IgGs can trigger phagocytosis by innate immune cells, like neutrophils. To do so, IgGs should bind to the bacterial surface via their variable Fab regions and interact with Fcγ receptors and complement C1 via the constant Fc domain. C1 binding to IgG-labeled bacteria activates the complement cascade, which results in bacterial decoration with C3-derived molecules that are recognized by complement receptors on neutrophils. Next to FcγRs and complement receptors on the membrane, neutrophils also express the intracellular neonatal Fc receptor (FcRn). We previously reported that staphylococcal protein A (SpA), a key immune-evasion protein of Staphylococcus aureus, potently blocks IgG-mediated complement activation and killing of S. aureus by interfering with IgG hexamer formation. SpA is also known to block IgG-mediated phagocytosis in absence of complement, but the mechanism behind it remains unclear. In this study, we demonstrate that SpA blocks IgG-mediated phagocytosis and killing of S. aureus and that it inhibits the interaction of IgGs with FcγRs (FcγRIIa and FcγRIIIb, but not FcγRI) and FcRn. Furthermore, our data show that multiple SpA domains are needed to effectively block IgG1-mediated phagocytosis. This provides a rationale for the fact that SpA from S. aureus contains four to five repeats. Taken together, our study elucidates the molecular mechanism by which SpA blocks IgG-mediated phagocytosis and supports the idea that in addition to FcγRs, the intracellular FcRn is also prevented from binding IgG by SpA.

Monoclonal Antibody Engineering and Design to Modulate FcRn Activities: A Comprehensive Review

Understanding the biological mechanisms underlying the pH-dependent nature of FcRn binding, as well as the various factors influencing the affinity to FcRn, was concurrent with the arrival of the first recombinant IgG monoclonal antibodies (mAbs) and IgG Fc-fusion proteins in clinical practice. IgG Fc–FcRn became a central subject of interest for the development of these drugs for the comfort of patients and good clinical responses. In this review, we describe (i) mAb mutations close to and outside the FcRn binding site, increasing the affinity for FcRn at acidic pH and leading to enhanced mAb half-life and biodistribution, and (ii) mAb mutations increasing the affinity for FcRn at acidic and neutral pH, blocking FcRn binding and resulting, in vivo, in endogenous IgG degradation. Mutations modifying FcRn binding are discussed in association with pH-dependent modulation of antigen binding and (iii) anti-FcRn mAbs, two of the latest innovations in anti-FcRn mAbs leading to endogenous IgG depletion. We discuss the pharmacological effects, the biological consequences, and advantages of targeting IgG–FcRn interactions and their application in human therapeutics.

Avidity in antibody effector functions and biotherapeutic drug design

Antibodies are the cardinal effector molecules of the immune system and are being leveraged with enormous success as biotherapeutic drugs. A key part of the adaptive immune response is the production of an epitope-diverse, polyclonal antibody mixture that is capable of neutralizing invading pathogens or disease-causing molecules through binding interference and by mediating humoral and cellular effector functions. Avidity - the accumulated binding strength derived from the affinities of multiple individual non-covalent interactions - is fundamental to virtually all aspects of antibody biology, including antibody-antigen binding, clonal selection and effector functions. The manipulation of antibody avidity has since emerged as an important design principle for enhancing or engineering novel properties in antibody biotherapeutics. In this Review, we describe the multiple levels of avidity interactions that trigger the overall efficacy and control of functional responses in both natural antibody biology and their therapeutic applications. Within this framework, we comprehensively review therapeutic antibody mechanisms of action, with particular emphasis on engineered optimizations and platforms. Overall, we describe how affinity and avidity tuning of engineered antibody formats are enabling a new wave of differentiated antibody drugs with tailored properties and novel functions, promising improved treatment options for a wide variety of diseases.

Case Report: Prompt Response to Savolitinib in a Case of Advanced Gastric Cancer With Bone Marrow Invasion and MET Abnormalities

Gastric cancer is one of the most common malignant tumors and patients show a short survival, those combined with bone marrow invasion have a median survival of only 37 days. Here we reported the treatment of a 47-year-old male with advanced gastric cancer and complicated with bone marrow invasion and extensive metastases, who did not tolerate chemotherapy, under monotherapy with savolitinib, a MET receptor tyrosine kinase inhibitor. Before treatment, the patient was in severe pain and presented with thrombocytopenia and hemorrhagic anemia. Savolitinib was given based on amplification and rearrangement of the MET gene in his tumor. After savolitinib treatment, the patient’s condition promptly improved, efficacy evaluation indicated partial remission, and the patient was alive and remained progression-free at 15 weeks at the time of reporting. No obvious adverse reactions occurred. Besides, another case of a female gastric cancer patient with MET amplification who received savolitinib monotherapy as a third-line treatment that remained progression-free at 12 weeks was also reported. This report provides a new reference for understanding MET abnormalities in gastric cancer and offers a possibility for future application of MET tyrosine kinase inhibitors in the therapy of gastric cancer with MET abnormalities. Also, it suggests that sequencing of MET can be considered a routine target in advanced gastric cancer patients.

Impact of Pharmacokinetic and Pharmacodynamic Properties of Monoclonal Antibodies in the Management of Psoriasis

The treatment of psoriasis has been revolutionized by the emergence of biological therapies. Monoclonal antibodies (mAb) generally have complex pharmacokinetic (PK) properties with nonlinear distribution and elimination. In recent years, several population pharmacokinetic/pharmacodynamic (PK/PD) models capable of describing different types of mAb have been published. This study aims to summarize the findings of a literature search about population PK/PD modeling and therapeutic drug monitoring (TDM) of mAb in psoriasis. A total of 22 articles corresponding to population PK/PD models of tumor necrosis factor (TNF)-α inhibitors (adalimumab and golimumab), interleukin (IL)-23 inhibitors (guselkumab, tildrakizumab, and risankizumab), IL-23/IL-12 inhibitor (ustekinumab), and IL-17 inhibitors (secukinumab, ixekizumab, and brodalumab) were collected. A summary of the clinical trials conducted so far in psoriasis was included, together with the current structural population PK and PD models. The most significant and clinical covariates were body weight (BW) and the presence of immunogenicity on clearance (CL). The lack of consensus on PK/PD relationships has prevented establishing an adequate dosage and, therefore, accentuates the need for TDM in psoriasis.

Short FcRn-Binding Peptides Enable Salvage and Transcytosis of scFv Antibody Fragments

Therapeutic antibodies have become one of the most widely used classes of biotherapeutics due to their unique antigen specificity and their ability to be engineered against diverse disease targets. There is significant interest in utilizing truncated antibody fragments as therapeutics, as their small size affords favorable properties such as increased tumor penetration as well as the ability to utilize lower-cost prokaryotic production methods. Their small size and simple architecture, however, also lead to rapid blood clearance, limiting the efficacy of these potentially powerful therapeutics. A common approach to circumvent these limitations is to enable engagement with the half-life extending neonatal Fc receptor (FcRn). This is usually achieved via fusion with a large Fc domain, which negates the benefits of the antibody fragment's small size. In this work, we show that modifying antibody fragments with short FcRn-binding peptide domains that mimic native IgG engagement with FcRn enables binding and FcRn-mediated recycling and transmembrane transcytosis in cell-based assays. Further, we show that rational, single amino acid mutations to the peptide sequence have a significant impact on the receptor-mediated function and investigate the underlying structural basis for this effect using computational modeling. Finally, we report the identification of a short peptide from human serum albumin that enables FcRn-mediated function when grafted onto a single-chain variable fragment (scFv) scaffold, establishing an approach for the rational selection of short-peptide domains from full-length proteins that could enable the transfer of non-native functions to small recombinant proteins without significantly impacting their size or structure.

Mass-Fix better predicts for PFS and OS than standard methods among multiple myeloma patients participating on the STAMINA trial (BMT CTN 0702 /07LT)

Measuring response among patients with multiple myeloma is essential for the care of patients. Deeper responses are associated with better progression free survival (PFS) and overall survival (OS). To test the hypothesis that Mass-Fix, a mass spectrometry-based means to detect monoclonal proteins, is superior to existing methodologies to predict for survival outcomes, samples from the STAMINA trial (NCT01109004), a trial comparing three transplant approaches, were employed. Samples from 575 patients from as many as three time points (post-induction [post-I; pre-maintenance [pre-M]; 1 year post enrollment [1YR]) were tested when available. Four response parameters were assessed: Mass-Fix, serum immunofixation, complete response, and measurable residual disease (MRD) by next generation flow cytometry. Of the four response measures, only MRD and Mass-Fix predicted for PFS and OS at multiple testing points on multivariate analyses. Although MRD drove Mass-Fix from the model for PFS at post-I and pre-M, 1YR Mass-Fix was independent of 1YR MRD. For OS, the only prognostic pre-I measure was Mass-Fix, and the only 1YR measures that were prognostic on multivariate analysis were 1YR MRD and 1YR Mass-Fix. SIFE and CR were not. Mass-Fix is a powerful means to track response.

Phagocytosis by an HIV antibody is associated with reduced viremia irrespective of enhanced complement lysis

Increasingly, antibodies are being used to treat and prevent viral infections. In the context of HIV, efficacy is primarily attributed to dose-dependent neutralization potency and to a lesser extent Fc-mediated effector functions. It remains unclear whether augmenting effector functions of broadly neutralizing antibodies (bNAbs) may improve their clinical potential. Here, we use bNAb 10E8v4 targeting the membrane external proximal region (MPER) to examine the role of antibody-mediated effector and complement (C’) activity when administered prophylactically against SHIV challenge in rhesus macaques. With sub-protective dosing, we find a 78–88% reduction in post-acute viremia that is associated with 10E8v4-mediated phagocytosis acting at the time of challenge. Neither plasma nor tissue viremic outcomes in vivo is improved with an Fc-modified variant of 10E8v4 enhanced for C’ functions as determined in vitro. These results suggest that effector functions inherent to unmodified 10E8v4 contribute to efficacy against SHIV_SF162P3 in the absence of plasma neutralizing titers, while C’ functions are dispensable in this setting, informing design of bNAb modifications for improving protective efficacy.

While antibodies neutralize HIV via Fab recognition of viral surface antigens, antibody Fc domains mediate effector functions, including antibody-dependent cellular phagocytosis (ADCP) and cytotoxicity (ADCC), and complement (C') activity. Here, Spencer et al. modify bNAb 10E8v4 to enhance C'-mediated potency in SHIV challenged rhesus macaques to probe its function in protection, showing that in the absence of neutralization, enhancing C' activities in vitro adds no value toward reducing viremia in either blood or tissue.

Antibody bivalency improves antiviral efficacy by inhibiting virion release independently of Fc gamma receptors

Across the animal kingdom, multivalency discriminates antibodies from all other immunoglobulin superfamily members. The evolutionary forces conserving multivalency above other structural hallmarks of antibodies remain, however, incompletely defined. Here, we engineer monovalent either Fc-competent or -deficient antibody formats to investigate mechanisms of protection of neutralizing antibodies (nAbs) and non-neutralizing antibodies (nnAbs) in virus-infected mice. Antibody bivalency enables the tethering of virions to the infected cell surface, inhibits the release of virions in cell culture, and suppresses viral loads in vivo independently of Fc gamma receptor (FcγR) interactions. In return, monovalent antibody formats either do not inhibit virion release and fail to protect in vivo or their protective efficacy is largely FcγR dependent. Protection in mice correlates with virus-release-inhibiting activity of nAb and nnAb rather than with their neutralizing capacity. These observations provide mechanistic insights into the evolutionary conservation of antibody bivalency and help refining correlates of nnAb protection for vaccine development.

Human IgE does not bind to human FcRn

The neonatal Fc receptor (FcRn) is known to mediate placental transfer of IgG from mother to unborn. IgE is widely known for triggering immune responses to environmental antigens. Recent evidence suggests FcRn-mediated transplacental passage of IgE during pregnancy. However, direct interaction of FcRn and IgE was not investigated. Here, we compared binding of human IgE and IgG variants to recombinant soluble human FcRn with β2-microglobulin (sFcRn) in surface plasmon resonance (SPR) at pH 7.4 and pH 6.0. No interaction was found between human IgE and human sFcRn. These results imply that FcRn can only transport IgE indirectly, and thereby possibly transfer allergenic sensitivity from mother to fetus.

Non-human primates in the PKPD evaluation of biologics: Needs and options to reduce, refine, and replace. A BioSafe White Paper

Monoclonal antibodies (mAbs) deliver great benefits to patients with chronic and/or severe diseases thanks to their strong specificity to the therapeutic target. As a result of this specificity, non-human primates (NHP) are often the only preclinical species in which therapeutic antibodies cross-react with the target. Here, we highlight the value and limitations that NHP studies bring to the design of safe and efficient early clinical trials. Indeed, data generated in NHPs are integrated with in vitro information to predict the concentration/effect relationship in human, and therefore the doses to be tested in first-in-human trials. The similarities and differences in the systems defining the pharmacokinetics and pharmacodynamics (PKPD) of mAbs in NHP and human define the nature and the potential of the preclinical investigations performed in NHPs. Examples have been collated where the use of NHP was either pivotal to the design of the first-in-human trial or, inversely, led to the termination of a project prior to clinical development. The potential impact of immunogenicity on the results generated in NHPs is discussed. Strategies to optimize the use of NHPs for PKPD purposes include the addition of PD endpoints in safety assessment studies and the potential re-use of NHPs after non-terminal studies or cassette dosing several therapeutic agents of interest. Efforts are also made to reduce the use of NHPs in the industry through the use of in vitro systems, alternative in vivo models, and in silico approaches. In the case of prediction of ocular PK, the body of evidence gathered over the last two decades renders the use of NHPs obsolete. Expert perspectives, advantages, and pitfalls with these alternative approaches are shared in this review.

Antibody variable sequences have a pronounced effect on cellular transport and plasma half-life

Monoclonal IgG antibodies are the fastest growing class of biologics, but large differences exist in their plasma half-life in humans. Thus, to design IgG antibodies with favorable pharmacokinetics, it is crucial to identify the determinants of such differences. Here, we demonstrate that the variable region sequences of IgG antibodies greatly affect cellular uptake and subsequent recycling and rescue from intracellular degradation by endothelial cells. When the variable sequences are masked by the cognate antigen, it influences both their transport behavior and binding to the neonatal Fc receptor (FcRn), a key regulator of IgG plasma half-life. Furthermore, we show how charge patch differences in the variable domains modulate both binding and transport properties and that a short plasma half-life, due to unfavorable charge patches, may partly be overcome by Fc-engineering for improved FcRn binding.

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IgG variable region sequences greatly affect cellular uptake and recycling

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Variable region charge patches affect FcRn binding and transport

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The presence of cognate antigen modulates cellular transport and FcRn binding

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Fc-engineering for improved FcRn binding can overcome unfavorable charge patches

Colostrogenesis: Role and Mechanism of the Bovine Fc Receptor of the Neonate (FcRn)

Colostrogenesis is a separate and unique phase of mammary epithelial cell activity occurring in the weeks before parturition and rather abruptly ending after birth in the bovine. It has been the focus of research to define what controls this process and how it produces high concentrations of specific biologically active components important for the neonate. In this review we consider colostrum composition and focus upon components that appear in first milked colostrum in concentrations exceeding that in blood serum. The Fc Receptor of the Neonate (FcRn) is recognized as the major immunoglobulin G (IgG) and albumin binding protein that accounts for the proteins' long half-lives. We integrate the action of the pinocytotic (fluid phase) uptake of extracellular components and merge them with FcRn in sorting endosomes. We define and explore the means of binding, sorting, and the transcytotic delivery of IgG1 while recycling IgG2 and albumin. We consider the means of releasing the ligands from the receptor within the endosome and describe a new secretion mechanism of cargo release into colostrum without the appearance of FcRn itself in colostrum. We integrate the insulin-like growth factor family, some of which are highly concentrated bioactive components of colostrum, with the mechanisms related to FcRn endosome action. In addition to secretion, we highlight the recent findings of a role of the FcRn in phagocytosis and antigen presentation and relate its significant and abrupt change in cellular location after parturition to a role in the prevention and resistance to mastitis infections.

IgG regulation through FcRn blocking: A novel mechanism for the treatment of myasthenia gravis

The neonatal Fc receptor (FcRn) is an MHC class I-like molecule that is widely distributed in mammalian organs, tissues, and cells. FcRn is critical to maintaining immunoglobulin G (IgG) and albumin levels through rescuing these molecules from lysosomal degradation. IgG autoantibodies are associated with many autoimmune diseases, including myasthenia gravis (MG), a rare neuromuscular autoimmune disease that causes debilitating and, in its generalized form (gMG), potentially life-threatening muscle weakness. IgG autoantibodies are directly pathogenic in MG and target neuromuscular junction proteins, causing neuromuscular transmission failure. Treatment approaches that reduce autoantibody levels, such as therapeutic plasma exchange and intravenous immunoglobulin, have been shown to be effective for gMG patients but are not indicated as ongoing maintenance therapies and can be associated with burdensome side effects. Agents that block FcRn-mediated recycling of IgG represent a rational and promising approach for the treatment of gMG. Blocking FcRn allows targeted reduction of all IgG subtypes without decreasing concentrations of other Ig isotypes; therefore, FcRn blocking could be a safe and effective treatment strategy for a broad population of gMG patients. Several FcRn-blocking antibodies and one antibody Fc fragment have been developed and are currently in various stages of clinical development. This article describes the mechanism of FcRn blockade as a novel approach for IgG-mediated disease therapy and reviews promising clinical data using such FcRn blockers for the treatment of gMG.

"Ways in which the neonatal Fc-receptor is involved in autoimmunity"

Since the neonatal IgG Fc receptor (FcRn) was discovered, its role has evolved from immunoglobulin recycling and biodistribution to antigen presentation and immune complex routing, bringing it to the center of both humoral and cellular immune responses. FcRn is thus involved in the pathophysiology of immune-related diseases such as cancer, infection, and autoimmune disorders. This review focuses on the role of FcRn in autoimmunity, based on the available data from both animal models and human studies. The knowledge concerning ways in which FcRn is involved in autoimmune response has led to the development of inhibitors for the treatment of autoimmune diseases, also described here. Up to date, the literature remains scarce, shedding light on the need for further studies to fully understand the various pathophysiological roles of this unique receptor.

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FcRn is an intracellular receptor with a key role in IgG and immune complex management.

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FcRn-targeting therapies are a promising way of treatment in antibodies mediated diseases.

Engineered Multivalent Nanobodies Potently and Broadly Neutralize SARS-CoV-2 Variants

The COVID-19 pandemic continues to be a severe threat to human health, especially due to current and emerging SARS-CoV-2 variants with potential to escape humoral immunity developed after vaccination or infection. The development of broadly neutralizing antibodies that engage evolutionarily conserved epitopes on coronavirus spike proteins represents a promising strategy to improve therapy and prophylaxis against SARS-CoV-2 and variants thereof. Herein, a facile multivalent engineering approach is employed to achieve large synergistic improvements in the neutralizing activity of a SARS-CoV-2 cross-reactive nanobody (VHH-72) initially generated against SARS-CoV. This synergy is epitope specific and is not observed for a second high-affinity nanobody against a non-conserved epitope in the receptor-binding domain. Importantly, a hexavalent VHH-72 nanobody retains binding to spike proteins from multiple highly transmissible SARS-CoV-2 variants (B.1.1.7 and B.1.351) and potently neutralizes them. Multivalent VHH-72 nanobodies also display drug-like biophysical properties, including high stability, high solubility, and low levels of non-specific binding. The unique neutralizing and biophysical properties of VHH-72 multivalent nanobodies make them attractive as therapeutics against SARS-CoV-2 variants.

Safety, efficacy, and tolerability of efgartigimod in patients with generalised myasthenia gravis (ADAPT): a multicentre, randomised, placebo-controlled, phase 3 trial

BACKGROUND

There is an unmet need for treatment options for generalised myasthenia gravis that are effective, targeted, well tolerated, and can be used in a broad population of patients. We aimed to assess the safety and efficacy of efgartigimod (ARGX-113), a human IgG1 antibody Fc fragment engineered to reduce pathogenic IgG autoantibody levels, in patients with generalised myasthenia gravis.

METHODS

ADAPT was a randomised, double-blind, placebo-controlled, phase 3 trial done at 56 neuromuscular academic and community centres in 15 countries in North America, Europe, and Japan. Patients aged at least 18 years with generalised myasthenia gravis were eligible to participate in the study, regardless of anti-acetylcholine receptor antibody status, if they had a Myasthenia Gravis Activities of Daily Living (MG-ADL) score of at least 5 (>50% non-ocular), and were on a stable dose of at least one treatment for generalised myasthenia gravis. Patients were randomly assigned by interactive response technology (1:1) to efgartigimod (10 mg/kg) or matching placebo, administered as four infusions per cycle (one infusion per week), repeated as needed depending on clinical response no sooner than 8 weeks after initiation of the previous cycle. Patients, investigators, and clinical site staff were all masked to treatment allocation. The primary endpoint was proportion of acetylcholine receptor antibody-positive patients who were MG-ADL responders (≥2-point MG-ADL improvement sustained for ≥4 weeks) in the first treatment cycle. The primary analysis was done in the modified intention-to-treat population of all acetylcholine receptor antibody-positive patients who had a valid baseline MG-ADL assessment and at least one post-baseline MG-ADL assessment. The safety analysis included all randomly assigned patients who received at least one dose or part dose of efgartigimod or placebo. This trial is registered at ClinicalTrials.gov (NCT03669588); an open-label extension is ongoing (ADAPT+, NCT03770403).

FINDINGS

Between Sept 5, 2018, and Nov 26, 2019, 167 patients (84 in the efgartigimod group and 83 in the placebo group) were enrolled, randomly assigned, and treated. 129 (77%) were acetylcholine receptor antibody-positive. Of these patients, more of those in the efgartigimod group were MG-ADL responders (44 [68%] of 65) in cycle 1 than in the placebo group (19 [30%] of 64), with an odds ratio of 4·95 (95% CI 2·21-11·53, p<0·0001). 65 (77%) of 84 patients in the efgartigimod group and 70 (84%) of 83 in the placebo group had treatment-emergent adverse events, with the most frequent being headache (efgartigimod 24 [29%] vs placebo 23 [28%]) and nasopharyngitis (efgartigimod ten [12%] vs placebo 15 [18%]). Four (5%) efgartigimod-treated patients and seven (8%) patients in the placebo group had a serious adverse event. Three patients in each treatment group (4%) discontinued treatment during the study. There were no deaths.

INTERPRETATION

Efgartigimod was well tolerated and efficacious in patients with generalised myasthenia gravis. The individualised dosing based on clinical response was a unique feature of ADAPT, and translation to clinical practice with longer term safety and efficacy data will be further informed by the ongoing open-label extension.

FUNDING

argenx.

A cell-based FcRn-dependent recycling assay for predictive pharmacokinetic assessment of therapeutic antibodies

Aim: Evaluation of suitable pharmacokinetic properties is critical for successful development of IgG-based biotherapeutics. The prolonged half-lives of IgGs depend on the intracellular trafficking function of neonatal Fc receptor, which rescues internalized IgGs from lysosomal degradation and recycles them back to circulation. Results: Here, we developed a novel cell-based assay to quantify recycling of monoclonal antibodies in a transwell culture system that uses a cell line that stably expresses human neonatal Fc receptor. We tested seven therapeutic antibodies and showed that the recycling output of the assay strongly correlated with the clearance in humans. Conclusion: This recycling assay has potential application as a pharmacokinetic prescreening tool to facilitate development and selection of IgG-based candidate therapeutic monoclonal antibodies.

FcRn as a Transporter for Nasal Delivery of Biologics: A Systematic Review

FcRn plays a major role in regulating immune homeostasis, but it is also able to transport biologics across cellular barriers. The question of whether FcRn could be an efficient transporter of biologics across the nasal epithelial barrier is of particular interest, as it would allow a less invasive strategy for the administration of biologics in comparison to subcutaneous, intramuscular or intravenous administrations, which are often used in clinical practice. A focused systematic review was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. It was registered on the international prospective register of systematic reviews PROSPERO, which helped in identifying articles that met the inclusion criteria. Clinical and preclinical studies involving FcRn and the nasal delivery of biologics were screened, and the risk of bias was assessed across studies using the Oral Health Assessment Tool (OHAT). Among the 12 studies finally included in this systematic review (out of the 758 studies screened), 11 demonstrated efficient transcytosis of biologics through the nasal epithelium. Only three studies evaluated the potential toxicity of biologics’ intranasal delivery, and they all showed that it was safe. This systematic review confirmed that FcRn is expressed in the nasal airway and the olfactory epithelium, and that FcRn may play a role in IgG and/or IgG-derived molecule-transcytosis across the airway epithelium. However, additional research is needed to better characterize the pharmacokinetic and pharmacodynamic properties of biologics after their intranasal delivery.

Association of IgG1 Antibody Clearance with FcγRIIA Polymorphism and Platelet Count in Infliximab-Treated Patients

The FcγRIIA/CD32A is mainly expressed on platelets, myeloid and several endothelial cells. Its affinity is considered insufficient for allowing significant binding of monomeric IgG, while its H131R polymorphism (histidine > arginine at position 131) influences affinity for multimeric IgG2. Platelet FcγRIIA has been reported to contribute to IgG-containing immune-complexe clearance. Given our finding that platelet FcγRIIA actually binds monomeric IgG, we investigated the role of platelets and FcγRIIA in IgG antibody elimination. We used pharmacokinetics analysis of infliximab (IgG1) in individuals with controlled Crohn’s disease. The influence of platelet count and FcγRIIA polymorphism was quantified by multivariate linear modelling. The infliximab half-life increased with R allele number (13.2, 14.4 and 15.6 days for HH, HR and RR patients, respectively). It decreased with increasing platelet count in R carriers: from ≈20 days (RR) and ≈17 days (HR) at 150 × 10⁹/L, respectively, to ≈13 days (both HR and RR) at 350 × 10⁹/L. Moreover, a flow cytometry assay showed that infliximab and monomeric IgG1 bound efficiently to platelet FcγRIIA H and R allotypes, whereas panitumumab and IgG2 bound poorly to the latter. We propose that infliximab (and presumably any IgG1 antibody) elimination is partly due to an unappreciated mechanism dependent on binding to platelet FcγRIIA, which is probably tuned by its affinity for IgG2.

The influence of antibody engineering on Fc conformation and Fc receptor binding properties: Analysis of FcRn-binding engineered antibodies and an Fc fusion protein

Therapeutic immunoglobulin G (IgG) antibodies have comparatively long half-lives because the neonatal Fc receptor (FcRn) binds to the IgG Fc at acidic pH in the endosome and protects IgG from degradation. To further prolong the half-lives, amino acid-substituted antibodies having high affinity to FcRn are being developed, and one such therapeutic antibody (ravulizumab) has been approved. In this study, we investigated the binding property to FcγR and the conformation of seven FcRn affinity-modulated adalimumab variants to clarify the impact of the amino acid substitutions on the function and conformation of IgG Fc. The amino acid substitutions in T254-P261 caused a change in deuterium uptake into some regions of Fc in HDX-MS analysis, but those at T311, M432 and N438 did not cause such a change. The conformations around F245-L255 (FLFPPKPKDTL) were particularly influenced by the amino acid substitution in M256-P261, and the conformational changes of this region were correlated with the decrease of the affinity to FcγRIIIa. Additionally, we investigated the conformational difference of Fc between a Fc fusion protein (etanercept) and a native IgG (adalimumab). Although the Fc fusion proteins were expected to have similar FcRn affinity to IgGs, the affinity of etanercept to FcRn was lower than that of adalimumab, and its half-life was shorter than those of the IgG antibodies. Differences in deuterium uptakes were observed in the two regions where they were also detected in the adalimumab variants, and the conformational differences appeared to be an important factor for the low FcRn affinity of etanercept.

Model-Based Selection and Recommendation for Subcutaneous Abatacept Dose in Patients With Polyarticular Juvenile Idiopathic Arthritis

The selective T-cell costimulation modulator abatacept is approved for treatment of adult rheumatoid arthritis (RA) and polyarticular juvenile idiopathic arthritis (pJIA; 6-17 years [intravenous] and 2-17 years [subcutaneous]). An extrapolation approach was taken to determine subcutaneous weight-tiered doses of abatacept to evaluate in patients with pJIA. Population pharmacokinetic (PPK) and exposure-response (E-R) analyses were conducted to determine whether the weight-tiered subcutaneous regimen provides near-maximal efficacy and is therapeutically comparable to the intravenous regimen in patients with pJIA aged 2-17 years. Combined study data from intravenous or subcutaneous abatacept were used to assess clinically relevant exposure outcomes. The PPK model was developed with data from 13 phase 2/3 studies in RA and pJIA; the E-R model for the American College of Rheumatology pediatric scores (JIA-ACR 30/50/70/100 responses) in month 4 was developed with data from 2 phase 3 pJIA studies. Predefined covariates were investigated in both analyses. PPK model-predicted exposures were steady-state peak, trough (Cminss ), and time-averaged concentrations. Abatacept PK was characterized by a linear 2-compartment model (zero-order intravenous infusion, first-order subcutaneous absorption, first-order elimination); body weight was the only clinically relevant covariate. Cminss was the best exposure predictor for the JIA-ACR response: log odds for response increased in proportion to log-transformed Cminss ; JIA-ACR30 approached a plateau when Cminss ≥ 10 μg/mL. The PPK and E-R analyses demonstrated that the weight-tiered subcutaneous and intravenous abatacept dosing regimens provide near-maximal efficacy and are clinically comparable across children with pJIA who are > 2 years old.

Suppression of IgE-mediated anaphylaxis and food allergy with monovalent anti-FcεRIα mAbs

BACKGROUND

Mast cell and basophil activation by antigen cross-linking of FcεRI-bound IgE is central to allergy pathogenesis. We previously demonstrated global suppression of this process by rapid desensitization with anti-FcεRIα mAbs.

OBJECTIVES

We sought to determine whether use of monovalent (mv) anti-FcεRIα mAbs increases desensitization safety without loss of efficacy.

METHODS

mv anti-human (hu) FcεRIα mAbs were produced with mouse-derived immunoglobulin variable regions and huIgG1 or huIgG4 C regions and were used to suppress murine IgE-mediated anaphylaxis and food allergy. mAbs were administered as a single dose or as serially increasing doses to mice that express hu instead of mouse FcεRIα; mice that additionally have an allergy-promoting IL-4Rα mutation; and hu cord blood-reconstituted immunodeficient, hu cytokine-secreting, mice that have large numbers of activated hu mast cells. Anaphylaxis susceptibility was sometimes increased by treatment with IL-4 or a β-adrenergic receptor antagonist.

RESULTS

mv anti-hu FcεRIα mAbs are considerably less able than divalent mAbs are to induce anaphylaxis and deplete mast cell and basophil IgE, but mv mAbs still strongly suppress IgE-mediated disease. The mv mAbs can be safely administered as a single large dose to mice with typical susceptibility to anaphylaxis, while a rapid desensitization approach safely suppresses disease in mice with increased susceptibility. Our huIgG4 variant of mv anti-huFcεRIα mAb is safer than our huIgG1 variant is, apparently because reduced interactions with FcεRs decrease ability to indirectly cross-link FcεRI.

CONCLUSIONS

mv anti-FcεRIα mAbs more safely suppress IgE-mediated anaphylaxis and food allergy than divalent variants of the same mAbs do. These mv mAbs may be useful for suppression of huIgE-mediated disease.

FcRn is not the receptor mediating the transfer of serum IgG to colostrum in pigs

In contrast to humans or rabbits, in which maternal IgG is transmitted to offspring prenatally via the placenta or the yolk sac, large domestic animals such as pigs, cows and sheep transmit IgG exclusively through colostrum feeding after delivery. The extremely high IgG content in colostrum is absorbed by newborns via the small intestine. Although it is widely accepted that the neonatal Fc receptor, FcRn, is the receptor mediating IgG transfer across both the placenta and small intestine, it remains unclear whether FcRn also mediates serum IgG transfer across the mammary barrier to colostrum/milk, especially in large domestic animals. In this study, using a FcRn knockout pig model generated with a CRISPR-Cas9-based approach, we clearly demonstrate that FcRn is not responsible for the IgG transfer from serum to colostrum in pigs, although like in other mammals, it is involved in IgG homeostasis and mediates IgG absorption in the small intestine of newborns.

Involved free light chain: an early independent predictor of response and progression in multiple myeloma

Serum and urine protein electrophoresis (sPEP/uPEP) are the standard methods for monitoring of multiple myeloma (MM). However, a method of detection with shorter half-life, such as serum-free light chain (FLC), could detect the response or progression earlier. In total, 450 MM patients were assessed in first, second, and third line. Response and progression were classified according to International myeloma working group guidelines. The overall median time to partial response or better was detectable significantly earlier with involved free light chain (iFLC) 1.94 months (IQR: 1.61-2.23) compared to sPEP 5.39 months (IQR: 3.88-7.00). In first line, iFLC detected progression earlier compared to sPEP, particularly in patients with progression more than 18 months after best response. In conclusion, a response observed by iFLC occurs at least a median of 3 months before response is detected by sPEP/uPEP.

Lack of neonatal Fc receptor does not diminish the efficacy of the HSV-1 0ΔNLS vaccine against ocular HSV-1 challenge

The neonatal Fc receptor (FcRn) is constitutively expressed in the cornea and is up-regulated in response to herpes simplex virus type 1 (HSV-1). Previously, we found targeting cornea FcRn expression by small interfering RNA-mediated knockdown reduced the local efficacy of HSV-1 0ΔNLS vaccinated C57BL/6 mice against ocular challenge with HSV-1. The current study was undertaken to evaluate the HSV-1 0ΔNLS vaccine efficacy in FcRn deficient (FcRn KO) mice challenged with HSV-1. Whereas there was little neutralizing antibody detected in the serum of HSV-1 0ΔNLS vaccinated FcRn KO mice, these mice exhibited the same degree of protection against ocular challenge with HSV-1 as wild type (WT) C57BL/6 mice as measured by cumulative survival, infectious virus shed or retained in tissue, and corneal pathology including opacity and neovascularization. Mock-vaccinated FcRn KO mice were found to be more sensitive to ocular HSV-1 infection compared to mock-vaccinated (WT) mice in terms of cumulative survival and virus shedding. In addition, the FcRn KO mice generated significantly fewer effector (CD3⁺CD44⁺CD62L^-) and central (CD3⁺CD44⁺CD62L⁺) memory CD8⁺ T cells compared to the WT mice 7 days post infection. Collectively, mock-vaccinated FcRn KO mice are susceptible to ocular HSV-1 infection but HSV-1 0ΔNLS vaccinated FcRn KO mice are resistant suggesting that in addition to the FcRn, other pathways are involved in mediating the protective effect of the HSV-1 0ΔNLS vaccine against subsequent HSV-1 challenge.

Antigen Mass May Influence Trastuzumab Concentrations in Cerebrospinal Fluid After Intrathecal Administration

Intravenous administration of monoclonal antibodies leads to low concentrations in the central nervous system, which is a serious concern in neuro-oncology, especially in leptomeningeal carcinomatosis of HER2-overexpressing breast cancer. Case reports of i.t. administrations of trastuzumab have shown promising results in these patients but dosing regimens are empirical in absence of pharmacokinetic (PK) study. With a population PK approach, we described the fate of trastuzumab after i.t. administration in 21 women included in a phase I-II clinical trial. Trastuzumab was administered by i.t. route every week for 8 weeks and both cerebrospinal fluid (CSF) and serum were sampled to measure trough concentrations. Some patients showed noticeable CSF concentration fluctuations predicted using a target-mediated drug disposition. This target was latent and produced with a delayed feedback. Apparent volumes of distribution were close to physiological volumes (V₁  = 3.25 L, V₂  = 0.644 L, for serum and CSF, respectively). Estimated (constant) transfer from serum to CSF was very slow (k₁₂  = 0.264 mg/day) whereas estimated half-life of transfer from CSF to serum was rapid (2.2 days). From the individual parameters of patients, a single i.t. administration of 150 mg of trastuzumab corresponded to median mean residence times of 3.8 days and 15.6 days in CSF and serum, respectively. Survival without neurological relapse was not related to trastuzumab exposure. This study confirms that transfer of trastuzumab from serum to CSF is very limited and that this monoclonal antibody, when administered by i.t. route, is rapidly transferred to the serum.