Receptor FcRn Research Articles

Efgartigimod treatment for therapy-refractory autoimmune encephalitis with coexistent NMDAR and LGI1 antibodies: a case report and literature review.

The Fc receptor (FcRn) inhibitors can ameliorate autoimmune conditions such as myasthenia gravis through a rapid and specific clearance of serum IgG levels, and they also have potential for future use in a wider variety of antibody-mediated autoimmune diseases. Some patients with therapy-refractory autoimmune encephalitis (AE) continue to be unresponsive to initial and secondary treatment regimens. A 32-year-old male presented with predominant psychiatric symptoms and seizures, along with imaging evidence indicating multifocal cerebral cortical involvement. Neural antibody testing revealed dual positivity for N-methyl-D-aspartate receptor (NMDAR) and leucine-rich glioma-inactivated 1 (LGI1) antibodies in both serum and cerebrospinal fluid (CSF). Human leukocyte antigen (HLA) genotyping revealed the presence of the DQB1*03:01 and DQB1*06:01 alleles in the patient. Treatment with efgartigimod, the FcRn inhibitor, led to significant clinical improvements accompanied by a significant decrease in both anti-NMDAR and anti-LGI1 antibody levels. Herein, we report a rare case of therapy-refractory anti-NMDAR AE coexisting with positive LGI1 antibodies. Efgartigimod demonstrates promising potential for treating antibody-mediated AE. Clinical trial number Not applicable.

Deciphering the colostral-immunity transfer: from mammary gland to neonates small intestine.

Colostrum, the initial mammary secretion produced by various mammals following birth, is a conduit for maternal immunity transfer in diverse mammalian species. Concurrently, many cellular processes are occurring in the neonatal small intestine to prepare it to receive molecular signals from a superfood essential for the neonate's health and development. During the prepartum colostrum secretion, the newborn intestine undergoes transient alterations in the intestinal barrier, primarily regulating immunoglobulin absorption. Accordingly, the immunity transfer can be delineated in two stages: the initial stage, which occurs on the maternal side (colostrogenesis serves as the primary immunoglobulin source), and the subsequent stage, which appears on the newborn side (the gut closure). The interval between the two stages is of great consequence, influencing the extent of immunity absorption and, thus, the newborn's health outcomes. The dual-phase (maternal-neonatal) process of immunity transport intersects with numerous factors, including cellular receptors such as the neonatal Fc receptor (FcRn), endocrine factors, physiological cellular phenomena (such as the blood-milk barrier), and environmental circumstances. However, no previous discussions have investigated the immunity transfer to neonatal health, nor have they discussed both sides. This gap highlights the necessity for further investigation into the time-dependent process, which can be described as a race against time to transfer adequate immunity (in quantity and quality) to neonates. Accordingly, the review encompasses a comprehensive analysis of immunological studies, from their foundational stages to the latest molecular research conducted on various mammalian species. This review aims to discern patterns and draw comparisons that advance our understanding of the complex interplay between colostral immunity transfers from diverse view points, including veterinary science and immunology.

C5 complement inhibition versus FcRn modulation in generalised myasthenia gravis

BackgroundMyasthenia gravis (MG) is an autoimmune disorder affecting neuromuscular junctions, leading to fluctuating muscle weakness. While many patients respond well to standard immunosuppression, a substantial subgroup faces ongoing disease activity....

Reducing IgG accumulation via neonatal Fc receptor (FcRn) blockade relieves neuropathic pain.

Preclinical and clinical studies have established that autoreactive immunoglobulin G (IgG) can drive neuropathic pain. We recently demonstrated that sciatic nerve chronic constriction injury (CCI) in male and female mice results in the production of pronociceptive IgG, which accumulates around the lumbar region, including within the dorsal root ganglia (DRG) and spinal cord, facilitating the development of neuropathic pain. These data raise the intriguing possibility that neuropathic pain may be alleviated by reducing the accumulation of IgG. To this end, we tested whether biologic inhibition or genetic deletion of the neonatal Fc receptor (FcRn) would attenuate mechanical hypersensitivity (allodynia) and IgG deposition induced by CCI. FcRn are prominently expressed on myeloid and endothelial cells and extend the half-life of IgG via pinocytosis and recycling into the extracellular milieu. We show here that administration of the FcRn blocker efgartigimod either 7- or 28-days post-CCI relieved allodynia among both male and female mice, compared to the Fc fragment control. Efgartigimod, administered systemically (intraperitoneal) or to the lumbar region (intrathecal), attenuated mechanical allodynia for at least one month w. CCI-induced allodynia was similarly reduced in FcRn-deficient (FcRn-) mice compared to wild-type mice. Biologic inhibition or genetic deletion of FcRn also reduced CCI-induced accumulation of IgG on macrophages and neurons in lumbar DRG, as well as microglia in the lumbar dorsal spinal cord. Expression of the Fc receptor γ subunit (FcRγ) was reduced in efgartigimod-treated or FcRn- mice post-CCI compared to controls. The FcRγ subunit is a key component of Fc gamma receptors (FcγRs), which are activated by IgG immune complexes. In macrophage cultures stimulated by IgG immune complexes, FcRn blockade also dampened FcγR-dependent production of proinflammatory cytokines. Collectively, our study demonstrates that FcRn blockade or deletion alleviates mechanical allodynia and reduces IgG accumulation after CCI, attenuating pronociceptive IgG-FcγR signaling around the lumbar region. Strategies to block FcRn and reduce IgG recycling warrant further investigation as potential treatments for IgG-mediated neuropathic pain.

Clinical efficacy of efgartigimod combined with intravenous methylprednisolone in the acute phase of neuromyelitis optica spectrum disorders

BackgroundNeuromyelitis Optica Spectrum Disorders (NMOSD) comprise a group of autoimmune-mediated, inflammatory, demyelinating central nervous system diseases caused by aquaporin-4 (AQP4) IgG autoantibodies. Efgartigimod is a human IgG Fc fragment that reduces antibody titers by targeting the neonatal Fc receptor (FcRn). This study documents the efficacy of efgartigimod combined with intravenous methylprednisolone (IVMP) in the acute phase of NMOSD.MethodsIn this retrospective study, the medical records of NMOSD patients with acute attack who received efgartigimod plus IVMP or IVMP were reviewed. Treatment efficacy was assessed by the Expanded Disability Scale Score (EDSS) before and one month after treatment. Any side effects that occurred during the treatment period were recorded.ResultsThis study was performed on 11 patients (efgartigimod plus IVMP group [n = 4] and IVMP group [n = 7]). Efgartigimod plus IVMP was effective and had a satisfactory safety profile. EDSS was reduced by 0.5 ± 0.32 compared with the IVMP group (0.27 ± 0.02). Immunoglobulin was decreased in three patients, and the immunoglobulin G (IgG) levels gradually increased approximately 8 weeks after the last administration. Hyperlipidemia and elevated white blood cell count were common side effects. No infections or deaths occurred.ConclusionsEfgartigimod plus IVMP treatment is safe and well-tolerated in patients with acute-phase NMOSD.

Evaluation of the effect of rozanolixizumab on pregnancy outcomes and pre- and postnatal development in cynomolgus monkeys.

Rozanolixizumab, a humanised immunoglobulin (Ig) G4 monoclonal antibody that selectively inhibits binding of IgG to the neonatal Fc receptor (FcRn), was evaluated in an embryo-foetal enhanced pre- and postnatal development (ePPND) study. Pregnant female cynomolgus monkeys (19 per group) received subcutaneous rozanolixizumab 50mg/kg or 150mg/kg or vehicle every 3 days from gestation day 20 until delivery. The proportion of pregnancy losses was 15.8%, 21.1% and 5.3%, in the rozanolixizumab 50mg/kg, 150mg/kg and control groups, respectively. Based on eNormograms for groups of 18 or 20 animals, these results were considered to be within the range of spontaneous prenatal losses naturally observed in cynomolgus monkeys. Foetal examinations revealed no treatment-related effects. All infants had normal postnatal development, although higher mortality was observed in female infants from the control group during the first 3 weeks. All infants were able to mount a normal immune response to keyhole limpet haemocyanin when vaccinated at the age of 4 months. Offspring from 150mg/kg-treated mothers had very low IgG levels at birth, indicating blockade of maternal IgG transfer; infants from mothers who received 50mg/kg had variable IgG levels at birth, with mothers who had developed significant anti-drug antibodies conferring maternal IgG transfer to varying degrees. Rates of infection in infants were similar across treatment groups. IgG levels in infants from rozanolixizumab-treated groups normalised within 2 months. Treatment of pregnant cynomolgus monkeys with the FcRn inhibitor rozanolixizumab had no adverse effects on pre- or postnatal development of offspring, including immune system development.

Diversity in Naturally Acquired Immunity to Group B Streptococcus: A Comparative Study of Women from Bangladesh, Malawi, and the United Kingdom.

Significant disparities in Group B Streptococcus (GBS) colonisation and neonatal disease rates have been documented across different geographical regions. For example, Bangladesh reports notably lower rates compared to the United Kingdom (UK) and Malawi. This study investigates whether this epidemiological variability correlates with the immune response to GBS in these regions. Qualitative and quantitative analyses of naturally acquired immunoglobulin G (IgG) antibodies against GBS capsular polysaccharides (CPS) and the Alp protein family were conducted in serum samples from women of childbearing age in the UK, Bangladesh, and Malawi. The efficacy of these antibodies in clearing vaginal colonisation or protecting newborns from GBS infection was assessed using humanised mouse models. Bangladeshi women displayed the highest diversity in serotype distribution, with elevated immunoglobulin G (IgG) levels in the serum against GBS capsular polysaccharides (CPS)- Ia, Ib, II, III, IV, and V, as well as Alp family proteins. In contrast, Malawian sera demonstrated the weakest antibody response. Bangladeshi sera also showed heightened IgG-mediated complement deposition, opsonophagocytic killing and neonatal Fc receptor (FcRn)-binding while tested against CPS Ib. In a humanised FcRn mouse model, Bangladeshi sera led to faster clearance of GBS virulent serotype Ib vaginal colonisation. Additionally, offspring from dams passively immunised with Bangladeshi sera demonstrated notably increased survival rates. This study demonstrates significant variability in the immune response to GBS across different geographical regions. These findings underscore the importance of understanding GBS-induced immune response in diverse populations, which may significantly impact vaccine efficacy in these regions.

Enhanced Gut-to-Liver Oral Drug Delivery via Ligand-Modified Nanoparticles by Attenuating Protein Corona Adsorption.

The development of effective oral drug delivery systems for targeted gut-to-liver transport remains a significant challenge due to the multiple biological barriers including the harsh gastrointestinal tract (GIT) environment and the complex protein corona (PC) formation. In this study, we developed ligand-modified nanoparticles (NPs) that enable gut-to-liver drug delivery by crossing the GIT and attenuating PC formation. Specifically, mesoporous silica nanoparticles (MSNs) were functionalized with peptides targeting the neonatal Fc receptor (FcRn), capitalizing on FcRn expression in the small intestine and liver for targeted drug delivery. We showed that MSNs decorated with a small cyclic FcRn binding peptide (MSNs-FcBP) obtained enhanced diffusion in intestinal mucus and superior transportation across the intestine compared to unmodified MSNs and MSNs decorated with a large IgG Fc fragment (MSNs-Fc), which correlated with diminished protein adsorption and weaker interaction with mucin. After entering the blood circulation, reduced serum PC formation by MSNs-FcBP reduces the proteolytic and phagocytic propensity of the reticuloendothelial system, ultimately ameliorating accumulation in hepatocytes. Pharmacokinetic and pharmacodynamic studies in diabetic mice revealed that MSNs-FcBP effectively transported the therapeutic agent exenatide across the intestinal epithelium, leading to a significant hypoglycemic response and improved glucose tolerance. This study underscores the critical role of ligand selection in limiting protein corona formation, thereby significantly enhancing gut-to-liver drug delivery by increasing mucus permeation and minimizing serum-protein interactions. The effective delivery of exenatide in diabetic mice illustrates the potential of this strategy to optimize oral drug bioavailability and therapeutic efficacy.

Targeting the neonatal Fc receptor (FcRn) is not beneficial in an animal model of chronic neuritis

The inhibition of the neonatal Fc receptor (FcRn) is a promising therapeutic pathway in certain autoimmune disorders to reduce the amount of circulating pathogenic IgG autoantibodies by interfering with their recycling system. FcRn antibodies are currently being tested in chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). This study aimed to investigate the therapeutic potential of an antibody targeting FcRn in the intracellular adhesion molecule 1 (ICAM1)-deficient NOD mouse—a model representative for many aspects of human CIDP. After the onset of clinical signs of neuropathy, ICAM1-deficient NOD mice were assigned to treatment twice per week with anti-FcRn antibody, isotype control antibody (negative control) or intraperitoneal (administered) immunoglobulin (positive control). Disease severity was monitored using disease-specific assessments for ataxia and paresis such as grip strength measurements. Serum immunoglobulin levels and peripheral nerve immune cell infiltration were quantified. Treatment with anti-FcRn antibody did not ameliorate disease progression, as determined by clinical scores and grip strength analysis. Disease progression was reduced in the positive control animals receiving immunoglobulin. Consistent with the clinical results, the composition of infiltrating immune cells was not altered in the peripheral nerve of anti-FcRn antibody-treated mice compared to controls. However, in anti-FcRn antibody-treated mice, significantly lower IgG levels were detectable compared to controls. These findings suggest that targeting the FcRn recycling system does not influence disease progression in the NOD-ICAM1-deficient mouse model of CIDP. Further studies will elucidate whether the reduction of IgG levels was insufficient to deplete pathogenic autoantibodies or whether the major inflammatory driver in the NOD-ICAM1-deficient mouse animal model is mediated by factors other than pathological immunoglobulins.

FcRn-dependent IgG accumulation in adipose tissue unmasks obesity pathophysiology.

Immunoglobulin G (IgG) is traditionally recognized as a plasma protein that neutralizes antigens for immune defense. However, our research demonstrates that IgG predominantly accumulates in adipose tissue during obesity development, triggering insulin resistance and macrophage infiltration. This accumulation is governed by neonatal Fc receptor (FcRn)-dependent recycling, orchestrated in adipose progenitor cells and macrophages during the early and late stages of diet-induced obesity (DIO), respectively. Targeting FcRn abolished IgG accumulation and rectified insulin resistance and metabolic degeneration in DIO. By integrating artificial intelligence (AI) modeling with invivo and invitro experimental models, we unexpectedly uncovered an interaction between IgG's Fc-CH3 domain and the insulin receptor's ectodomain. This interaction hinders insulin binding, consequently obstructing insulin signaling and adipocyte functions. These findings unveil adipose IgG accumulation as a driving force in obesity pathophysiology, providing a novel therapeutic strategy to tackle metabolic dysfunctions.

A novel monoclonal antibody against human thymic stromal lymphopoietin for the treatment of TSLP-mediated diseases.

Thymic stromal lymphopoietin (TSLP) is a master regulator of allergic inflammation against pathogens at barrier surfaces of the lung, skin, and gut. However, aberrant TSLP activity is implicated in various allergic, chronic inflammation and autoimmune diseases and cancers. Biologics drugs neutralizing excess TSLP activity represented by tezepelumab have been approved for severe asthma and are being evaluated for the treatments of other TSLP-mediated diseases. In this study, we discovered and characterized a novel humanized anti-TSLP antibody TAVO101 with high binding affinity to human TSLP, which blocks TSLP binding to its receptor complexes on cell surface. TAVO101 showed potent neutralization of TSLP activities in the TSLP-driven STAT5 reporter assay and cell proliferation assay. Results from ex vivo studies showed that TAVO101 neutralized TSLP-mediated CCL17 release from primary human CD1c+ dendritic cells and proliferation of activated CD4+ T cells. In addition, TAVO101 showed strong efficacy in both TSLP/OVA-induced asthma and imiquimod induced psoriasis models in hTSLP/hTSLPR double knock-in mice. We further conducted Fc engineering to optimize TAVO101 antibody with reduced affinity to Fcγ receptors and C1q protein but with increased affinity to FcRn receptor for half-life extension. By recognizing a different epitope, similarly potent neutralization of TSLP activities, and longer circulating half-life than tezepelumab, novel anti-TSLP antibody TAVO101 offers a potential best-in class therapeutics for various TSLP-mediated diseases.

The neonatal Fc receptor (FcRn) is required for porcine reproductive and respiratory syndrome virus uncoating.

Porcine reproductive and respiratory syndrome virus (PRRSV) continues to cause substantial economic losses to the pig industry worldwide. Previous studies from other groups showed that CD163 is required for PRRSV uncoating and genome release. However, CD163 does not interact with nucleocapsid (N) protein. In this study, the neonatal Fc receptor (FcRn) was demonstrated to be irreplaceable for PRRSV infection by knockdown, overexpression, antibodies or IgG blocking, knockout, and replenishment assays. FcRn was further revealed to be involved in PRRSV uncoating for the first time rather than viral attachment and internalization. In detail, FcRn was determined to colocalize with CD163 and PRRSV virions in early endosomes and specially interact with N protein in early endosomes. Taken together, these results provide evidence that FcRn is an essential cellular factor for PRRSV uncoating, which will be a promising target to interfere with the viral infection.IMPORTANCEPRRSV infection results in a severe swine disease affecting pig farming in the world. Although CD163 has been implicated as the uncoating receptor for PRRSV but the uncoating mechanism of PRRSV remains unclear. Here, we identified that FcRn facilitated virion uncoating via interaction with viral N protein in early endosomes. Our work actually expands the knowledge of PRRSV infection and provides an attractive therapeutic target for the prevention and control of PRRS.

Resolution of acute motor axonal neuropathy in a patient after treatment with efgartigimod: A case report.

Guillain-Barré syndrome (GBS) is an acute autoimmune neuropathy characterized by progressive muscle weakness, often caused by immunoglobulin G (IgG) autoantibodies. There are several subtypes of GBS, of which acute motor axonal neuropathy (AMAN) is one of the most severe subtypes associated with axonal damage. It is well known that the current clinical standard of treatment is intravenous immunoglobulin (IVIg) and plasma exchange (PLEX), but some patients often show limited response or experience persistent disability. Efgartigimod, an Fc fragment of human IgG antibody, provides a way to target and reduce pathogenic IgG antibodies as a natural ligand Fc receptor (FcRn). The purpose of this study was to observe the therapeutic effect of efgartigimod on axonal GBS, which is expected to be a potential therapeutic method for GBS and AMAN. We present a case of a 58-year-old man diagnosed with AMAN, presenting with ascending symmetrical limb weakness, flaccid paralysis, and multiple cranial nerve palsies. Electromyography confirmed the axonal subtype of GBS. Despite receiving IVIg and PLEX, the patient showed suboptimal recovery. Subsequently, he was treated with efgartigimod at a dose of 10 mg/kg weekly for 4 weeks, demonstrating significant improvement in both clinical symptoms and electromyographic findings, with good tolerability. This case highlights the potential efficacy and safety of a 4-dose efgart-igimod regimen in AMAN, particularly for patients with inadequate response to conventional therapies. By targeting FcRn and promoting IgG degradation, efgartigimod offers a novel mechanism to modulate the aberrant immune response underlying AMAN. Efgartigimod at a dose of 10 mg/kg weekly for 4 weeks demonstrated promising results in this case of AMAN. While further research is warranted, our findings suggest that efgartigimod may represent a valuable addition to the therapeutic armamentarium for AMAN and potentially other autoimmune neurological conditions. Well-designed clinical trials are crucial to confirm these findings and establish optimal treatment protocols for efgartigimod in AMAN.

Translational population target binding model for the anti-FcRn fragment antibody efgartigimod

Efgartigimod is a human IgG1 antibody Fc-fragment that lowers IgG levels through blockade of the neonatal Fc receptor (FcRn) and is being evaluated for the treatment of patients with severe autoimmune diseases mediated by pathogenic IgG autoantibodies. Engineered for increased FcRn affinity at both acidic and physiological pH, efgartigimod can outcompete endogenous IgG binding, preventing FcRn-mediated recycling of IgGs and resulting in increased lysosomal degradation. A population pharmacokinetic-pharmacodynamic (PKPD) model including FcRn binding was developed based on data from two healthy volunteer studies after single and repeated administration of efgartigimod. This model was able to simultaneously describe the serum efgartigimod and total IgG profiles across dose groups, using drug-induced FcRn receptor occupancy as driver of total IgG suppression. The model was expanded to describe the PKPD of efgartigimod in cynomolgus monkeys, rabbits, rats and mice. Most species differences were explainable by including the species-specific in vitro affinity for FcRn binding at pH 7.4 and by allometric scaling of the physiological parameters. In vitro-in vivo scaling proved crucial for translation success: the drug effect was over/underpredicted in rabbits/mice when ignoring the lower/higher binding affinity of efgartigimod for these species versus human, respectively. Given the successful model prediction of the PK and total IgG dynamics across species, it was concluded that the PKPD of efgartigimod can be characterized by target binding. From the model, it is suggested that the initial fast decrease of measurable unbound efgartigimod following dosing is the result of combined clearance of free drug and high affinity target binding, while the relatively slow terminal PK phase reflects release of bound drug from the receptor. High affinity target binding protects the drug from elimination and results in a sustained PD effect characterized by an increase in the IgG degradation rate constant with increasing target receptor occupancy.

FcRn inhibitors: Transformative advances and significant impacts on IgG-mediated autoimmune diseases.

Pathogenic IgG autoantibodies play a crucial role in the pathogenesis of autoimmune diseases, and removal of pathogenic IgG autoantibodies is an important therapeutic approach and tool for such diseases. The neonatal Fc receptor (FcRn) interacts with IgG and protects it from lysosomal degradation. FcRn inhibitors accelerate the clearance of IgG antibodies, including pathogenic IgG autoantibodies, by targeting and blocking the binding of FcRn to IgG. Theoretically, FcRn inhibitors can be applied for the treatment of IgG-mediated autoimmune diseases. With successful completion of multiple relevant clinical trials, key evidence-based data have been provided for FcRn inhibitors in the treatment of IgG-mediated autoimmune diseases, and several FcRn inhibitors have been approved for these indications. Additional trials are being planned or conducted. This review examines all available high-quality clinical trials of FcRn inhibitors assessing IgG-mediated autoimmune diseases.

Population Pharmacokinetic Model of Intravenous Immunoglobulin in Patients Treated for Various Immune System Disorders

Intravenous immunoglobulin (IVIG) is used to treat various immune system disorders, but the factors influencing its disposition are not well understood. This study aimed to estimate the population pharmacokinetic parameters of IVIG and to investigate the effect of genetic polymorphism of the FCGRT gene encoding the neonatal Fc receptor (FcRn) and clinical variability on the pharmacokinetic properties of IVIG in patients with immune system disorders. Patients were recruited from 4 hospitals in Malaysia. Clinical data were recorded, and blood samples were taken for pharmacokinetic and genetic studies. Population pharmacokinetic parameters were estimated by nonlinear mixed-effects modeling in Monolix. Age, weight, baseline immunoglobulin G concentration, ethnicity, sex, genotype, disease type, and comorbidity were investigated as potential covariates. Models were evaluated using the difference in objective function value, goodness-of-fit plots, visual predictive checks, and bootstrap analysis. A total of 292 blood samples were analyzed from 79 patients. The IVIG concentrations were best described by a 2-compartment model with linear elimination. Weight was found to be an important covariate for volume of distribution in the central compartment (Vc), volume of distribution in the peripheral compartment (Vp), and clearance in the central compartment, whereas disease type was found to be an important covariate for Vp. Goodness-of-fit plots indicated that the model fit the data adequately. Genetic polymorphism of the FCGRT gene encoding the neonatal Fc receptor did not affect the pharmacokinetic properties of IVIG. This study supports the use of dosage based on weight as per current practice. The study findings highlight that Vp is significantly influenced by the type of disease being treated with IVIG. This relationship suggests that different disease types, particularly inflammatory and autoimmune conditions, may alter tissue permeability and fluid distribution due to varying degrees of inflammation. Increased inflammation can lead to enhanced permeability and retention of IVIG in peripheral tissues, reflecting higher Vp values.

The neonatal Fc receptor is a cellular receptor for human astrovirus.

Human astroviruses (HAstV) are major causes of gastroenteritis, especially in children, and there are no vaccines or antivirals currently available. Little is known about host factors required for their cellular entry. Here we utilized complementary CRISPR-Cas9-based knockout and activation screens to identify neonatal Fc receptor (FcRn) and dipeptidyl-peptidase IV (DPP4) as entry factors for HAstV infection in vitro. Disruption of FcRn or DPP4 reduced HAstV infection in permissive cells and, reciprocally, overexpression of these factors in non-permissive cells was sufficient to promote infection. We observed direct binding of FcRn, but not DPP4, with HAstV virions and the purified spike protein. This suggests that FcRn is a receptor for HAstVs while DPP4 is a cofactor for entry. Inhibitors for DPP4 and FcRn currently in clinical use prevented HAstV infection in cell lines and human enteroids. Our results reveal mechanisms of HAstV entry as well as druggable targets to limit HAstV infection.

The Many Faces of Immune Thrombocytopenia: Mechanisms, Therapies, and Clinical Challenges in Oncological Patients.

In light of these data, we decided to prepare a literature review that will explain the classification and immunological determinants of the pathogenesis of ITP and present the clinical implications of this condition, especially in patients with cancer. We reviewed the literature on immunological mechanisms, therapies, and challenges in treating ITP, particularly on cancer patients. The results of the literature review show that ITP in cancer patients can be both primary and secondary, with secondary ITP being more often associated with anticancer therapies such as chemotherapy and immunotherapy. Innovative therapies such as TPO-RA, rituximab, Bruton's kinase inhibitors, and FcRn receptor inhibitors have shown promising results in treating refractory ITP, especially in patients with chronic disease. ITP is a significant clinical challenge, especially in the context of oncology patients, where both the disease and treatment can worsen thrombocytopenia and increase the risk of bleeding complications. Treatment of oncology patients with ITP requires an individualized approach, and new therapies offer effective tools for managing this condition. Future research into immunological mechanisms may bring further advances in treating ITP and improve outcomes in cancer patients.

Efgartigimod: A Review in Generalised Myasthenia Gravis.

Efgartigimod (Vyvgart®; Vyvgart® Hytrulo) is a neonatal fragment crystallizable receptor (FcRn) antagonist indicated for the treatment of generalised myasthenia gravis (gMG) in adults who are acetylcholine receptor (AChR) antibody positive (Ab+). Efgartigimod is approved for both intravenous (IV) and subcutaneous (SC) use. In a pivotal phaseIII trial, IV efgartigimod was associated with significant and clinically meaningful improvements in myasthenia gravis symptoms and reductions in disease burden. The beneficial effects of IV efgartigimod were reproducible, durable and maintained over the long term. IV efgartigimod also improved health-related quality of life (HRQOL). In another phaseIII trial, SC efgartigimod PH20 was noninferior to IV efgartigimod in reducing total immunoglobulin G levels. Clinical improvement with SC efgartigimod PH20 was consistent with that of IV efgartigimod and was reproducible over the long term. Efgartigimod was generally well tolerated; the most common adverse events were headache and infections (with IV efgartigimod) and injection-site reactions (with SC efgartigimod PH20). Although further long-term data are required, IV and SC formulations of efgartigimod provide effective, generally well-tolerated and flexible treatment options for adults with AChR Ab+ gMG.

2D-CEX-FcRn-MS to Study Structure/Function Relation of mAb Charge Variants.

The automated elucidation of the interplay between monoclonal antibody (mAb) structure and function using two-dimensional liquid chromatography-mass spectrometry (2D-LC-MS) is reported. Charge variants, induced through forced degradation, are resolved by first-dimension (1D) cation-exchange chromatography (CEX) and subsequently collected in loops installed on a multiple heart-cutting valve prior to transfer to second-dimension (2D) neonatal crystallizable fragment receptor (FcRn) affinity chromatography coupled with MS. As such, binding affinity of the latter mAb variants can elegantly be assessed and a first glimpse of identity provided. To maximize MS sensitivity, charge variants are unfolded upon eluting from the 2D affinity column by postcolumn addition of a denaturing solution. Further structural details, i.e., modification sites and chain distribution, are unraveled by a multidimensional LC-MS (mD-LC-MS) setup incorporating 1D CEX and parallel online middle-up and bottom-up LC-MS analysis in the subsequent dimensions. Identified charge variants could be ranked according to their affinity for FcRn. Binding is predominantly impacted by heavy chain (HC) M253 oxidation and to a lesser extend, M429 oxidation. Oxidation of both HCs more drastically affects FcRn interaction compared to single-chain oxidation, and the more oxidation, the less binding. Other modifications, such as HC glycosylation, HC N385/390, and N326 deamidation or HC C-terminal processing, are not shown to affect binding. The streamlined platform is challenged against the established workflow involving offline collection of charge variants and structural and functional assessment by, respectively, LC-MS and enzyme-linked immunosorbent assay (ELISA). A decent correlation is demonstrated between the binding affinity measured with ELISA and 2D FcRn affinity chromatography. In addition, throughput is improved (7-fold), material requirements are substantially reduced (2 orders of magnitude), and sample preparation artifacts and loss are minimized. With the simultaneous determination of mAb structure and function, the current study takes the concept of multiattribute analysis to the next level, thereby contributing to the future development of safer and more effective antibody therapeutics.