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Rozanolixizumab is an anti‐human neonatal Fc receptor humanized immunoglobulin (Ig) G4 monoclonal antibody that reduces IgG, including pathogenic IgG autoantibodies. Rozanolixizumab safety and tolerability have been assessed in previous clinical studies with predominantly White participants. We assessed safety, tolerability, pharmacokinetics, and pharmacodynamics of single doses of rozanolixizumab in healthy Japanese and Chinese participants compared with White participants. This double‐blind, single‐center, UK‐based, Phase 1 study randomized 65 participants to rozanolixizumab 4 mg/kg (Japanese and White participants only), 7  mg/kg, or 10 mg/kg. All treatment‐emergent adverse events (TEAEs) were mild to moderate in severity; no severe TEAEs, serious TEAEs, or TEAEs leading to discontinuation occurred. Incidences of TEAEs in Japanese and Chinese participants were comparable to those in White participants. Japanese and Chinese participants had lower systemic rozanolixizumab exposure relative to Caucasian participants, attributable to lower actual doses administered due to lower body weight in Chinese and Japanese participants, indicating that body weight is not a relevant predictor of rozanolixizumab pharmacokinetics. All 3 ethnicities demonstrated dose‐dependent IgG reductions, with IgG nadir achieved around Day 10 and gradual return to baseline levels by Day 56. These data support the applicability of safety data from previous clinical studies of rozanolixizumab to individuals of Japanese and Chinese ethnicity. [ABSTRACT FROM AUTHOR]

Summary Primary immune thrombocytopenia (ITP) is an antiplatelet‐antibody‐mediated disorder with accelerated platelet clearance and decreased platelet production. Rozanolixizumab, a monoclonal IgG4 anti‐FcRn antibody, blocks IgG recycling and decreases IgG levels. We report efficacy and safety of rozanolixizumab in adults with persistent/chronic ITP in 24‐week phase 3 studies (TP0003; TP0006), and their 52‐week open‐label extension (OLE). Primary end‐point was durable clinically meaningful platelet response (DCMPR) of ≥50 × 109/L for 8/12 weeks during Weeks 13–25 in the double‐blind studies. Operational delays and evolving ITP treatment landscape led the sponsor to terminate these studies early; thus, only 21 and 12 (TP0003) and 20 and 10 (TP0006) patients were randomised to rozanolixizumab or placebo. Forty‐three patients enrolled in the OLE: 42 started on every 2‐week dosing; 21 later switched to weekly dosing. More rozanolixizumab‐treated than placebo‐treated patients achieved DCMPR: 4/21 versus 0 (TP0003) and 1/20 versus 0 (TP0006). Platelet increases to ≥50 × 109/L were observed on Day 8 in 52.4% (TP0003; 2/12 placebo) and 45.0% (TP0006; 1/10 placebo) of rozanolixizumab‐treated patients. OLE platelet increases were maintained while on weekly dosing. The most frequent treatment‐emergent adverse events overall were headache, pyrexia and nausea, as seen previously. Weekly dosing appears more efficacious than every 2‐week dosing. [ABSTRACT FROM AUTHOR]

Human astrovirus (HAstV) is a global cause of gastroenteritis in infants, the elderly, and the immunocompromised. However, the molecular mechanisms that control its susceptibility are not fully understood, as the functional receptor used by the virus has yet to be identified. Here, a genome‐wide CRISPR‐Cas9 library screen in Caco2 cells revealed that the neonatal Fc receptor (FcRn) can function as a receptor for classical HAstV (Mamastrovirus genotype 1). Deletion of FCGRT or B2M, which encode subunits of FcRn, rendered Caco2 cells and intestinal organoid cells resistant to HAstV infection. We also showed that human FcRn expression renders non‐susceptible cells permissive to viral infection and that FcRn binds directly to the HAstV spike protein. Therefore, our findings provide insight into the entry mechanism of HAstV into susceptible cells. We anticipate that this information can be used to develop new therapies targeting human astroviruses, providing new strategies to treat this global health issue. [ABSTRACT FROM AUTHOR]

Purpose: In the emerging field of antibody treatments for neurodegenerative diseases, reliable tools are needed to evaluate new therapeutics, diagnose and select patients, monitor disease progression, and assess therapy response. Immuno-PET combines the high affinity and exceptional specificity of monoclonal antibodies with the non-invasive imaging technique positron emission tomography (PET). Its application in neurodegenerative disease brain imaging has been limited due to the marginal uptake across the blood–brain barrier (BBB). The emergence of BBB-shuttle antibodies with enhanced uptake across the BBB extended immuno-PET to brain imaging. We recently reported about specific brain uptake of a bispecific aducanumab mTfR antibody in APP/PS1 TG mice using 89Zr-immuno-PET. However, a sufficient target-to-background ratio was reached at a relatively late scanning time point of 7 days post-injection. To investigate if a better target-to-background ratio could be achieved earlier, an aducanumab BBB-shuttle with a mutated Fc region for reduced FcRn affinity was evaluated. Procedures: AduH310A-8D3 and Adu-8D3 were modified with DFO*-NCS and subsequently radiolabeled with 89Zr. The potential influence of the H310A mutation, modification with DFO*-NCS, and subsequent radiolabeling on the in vitro binding to amyloid-beta and mTfR1 was investigated via amyloid-beta peptide ELISA and FACS analysis using mTfR1 transfected CHO-S cells. Blood kinetics, brain uptake, in vivo PET imaging and target engagement of radiolabeled AduH310A-8D3 were evaluated and compared to non-mutated Adu-8D3 in APP/PS1 TG mice and wild-type animals as controls. Results: Radiolabeling was performed with sufficient radiochemical yields and radiochemical purity. In vitro binding to amyloid-beta and mTfR1 showed no impairment. [89Zr]Zr-AduH310A-8D3 showed faster blood clearance and earlier differentiation of amyloid-beta-related brain uptake compared to [89Zr]Zr-Adu-8D3. However, only half of the brain uptake was observed for [89Zr]Zr-AduH310A-8D3. Conclusions: Although a faster blood clearance of AduH310A-8D3 was observed, it was concluded that no beneficial effects for 89Zr-immuno-PET imaging of brain uptake were obtained. [ABSTRACT FROM AUTHOR]

BACKGROUND: The alkaloid camptothecin analog SN38 is a potent antineoplastic agent, but cannot be used directly for clinical application due to its poor water solubility. Currently, the prodrug approach on SN38 has resulted in 3 FDA-approved cancer therapeutics, irinotecan, ONIVYDE, and Trodelvy. However, only 2-8% of irinotecan can be transformed enzymatically in vivo into the active metabolite SN38, which severely limits the drugs efficacy. While numerous drug delivery systems have been attempted to achieve effective SN38 delivery, none have produced drug products with antitumor efficacy better than irinotecan in clinical trials. Therefore, novel approaches are urgently needed for effectively delivering SN38 to cancer cells with better efficacy and lower toxicity. METHODS: Based on the unique properties of human serum albumin (HSA), we have developed a novel single protein encapsulation (SPE) technology to formulate cancer therapeutics for improving their pharmacokinetics (PK) and antitumor efficacy and reducing their side effects. Previous application of SPE technology to doxorubicin (DOX) formulation has led to a promising drug candidate SPEDOX-6 (FDA IND #, 152154), which will undergo a human phase I clinical trial. Using the same SPE platform on SN38, we have now produced two SPESN38 complexes, SPESN38-5 and SPESN38-8. We conducted their pharmacological evaluations with respect to maximum tolerated dose, PK, and in vivo efficacy against colorectal cancer (CRC) and soft tissue sarcoma (STS) in mouse models. RESULTS: The lyophilized SPESN38 complexes can dissolve in aqueous media to form clear and stable solutions. Maximum tolerated dose (MTD) of SPESN38-5 is 250 mg/kg by oral route (PO) and 55 mg/kg by intravenous route (IV) in CD-1 mice. SPESN38-8 has the MTD of 45 mg/kg by IV in the same mouse model. PK of SPESN38-5 by PO at 250 mg/kg gave mouse plasma AUC0-∞ of 0.05 and 4.5 nmol × h/mL for SN38 and SN38 glucuronidate (SN38G), respectively, with a surprisingly high molar ratio of SN38G:SN38 = 90:1. However, PK of SPESN38-5 by IV at 55 mg/kg yielded much higher mouse plasma AUC0-∞ of 19 and 28 nmol × h/mL for SN38 and SN38G, producing a much lower molar ratio of SN38G:SN38 = 1.5:1. Antitumor efficacy of SPESN38-5 and irinotecan (control) was evaluated against HCT-116 CRC xenograft tumors. The data indicates that SPESN38-5 by IV at 55 mg/kg is more effective in suppressing HCT-116 tumor growth with lower systemic toxicity compared to irinotecan at 50 mg/kg. Additionally, SPESN38-8 and DOX (control) by IV were evaluated in the SK-LMS-1 STS mouse model. The results show that SPESN38-8 at 33 mg/kg is highly effective for inhibiting SK-LMS-1 tumor growth with low toxicity, in contrast to DOXs insensitivity to SK-LMS-1 with high toxicity. CONCLUSION: SPESN38 complexes provide a water soluble SN38 formulation. SPESN38-5 and SPESN38-8 demonstrate better PK values, lower toxicity, and superior antitumor efficacy in mouse models, compared with irinotecan and DOX.

Abstract Background Herpes simplex virus type 1 (HSV-1) is a major cause of viral encephalitis, genital mucosal infections, and neonatal infections. Lactococcus lactis (L. lactis) has been proven to be an effective vehicle for delivering protein antigens and stimulating both mucosal and systemic immune responses. In this study, we constructed a recombinant L. lactis system expressing the protective antigen glycoprotein D (gD) of HSV-1. Results To improve the stability and persistence of antigen stimulation of the local mucosa, we inserted the immunologic adjuvant interleukin (IL)-2 and the Fc fragment of IgG into the expression system, and a recombinant L. lactis named NZ3900-gD-IL-2-Fc was constructed. By utilizing this recombinant L. lactis strain to elicit an immune response and evaluate the protective effect in mice, the recombinant L. lactis vaccine induced a significant increase in specific neutralizing antibodies, IgG, IgA, interferon-γ, and IL-4 levels in the serum of mice. Furthermore, in comparison to the mice in the control group, the vaccine also enhanced the proliferation levels of lymphocytes in response to gD. Moreover, recombinant L. lactis expressing gD significantly boosted nonspecific immune reactions in mice through the activation of immune-related genes. Furthermore, following the HSV-1 challenge of the murine lung mucosa, mice inoculated with the experimental vaccine exhibited less lung damage than control mice. Conclusion Our study presents a novel method for constructing a recombinant vaccine using the food-grade, non-pathogenic, and non-commercial bacterium L. lactis. The findings indicate that this recombinant vaccine shows promise in preventing HSV-1 infection in mice.

Effective treatment and immunoprophylaxis of viral respiratory infections with neutralizing monoclonal antibodies (mAbs) require maintaining inhibitory concentrations of mAbs at the airway surface. While engineered mAbs with increased affinity to the neonatal Fc receptor (FcRn) are increasingly employed, little is known how increased affinity of Fc to FcRn influences basal-to-apical transepithelial transport (transcytosis) of mAbs across the airway epithelium. To investigate this, we utilized a model of well-differentiated human airway epithelium (WD-HAE) that exhibited robust FcRn expression, and measured the transepithelial transport of a mAb against SARS-CoV-2 Spike protein (CR3022) with either wildtype IgG1-Fc or Fc modified with YTE or LS mutations known to increase affinity for FcRn. Despite the marked differences in the affinity of these CR3022 variants for FcRn, we did not find substantial differences in basal-toapical transport reflective of systemic dosing, or apical-to-basal transport reflective of inhaled dosing, compared to the transport of wildtype IgG1-Fc. These results suggest increasing FcRn affinity may only have limited influence over transcytosis rates of systemically dosed mAbs across the human airway epithelium over short time scales. Over longer time scales, the elevated circulating levels of mAbs with greater FcRn affinity, due to more effective FcRn-mediated recycling, may better resupply mAb into the respiratory tract, leading to more effective extended immunoprophylaxis. [ABSTRACT FROM AUTHOR]

Background: Herpes simplex virus type 1 (HSV-1) is a major cause of viral encephalitis, genital mucosal infections, and neonatal infections. Lactococcus lactis (L. lactis) has been proven to be an effective vehicle for delivering protein antigens and stimulating both mucosal and systemic immune responses. In this study, we constructed a recombinant L. lactis system expressing the protective antigen glycoprotein D (gD) of HSV-1. Results: To improve the stability and persistence of antigen stimulation of the local mucosa, we inserted the immunologic adjuvant interleukin (IL)-2 and the Fc fragment of IgG into the expression system, and a recombinant L. lactis named NZ3900-gD-IL-2-Fc was constructed. By utilizing this recombinant L. lactis strain to elicit an immune response and evaluate the protective effect in mice, the recombinant L. lactis vaccine induced a significant increase in specific neutralizing antibodies, IgG, IgA, interferon-γ, and IL-4 levels in the serum of mice. Furthermore, in comparison to the mice in the control group, the vaccine also enhanced the proliferation levels of lymphocytes in response to gD. Moreover, recombinant L. lactis expressing gD significantly boosted nonspecific immune reactions in mice through the activation of immune-related genes. Furthermore, following the HSV-1 challenge of the murine lung mucosa, mice inoculated with the experimental vaccine exhibited less lung damage than control mice. Conclusion: Our study presents a novel method for constructing a recombinant vaccine using the food-grade, non-pathogenic, and non-commercial bacterium L. lactis. The findings indicate that this recombinant vaccine shows promise in preventing HSV-1 infection in mice. [ABSTRACT FROM AUTHOR]

Introduction/Aims: Efgartigimod, a neonatal Fc‐receptor inhibitor, has recently been approved as treatment for myasthenia gravis (MG). In this retrospective cohort study, we aimed to systematically assess short‐ and long‐term effectiveness of efgartigimod in patients with refractory MG. Methods: Sixteen patients with refractory autoimmune acetylcholine receptor MG were treated with efgartigimod. Data were collected from January 2021 to March 2023 on Myasthenia Gravis Activities of Daily Living (MG‐ADL), Quantitative Myasthenia Gravis score (QMG), Myasthenia Gravis Composite score (MGC) and the 15‐item revised version of the Myasthenia Gravis Quality of Life questionnaire (MG‐QoL15r). Results: A favorable outcome was seen in 56% of patients at the last measurement. Out of 16 patients, 50% were an MG‐ADL responder after the first treatment cycle. After 4 weeks, a clinically meaningful improvement compared to baseline was seen on the MG‐ADL, QMG, and MGC. There was a statistically significant improvement on the MGQoL15r from baseline to week 4. The improvement was maintained until the last measurement for the MGC and the MGQoL15r. At the last visit, all patients had discontinued 4‐weekly dosages, shifting to administration frequencies of 1, 2, or 3 weeks. Drug doses could be decreased for prednisolone (n = 7), azathioprine (n = 2), and intravenous immunoglobulin (n = 9). Frequency of plasma exchange was decreased in nine patients. Discussion: In patients with refractory MG, efgartigimod was effective for at least half of all patients. Patients required more frequent dosing compared to the ADAPT phase 3 trial. In 80% of the patients concurrent medication could be reduced or discontinued. [ABSTRACT FROM AUTHOR]

TAVO101 is a humanized anti‐human thymic stromal lymphopoietin (TSLP) monoclonal antibody under clinical development for the treatment of atopic dermatitis (AD) and other allergic inflammatory conditions. The crystallizable fragment region of the antibody was engineered for half‐life extension and attenuated effector functions. This Phase 1, double‐blinded, randomized, placebo‐controlled study assessed the safety, tolerability, pharmacokinetics, and immunogenicity of TAVO101 in healthy adult subjects in seven ascending dose cohorts. Subjects received a single intravenous administration of TAVO101 or placebo with a 195‐day follow‐up. TAVO101 was safe and well tolerated. The incidences and severities of treatment‐emergent adverse events were mostly mild and comparable between the active and placebo groups, with no trends of dose relationship. There were no severe adverse events, deaths, or treatment‐related withdrawals. TAVO101 exhibited a linear pharmacokinetic profile, low clearance, and a median elimination half‐life of 67 days in healthy subjects. All TAVO101‐treated subjects tested negative for anti‐drug antibodies. To support development in AD, TAVO101 was studied in an oxazolone‐induced AD model in hTSLP transgenic mice and demonstrated efficacy. This long‐acting anti‐TSLP antibody has the potential for stronger and sustained allergic inflammatory disease control. The results from this study warranted further clinical development of TAVO101 in patients. [ABSTRACT FROM AUTHOR]

Esculentin-2CHa(1–30) (‟ESC") has been reported as a potent anti-diabetic peptide with little toxicity. However, its very short plasma residence time severely limits the therapeutic efficacy. To address this issue, we genetically engineered a fusion protein of tandem trimeric ESC with an albumin binding domain (ABD) and a fusion partner, SUMO (named ‟SUMO-3×ESC-ABD"). The SUMO-3×ESC-ABD, successfully produced from E. coli , showed low cellular and hemolytic toxicity while displaying potent activities for the amelioration of hyperglycemia as well as non-alcoholic fatty liver disease (NAFLD) in vitro. In animal studies, the estimated plasma half-life of SUMO-3×ESC-ABD was markedly longer (427-fold) than that of the ESC peptide. In virtue of the extended plasma residence, the SUMO-3×ESC-ABD could produce significant anti-hyperglycemic effects that lasted for >2 days, while both the ESC or ESC-ABD peptides elicited little effects. Further, twice-weekly treatment for 10 weeks, the SUMO-3×ESC-ABD displayed significant improvement in blood glucose control with a reduction in body weight. Most importantly, a significant improvement in the conditions of NAFLD was observed in the SUMO-3×ESC-ABD-treated mice. Along the systemic effects (by improved glucose tolerance and body weight reduction), direct inhibition of the hepatocyte lipid uptake was suggested as the major mechanism of the anti-NAFLD effects. Overall, this study demonstrated the utility of the long-acting SUMO-3×ESC-ABD as a potent drug candidate for the treatment of NAFLD. [Display omitted] [ABSTRACT FROM AUTHOR]

Monoclonal antibodies (mAbs) as therapeutics necessitate favorable pharmacokinetic properties, including extended serum half-life, achieved through pH-dependent binding to the neonatal Fc receptor (FcRn). While prior research has mainly investigated IgG-FcRn binding kinetics with a focus on single affinity values, it has been shown that each IgG molecule can engage two FcRn molecules throughout an endosomal pH gradient. As such, we present here a more comprehensive analysis of these interactions with an emphasis on both affinity and avidity by taking advantage of switchSENSE technology, a surface-based biosensor where recombinant FcRn was immobilized via short DNA nanolevers, mimicking the membranous orientation of the receptor. The results revealed insight into the avidity-to-affinity relationship, where assessing binding through a pH gradient ranging from pH 5.8 to 7.4 showed that the half-life extended IgG1-YTE has an affinity inflection point at pH 7.2, reflecting its engineering for improved FcRn binding compared with the wild-type counterpart. Furthermore, IgG1-YTE displayed a pH switch for the avidity enhancement factor at pH 6.2, reflecting strong receptor binding to both sides of the YTE-containing Fc, while avidity was abolished at pH 7.4. When compared with classical surface plasmon resonance (SPR) technology and complementary methods, the use of switchSENSE demonstrated superior capabilities in differentiating affinity from avidity within a single measurement. Thus, the methodology provides reliable kinetic rate parameters for both binding modes and their direct relationship as a function of pH. Also, it deciphers the potential effect of the variable Fab arms on FcRn binding, in which SPR has limitations. Our study offers guidance for how FcRn binding properties can be studied for IgG engineering strategies.

ABSTRACTBispecific antibodies (BsAbs) capable of recognizing two distinct epitopes or antigens offer promising therapeutic options for various diseases by targeting multiple pathways. The favorable pharmacokinetic (PK) properties of monoclonal antibodies (mAbs) are crucial, as they directly influence patient safety and therapeutic efficacy. For numerous mAb therapeutics, optimization of neonatal Fc receptor (FcRn) interactions and elimination of unfavorable molecular properties have led to improved PK properties. However, many BsAbs exhibit unfavorable PK, which has precluded their development as drugs. In this report, we present studies on the molecular determinants underlying the distinct PK profiles of three IgG1-scFv BsAbs. Our study indicated that high levels of nonspecific interactions, elevated isoelectric point (pI), and increased number of positively charged patches contributed to the fast clearance of IgG1-scFv. FcRn chromatography results revealed specific scFv-FcRn interactions that are unique to the IgG1-scFv, which was further supported by molecular dynamics (MD) simulation. These interactions likely stabilize the BsAb FcRn interaction at physiological pH, which in turn could disrupt FcRn-mediated BsAb recycling. In addition to the empirical observations, we also evaluated the impact of in silico properties, including pI differential between the Fab and scFv and the ratio of dipole moment to hydrophobic moment (RM) and their correlation with the observed clearance. These findings highlight that the PK properties of BsAbs may be governed by novel determinants, owing to their increased structural complexity compared to immunoglobulin G (IgG) 1 antibodies.

ABSTRACTRozanolixizumab is a humanized anti-neonatal Fc receptor (FcRn) monoclonal antibody (mAb) of the immunoglobulin G4 (IgG4) sub-class, currently in clinical development for the treatment of IgG autoantibody-driven diseases. This format is frequently used for therapeutic mAbs due to its intrinsic lower affinity for Fc gamma receptors (FcγR) and lack of C1q engagement. However, with growing evidence suggesting that no Fc-containing agent is truly “silent” in this respect, we explored the engagement of FcγRs and potential functional consequences with rozanolixizumab. In the study presented here, rozanolixizumab was shown to bind to FcγRs in both protein-protein and cell-based assays, and the kinetic data were broadly as expected based on published data for an IgG4 mAb. Rozanolixizumab was also able to mediate antibody bipolar bridging (ABB), a phenomenon that led to a reduction of labeled FcγRI from the surface of human macrophages in an FcRn-dependent manner. However, the presence of exogenous human IgG, even at low concentrations, was able to prevent both binding and ABB events. Furthermore, data from in vitro experiments using relevant human cell types that express both FcRn and FcγRI indicated no evidence for functional sequelae in relation to cellular activation events (e.g., intracellular signaling, cytokine production) upon either FcRn or FcγR binding of rozanolixizumab. These data raise important questions about whether therapeutic antagonistic mAbs like rozanolixizumab would necessarily engage FcγRs at doses typically administered to patients in the clinic, and hence challenge the relevance and interpretation of in vitro assays performed in the absence of competing IgG.

FcRn, a receptor originally known for its involvement in IgG and albumin transcytosis and recycling, is also important in the establishment of the innate and adaptive immune response. Dysregulation of the immune response has been associated with variations in FcRn expression, as observed in cancer. Recently, a link between autophagy and FcRn expression has been demonstrated. Knowing that autophagy is strongly involved in the development of reperfusion injury in kidney transplantation and that albuminemia is transiently decreased in the first 2 weeks after transplantation, we investigated variations in FcRn expression after kidney transplantation. We monitored FcRn levels by flow cytometry in leukocytes from 25 renal transplant patients and considered parameters such as albumin concentrations, estimated glomerular filtration rate, serum creatinine, serum IgG levels, and ischaemia/reperfusion time. Two groups of patients could be distinguished according to their increased or non-increased FcRn expression levels between days 2 and 6 (d2–d6) post-transplantation. Leukocyte FcRn expression at d2–d6 was correlated with albumin concentrations at d0–d2. These results suggest that albumin concentrations at d0–d2 influence FcRn expression at d2–d6, raising new questions about the mechanisms underlying these original observations. FcRn is the subject of much work in renal pathophysiology due to its involvement in the recycling/transcytosis of IgG and albumin. In our study, leukocyte FcRn expression was positively correlated to albumin concentrations in kidney-transplanted patients in early days post-transplantation. The kinetics observed suggest that albumin may impact leukocyte FcRn expression. Graphical Abstract [ABSTRACT FROM AUTHOR]

Summary: Immune checkpoint blocking therapy targeting the PD‐1/PD‐L1 inhibitory signalling pathway has produced encouraging results in the treatment of a variety of cancers. Durvalumab (Imfinzi®) targeting PD‐L1 is currently used for immunotherapy of several tumour malignancies. The Fc region of this IgG1 antibody has been engineered to reduce FcγR interactions with the aim of enhancing blockade of PD‐1/PD‐L1 interactions without the depletion of PD‐L1‐expressing immune cells. Here, we used Nicotiana benthamiana to produce four variants of Durvalumab (DL): wild‐type IgG1 and its 'Fc‐effector‐silent' variant (LALAPG) carrying further modifications to increase antibody half‐life (YTE); IgG4S228P and its variant (PVA) with Fc mutations to decrease binding to FcγRI. In addition, DL variants were produced with two distinct glycosylation profiles: afucosylated and decorated with α1,6‐core fucose. Plant‐derived DL variants were compared to the therapeutic antibody regarding their ability to (i) bind to PD‐L1, (ii) block PD‐1/PD‐L1 inhibitory signalling and (iii) engage with the neonatal Fc receptor (FcRn) and various Fcγ receptors. It was found that plant‐derived DL variants bind to recombinant PD‐L1 and to PD‐L1 expressed in gastrointestinal cancer cells and are able to effectively block its interaction with PD‐1 on T cells, thereby enhancing their activation. Furthermore, we show a positive impact of Fc amino acid mutations and core fucosylation on DL's therapeutic potential. Compared to Imfinzi®, DL‐IgG1 (LALAPG) and DL‐IgG4 (PVA)S228P show lower affinity to CD32B inhibitory receptor which can be therapeutically favourable. Importantly, DL‐IgG1 (LALAPG) also shows enhanced binding to FcRn, a key determinant of serum half‐life of IgGs. [ABSTRACT FROM AUTHOR]

Effective treatment and immunoprophylaxis of viral respiratory infections with neutralizing monoclonal antibodies (mAbs) require maintaining inhibitory concentrations of mAbs at the airway surface. While engineered mAbs with increased affinity to the neonatal Fc receptor (FcRn) are increasingly employed, little is known how increased affinity of Fc to FcRn influences basal-to-apical transepithelial transport (transcytosis) of mAbs across the airway epithelium. To investigate this, we utilized a model of well-differentiated human airway epithelium (WD-HAE) that exhibited robust FcRn expression, and measured the transepithelial transport of a mAb against SARS-CoV-2 Spike protein (CR3022) with either wildtype IgG1-Fc or Fc modified with YTE or LS mutations known to increase affinity for FcRn. Despite the marked differences in the affinity of these CR3022 variants for FcRn, we did not find substantial differences in basal-to-apical transport reflective of systemic dosing, or apical-to-basal transport reflective of inhaled dosing, compared to the transport of wildtype IgG1-Fc. These results suggest increasing FcRn affinity may only have limited influence over transcytosis rates of systemically dosed mAbs across the human airway epithelium over short time scales. Over longer time scales, the elevated circulating levels of mAbs with greater FcRn affinity, due to more effective FcRn-mediated recycling, may better resupply mAb into the respiratory tract, leading to more effective extended immunoprophylaxis.

BackgroundFor the treatment of diabetes mellitus (DM) in dogs, novel insulins with decreased injection frequency while maintaining safety and efficacy are desirable. Insulin fused with immunoglobulin-fragment-crystallizable (Fc) has an ultra-long plasma half-life because it recycles through cells, protected from proteolysis.HypothesisGlycemic control can be achieved in diabetic dogs with a recombinant fusion protein of a synthetic insulin and canine Fc (AKS-218d) administered subcutaneously once-weekly.AnimalsFive client-owned dogs with naturally occurring DM.MethodsProspective clinical trial in dogs with DM that were recruited from the UC Davis Veterinary Teaching Hospital and local veterinary clinics. Dogs previously controlled using intermediate-acting insulin q12h were transitioned to once-weekly injections of a preliminary construct identified as AKS-218d. The dose of AKS-218d was titrated weekly for 8 weeks based on clinical response and continuous interstitial glucose monitoring. Clinical signs, body weight, serum fructosamine concentrations, and mean interstitial glucose concentrations (IG) over the preceding week were compared between baseline (before AKS-218d) and during the last week of treatment. Data were compared using nonparametric paired tests.ResultsOnce-weekly AKS-218d, compared to baseline twice-daily insulin therapy, resulted in no significant changes in clinical signs, median (range) body weight (+0.4 kg [-0.5-1.1]; P = .6), fructosamine concentration (-75 mmol/L [-215 to +126]; P = .4), or mean IG (+81 mg/dL [-282 to +144]; P = .8). No adverse reactions were reported.ConclusionControl of clinical signs, body weight, and maintenance of glycemia was achieved with this once-weekly novel insulin construct in 4 of 5 dogs.

Single-domain antibody fragments (sdAbs) can be isolated from heavy-chain-only antibodies that occur in camelids or the heavy chain of conventional antibodies, that also occur in camelids. Therapeutic application of sdAbs is often complicated by their low serum half-life. Fusion to sdAb that bind to long-lived serum proteins albumin or IgG can prolong serum half-life of fusion partners. Such studies mostly focused on human application. For half-life prolongation in multiple animal species novel species cross-reacting sdAb are needed. We here describe the isolation from immunized llamas of sdAbs G6 and G13 that bound IgG of 9-10 species analysed, including horse, dog, cat, and swine, as well as sdAb A12 that bound horse, dog, swine and cat albumin. A12 bound albumin with 13 to 271 nMaffinity dependent on the species.G13 affinity was difficult to determine by biolayer interferometry due to lowand heterogeneous signals. G13 andG6 compete for the same binding domain on Fab fragments. Furthermore, they both lack the hallmark residues typical of camelid sdAbs derived from heavy-chain antibodies and had sequence characteristics typical of human sdAbs with high solubility and stability. This suggests they are derived from conventional llama antibodies. They most likely bind IgG through pairing with VL domains at the VH-VL interface rather than a paratope involving complementarity determining regions. None of the isolated sdAb interfered with FcRn binding to albumin or IgG, and thus do not prevent endosomal albumin/IgG-sdAb complex recycling. Fusions of albumin-binding sdAb A12 to several tetanus neurotoxin (TeNT) binding sdAbs prolonged the terminal serum half-life in piglets to about 4 days, comparable to authentic swine albumin. However, G13 conferred a much lower half-life of 0.84 days. Similarly, in horse, G13 prolonged half-life to only 1.2 days whereas A12 fused to two TeNT binding domains (T6T16A12) had a half-life of 21 days. The high half-life of T6T16A12, which earlier proved to be a highly potent TeNT antitoxin, further supports its therapeutic value. Furthermore, we have identified several additional sdAbs that enable tailored half-life extension of biologicals in multiple animal species. [ABSTRACT FROM AUTHOR]

Objective: ADAPT+ assessed the long-term safety, tolerability, and efficacy of efgartigimod in adult participants with generalized myasthenia gravis (gMG). Methods: ADAPT+ was an open-label, single-arm, multicenter, up to 3-year extension of the pivotal phase 3 ADAPT study. Efgartigimod was administered in treatment cycles of 4 intravenous infusions (one 10 mg/kg infusion per week). Initiation of subsequent treatment cycles was individualized based on clinical evaluation. Safety endpoints included incidence and severity of adverse events. Efficacy endpoints assessed disease severity using Myasthenia Gravis-Activities of Daily Living (MG-ADL) and Quantitative Myasthenia Gravis (QMG) scores. Results: As of January 2022, 151 participants had rolled over to ADAPT+ and 145 had received ≥1 dose of efgartigimod, of whom, 111 (76.6%) were AChR-Ab+ and 34 (23.4%) were AChR-Ab-. Mean study duration (treatment plus follow-up) was 548 days, and participants received up to 17 treatment cycles, corresponding to 217.6 participant-years of exposure. In the overall population, 123 (84.8%) participants reported ≥1 treatment-emergent adverse event; most frequent were headache (36 [24.8%]), COVID-19 (22 [15.2%]), and nasopharyngitis (20 [13.8%]). Clinically meaningful improvement (CMI) in mean MG-ADL and QMG scores was seen as early as 1 week following the first infusion across multiple cycles in AChR-Ab+ and AChR-Ab-participants. Maximal MG-ADL and QMG improvements aligned with onset and magnitude of total IgG and AChR-Ab reductions. For AChR-Ab+ participants at any time point in each of the first 10 treatment cycles, more than 90% had a maximum reduction of ≥2 points (CMI) in MG-ADL total score; across the 7 cycles in which QMG was measured, 69.4% to 91.3% of participants demonstrated a maximum reduction of ≥3 points (CMI) in QMG total score. Many participants demonstrated improvements well beyond CMI thresholds. In AChR-Ab+ participants with ≥1 year of combined follow-up between ADAPT and ADAPT+, mean number of annualized cycles was 4.7 per year (median [range] 5.0 [0.5-7.6]). Conclusion: Results of ADAPT+ corroborate the substantial clinical improvements seen with efgartigimod in ADAPT and support its long-term safety, tolerability, and efficacy, as well as an individualized dosing regimen for treatment of gMG. [ABSTRACT FROM AUTHOR]

Stiff-person syndrome (SPS) is a rare autoimmune neurological disorder characterized by high titers of antibodies against glutamic acid decarboxylase (GAD) causing impaired GABAergic inhibitory neurotransmission. To date, there is not a defined therapy for such condition, but immunomodulating therapies, such as plasma exchange, intravenous immunoglobulins, and rituximab, have been widely used in clinical practice. However, the efficacy and tolerability of these treatments is not well established. Efgartigimod, a new neonatal Fc receptor (FcRn) blocker, is a human IgG1 antibody Fc fragment engineered with increased affinity for FcRn binding, leading to a reduction in IgGs levels, including pathogenic IgG autoantibody showing promising results in neurological autoimmune disorders and has been approved for the treatment of AChR-seropositive generalized myasthenia gravis (MG). In this study, we report and describe the first data on treatment with efgartigimod in three patients affected by both AChR-seropositive generalized MG and anti-GAD-seropositive SPS. Patients were followed since the start of efgartigimod and for the whole treatment period (12 weeks). MG symptoms were assessed with the "MG activity of daily living score" and the Quantitative Myasthenia Gravis score, while SPS ones were assessed with the "SPS activity of daily living score"; muscle strength was assessed with the Medical Research Council Sum score; the overall disability from MG and SPS was assessed by the modified Rankin Scale. All patients showed an improvement in symptoms of both SPS and MG after 2 cycles of treatment. Our data suggest that efgartigimod may be considered as a candidate drug for SPS and other autoantibody-mediated neurological disorders. [ABSTRACT FROM AUTHOR]

Chlamydia trachomatis infections are an important sexually transmitted infection that can lead to inflammation, scarring and hydrosalpinx/infertility. However, infections are commonly clinically asymptomatic and do not receive treatment. The underlying cause of asymptomatic immunopathology remains unknown. Here, we demonstrate that IgG produced during male infection enhanced the incidence of immunopathology and infertility in females. Human endocervical cells expressing the neonatal Fc Receptor (FcRn) increased translocation of human IgG‐opsonized C. trachomatis. Using total IgG purified from infected male mice, we opsonized C. muridarum and then infected female mice, mimicking sexual transmission. Following infection, IgG‐opsonized Chlamydia was found to transcytose the epithelial barrier in the uterus, where it was phagocytosed by antigen‐presenting cells (APCs) and trafficked to the draining lymph nodes. APCs then expanded both CD4+ and CD8+ T cell populations and caused significantly more infertility in female mice infected with non‐opsonized Chlamydia. Enhanced phagocytosis of IgG‐opsonized Chlamydia significantly increased pro‐inflammatory signalling and T cell proliferation. As IgG is transcytosed by FcRn, we utilized FcRn−/− mice and observed that shedding kinetics of Chlamydia were only affected in FcRn−/− mice infected with IgG‐opsonized Chlamydia. Depletion of CD8+ T cells in FcRn−/− mice lead to a significant reduction in the incidence of infertility. Taken together, these data demonstrate that IgG seroconversion during male infection can amplify female immunopathology, dependent on FcRn transcytosis, APC differentiation and enhanced CD8 T cell responses. [ABSTRACT FROM AUTHOR]

Single-domain antibody fragments (sdAbs) can be isolated from heavy-chain-only antibodies that occur in camelids or the heavy chain of conventional antibodies, that also occur in camelids. Therapeutic application of sdAbs is often complicated by their low serum half-life. Fusion to sdAb that bind to long-lived serum proteins albumin or IgG can prolong serum half-life of fusion partners. Such studies mostly focused on human application. For half-life prolongation in multiple animal species novel species cross-reacting sdAb are needed. We here describe the isolation from immunized llamas of sdAbs G6 and G13 that bound IgG of 9-10 species analysed, including horse, dog, cat, and swine, as well as sdAb A12 that bound horse, dog, swine and cat albumin. A12 bound albumin with 13 to 271 nM affinity dependent on the species. G13 affinity was difficult to determine by biolayer interferometry due to low and heterogeneous signals. G13 and G6 compete for the same binding domain on Fab fragments. Furthermore, they both lack the hallmark residues typical of camelid sdAbs derived from heavy-chain antibodies and had sequence characteristics typical of human sdAbs with high solubility and stability. This suggests they are derived from conventional llama antibodies. They most likely bind IgG through pairing with VL domains at the VH-VL interface rather than a paratope involving complementarity determining regions. None of the isolated sdAb interfered with FcRn binding to albumin or IgG, and thus do not prevent endosomal albumin/IgG-sdAb complex recycling. Fusions of albumin-binding sdAb A12 to several tetanus neurotoxin (TeNT) binding sdAbs prolonged the terminal serum half-life in piglets to about 4 days, comparable to authentic swine albumin. However, G13 conferred a much lower half-life of 0.84 days. Similarly, in horse, G13 prolonged half-life to only 1.2 days whereas A12 fused to two TeNT binding domains (T6T16A12) had a half-life of 21 days. The high half-life of T6T16A12, which earlier proved to be a highly potent TeNT antitoxin, further supports its therapeutic value. Furthermore, we have identified several additional sdAbs that enable tailored half-life extension of biologicals in multiple animal species.

ObjectiveADAPT+ assessed the long-term safety, tolerability, and efficacy of efgartigimod in adult participants with generalized myasthenia gravis (gMG).MethodsADAPT+ was an open-label, single-arm, multicenter, up to 3-year extension of the pivotal phase 3 ADAPT study. Efgartigimod was administered in treatment cycles of 4 intravenous infusions (one 10 mg/kg infusion per week). Initiation of subsequent treatment cycles was individualized based on clinical evaluation. Safety endpoints included incidence and severity of adverse events. Efficacy endpoints assessed disease severity using Myasthenia Gravis-Activities of Daily Living (MG-ADL) and Quantitative Myasthenia Gravis (QMG) scores.ResultsAs of January 2022, 151 participants had rolled over to ADAPT+ and 145 had received ≥1 dose of efgartigimod, of whom, 111 (76.6%) were AChR-Ab+ and 34 (23.4%) were AChR-Ab−. Mean study duration (treatment plus follow-up) was 548 days, and participants received up to 17 treatment cycles, corresponding to 217.6 participant-years of exposure. In the overall population, 123 (84.8%) participants reported ≥1 treatment-emergent adverse event; most frequent were headache (36 [24.8%]), COVID-19 (22 [15.2%]), and nasopharyngitis (20 [13.8%]). Clinically meaningful improvement (CMI) in mean MG-ADL and QMG scores was seen as early as 1 week following the first infusion across multiple cycles in AChR-Ab+ and AChR-Ab− participants. Maximal MG-ADL and QMG improvements aligned with onset and magnitude of total IgG and AChR-Ab reductions. For AChR-Ab+ participants at any time point in each of the first 10 treatment cycles, more than 90% had a maximum reduction of ≥2 points (CMI) in MG-ADL total score; across the 7 cycles in which QMG was measured, 69.4% to 91.3% of participants demonstrated a maximum reduction of ≥3 points (CMI) in QMG total score. Many participants demonstrated improvements well beyond CMI thresholds. In AChR-Ab+ participants with ≥1 year of combined follow-up between ADAPT and ADAPT+, mean number of annualized cycles was 4.7 per year (median [range] 5.0 [0.5–7.6]).ConclusionResults of ADAPT+ corroborate the substantial clinical improvements seen with efgartigimod in ADAPT and support its long-term safety, tolerability, and efficacy, as well as an individualized dosing regimen for treatment of gMG.Clinical trial registrationhttps://classic.clinicaltrials.gov/ct2/show/NCT03770403, NCT03770403.

High baseline clearance of immune checkpoint inhibitors (ICIs), independent of dose or systemic exposure, is associated with cachexia and poor outcomes in cancer patients. Mechanisms linking ICI clearance, cachexia and ICI therapy failure are unknown. Here, we evaluate in four murine models and across multiple antibodies whether altered baseline catabolic clearance of administered antibody requires a tumor and/or cachexia and whether medical reversal of cachexia phenotype can alleviate altered clearance. Key findings include mild cachexia phenotype and lack of elevated pembrolizumab clearance in the MC38 tumor-bearing model. We also observed severe cachexia and decreased, instead of increased, baseline pembrolizumab clearance in the tumor-free cisplatin-induced cachexia model. Liver Fcgrt expression correlated with altered baseline catabolic clearance, though elevated clearance was still observed with antibodies having no (human IgA) or reduced (human H310Q IgG1) FcRn binding. We conclude cachexia phenotype coincides with altered antibody clearance, though tumor presence is neither sufficient nor necessary for altered clearance in immunocompetent mice. Magnitude and direction of clearance alteration correlated with hepatic Fcgrt, suggesting changes in FcRn expression and/or recycling function may be partially responsible, though factors beyond FcRn also contribute to altered clearance in cachexia.

Context: Inhibition of the neonatal fragment crystallizable receptor (FcRn) reduces pathogenic thyrotropin receptor antibodies (TSH-R-Ab) that drive pathology in thyroid eye disease (TED). Objective: We report the first clinical studies of an FcRn inhibitor, batoclimab, in TED. Design: Proof-of-concept (POC) and randomized, double-blind placebo-controlled trials. Setting: Multicenter. Participants: Patients with moderate-to-severe, active TED. Intervention: In the POC trial, patients received weekly subcutaneous injections of batoclimab 680 mg for 2 weeks, followed by 340 mg for 4 weeks. In the double-blind trial, patients were randomized 2:2:1:2 to weekly batoclimab (680 mg, 340 mg, 255 mg) or placebo for 12 weeks. Main Outcome: Change from baseline in serum anti-TSH-R-Ab and total IgG (POC); 12-week proptosis response (randomized trial). Results: The randomized trial was terminated because of an unanticipated increase in serum cholesterol; therefore, data from 65 of the planned 77 patients were analyzed. Both trials showed marked decreases in pathogenic anti-TSH-R-Ab and total IgG serum levels (P< .001) with batoclimab. In the randomized trial, there was no statistically significant difference with batoclimab vs placebo in proptosis response at 12 weeks, although significant differences were observed at several earlier timepoints. In addition, orbital muscle volume decreased (P < .03) at 12 weeks, whereas quality of life (appearance subscale) improved (P< .03) at 19 weeks in the 680-mg group. Batoclimab was generally well tolerated, with albumin reductions and increases in lipids that reversed upon discontinuation. Conclusions: These results provide insight into the efficacy and safety of batoclimab and support its further investigation as a potential therapy for TED. [ABSTRACT FROM AUTHOR]

Advances in adeno-associated virus (AAV)-based gene therapy are transforming our ability to treat rare genetic disorders and address other unmet medical needs. However, the natural prevalence of anti-AAV neutralizing antibodies (NAbs) in humans currently limits the population who can benefit from AAV-based gene therapies. Neonatal Fc receptor (FcRn) plays an essential role in the long half-life of IgG, a key NAb. Researchers have developed several FcRn-inhibiting monoclonal antibodies to treat autoimmune diseases, as inhibiting the interaction between FcRn and IgG Fc can reduce circulating IgG levels to 20–30% of the baseline. We evaluated the utility of one such monoclonal antibody, M281, to reduce pre-existing NAb levels and to permit gene delivery to the liver and heart via systemic AAV gene therapy in mice and nonhuman primates. M281 successfully reduced NAb titers along with total IgG levels; it also enhanced gene delivery to the liver and other organs after intravenous administration of AAV in NAb-positive animals. These results indicate that mitigating pre-existing humoral immunity via disruption of the FcRn–IgG interaction may make AAV-based gene therapies effective in NAb-positive patients. [ABSTRACT FROM AUTHOR]

BackgroundTreatment of diabetes mellitus (DM) in cats typically requires insulin injections q12h-q24h, posing a major compliance barrier for caregivers. Novel treatments enabling decreased injection frequency while maintaining safety are highly desirable. Insulin fused with feline immunoglobulin fragment crystallizable (Fc) has an ultra-long plasma half-life because it recycles through cells where it is protected from proteolysis.HypothesisGlycemic control can be achieved in diabetic cats with a recombinant fusion protein of a synthetic insulin and feline Fc (AKS-267c) administered SC weekly.AnimalsFive cats with spontaneous DM.MethodsCats previously controlled using insulin glargine q12h were transitioned to once-weekly injection of AKS-267c. The dose of AKS-267c was titrated weekly for 7 weeks based on continuous glucose monitoring. Clinical signs, body weight, fructosamine concentrations, and mean interstitial glucose concentrations (IG) were compared between baseline (week 0, on insulin glargine) and the last week of treatment. Data were assessed for normality and compared using parametric or nonparametric paired tests (as appropriate).ResultsAfter 7 weeks of once-weekly injections, compared to baseline, there were no significant changes in clinical signs, body weight (median [range] gain, 0.1 kg [-0.1 to +0.7]; P = .5), fructosamine (-60 mmol/L [-338 to +206]; P = .6), and mean IG concentrations (change = -153 mmol/L [-179 to +29]; P = .3), and no adverse reactions were reported.ConclusionSuccessful control of clinical signs and maintenance of glycemia was achieved with this once-weekly novel insulin treatment. The efficacy and safety of this novel formulation should be further assessed in a large clinical trial.

Graves orbitopathy, also known as thyroid eye disease, affects around 20% of patients with Graves disease. It is disfiguring and has a significant impact on quality of life. In the past, the standard approach was to wait for the disease to "burn-out" and then perform corrective surgeries. However, high-dose steroids have been shown to reduce symptoms and became the standard of care. In 2017, a failed cancer therapeutic called teprotumumab showed remarkable results in reducing proptosis, leading to an explosion of drug repurposing for this condition. One approach involves using monoclonal antibodies to target the neonatal fragment crystallizable receptor (FcRn). A study using batoclimab, an FcRn inhibitor, showed promising results in reducing proptosis, but the trial was stopped due to adverse effects on LDL and serum albumin levels. These findings provide important insights into the disease process and expand therapeutic options. However, the long-term safety and cost-effectiveness of FcRn inhibitors need to be further investigated. Overall, the paradigm for treating Graves orbitopathy is expected to change in the coming years, with surgery and high-dose steroids playing a smaller role. [Extracted from the article]

Seismic elastic parameter inversion translates seismic data into subsurface structures and physical properties of formations. Traditional model-based inversion methods have limitations in retrieving complex geological structures. In recent years, deep learning methods have emerged as preferable alternatives. Nevertheless, inverting multiple elastic parameters using neural networks individually is computationally intensive and can lead to overfitting due to a shortage of labeled data in field applications. Multi-task learning can be employed to invert elastic parameters simultaneously. In this work, a hybrid network that leverages the fully convolutional residual network (FCRN) and the gated recurrent unit network (GRU) is designed for the simultaneous inversion of P-wave velocity and density from post-stack seismic data. The FCRN efficiently extracts local information from seismic data, while the GRU captures global dependency over time. To further improve the horizontal continuity and inversion stability, we use a multi-trace to single-trace (M2S) inversion strategy. Consequently, we name our proposed method the M2S multi-task FCRN and GRU hybrid network (M2S-MFCRGRU). Through anti-noise experiments and blind well tests, M2S-MFCRGRU exhibits superior anti-noise performance and generalization ability. Comprehensive experimental inversion results also showcase the excellent lateral continuity, vertical resolution, and stability of the M2S-MFCRGRU inversion results. [ABSTRACT FROM AUTHOR]

Transplacental transport of maternal IgG via the neonatal Fc receptor (FcRn) provides babies with passive immunity. Several factors are reported to influence transport, including the avidity of antibodies (Abs) for their cognate antigens. Unfortunately, information on the role of antibody (Ab) avidity is limited. This study investigated if i) antibodies (Abs) with high avidity for 6 Plasmodium falciparum antigens and tetanus toxoid (TTx) were preferentially transferred to premature and term Cameroonian babies and ii) if Ab avidity was increased in babies whose mothers had placental malaria (PM), implicating the involvement of immune complexes. Total IgG (mg/ml) and Abs to malarial antigens (AMA1, EBA-175, MSP1-42, MSP2, MSP3, DBL5 of VAR2CSA) and TTx were measured in paired mother-cord samples obtained from premature and term deliveries in Cameroon. Half the women had PM at delivery. Avidity Indices (AIs) were determined by treating antigen-bound-Abs with different molar concentrations of NH 4 SCN and calculating 50% endpoints. Total IgG and antigen-specific Abs increased in cord blood with gestational age; however, AIs did not. AIs in paired maternal-cord blood samples were strongly associated for all antigens (r = 0.77–0.96). However, no significant different in AIs was found between paired mother-cord blood samples for any of the antigens (p values > 0.05). Similarly, Ab avidity was not increased in cord blood of babies whose mothers had PM or hypergammaglobulinemia. Overall, there was no evidence that higher avidity Abs to any of the malarial antigens or TTx were preferentially transferred to Cameroonian babies. • Antibody avidity to malarial antigens was similar in premature and term babies. • The avidity of antibodies to malaria antigens was the same in mother and cord blood. • Placental malaria did not alter transfer of high avidity anti-malarial antibodies. • Hypergammaglobulinemia didn't affect avidity of transferred antimalaria antibodies. [ABSTRACT FROM AUTHOR]

Muscle-specific kinase (MuSK) Myasthenia Gravis (MG) represents a prototypical antibody-mediated disease characterized by predominantly focal muscle weakness (neck, facial, and bulbar muscles) and fatigability. The pathogenic antibodies mostly belong to the immunoglobulin subclass (Ig)G4, a feature which attributes them their specific properties and pathogenic profile. On the other hand, acetylcholine receptor (AChR) MG, the most prevalent form of MG, is characterized by immunoglobulin (Ig)G1 and IgG3 antibodies to the AChR. IgG4 class autoantibodies are impotent to fix complement and only weakly bind Fcreceptors expressed on immune cells and exert their pathogenicity via interfering with the interaction between their targets and binding partners (e.g. between MuSK and LRP4). Cardinal differences between AChR and MuSK-MG are the thymus involvement (not prominent in MuSK-MG), the distinct HLA alleles, and core immunopathological patterns of pathology in neuromuscular junction, structure, and function. In MuSK-MG, classical treatment options are usually less effective (e.g. IVIG) with the need for prolonged and high doses of steroids difficult to be tapered to control symptoms. Exceptional clinical response to plasmapheresis and rituximab has been particularly observed in these patients. Reduction of antibody titers follows the clinical efficacy of anti-CD20 therapies, a feature implying the role of short-lived plasma cells (SLPB) in autoantibody production. Novel therapeutic monoclonal against B cells at different stages of their maturation (like plasmablasts), or against molecules involved in B cell activation, represent promising therapeutic targets. A revolution in autoantibody-mediated diseases is pharmacological interference with the neonatal Fc receptor, leading to a rapid reduction of circulating IgGs (including autoantibodies), an approach already suitable for AChR-MG and promising for MuSK-MG. New precision medicine approaches involve Chimeric autoantibody receptor T (CAAR-T) cells that are engineered to target antigen-specific B cells in MuSK-MG and represent a milestone in the development of targeted immunotherapies. This review aims to provide a detailed update on the pathomechanisms involved in MuSK-MG (cellular and humoral aberrations), fostering the understanding of the latest indications regarding the efficacy of different treatment strategies. [ABSTRACT FROM AUTHOR]

The concept of grafting mannose 6-phosphonate derivatives (M6Pn), named AMFA, on therapeutic proteins was first developed for the improvement of enzyme delivery in lysosomal storage disorders. This glycoengineering increases the cellular uptake of the protein via the cation-independent mannose 6-phosphate receptor (M6PR) which further allows their targeting to the lysosomes. In the present study, we investigated the extent to which the direct grafting of AMFA onto a drug, here a monoclonal antibody (mAb), affects the cell uptake and recycling of the antibody. The antibodies infliximab (IFX) and adalimumab (ADA), directed against the tumor necrosis factor α (TNFα), grafted with AMFA acquired an affinity for the M6PR, resulting in a >3-fold increase in drug release in cells. Subsequently, the impact of AMFA grafting to the Fc portion of mAb on its affinity for the neonatal Fc receptor (FcRn), which is the key receptor for antibody recycling, was evaluated. Whether one to three AMFA moieties were grafted, FcRn-mediated recycling of mAb was not affected. AMFA grafting did not impair the pharmacokinetics of both ADA and IFX and presented a high stability since AMFA were still bound to mAb in the plasma of mice 21 days after the treatment. In conclusion, this type of antibody engineering with a reduced number of AMFA confers M6PR targeting property and increases endocytosis, and yet appears fully compatible with FcRn binding and with antibody recycling and transcytosis. [Display omitted] • AMFA addition onto monoclonal antibody (mAb) enables M6PR recognition without altering antigen and FcRn affinities. • AMFA grafting allows an increase in cell delivery of mAb-AMFA. • AMFA grafting on Fc fragment does not affect mAb recycling. • The mAb-AMFA recycling is FcRn-mediated. • mAb-AMFA and mAb have comparable plasma half-lives. • AMFA is still bound to mAb 21 days in mouse. [ABSTRACT FROM AUTHOR]

Keywords: colostrum; FcRn; lactoferrin; mammary; regulation EN colostrum FcRn lactoferrin mammary regulation 37 43 7 06/20/23 20230601 NES 230601 Implications Colostrum formation is directed by placental structure and hormone signals Quality colostrum is defined by the concentration of immunoglobulin Quality colostrum formation in ungulates (hoofed mammals) is dependent on the Fc receptor of the neonate (FcRn) While the FcRn binds IgG1, IgG2, and albumin, only IgG1 is transported to colostrum FcRn IgG release into colostrum is pH dependent and lactoferrin likely facilitates it release Introduction Members of the class mammalia are so named for their mammary glands. Another example of this variation is that ungulate species form colostrum with IgG in a period of 3-4 weeks before birth ending shortly after partum, while the rodent species continue colostrum production over the entire suckling period (21 d) with an IgA emphasis that gradually transitions to mature milk. Immunoglobulins present in cow colostrum include G, M, and A, but it is IgG subclass 1 (IgG1) that constitutes 65-80% of immunoglobulin in cow colostrum (Table 1). Thus, milk secretion and hence dilution of the pre-colostrum secretion starts at this time and provides liquid colostrum at first milking ([14]). [Extracted from the article]

Monoclonal antibodies, endogenous IgG, and serum albumin bind to FcRn in the endosome for salvaging and recycling after pinocytotic uptake, which prolongs their half-life. This mechanism has been broadly recognized and is incorporated in currently available PBPK models. Newer types of large molecules have been designed and developed, which also bind to FcRn in the plasma space for various mechanistic reasons. To incorporate FcRn binding affinity in PBPK models, binding in the plasma space and subsequent internalisation into the endosome needs to be explicitly represented. This study investigates the large molecules model in PK-Sim® and its applicability to molecules with FcRn binding affinity in plasma. With this purpose, simulations of biologicals with and without plasma binding to FcRn were performed with the large molecule model in PK-Sim®. Subsequently, this model was extended to ensure a more mechanistic description of the internalisation of FcRn and the FcRn-drug complexes. Finally, the newly developed model was used in simulations to explore the sensitivity for FcRn binding in the plasma space, and it was fitted to an in vivo dataset of wild-type IgG and FcRn inhibitor plasma concentrations in Tg32 mice. The extended model demonstrated a strongly increased sensitivity of the terminal half-life towards the plasma FcRn binding affinity and could successfully fit the in vivo dataset in Tg32 mice with meaningful parameter estimates. [ABSTRACT FROM AUTHOR]

Background: Neonatal Fc receptors (FcRn) mediate the transcytosis of IgG present in colostrum across absorptive gut epithelium of newborn calves. FcRn receptor is a heterodimer composed of two polypeptides encoded by FCGRT (Fc fragment of IgG Receptor Transporter neonatal) and B2M (Beta 2 microglobulin) genes. Polymorphism in FCGRT gene may have a bearing on absorption of colostral immunoglobulins by neonatal buffalo calves, thereby affecting their immune status and susceptibility to diseases. The primary aim of our study was to mine alleles and single nucleotide polymorphs in the FCGRT gene and determine their association with the levels of IgG in serum of neonatal buffalo calves. Methods and results: On the basis of serum IgG levels estimated by indirect ELISA in 80 newborn calves, 20 calves each with highest and lowest IgG concentration were selected to study polymorphism in the FCGRT gene. The exonic regions of this gene were amplified in nine fragments which were subjected to PCR-SSCP to detect variations followed by the sequencing of variants to locate the SNPs. A total of nine SNPs (7 in introns and 2 in exons) were detected in four polymorphic fragments. Association study based on Odds ratios (ORs) with 95% Confidence Interval (CIs) established that the SNP G40T in fragment 3 has a significant (P < 0.05) bearing on IgG level in serum of neonatal buffalo calves. Conclusion: Genetic variation in FCGRT gene in buffalo calves was found to be associated with their serum IgG levels in neonatal stage which may have implications in calf survival and growth vis-à-vis inadequate transfer of passive immunity. [ABSTRACT FROM AUTHOR]

Muscle-specific kinase (MuSK) Myasthenia Gravis (MG) represents a prototypical antibody-mediated disease characterized by predominantly focal muscle weakness (neck, facial, and bulbar muscles) and fatigability. The pathogenic antibodies mostly belong to the immunoglobulin subclass (Ig)G4, a feature which attributes them their specific properties and pathogenic profile. On the other hand, acetylcholine receptor (AChR) MG, the most prevalent form of MG, is characterized by immunoglobulin (Ig)G1 and IgG3 antibodies to the AChR. IgG4 class autoantibodies are impotent to fix complement and only weakly bind Fc-receptors expressed on immune cells and exert their pathogenicity via interfering with the interaction between their targets and binding partners (e.g. between MuSK and LRP4). Cardinal differences between AChR and MuSK-MG are the thymus involvement (not prominent in MuSK-MG), the distinct HLA alleles, and core immunopathological patterns of pathology in neuromuscular junction, structure, and function. In MuSK-MG, classical treatment options are usually less effective (e.g. IVIG) with the need for prolonged and high doses of steroids difficult to be tapered to control symptoms. Exceptional clinical response to plasmapheresis and rituximab has been particularly observed in these patients. Reduction of antibody titers follows the clinical efficacy of anti-CD20 therapies, a feature implying the role of short-lived plasma cells (SLPB) in autoantibody production. Novel therapeutic monoclonal against B cells at different stages of their maturation (like plasmablasts), or against molecules involved in B cell activation, represent promising therapeutic targets. A revolution in autoantibody-mediated diseases is pharmacological interference with the neonatal Fc receptor, leading to a rapid reduction of circulating IgGs (including autoantibodies), an approach already suitable for AChR-MG and promising for MuSK-MG. New precision medicine approaches involve Chimeric autoantibody receptor T (CAAR-T) cells that are engineered to target antigen-specific B cells in MuSK-MG and represent a milestone in the development of targeted immunotherapies. This review aims to provide a detailed update on the pathomechanisms involved in MuSK-MG (cellular and humoral aberrations), fostering the understanding of the latest indications regarding the efficacy of different treatment strategies.

Abstract Background For the treatment of diabetes mellitus (DM) in dogs, novel insulins with decreased injection frequency while maintaining safety and efficacy are desirable. Insulin fused with immunoglobulin‐fragment‐crystallizable (Fc) has an ultra‐long plasma half‐life because it recycles through cells, protected from proteolysis. Hypothesis Glycemic control can be achieved in diabetic dogs with a recombinant fusion protein of a synthetic insulin and canine Fc (AKS‐218d) administered subcutaneously once‐weekly. Animals Five client‐owned dogs with naturally occurring DM. Methods Prospective clinical trial in dogs with DM that were recruited from the UC Davis Veterinary Teaching Hospital and local veterinary clinics. Dogs previously controlled using intermediate‐acting insulin q12h were transitioned to once‐weekly injections of a preliminary construct identified as AKS‐218d. The dose of AKS‐218d was titrated weekly for 8 weeks based on clinical response and continuous interstitial glucose monitoring. Clinical signs, body weight, serum fructosamine concentrations, and mean interstitial glucose concentrations (IG) over the preceding week were compared between baseline (before AKS‐218d) and during the last week of treatment. Data were compared using nonparametric paired tests. Results Once‐weekly AKS‐218d, compared to baseline twice‐daily insulin therapy, resulted in no significant changes in clinical signs, median (range) body weight (+0.4 kg [−0.5‐1.1]; P = .6), fructosamine concentration (−75 mmol/L [−215 to +126]; P = .4), or mean IG (+81 mg/dL [−282 to +144]; P = .8). No adverse reactions were reported. Conclusion Control of clinical signs, body weight, and maintenance of glycemia was achieved with this once‐weekly novel insulin construct in 4 of 5 dogs.

ABSTRACT Transplacental transfer of maternal antibodies provides the fetus and newborn with passive protection against infectious diseases. While the role of the highly conserved neonatal Fc receptor (FcRn) in transfer of IgG in mammals is undisputed, recent reports have suggested that a second receptor may contribute to transport in humans. We report poor transfer efficiency of plant-expressed recombinant HIV-specific antibodies, including engineered variants with high FcRn affinity, following subcutaneous infusion into rhesus macaques close to parturition. Unexpectedly, unlike those derived from mammalian tissue culture, plant-derived antibodies were essentially unable to cross macaque placentas. This defect was associated with poor Fcγ receptor binding and altered Fc glycans and was not recapitulated in mice. These results suggest that maternal-fetal transfer of IgG across the three-layer primate placenta may require a second receptor and suggest a means of providing maternal antibody treatments during pregnancy while avoiding fetal harm. IMPORTANCE This study compared the ability of several human HIV envelope-directed monoclonal antibodies produced in plants with the same antibodies produced in mammalian cells for their ability to cross monkey and mouse placentas. We found that the two types of antibodies have comparable transfer efficiencies in mice, but they are differentially transferred across macaque placentas, consistent with a two-receptor IgG transport model in primates. Importantly, plant-produced monoclonal antibodies have excellent binding characteristics for human FcRn receptors, permitting desirable pharmacokinetics in humans. The lack of efficient transfer across the primate placenta suggests that therapeutic plant-based antibody treatments against autoimmune diseases and cancer could be provided to the mother while avoiding transfer and preventing harm to the fetus.

Monoclonal antibodies are biopharmaceuticals with a very long half-life due to the binding of their Fc portion to the neonatal receptor (FcRn), a pharmacokinetic property that can be further improved through engineering of the Fc portion, as demonstrated by the approval of several new drugs. Many Fc variants with increased binding to FcRn have been found using different methods, such as structure-guided design, random mutagenesis, or a combination of both, and are described in the literature as well as in patents. Our hypothesis is that this material could be subjected to a machine learning approach in order to generate new variants with similar properties. We therefore compiled 1323 Fc variants affecting the affinity for FcRn, which were disclosed in twenty patents. These data were used to train several algorithms, with two different models, in order to predict the affinity for FcRn of new randomly generated Fc variants. To determine which algorithm was the most robust, we first assessed the correlation between measured and predicted affinity in a 10-fold cross-validation test. We then generated variants by in silico random mutagenesis and compared the prediction made by the different algorithms. As a final validation, we produced variants, not described in any patents, and compared the predicted affinity with the experimental binding affinities measured by surface plasmon resonance (SPR). The best mean absolute error (MAE) between predicted and experimental values was obtained with a support vector regressor (SVR) using six features and trained on 1251 examples. With this setting, the error on the log(KD) was less than 0.17. The obtained results show that such an approach could be used to find new variants with better half-life properties that are different from those already extensively used in therapeutic antibody development. [ABSTRACT FROM AUTHOR]

This post-hoc analysis evaluates the long-term efficacy of efgartigimod versus placebo in adult patients with generalized myasthenia gravis (gMG) with acetylcholine-receptor autoantibodies (AChR-Ab+), based on data from the ADAPT RCT and its open-label extension ADAPT+. Changes from baseline in Quantitative Myasthenia Gravis (QMG) and Myasthenia Gravis-Activities of Daily Living (MG-ADL) scores were assessed by treatment group over the ADAPT (up to 20 weeks) and ADAPT+ time horizon (extended to 64 weeks for efgartigimod group patients). Response to treatment was defined as 5-point reduction in QMG or 3-point reduction in MG-ADL vs. baseline values. AChR-Ab+ patients treated with efgartigimod spent a substantially greater percentage of time in response in ADAPT based on at least a 5-point change in QMG compared to the placebo group (44 % versus 13 % respectively, p = 0.0034). Analyses based on a 3-point change in MG-ADL in ADAPT showed the percentage of time in response was nearly double for efgartigimod versus placebo (59 % versus 30 % respectively, p = 0.010). These trends were also maintained using different response definitions, as well as in patients with and without prior immune therapy exposure and by time from diagnosis (<7 years versus ≥7 years). The clinical benefit of efgartigimod was sustained over repeat treatment cycles and maintained over the long term. Response to treatment was consistent regardless of response definition and was repeated in different patient subgroups. Overall, the results of this analysis indicate that efgartigimod is an effective therapeutic option, demonstrating a robust benefit among AChR-Ab+ patients with gMG. • This post-hoc analysis of the RCT (and its open-label extension) ADAPT(+) evaluates efgartigimod's long-term efficacy in gMG. • AChR+ patients had a significantly higher response to efgartigimod than placebo in ADAPT, sustained in weeks 20-64 in ADAPT+. • Treatment response was consistent across outcomes (QMG, MG-ADL) and response criteria (2-, 3-, 5-point change from baseline). • Trends were maintained in patients with/without prior immune therapy exposure, and by time from diagnosis (<7 vs. ≥7 years). • Results should be interpreted with caution; the assessment frequency and other aspects the trial design limited the analysis. [ABSTRACT FROM AUTHOR]

Oral insulin delivery could change the life of millions of diabetic patients as an effective, safe, easy-to-use, and affordable alternative to insulin injections, known by an inherently thwarted patient compliance. Here, we designed a multistage nanoparticle (NP) system capable of circumventing the biological barriers that lead to poor drug absorption and bioavailability after oral administration. The nanosystem consists of an insulin-loaded porous silicon NP encapsulated into a pH-responsive lignin matrix, and surface-functionalized with the Fc fragment of immunoglobulin G, which acts as a targeting ligand for the neonatal Fc receptor (FcRn). The developed NPs presented small size (211 ± 1 nm) and narrow size distribution. The NPs remained intact in stomach and intestinal pH conditions, releasing the drug exclusively at pH 7.4, which mimics blood circulation. This formulation showed to be highly cytocompatible, and surface plasmon resonance studies demonstrated that FcRn-targeted NPs present higher capacity to interact and being internalized by the Caco-2 cells, which express FcRn, as demonstrated by Western blot. Ultimately, in vitro permeability studies showed that Fc-functionalized NPs induced an increase in the amount of insulin that permeated across a Caco-2/HT29-MTX co-culture model, showing apparent permeability coefficients (Papp) of 2.37 × 10−6 cm/s, over the 1.66 × 10−6 cm/s observed for their non-functionalized counterparts. Overall, these results demonstrate the potential of these NPs for oral delivery of anti-diabetic drugs.

The 5th Scientific Conference of the International Pemphigus and Pemphigoid Foundation (IPPF), "Pemphigus and Pemphigoid: A New Era of Clinical and Translational Science" was held in Orlando, Florida, on May 15-16, 2018. Scientific sessions covered recent, ongoing, and future clinical trials in pemphigus and bullous pemphigoid, disease activity and quality of life instruments, and the IPPF Natural History Study. Furthermore, the meeting provided an opportunity to hear firsthand from patients, investigators, and industry about their experience enrolling for clinical trials.

As a developmental toxicant, Zika virus (ZIKV) attacks both the growing nervous system, causing congenital Zika syndrome, and the placenta, resulting in pathological changes and associated adverse fetal outcomes. There are no vaccines, antibodies, or other treatments for ZIKV, despite the potential for its re-emergence. Multiple studies have highlighted the risk of antibodies for enhancing ZIKV infection, including during pregnancy, but the mechanisms for such effects are not fully understood. We have focused on the ability of the neonatal Fc receptor (FcRn) to interact with ZIKV in the presence and absence of relevant antibodies. We found that ZIKV replication was higher in Marvin Darby Canine Kidney (MDCK) cells that overexpress FcRn compared to those that do not, and knocking down FcRn decreased ZIKV RNA production. In the placenta trophoblast BeWo cell line, ZIKV infection itself downregulated FcRn at the mRNA and protein levels. Addition of anti-ZIKV antibodies to MDCK/FcRn cells resulted in non-monotonous neutralization curves with neutralization attenuation and even enhancement of infection at higher concentrations. Non-monotonous neutralization was also seen in BeWo cells at intermediate antibody concentrations. Our studies highlight the underappreciated role FcRn plays in ZIKV infection and may have implications for anti-ZIKV prophylaxis and therapy in pregnant women. [ABSTRACT FROM AUTHOR]

The neonatal Fc receptor (FcRn) plays a central role in recycling and biodistributing immunoglobulin G. FcRn is also involved in many physiological immune functions as well as pathological immune responses in cancer or autoimmune diseases. Low levels of FcRn in tumor cells and the microenvironment is associated with poor prognosis in non-small cell lung cancers. Among cells that are present in the tumor microenvironment, macrophages express high levels of FcRn. Macrophages are involved in these pathophysiological contexts by their dual differentiation states of pro-or antiinflammatory macrophages. However, variations in FcRn protein expression have not been described in macrophage subtypes. In this work, we studied FcRn expression in an in vitro model of pro- and anti-inflammatory macrophage differentiation. We demonstrated an inverse relation between FcRn protein and mRNA expression in macrophage populations. Autophagy, which is involved in protein degradation and acquisition of phagocytic function in macrophages, participated in regulating FcRn levels. Intravenous immunoglobulin protected FcRn against autophagosome degradation in anti-inflammatory macrophages. Our data demonstrate that autophagy participates in regulating FcRn expression in pro- and anti-inflammatory macrophages. This finding raises new questions concerning the regulation of FcRn in immune functions. [ABSTRACT FROM AUTHOR]

For nearly 50 years the proximal tubule (PT) has been known to reabsorb, process, and either catabolize or transcytose albumin from the glomerular filtrate. Innovative techniques and approaches have provided insights into these processes. Several genetic diseases, nonselective PT cell defects, chronic kidney disease (CKD), and acute PT injury lead to significant albuminuria, reaching nephrotic range. Albumin is also known to stimulate PT injury cascades. Thus, the mechanisms of albumin reabsorption, catabolism, and transcytosis are being reexamined with the use of techniques that allow for novel molecular and cellular discoveries. Megalin, a scavenger receptor, cubilin, amnionless, and Dab2 form a nonselective multireceptor complex that mediates albumin binding and uptake and directs proteins for lysosomal degradation after endocytosis. Albumin transcytosis is mediated by a pH-dependent binding affinity to the neonatal Fc receptor (FcRn) in the endosomal compartments. This reclamation pathway rescues albumin from urinary losses and cellular catabolism, extending its serum half-life. Albumin that has been altered by oxidation, glycation, or carbamylation or because of other bound ligands that do not bind to FcRn traffics to the lysosome. This molecular sorting mechanism reclaims physiological albumin and eliminates potentially toxic albumin. The clinical importance of PT albumin metabolism has also increased as albumin is now being used to bind therapeutic agents to extend their half-life and minimize filtration and kidney injury. The purpose of this review is to update and integrate evolving information regarding the reabsorption and processing of albumin by proximal tubule cells including discussion of genetic disorders and therapeutic considerations. [ABSTRACT FROM AUTHOR]

Efgartigimod represents a first‐in‐class immunomodulatory agent that is comparable to TPE in reducing immunoglobulin levels. This translates to reductions in Myasthenia Gravis symptom scores with maximal effect following the fourth weekly efgartigimod dose. Efgartigimod received FDA approval in December of 2021 and may be an alternative particularly for patients on long‐term TPE regimens of weekly or less frequent. Apheresis practitioners, especially those managing long‐term apheresis in seropositive individuals, may therefore see some of their patients transitioned from plasma exchange to efgartigimod. Long‐term experience with efgartigimod remains lacking and studies are needed to establish the role of efgartigimod in the acute setting. [ABSTRACT FROM AUTHOR]