IgG Binding Site Research Articles

A Phase 2/3 Placebo-Controlled, Parallel Group, Randomized Withdrawal Study to Evaluate the Efficacy and Safety of Nipocalimab for Adults with Chronic Inflammatory Demyelinating Polyneuropathy: the ARISE study (P14-8.006)

<h3>Objective:</h3> Chronic inflammatory demyelinating polyneuropathy (CIDP) is a rare, chronic autoimmune disease of the peripheral nervous system characterized by progressive weakness and impaired sensation. The ARISE study (NCT05327114) is a Phase 2/3 multicenter, double-blind, placebo-controlled, randomized withdrawal study evaluating the efficacy and safety of nipocalimab in adults with CIDP. <h3>Background:</h3> Nipocalimab is a fully human aglycosylated immunoglobulin (Ig)G1 monoclonal antibody (mAb) designed to selectively bind, saturate, and block the IgG binding site on the endogenous neonatal Fc receptor. Nipocalimab is administered via intravenous infusion. <h3>Design/Methods:</h3> The study consists of the following periods: (1) Screening (≤4 weeks)/Run-in (≤12 weeks), which includes identification of patients with active CIDP; (2) Stage A (Open-label, 12 weeks), in which participants receive nipocalimab loading dose, then once every 2 weeks (q2w); (3) Stage B (Double-blind, placebo-controlled, ≤52 weeks), in which participants are randomized 1:1 to nipocalimab q2w versus placebo; (4) Open-label extension (variable duration), in which participants receive nipocalimab q2w. Key inclusion criteria include adults ≥18 years with CIDP, progressing/relapsing forms, confirmed by independent adjudication committee; CIDP disease activity score ≥3; and adjusted INCAT disability score 2–9. Patients with pure sensory CIDP or CISP, or other diagnoses that could better explain their clinical presentation are excluded. The primary endpoint is time to first occurrence of a relapse event in Stage B. Secondary efficacy endpoints include time to initial response to nipocalimab and percentage of nipocalimab responders in Stage A, and change from baseline in functional measures (e.g. grip strength, MRC sum score, etc.) in Stage B. Other secondary endpoints include safety/tolerability, pharmacokinetics, immunogenicity, and pharmacodynamics of nipocalimab. <h3>Results:</h3> The study is currently enrolling patients, targeting approximately 300 patients, with primary study completion date anticipated in 2026. <h3>Conclusions:</h3> This ongoing phase 2/3 study will assess the efficacy, safety, PK, and PD of nipocalimab in adults with CIDP. <b>Disclosure:</b> Dr. Ford has received personal compensation for serving as an employee of Janssen . Dr. Ford has stock in Janssen. Dr. Wong has received personal compensation for serving as an employee of Janssen Research &amp; Development. Dr. Wong has received personal compensation for serving as an employee of Biogen. Dr. Wong has stock in Biogen. Dr. Youssef has received personal compensation for serving as an employee of Janssen. Dr. Youssef has stock in Janssen. Mr. Murray has received personal compensation for serving as an employee of Janssen. Dr. Lim has received personal compensation for serving as an employee of Johnson &amp; Johnson. Dr. Lim has stock in Johnson &amp; Johnson. Dr. Nobile-Orazio has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for ArgenX, Belgium. Dr. Nobile-Orazio has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for LFB, France. Dr. Nobile-Orazio has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Roche, Switzerland. Dr. Nobile-Orazio has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for CSL Behring. Dr. Nobile-Orazio has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Janssen, USA. The institution of Dr. Nobile-Orazio has received research support from Takeda/Shire. Ingemar Merkies has nothing to disclose. Dr. Cornblath has received personal compensation in the range of $5,000-$9,999 for serving as a Consultant for Octapharma. Dr. Cornblath has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Annexon. Dr. Cornblath has received personal compensation in the range of $5,000-$9,999 for serving as a Consultant for Pfizer. Dr. Cornblath has received personal compensation in the range of $5,000-$9,999 for serving as a Consultant for Grifols. Dr. Cornblath has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Cigna. Dr. Cornblath has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Alnylam. Dr. Cornblath has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Anavex. Dr. Cornblath has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Hansa. Dr. Cornblath has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for MPTP. Dr. Cornblath has received intellectual property interests from a discovery or technology relating to health care. Dr. Sun has received personal compensation for serving as an employee of Janssen.

Pharmacokinetics and Pharmacodynamics of Nipocalimab Administered at Different Rates of Intravenous Infusion in Healthy Participants: Results of a Phase 1 Placebo-Controlled Single-Dose Study

Background: Warm autoimmune hemolytic anemia (wAIHA) is a rare autoimmune condition driven by autoantibodies that can significantly impact a patient's quality of life. wAIHA is characterized by the premature destruction of red blood cells (RBCs) in the presence of autoantibodies which preferentially bind to RBCs at 37°C. There is currently no approved treatment for wAIHA. Patients with severely symptomatic anemia are typically managed with corticosteroids and rituximab, both of which are associated with potential relapse and adverse events. Nipocalimab, which is in clinical development for the treatment of wAIHA (NCT04119050), is a fully human, aglycosylated, effectorless IgG1 monoclonal antibody that targets the IgG binding site on the neonatal Fc receptor (FcRn) with high affinity to lower circulating IgG levels. This study assessed the pharmacokinetics (PK) and pharmacodynamics (PD) of single doses of nipocalimab administered at different IV infusion rates in healthy adults to support the potential use of shortened infusions in future studies. Nipocalimab was generally safe and well-tolerated at all doses and infusion rates; detailed safety results have been presented separately [Leu JH, et al. EHA 2022. Presentation P1534]. Methods: The trial was a single dose, sequential, randomized, double-blind, placebo-controlled, escalating dose and infusion rate study. Eligible participants were males or females aged 18-55 years with no clinically significant medical or physical conditions. Participants were randomized to 1 of 5 cohorts (n=8 per cohort [6 nipocalimab, 2 placebo]) to receive nipocalimab 30 mg/kg IV infused over 60, 30, 15 or 7.5 min (0.5, 1, 2, or 4 mg/kg/min), nipocalimab 60 mg/kg IV infused over 15 min (4 mg/kg/min) or matching placebo. Escalation to the next dose level was permitted following review by a safety monitoring committee. Pharmacokinetic sampling of nipocalimab was conducted predose, midpoint of infusion (MOI), end of infusion (EOI), EOI + 0.083h, EOI + 0.25h, EOI + 1h, start of infusion + 24h, Day 8, and Day 15 postdose; MOI and EOI varied for each dose. In terms of PD, total serum IgG was assessed. Results: A total of 40 participants (70% female, 93% white) received study drug, of which 30 were included in the PK analysis; 39 completed the study. Mean serum nipocalimab concentration-time profiles were similar following all 30 mg/kg doses regardless of infusion rate; mean serum concentrations were ~2 times higher following a 60 mg/kg infusion. Nipocalimab remained detectable up to ~169 hours postdose for 30 mg/kg groups and ~337 hours postdose for the 60 mg/kg group. Geometric mean peak (Cmax) and overall exposure (AUC) to nipocalimab were unaffected by infusion rate when administered at 30 mg/kg. Following a 60 mg/kg infusion, AUCs were 2.4-2.8 times higher and Cmax was 2.0-2.2 times higher than with 30 mg/kg infusions. Median Tmax was approximately at EOI following the 60 mg/kg infusion. Mean half-life (t½) values were similar in all treatment groups. In terms of total serum IgG, changes from baseline were decreased among all nipocalimab cohorts at all postdose time points. The maximum decrease in mean serum IgG levels was 79% at day 15 with nipocalimab 60 mg/kg. Conclusion: Nipocalimab Cmax and AUC were not affected by infusion rates when given at a dose of 30 mg/kg, but Tmax was delayed at the fastest infusion rates. Following the 60 mg/kg infusion, peak and overall nipocalimab exposures were 2-2.8 times higher than following 30 mg/kg infusions.

A PHASE 1 PLACEBO-CONTROLLED SINGLE-DOSE STUDY OF NIPOCALIMAB ADMINISTERED AT DIFFERENT RATES OF INTRAVENOUS INFUSION IN HEALTHY ADULTS

Warm autoimmune hemolytic anemia (wAIHA) is a rare, life-threatening disorder characterized by the destruction of red blood cells by pathogenic IgG autoantibodies. There is currently no approved treatment for wAIHA. Nipocalimab is a fully human, aglycosylated, effectorless IgG1 monoclonal antibody that blocks the IgG binding site on the neonatal Fc receptor (FcRn) with high affinity, which is in clinical development for the treatment of wAIHA. In a prior phase 1 study in healthy adults receiving single and multiple ascending doses infused intravenously (IV) over 2 hours, nipocalimab was well-tolerated with an adverse event profile comparable to placebo. However, shorter durations of nipocalimab infusion may be more convenient for patients. Here we assess the safety and tolerability of single doses of nipocalimab administered at different IV infusion rates in healthy adults to support the potential use of shortened infusions in future studies. The trial was a single dose, sequential, randomized, double-blind, placebo-controlled, escalating dose and infusion rate study. Eligible participants were males or females aged 18-55 years with no clinically significant medical or physical conditions. Participants were randomized to 1 of 5 cohorts (n = 8 per cohort [6 nipocalimab, 2 placebo]) to receive nipocalimab 30 mg/kg IV infused over 60, 30, 15 or 7.5 min (0.5, 1, 2, or 4 mg/kg/min), nipocalimab 60 mg/kg IV infused over 15 min (4 mg/kg/min) or matching placebo. Escalation to the next dose level was permitted following review by a safety monitoring committee. Safety was assessed by the frequency and nature of treatment-emergent adverse events (TEAEs). A total of 40 participants (70% female, 93% white) received study drug and were included in the safety analysis; 39 completed the study. A total of 12 participants (40%) experienced TEAEs across all nipocalimab dosing cohorts and 1 (10%) participant experienced TEAEs following administration of placebo. The most frequently reported TEAE was headache, reported by 6 participants with nipocalimab and 1 participant with placebo. Nausea was reported by 3 participants receiving nipocalimab. Grade 2 injection site reactions were reported by 2 participants but were considered unrelated to the investigational agent. None of the TEAEs were severe, and no participants discontinued treatment due to TEAEs; there were no serious adverse events or deaths. Only 4 participants experienced AEs that occurred within 24 hours after the infusion that were considered related to the study drug. Lower rates of nipocalimab infusion were associated with fewer TEAEs, while participants receiving 4 mg/kg/min (as either 30 mg/kg infused over 7.5 min or 60 mg/kg infused over 15 min) reported more TEAEs. Single doses of nipocalimab, when administered at doses up to 60 mg/kg and infusion rates up to 4 mg/kg/min were safe and well-tolerated in healthy adults. The frequency of reported TEAEs was lower in participants receiving IV nipocalimab at rates of 1 or 2 mg/kg/min, providing a target infusion rate for current and future studies. JHL, AV, LEL are employees of Janssen Research & Development, LLC, and AMBP is an employee of Janssen Latin America, which are a wholly owned subsidiaries of Johnson & Johnson, and may own stock or stock options in Johnson & Johnson.

EFFICACY AND SAFETY OF NIPOCALIMAB, AN FCRN BLOCKER, IN WARM AUTOIMMUNE HEMOLYTIC ANEMIA (WAIHA): ENERGY PHASE 2/3 STUDY DESIGN

Warm autoimmune hemolytic anemia (wAIHA) is characterized by the destruction of red blood cells (RBCs) by pathogenic autoantibodies which bind to RBCs and lead to their clearance in the spleen and liver. Patients with wAIHA can experience acute worsening of anemia, which can be a medical emergency, and have an increased risk of thromboembolic events and premature death. Nipocalimab is a fully human, aglycosylated, effectorless IgG1 monoclonal antibody that blocks the IgG binding site on the neonatal Fc receptor (FcRn) with high affinity. FcRn, which is expressed in endothelial cells, is responsible for recycling IgG into the circulation and for the relatively long half-life of IgG antibodies compared to other Igs. It is expected that nipocalimab, by blocking IgG binding to FcRn, will prevent IgG recycling and lower pathogenic IgG autoantibodies that cause many autoantibody diseases, including wAIHA. Nipocalimab has been studied in multiple phase 1 studies in healthy subjects and in a completed phase 2 study in subjects with Generalized Myasthenia Gravis (gMG). Treatment with nipocalimab was associated with rapid and durable total serum IgG and pathogenic IgG autoantibody reduction and meaningful clinical response. Here we share the rationale and study design for an adaptive, phase 2/3 multicenter, randomized, double-blind, placebo-controlled study in patients with wAIHA whose aim is to evaluate the efficacy, safety, tolerability, PK, and PD of nipocalimab compared with placebo (NCT04119050). Male or female subjects ≥18 years of age who have been diagnosed with primary or secondary wAIHA and have not experienced a sufficient response or have not tolerated currently available treatments will be included in the study. Subjects with cold antibody AIHA, cold agglutinin syndrome, mixed type (i.e., warm and cold) AIHA, or paroxysmal cold hemoglobinuria will be excluded. Participants will be randomized 1:1:1 to receive nipocalimab at two different dose schedules or placebo. Following completion of 24 weeks of double-blind treatment, participants may enter an open-label extension period to receive nipocalimab. The primary endpoint is percentage of participants achieving durable response of improvement in hemoglobin (Hgb). The main secondary endpoints are change from baseline in the total score from the FACIT-Fatigue Scale, number of participants who attain normal lactate dehydrogenase, normal haptoglobin, and normal indirect bilirubin levels at a minimum of 3 consecutive visits after baseline. ENERGY is a phase 2/3 study that will evaluate the efficacy and safety of nipocalimab in wAIHA. ENERGY is currently enrolling globally. IM received research support from Alexion, Annexon, Incyte, Kezar, Momenta, Rigel, and Sanofi; and served as a consultant for Apellis, Janssen, Momenta, Novartis, Rigel, and Sanofi. BF is a consultant of Alexion, Amgen, Janssen, Momenta, and Novartis. DC is an employee of Janssen Global Services, LLC, which is a wholly owned subsidiary of Johnson & Johnson, and may own stock or stock options in Johnson & Johnson; was an employee of Momenta. AMBP is an employee of Janssen Latin America, which is a wholly owned subsidiary of Johnson & Johnson, and may own stock or stock options in Johnson & Johnson. MHJ was an employee of Momenta.

SELECTIVE TARGETING OF FCRN AND IGG CLEARANCE BY NIPOCALIMAB PRESERVES KEY IMMUNE FUNCTIONS

Autoantibody disorders are caused by immune-system-produced antibodies that can damage the body's tissues or organs. In the case of warm autoimmune hemolytic anemia (wAIHA), pathogenic autoantibodies lead to the destruction of red blood cells. There is an unmet need for innovative targeted therapies that address the underlying pathogenesis of wAIHA in a safe and efficacious way. Nipocalimab is a fully human, aglycosylated, effectorless IgG1 monoclonal antibody that blocks the IgG binding site on the neonatal Fc receptor (FcRn) which prevents IgG recycling, leading to reduced serum levels of total IgGs, including pathogenic IgG autoantibodies. Nipocalimab is in clinical development for the treatment of multiple IgG-mediated autoantibody diseases, including wAIHA (NCT04119050). Rapid, sustained lowering of IgG was observed in the phase 2 VIVACITY study in generalized myasthenia gravis (gMG) and in phase 1 healthy volunteers. In gMG patients, nipocalimab induced rapid and sustained lowering of anti-AChR autoantibodies and MG-ADL scores, but no serious adverse events including clinically significant infections. Here, we characterize the effect of nipocalimab on immune function. Nipocalimab was evaluated extensively in vitro and in nonhuman primate-based chronic toxicology studies to evaluate selectivity, tolerability, safety and immunopharmacology. Safety, tolerability and immune-focused assessments in clinical phase 1 and Phase 2 MG studies were also completed (NCT02828046, NCT03772587). Nipocalimab binds specifically in vitro to FcRn without activation of effector function or inhibition of antigen presentation. In nonhuman primates administered up to 300 mg/kg nipocalimab QW for up to 6 months, sustained lowering of IgG was observed without adverse effects. Immunotoxicology identified no effect on immune cell phenotypes; CD8 T cell, NK or innate cell functions; T-dependent neoantigen IgM responses. Neoantigen IgG production was observed, but with lowered peak IgG titers consistent with the anticipated increase in IgG clearance with nipocalimab. In clinical studies, nipocalimab demonstrated a reproducible selective decrease in total serum IgG, including all subclasses of IgG, with no effect on IgM, IgA, IgE, CH50, C3, C4, inflammatory cytokines or acute phase proteins including, C-reactive protein (CRP). These data suggest that nipocalimab can selectively lower IgG and IgG autoantibodies while preserving cellular immunity, complete IgM response and IgG production after neoantigen challenge. Overall, nipocalimab's selective effect on IgG recycling provides a mechanistic rationale for potentially decreased infection risk despite substantial IgG lowering. LEL *, FY *, CJB *, JB *, RX *, AMBP are employed by the Janssen Pharmaceutical Companies of Johnson & Johnson and may hold stock or stock options in Johnson & Johnson; ST * is an employee of Orna Therapeutics; SK * is an employee of Checkmate Pharmaceuticals; JD * is an employee of Faze Medicines; WA * is an employee of Kisbee Therapeutics. *Former employees of Momenta Pharmaceuticals which was acquired by Janssen Pharmaceutical Companies of Johnson & Johnson.

P1535: SAFETY AND TOLERABILITY OF SINGLE ESCALATING DOSES OF INTRAVENOUS NIPOCALIMAB IN HEALTHY JAPANESE ADULTS: A RANDOMIZED, PHASE 1 PLACEBO-CONTROLLED STUDY

Background: Autoimmune hemolytic anemia (AIHA) is a rare, life-threatening disorder characterized by the destruction of red blood cells (RBCs) by autoantibodies. In Japan, the estimated prevalence of AIHA is 3-10 cases per 1 million person-years. Of these, approximately 90% of patients present with warm AIHA (wAIHA), which occurs when pathogenic IgG antibodies bind to RBCs at a temperature of ~37 °C. There is currently no approved treatment for wAIHA, and patients with severe symptomatic anemia are generally managed with corticosteroids, immunosuppressants, rescue therapies, and immune cell depleting biologic therapies. Nipocalimab is a fully human, effectorless IgG1 monoclonal antibody in clinical development for wAIHA. Nipocalimab targets the IgG binding site on the neonatal Fc receptor (FcRn) to reduce circulating IgG including anti-RBC autoantibodies. In a prior phase 1 study in healthy adults receiving single and multiple ascending doses administered by intravenous (IV) infusion, nipocalimab was well-tolerated with an adverse event profile comparable to placebo. However, the proportion of Asian participants in that study was small, and therefore the safety of nipocalimab required further investigation in this population. Aims: To assess the safety and tolerability of single escalating doses of nipocalimab administered as IV infusions in healthy Japanese adults. Methods: The trial was a randomized, double-blind, placebo-controlled, escalating single dose study. Eligible participants were healthy Japanese males or females aged 18-64 years with no clinically significant medical or physical conditions. Dosing cohorts were: nipocalimab 10 mg/kg, 30 mg/kg, and 60 mg/kg or matching placebo, infused IV over 30 min. Escalation to the next dose level only proceeded following review of safety and tolerability by the principal investigator. Safety was assessed by the frequency of treatment-emergent adverse events (TEAEs), as well as abnormalities in clinical laboratory assessments, physical examinations, or vital signs. Results: A total of 24 Japanese participants (92% female) were randomized, received study drug, and completed the study. A total of 3 participants (12.5%) experienced 1 or more TEAE: 2 in the 30 mg/kg nipocalimab cohort and 1 in the 60 mg/kg nipocalimab cohort (Table). Mild (grade 1) dizziness was the most common TEAE, which was reported by 2 participants, 1 each in the 30 mg/kg and 60 mg/kg nipocalimab cohorts. Mild influenza-like illness was reported by 1 participant who received 30 mg/kg nipocalimab and mild diarrhea was reported by 1 participant who received 60 mg/kg nipocalimab; these TEAEs were considered by the investigator as unrelated to study drug. One participant in the 30 mg/kg nipocalimab cohort discontinued study drug infusion after 22 minutes due to a moderate infusion-related reaction, which was considered to be related to study treatment. This AE was managed with an antihistamine, and the participant received only 22 mg of nipocalimab. There were no clinically significant changes in laboratory parameters or vital signs, no injection site reactions, serious adverse events, or deaths. Image:Summary/Conclusion: Single doses of nipocalimab, administered at doses between 10 mg/kg and 60 mg/kg by IV infusion, were generally safe and well-tolerated in healthy Japanese adults, consistent with the prior phase 1 study in a general population, which included Asian and non-Asian participants.

AB1289 STUDY DESIGN OF A PHASE 2/3 RANDOMIZED, DOUBLE-BLIND, PLACEBO-CONTROLLED STUDY TO ASSESS THE EFFICACY AND SAFETY OF NIPOCALIMAB, AN FcRn ANTAGONIST, IN WARM AUTOIMMUNE HEMOLYTIC ANEMIA (wAIHA)

BackgroundWarm autoimmune hemolytic anemia (wAIHA) is characterized by the destruction of red blood cells (RBCs) by pathogenic autoantibodies which bind to RBCs and lead to their clearance in the spleen and liver. Patients with wAIHA can experience acute worsening of anemia, which can be a medical emergency, and have an increased risk of thromboembolic events and premature death. Nipocalimab is a fully human, aglycosylated, effectorless IgG1 monoclonal antibody that targets the IgG binding site on the neonatal Fc receptor (FcRn) with high affinity. FcRn, which is expressed in endothelial cells, is responsible for recycling IgG into the circulation and for the relatively long half-life of IgG antibodies compared to other Igs. It is expected that nipocalimab, by inhibiting IgG binding to FcRn, will prevent IgG recycling and lower pathogenic IgG autoantibodies that cause many autoimmune diseases including warm autoimmune hemolytic anemia (wAIHA).Nipocalimab has been studied in multiple phase 1 studies in healthy subjects and in a recently completed phase 2 study in subjects with Generalized Myasthenia Gravis (gMG). In the gMG phase 2 study, nipocalimab was well tolerated at doses from 5 mg/kg every 4 weeks to 60 mg/kg every 2 weeks. Treatment with nipocalimab was associated with rapid and durable total serum IgG and pathogenic IgG autoantibody reduction and meaningful clinical response. A statistically significant relationship between IgG autoantibody reduction and clinical benefit was observed. This study provided proof-of-concept evidence that lowering pathogenic IgG autoantibodies can ameliorate the autoimmune condition these antibodies cause.ObjectivesTo share the rationale and study design for an adaptive, phase 2/3 multicenter, randomized, double-blind, placebo-controlled study in patients with wAIHA whose aim is to evaluate the efficacy, safety, tolerability, PK, and PD of nipocalimab compared with placebo1.MethodsMale or female patients ≥18 years of age who have been diagnosed with primary or secondary wAIHA and have not experienced a sufficient response or have not tolerated currently available treatments will be included in the study. Patients with cold antibody AIHA, cold agglutinin syndrome, mixed type (i.e., warm and cold) AIHA, or paroxysmal cold hemoglobinuria will be excluded. Patients will be randomized 1:1:1 to receive nipocalimab at two different dose schedules or placebo. Following completion of 24 weeks of double-blind treatment, patients may enter an open-label extension period to receive nipocalimab.ResultsThe following endpoints will be analyzed:Primary endpoint:Percentage of participants achieving durable response of improvement in hemoglobin (Hgb).Main secondary endpoints:Change from baseline in the total score from the Functional Assessment of Chronic Illness Therapy-Fatigue Scale at the end of the double-blind period.Number of participants who attain normal lactate dehydrogenase, normal haptoglobin, and normal indirect bilirubin levels at a minimum of 3 consecutive visits after baseline.ConclusionA phase 2 study investigating nipocalimab in patients with gMG provided proof of concept for a phase 2/3 interventional study with nipocalimab in patients with wAIHA. This phase 2/3 study is currently enrolling in the USA and Europe.

Signal Enhancement in Oriented Immunosorbent Assays: A Balance between Accessibility of Antigen Binding Sites and Avidity.

The sensitivity of immunoassays was reported to be increased by the orientation of antibodies. We investigated how the size and valence of antigens and orientation and valence of antibodies contribute to the analytical sensitivity of ELISA. Antigens differing in size and number of epitopes were compared using oriented and non-oriented ELISAs: the orientation of antibodies was obtained coating half-fragment antibodies on maleimide microplates, while, in non-oriented ELISA, whole antibodies were randomly physisorbed. The oriented assay performed better than the non-oriented one at each concentration (0.4–3.3 ng/mL) of a small monomeric antigen (cardiac Troponin I, 24 kDa, Rh 3 nm). No significant differences were observed with a large monovalent antigen (prostate-specific antigen-alpha(1) antichymotrypsin, 90 kDa, Rh > 3 nm), since its steric hindrance overcame the increased availability of antigen binding sites given by orientation. Large multivalent antigens (ferritin, 280 kDa, Rh 6 nm; α-fetoprotein, >70 kDa, Rh > 3.3 nm) performed better in non-oriented assays. In this case, the repeated epitopes on the surface of the antigens favored the engagement of both antigen binding sites of the whole IgG, thus suggesting that avidity represented the leading force in this experimental setting. In conclusion, the design of high-sensitivity ELISAs should consider the dimension and valency of antigens in addition to the affinity and avidity of antibodies.

Functional and Structural Characterization of a Potent C1q Inhibitor Targeting the Classical Pathway of the Complement System.

The classical pathway of complement is important for protection against pathogens and in maintaining tissue homeostasis, but excessive or aberrant activation is directly linked to numerous pathologies. We describe the development and in vitro characterization of C1qNb75, a single domain antibody (nanobody) specific for C1q, the pattern recognition molecule of the classical pathway. C1qNb75 binds to the globular head modules of human C1q with sub-nanomolar affinity and impedes classical pathway mediated hemolysis by IgG and IgM. Crystal structure analysis revealed that C1qNb75 recognizes an epitope primarily located in the C1q B-chain that overlaps with the binding sites of IgG and IgM. Thus, C1qNb75 competitively prevents C1q from binding to IgG and IgM causing blockade of complement activation by the classical pathway. Overall, C1qNb75 represents a high-affinity nanobody-based inhibitor of IgG- and IgM-mediated activation of the classical pathway and may serve as a valuable reagent in mechanistic and functional studies of complement, and as an efficient inhibitor of complement under conditions of excessive CP activation.

Serum Immunoglobulin G of Neuro-Behçet's Disease Patients Reduce Cerebral Expression Levels of Survival Pathway Factors

Objective: Anti-neuronal antibodies are found in sera of neuro-Behçet's disease (NBD) patients. In this study, our aim was to analyze the potential mechanisms by which NBD immunoglobulin (Ig) Gs affect neuronal dysfunction. Materials and Methods: Purified IgGs obtained from pooled sera of six each NBD patients and healthy controls (HCs) were administered to Sprague Dawley rats through intraventricular injection. Control rats received phosphate-buffered saline (PBS) only. Locomotor activity was assessed by open field test on days 0, 10, and 25. Cerebral expression levels of intracellular pathway factors associated with cell survival and viability were measured by real-time polymerase chain reaction. Results: Rats treated with NBD IgG exhibited reduced motor activity. On day 25, the mean number of crossings was 44 ± 7, 90 ± 12, and 93 ± 5 and the mean number of rearings was 18 ± 7, 34 ± 5, and 35 ± 6 for NBD IgG, HC IgG, and PBS groups, respectively (P &lt; 0.001). Relative expression levels of Akt-1 (0.4 ± 0.2, 1.0 ± 0.3, and 0.9 ± 0.6; P = 0.004), DJ-1 (0.6 ± 0.2, 1.0 ± 0.6, and 0.9 ± 0.5; P = 0.047), mouse double mininute-2 (0.5 ± 0.3, 0.9 ± 0.2, and 1.0 ± 0.2; P = 0.002), and mechanistic target of rapamycin (0.4 ± 0.2, 0.8 ± 0.4, and 0.9 ± 0.6; P = 0.006) were significantly lower in NBD-IgG group than HC IgG and PBS groups. By contrast, the expression levels of factors associated with apoptosis (caspase 3, mitochondrial carrier homolog 1, and B-cell lymphoma-2) were comparable among different treatment arms. Conclusion: Our results suggest that at least a fraction of NBD IgG interacts with neuronal surface antigens and subsequently decreases neuronal viability through Akt pathway inhibition. By contrast, NBD IgG does not appear to activate neuronal apoptosis. Further identification of the binding sites of serum IgG ıs required.

Epitope mapping of antibodies induced with a conserved rhinovirus protein generating protective anti-rhinovirus immunity

Human rhinovirus (RV) infections are the principle cause of common colds and precipitate asthma and chronic obstructive pulmonary disease (COPD) exacerbations. Currently there is no vaccine for RV which is largely due to the existence of ∼160 serotypes/strains. We demonstrated previously that immunising mice with highly conserved VP4 and VP2 regions of the RV polyprotein (RV-A16 VP0) generated cross-reactive immunity to RV in vivo. The current study investigated and mapped the epitopes of RV-A16 VP0 that are targets for antibodies in serum samples from VP0 immunisation and RV challenge studies in mice. Recombinant capsid proteins, peptide pools and individual peptides spanning the immunogen sequence (RV-A16 VP0) were assessed for IgG binding sites to identify epitopes. We found that peptide pools covering the C-terminus of VP4, the N-terminus of VP2 and the neutralising NIm-II site within VP2 were bound by serum IgG from immunised mice. The NIm-II site peptide pool blocked IgG binding to the immunogen RV-A16 VP0 and individual peptides within the pool binding IgG were further mapped. Thus, we have identified immunodominant epitopes of RV vaccine candidate RV-A16 VP0, noting that strong IgG binding antibodies were observed that target a key neutralising epitope that is highly variable amongst RV serotypes.

Investigation of the interaction between calreticulin and immunoglobulin G by capillary electrophoresis and computer modeling

Calreticulin (CRT), a highly conserved ubiquitous multifunctional protein, has immense implications in physiological, developmental, and pathological processes due to its interaction with many proteins. In this work, we utilized various capillary electrophoresis (CE) modes for CRT analysis and its interaction with IgG both qualitatively and quantitatively. The interaction was evaluated by capillary zone electrophoresis (CZE) and affinity capillary electrophoresis (ACE) modes that took only 4–6 min for each run. The nanomolar level Kd was determined between CRT and IgG by CZE-LIF and ACE-UV, whereas, CRT did not exhibit any interaction with HSA (as the control protein). By computer modeling, we obtained modeled structures of the CRT-IgG complex which mapped six hot spots on the CRT and IgG interacting interface. Our work is the first report which establishes CE methods for qualitative and quantitative analysis of CRT and IgG interaction. Moreover, the results of computer modeling provide the first molecular insights into the CRT binding sites for IgG that may act as the key anchors and contribute to the interaction studies between CRT and its interacting protein partners.

Pentraxins and Fc Receptor-Mediated Immune Responses.

C-reactive protein (CRP) is a member of the pentraxin family of proteins. These proteins are highly conserved over the course of evolution being present as far back as 250 million years ago. Mammalian pentraxins are characterized by the presence of five identical non-covalently linked subunits. Each subunit has a structurally conserved site for calcium-dependent ligand binding. The biological activities of the pentraxins established over many years include the ability to mediate opsonization for phagocytosis and complement activation. Pentraxins have an important role in protection from infection from pathogenic bacteria, and regulation of the inflammatory response. It was recognized early on that some of these functions are mediated by activation of the classical complement pathway through C1q. However, experimental evidence suggested that cellular receptors for pentraxins also play a role in phagocytosis. More recent experimental evidence indicates a direct link between pentraxins and Fc receptors. The Fc receptors were first identified as the major receptors for immunoglobulins. The avidity of the interaction between IgG complexes and Fc receptors is greatly enhanced when multivalent ligands interact with the IgG binding sites and activation of signaling pathways requires Fc receptor crosslinking. Human pentraxins bind and activate human and mouse IgG receptors, FcγRI and FcγRII, and the human IgA receptor, FcαRI. The affinities of the interactions between Fc receptors and pentraxins in solution and on cell surfaces are similar to antibody binding to low affinity Fc receptors. Crystallographic and mutagenesis studies have defined the structural features of these interactions and determined the stoichiometry of binding as one-to-one. Pentraxin aggregation or binding to multivalent ligands increases the avidity of binding and results in activation of these receptors for phagocytosis and cytokine synthesis. This review will discuss the structural and functional characteristics of pentraxin Fc receptor interactions and their implications for host defense and inflammation.

Chemical modification of protein A chromatography ligands with polyethylene glycol. I: Effects on IgG adsorption equilibrium, kinetics, and transport

Chemical modification of Protein A (ProA) chromatography ligands with polyethylene glycol (PEGylation) has been proposed as a strategy to increase the process selectivity and resin robustness by providing the ligand with a steric repulsion barrier against non-specific binding. This article comprises a comprehensive study of IgG adsorption and transport in Repligen CaptivA PriMAB resin with PEGylated ProA ligands that are modified using 5.2 and 21.5 kDa PEG chains. We studied the impact of the molecular weight of the PEG as well as the extent of PEGylation for the 5.2 kDa PEG modification. In all cases, PEGylation of ProA ligands decreases the resin average pore size, particle porosity, and static binding capacity for IgG proportional to the volume of conjugated PEG in the resin. Resin batch uptake experiments conducted in bulk via a stirred-tank system and with individual resin particles under confocal laser scanning microscopy suggests that PEGylation introduces heterogeneity into IgG binding kinetics: a fraction of the IgG binding sites are transformed from typical fast association kinetic behavior to slow kinetic behavior. pH gradient elution experiments of an IgG molecule on the modified resins show an increase in IgG elution pH for all modified resins, implying a decrease in IgG-ProA binding affinity on modification. Despite losses in static binding capacity for all resins with PEGylated ligands, the loss of dynamic binding capacity at 10% breakthrough (DBC10%) ranged more broadly from almost 0–47% depending on the PEG molecular weight and the extent of PEGylation. Minimal losses in DBC10% were observed with a low extent of PEGylation with a smaller molecular weight PEG, while higher losses were observed at higher extents of PEGylation and with higher molecular weight PEG due to decreased static binding capacity and increased mass transfer resistance. This work provides insight into the practical implications for resin performance if PEGylation is considered as a strategy for selectivity enhancement in affinity chromatography with macromolecular ligands.

Kinetic Analysis of the Multivalent Ligand Binding Interaction between Protein A/G and IgG: A Standard System Setting.

Recombinant protein A/G (PAG) has a sequence coding for eight IgG binding sites and has enhanced interspecies affinity. High-frequency sampling of a PAG titration with IgG produces concentration profiles that are sensitive to the kinetic availability of the binding sites. The full kinetic model developed here for IgG binding sequentially to PAG shows only two distinct kinetic processes, describing an initial rapid association of two antibodies to PAG with a rate constant k-fast = (1.86 ± 0.08) × 106 M-1 s-1 and a slower antibody binding process to all remaining sites, k-slow = (1.24 ± 0.05) × 104 M-1 s-1. At equilibrium (after 1 h), the maximum IgG occupancy of PAG is 2.8 ± 0.5, conflicting with the genetic evidence of eight binding sites and suggesting significant steric hindrance of the neighboring IgG binding sites. The phosphate-buffered saline (PBS) solution defines a standard system setting, and this may be compared with other settings. The mean association rate of PAG-IgGn in the standard setting is 282 ± 20% higher than when PAG is tethered to a surface. A systems biology approach requires that a model parameter set that defines a system in a standard setting should be transferable to another system. The transfer of parameters between settings may be performed using activity coefficients characterizing an effective concentration of species in a system, ai = γici. The activity correction, γ, for the eight-site occupancy is γ = 0.35 ± 0.06, and mapping from the standard setting to the solution setting suggests γPAG-IgG = 0.4 ± 0.03. The role of activity coefficients and transferability of kinetic parameters between system settings is discussed.

Optimizing Immunostaining of Enamel Matrix: Application of Sudan Black B and Minimization of False Positives from Normal Sera and IgGs.

Non-specific fluorescence from demineralized enamel matrix can significantly compromise the immunofluorescence studies and lead to false positives. Our goal was to assess degrees of non-specific binding under different conditions and try to optimize procedures for immunofluorescence studies of forming enamel. Firstly, we compared two methods for background fluorescence elimination, i.e., sodium borohydride and Sudan Black B treatments. The results demonstrated that Sudan Black B is far superior to sodium borohydride in reducing the background fluorescence in dental tissues. We also studied the extent of non-specific binding of normal sera and purified polyclonal immunoglobulins (IgG) from five mammalian species, guinea pig, rat, rabbit, goat, and sheep, over a broad range of dilutions. For all sera tested fluorescence signals increased exponentially from 1:1000 to 1:100. Interestingly, the non-specific binding of sera from rodent species was below that of positive control in the whole range of dilutions. In contrast, incubation with sera from 3 non-rodent species produced much higher signals which surpassed the positive control signal at 1:250~1:500 dilution range. Most of the IgGs didn't show significant non-specific binding within 0.25–5 μg/ml range, except rabbit IgG which demonstrated extremely high affinity to the enamel matrix even at concentrations as low as 1 μg/ml. Further, studies confirmed that Fab fragments of purified normal rabbit IgG, not conserved Fc fragments, were involved in the interactions. Our observations suggest this high affinity is associated with the antigen binding sites of rabbit IgG. We anticipate that our results will help enamel researchers to optimize and standardize their immunochemical procedures.

Local retention of antibodies in vivo with an injectable film embedded with a fluorogen-activating protein

Herein we report an injectable film by which antibodies can be localized in vivo. The system builds upon a bifunctional polypeptide consisting of a fluorogen-activating protein (FAP) and a β-fibrillizing peptide (βFP). The FAP domain generates fluorescence that reflects IgG binding sites conferred by Protein A/G (pAG) conjugated with the fluorogen malachite green (MG). A film is generated by mixing these proteins with molar excess of EAK16-II, a βFP that forms β-sheet fibrils at high salt concentrations. The IgG-binding, fluorogenic film can be injected in vivo through conventional needled syringes. Confocal microscopic images and dose–response titration experiments showed that loading of IgG into the film was mediated by pAGMG bound to the FAP. Release of IgG in vitro was significantly delayed by the bioaffinity mechanism; 26% of the IgG were released from films embedded with pAGMG after five days, compared to close to 90% in films without pAGMG. Computational simulations indicated that the release rate of IgG is governed by positive cooperativity due to pAGMG. When injected into the subcutaneous space of mouse footpads, film-embedded IgG were retained locally, with distribution through the lymphatics impeded. The ability to track IgG binding sites and distribution simultaneously will aid the optimization of local antibody delivery systems.

Targeting FcγRs to treat antibody-dependent autoimmunity.

Self-reactive antibodies represent a significant force in autoimmune disease induction. In antibody-dependent autoimmune syndromes such as immune thrombocytopenia (ITP), systemic lupus erythematosus (SLE), myasthenia gravis and rheumatoid arthritis (RA), autoantibodies exert their inflammatory effect through FcγRs, a well-established class of cell surface receptors that interact with the Fc domain of IgG. Down-regulating FcγR functionality presents an attractive strategy to treat antibody-dependent autoimmune diseases. Various approaches, including nonspecific blocking of the IgG binding site as well as specific targeting using antagonistic monoclonal antibodies, have been explored to modulate the interaction between the Fc portion of IgG and FcγRs. The exquisite specificity and favorable pharmacokinetics of IgG make monoclonal antibodies a preferred choice. Indeed, the first antagonistic monoclonal antibody against the human FcγRIIIA had shown efficacy in refractory ITP patients; however, the practicality of using anti-FcγRIII antibody as a therapeutic was hindered by its associated adverse events, a phenomenon recapitulated in animal models. In this review, we discuss the role of FcγRs in autoimmune diseases, and focus on a novel monovalent approach to target FcγRs to resolve antibody-mediated autoimmunity.

The degree of virulence does not necessarily affect MRSA biofilm strength and response to photodynamic therapy

Biofilm formation transforms infections from acute to chronic, increasing patient mortality and significantly increasing healthcare costs. We are studying the prevalence of some virulence genes among methicillin resistant Staphylococcus aureus (MRSA) isolates relative to biofilm formation and the potential of photoactivated hypericin to treat these infections. Isolates were collected from three Egyptian governorates over seven months in 2011, 100 isolates were identified as MRSA. Biofilm formation was established using crystal violet staining and 2,3,5-triphenyl tetrazolium chloride reduction. Twenty two percent of the isolates formed biofilms, of which 68.2% were moderate to strong. The virulence genes were detected using polymerase chain reaction. spaX (x-region of protein A) was most prevalent. All biofilm-formers lacked cap5 (capsular polysaccharide 5), the other genes were: nuc (thermonuclease) > clfA (clumping factor) > spaIgG (IgG binding site of protein A), fnbA (fibronectin protein A), cap8 (capsular polysaccharide 8), agr (accessory-gene-regulator locus) > fnbB (fibronectin protein B). agr-locus was only found in 22.22% of moderate biofilm-formers, the remaining genes were almost equally prevalent among biofilm-formers and negative controls. Photoactivated hypericin efficiently inhibited 92.2–99.9% of biofilm viability, irrespective of the number of virulence genes. To conclude, biofilm formation, and treatment might be affected by a myriad of virulence factors rather than a single gene, however, photoactivated hypericin remains a potential antibiofilm approach.

Anti-factor H autoantibodies in C3 glomerulopathies and in atypical hemolytic uremic syndrome: one target, two diseases.

Autoantibodies targeting factor H (FH), which is a main alternative complement pathway regulatory protein, have been well characterized in atypical hemolytic uremic syndrome (aHUS) but have been less well described in association with alternative pathway-mediated glomerulopathies (GP). In this study, we studied 17 patients presenting with GP who were positive for anti-FH IgG. Clinical data were collected and biological characteristics were compared with those of patients presenting with anti-FH Ab-associated aHUS. In contrast to the aHUS patients, the GP patients had no circulating FH-containing immune complexes, and their anti-FH IgG had a weaker affinity for FH. Functional studies demonstrated that these Abs induced no perturbations in FH cell surface protection or the binding of FH to its ligand. However, anti-FH IgG samples isolated from three patients were able to affect the factor I cofactor activity of FH. Epitope mapping identified the N-terminal domain of FH as the major binding site for GP patient IgG. No homozygous deletions of the CFHR1 and CFHR3 genes, which are frequently associated with the anti-FH Ab in aHUS patients, were found in the GP patients. Finally, anti-FH Abs were frequently associated with the presence of C3 nephritic factor in child GP patients and with monoclonal gammopathy in adult GP patients, who frequently showed Ig Lchain restriction during reactivity against factor H. These data provide deeper insights into the pathophysiological differences between aHUS and GP, demonstrating heterogeneity of anti-FH IgG.