anti-C5 Antibody Research Articles

Research Highlights

Research Highlights

Complement-mediated release of fibroblast growth factor 2 from human RPE cells

PurposeComplement activation is associated with choroidal neovascularization (CNV) in age-related macular degeneration (AMD). Fibroblast growth factor 2 (FGF2) and membrane attack complex (MAC) are present in eyes of patients with CNV. Herein, we investigated the effect of complement activation on FGF2 release in human retinal pigment epithelial (RPE) cells. MethodsCultured human RPE cells were primed with an anti-RPE antibody and then treated with C1q-depleted human serum in the presence or absence of Tec kinases inhibitor (LFM-A13). 38 cytokines/chemokines levels were measured by Luminex technology. Secretion of FGF2 and interleukin (IL)-6 was assessed by ELISA. Tec protein was measured by Western blot. mRNA expression of FGF2, chemokine (C-X-C motif) ligand 1 (CXCL-1), and family members of Tec kinases was evaluated by qPCR. Cell viability and MAC deposition were determined by WST-1 assay and flow cytometry, respectively. ResultsComplement activation caused increased FGF2 and IL-6 release. FGF2 was released when C6-depleted human serum was reconstituted with C6. Anti-C5 antibody significantly attenuated complement-mediated FGF2 release, but not IL-6. FGF2 mRNA levels were not affected, while CXCL-1 mRNA levels were increased by complement activation. FGF2-containing extracellular vesicles were detected in response to complement challenge. Tec mRNA and protein were expressed in RPE cells. In the presence of LFM-A13, secretion of FGF2, but not IL-6, and MAC deposition were significantly decreased and cell viability was significantly increased in complement-treated cells when compared to controls. ConclusionsComplement plays an important role to release FGF2 from RPE cells. Tec kinase is involved in MAC formation and complement-mediated FGF2 release. This information suggests a role for complement activation to mediate neovascularization in conditions such as AMD, and may elucidate potential therapeutic targets.

Inflammatory stress in SARS-COV-2 associated Acute Kidney Injury

Increasing clinical evidence shows that acute kidney injury (AKI) is a common and severe complication in critically ill COVID-19 patients. The older age, the severity of COVID-19 infection, the ethnicity, and the history of smoking, diabetes, hypertension, and cardiovascular disease are the risk factor for AKI in COVID-19 patients. Of them, inflammation may be a key player in the pathogenesis of AKI in patients with COVID-19. It is highly possible that SARS-COV-2 infection may trigger the activation of multiple inflammatory pathways including angiotensin II, cytokine storm such as interleukin-6 (IL-6), C-reactive protein (CRP), TGF-β signaling, complement activation, and lung-kidney crosstalk to cause AKI. Thus, treatments by targeting these inflammatory molecules and pathways with a monoclonal antibody against IL-6 (Tocilizumab), C3 inhibitor AMY-101, anti-C5 antibody, anti-TGF-β OT-101, and the use of CRRT in critically ill patients may represent as novel and specific therapies for AKI in COVID-19 patients.

Current treatment of paroxysmal nocturnal hemoglobinuria and prospects for new therapeutic agents in the future

Paroxysmal nocturnal hemoglobinuria (PNH) is a hematopoietic stem cell disease whose main symptom is complement-mediated intravascular hemolysis as a result of the clonal expansion of hematopoietic stem cells having mutations in genes involved in glycosylphosphatidylinositol (GPI) anchor synthesis including PIGA. With the advent of a humanized anti-C5 monoclonal antibody (eculizumab), the inhibitory effect on hemolysis, improvement in its various complicating symptoms, and preventive effect on thrombus formation were observed. In addition, the QOL in patients with PNH was significantly improved. Subsequently, the technology of recycling antibodies (ravulizumab and crovalimab) significantly extended the treatment interval and improved convenience, although the poor improvement of anemia due to extravascular hemolysis has been a major issue in some patients. Several clinical trials using proximal complement inhibitors (C3, factor D, factor B) are being conducted to overcome this critical task. Not only efficacy but also safety and convenience will be evaluated, and the best therapeutic agent will be selected in the near future.

A Novel Total Drug Assay for Quantification of Anti-C5 Therapeutic Monoclonal Antibody in the Presence of Abundant Target

SKY59 or RO7112689 is a humanized monoclonal antibody against complement protein C5 with pH-dependent C5-binding and neonatal Fc receptor-mediated recycling capabilities, which result in long-lasting neutralization of C5. We developed and validated a novel total drug assay for quantification of target-binding competent SKY59 in the presence of endogenous C5 in cynomolgus monkey plasma. The target-binding competent SKY59 was determined after complex formation by the addition of recombinant monkey C5 using goat anti-human IgG-heavy chain monkey-adsorbed polyclonal antibody as a capture antibody and rabbit anti-C5 monoclonal antibody (mAb) non-competing with SKY59 for detection. The total SKY59 assay was shown to be accurate and precise over the range of 0.05-3.2μg/mL as well as be tolerant to more than 400μg/mL of C5 (~ 3000-fold molar excess of target). We also developed and validated a total C5 assay, confirmed selectivity and parallelism, and verified the utility of recombinant monkey C5 for the total C5 assay as well as the total SKY59 assay. Furthermore, we used these validated methods to measure SKY59 and C5 concentrations in cynomolgus monkey plasma samples in a toxicology study. This total drug assay can be applied not only to other antibody therapeutics against shed/soluble targets when a non-competing reagent mAb is available but also for clinical studies when a reagent mAb specific for engineered Fc region on a therapeutic mAb is available.

Novel therapeutics for paroxysmal nocturnal hemoglobinuria

Following the reports of paroxysmal nocturnal hemoglobinuria (PNH) due to PIGT and PIGB gene mutations, the definition of PNH was changed to a hematopoietic stem cell disease with complement-mediated intravascular hemolysis as a result of clonal expansion of hematopoietic stem cells with mutations in genes involved in glycosylphosphatidylinositol (GPI) anchor synthesis, including PIGA. Treatment with eculizumab (Soliris®), a humanized anti-C5 monoclonal antibody, significantly improved the quality of life in patients with PNH, remarkably reduced hemolysis, improved symptoms associated with hemolysis, and prevented thrombosis. Although the administration interval has been extended and convenience has been greatly improved using the technique of recycling antibodies (ravulizumab and crovalimab), extravascular hemolysis has become another issue. Although attempts have been made to overcome this issue with proximal complement (C3, factor D, and factor B) inhibitors, the optimal therapeutic agent is expected to be selected after evaluating for not only efficacy and safety but also convenience.

Complement-5 Inhibition Deters Progression of Fulminant Hepatitis to Acute Liver Failure in Murine Models

Background & AimsAcute liver failure (ALF) is a life-threatening condition with limited treatment alternatives. ALF pathogenesis seemingly involves the complement system. However, no complement-targeted intervention has been clinically applied. In this study, we aimed to investigate the potential of Complement-5 (C5)-targeted ALF treatment.MethodsALF was induced in C5-knockout (KO, B10D2/oSn) mice and their wild-type (WT) counterparts (B10D2/nSn) through intraperitoneal lipopolysaccharide (LPS) and d-galactosamine (D-GalN) administration. Thereafter, monoclonal anti-C5 antibody (Ab) or control immunoglobulin was administered intravenously. Furthermore, a selective C5a-receptor (C5aR) antagonist was administered to WT mice to compare its efficacy with that of anti-C5-Ab-mediated total C5 inhibition. We clarified the therapeutic effect of delayed anti-C5-Ab administration after LPS/D-GalN challenge. We also assessed the efficacy of anti-C5-Ab in another ALF model, using concanavalin-A.ResultsLiver injury was evident 6 hours after LPS/D-GalN administration. C5-KO and anti-C5-Ab treatment significantly improved overall animal survival and significantly reduced serum transaminase and high-mobility group box-1 release with decreased histological tissue damage. This improvement was characterized by significantly reduced CD41+ platelet aggregation, maintained F4/80+ cells, and less infiltration of CD11+/Ly6-G+ cells with lower cytokine/chemokine expression. Furthermore, C5-KO and anti-C5-Ab downregulated tumor necrosis factor-α production by macrophages before inducing marked liver injury. Moreover, single-stranded-DNA cells and caspase activation were reduced, indicating significant attenuation of apoptosis. Anti-C5-Ab treatment protected the liver more effectively than the C5aR antagonist, and its delayed doses were hepatoprotective. In addition, anti-C5-Ab treatment was effective against concanavalin-A–induced ALF.ConclusionsC5 inhibition effectively suppresses progression to ALF in mice models of fulminant hepatitis, serving as a new potential treatment strategy for ALF.

Eculizumab-Associated Moraxella lacunata Bacteremia and Systemic Inflammatory Response Syndrome in a Toddler with Atypical Hemolytic Uremic Syndrome

Moraxella lacunata, a low-virulence Gram-negative coccobacillus, is classically associated with conjunctivitis and upper respiratory tract infections; systemic infections such as sepsis have rarely been reported, especially in children. We describe a 28-month-old girl with atypical hemolytic uremic syndrome and stage II chronic kidney disease on long-term eculizumab therapy who presented with systemic inflammatory response syndrome and was found to have Moraxella lacunata bloodstream infection. Eculizumab, a humanized monoclonal anti-C5 antibody, has been associated with susceptibility to infections with encapsulated bacteria, especially Neisseria meningitidis. This is the first report of an invasive bacterial infection with Moraxella lacunata in a pediatric eculizumab recipient.

Feasibility and safety of tailored dosing schedule for eculizumab based on therapeutic drug monitoring: Lessons from a prospective multicentric study.

Eculizumab is an anti-C5 monoclonal antibody approved for rare diseases including atypical haemolytic-uraemic syndrome. The maintenance phase dosing regimen is identical for all adult patients: 1200 mg every 2 weeks. Recent studies reported an overexposure in many patients when considering a target trough concentration range of 50-100 mg/L. The aim of the present work was to validate the feasibility of therapeutic drug monitoring of eculizumab in atypical haemolytic-uraemic syndrome patients. We performed a 2-step prospective multicentre study. In the first phase, we developed a pharmacokinetic population model using data from 40 patients and identified patients for whom a 1-week lengthening of interval between infusions would lead to a trough concentration above 100 mg/L. In the second phase, selected patients were allocated a 1-week extension and eculizumab trough concentrations were monitored. The model confirmed the previously reported influence of bodyweight on elimination clearance and predicted that 36 (90%) patients would be eligible for interval extension. In the second phase of the study, a 1-week lengthening of interval between infusions was performed in 15 patients whose trough concentration at the next visit was predicted with a Bayesian model to be above 100 mg/L. After interval extension, 10 patients (67%) presented measured trough concentrations over 100 mg/L. No biological or clinical recurrence of disease was observed, even in the 5 patients with concentrations below 100 mg/L in whom the initial dosing regimen was resumed. Safe eculizumab interval adjustment is feasible with a PK monitoring.

A Novel pH Dependent C5 Monoclonal Antibody with Better Developability

Introduction: Dysregulation of complement system is the driver of many immune disorder diseases, including paroxysmal nocturnal hemoglobinuria (PNH), atypical hemolytic uremic syndrome (aHUS), and etc. All pathways of complement activation converge at the cleavage of C5, which leads to the generation of membrane attack complex (MAC). The approval of Eculizumab, anti-C5 monoclonal antibody, opened the complement-inhibitor era and proved C5 to be a feasible therapeutic target with manageable risk. Eculizumab and Crovalimab are currently approved for treatment of patients with PNH, yet treatment limitations include hemolysis breakthrough for non-sufficient C5 inhibition, lack of efficacy in patients with C5 mutational variants, and the burden of regular intravenous infusions. The next-generation C5 inhibitor emerges as a new/existing C5 monoclonal antibody engineered to have pH dependence (to reduce dosing frequency), and other new approached to target C5 in complement system. Here we report the results of a novel pH dependent C5 monoclonal antibody-LP-005, to prevent the hemolysis of red blood cells (RBCs) from PNH patients in vitro experiment. Methods: The sequence of Ravulizumab and Crovalimab were obtained from INN. LP-005 was generated using hybridoma method and multidimentionally optimized in variable and content regions. All antibodies were expressed by NHK293 cells. For antibody affinity test, Fortebio Octet K2 was used, different C5 antibodies were first loaded on the AHC sensors and serial diluted recombinant human C5 have been run for global-fit analysis. For antibody biological function test, antibody-sensitized sheep RBCs hemolysis (classic pathway/CP activity) inhibition assay have been run in 1% normal human serum (NHS) with antibodies serial diluted by GVB++ buffer. Antibody-sensitized chicken RBC hemolysis (CP activity) inhibition assay have been run in 6.25% NHS with antibodies serial diluted by GVB++ buffer. Ex vivo inhibition of PNH patients (with more than 70% CD59 deficiency) RBCs hemolysis by anti-C5 antibodies was performed using ABO blood group-compatible serum (20%) under conditions of robust alternative pathway (AP) specific activation (GVB0 + MgEGTA, pH7.3). CD59 deficiency on RBCs of PNH patients has been analyzed by flow cytometry using APC-conjugated anti-human CD59 (negative) and PE-conjugated anti-human CD47 antibodies (positive). Antibody stability test was conducted, antibodies were treated at 66℃ and 67.5℃ for 1hr, and C5 binding activity was then tested using by ELISA. Results: In the present study, we report a novel humanized anti-C5 monoclonal antibody, named LP-005. LP-005, Ravulizumab and Crovalimab exhibits different binding kinetics to C5 (Table 1), however, there is no clear correlation between their binding affinity and complement inhibition activity (NHS-induced CP and AP hemolysis). In antibody-sensitized sheep RBCs hemolysis inhibition assay (CP), LP-005 shows an IC50 of 0.41 nM, whereas Ravulizumab and Crovalimab has IC50 of 0.99 nM and 0.4 nM respectively (Figure 1). For AP induced helmolysis assay, PNH patient's RBCs with more than 70% CD59 absence was used, however, little difference was found between LP-005 and Ravulizumab hemolysis inhibition activity. Moreover, Crovalimab showed incomplete and less efficient inhibition compared with Ravulizumab and LP-005 (Figure 2). The thermal stability study showed that LP-005 is comparable to Crovalimab and is more stable than Ravulizumab (Figure 3). Conclusion: In summary, LP-005 is a novel anti-C5 monoclonal antibody with higher bioactivity in CP induced hemolysis compared to Ravulizumab, and comparable activity in AP induced hemolysis using PNH patient's RBCs. LP-005 is also engineered to increase FcRn binding property as well as thermal stability, which has the potential to be a good drug candidate with improved pharmacokinetic properties of decreasing doses frequency during clinical practice as well as a more robust manufacture process during drug development. Disclosures He: Celgene: Research Funding; furnished by Scott Battle, PhD, of Health Interactions, was funded by F. Hoffmann-La Roche Ltd, Basel, Switzerland: Other: Medical writing support; Celgene, Novartis, Amgen, Ra Pharma, Alexion, Achilleon, Biocryst, Akari, F. Hoffmann-La Roche: Speakers Bureau; Celgene, Novartis, Amgen, Ra Pharma, Alexion, Achilleon, Biocryst, Akari, F. Hoffmann-La Roche: Honoraria; Celgene, Novartis, Amgen, Ra Pharma, Alexion, Achilleon, Biocryst, Akari, Apellis, F. Hoffmann-La Roche: Consultancy.

Crovalimab for Treatment of Patients with Paroxysmal Nocturnal Hemoglobinuria and Complement C5 Polymorphism - Experience from the Phase I/II COMPOSER Study

Crovalimab for Treatment of Patients with Paroxysmal Nocturnal Hemoglobinuria and Complement C5 Polymorphism - Experience from the Phase I/II COMPOSER Study

COMPOSER Part 4: An Optimized Dosing Strategy for Crovalimab in the Treatment of Complement Inhibitor-Naïve or -Experienced Patients with Paroxysmal Nocturnal Hemoglobinuria

COMPOSER Part 4: An Optimized Dosing Strategy for Crovalimab in the Treatment of Complement Inhibitor-Naïve or -Experienced Patients with Paroxysmal Nocturnal Hemoglobinuria

Population Pharmacokinetic/Pharmacodynamic Modelling from the Phase I/II COMPOSER Trial to Predict Lowering of Lactate Dehydrogenase in Crovalimab-Treated Patients with Paroxysmal Nocturnal Hemoglobinuria

Introduction Paroxysmal nocturnal hemoglobinuria (PNH) is a hematopoietic stem cell disorder characterized by intravascular hemolytic anemia and hemoglobinuria. Lactate dehydrogenase (LDH) is a cytoplasmic enzyme that is abundant in red blood cells. Serum LDH level is used as a biomarker for intravascular hemolysis to monitor response to PNH treatment. Crovalimab is a novel antihuman C5 antibody engineered with Sequential Monoclonal Antibody Recycling Technology (SMART-Ig; Fukuzawa et al, Sci Rep. 2017) that is being evaluated as a therapy for PNH in the 4-part, dose-optimization Phase I/II COMPOSER trial (NCT03157635; Röth et al, Blood. 2020), which includes healthy volunteers and patients with PNH who received or did not receive prior C5 inhibition therapy with eculizumab. In this study, COMPOSER data were used to obtain a dose-concentration effect relationship between crovalimab and LDH through development of a pharmacokinetic (PK)-LDH model. Objectives To describe the LDH time course in patients with PNH and to confirm the adequate LDH-lowering effect of the optimized dose and regimen of crovalimab. Study Design and Methods At the clinical data cutoff date of September 4, 2019, data from 15 treatment-naive patients with PNH were used to develop the population PK-LDH model. Observations collected in patients switching treatment from eculizumab to crovalimab (n = 26) were not used to build the PK-LDH model but were used as an external validation tool to evaluate the predictive performance of the model at steady state. A sequential approach was followed (Zhang et al, J Pharmacokinet Pharmacodynam. 2003;30:387-404; Zhang et al, J Pharmacokinet Pharmacodynam. 2003;30:405-416): the individual PK parameters of crovalimab were derived from a population PK model by an empirical Bayesian analysis, and subsequently, the PK-LDH response relationship was modeled with an indirect response model in which LDH synthesis was inhibited by crovalimab concentrations. The predictive performance of the population PK-LDH model was evaluated using a prediction-corrected visual predictive check (pcVPC). The population PK-LDH analysis and all simulations were performed using NONMEM 7.4.0 software. All data sets were analyzed using SAS 9.4. Results For a typical patient, the maximal LDH-lowering effect was estimated to be 80% and the concentration of crovalimab leading to 90% of maximal reduction of LDH synthesis was estimated to be 34.9 μg/mL (90% CI, 15.9-67.5 μg/mL). The half-life for LDH was estimated to be 3 days and steady state for the LDH-lowering effect was predicted to be reached 15 days after first drug intake. The pcVPC in treatment-naive patients showed that the PK-LDH model had good predictive qualities (Figure 1). An external pcVPC was performed in patients who had switched from eculizumab to crovalimab with good predictive qualities, supporting the use of the model for simulation. Using the optimized crovalimab dose and regimen from Part 4, model-based simulations of the LDH time course showed that > 95% of patients were predicted to have LDH levels of ≤ 1.5 × upper limit of normal (ULN) (Figure 2). A sensitivity analysis, to assess the impact of uncertainty around the estimated concentration of crovalimab leading to 90% of maximal reduction of LDH synthesis, found a moderate impact on the predicted LDH-lowering effect of crovalimab, with a small decrease in the percentage of patients predicted to reach an LDH level of < 1.5 × ULN. Conclusions Simulations show a rapid and sustained decrease in LDH levels to < 1.5 × ULN in over 95% of treatment-naive patients with PNH who receive the optimized dose and regimen of crovalimab. The confirmation of the LDH-lowering effect of crovalimab supports further clinical study of the optimized regimen, which is being evaluated in the Phase III studies COMMODORE 1 (NCT04432584) and COMMODORE 2 (NCT04434092). Disclosures Buatois: F. Hoffmann-La Roche Ltd: Current Employment, Other: All authors received support for third-party writing assistance, furnished by Scott Battle, PhD, provided by F. Hoffmann-La Roche, Basel, Switzerland.. Sostelly:F. Hoffmann-La Roche Ltd: Current Employment, Other: All authors received support for third-party writing assistance, furnished by Scott Battle, PhD, provided by F. Hoffmann-La Roche, Basel, Switzerland.. Soubret:F. Hoffmann-La Roche Ltd: Current Employment, Other: All authors received support for third-party writing assistance, furnished by Scott Battle, PhD, provided by F. Hoffmann-La Roche, Basel, Switzerland.. Jaminion:F. Hoffmann-La Roche Ltd: Current Employment, Other: All authors received support for third party writing assistance, furnished by Scott Battle, PhD, provided by F. Hoffmann-La Roche, Basel, Switzerland.. Cosson:F. Hoffmann-La Roche Ltd: Current Employment, Other: All authors received support for third party writing assistance, furnished by Scott Battle, PhD, provided by F. Hoffmann-La Roche, Basel, Switzerland.. OffLabel Disclosure: Crovalimab is an anti-C5 monoclonal antibody being evaluated as a therapy for paroxysmal nocturnal hemoglobinuria

Paroxysmal nocturnal haemoglobinuria (PNH): novel therapies for an ancient disease.

In the UK, early work on paroxysmal nocturnal haemoglobinuria (PNH) was conducted by John Dacie who, at the Hammersmith Hospital, first hypothesised that the PNH abnormality might arise through a somatic mutation; and who outlined with S.M. Lewis the relationship between PNH and aplastic anaemia. When the phosphatidylinositol glycan anchor biosynthesis Class A (PIGA) gene was identified by Taroh Kinoshita's group, jointly with him the Hammersmith group proved that PNH is caused in most patients by a single somatic mutation in the PIGA gene. At the same time, after Bruno Rotoli had spent a sabbatical at the Hammersmith, the 'immune escape model' for the pathogenesis of PNH was developed. Early this century, Peter Hillmen, formerly at the Hammersmith and now in Leeds, spearheaded the use of the complement-blocking (anti-C5) antibody eculizumab. This new medicine radically changed the management and the clinical course of patients with PNH. Recently a derivative of eculizumab with more favourable pharmacokinetics has been introduced. In view of the fact that these agents are associated with C3-dependent extravascular haemolysis, it is important that a number of inhibitors of the proximal complement pathway are now in the offing and may further improve the life of patients with PNH.

Combined liver-kidney transplantation for rare diseases.

Combined liver and kidney transplantation (CLKT) is indicated in patients with failure of both organs, or for the treatment of end-stage chronic kidney disease (ESKD) caused by a genetic defect in the liver. The aim of the present review is to provide the most up-to-date overview of the rare conditions as indications for CLKT. They are major indications for CLKT in children. However, in some of them (e.g., atypical hemolytic uremic syndrome or primary hyperoxaluria), CLKT may be required in adults as well. Primary hyperoxaluria is divided into three types, of which type 1 and 2 lead to ESKD. CLKT has been proven effective in renal function replacement, at the same time preventing recurrence of the disease. Nephronophthisis is associated with liver fibrosis in 5% of cases and these patients are candidates for CLKT. In alpha 1-antitrypsin deficiency, hereditary C3 deficiency, lecithin cholesterol acyltransferase deficiency and glycogen storage diseases, glomerular or tubulointerstitial disease can lead to chronic kidney disease. Liver transplantation as a part of CLKT corrects underlying genetic and consequent metabolic abnormality. In atypical hemolytic uremic syndrome caused by mutations in the genes for factor H, successful CLKT has been reported in a small number of patients. However, for this indication, CLKT has been largely replaced by eculizumab, an anti-C5 antibody. CLKT has been well established to provide immune protection of the transplanted kidney against donor-specific antibodies against class I HLA, facilitating transplantation in a highly sensitized recipient.

Ex vivo assays to detect complement activation in complementopathies

In complement-driven thrombotic microangiopathies, failure to regulate complement activation leads to end-organ damage. The modified Ham (mHam) test measures complement-mediated killing of a nucleated cell in vitro but lacks a confirmatory assay and reliable positive controls. We demonstrate that C5b-9 accumulation on the surface of TF1 PIGAnull cells correlates with cell killing in the mHam. We also show that Sialidase treatment of cells or addition of Shiga toxin 1 to human serum serve as a more reliable positive control for the mHam than cobra venom factor or lipopolysaccharide. Simultaneously performing the mHam and measuring C5b-9 accumulation either in GVB++ or GVB0 MgEGTA buffer with the addition of complement pathway specific inhibitors (anti-C5 antibody or a factor D inhibitor, ACH-145951) can be used to localize defects in complement regulation. As more targeted complement inhibitors become available, these assays may aid in the selection of personalized treatments for patients with complement-mediated diseases.

Severe worsening of myasthenic symptoms after the eculizumab discontinuation

Myasthenia gravis (MG) is an autoantibody-mediated disease of the neuromuscular junction. The neuromuscular junction damage associated with MG is caused by anti-acetylcholine receptor (AChR) antibody and complements. Recently, eculizumab (an anti-C5 monoclonal antibody) was approved for patients with anti-AChR antibody-positive generalized refractory MG. Here, we report a Japanese man with MG who well responded to eculizumab, but experienced acute severe worsening of myasthenic symptoms 2months after its discontinuation. Plasmapheresis did not improve his symptoms; hence, eculizumab was re-administered, resulting in a dramatic response within a week. This is an informative case because eculizumab discontinuation in patients with MG has been very rarely reported. If eculizumab treatment is clinically well effective and AChR antibody titer does not decrease, clinicians should be aware that acute and critical deterioration of MG may occur after the eculizumab discontinuation.

Biotechnological products for the treatment of complement system disorders including paroxysmal nocturnal hemoglobinuria: currently available and in development

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare acquired clonal blood disorder caused by somatic mutations in phosphatidylinositol glycan, class A gene (PIG-A) in hematopoietic stem cells which manifests as haemolytic anemia, bone marrow failure, thromboses, impaired renal function, and other severe clinical symptoms. The management of PNH is a clinical challenge requiring a comprehensive approach. Over the past decade, target therapy with eculizumab, an antibody inhibitor of terminal complement activation, has played a key role in the treatment of PNH. Eculizumab is the first humanized anti-C5 monoclonal antibody that was proven effective in inhibiting the complement system and was approved as a standard treatment for PNH in many countries. Elizaria, the first biosimilar version of eculizumab, whose similarity to the original drug in terms of efficacy and safety was demonstrated in clinical trials, has been widely used in Russia since 2019. New complement inhibitors classified by their mechanism of action into inhibitors targeting complement component C5 (the terminal pathway) and those targeting early phases of complement activation cascade (the proximal pathway) are currently in development. These new drugs include monoclonal antibodies, small molecules, small peptide inhibitors, small interfering RNA, and recombinant proteins based on endogenous regulators of complement activation.

Modeling the activation of the alternative complement pathway and its effects on hemolysis in health and disease.

The complement system is a powerful mechanism of innate immunity poised to eliminate foreign cells and pathogens. It is an intricate network of >35 proteins, which, once activated, leads to the tagging of the surface to be eliminated, produces potent chemoattractants to recruit immune cells, and inserts cytotoxic pores into nearby lipid surfaces. Although it can be triggered via different pathways, its net output is largely based on the direct or indirect activation of the alternative pathway. Complement dysregulation or deficiencies may cause severe pathologies, such as paroxysmal nocturnal hemoglobinuria (PNH), where a lack of complement control proteins leads to hemolysis and life-threatening anemia. The complexity of the system poses a challenge for the interpretation of experimental data and the design of effective pharmacological therapies. To address this issue, we developed a mathematical model of the alternative complement pathway building on previous modelling efforts. The model links complement activation to the hemolytic activity of the terminal alternative pathway, providing an accurate description of pathway activity as observed in vitro and in vivo, in health and disease. Through adjustment of the parameters describing experimental conditions, the model was capable of reproducing the results of an array of standard assays used in complement research. To demonstrate its clinical applicability, we compared model predictions with clinical observations of the recovery of hematological biomarkers in PNH patients treated with the complement inhibiting anti-C5 antibody eculizumab. In conclusion, the model can enhance the understanding of complement biology and its role in disease pathogenesis, help identifying promising targets for pharmacological intervention, and predict the outcome of complement-targeting pharmacological interventions.

Atypical hemolytic and uremic syndrome due to C3 mutation in pancreatic islet transplantation: a case report

BackgroundWe here report on the first observation of a C3 mutation that is related to atypical hemolytic and uremic syndrome (aHUS), which occurred in a pancreatic islet transplant patient. Immunosuppressive treatments, such as calcineurin inhibitors, have been linked to undesirable effects like nephrotoxicity.Case presentationA 40-year-old man with brittle diabetes, who was included in the TRIMECO trial, became insulin-independent 2 months after pancreatic islet transplantation. About 15 months after islet transplantation, the patient exhibited acute kidney injury due to aHUS. Despite plasma exchange and eculizumab treatment, the patient developed end-stage renal disease.A genetic workup identified a missense variant (p.R592Q) in the C3 gene. In vitro, this C3 variant had defective Factor I proteolytic activity with membrane proteins as cofactor proteins, which was thus classified as pathogenic. About 1 year after the aHUS episode, kidney transplantation was carried out under the protection of the specific anti-C5 monoclonal antibody eculizumab. The patient had normal kidney function, with preserved pancreatic islet function 4 years later.ConclusionsPancreatic islet transplantation could have triggered this aHUS episode, but this link needs to be clarified. Although prophylactic eculizumab maintains kidney allograft function, its efficacy still needs to be studied in larger populations.