Anticomplement C5 therapy with eculizumab for the treatment of paroxysmal nocturnal hemoglobinuria and atypical hemolytic uremic syndrome

Reconstitution of the alternative pathway of the complement system enables rapid delineation of the mechanism of action of novel inhibitors

The complement system plays a critical role in the innate immune response, acting as a first line of defense against invading pathogens. However, dysregulation of the complement system is implicated in the pathogenesis of numerous diseases, ranging from Alzheimer's to age-related macular degeneration (AMD) and rare blood disorders. As such, complement inhibitors have enormous potential to alleviate disease burden. While a few complement inhibitors are in clinical use, there is still a significant unmet medical need for the discovery and development of novel inhibitors to treat patients suffering from disorders of the complement system. A key hurdle in the development of complement inhibitors has been the determination of their mechanism of action. Progression along the complement cascade involves the formation of numerous multimeric protein complexes, creating the potential for inhibitors to act at multiple nodes in the pathway. This is especially true for molecules that target the central component C3 and its fragment C3b, which serve a dual role as a substrate for the C3 convertases and as a scaffolding protein in both the C3 and C5 convertases. Here, we report a step-by-step in vitro reconstitution of the complement alternative pathway using bio-layer interferometry. By physically uncoupling each step in the pathway, we were able to determine the kinetic signature of inhibitors that act at single steps in the pathway and delineate the full mechanism of action of known and novel C3 inhibitors. The method could have utility in drug discovery and further elucidating the biochemistry of the complement system.

Targeting the Complement-Sphingolipid System in COVID-19 and Gaucher Diseases: Evidence for a New Treatment Strategy

Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2)-induced disease (COVID-19) and Gaucher disease (GD) exhibit upregulation of complement 5a (C5a) and its C5aR1 receptor, and excess synthesis of glycosphingolipids that lead to increased infiltration and activation of innate and adaptive immune cells, resulting in massive generation of pro-inflammatory cytokines, chemokines and growth factors. This C5a-C5aR1-glycosphingolipid pathway- induced pro-inflammatory environment causes the tissue damage in COVID-19 and GD. Strikingly, pharmaceutically targeting the C5a-C5aR1 axis or the glycosphingolipid synthesis pathway led to a reduction in glycosphingolipid synthesis and innate and adaptive immune inflammation, and protection from the tissue destruction in both COVID-19 and GD. These results reveal a common involvement of the complement and glycosphingolipid systems driving immune inflammation and tissue damage in COVID-19 and GD, respectively. It is therefore expected that combined targeting of the complement and sphingolipid pathways could ameliorate the tissue destruction, organ failure, and death in patients at high-risk of developing severe cases of COVID-19.

Treatment of Autoimmune Diseases with Therapeutic Antibodies: Lessons Learned from PID Patients Allow for Stratification of the Infection Risk

Over the years, a wide variety of therapeutic antibodies has been successfully introduced in the autoimmunology clinic and many more are on the edge to follow. Many of these treatments address either a pathogenic circulating molecule or a cell-bound molecule. Whereas the former target results in neutralization of the soluble factor, the latter target either inhibits cellular function or induces selective cell death. If this targeted molecule or cell is part of the immune system, this therapy evokes a state of immunodeficiency. Knowing the exact function of the respective components enables the risk stratification for possible infectious complications in patients treated with biologics. Much of the understanding of the function of immune cells and their associated molecules, in relation to redundancy in the immune system, is derived from studies in knockout mice. However, as mice are not men in terms of their life-expectancy, their infection exposure, or the composition of their immune system, the most useful knowledge for estimating the consequence of therapeutic intervention on immune competence comes from monitoring patients. In the current chapter, we focus on patients with a primary immunodeficiency (PID) because they provide us with a unique perspective to estimate the redundancy of a certain genetic defect for overall immune competence. These patients have inborn errors of the immune system that, in general, are due to single gene defects. Depending on the immunological pathway that is defective, patients can present with different types of (opportunistic) infectious diseases, as well as other clinical manifestations. Based on selected examples, we focus in this chapter on finding parallels in the infectious risk of autoimmune patients treated with biologics and PID patients with a defect in the immunological pathway that is affected by the respective biologic. The goal is to learn from the (dis)similarities between both patient populations in terms of safety profiles of biologic treatments.

Long-Term Efficacy and Safety of the Long-Acting Complement C5 Inhibitor Ravulizumab for the Treatment of Atypical Hemolytic Uremic Syndrome in Adults

Introduction

Atypical hemolytic uremic syndrome (aHUS) is a rare, complex, multisystem disease of dysregulated complement activity, characterized by progressive thrombotic microangiopathy (TMA), acute kidney injury, and multiorgan dysfunction, which often progresses to chronic kidney disease. Results from the prospective clinical trial of ravulizumab (NCT02949128) reveal rapid resolution of TMA in patients with aHUS, with sustained efficacy and safety in a 26-week initial evaluation period.

Methods

The aim of this analysis was to characterize the long-term efficacy and the safety profile of ravulizumab in adults with aHUS who had completed the initial evaluation period of the trial. Complete TMA response, hematologic and kidney functions, and safety were evaluated for all patients available for follow-up in the extension period (median follow-up: 76.7 weeks; range: 0.6–118.3). This trial included a total of 58 patients, 49 of whom entered the extension period.

Results

A total of 4 additional patients achieved complete TMA response during the follow-up period. Normalization of platelet count, serum lactate dehydrogenase (LDH), and hemoglobin observed in the 26-week initial evaluation period was sustained until the last available follow-up, as were the improvements in the estimated glomerular filtration rate (eGFR) and patient quality of life. All efficacy endpoints were correlated with the sustained inhibition of complement C5. Most adverse events (AEs) occurred early during the initial evaluation period and decreased substantially during the extension period. No patient developed a meningococcal infection or died during the extension period.

Conclusion

This analysis reveals that ravulizumab administered every 8 weeks is efficacious with an acceptable safety profile for the long-term treatment of adults with aHUS and provides additional clinical benefit beyond 6 months of treatment.

Interventions for atypical haemolytic uraemic syndrome

BACKGROUND

Atypical haemolytic uraemic syndrome (aHUS) is a rare disorder characterised by thrombocytopenia, microangiopathic haemolytic anaemia, and acute kidney injury. The condition is primarily caused by inherited or acquired dysregulation of complement regulatory proteins with ~40% of those affected aged < 18 years. Historically, kidney failure and death were common outcomes, however, improved understanding of the condition has led to discovery of novel therapies.

OBJECTIVES

To evaluate the benefits and harms of interventions for aHUS.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies for randomised controlled studies (RCTs) up to 3 September 2020 using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Register (ICTRP) Search Portal and ClinicalTrials.gov. MEDLINE(OVID) 1946 to 27 July 2020 and EMBASE (OVID) 1974 to 27 July 2020 were searched for non-RCTs.

SELECTION CRITERIA

All randomised and non-randomised clinical trials comparing an intervention with placebo, an intervention with supportive therapy, or two or more interventions for aHUS were included. Given the rare nature of the condition in question, prospective single-arm studies of any intervention for aHUS were also included.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted pre-specified data from eligible studies and evaluated risk of bias using a newly developed tool based on existing Cochrane criteria. As statistical meta-analysis was not appropriate, qualitative analysis of data was then performed.

MAIN RESULTS

We included five single-arm studies, all of which evaluated terminal complement inhibition for the treatment of aHUS. Four studies evaluated the short-acting C5 inhibitor eculizumab and one study evaluated the longer-acting C5 inhibitor ravulizumab. All included studies within the review were of non-randomised, single-arm design. Thus, risk of bias is high, and it is challenging to draw firm conclusions from this low-quality evidence. One hundred patients were included within three primary studies evaluating eculizumab, with further data reported from 37 patients in a secondary study. Fifty-eight patients were included in the ravulizumab study. After 26 weeks of eculizumab therapy there were no deaths and a 70% reduction in the number of patients requiring dialysis. Complete thrombotic microangiopathic (TMA) response was observed in 60% of patients at 26 weeks and 65% at two years. After 26 weeks of ravulizumab therapy four patients had died (7%) and complete TMA response was observed in 54% of patients. Substantial improvements were seen in estimated glomerular filtration rate and health-related quality of life in both eculizumab and ravulizumab studies. Serious adverse events occurred in 42% of patients, and meningococcal infection occurred in two patients, both treated with eculizumab.

AUTHORS' CONCLUSIONS

When compared with historical data, terminal complement inhibition appears to offer favourable outcomes in patients with aHUS, based upon very low-quality evidence drawn from five single-arm studies. It is unlikely that an RCT will be conducted in aHUS and therefore careful consideration of future single-arm data as well as longer term follow-up data will be required to better understand treatment duration, adverse outcomes and risk of disease recurrence associated with terminal complement inhibition.

NHDL, a recombinant VL/VH hybrid antibody control for IgG2/4 antibodies

The mechanism of action of recombinant IgG2/4 antibodies involves blocking of their target without the induction of effector functions. Examples are eculizumab (Soliris®), which is used clinically to block complement factor C5, as well as anti-human CD14 (r18D11) and anti-porcine CD14 (rMIL2) produced in our laboratory. So far, no proper IgG2/4 control antibody has been available for controlled validation of IgG2/4 antibody functions. Here, we describe the design of a recombinant control antibody (NHDL), which was generated by combining the variable light (V_L) and heavy (V_H) chains from two unrelated specificities. NHDL was readily expressed and purified as a stable IgG2/4 antibody, and showed no detectable specificity toward any putative antigen present in human or porcine blood. The approach of artificial V_L/V_H combination may be adopted for the design of other recombinant control antibodies.

Insights into Potential Targets for Therapeutic Intervention in Epilepsy

Epilepsy is a chronic brain disease that affects approximately 65 million people worldwide. However, despite the continuous development of antiepileptic drugs, over 30% patients with epilepsy progress to drug-resistant epilepsy. For this reason, it is a high priority objective in preclinical research to find novel therapeutic targets and to develop effective drugs that prevent or reverse the molecular mechanisms underlying epilepsy progression. Among these potential therapeutic targets, we highlight currently available information involving signaling pathways (Wnt/β-catenin, Mammalian Target of Rapamycin (mTOR) signaling and zinc signaling), enzymes (carbonic anhydrase), proteins (erythropoietin, copine 6 and complement system), channels (Transient Receptor Potential Vanilloid Type 1 (TRPV1) channel) and receptors (galanin and melatonin receptors). All of them have demonstrated a certain degree of efficacy not only in controlling seizures but also in displaying neuroprotective activity and in modifying the progression of epilepsy. Although some research with these specific targets has been done in relation with epilepsy, they have not been fully explored as potential therapeutic targets that could help address the unsolved issue of drug-resistant epilepsy and develop new antiseizure therapies for the treatment of epilepsy.

Antibody-medicated rejection after heart transplantation: diagnosis and clinical implications

PURPOSE OF REVIEW

The present article will review the diagnosis of antibody-mediated rejection in heart transplant recipients and further explore the clinical implications.

RECENT FINDINGS

Improved diagnostic techniques have led to increased recognition of antibody-mediated rejection and better understanding of the long-term consequences in heart transplant recipients. Endomyocardial biopsy remains the gold standard for the diagnosis of antibody-medicated ejection; however, several advances in molecular testing have emerged, including the use of gene expression profiling, messenger RNA, and microRNA. Routine surveillance of donor-specific antibodies identifies recipients at high risk for graft compromise. Additionally, new monoclonal antibody therapies have broadened our repertoire in the treatment of rejection.

SUMMARY

Advances in molecular testing for antibody-mediated rejection may improve the associated long-term complication, while minimizing risk to the patient.

Pharmacokinetic and Pharmacodynamic Properties of Cemdisiran, an RNAi Therapeutic Targeting Complement Component 5, in Healthy Subjects and Patients with Paroxysmal Nocturnal Hemoglobinuria

BACKGROUND

Cemdisiran, an N-acetylgalactosamine (GalNAc) conjugated RNA interference (RNAi) therapeutic, is currently under development for the treatment of complement-mediated diseases by suppressing liver production of complement 5 (C5) protein. This study was designed to evaluate the safety, tolerability, pharmacokinetics (PK), and pharmacodynamics (PD) of cemdisiran in healthy subjects and in patients with paroxysmal nocturnal hemoglobinuria (PNH) in order to support dose selection for late-stage clinical trials.

METHODS

Healthy volunteers (HVs; n = 32, including 12 Japanese subjects) were randomized (3:1) to receive single doses of subcutaneous cemdisiran (50-900 mg) or placebo, or repeat doses of subcutaneous cemdisiran (100-600 mg) or placebo weekly, biweekly, weekly/biweekly, or weekly/monthly for 5, 8, or 13 weeks (n = 24). Cemdisiran 200 or 400 mg was administered weekly in an open-label manner, for varying durations, as monotherapy in three eculizumab-naïve PNH patients or in combination with eculizumab in three PNH patients who were receiving stable label doses of eculizumab (900 or 1200 mg biweekly) before the start of the study. After the last dose of cemdisiran, patients were followed for safety and ongoing pharmacologic effects with the eculizumab regimen (600 or 900 mg every month).

RESULTS

In HVs, cemdisiran was rapidly converted to a major active metabolite, AS(N-2)3'-cemdisiran, both declining below the lower limit of quantification (LLOQ) in plasma within 48 h, and showing minimal renal excretion. AS(N-2)3'-cemdisiran exhibited more than dose-proportional PK. The C5 protein reductions were dose-dependent, with > 90% reduction of C5 protein beginning on days 21-28 and maintained for 10-13 months following single and biweekly doses of 600 mg. The dose-response relationship, described by an inhibitory sigmoid maximum effect (E_max) model, estimated half-maximal effective dose (ED₅₀) of 14.0 mg and maximum C5 reduction of 99% at 600 mg. The PK and PD were similar between Japanese and non-Japanese subjects, and PNH patients and HVs. One of 48 subjects tested transiently positive for antidrug antibody with low titer, with no impact on PK or PD. In PNH patients, C5 suppression by cemdisiran enabled effective inhibition of residual C5 levels with lower dose and/or dosing frequency of eculizumab, which was maintained for 6-10 months after the last dose of cemdisiran.

CONCLUSIONS

Consistent with the PK/PD properties of liver targeting GalNac conjugates, cemdisiran and AS(N-2)3'-cemdisiran plasma concentrations declined rapidly while showing rapid and robust C5 suppression maintained up to 13 months following single and multiple doses, which indicates long residence times of cemdisiran within hepatocytes. The long PD duration of action in liver, low immunogenicity and acceptable safety profiles enables low, infrequent SC dosing and support further evaluation of cemdisiran in complement-mediated diseases as monotherapy or in combination with a C5 inhibitor antibody.

CLINICAL TRIAL REGISTRATION NO

NCT02352493.

Novel β-Coronavirus (SARS-CoV-2): Current and future aspects of pharmacological treatments

The novel coronavirus outbreak has reported to be rapidly spreading across the countries and becomes a foremost community health alarm. At present, no vaccine or specific drug is on hand for the treatment of this infectious disease. This review investigates the drugs, which are being evaluated and found to be effective against nCOVID-19 infection. A thorough literature search was performedon the recently published research papers in between January 2020 to May 2020, through various databases like "Science Direct", "Google Scholar", "PubMed","Medline", "Web of Science", and "World Health Organization (WHO)". We reviewed and documented the information related with the current and future aspects for the management and cure of COVID-19. As of 21st July 2020 a total of 14,562,550 confirmed cases of coronavirus and 607,781 deaths have been reported world-wide. The main clinical feature of COVID-19 ranges from asymptomatic disease to mild lower respiratory tract illness to severe pneumonia, acute lung injury, acute respiratory distress syndrome (ARDS), multiple organ dysfunction, and death. The drugs at present used in COVID-19 patients and ongoing clinical trials focusing on drug repurposing of various therapeutic classes of drug e.g. antiviral, anti-inflammatory and/or immunomodulatory drugs along with adjuvant/supportive care. Many drugs on clinical trials shows effective results on preliminary scale and now used currently in patients. Adjuvant/supportive care therapy are used in patients to get the best results in order to minimize the short and long-term complications. However, further studies and clinical trials are needed on large scale of population to reach any firm conclusion in terms of its efficacy and safety.

Eculizumab in the treatment of neuromyelitis optica spectrum disorder

Neuromyelitis optica spectrum disorder (NMOSD) is a rare autoimmune disease of the CNS which is distinct from multiple sclerosis and typically presents with a relapsing course of optic neuritis, myelitis and midline brain inflammatory lesions. In at least two-thirds of cases, antibodies against the water channel AQP4 can be found, which lead to an antibody-mediated activation of the complement system with consecutive damage to neuronal structures. Eculizumab, a humanized monoclonal antibody against the terminal complement component 5, was shown to significantly reduce the risk of NMOSD relapse in a Phase III placebo-controlled trial. Based on this, eculizumab (Soliris^®) was the first drug to be formally approved for the treatment of anti-AQP4-antibody positive NMOSD in 2019.

Postpartum atypical hemolytic uremic syndrome: Evaluating thrombotic microangiopathy in the pregnant woman

Acute kidney injury in women during pregnancy and the puerperium is often ascribed to hypertensive complications of pregnancy, especially pre-eclampsia. However, rarer causes, including atypical hemolytic uremic syndrome (aHUS) can be triggered by pregnancy. We present a case of a woman with post-partum acute kidney injury due to aHUS, which was successfully treated with the C5a inhibitor eculizumab. We also present a summary of the evaluation and management of thrombotic microangiopathy in pregnancy.

Inhibition of complement pathway activation with Pozelimab, a fully human antibody to complement component C5

Complement is a key component of the innate immune system. Inappropriate complement activation underlies the pathophysiology of a variety of diseases. Complement component 5 (C5) is a validated therapeutic target for complement-mediated diseases, but the development of new therapeutics has been limited by a paucity of preclinical models to evaluate the pharmacokinetic (PK) and pharmacodynamic (PD) properties of candidate therapies. The present report describes a novel humanized C5 mouse and its utility in evaluating a panel of fully human anti-C5 antibodies. Surprisingly, humanized C5 mice revealed marked differences in clearance rates amongst a panel of anti-C5 antibodies. One antibody, pozelimab (REGN3918), bound C5 and C5 variants with high affinity and potently blocked complement-mediated hemolysis in vitro. In studies conducted in both humanized C5 mice and cynomolgus monkeys, pozelimab demonstrated prolonged PK and durable suppression of hemolytic activity ex vivo. In humanized C5 mice, a switch in dosing from in-house eculizumab to pozelimab was associated with normalization of serum C5 concentrations, sustained suppression of hemolytic activity ex vivo, and no overt toxicity. Our findings demonstrate the value of humanized C5 mice in identifying new therapeutic candidates and treatment options for complement-mediated diseases.

Effect of anti-C5 antibody on recuperation from ischemia/reperfusion-induced acute kidney injury

Aim: The complement system is activated in acute kidney injury (AKI). Anti-C5 antibody targets the common terminal portion of the complement cascade that generate the terminal complex C5b-9 and has a renal-protective effect in paroxysmal nocturnal hemoglobinuria. However, the anti-C5 antibody’s role in ischemia/reperfusion (I/R)-induced AKI has not been fully investigated. We therefore evaluated its effect on the pathophysiological cascade of I/R-induced AKI.

Methods: Sprague–Dawley rats underwent unilateral right kidney nephrectomies with simultaneous clamping of the contralateral hilum for 60 min (ischemia), followed by reperfusion. In addition to a placebo, two treatment groups received either high or low doses of anti-C5 monoclonal antibody. After 48 h, the rats were euthanized, blood was drawn to evaluate systemic inflammation and to estimate glomerular filtration rate (GFR). The remaining kidney was removed for pathological evaluation and intra-renal complement activation.

Results: I/R induced significant intra-renal complement activation and systemic inflammation compared with unilateral nephrectomy group. The anti-C5 antibody ameliorated the intra-renal complement activation (intra-renal C3 and C6), reduced systemic inflammation (C-reactive protein, and systemic C3), decreased intra-renal acute tubular necrosis damage and improved GFR (seen by the sensitive marker, serum cystatin C; 1.63 mg/L (I/R + placebo), 1.36 mg/L (I/R + low dose) and 1.21 mg/L (I/R + high dose), p = .08 and .03 compared with I/R + placebo).

Conclusion: In I/R-induced AKI, the monoclonal anti-C5 complement factor ameliorates intra renal complement activation, decreases local and systemic inflammation and may improve GFR.

The role of complement in antineutrophil cytoplasmic antibody-associated vasculitis

PURPOSE OF REVIEW

To provide a comprehensive overview of the current insight into the role of complement activation in antineutrophil cytoplasmic antibody-associated vasculitis (AAV). In addition, the therapeutic options targeting the complement system in AAV are discussed.

RECENT FINDINGS

It has become increasingly clear that complement, and more specifically signalling through the C5a receptor, contributes to the immunopathology of AAV. This has led to the design of clinical trials with a C5a receptor blocker. The first results show a reduction in tissue damage and a favourable safety profile, as other parts of the complement defence system are left intact.

SUMMARY

Although AAV was initially regarded as a pauci-immune disease, it is now well established that, in addition to autoantibodies, complement plays an essential role in the disease process. Animal models delivered the first insight, but the effective therapeutic interventions using complement inhibitors provided the proof that indeed complement activation contributes to disease activity and tissue damage in human AAV.

Myasthenia gravis: State of the art and new therapeutic strategies

Myasthenia Gravis (MG) - an autoimmune neuromuscular disease - is known by the production of autoantibodies against components of the neuromuscular junction mainly to the acetylcholine receptor, which cause the destruction and compromises the synaptic transmission. This disease is characterized by fluctuating and fatigable muscle weakness, becoming more intensive with activity, but with an improvement under resting. There are many therapeutic strategies used to alleviate MG symptoms, either by improving the transmission of the nerve impulse or by ameliorating autoimmune reactions with e.g. steroids, immunosuppressant drugs, or monoclonal antibodies (rituximab and eculizumab). Many breakthroughs in the discovery of new therapeutic targets have been reported, but MG remains to be a chronic disease where the symptoms are kept in the majority of patients. In this review, we discuss the different therapeutic strategies that have been used over the years to alleviate MG symptoms, as well as innovative therapeutic approaches currently under study.

Analysis of the Complement System in the Clinical Immunology Laboratory

The complement system is a critical component of both the innate and adaptive immune systems that augments the function of antibodies and phagocytes. Antigen-antibody immune complexes, lectin binding, and accelerated C3 tick-over can activate this well-coordinated and carefully regulated process. The importance of this system is highlighted by the disorders that arise when complement components or regulators are deficient or dysregulated. This article describes the pathways involved in complement activation and function, the regulation of these various pathways, and the interpretation of laboratory testing performed for the diagnosis of diseases of complement deficiency, exuberant complement activation, and complement dysregulation.

Reduced membrane attack complex formation in umbilical cord blood during Eculizumab treatment of the mother: a case report

Background

Atypical hemolytic uremic syndrome (aHUS) is a disorder of the microvasculature with hemolytic anemia, thrombocytopenia and acute kidney injury. Nowadays, aHUS is successfully treated with eculizumab, a humanized, chimeric IgG2/4 kappa antibody, which binds human complement C5 and blocks generation of C5a and membrane-attack-complex.

Case presentation

A 25-year-old woman with end stage renal disease due to relapsing atypical hemolytic uremic syndrome had a relapse of the disease during pregnancy. She was treated with eculizumab. We measured reduced formation of the membrane-attack complex in newborn’s umbilical cord vein blood using the sensitive and specific Palarasah-Nielsen-ELISA.

Conclusions

Eculizumab treatment of the mother with end stage renal disease may cause reduced innate immunity which could render newborns more susceptible to infections.

Eculizumab Safety: Five-Year Experience From the Global Atypical Hemolytic Uremic Syndrome Registry

Introduction

Eculizumab has transformed outcomes for patients with atypical hemolytic uremic syndrome (aHUS). Its efficacy and safety profile was well characterized in the clinical trial program. The long-term safety profile was not previously assessed or compared against nontreated patients in an observational registry setting.

Methods

The Global aHUS Registry recruits patients with clinical diagnoses of aHUS. This analysis includes baseline characteristics and targeted safety events from adult and pediatric patients who were "ever treated" versus "never treated" with eculizumab in the first 5 years of the registry, through January 26, 2017.

Results

Overall, 1321 patients (adult, n = 842; pediatric, n = 479; ever treated, n = 865; never treated, n = 456) were enrolled. A higher proportion of ever-treated versus never-treated adult and pediatric patients had renal, cardiovascular, pulmonary, central nervous system, gastrointestinal symptoms, and hepatic impairment. No differences in safety event rates between ever-treated and never-treated patients were observed, except serious infections in pediatric patients (5.15 versus 1.12 events/100 patient-years for ever- and never-treated patients, respectively). Deaths were more frequent in adult (4.7% and 9.9% of ever- and never-treated patients) compared with pediatric patients (1.8% of ever-treated patients; no deaths in never-treated patients).Three meningococcal infections were reported in ever-treated patients; 1 infection led to a fatal outcome.

Conclusion

In this large observational dataset covering 5 years of registry enrollment, no new safety concerns were identified for adult or pediatric eculizumab-treated patients with aHUS, confirming a positive benefit-risk profile in a real-world setting.

ANCA associated vasculitis: The journey to complement-targeted therapies

ANCA associated vasculitis is a serious, very often recurrent disease that despite the current standard treatment with high-dose glucocorticoids and either cyclophosphamide or rituximab, patients have a nine-fold increased mortality risk in the first year compared with healthy controls, attributed to infections, vasculitis activity, and renal disease. During the last few years, novel findings have suggested that activation of the complement system, in particular the alternative complement system, has a significant role in ANCA associated vasculitis pathogenesis. Detection of several components of this system in the circulation and urine reflects disease activity, and thus may be useful for clinical prognosis and to set up personalised treatments. In fact, some components of the complement system, such as C5a, might be potential targets for therapy. In this Review an update on clinical evidence for the role of complement activation in AAV is provided and subsequently we discuss potential therapeutic strategies that target complement components and open the way for clinical use of this target therapy in the near future.

Advances in the Potential Biomarkers of Epilepsy

Epilepsy is a group of chronic neurological disorders characterized by recurrent, spontaneous, and unpredictable seizures. It is one of the most common neurological disorders, affecting tens of millions of people worldwide. Comprehensive studies on epilepsy in recent decades have revealed the complexity of epileptogenesis, in which immunological processes, epigenetic modifications, and structural changes in neuronal tissues have been identified as playing a crucial role. This review discusses the recent advances in the biomarkers of epilepsy. We evaluate the possible molecular background underlying the clinical changes observed in recent studies, focusing on therapeutic investigations, and the evidence of their safety and efficacy in the human population. This article reviews the pathophysiology of epilepsy, including recent reports on the effects of oxidative stress and hypoxia, and focuses on specific biomarkers and their clinical implications, along with further perspectives in epilepsy research.

Recombinant Production of MFHR1, A Novel Synthetic Multitarget Complement Inhibitor, in Moss Bioreactors

The human complement system is an important part of the immune system responsible for lysis and elimination of invading microorganisms and apoptotic body cells. Improper activation of the system due to deficiency, mutations, or autoantibodies of complement regulators, mainly factor H (FH) and FH-related proteins (FHRs), causes severe kidney and eye diseases. However, there is no recombinant FH therapeutic available on the market. The first successful recombinant production of FH was accomplished with the moss bioreactor, Physcomitrella patens. Recently, a synthetic regulator, MFHR1, was designed to generate a multitarget complement inhibitor that combines the activities of FH and the FH-related protein 1 (FHR1). The potential of MFHR1 was demonstrated in a proof-of-concept study with transiently transfected insect cells. Here, we present the stable production of recombinant glyco-engineered MFHR1 in the moss bioreactor. The key features of this system are precise genome engineering via homologous recombination, Good Manufacturing Practice-compliant production in photobioreactors, high batch-to-batch reproducibility, and product stability. Several potential biopharmaceuticals are being produced in this system. In some cases, these are even biobetters, i.e., the recombinant proteins produced in moss have a superior quality compared to their counterparts from mammalian systems as for example moss-made aGal, which successfully passed phase I clinical trials. Via mass spectrometry-based analysis of moss-produced MFHR1, we now prove the correct synthesis and modification of this glycoprotein with predominantly complex-type N-glycan attachment. Moss-produced MFHR1 exhibits cofactor and decay acceleration activities comparable to FH, and its mechanism of action on multiple levels within the alternative pathway of complement activation led to a strong inhibitory activity on the whole alternative pathway, which was higher than with the physiological regulator FH.

New strategies for treatment of infectious sepsis

In this mini review, we describe the molecular mechanisms in polymicrobial sepsis that lead to a series of adverse events including activation of inflammatory and prothrombotic pathways, a faulty innate immune system, and multiorgan dysfunction. Complement activation is a well-established feature of sepsis, especially involving generation of C5a and C5b-9, along with engagement of relevant receptors for C5a. Activation of neutrophils by C5a leads to extrusion of DNA, forming neutrophil extracellular traps that contain myeloperoxidase and oxidases, along with extracellular histones. Generation of the distal complement activation product, C5b-9 (known as the membrane attack complex, MAC), also occurs in sepsis. C5b-9 activates the NLRP3 inflammasome, which damages mitochondria, together with appearance in plasma of IL-1β and IL-18. Histones are strongly proinflammatory as well as being prothrombotic, leading to activation of platelets and development of venous thrombosis. Multiorgan dysfunction is also a feature of sepsis. It is well known that septic cardiomyopathy, which if severe, can lead to death. This complication in sepsis is linked to reduced levels in cardiomyocytes of three critical proteins (SERCA2, NCX, Na⁺ /K⁺ -ATPase). The reductions in these three key proteins are complement- and histone-dependent. Dysfunction of these ATPases is linked to the cardiomyopathy of sepsis. These data suggest novel targets in the setting of sepsis in humans.

A Single-Domain Antibody Targeting Complement Component C5 Acts as a Selective Inhibitor of the Terminal Pathway of the Complement System and Thus Functionally Mimicks the C-Terminal Domain of the Staphylococcus aureus SSL7 Protein

The complement system is an efficient anti-microbial effector mechanism. On the other hand abnormal complement activation is involved in the pathogenesis of multiple inflammatory and hemolytic diseases. As general inhibition of the complement system may jeopardize patient health due to increased susceptibility to infections, the development of pathway-specific complement therapeutics has been a long-lasting goal over the last decades. In particular, pathogen mimicry has been considered as a promising approach for the design of selective anti-complement drugs. The C-terminal domain of staphylococcal superantigen-like protein 7 (SSL7), a protein secreted by Staphylococcus aureus, was recently found to be a specific inhibitor of the terminal pathway of the complement system, providing selective inhibition of cell lysis mediated by the membrane attack complex (MAC). We describe here the selection by phage display of a humanized single-domain antibody (sdAb) mimicking the C-terminal domain of SSL7. The antibody, called sdAb_E4, binds complement C5 with an affinity in the low micromolar range. Furthermore, sdAb_E4 induces selective inhibition of MAC-mediated lysis, allowing inhibition of red blood cell hemolysis and inhibition of complement deposition on apopto-necrotic cells, while maintaining efficient bactericidal activity of the complement terminal pathway. Finally, we present preliminary results indicating that sdAb_E4 may also be efficient in inhibiting hemolysis of erythrocytes from patients with paroxysmal nocturnal hemoglobinuria. Our data provide a proof of concept for the design of a selective MAC inhibitor capable of retaining complement bacteriolytic activity and this study opens up promising perspectives for the development of an sdAb_E4-derived therapeutics with application in the treatment of complement-mediated hemolytic disorders.

Systemic inhibition of the membrane attack complex impedes neuroinflammation in chronic relapsing experimental autoimmune encephalomyelitis

The complement system is a key driver of neuroinflammation. Activation of complement by all pathways, results in the formation of the anaphylatoxin C5a and the membrane attack complex (MAC). Both initiate pro-inflammatory responses which can contribute to neurological disease. In this study, we delineate the specific roles of C5a receptor signaling and MAC formation during the progression of experimental autoimmune encephalomyelitis (EAE)-mediated neuroinflammation. MAC inhibition was achieved by subcutaneous administration of an antisense oligonucleotide specifically targeting murine C6 mRNA (5 mg/kg). The C5a receptor 1 (C5aR1) was inhibited with the C5a receptor antagonist PMX205 (1.5 mg/kg). Both treatments were administered systemically and started after disease onset, at the symptomatic phase when lymphocytes are activated. We found that antisense-mediated knockdown of C6 expression outside the central nervous system prevented relapse of disease by impeding the activation of parenchymal neuroinflammatory responses, including the Nod-like receptor protein 3 (NLRP3) inflammasome. Furthermore, C6 antisense-mediated MAC inhibition protected from relapse-induced axonal and synaptic damage. In contrast, inhibition of C5aR1-mediated inflammation diminished expression of major pro-inflammatory mediators, but unlike C6 inhibition, it did not stop progression of neurological disability completely. Our study suggests that MAC is a key driver of neuroinflammation in this model, thereby MAC inhibition might be a relevant treatment for chronic neuroinflammatory diseases.

Thrombotic Microangiopathy and the Kidney

Thrombotic microangiopathy can manifest in a diverse range of diseases and is characterized by thrombocytopenia, microangiopathic hemolytic anemia, and organ injury, including AKI. It can be associated with significant morbidity and mortality, but a systematic approach to investigation and prompt initiation of supportive management and, in some cases, effective specific treatment can result in good outcomes. This review considers the classification, pathology, epidemiology, characteristics, and pathogenesis of the thrombotic microangiopathies, and outlines a pragmatic approach to diagnosis and management.

Diseases of complement dysregulation-an overview

Atypical hemolytic uremic syndrome (aHUS), C3 glomerulopathy (C3G), and paroxysmal nocturnal hemoglobinuria (PNH) are prototypical disorders of complement dysregulation. Although complement overactivation is common to all, cell surface alternative pathway dysregulation (aHUS), fluid phase alternative pathway dysregulation (C3G), or terminal pathway dysregulation (PNH) predominates resulting in the very different phenotypes seen in these diseases. The mechanism underlying the dysregulation also varies with predominant acquired autoimmune (C3G), somatic mutations (PNH), or inherited germline mutations (aHUS) predisposing to disease. Eculizumab has revolutionized the treatment of PNH and aHUS although has been less successful in C3G. With the next generation of complement therapeutic in late stage development, these archetypal complement diseases will provide the initial targets.

Myasthenia gravis: the role of complement at the neuromuscular junction

Generalized myasthenia gravis (gMG) is a rare autoimmune disorder characterized by skeletal muscle weakness caused by disrupted neurotransmission at the neuromuscular junction (NMJ). Approximately 74-88% of patients with gMG have acetylcholine receptor (AChR) autoantibodies. Complement plays an important role in innate and antibody-mediated immunity, and activation and amplification of complement results in the formation of membrane attack complexes (MACs), lipophilic proteins that damage cell membranes. The role of complement in gMG has been demonstrated in animal models and patients. Studies in animals lacking specific complement proteins have confirmed that MAC formation is required to induce experimental autoimmune MG (EAMG) and NMJ damage. Complement inhibition in EAMG models can prevent disease induction and reverse its progression. Patients with anti-AChR⁺ MG have autoantibodies and MACs present at NMJs. Damaged NMJs are associated with more severe disease, fewer AChRs, and MACs in synaptic debris. Current MG therapies do not target complement directly. Eculizumab is a humanized monoclonal antibody that inhibits cleavage of complement protein C5, preventing MAC formation. Eculizumab treatment improved symptoms compared with placebo in a phase II study in patients with refractory gMG. Direct complement inhibition could preserve NMJ physiology and muscle function in patients with anti-AChR⁺ gMG.

Complement C5-inhibiting therapy for the thrombotic microangiopathies: accumulating evidence, but not a panacea

Thrombotic microangiopathy (TMA), characterized by organ injury occurring consequent to severe endothelial damage, can manifest in a diverse range of diseases. In complement-mediated atypical haemolytic uraemic syndrome (aHUS) a primary defect in complement, such as a mutation or autoantibody leading to over activation of the alternative pathway, predisposes to the development of disease, usually following exposure to an environmental trigger. The elucidation of the pathogenesis of aHUS resulted in the successful introduction of the complement inhibitor eculizumab into clinical practice. In other TMAs, although complement activation may be seen, its role in the pathogenesis remains to be confirmed by an interventional trial. Although many case reports in TMAs other than complement-mediated aHUS hint at efficacy, publication bias, concurrent therapies and in some cases the self-limiting nature of disease make broader interpretation difficult. In this article, we will review the evidence for the role of complement inhibition in complement-mediated aHUS and other TMAs.

Atypical hemolytic uremic syndrome triggered by varicella infection

Varicella Zoster Virus (VZV) is a well-known virus that belongs to the Herpesviridae family which induces a self-limited disease except in specific cases in particular among stem cell transplant patients. This virus is not known however to trigger atypical Hemolytic Uremic Syndrome (aHUS). Here we report the case of a six-year-old boy who was hospitalized with fever and abdominal pains associated to pruritic and vesicular rash, thrombocytopenia and acute renal failure. He was diagnosed with aHUS precipitated by varicella virus. He was treated by an association of antimicrobials against potential superinfections, plasmapheresis and eculizumab for curative aHUS treatment. This was effective but after 6 months the kidney function remained poor. The current case describes an aHUS associated to varicella infection as demonstrated by the simultaneous occurrence of the viral infection and aHUS manifestations. Apart from typical Hemolytic Uremic Syndrome which is triggered by bacteria mostly Shiga toxin producing Echerichia coli and Streptococcus pneumoniae or Shigella, aHUS may be linked to viral infections such as HIV, EBV and enteroviruses, but very rarely by varicella. This case highlights a possible even rare complication of varicella infection a very common childhood disease. This complication could be avoided by to anti-VZV vaccination.

Quantification of the IgG2/4 kappa Monoclonal Therapeutic Eculizumab from Serum Using Isotype Specific Affinity Purification and Microflow LC-ESI-Q-TOF Mass Spectrometry

As therapeutic monoclonal antibodies (mAbs) become more humanized, traditional tryptic peptide approaches used to measure biologics in serum become more challenging since unique clonotypic peptides used for quantifying the mAb may also be found in the normal serum polyclonal background. An alternative approach is to monitor the unique molecular mass of the intact light chain portion of the mAbs using liquid chromatography-mass spectrometry (LC-MS). Distinguishing a therapeutic mAb from a patient's normal polyclonal immunoglobulin (Ig) repertoire is the primary limiting factor when determining the limit of quantitation (LOQ) in serum. The ability to selectively extract subclass specific Igs from serum reduces the polyclonal background in a sample. We present here the development of an LC-MS method to quantify eculizumab in serum. Eculizumab is a complement component 5 (C5) binding mAb that is fully humanized and contains portions of both IgG2 and IgG4 subclasses. Our group developed a method that uses Life Technologies CaptureSelect IgG4 (Hu) affinity matrix. We show here the ability to quantitate eculizumab with a LOQ of 5 mcg/mL by removing the higher abundance IgG1, IgG2, and IgG3 from the polyclonal background, making this approach a simple and efficient procedure. Graphical Abstract ᅟ.

Unintended Immunological Consequences of Biologic Therapy

Recent advances in the understanding of immune dysregulation in autoimmune diseases have enabled the development of new monoclonal antibody-based drugs called biologics. Biologics have been used to target aberrant immune responses in many diseases, but patients with rheumatologic and other autoimmune diseases have benefited the most and improvements in outcomes have been significant. The use of biologics is not without hazard, however, as these agents block immune pathways adapted to protect the host. This has been borne out by increased rates of infections as well as induction of new autoimmune and hematologic adverse effects. As new drugs for the treatment of autoimmune conditions are entering the pipeline, it is incumbent on the practicing immunologist to understand the mechanism of these biologics and the implications of clinical use.

Biologic response modifiers: Indications, implications, and insights

The field of biologic immune modulators is currently mushrooming at a dizzying pace. Although most of these biologics are tested and approved for one or a few indications, their unanticipated side effects and off-label use have contributed significantly to our understanding of basic immune mechanisms, the involvement of cytokines in several apparently nonimmunologic diseases, and the importance of compartmentalized immune responses. In this review we attempt to give a bird's-eye view of the major biologics and to highlight insights and implications derived from their secondary effects and adverse reactions.

Complement: A primer for the coming therapeutic revolution

The complement system is an important part of the innate and adaptive immune systems. Originally characterized as a single serum component contributing to the killing of bacteria, we now know that there are close to sixty complement proteins, multiple activation pathways and a wide range of effector functions mediated by complement. The system plays a critical role in host defense against bacteria, viruses, fungi and other pathogens. However, inappropriate complement activation contributes to the pathophysiology of autoimmune diseases and many inflammatory syndromes. Over the last several decades, therapeutic approaches to inhibit complement activation at various steps in the pathways have met with initial success, particularly at the level of the terminal pathway. This success, combined with insight from animal model studies, has lead to an unprecedented effort by biotech and pharmaceutical companies to begin developing complement inhibitors. As a result, complement has been brought for the first time to the attention of pharmacologists, toxicologists, project managers and others in the drug development industry, as well as those in the investment world. The purpose of this primer is to provide a broad overview of complement immunobiology to help those new to complement understand the rationale behind the current therapeutic directions and the investment potential of these new therapeutics.

Unraveling the Role of Allo-Antibodies and Transplant Injury

Alloimmunity driving rejection in the context of solid organ transplantation can be grossly divided into mechanisms predominantly driven by either T cell-mediated rejection (TCMR) and antibody-mediated rejection (ABMR), though the co-existence of both types of rejections can be seen in a variable number of sampled grafts. Acute TCMR can generally be well controlled by the establishment of effective immunosuppression (1, 2). Acute ABMR is a low frequency finding in the current era of blood group and HLA donor/recipient matching and the avoidance of engraftment in the context of high-titer, preformed donor-specific antibodies. However, chronic ABMR remains a major complication resulting in the untimely loss of transplanted organs (3-10). The close relationship between donor-specific antibodies and ABMR has been revealed by the highly sensitive detection of human leukocyte antigen (HLA) antibodies (7, 11-15). Injury to transplanted organs by activation of humoral immune reaction in the context of HLA identical transplants and the absence of donor specific antibodies (17-24), strongly suggest the participation of non-HLA (nHLA) antibodies in ABMR (25). In this review, we discuss the genesis of ABMR in the context of HLA and nHLA antibodies and summarize strategies for ABMR management.

Differential activation mechanisms of serum C5a in lupus nephritis and neuropsychiatric systemic lupus erythematosus

OBJECTIVE

To explore the role of C5a in the pathogenesis of neuropsychiatric systemic lupus erythematosus (NPSLE) and lupus nephritis (LN).

METHODS

Sera were obtained from 29 patients with NPSLE, 25 with LN, 26 without NPSLE or LN [SLE alone], and 21 healthy donors. Cerebrospinal fluid (CSF) was obtained from 29 NPSLE patients. C5a and C5 were measured by ELISA. Blood-brain barrier (BBB) function was evaluated by Q albumin ([CSF albumin/serum albumin] × 10³).

RESULTS

Serum C5a, but not C5, was significantly increased in SLE compared with healthy control. Serum C5a, but not C5, was significantly higher in NPSLE and in LN than in SLE alone. Serum C4, but not C3, was lower in LN than in NPSLE. Q albumin was significantly higher in diffuse NPSLE than in focal NPSLE, whereas there were no significant differences in CSF or serum C5a between both groups. Notably, CSF C5 and C5a were significantly correlated with Q albumin, whereas serum C5a, but not C5, appeared to be inversely correlated with Q albumin.

CONCLUSION

These results disclosed that serum C5a was elevated not only in NPSLE but also in LN through different mechanisms. Moreover, it is suggested that C5a might be consumed during BBB damages.

Complement in disease: a defence system turning offensive

Although the complement system is primarily perceived as a host defence system, a more versatile, yet potentially more harmful side of this innate immune pathway as an inflammatory mediator also exists. The activities that define the ability of the complement system to control microbial threats and eliminate cellular debris - such as sensing molecular danger patterns, generating immediate effectors, and extensively coordinating with other defence pathways - can quickly turn complement from a defence system to an aggressor that drives immune and inflammatory diseases. These host-offensive actions become more pronounced with age and are exacerbated by a variety of genetic factors and autoimmune responses. Complement can also be activated inappropriately, for example in response to biomaterials or transplants. A wealth of research over the past two decades has led to an increasingly finely tuned understanding of complement activation, identified tipping points between physiological and pathological behaviour, and revealed avenues for therapeutic intervention. This Review summarizes our current view of the key activating, regulatory, and effector mechanisms of the complement system, highlighting important crosstalk connections, and, with an emphasis on kidney disease and transplantation, discusses the involvement of complement in clinical conditions and promising therapeutic approaches.

[Atipical uremic hemolityc syndrome in pregnancy]

Atypical haemolytic uraemic syndrome is one of the main variants of thrombotic microangiopathy, and is characterized by excessive complement activation in the microvasculature. It is also characterised by the clinical triad; non-immune haemolytic anaemia, thrombocytopenia, and acute renal failure. In addition, 60% of patients have mutations in the genes encoding complement regulators (factor H, factor I, membrane cofactor proteins, and thrombomodulin), activators (factor B and C3), as well as autoantibodies against factor H. Multiple factors are required for the disease to manifest itself, including a trigger and gene mutations with adequate penetration. Being one of the differential diagnoses of preeclampsia- eclampsia and HELLP syndrome means that the clinician must be familiar with the disease due to its high mortality, which can be modified with early diagnosis and comprehensive treatment.

Complement Activation in Arterial and Venous Thrombosis is Mediated by Plasmin

Thrombus formation leading to vaso-occlusive events is a major cause of death, and involves complex interactions between coagulation, fibrinolytic and innate immune systems. Leukocyte recruitment is a key step, mediated partly by chemotactic complement activation factors C3a and C5a. However, mechanisms mediating C3a/C5a generation during thrombosis have not been studied. In a murine venous thrombosis model, levels of thrombin–antithrombin complexes poorly correlated with C3a and C5a, excluding a central role for thrombin in C3a/C5a production. However, clot weight strongly correlated with C5a, suggesting processes triggered during thrombosis promote C5a generation. Since thrombosis elicits fibrinolysis, we hypothesized that plasmin activates C5 during thrombosis. In vitro, the catalytic efficiency of plasmin-mediated C5a generation greatly exceeded that of thrombin or factor Xa, but was similar to the recognized complement C5 convertases. Plasmin-activated C5 yielded a functional membrane attack complex (MAC). In an arterial thrombosis model, plasminogen activator administration increased C5a levels. Overall, these findings suggest plasmin bridges thrombosis and the immune response by liberating C5a and inducing MAC assembly. These new insights may lead to the development of strategies to limit thrombus formation and/or enhance resolution.

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Thrombin is not a major direct contributor to C5a generation during venous thrombosis in mice.

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Plasmin, a protease generated in response to thrombin generation and fibrin deposition, efficiently cleaves C5 to C5a.

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In an arterial thrombosis model, administration of a plasminogen activator augments C5a plasma levels.

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Plasmin participates in immunothrombosis, liberating chemotactic C5a and inducing assembly of the procoagulant C5b-9.

Venous and arterial thrombosis are major causes of death and morbidity. Leukocytes are early and active participants in thrombus formation, recruited partly by complement factor C5a. We examined how C5a is generated in the setting of thrombosis. In venous thrombosis in mice, we show that thrombin, a key clot-promoting enzyme, is not a major contributor to C5a generation. Rather, plasmin, a fibrinolytic enzyme formed in response to thrombin generation and clot formation, efficiently generates C5a. The findings were validated in an arterial thrombosis model in mice. These insights may be valuable in developing therapeutic strategies to limit thrombus formation.

The membrane attack complex as an inflammatory trigger

The final common pathway of all routes of complement activation involves the non-enzymatic assembly of a complex comprising newly formed C5b with the plasma proteins C6, C7, C8 and C9. When assembly occurs on a target cell membrane the forming complex inserts into and through the bilayer to create a pore, the membrane attack complex (MAC). On some targets, pore formation causes rapid lytic destruction; however, most nucleated cell targets resist lysis through a combination of ion pumps, membrane regulators and active recovery processes. Cells survive but not without consequence. The MAC pore causes ion fluxes and directly or indirectly impacts several important signalling pathways that in turn activate a diverse series of events in the cell, many of which are highly pro-inflammatory. Although this non-lytic, pro-inflammatory role of MAC has been recognised for thirty years, no consensus signalling pathway has emerged. Recent work, summarised here, has implicated specific signalling routes and, in some cells, inflammasome involvement, opening the door to novel approaches to therapy in complement-driven pathologies.