Terminal complement inhibitor eculizumab in atypical hemolytic-uremic syndrome

Molecular recognition and interaction between human plasminogen Kringle 5 and A2M domain in human complement C5 by biospecific methods coupled with molecular dynamics simulation

The potent angiogenesis inhibitor known as human plasminogen Kringle 5 has shown promise in the treatment of vascular disorders and malignancies. The study aimed to investigate the recognition and interaction between Kringle 5 and the A2M domain of human complement component C5 using bio-specific methodologies and molecular dynamics (MD) simulation. Initially, the specific interaction between Kringle 5 and A2M was confirmed and characterized through Ligand Blot and ELISA, yielding the dissociation constant (Kd) of 1.70 × 10-7 mol/L. Then, Kringle 5 showcased a dose-dependent inhibition of the production of C5a in lung cancer A549 cells, consequently impeding their proliferation and migration. Following the utilization of frontal affinity chromatography (FAC), it was revealed that there exists a singular binding site with the binding constant (Ka) of 3.79 × 105 L/mol. Following the implementation of homology modeling and MD optimization, the detailed results indicate that only a specific segment of the N-terminal structure of the A2M molecule engages in interaction with Kringle 5 throughout the binding process and the principal driving forces encompass electrostatic force, hydrogen bonding, and van der Waals force. In conclusion, the A2M domain of human complement C5 emerges as a plausible binding target for Kringle 5 in vivo.

Adolescence-onset atypical hemolytic uremic syndrome: is it different from infant-onset?

BACKGROUND

Atypical hemolytic uremic syndrome (aHUS) is a rare, mostly complement-mediated thrombotic microangiopathy. The majority of patients are infants. In contrast to infantile-onset aHUS, the clinical and genetic characteristics of adolescence-onset aHUS have not been sufficiently addressed to date.

METHODS

A total of 28 patients (21 girls, 7 boys) who were diagnosed as aHUS between the ages of ≥10 years and <18 years were included in this study. All available data in the Turkish Pediatric aHUS registry were collected and analyzed.

RESULTS

The mean age at diagnosis was 12.8±2.3 years. Extra-renal involvement was noted in 13 patients (46.4%); neurological involvement was the most common (32%). A total of 21 patients (75%) required kidney replacement therapy. Five patients (17.8%) received only plasma therapy and 23 (82%) of the patients received eculizumab. Hematologic remission and renal remission were achieved in 25 (89.3%) and 17 (60.7%) of the patients, respectively. Compared with the infantile-onset aHUS patients, adolescent patients had a lower complete remission rate during the first episode (p = 0.002). Genetic analyses were performed in all and a genetic variant was detected in 39.3% of the patients. The mean follow-up duration was 4.9±2.6 years. At the last visit, adolescent patients had lower eGFR levels (p = 0.03) and higher rates of chronic kidney disease stage 5 when compared to infantile-onset aHUS patients (p = 0.04).

CONCLUSIONS

Adolescence-onset aHUS is a rare disease but tends to cause more permanent renal dysfunction than infantile-onset aHUS. These results may modify the management approaches in these patients.

Complement inhibitors in pediatric kidney diseases: new therapeutic opportunities

Historically, the complement system (classical, lectin, alternative, and terminal pathways) is known to play a crucial role in the etiopathogenesis of many kidney diseases. Direct or indirect activation in these settings is revealed by consumption of complement proteins at the serum level and kidney tissue deposition seen by immunofluorescence and electron microscopy. The advent of eculizumab has shown that complement inhibitors may improve the natural history of certain kidney diseases. Since then, the number of available therapeutic molecules and experimental studies on complement inhibition has increased exponentially. In our narrative review, we give a summary of the main complement inhibitors that have completed phase II and phase III studies or are currently used in adult and pediatric nephrology. The relevant full-text works, abstracts, and ongoing trials (clinicaltrials.gov site) are discussed. Data and key clinical features are reported for eculizumab, ravulizumab, crovalimab, avacopan, danicopan, iptacopan, pegcetacoplan, and narsoplimab. Many of these molecules have been shown to be effective in reducing proteinuria and stabilizing kidney function in different complement-mediated kidney diseases. Thanks to their efficacy and target specificity, these novel drugs may radically improve the outcome of complement-mediated kidney diseases, contributing to an improvement in our understanding of their underlying pathophysiology.

A case-based narrative review of pregnancy-associated atypical hemolytic uremic syndrome/complement-mediated thrombotic microangiopathy

Atypical hemolytic uremic syndrome is a complement-mediated thrombotic microangiopathy caused by uncontrolled activation of the alternative complement pathway in the setting of autoantibodies to or rare pathogenic genetic variants in complement proteins. Pregnancy may serve as a trigger and unmask atypical hemolytic uremic syndrome/complement-mediated thrombotic microangiopathy (aHUS/CM-TMA), which has severe, life-threatening consequences. It can be difficult to diagnose aHUS/CM-TMA in pregnancy due to overlapping clinical features with other thrombotic microangiopathy syndromes including hypertensive disorders of pregnancy. However, the distinction among thrombotic microangiopathy etiologies in pregnancy is important because each syndrome has specific disease management and treatment. In this narrative review, we discuss 2 cases to illustrate the diagnostic challenges and evolving approach in the management of pregnancy-associated aHUS/CM-TMA. The first case involves a 30-year-old woman presenting in the first trimester who was diagnosed with aHUS/CM-TMA and treated with eculizumab from 19 weeks' gestation. Genetic testing revealed a likely pathogenic variant in CFI. She successfully delivered a healthy infant at 30 weeks' gestation. In the second case, a 22-year-old woman developed severe postpartum HELLP syndrome, requiring hemodialysis. Her condition improved with supportive management, yet investigations assessing for aHUS/CM-TMA remained abnormal 6 months postpartum consistent with persistent complement activation but negative genetic testing. Through detailed case discussion describing tests assessing for placental health, fetal anatomy, complement activation, autoantibodies to complement regulatory proteins, and genetic testing for aHUS/CM-TMA, we describe how these results aided in the clinical diagnosis of pregnancy-associated aHUS/CM-TMA and assisted in guiding patient management, including the use of anticomplement therapy.

Eculizumab dose tapering should take into account the nonlinearity of its pharmacokinetics

AIMS

Eculizumab is a monoclonal antibody targeting complement protein C5 used in renal diseases. As recommended dosing regimen leads to unnecessarily high concentrations in some patients, tailored dosing therapeutic drug monitoring was proposed to reduce treatment cost. The objectives of the present work were (i) to investigate the target-mediated elimination of eculizumab and (ii) whether a pharmacokinetic model integrating a nonlinear elimination allows a better prediction of eculizumab concentrations than a linear model.

METHODS

We analysed 377 eculizumab serum concentrations from 44 patients treated for atypical haemolytic uraemic syndrome and C3 glomerulopathy with a population pharmacokinetic approach. Critical concentrations (below which a non-log-linear decline of concentration over time is evidenced) were computed to estimate the relevance of the target-mediated elimination. Simulations of dosing regimens were then performed to predict probabilities of target attainment (i.e. trough >100 mg/L).

RESULTS

Pharmacokinetics of eculizumab was nonlinear and followed a mixture of first-order (CL = 1.318 mL/day/kg) and Michaelis-Menten elimination (Vmax = 26.07 mg/day, Km = 24.06 mg/L). Volume of distribution (72.39 mL/kg) and clearance were weight-dependent. Critical concentrations (Vmax/CL) ranged from 144.7 to 759.7 mg/L and were inversely related to body weight (P = .013). Nonlinearity was thus noticeable at therapeutic concentrations. Simulations predicted that 1200 mg of eculizumab every 21 days would allow 85% and 76% of patients to maintain a therapeutic exposure, for 50 or 90 kg body weight, respectively.

CONCLUSIONS

Our study investigates the nonlinear elimination of eculizumab and discusses the importance of accounting for eculizumab target-mediated elimination in therapeutic drug monitoring.

Eculizumab in Shiga toxin-producing Escherichia coli hemolytic uremic syndrome: a systematic review

BACKGROUND

Infection-associated hemolytic uremic syndrome (IA-HUS), most often due to infection with Shiga toxin-producing bacteria, mainly affects young children. It can be acutely life-threatening, as well as cause long-term kidney and neurological morbidity. Specific treatment with proven efficacy is lacking. Since activation of the alternative complement pathway occurs in HUS, the monoclonal C5 antibody eculizumab is often used off-label once complications, e.g., seizures, occur. Eculizumab is prohibitively expensive and carries risk of infection. Its utility in IA-HUS has not been systematically studied. This systematic review aims to present, summarize, and evaluate all currently available data regarding the effect of eculizumab administration on medium- to long-term outcomes (i.e., outcomes after the acute phase, with a permanent character) in IA-HUS.

METHODS

PubMed, Embase, and Web of Science were systematically searched for studies reporting the impact of eculizumab on medium- to long-term outcomes in IA-HUS. The final search occurred on March 2, 2022. Studies providing original data regarding medium- to long-term outcomes in at least 5 patients with IA-HUS, treated with at least one dose of eculizumab during the acute illness, were included. No other restrictions were imposed regarding patient population. Studies were excluded if data overlapped substantially with other studies, or if outcomes of IA-HUS patients were not reported separately. Study quality was assessed using the ROBINS-I tool for risk of bias in non-randomized studies of interventions. Data were analyzed descriptively.

RESULTS

A total of 2944 studies were identified. Of these, 14 studies including 386 eculizumab-treated patients met inclusion criteria. All studies were observational. Shiga toxin-producing E. coli (STEC) was identified as the infectious agent in 381 of 386 patients (98.7%), effectively limiting the interpretation of the data to STEC-HUS patients. Pooling of data across studies was not possible. No study reported a statistically significant positive effect of eculizumab on any medium- to long-term outcome. Most studies were, however, subject to critical risk of bias due to confounding, as more severely ill patients received eculizumab. Three studies attempted to control for confounding through patient matching, although residual bias persisted due to matching limitations.

DISCUSSION

Current observational evidence does not permit any conclusion regarding the impact of eculizumab in IA-HUS given critical risk of bias. Results of randomized clinical trials are eagerly awaited, as new therapeutic strategies are urgently needed to prevent long-term morbidity in these severely ill patients.

SYSTEMATIC REVIEW REGISTRATION NUMBER

OSF Registries, MSZY4, Registration DOI https://doi.org/10.17605/OSF.IO/MSZY4 .

Balancing efficacy and safety of complement inhibitors

Complement inhibitors have been approved for several immune-mediated diseases and they are considered the next paradigm-shifting approach in the treatment of glomerulonephritis. The hierarchical organization of the complement system offers numerous molecular targets for therapeutic intervention. However, complement is an integral element of host defense and therefore complement inhibition can be associated with serious infectious complications. Here we give a closer look to the hierarchical complement system and how interfering with proximal versus distal or selective versus unselective molecular targets could determine efficacy and safety. Furthermore, we propose to consider the type of disease, immunological activity, and patient immunocompetence when stratifying patients, e.g., proximal/unselective targets for highly active and potentially fatal diseases while distal and selective targets may suit more chronic disease conditions with low or moderate disease activity requiring persistent complement blockade in patients with concomitant immunodeficiency. Certainly, there exists substantial promise for anti-complement therapeutics. However, balancing efficacy and safety will be key to establish powerful treatment effects with minimal adverse events, especially when complement blockade is continued over longer periods of time in chronic disorders.

How We Interpret Thrombosis with Thrombocytopenia Syndrome?

Platelets play an important role in hemostasis, and a low platelet count usually increases the risk of bleeding. Conditions in which thrombosis occurs despite low platelet counts are referred to as thrombosis with thrombocytopenia syndrome, including heparin-induced thrombocytopenia, vaccine-induced immune thrombotic thrombocytopenia, paroxysmal nocturnal hemoglobinuria, antiphospholipid syndrome, thrombotic microangiopathy (TMA), and disseminated intravascular coagulation. TMA includes thrombotic thrombocytopenic purpura, Shiga toxin-producing Escherichia coli-associated hemolytic uremic syndrome (HUS), and atypical HUS. Patients with these pathologies present with thrombosis and consumptive thrombocytopenia associated with the activation of platelets and the coagulation system. Treatment varies from disease to disease, and many diseases have direct impacts on mortality and organ prognosis if therapeutic interventions are not promptly implemented. Underlying diseases and the results of physical examinations and general laboratory tests as part of a thorough workup for patients should promptly lead to therapeutic intervention before definitive diagnosis. For some diseases, the diagnosis and initial treatment must proceed in parallel. Utilization of not only laboratory tests but also various scoring systems is important for validating therapeutic interventions based on clinical information.

Anti-CFH-associated hemolytic uremic syndrome: do we still need plasma exchange?

BACKGROUND

Between 5 and 50% of atypical hemolytic uremic syndrome (aHUS) cases in children are caused by autoantibodies against complement factor H (CFH). Given the acquired autoimmune nature of the disease, plasma exchange (PE) and various immunosuppressive treatments have been used. More recently, eculizumab has been proposed.

METHODS

In this multicenter, retrospective study, we report outcomes of 12 children with anti-FH antibody-associated HUS treated with eculizumab associated with various immunosuppressive regimens.

RESULTS

Patients were treated with eculizumab for 15.5 [9.5;23.0] months and 3 received PE or IgG adsorption. Three patients received mycophenolate mofetil (MMF) alone, 1 patient received MMF and steroids, 1 patient received MMF and rituximab, 3 patients received MMF/steroids and rituximab, and 4 patients did not receive any immunosuppression. Anti-FH antibody levels significantly decreased but no difference was observed based on the immunosuppressive regimen. Eculizumab was discontinued in 7/10 patients after 11 [7.5;15.5] months and MMF in 6/8 patients after 36 [35;40] months. Anti-FH titers at MMF discontinuation ranged from 257 to 3425 UI/L. None of these patients relapsed and eGFR at last follow-up was above 70 mL/min/1.73 m2 in all patients.

CONCLUSIONS

Eculizumab is effective and safe in inducing and maintaining remission in aHUS secondary to anti-FH antibodies and renders reduction of anti-FH titers less urgent. Anti-FH antibody titers decreased in most patients irrespective of the immunosuppressive treatment chosen, so that a strategy consisting of combining eculizumab with MMF monotherapy seems sufficient at least in non-Indian or less severe forms of anti-FH antibody-associated HUS.

Triple-fusion protein (TriFu): A potent, targeted, enzyme-like inhibitor of all three complement activation pathways

The introduction of a therapeutic anti-C5 antibody into clinical practice in 2007 inspired a surge into the development of complement-targeted therapies. This has led to the recent approval of a C3 inhibitory peptide, an antibody directed against C1s and a full pipeline of several complement inhibitors in preclinical and clinical development. However, no inhibitor is available that efficiently inhibits all three complement initiation pathways and targets host cell surface markers as well as complement opsonins. To overcome this, we engineered a novel fusion protein combining selected domains of the three natural complement regulatory proteins decay accelerating factor, factor H and complement receptor 1. Such a triple fusion complement inhibitor (TriFu) was recombinantly expressed and purified alongside multiple variants and its building blocks. We analyzed these proteins for ligand binding affinity and decay acceleration activity by surface plasmon resonance. Additionally, we tested complement inhibition in several in vitro/ex vivo assays using standard classical and alternative pathway restricted hemolysis assays next to hemolysis assays with paroxysmal nocturnal hemoglobinuria erythrocytes. A novel in vitro model of the alternative pathway disease C3 glomerulopathy was established to evaluate the potential of the inhibitors to stop C3 deposition on endothelial cells. Next to the novel engineered triple fusion variants which inactivate complement convertases in an enzyme-like fashion, stoichiometric complement inhibitors targeting C3, C5, factor B, and factor D were tested as comparators. The triple fusion approach yielded a potent complement inhibitor that efficiently inhibits all three complement initiation pathways while targeting to surface markers.

Recurrent C3 glomerulopathy after kidney transplantation

The complement system is part of innate immunity and is pivotal in protecting the body against pathogens and maintaining host homeostasis. Activation of the complement system is triggered through multiple pathways, including antibody deposition, a mannan-binding lectin, or activated complement deposition. C3 glomerulopathy (C3G) is a rare glomerular disease driven by complement dysregulation with high post-transplantation recurrence rates. Its treatment is mainly based on immunosuppressive therapies, specifically mycophenolate mofetil and glucocorticoids. Recent years have seen significant progress in understanding complement biology and its role in C3G pathophysiology. New complement-tergeting treatments have been developed and initial trials have shown promising results. However, challenges persist in C3G, with recurrent post-transplantation cases leading to suboptimal outcomes. This review discusses the pathophysiology and management of C3G, with a focus on its recurrence after kidney transplantation.

"Eculizumab First" in the Management of Posttransplant Thrombotic Microangiopathy

Introduction

Posttransplant thrombotic microangiopathy (PT-TMA) is an uncommon event that characterizes approximately 3% to 14% of kidney transplants (KTs), and that is associated with a higher risk of delayed graft function and graft loss. PT-TMA occurs more frequently within the first 3 months after transplant and can be a manifestation of de novo disease or the recurrence of previous atypical hemolytic uremic syndrome (aHUS). Abnormalities in complement regulation genes could explain the increased susceptibility of some patients to PT-TMA. Eculizumab is a humanized monoclonal antibody that inhibits the formation of the membrane attack complex C5b-9. The aim of this study is to evaluate the efficacy of eculizumab as treatment for PT-TMA.

Methods

We retrospectively analyzed clinical records of 45 KT patients who received eculizumab immediately after the clinical diagnosis of PT-TMA.

Results

Kidney biopsy was performed in 91.1% of patients, and complement genetic study was performed in 64.4%. Of the kidney biopsies, 85.4% showed signs of TMA; genetic analysis revealed 1 pathogenetic variant, 2 variants of uncertain significance, 1 likely benign variant, 8 risk polymorphisms, and 27 risk haplotypes. After 2 weeks from the treatment starting, hemoglobin and platelets significantly increased. A remarkable improvement in kidney function was also observed. After 6 months, 28.8% of patients had a complete renal recovery whereas 44.4% had a partial recovery.

Conclusion

This is, to our knowledge, the largest series of KT patients with PT-TMA treated with eculizumab. These data suggest that eculizumab is associated with a normalization of hemolysis indices and an important and progressive improvement of graft function.

Features of Postpartum Hemorrhage-Associated Thrombotic Microangiopathy and Role of Short-Term Complement Inhibition

Introduction

In pregnancy-related atypical hemolytic uremic syndrome (p-aHUS), transferring recommendations for treatment decisions from nonpregnant cohorts with thrombotic microangiopathy (TMA) is difficult. Although potential causes of p-aHUS may be unrelated to inherent complement defects, peripartal complications such as postpartum hemorrhage (PPH) or (pre)eclampsia or Hemolysis, Elevated Liver enzymes and Low Platelets (HELLP) syndrome may be unrecognized drivers of complement activation.

Methods

To evaluate diagnostic and therapeutic decisions in the practical real-life setting, we conducted an analysis of a cohort of 40 patients from 3 German academic hospitals with a diagnosis of p-aHUS, stratified by the presence (n = 25) or absence (n = 15) of PPH.

Results

Histological signs of TMA were observed in 84.2% of all patients (100% vs. 72.7% in patients without or with PPH, respectively). Patients without PPH had a higher likelihood (20% vs. 0%) of pathogenic genetic abnormalities in the complement system although notably less than in other published cohorts. Four of 5 patients with observed renal cortical necrosis (RCN) after PPH received complement inhibition and experienced partially recovered kidney function. Patients on complement inhibition with or without PPH had an increased need for kidney replacement therapy (KRT) and plasma exchange (PEX). Because renal recovery was comparable among all patients treated with complement inhibition, a potential beneficial effect in this group of pregnancy-associated TMAs and p-aHUS is presumed.

Conclusion

Based on our findings, we suggest a pragmatic approach toward limited and short-term anticomplement therapy for patients with a clinical diagnosis of p-aHUS, which should be stopped once causes of TMA other than genetic complement abnormalities emerge.

Genetic Diagnosis of Adult Hemodialysis Patients With Unknown Etiology

Introduction

Kidney disease of unknown etiology accounts for 1 in 10 adult end-stage renal disease (ESRD) cases worldwide. The aim of this study is to clarify the genetic background of patients with chronic kidney disease (CKD) of unknown etiology who initiated renal replacement therapy (RRT) in adulthood.

Methods

This is a multicenter cross-sectional cohort study. Of the 1164 patients who attended 4 dialysis clinics in Japan, we first selected patients who started RRT between the ages of 20 and 49 years. After excluding patients with apparent causes of CKD (e.g., diabetic nephropathy, polycystic kidney disease (PKD) with family history, patients who underwent renal biopsy), 90 patients with CKD of unknown cause were included. The 298 genes associated with CKD were analyzed using capture-based targeted next-generation sequencing.

Results

Of the 90 patients, 10 (11.1%) had pathogenic variants in CKD-causing genes and 17 (18.9%) had variant of unknown significance (VUS). Three patients had PKD1 pathogenic variants, and 1 patient had PKD1 and COL4A4 pathogenic variants. In addition, 2 patients were diagnosed with atypical hemolytic uremic syndrome (aHUS) due to C3 or CFHR5. One patient each was diagnosed with Alport syndrome due to COL4A4 and COL4A3 variants, nephronophthisis due to NPHP1 variants, Fabry disease due to GLA variants, and autosomal-dominant tubulointerstitial kidney disease due to UMOD variants. Genetic diagnoses were not concordant with clinical diagnoses, except for patients with PKD1 variant.

Conclusion

This largest study on genetic analysis in hemodialysis-dependent adults revealed the presence of undiagnosed inherited kidney diseases.

Systemic lupus erythematosus presenting with atypical hemolytic uremic syndrome: a case report and review of the literature

Systemic lupus erythematosus (SLE) can present with a diverse array of hematologic manifestations, among which atypical hemolytic uremic syndrome (aHUS) is a rare entity. SLE-triggered aHUS has significant morbidity and mortality without timely intervention, yet its frequency remains uncertain and optimal strategies for complement-directed therapies are largely expert-driven. We performed a comprehensive literature review and present a case of a 23-year-old female newly diagnosed with SLE/class IV lupus nephritis who developed aHUS that rapidly responded to the C5 antagonist, eculizumab. Review of the current literature identified forty-nine published cases of SLE with concurrent aHUS and revealed a predilection for aHUS in younger SLE patients, concurrent presentation with lupus nephritis, anti-dsDNA positivity, and complement system abnormalities. Over seventy percent of cases used eculizumab as complement-directed therapy with a trend towards faster time to improvement in laboratory parameters, though reported outcomes were highly variable. Early recognition of aHUS in SLE is pivotal in guiding appropriate therapeutic interventions, and prompt initiation of eculizumab may reduce the potential morbidity associated with plasmapheresis and additional immunosuppression. While eculizumab showcases promising results, its optimal timing and duration remain elusive. An understanding of a patients' complement genetics could aid management strategies, and ongoing research into complement-targeted therapies offers promising avenues for both SLE and aHUS treatment.

Complement-mediated thrombotic microangiopathy treated with anticomplement protein 5 therapy, a retrospective study

BACKGROUND

Complement-mediated thrombotic microangiopathy (CM-TMA), also called atypical hemolytic uremic syndrome (aHUS), is a difficult-to-diagnose rare disease that carries severe morbidity and mortality. Anti-C5 monoclonal antibodies (aC5-mab) are standard treatments, but large studies and long-term data are scarce. Here, we report our single institution experience to augment the knowledge of CM-TMA treated with aC5-mab therapy.

METHODS

We aimed to assess the short and long-term effects of aC5-mab in patients diagnosed with CM-TMA treated outside of a clinical trial. This was a retrospective study. We included all patients diagnosed with CM-TMA and treated with aC5-mab at our institution. There were no exclusion criteria. Endpoints included complete TMA response (CR) defined as normalization of hematological parameters and ≥25% improvement in serum creatinine (Cr) from baseline in patients with renal disease, relapse defined as losing the previously achieved CR, morbidity, adverse events, and survival.

RESULTS

We found 28 patients with CM-TMA treated with aC5-mab. The median age was 50 years. Baseline laboratories: platelet counts 93 × 109 /L, hemoglobin 8.6 g/dL, lactate dehydrogenase 1326 U/L, serum Cr 4.7 mg/dL, and estimated glomerular filtration rate 19 mL/min. One individual was on renal replacement therapy (RRT) and 10 initiated RRT within 5 days of the first dose of aC5-mab. Genetic variants associated with CM-TMA included mutations in C3, CFB, CFH, CFHR1/3, CFI, and MCP. The mean duration of hospitalization was 24 days. The median time to initiation of aC5-mab was 10 days. Sixteen subjects received RRT. At the time of hospital discharge, 27 were alive, 14 remained on RRT, and 4 had a CR. At 6 months, 23 patients were alive, 18 continued aC5-mab, 8 remained on RRT, and 9 had a CR. At the last follow-up visit past 6 months, 20 were alive, 14 continued aC5-mab, 5 remained on RRT, 12 had a CR, and 1 was lost to follow-up.

CONCLUSIONS

Our study provides real-world experience and insight into the long-term outcomes of CM-TMA treated with aC5-mab. Our findings validate that CM-TMA is an aggressive disease with significant morbidity and mortality, and confirm that aC5-mab is a relatively effective therapy for CM-TMA. Our study adds practical, real-world experience to the literature, but future research remains imperative.

Thrombotic microangiopathy - the importance of a multidisciplinary approach

PURPOSE OF REVIEW

The purpose of this review is to highlight the importance of a multidisciplinary thrombotic microangiopathies (TMA) Team. This goal will be accomplished through review of the complement system, discuss various causes of thrombotic microangiopathies (TMA), and aspects of their diagnosis and management. In so doing, readers will gain an appreciation for the complexity of this family of disorders and realize the benefit of a dedicated multidisciplinary TMA Team.

RECENT FINDINGS

TMA causes derive from multiple specialty areas, are difficult to timely recognize, pose complex challenges, and require multidisciplinary management. Hematopoietic stem cell transplant-associated TMA (TA-TMA) and TA-TMA related multiorgan dysfunction syndrome (TA-TMA MODS) are areas of burgeoning research; use of complement testing and eculizumab precision-dosing has been found to better suppress complement activity in TA-TMA than standard eculizumab dosing. Newer tests are available to risk-stratify obstetric patients at risk for severe pre-eclampsia, whose features resemble those of TA-TMA MODS. Numerous disorders may produce TMA-like findings, and a systematic approach aids in their identification. TMA Teams elevate institutional awareness of increasingly recognized TMAs, will help expedite diagnostic and therapeutic interventions, and create pathways to future TMA-related research and facilitate access to clinical trials.

SUMMARY

Establishment of a TMA-Team is valuable in developing the necessary institutional expertise needed to promptly recognize and appropriately manage patients with TMA.

Complement Activation in Nephrotic Glomerular Diseases

The nephrotic syndrome holds significant clinical importance and is characterized by a substantial protein loss in the urine. Damage to the glomerular basement membrane or podocytes frequently underlies renal protein loss. There is an increasing belief in the involvement of the complement system, a part of the innate immune system, in these conditions. Understanding the interactions between the complement system and glomerular structures continually evolves, challenging the traditional view of the blood-urine barrier as a passive filter. Clinical studies suggest that a precise inhibition of the complement system at various points may soon become feasible. However, a thorough understanding of current knowledge is imperative for planning future therapies in nephrotic glomerular diseases such as membranous glomerulopathy, membranoproliferative glomerulonephritis, lupus nephritis, focal segmental glomerulosclerosis, and minimal change disease. This review provides an overview of the complement system, its interactions with glomerular structures, and insights into specific glomerular diseases exhibiting a nephrotic course. Additionally, we explore new diagnostic tools and future therapeutic approaches.

HELLP Syndrome and Differential Diagnosis with Other Thrombotic Microangiopathies in Pregnancy

Thrombotic microangiopathies (TMAs) comprise a distinct group of diseases with different manifestations that can occur in both pediatric and adult patients. They can be hereditary or acquired, with subtle onset or a rapidly progressive course, and they are particularly known for their morbidity and mortality. Pregnancy is a high-risk time for the development of several types of thrombotic microangiopathies. The three major syndromes are hemolysis, elevated liver function tests, and low platelets (HELLP); hemolytic uremic syndrome (HUS); and thrombotic thrombocytopenic purpura (TTP). Because of their rarity, clinical information and therapeutic results related to these conditions are often obtained from case reports, small series, registries, and reviews. The collection of individual observations, the evolution of diagnostic laboratories that have identified autoimmune and/or genetic abnormalities using von Willebrand factor post-secretion processing or genetic-functional alterations in the regulation of alternative complement pathways in some of these TMAs, and, most importantly, the introduction of advanced treatments, have enabled the preservation of affected organs and improved survival rates. Although TMAs may show different etiopathogenesis routes, they all show the presence of pathological lesions, which are characterized by endothelial damage and the formation of thrombi rich in platelets at the microvascular level, as a common denominator, and thrombotic damage to microcirculation pathways induces "mechanical" (microangiopathic) hemolytic anemia, the consumption of platelets, and ischemic organ damage. In this review, we highlight the current knowledge about the diagnosis and management of these complications during pregnancy.

Targeted therapy in glomerular diseases

Targeted therapy has emerged as a more precise approach to treat glomerular diseases, focusing on specific molecular or cellular processes that contribute to disease development or progression. This approach complements or replaces traditional immunosuppressive therapy, optimizes supportive care, and provides a more personalized treatment strategy. In this review, we summarize the evolving understanding of pathogenic mechanisms in immune-mediated glomerular diseases and the developing targeted therapies based on these mechanisms. We begin by discussing pan-B-cell depletion, anti-CD20 rituximab, and targeting B-cell survival signaling through the BAFF/APRIL pathway. We also exam specific plasma cell depletion with anti-CD38 antibody. We then shift our focus to complement activation in glomerular diseases, which is involved in antibody-mediated glomerular diseases, such as IgA nephropathy, membranous nephropathy, ANCA-associated vasculitis, and lupus nephritis. Non-antibody-mediated complement activation occurs in glomerular diseases, including C3 glomerulopathy, complement-mediated atypical hemolytic uremic syndrome, and focal segmental glomerulosclerosis. We discuss specific inhibition of terminal, lectin, and alternative pathways in different glomerular diseases. Finally, we summarize current clinical trials targeting the final pathways of various glomerular diseases, including kidney fibrosis. We conclude that targeted therapy based on individualized pathogenesis should be the future of treating glomerular diseases.

Constipation and hemolytic uremic syndrome

BACKGROUND

Shiga toxin-producing Escherichia coli (STEC) hemolytic uremic syndrome (HUS) classically presents with diarrhea. Absence of diarrheal prodrome increases suspicion for atypical HUS (aHUS). Inability to obtain a fecal specimen for culture or culture-independent testing limits the ability to differentiate STEC-HUS and aHUS.

CASE-DIAGNOSIS/TREATMENT

Our patient presented with abdominal pain and constipation, and evaluation of pallor led to a diagnosis of HUS. There was a complete absence of diarrhea during the disease course. Lack of fecal specimen for several days delayed testing for STEC. Treatment for atypical HUS was initiated with complement-blockade therapy. PCR-testing for Shiga toxin from fecal specimen later returned positive. Alternative complement-pathway testing did not identify a causative genetic variant or anti-Factor H antibody. A diagnosis of STEC-HUS was assigned, and complement-blockade therapy was stopped.

CONCLUSION

Diagnosis of aHUS remains a diagnosis of exclusion, whereby other causes of HUS are eliminated with reasonable certainty. Exclusion of STEC is necessary and relies on testing availability and recognition of testing limitations. Diarrhea-negative STEC-HUS remains a minority of cases, and future research is needed to explore the clinical characteristics of these patients.

Myasthenia gravis: the changing treatment landscape in the era of molecular therapies

Myasthenia gravis (MG) is an autoimmune disorder that affects the neuromuscular junction, leading to muscle weakness and fatigue. MG is caused by antibodies against the acetylcholine receptor (AChR), the muscle-specific kinase (MuSK) or other AChR-related proteins that are expressed in the postsynaptic muscle membrane. The standard therapeutic approach for MG has relied on acetylcholinesterase inhibitors, corticosteroids and immunosuppressants, which have shown good efficacy in improving MG-related symptoms in most people with the disease; however, these therapies can carry a considerable burden of long-term adverse effects. Moreover, up to 15% of individuals with MG exhibit limited or no response to these standard therapies. The emergence of molecular therapies, including monoclonal antibodies, B cell-depleting agents and chimeric antigen receptor T cell-based therapies, has the potential to revolutionize the MG treatment landscape. This Review provides a comprehensive overview of the progress achieved in molecular therapies for MG associated with AChR antibodies and MuSK antibodies, elucidating both the challenges and the opportunities these therapies present to the field. The latest developments in MG treatment are described, exploring the potential for personalized medicine approaches.

The Efficacy and Safety of Different Targeted Drugs for the Treatment of Generalized Myasthenia Gravis: A Systematic Review and Bayesian Network Meta-analysis

BACKGROUND

The treatment of generalized myasthenia gravis (gMG) has been transformed by the development and approval of new targeted therapies. This analysis aimed to rank and compare the new therapies for gMG using efficacy and safety data from randomized controlled trials (RCTs).

METHODS

We searched PubMed, Embase, the Cochrane Central Register of Controlled Trials (CENTRAL), and ClinicalTrials.gov (up to November 2022) for RCTs of targeted drugs for gMG. We used a Bayesian random-effects network meta-analysis (NMA) model and a Markov chain Monte Carlo (MCMC) model for statistical analysis. The primary outcome was the change in quantitative myasthenia gravis score (QMGS) from baseline, while the secondary outcome was the risk ratio (RR) of adverse events (AEs) during treatment. The surface under the cumulative ranking curve (SUCRA) was used to rank these targeted drugs, with higher SUCRA values indicating better efficacy or lower likelihood of AEs.

RESULTS

In total, 13 studies (872 subjects) were included in this analysis evaluating 10 targeted drugs (batoclimab, belimumab, CFZ533, eculizumab, efgartigimod, nipocalimab, rituximab, ravulizumab, rozanolixizumab, and zilucoplan). With regards to the primary outcome, batoclimab [standardized mean difference (SMD), - 1.61; 95% credible interval (CrI), - 2.78, - 0.43] significantly reduced QMGS in patients with gMG when compared with placebo and was ranked as the most efficacious drug. Ranked second and third were eculizumab (SMD, - 0.67; 95% CrI, 1.43, 0.01) and zilucoplan (SMD, - 0.54; 95% CrI, - 1.56, 0.46), respectively. Nipoclimab (SMD, - 0.02; 95% CrI, - 1.04, 1.00) had the worst efficacy and ranked last among all targeted drugs. In our study, except for batoclimab, there was no statistically significant difference in the reduction of patient QMGS for the remaining targeted agents compared with placebo. With regards to the secondary outcomes, only batoclimab (RR, 0.19; 95% CrI, 0, 0.97) led to a significant reduction in the incidence of AEs when compared with the placebo. Belimumab (RR, 0.85; 95% CrI, 0.57, 1.19), CFZ533 (RR, 0.95; 95% CrI, 0.72, 1.25), eculizumab (RR, 0.99; 95% CrI, 0.85, 1.21), and efgartigimod (RR, 0.93; 95% CrI, 0.76, 1.15) also led to a lower incidence of AEs, although these effects were not significantly different from the placebo.

CONCLUSIONS

Batoclimab had the best efficacy and safety for the treatment of gMG and was ranked first out of the 10 targeted drugs included in this study. Eculizumab was ranked second, and nipocalimab had the worst efficacy. With the exception of batoclimab, the incidence of AEs for the remaining drugs was not statistically significantly different from placebo. We note, however, that wide CrIs reflect the uncertainty in this analysis owing to the small number of available studies and low numbers of study participants; moreover, batoclimab had the widest CrI of all drugs in this analysis. More well-designed studies with long-term follow-up are needed to further evaluate and compare the efficacy and safety of these drugs in the future.

Clinical Evaluation and Management of Thrombotic Microangiopathy

Thrombotic microangiopathy (TMA) refers to a diverse group of diseases that share clinical and histopathologic features. TMA is clinically characterized by microangiopathic hemolytic anemia, consumptive thrombocytopenia, and organ injury that stems from endothelial damage and vascular occlusion. There are several disease states with distinct pathophysiological mechanisms that manifest as TMA. These conditions are associated with significant morbidity and mortality and require urgent recognition and treatment. Thrombotic thrombocytopenic purpura and hemolytic uremic syndrome are traditionally considered to be primary forms of TMA, but TMA more commonly occurs in association with a coexisting condition such as infection, pregnancy, autoimmune disease, or malignant hypertension, among others. Determining the cause of TMA is a diagnostic challenge because of limited availability of disease-specific testing. However, identifying the underlying etiology is imperative as treatment strategies differ. Our understanding of the conditions that cause TMA is evolving. Recent advances have led to improved comprehension of the varying pathogenic mechanisms that drive TMA. Development of targeted therapeutics has resulted in significant improvements in patient outcomes. In this article, we review the pathogenesis and clinical features of the different TMA-causing conditions. We outline a practical approach to diagnosis and management and discuss empiric and disease-specific treatment strategies.

Pregnancy-Associated Atypical Hemolytic Uremic Syndrome Successfully Treated with Ravulizumab: A Case Report

Pregnancy-associated atypical hemolytic-uremic syndrome (p-aHUS) refers to a pregnancy that leads to thrombotic microangiopathy (TMA). This disease is associated with adverse maternal outcomes. We encountered a case of p-aHUS, in which treatment with ravulizumab, a long-acting C5 inhibitor, resulted in a favorable clinical course and recovery of renal function. The patient was a 31-year-old woman with no apparent medical history. She developed TMA on the third postpartum day and was initially treated with steroids, plasma exchange, and hemodialysis (HD). On the seventh day of treatment initiation, she was diagnosed with p-aHUS, and treatment with ravulizumab was started. Following administration, her platelet count increased, and her acute kidney injury improved. Consequently, HD was discontinued after six sessions, and the patient was discharged on the 28th day of treatment initiation and continued her recovery at home. Similar to eculizumab, ravulizumab is an effective treatment for p-aHUS. Early administration of ravulizumab after diagnosis of p-aHUS may contribute to favorable clinical outcomes and recovery of renal function, as observed in the present case.

Therapeutic apheresis in renal transplantation: An update

Therapeutic apheresis (TA) plays a significant role in various aspects of renal transplantation. It has been a necessary preconditioning component in ABO incompatible kidney transplants and an important modality in the removal of anti-human leukocyte antigen (HLA) antibodies both in the context of desensitization protocols that have been developed to allow highly sensitized kidney transplant candidates to be successfully transplanted and as treatment of antibody mediated rejection episodes post transplantation. In addition, TA has been used with various results for the management of recurrent focal segmental glomerulosclerosis. The purpose of this review is to examine the evidence supporting the application of TA as an adjunctive therapeutic option to immunosuppressive agents in protocols both before and after kidney transplantation.

Expansion of Anticomplement Therapy Indications from Rare Genetic Disorders to Common Kidney Diseases

Complement constitutes a major part of the innate immune system. The study of complement in human health has historically focused on infection risks associated with complement protein deficiencies; however, recent interest in the field has focused on overactivation of complement as a cause of immune injury and the development of anticomplement therapies to treat human diseases. The kidneys are particularly sensitive to complement injury, and anticomplement therapies for several kidney diseases have been investigated. Overactivation of complement can result from loss-of-function mutations in complement regulators; gain-of-function mutations in key complement proteins such as C3 and factor B; or autoantibody production, infection, or tissue stresses, such as ischemia and reperfusion, that perturb the balance of complement activation and regulation. Here, we provide a high-level review of the status of anticomplement therapies, with an emphasis on the transition from rare diseases to more common kidney diseases.

Complement in human disease: approved and up-and-coming therapeutics

The complement system is recognised as a protector against blood-borne pathogens and a controller of immune system and tissue homoeostasis. However, dysregulated complement activity is associated with unwanted or non-resolving immune responses and inflammation, which induce or exacerbate the pathogenesis of a broad range of inflammatory and autoimmune diseases. Although the merit of targeting complement clinically has long been acknowledged, the overall complement drug approval rate has been modest. However, the success of the humanised anti-C5 antibody eculizumab in effectively treating paroxysmal nocturnal haemoglobinuria and atypical haemolytic syndrome has revitalised efforts to target complement therapeutically. Increased understanding of complement biology has led to the identification of novel targets for drug development that, in combination with advances in drug discovery and development technologies, has resulted in a surge of interest in bringing new complement therapeutics into clinical use. The rising number of approved drugs still almost exclusively target rare diseases, but the substantial pipeline of up-and-coming treatment options will possibly provide opportunities to also expand the clinical targeting of complement to common diseases.

Outcome of atypical hemolytic uremic syndrome: role of triggers and complement abnormalities in the response to C5 inhibition

BACKGROUND

Atypical-hemolytic uremic syndrome (aHUS) is a rare thrombotic microangiopathy often due to uncontrolled complement activation, characterized by high risk of end-stage kidney disease (ESKD). Eculizumab has improved the outcome, however, its efficacy varies among patients and its discontinuation is debated.

METHODS

To identify characteristics associated with treatment response, we analyzed 244 aHUS patients referred to our center. Patients were classified according to the presence/absence of complement abnormalities and/or triggers at onset in 4 categories: (1) primary (complement abnormality without trigger), (2) secondary (trigger without complement abnormality), (3) combined (trigger and complement abnormality), (4) idiopathic (no trigger, no complement abnormality). Response to treatment was evaluated by comparing the response to eculizumab with that of conventional therapy. Short- and long-term outcomes were evaluated with the relapse rate after discontinuation of C5-inhibition.

RESULTS

Patients had a better outcome with eculizumab compared to conventional treatment, with a response rate of 81.9% vs 56.9%, p < 0.001 and a long-term cumulative incidence of ESKD of 5.8% vs 22.5% (hazard ratio 0.25, 95% confidence interval: 0.10-0.80). The excellent global response was driven by the primary and combined groups (89.8% vs 54.0% and 89.3% vs 54.2%, respectively). The relapse rate following discontinuation of the C5-inhibitor was as high as 66.7% in the primary group, 18.7% in the combined, and 0% in the secondary and idiopathic groups.

CONCLUSIONS

Our data show a better outcome in aHUS patients treated with C5-inhibition, particularly in the primary and combined forms, which have a high risk of relapse after discontinuation that is not observed in the secondary and idiopathic forms.

Rational use of eculizumab in secondary atypical hemolytic uremic syndrome

Background

Secondary atypical hemolytic uremic syndrome (secondary aHUS) is a heterogeneous group of thrombotic microangiopathies (TMA) associated with various underlying conditions. Unlike primary aHUS, there is still no hard evidence on the efficacy of complement blockade in secondary aHUS, since the two main series that investigated this subject showed discrepant results. Our work aims to reassess the efficacy of eculizumab in treating secondary aHUS.

Methods

Observational, retrospective, single-center study, in which we analyzed the hematological and renal evolution of 23 patients diagnosed with secondary aHUS who received treatment with eculizumab and compared them with a control cohort of 14 patients. Complete renal response was defined as the recovery of renal function before the event, partial renal response as a recovery of 50% of lost glomerular filtration rate, and hematological response as normalization of hemoglobin and platelets.

Results

We found no statistically significant differences in baseline characteristics or disease severity between both groups. After a median of 5 doses of eculizumab, the group of patients who received complement blockade presented a significant difference in renal response (complete in 52.3% of patients and partial in 23.8%) compared to the control cohort (complete response 14.3% and partial of 14.3%). Rates of hematological remission were similar in both groups (90.9% in the eculizumab cohort and 85.7% in the control cohort).

Conclusion

Early and short-term use of eculizumab in patients with secondary aHUS could be an effective and safe therapeutic option, assuring better renal recovery compared to patients who do not receive complement blockade.

Efficacy and Safety of Eculizumab in Enteroaggregative E. coli Associated Hemolytic Uremic Syndrome

BACKGROUND

Hemolytic uremic syndrome (HUS) may present atypically without the full triad of classical HUS. Eculizumab has been shown to be efficacious in complement-mediated atypical HUS and some cases of Shiga-toxin (ST) associated HUS. We report the utility of eculizumab in enteroaggregative E. coli (EAEC) associated HUS.

CASE SUMMARY

A female toddler presented with hemolytic anemia, oliguric acute kidney injury (AKI) without thrombocytopenia, and peripheral schistocytes. The stool examination for ST was negative but positive for EAEC. She required several hemodialysis sessions and received one dosage of eculizumab with rapid reversal of AKI and hemolytic markers. A kidney biopsy revealed acute tubular injury and segmental glomerular basement membrane splitting. Genetic testing was negative for complement mutations or deficiencies. A follow-up six months later showed persistently normal renal function and hematological markers.

CONCLUSION

The clinical and histological manifestations of non-ST-associated diarrheal HUS and the role of eculizumab in this condition warrant future larger studies.

[Translated article] Pharmacokinetics of eculizumab in adult and pediatric patients with atypical hemolytic uremic syndrome and C3 glomerulopathy

OBJECTIVE

The objective of the study was to analyze and describe the concentrations of eculizumab and the complement blockade in patients with atypical hemolytic uremic syndrome (aHUS) and C3 glomerulopathy, and to define a therapeutic margin where there is a high probability of achieving therapeutic efficacy.

METHODS

Observational, ambispective, and multicenter study that included adult and pediatric patients diagnosed with aHUS and C3 glomerulopathy from September 2020 to October 2022 in 5 hospitals in Spain. Eculizumab was administered at the doses recommended by the data sheet according to the European Medicines Agency (EMA). Pre- and post-dose concentrations of eculizumab were determined, as well as blockade of the classical complement pathway (CH50). Sociodemographic and clinical data were collected, and pharmacokinetic parameters were calculated. To establish the cut-off point for eculizumab concentrations that predicted complement blockade, Receiver Operating Characteristic (ROC) curve analysis was performed. Lastly, the Kruskal-Wallis test was used to contrast the differences in different parameters according to eculizumab concentrations.

RESULTS

Twenty-five patients were included, 19 adults (76.0%) and 6 pediatrics (24.0%), with median ages of 43.4 (interquartile range (IQR) 35.7-48.8) and 10.1 (IQR 9.6-11.3) years, respectively. Of these, 22 (88.0%) patients were diagnosed with aHUS and 3 (12.0%) with C3 glomerulopathy. A total of 111 eculizumab concentrations were determined. Mean pre- and post-dose concentration values detected during the maintenance phase were 243.8 (SD 240.6) μg/mL and 747.4 (standard deviation (SD) 444.3) μg/mL, respectively. Increased complement blockade was observed at higher pre-dose concentrations (P = .002) and decreased serum creatinine at both higher pre- and post-dose concentrations (P = .001 and P = .017, respectively). Using ROC curves, it was determined that a pre-dose concentration >149.0 μg/mL was optimal to achieve complement blockade, with an AUC of 0.87 (0.78-0.95). Finally, high inter-individual (48.9% variation coefficient (CV)) with low intra-individual variabilities (11.9% CV) in eculizumab clearance were observed.

CONCLUSIONS

The present study reports supratherapeutic concentrations of eculizumab in patients with aHUS, and defines higher concentrations than those described in the data sheet to achieve blockade, thus encouraging the personalization of treatment with eculizumab.

Pharmacokinetics of eculizumab in adult and pediatric patients with atypical hemolytic uremic syndrome and C3 glomerulopathy

OBJECTIVE

The objective of the study was to analyze and describe the concentrations of eculizumab and the complement blockade in patients with atypical hemolytic uremic syndrome (aHUS) and C3 glomerulopathy, and to define a therapeutic margin where there is a high probability of achieving therapeutic efficacy.

METHODS

Observational, ambispective and multicenter study that included adult and pediatric patients diagnosed with aHUS and C3 glomerulopathy from September 2020 to October 2022 in five hospitals in Spain. Eculizumab was administered at the doses recommended by the data sheet according to the European Medicines Agency (EMA). Pre-dose and post-dose concentrations of eculizumab were determined, as well as blockade of the classical complement pathway (CH50). Sociodemographic and clinical data were collected, and pharmacokinetic parameters were calculated. To establish the cut-off point for eculizumab concentrations that predicted complement blockade, Receiver Operating Characteristic (ROC) curve analysis was performed. Lastly, the Kruskal-Wallis test was used to contrast the differences in different parameters according to eculizumab concentrations.

RESULTS

Twenty-five patients were included, 19 adults (76.0%) and 6 pediatrics (24.0%), with median ages of 43.4 (IQR 35.7-48.8) and 10.1 (IQR 9.6-11.3) years, respectively. Of these, 22 (88.0%) patients were diagnosed with aHUS and 3 (12.0%) with C3 glomerulopathy. A total of 111 eculizumab concentrations were determined. Mean pre-dose and post-dose concentration values detected during the maintenance phase were 243.8 (SD 240.6) μg/mL and 747.4 (SD 444.3) μg/mL, respectively. Increased complement blockade was observed at higher pre-dose concentrations (p=0.002) and decreased serum creatinine at both higher pre- and post-dose concentrations (p=0.001 and p=0.017, respectively). Using ROC curves, it was determined that a pre-dose concentration >149.0 μg/mL was optimal to achieve complement blockade, with an AUC of 0.87 (0.78-0.95). Finally, high inter-individual (48.9% CV) with low intra-individual variabilities (11.9% CV) in eculizumab clearance were observed.

CONCLUSIONS

The present study reports supratherapeutic concentrations of eculizumab in patients with aHUS, and defines higher concentrations than those described in the data sheet to achieve blockade, thus encouraging the personalization of treatment with eculizumab.

Atypical hemolytic uremic syndrome in a child: A rare case report

Atypical hemolytic uremic syndrome, a rare thrombotic microangiopathy, necessitates early diagnosis and comprehensive care due to its potential severity, emphasizing the importance of a multidisciplinary approach to improve outcomes.

Complements and Their Role in Systemic Disorders

The complement system is critical to the body's innate defense against exogenous pathogens and clearance of endogenous waste, comprising the classical, alternative, and lectin pathways. Although tightly regulated, various congenital and acquired diseases can perturb the complement system, resulting in specific complement deficiencies. Systemic rheumatic, neurological, ophthalmological, renal, and hematological disorders are some prototypical complement-mediated diseases. An adequate understanding of the mechanisms of the normal complement system and the pathophysiology of complement dysregulation is critical for providing diagnostic clues and appropriately managing these conditions. This review guides clinicians in understanding the role of complement factors in systemic diseases and what diagnostic and therapeutic options are available for complement-mediated disorders.

Characterization of the bispecific VHH antibody gefurulimab (ALXN1720) targeting complement component 5, and designed for low volume subcutaneous administration

The bispecific antibody gefurulimab (also known as ALXN1720) was developed to provide patients with a subcutaneous treatment option for chronic disorders involving activation of the terminal complement pathway. Gefurulimab blocks the enzymatic cleavage of complement component 5 (C5) into the biologically active C5a and C5b fragments, which triggers activation of the terminal complement cascade. Heavy-chain variable region antigen-binding fragment (VHH) antibodies targeting C5 and human serum albumin (HSA) were isolated from llama immune-based libraries and humanized. Gefurulimab comprises an N-terminal albumin-binding VHH connected to a C-terminal C5-binding VHH via a flexible linker. The purified bispecific VHH antibody has the expected exact size by mass spectrometry and can be formulated at greater than 100 mg/mL. Gefurulimab binds tightly to human C5 and HSA with dissociation rate constants at pH 7.4 of 54 pM and 0.9 nM, respectively, and cross-reacts with C5 and serum albumin from cynomolgus monkeys. Gefurulimab can associate with C5 and albumin simultaneously, and potently inhibits the terminal complement activity from human serum initiated by any of the three complement pathways in Wieslab assays. Electron microscopy and X-ray crystallography revealed that the isolated C5-binding VHH recognizes the macroglobulin (MG) 4 and MG5 domains of the antigen and thereby is suggested to sterically prevent C5 binding to its activating convertase. Gefurulimab also inhibits complement activity supported by the rare C5 allelic variant featuring an R885H substitution in the MG7 domain. Taken together, these data suggest that gefurulimab may be a promising candidate for the potential treatment of complement-mediated disorders.

Medical consult: aHUS, TTP? How to distinguish and what to do

Immune thrombotic thrombocytopenic purpura (iTTP) caused by an autoantibody-mediated deficiency of ADAMTS13 and atypical hemolytic syndrome (aHUS) caused by alternative complement dysregulation are the most common primary thrombotic microangiopathies (TMAs). The evaluation of a patient with TMA is a medical emergency since it is critical to quickly distinguish iTTP and aHUS from other causes of TMA. Untreated iTTP is rapidly fatal, and delays in initiating complement inhibition in aHUS increase the risk of irreversible renal failure. An ADAMTS13 activity level of less than 10% is diagnostic of iTTP in the appropriate clinical setting. In settings where rapid-turnaround ADAMTS13 testing is not available, clinical features and clinical prediction tools are useful to identify patients who should receive emergent plasma exchange. We present an evidence-based approach to the initial (first 24 hours) diagnosis and management of iTTP and review the clinical and laboratory features that can be used to identify patients with aHUS who will benefit from early C5 blockade. We also discuss the potential use of complement blockade to improve outcomes in selected patients with secondary TMA.

New findings in preventing recurrence and improving renal function in AHUS patients after renal transplantation treated with eculizumab: a systemic review and meta-analyses

BACKGROUND

The long-term mortality of kidney transplantation patients with atypical hemolytic uremic syndrome remains high, and the efficacy of the main treatment eculizumab is still controversial.

OBJECTIVE

A comprehensive systematic review and meta-analysis of clinical trials using eculizumab in renal transplant patients with atypical hemolytic uremic syndrome was conducted to evaluate the efficacy of this therapy and its impact on renal function.

METHODS

A comprehensive systematic search was conducted across multiple reputable databases, including Ovid (MEDLINE, EMBASE), PubMed, and the Cochrane Library (since database inception), to identify relevant studies exploring the use of eculizumab in patients with atypical hemolytic uremic kidney transplantation. Various renal function parameters, such as dialysis, rejection, glomerular filtration rate, serum creatinine, lactate dehydrogenase, and platelet count, along with patient relapse rates, were extracted and summarized using a combination of robust statistical methods, including fixed effects, random effects, and general inverse variance methods.

RESULT

Eighteen trials with 618 subjects were analyzed. Our analysis suggests that the use of eculizumab is associated with a reduced likelihood of AHUS recurrence (odds ratio (OR) = 0.05, 95% CI: 0.00-0.13), as well as a significant reduction in the need for dialysis (odds ratio (OR) = 0.13, 95% CI: 0.01-0.32). Additionally, eculizumab treatment led to lower serum creatinine levels (mean differences (MD) = 126.931μmoI/L, 95% CI: 115.572μmoI/L-138.290μmoI/L) and an improved glomerular filtration rate (mean differences (MD) = 59.571 ml/min, 95% CI: 57.876 ml/min-61.266 mL/min). Our results also indicate that the use of eculizumab reduces the likelihood of rejection (odds ratio (OR) = 0.09, 95% CI: 0.01-0.22). Furthermore, the drug was effective in improving platelet counts (×10∧9/L) (mean differences (MD) = 163.421, 95% CI: 46.998-279.844) and lactate dehydrogenase levels (mean differences (MD) = 336.608 U/L, 95% CI: 164.816 U/L-508.399 U/L).

CONCLUSIONS

Based on the meta-analysis, treatment with eculizumab can reduce dialysis rates and improve patients' quality of life by enhancing renal function.

Safety and pharmacodynamic efficacy of eculizumab in aneurysmal subarachnoid hemorrhage (CLASH): A phase 2a randomized clinical trial

INTRODUCTION

Complement C5 antibodies reduce brain injury after experimental subarachnoid hemorrhage.

PATIENTS AND METHODS

In this randomized, controlled, open-label, phase 2a clinical trial with blinded-outcome assessment, we included adult aneurysmal subarachnoid hemorrhage (aSAH) patients admitted to a tertiary referral center ⩽11 h after ictus. Patients were randomized (1:1) to eculizumab plus care as usual or to care as usual. Eculizumab (1200 mg) was administered <12 h, and on days 3 and 7 after ictus. In the intervention group, all patients received prophylactic antibiotics and, after a protocol amendment, fluconazole if indicated. Primary outcome was C5a concentration in cerebrospinal fluid (CSF) on day 3 after ictus. Safety was monitored during 4 weeks. In each group, 13 patients with CSF assessments were needed to detect a 55% reduction in CSF C5a concentration.

RESULTS

From October 2018 to May 2021, we enrolled 31 patients of whom 26 with CSF samples, 13 per group. Median C5a concentration in CSF on day 3 was 251 pg/ml [IQR: 103-402] in the intervention group and 371 pg/ml [IQR: 131-534] in the control group (p = 0.29). Infections occurred in two patients in the intervention group and four patients in the control group. One patient in the intervention group developed a C. albicans meningitis prior to the protocol amendment.

DISCUSSION AND CONCLUSION

One dose of eculizumab did not result in a ⩾ 55% decrease in C5a concentration in CSF on day 3 after aSAH. The study did not reveal new safety concerns, except for a C. albicans drain-related infection prior to antifungal monitoring and treatment.

TRIAL REGISTRATION

EudraCT 2017-004307-51, https://www.clinicaltrialsregister.eu/.

Recommendations for the individualised management of atypical hemolytic uremic syndrome in adults

Background

Despite significant advances in therapeutic management of atypical hemolytic uremic syndrome (aHUS), guidelines are not timely updated and achieving a consensus on management recommendations remains a topic of ongoing discussion.

Methods

A Scientific Committee with five experts was set up. A literature review was conducted and publications addressing the classification of aHUS, patient profiles and therapeutic approach were selected. Recommendations were proposed at an initial meeting, evaluated through an online questionnaire and validated during a second meeting.

Results

Patients with confirmed or clear suspicion of aHUS should be treated with C5 inhibitors within 24 h of the diagnosis or suspicion of aHUS. Treatment monitoring and the decision to interrupt treatment should be individualised according to the risk of relapse and each patient's evolution. aHUS with a genetic variant or associated with pregnancy should be treated for at least 6-12 months; de novo aHUS associated with kidney transplant until renal function is recovered and genetic variants are ruled out; aHUS associated with malignant hypertension until genetic variants are ruled out; aHUS associated with non-kidney transplant, autoimmune diseases, infection-or drug-induced until the thrombotic microangiopathy is resolved. Patients with a high risk of relapse should be treated for longer than 6-12 months.

Conclusion

These recommendations provides physicians who are not familiar with the disease with recommendations for the management of aHUS in adults. The experts who participated advocate early treatment, maintenance for at least 6-12 months and treatment interruption guided by genetic background, trigger factors, risk of relapse and evolution.

Genetic, clinical, and pathological study of patients with severe hypertension-associated renal microangiopathy

BACKGROUND

Severe hypertension may be a prominent manifestation of complement-mediated thrombotic microangiopathy. Furthermore, patients with severe hypertension-associated thrombotic microangiopathy may present with concurrent hematologic abnormalities that mimic complement-mediated thrombotic microangiopathy. Whether or not severe hypertension-associated thrombotic microangiopathy is associated with genetic susceptibility in complement- and/or coagulation-pathway genes remains unclear, and there is thus a need to identify clinicopathological clues to distinguish between these entities.

METHODS

Forty-five patients with concomitant severe hypertension and thrombotic microangiopathy on kidney biopsy were identified retrospectively. Whole-exome sequencing was performed to identify rare variants in 29 complement- and coagulation-cascade genes. Clinicopathological features were compared between patients with severe hypertension-associated thrombotic microangiopathy and complement-mediated thrombotic microangiopathy with severe hypertension.

RESULTS

Three patients with pathogenic variants diagnostic of complement-mediated thrombotic microangiopathy and two with anti-factor H antibody positivity were diagnosed with complement-mediated thrombotic microangiopathy with severe hypertension. Among the 40 patients with severe hypertension-associated thrombotic microangiopathy, 53 rare variants of uncertain significance were found in the analyzed genes in 34 (34/40, 85%) patients, of whom 12 patients harbored two or more variants. Compared with complement-mediated thrombotic microangiopathy patients with severe hypertension, patients with severe hypertension-associated thrombotic microangiopathy were more likely to have left ventricular wall thickening (p < 0.001), less-severe acute glomerular thrombotic microangiopathy lesions including mesangiolysis and subendothelial space widening (both p < 0.001), and less arteriolar thrombosis formation (p < 0.001).

CONCLUSIONS

Rare genetic variants involving complement and coagulation pathways can be found in patients with severe hypertension-associated thrombotic microangiopathy; their role needs further investigation. Cardiac remodeling and acute glomerular TMA lesions may help to differentiate between severe hypertension-associated thrombotic microangiopathy and complement-mediated thrombotic microangiopathy with severe hypertension.

Drugs in treating paediatric acute kidney injury

Acute kidney injury (AKI) is a complex syndrome which affects a significant proportion of hospitalized children. The breadth and impact of AKI on health outcomes in both adults and children have come to the fore in recent years with increasing awareness encouraging research advancement. Despite this, management strategies for most types of AKI remain heavily reliant on fluid and electrolyte management, hemodynamic optimization, nephrotoxin avoidance and appropriate initiation of kidney replacement therapy. Specific drugs targeting the mechanisms involved in AKI remain elusive. Recent improvement in appreciation of the complexity of AKI pathophysiology has allowed for greater opportunity to consider novel therapeutic agents. A number of drugs specifically targeting AKI are in various stages of development. This review will consider some novel and repurposed agents; interrogate the plausibility of the proposed mechanisms of action, as they relate to what we know about the pathophysiology of AKI; and review the level of existing literature supporting their efficacy. The evidence base, particularly in children, is limited.

Clinical advances in immunotherapy for immune-mediated glomerular diseases

BACKGROUND AND OBJECTIVE

Due to the suboptimal therapeutic efficacy and potential adverse effects associated with traditional immunosuppressive medications, there has been an increasing emphasis on the development and utilization of immunotherapies. This paper aims to provide clinicians with valuable insights for selecting appropriate therapeutic approaches and contribute to the development of novel immunotherapeutic drugs.

MAIN BODY

This paper categorizes the immunotherapeutic drugs that are used for the treatment of immune-mediated glomerular diseases into three groups: immunotherapies targeting antigen-presenting cells (anti-CD80), immunotherapies targeting T/B cells (anti-CD20, anti-CD22, BAFF and APRIL inhibitors, CD40-CD40L inhibitors, proteasome inhibitors, Syk inhibitors, and Btk inhibitors), and immunotherapies targeting the complement system (C5 inhibitors, C5a/C5aR inhibitors, C3 inhibitors, MASP2 inhibitors, factor B inhibitors, and factor D inhibitors). The article then provides a comprehensive overview of advances related to these immunotherapeutic drugs in clinical research.

CONCLUSION

Certain immunotherapeutic drugs, such as rituximab, belimumab, and eculizumab, have exhibited notable efficacy in treating specific immune-mediated glomerular diseases, thereby providing novel therapeutic approaches for patients. Nonetheless, the efficacy of numerous immunotherapeutic drugs remains to be substantiated.

The role of complement in kidney disease

The complement cascade comprises soluble and cell surface proteins and is an important arm of the innate immune system. Once activated, the complement system rapidly generates large quantities of protein fragments that are potent mediators of inflammatory, vasoactive and metabolic responses. Although complement is crucial to host defence and homeostasis, its inappropriate or uncontrolled activation can also drive tissue injury. For example, the complement system has been known for more than 50 years to be activated by glomerular immune complexes and to contribute to autoimmune kidney disease. Notably, the latest research shows that complement is also activated in kidney diseases that are not traditionally thought of as immune-mediated, including haemolytic-uraemic syndrome, diabetic kidney disease and focal segmental glomerulosclerosis. Several complement-targeted drugs have been approved for the treatment of kidney disease, and additional anti-complement agents are being investigated in clinical trials. These drugs are categorically different from other immunosuppressive agents and target pathological processes that are not effectively inhibited by other classes of immunosuppressants. The development of these new drugs might therefore have considerable benefits in the treatment of kidney disease.

Delving into Molecular Pathways: Analyzing the Mechanisms of Action of Monoclonal Antibodies Integrated in IMGT/mAb-DB for Myasthenia Gravis

BACKGROUND

Myasthenia Gravis (MG) is a rare autoimmune disease presenting with auto-antibodies that affect the neuromuscular junction. In addition to symptomatic treatment options, novel therapeutics include monoclonal antibodies (mAbs). IMGT®, the international ImMunoGeneTics information system®, extends the characterization of therapeutic antibodies with a systematic description of their mechanisms of action (MOA) and makes them available through its database for mAbs and fusion proteins, IMGT/mAb-DB.

METHODS

Using available literature data combined with amino acid sequence analyses from mAbs managed in IMGT/2Dstructure-DB, the IMGT® protein database, biocuration allowed us to define in a standardized way descriptions of MOAs of mAbs that target molecules towards MG treatment.

RESULTS

New therapeutic targets include FcRn and molecules such as CD38, CD40, CD19, MS4A1, and interleukin-6 receptor. A standardized graphical representation of the MOAs of selected mAbs was created and integrated within IMGT/mAb-DB. The main mechanisms involved in these mAbs are either blocking or neutralizing. Therapies directed to B cell depletion and plasma cells have a blocking MOA with an immunosuppressant effect along with Fc-effector function (MS4A1, CD38) or FcγRIIb engager effect (CD19). Monoclonal antibodies targeting the complement also have a blocking MOA with a complement inhibitor effect, and treatments targeting T cells have a blocking MOA with an immunosuppressant effect (CD40) and Fc-effector function (IL6R). On the other hand, FcRn antagonists present a neutralizing MOA with an FcRn inhibitor effect.

CONCLUSION

The MOA of each new mAb needs to be considered in association with the immunopathogenesis of each of the subtypes of MG in order to integrate the new mAbs as a viable and safe option in the therapy decision process. In IMGT/mAb-DB, mAbs for MG are characterized by their sequence, domains, and chains, and their MOA is described.

Therapeutic apheresis in renal transplantation: An update

Therapeutic apheresis (TA) plays a significant role in various aspects of renal transplantation. It has been a necessary preconditioning component in ABO incompatible kidney transplants and an important modality in the removal of anti-human leukocyte antigen (HLA) antibodies both in the context of desensitization protocols that have been developed to allow highly sensitized kidney transplant candidates to be successfully transplanted and as treatment of antibody mediated rejection episodes post transplantation. In addition, TA has been used with various results for the management of recurrent focal segmental glomerulosclerosis. The purpose of this review is to examine the evidence supporting the application of TA as an adjunctive therapeutic option to immunosuppressive agents in protocols both before and after kidney transplantation.

Shiga toxin targets the podocyte causing hemolytic uremic syndrome through endothelial complement activation

BACKGROUND

Shiga toxin (Stx)-producing Escherichia coli hemolytic uremic syndrome (STEC-HUS) is the leading cause of acute kidney injury in children, with an associated mortality of up to 5%. The mechanisms underlying STEC-HUS and why the glomerular microvasculature is so susceptible to injury following systemic Stx infection are unclear.

METHODS

Transgenic mice were engineered to express the Stx receptor (Gb3) exclusively in their kidney podocytes (Pod-Gb3) and challenged with systemic Stx. Human glomerular cell models and kidney biopsies from patients with STEC-HUS were also studied.

FINDINGS

Stx-challenged Pod-Gb3 mice developed STEC-HUS. This was mediated by a reduction in podocyte vascular endothelial growth factor A (VEGF-A), which led to loss of glomerular endothelial cell (GEnC) glycocalyx, a reduction in GEnC inhibitory complement factor H binding, and local activation of the complement pathway. Early therapeutic inhibition of the terminal complement pathway with a C5 inhibitor rescued this podocyte-driven, Stx-induced HUS phenotype.

CONCLUSIONS

This study potentially explains why systemic Stx exposure targets the glomerulus and supports the early use of terminal complement pathway inhibition in this devastating disease.

FUNDING

This work was supported by the UK Medical Research Council (MRC) (grant nos. G0901987 and MR/K010492/1) and Kidney Research UK (grant nos. TF_007_20151127, RP42/2012, and SP/FSGS1/2013). The Mary Lyon Center is part of the MRC Harwell Institute and is funded by the MRC (A410).