Terminal complement inhibitor eculizumab in atypical hemolytic-uremic syndrome

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.

Correlation between a 2-week change in platelet count and clinical outcomes after the initiation of ravulizumab treatment in adult patients with atypical hemolytic uremic syndrome: post-hoc analysis of the phase III trial

BACKGROUND

Atypical hemolytic uremic syndrome (aHUS) is a rare disease with poor outcomes when untreated, in which ravulizumab or eculizumab are the standard of care where available. It has been proposed to regularly monitor platelet counts as an early response to ravulizumab or eculizumab. This study aimed to investigate the association between the early response to ravulizumab treatment and renal outcomes through 26 weeks in complement inhibitor-naïve adults with aHUS.

METHODS

Adult patients with aHUS enrolled in the ALXN1210-aHUS-311 phase III study of ravulizumab were divided into two groups according to the achievement of complete thrombotic microangiopathy (TMA) response, i.e., platelet count and lactate dehydrogenase (LDH) normalization and ≥ 25% improvement in serum creatinine (sCr) from baseline, by 26 weeks and baseline characteristics were compared. Changes in hematologic parameters, platelet count and LDH, were compared between the two groups. Finally, we examined whether early hematologic improvement was associated with renal recovery (dialysis discontinuation or ≥ 25% improvement in sCr from baseline) through 26 weeks.

RESULTS

Of 56 ravulizumab-treated patients, 30 achieved complete TMA response for 26 weeks, and 26 did not. Patients with complete TMA response showed rapid improvements in platelet counts. In patients without complete TMA response, delayed normalization of platelet counts was observed. By day 15, 93.3% (28/30) of patients with complete TMA response at 26 weeks and 26.9% (7/26) of patients without complete TMA response achieved platelet normalization. At 26 weeks, 62.5% (35/56) achieved renal recovery; however, 37.5% (21/56) did not. In patients with renal recovery, 85.7% (30/35) of patients had platelet count normalization by day 15; in patients without renal recovery, 23.8% (5/21) of patients had platelet count normalization (P < 0.0001). Receiver operator characteristic curve analysis showed a moderate association between platelet counts on day 8/15 and renal recovery within 26 weeks (day 8: area under the curve [AUC] = 0.7985; day 15: AUC = 0.8406).

CONCLUSIONS

Platelet count normalization occurred in 62.5% (35/56) by day 15 after ravulizumab initiation and was associated with renal recovery through 26 weeks in complement inhibitor-naïve adults with aHUS.

TRIAL REGISTRATION

This study was performed as a post-hoc analysis of the ALXN1210-aHUS-311 phase III clinical trial (NCT02949128, registered October 25, 2016).

Outcomes from the International Society of Nephrology Hemolytic Uremic Syndromes International Forum

Hemolytic uremic syndromes (HUSs) are a heterogeneous group of conditions, only some of which are mediated by complement (complement-mediated HUS). We report the outcome of the 2023 International Society of Nephrology HUS International Forum where a global panel of experts considered the current state of the art, identified areas of uncertainty, and proposed optimal solutions. Areas of uncertainty and areas for future research included the nomenclature of HUS, novel complement testing strategies, identification of biomarkers, genetic predisposition to atypical HUS, optimal dosing and withdrawal strategies for C5 inhibitors, treatment of kidney transplant recipients, disparity of access to treatment, and the next generation of complement inhibitors in complement-mediated HUS. The current rationale for optimal patient management is described.

Podocyte-targeted therapies - progress and future directions

Podocytes are the key target cells for injury across the spectrum of primary and secondary proteinuric kidney disorders, which account for up to 90% of cases of kidney failure worldwide. Seminal experimental and clinical studies have established a causative link between podocyte depletion and the magnitude of proteinuria in progressive glomerular disease. However, no substantial advances have been made in glomerular disease therapies, and the standard of care for podocytopathies relies on repurposed immunosuppressive drugs. The past two decades have seen a remarkable expansion in understanding of the mechanistic basis of podocyte injury, with prospects increasing for precision-based treatment approaches. Dozens of disease-causing genes with roles in the pathogenesis of clinical podocytopathies have been identified, as well as a number of putative glomerular permeability factors. These achievements, together with the identification of novel targets of podocyte injury, the development of potential approaches to harness the endogenous podocyte regenerative potential of progenitor cell populations, ongoing clinical trials of podocyte-specific pharmacological agents and the development of podocyte-directed drug delivery systems, contribute to an optimistic outlook for the future of glomerular disease therapy.

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.

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.

Postpartum Renal Cortical Necrosis: A Case Series

Rationale & Objective

Postpartum renal cortical necrosis (postpartum RCN) is a severe form of obstetric acute kidney injury. This study aimed to identify clinicopathologic features in Chinese postpartum RCN cases to determine how pathologic findings may contribute to the treatment and prognosis.

Study Design

Single-center, case series.

Setting & Participants

Twelve patients with postpartum RCN had kidney biopsies at Peking University First Hospital between 2014 and 2021. The diagnosis of postpartum RCN was made according to typical magnetic resonance imaging or pathologic features. Clinical, laboratory, and pathologic data were compared between patients with estimated glomerular filtration rate <30 (poor outcome) and ≥30 mL/min/1.73 m2 after 6 months.

Observations

All patients with postpartum RCN presented with stage 3 acute kidney injury attributed to a probable atypical hemolytic uremic syndrome. Pregnancy terminations occurred at a median gestational age of 35.5 weeks. Kidney biopsy was performed from 18 days to 4 months from delivery. On biopsy, hemoglobin, platelet count, and lactate dehydrogenase levels had been restored to 137 g/L, 214 × 109/L, and 231.50 ± 65.01 U/L, respectively. Four patients exhibited poor outcome, demonstrating higher schistocyte count, serum creatinine, and mean arterial pressure at onset. Pathologically, glomerular segmental sclerosis was prevalent. The "not otherwise specified" variant was the most common type, followed by collapsing variant, cellular variant, and tip variant. Patients with poor kidney outcome had more glomerular coagulative necrosis, capillary thrombosis, extensive cortical coagulative necrosis, and pronounced arteriole/artery lesions including increased interlobular arteriole intimal edema and fibrin thrombosis, but a lower occurrence of segmental sclerosis.

Limitations

Limited sample size and retrospective design.

Conclusions

We identified key pathologic features in patients with postpartum RCN and atypical hemolytic uremic syndrome, highlighting the necessity for more effective therapeutic options. There is a clear demand for noninvasive biomarkers that can accurately track disease progression and inform treatment duration for long-term outcomes improvement.

Hemostasis and complement in allogeneic hematopoietic stem cell transplantation: clinical significance of two interactive systems

Hematopoietic stem cell transplantation (HCT) represents a curative treatment option for certain malignant and nonmalignant hematological diseases. Conditioning regimens before HCT, the development of graft-versus-host disease (GVHD) in the allogeneic setting, and delayed immune reconstitution contribute to early and late complications by inducing tissue damage or humoral alterations. Hemostasis and/or the complement system are biological regulatory defense systems involving humoral and cellular reactions and are variably involved in these complications after allogeneic HCT. The hemostasis and complement systems have multiple interactions, which have been described both under physiological and pathological conditions. They share common tissue targets, such as the endothelium, which suggests interactions in the pathogenesis of several serious complications in the early or late phase after HCT. Complications in which both systems interfere with each other and thus contribute to disease pathogenesis include transplant-associated thrombotic microangiopathy (HSCT-TMA), sinusoidal obstruction syndrome/veno-occlusive disease (SOS/VOD), and GVHD. Here, we review the current knowledge on changes in hemostasis and complement after allogeneic HCT and how these changes may define clinical impact.

Risk factors of death or chronic renal replacement therapy requirements in patients with thrombotic microangiopathies without ADAMTS-13 deficiency

Thrombotic microangiopathy (TMA), characterized by microangiopathic hemolytic anemia, thrombocytopenia, and multisystem organ dysfunction, is a life-threatening disease. Patients with TMA who do not exhibit a severe ADAMTS-13 deficiency (defined as a disintegrin-like and metalloprotease with thrombospondin type 1 motif no. 13 activity ≥10%: TMA-13n) continue to experience elevated mortality rates. This study explores the prognostic indicators for augmented mortality risk or necessitating chronic renal replacement therapy (composite outcome: CO) in TMA-13n patients. We included 42 TMA-13n patients from January 2008 to May 2018. Median age of 41 years and 60% were female. At presentation, 62% required dialysis, and 57% warranted intensive care unit admission. CO was observed in 45% of patients, including a 9-patient mortality subset. Multivariate logistic regression revealed three independent prognostic factors for CO: early administration of eculizumab (median time from hospitalization to eculizumab initiation: 5 days, range 0-19 days; odds ratio [OR], 0.14; 95% confidence interval [CI], 0.02-0.94), presence of neuroradiological lesions (OR, 6.67; 95% CI, 1.12-39.80), and a PLASMIC score ≤4 (OR, 7.39; 95% CI, 1.18-46.11). In conclusion, TMA-13n patients exhibit a heightened risk of CO in the presence of low PLASMIC scores and neuroradiological lesions, while early eculizumab therapy was the only protective factor.

Therapeutic Plasma Exchange to Reverse Plasma Failure in Multiple Organ Dysfunction Syndrome

Plasma plays a crucial role in maintaining health through regulating coagulation and inflammation. Both are essential to respond to homeostatic threats such as traumatic injury or microbial infection; however, left unchecked, they can themselves cause damage. A well-functioning plasma regulatory milieu controls the location, intensity, and duration of the response to injury or infection. In contrast, plasma failure can be conceptualized as a state in which these mechanisms are overwhelmed and unable to constrain coagulation and inflammation appropriately. This dysregulated state causes widespread tissue damage and multiple organ dysfunction syndrome. Unlike plasma derangements caused by individual factors, plasma failure is characterized by a heterogeneous set of plasma component deficiencies and excesses. Targeted therapies such as factor replacement or recombinant antibodies are thus inadequate to restore plasma function. Therapeutic plasma exchange offers the unique ability to remove harmful factors and replete exhausted components, thereby reestablishing appropriate regulation of coagulation and inflammation.

IgG-immunoadsorptions and eculizumab combination in STEC-hemolytic and uremic syndrome pediatric patients with neurological involvement

BACKGROUND

Neurological complications pose a significant threat in pediatric hemolytic and uremic syndrome (HUS) resulting from infections with Shiga toxin-producing Escherichia coli (STEC), with no established treatment. The involvement of complement activation in the pathogenesis of STEC-HUS is acknowledged, and eculizumab (ECZ), a terminal complement blocker, has been documented in several pediatric series with inconsistent results. Antibody-mediated mechanisms have also been suggested, with IgG-immunoadsorption (IgIA) showing promise in adults with neurological complications. We aimed to assess the benefit of combining IgIA with ECZ in pediatric patients with neurological STEC-HUS compared to patients treated with ECZ alone or supportive care.

METHODS

Multicenter retrospective study conducted on pediatric patients (< 18 years) with neurological STEC-HUS treated with IgIA + ECZ or ECZ alone from 2010 to 2020 in France. A historical cohort treated with supportive care served as controls. Primary outcome included survival and neurological evaluation at 1-year follow-up (dichotomized as normal vs. abnormal).

RESULTS

A total of 42 children were included: 18 treated with IgIA + ECZ, 24 with ECZ alone, and 27 with supportive care. Although there was no significant difference in survival between groups, three deaths occurred in the control group in the acute phase, while none was reported in both the IgIA + ECZ and ECZ alone groups, despite presenting with more severe neurological symptoms for IgIA + ECZ patients. No significant association was found between treatment group and 1-year neurological evaluation after adjustment for age, sex, and initial neurological presentation.

CONCLUSIONS

Systematic association of IgIA + ECZ is not supported for all neurological STEC-HUS pediatric patients; potential rescue therapy for severe cases warrants consideration.

Thrombotic thrombocytopenic purpura: 100 years of research on Moschcowitz syndrome

ABSTRACT

In the 100 years since Eli Moschcowitz reported the first case of thrombotic thrombocytopenic purpura (TTP), there has been remarkable awareness and progress in the diagnosis and management of this rare blood disorder. This progress initially was the result of careful clinical observations followed by well thought-out therapeutic interventions, with dual goals of both improving outcomes and discerning the pathophysiology of TTP. The discovery of the ADAMTS13 protease set in motion the efforts to more accurately define the specific etiologies of thrombotic microangiopathies (TMAs) based on objective, scientific data rather than clinical characterizations alone. This accurate differentiation led to better and more revealing clinical trials and advancements in the treatment of TTP and other TMAs. Further advances followed and included improvements in immune-suppressive therapy and targeted therapies of immune-mediated TTP (iTTP; caplacizumab) and congenital TTP (cTTP; recombinant ADAMTS13). The longitudinal study of patients with TTP revealed the unexpected risk for long-term complications in both patients with iTTP and those with cTTP in remission. Ongoing studies aim to further understand the prevalence, mechanisms, and appropriate screening for these mood disorders, neurocognitive deficits, and cardiovascular complications that develop at remarkably high rates and are associated with a decreased life expectancy. These discoveries are a result of the collaborative efforts of investigators worldwide that have been fostered by the frequent interactions of investigators via the International TTP Working Group meetings and TMA workshops held regularly at international meetings. These efforts will support the rapid pace of discovery and improved understanding of this rare disease.

Antibodies and complement are key drivers of thrombosis

Venous thromboembolism (VTE) is a common, deadly disease with an increasing incidence despite preventive efforts. Clinical observations have associated elevated antibody concentrations or antibody-based therapies with thrombotic events. However, how antibodies contribute to thrombosis is unknown. Here, we show that reduced blood flow enabled immunoglobulin M (IgM) to bind to FcμR and the polymeric immunoglobulin receptor (pIgR), initiating endothelial activation and platelet recruitment. Subsequently, the procoagulant surface of activated platelets accommodated antigen- and FcγR-independent IgG deposition. This leads to classical complement activation, setting in motion a prothrombotic vicious circle. Key elements of this mechanism were present in humans in the setting of venous stasis as well as in the dysregulated immunothrombosis of COVID-19. This antibody-driven thrombosis can be prevented by pharmacologically targeting complement. Hence, our results uncover antibodies as previously unrecognized central regulators of thrombosis. These findings carry relevance for therapeutic application of antibodies and open innovative avenues to target thrombosis without compromising hemostasis.

Complement system activation: bridging physiology, pathophysiology, and therapy

The complement system is a set of over 50 proteins that constitutes an essential part of the innate immune system. Complement system activation involves an organized proteolytic cascade. Overactivation of complement system activation is the main pathogenic mechanism of several diseases and contributes to the manifestations of many other conditions. This review describes the normal complement system and the role for complement dysregulation in critical illnesses, notably sepsis and acute respiratory distress syndrome. Complement activation is involved in the immune system response to pathogens but, when excessive, can contribute to tissue damage, runaway inflammation, and capillary leakage syndrome. Complement overactivation may play a key role in severe forms of coronavirus disease 2019 (COVID-19). Two diseases whose manifestations are mainly caused by complement overactivation, namely, atypical hemolytic and uremic syndrome (aHUS) and myasthenia gravis, are discussed. A diagnostic algorithm for aHUS is provided. Early complement-inhibiting therapy has been proven effective. When renal transplantation is required, complement-inhibiting drugs can be used prophylactically to prevent aHUS recurrence. Similarly, acetylcholine-receptor autoantibody-positive generalized myasthenia gravis involves complement system overactivation and responds to complement inhibition. The two main complement inhibitors used in to date routine are eculizumab and ravulizumab. The main adverse event is Neisseria infection, which is rare and preventable, but can be fatal. The complement system is crucial to health but, when overactivated, can cause or contribute to disease. Effective complement inhibitors are now available, although additional data are required to determine optimal regimens. Further research is also needed to better understand the complement system, develop advanced diagnostic tools, and identify markers that allow the personalization of treatment strategies.

The role of immunoglobulin transport receptor, neonatal Fc receptor in mucosal infection and immunity and therapeutic intervention

The neonatal Fc receptor (FcRn) can transport IgG and antigen-antibody complexes participating in mucosal immune responses that protect the host from most pathogens' invasion via the respiratory, digestive, and urogenital tracts. FcRn expression can be triggered upon stimulation with pathogenic invasion on mucosal surfaces, which may significantly modulate the innate immune response of the host. As an immunoglobulin transport receptor, FcRn is implicated in the pathophysiology of immune-related diseases such as infection and autoimmune disorders. In this review, we thoroughly summarize the recent advancement of FcRn in mucosal immunity and its therapeutic strategy. This includes insights into its regulation mechanisms of FcRn expression influenced by pathogens, its emerging role in mucosal immunity and its potential probability as a therapeutic target in infection and autoimmune diseases.

The role of complement in kidney disease: conclusions from a Kidney Disease: Improving Global Outcomes (KDIGO) Controversies Conference

Uncontrolled complement activation can cause or contribute to glomerular injury in multiple kidney diseases. Although complement activation plays a causal role in atypical hemolytic uremic syndrome and C3 glomerulopathy, over the past decade, a rapidly accumulating body of evidence has shown a role for complement activation in multiple other kidney diseases, including diabetic nephropathy and several glomerulonephritides. The number of available complement inhibitor therapies has also increased during the same period. In 2022, Kidney Diseases: Improving Global Outcomes (KDIGO) convened a Controversies Conference, "The Role of Complement in Kidney Disease," to address the expanding role of complement dysregulation in the pathophysiology, diagnosis, and management of various glomerular diseases, diabetic nephropathy, and other forms of hemolytic uremic syndrome. Conference participants reviewed the evidence for complement playing a primary causal or secondary role in progression for several disease states and considered how evidence of complement involvement might inform management. Participating patients with various complement-mediated diseases and caregivers described concerns related to life planning, implications surrounding genetic testing, and the need for inclusive implementation of effective novel therapies into clinical practice. The value of biomarkers in monitoring disease course and the role of the glomerular microenvironment in complement response were examined, and key gaps in knowledge and research priorities were identified.

The efficacy and safety of eculizumab in patients and the role of C5 polymorphisms

Eculizumab is an orphan drug with indications for extremely rare autoimmune disorders. It is primarily prescribed for use in patients with paroxysmal nocturnal hemoglobinuria and atypical hemolytic uremic syndrome; but is also highly effective in the treatment of myasthenia gravis, among others. By binding to the C5 protein in the complement system, eculizumab effectively inhibits cellular hemolysis and autoimmune reactions. Despite this effective treatment, some patients reported no improvement in symptoms. Genetic sequencing revealed three distinct C5 mutations in the non-responders and these polymorphisms appeared to be most prevalent among Japanese, Korean and African populations. Here, we present an overview of the current and potential future applications of eculizumab, as well as the disadvantages of eculizumab treatment in patients with C5 polymorphisms.

Deciphering Complexity: Atypical Hemolytic Uremic Syndrome Unraveled in the Wake of Elective Hip Arthroplasty

Atypical hemolytic uremic syndrome (aHUS) is a rare and complex disease characterized by microangiopathic hemolytic anemia, thrombocytopenia, and acute renal failure. This case report details the clinical presentation, diagnosis, and management of a 49-year-old female who developed aHUS following elective hip arthroplasty. The patient, with a history of cardiovascular events and no prior renal disease, presented with elevated LDH levels, thrombocytopenia, and acute renal failure on the first postoperative day. A diagnostic workup confirmed aHUS, and the patient was successfully treated with therapeutic plasma exchange (TPE) and hemodialysis. The case underscores the importance of early recognition and aggressive management of aHUS, especially in the perioperative setting, and highlights the need for a multidisciplinary approach to optimize patient outcomes. Through this case, we aim to raise awareness about the potential for surgical stress to trigger aHUS and emphasize the critical role of TPE and supportive care in the treatment of this rare condition.

Atypical hemolytic uremic syndrome during induction chemotherapy in neuroblastoma, a rare phenomenon or common congenital predisposition?

Atypical hemolytic uremic syndrome (aHUS) is a complement-mediated thrombotic microangiopathy sometimes associated with germline variants in genes of the complement system. Clinical findings of microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury arise due to aberrant complement protein activation in the circulation. A 13-month-old boy with metastatic neuroblastoma (NB) developed aHUS during his first cycle of induction chemotherapy with germline testing revealing a complement factor H (CFH) gene mutation, currently classified as a variant of uncertain significance (VUS). Now he is in disease remission after successful complement blockade therapy, thus highlighting a unique presentation of aHUS in a patient with newly diagnosed NB.

Eculizumab as Salvage Treatment for Thrombotic Microangiopathy After Lung Transplantation

BACKGROUND

Thrombotic microangiopathy (TMA) is a rare complication after lung transplantation (LT) that has seldom been characterized in detail. Recent evidence has linked TMA other than primary atypical hemolytic uremic syndrome (aHUS) with hyperactivation of the complement alternative pathway. The focus of this investigation was to analyze the treatment response with eculizumab in TMA after LT.

METHODS

Case series where we have studied 11 patients with TMA after LT from 2 Spanish tertiary healthcare centers. Clinical data and response rates to eculizumab are provided.

RESULTS

The main indication for lung transplant was chronic obstructive pulmonary disease (COPD) (36%) and most cases (82%) received bilateral LT. The median time to TMA diagnosis was 11.6 months (4.7-28.9) and the TMA trigger in the majority of cases (73%) was immunosuppressive drugs. Platelet and hemoglobin nadir were 58 × 103/µL (24-108) and 7.7 g/dL (7.1-7.9), respectively. All cases presented acute kidney injury (AKI) with a median creatinine of 4 mg/dL (3.2-4.8) and 54.5% required acute dialysis. Eculizumab was started after a median time of 8 days (6-14) with a median duration of 3 weeks (2-8). Complete TMA response was observed in 7 (63.6%) cases and hematologic response in 10 (90.9%). The time to hematologic and renal response was 23 days (13-29) and 28 days (14-46), respectively.

CONCLUSIONS

TMA after LT is infrequent but potentially devastating. Our findings suggest that short cycles of eculizumab may be effective for severe TMA after LT.

Catastrophic Thrombosis: A Narrative Review

Catastrophic thrombosis is a severe condition characterized by a hypercoagulable tendency, leading to multiple thromboembolic events in different blood vessels, usually within a short timeframe. Several conditions have been associated with the development of catastrophic thrombosis, including the catastrophic antiphospholipid syndrome, thrombotic anti-platelet factor 4 immune disorders, thrombotic microangiopathies, cancers, the hyper-eosinophilic syndrome, pregnancy, infections, trauma, and drugs. Thrombotic storm represents a medical emergency whose management represents a serious challenge for physicians. Besides the prompt start of anticoagulation, a patient's prognosis depends on early recognition and possible treatment of the underlying condition. In this narrative review, we summarize the main characteristics of catastrophic thrombosis, analyzing the various conditions triggering such life-threatening complication. Finally, an algorithm with the diagnostic workup and the initial management of patients with catastrophic thrombosis is presented.

Annual trends in atypical haemolytic uremic syndrome management in Japan and factors influencing early diagnosis and treatment: a retrospective study

Atypical haemolytic uremic syndrome (aHUS) is a rare disorder characterised by complement-mediated thrombotic microangiopathy (TMA). Despite clinical guidelines, the diagnosis and treatment of aHUS in its early stages remains challenging. This study examined the annual trends in aHUS clinical practices in Japan and explored factors influencing early diagnosis and treatment. Using data from the 2011-2020 Diagnosis Procedure Combination database, 3096 cases with the HUS disease code were identified, of which 217 were confirmed as aHUS and treated with eculizumab or plasma exchange. Early initiation, defined as starting eculizumab or plasma exchange within 7 days of admission, was the focus of the study. Our study revealed no significant changes over time in the number of aHUS diagnoses, cases treated with eculizumab, or early initiation cases. Early initiation cases underwent haemodialysis earlier and had ADAMTS13 activity measured earlier, shorter hospital stays, and lower hospitalisation costs than late initiation cases. In conclusion, we found no increase in the number of newly diagnosed aHUS cases or early treatment initiation over time. Early recognition of TMA and differentiation of the causative disease are crucial for identifying potential aHUS cases, which may lead to better patient prognoses.

Ravulizumab in Atypical Hemolytic Uremic Syndrome: An Analysis of 2-Year Efficacy and Safety Outcomes in 2 Phase 3 Trials

Rationale & Objective

Atypical hemolytic uremic syndrome (aHUS) is a rare form of thrombotic microangiopathy (TMA) caused by complement dysregulation. Ravulizumab is a C5i approved for the treatment of aHUS. This analysis assessed long-term outcomes of ravulizumab in adults and pediatric patients with aHUS.

Study Design

This analysis reports 2-year data from 2 phase 3, single-arm studies.

Setting & Participants

One study included C5i-naïve adults (NCT02949128), and the other included 2 cohorts of pediatric patients (C5i-naïve and those who switched to ravulizumab from eculizumab [pediatric switch patients]; NCT03131219).

Exposure

Patients received intravenous ravulizumab every 4-8 weeks, with the dose depending on body weight.

Outcomes

The primary endpoint in the studies of C5i-naïve patients was complete TMA response, which consisted of platelet count normalization, lactate dehydrogenase normalization, and ≥25% improvement in serum creatinine concentrations from baseline, at 2 consecutive assessments ≥4 weeks apart.

Analytical Approach

All analyses used descriptive statistics. No formal statistical comparisons were performed.

Results

In total, 86 and 92 patients were included in efficacy and safety analyses, respectively. Complete TMA response rates over 2 years were 61% and 90% in C5i-naïve adults and pediatric patients, respectively. The median increase in estimated glomerular filtration rate from baseline was maintained over 2 years in C5i-naïve adults (35 mL/min/1.73 m2) and pediatric patients (82.5 mL/min/1.73 m2). Most adverse events and serious adverse events occurred during the first 26 weeks. No meningococcal infections were reported. Improvement in the Functional Assessment of Chronic Illness Therapy - Fatigue score achieved by 26 weeks was maintained over 2 years.

Limitations

Limitations were the small sample of pediatric switch patients and limited availability of genetic data.

Conclusions

Long-term treatment with ravulizumab is well tolerated and associated with improved hematologic and renal parameters and quality of life in adults and pediatric patients with aHUS.

The Role of Genetic Testing in Adult CKD

Mounting evidence indicates that monogenic disorders are the underlying cause in a significant proportion of patients with CKD. In recent years, the diagnostic yield of genetic testing in these patients has increased significantly as a result of revolutionary developments in genetic sequencing techniques and sequencing data analysis. Identification of disease-causing genetic variant(s) in patients with CKD may facilitate prognostication and personalized management, including nephroprotection and decisions around kidney transplantation, and is crucial for genetic counseling and reproductive family planning. A genetic diagnosis in a patient with CKD allows for screening of at-risk family members, which is also important for determining their eligibility as kidney transplant donors. Despite evidence for clinical utility, increased availability, and data supporting the cost-effectiveness of genetic testing in CKD, especially when applied early in the diagnostic process, many nephrologists do not use genetic testing to its full potential because of multiple perceived barriers. Our aim in this article was to empower nephrologists to (further) implement genetic testing as a diagnostic means in their clinical practice, on the basis of the most recent insights and exemplified by patient vignettes. We stress why genetic testing is of significant clinical benefit to many patients with CKD, provide recommendations for which patients to test and which test(s) to order, give guidance about interpretation of genetic testing results, and highlight the necessity for and essential components of pretest and post-test genetic counseling.

Application of eculizumab, a terminal complement inhibitor, in the management of atypical hemolytic uremic syndrome in a 14-month-old Chinese pediatric patient: a case report

Eculizumab, a recombined humanized monoclonal antibody which possesses high affinity for the complement protein C5, is a therapeutic agent utilized in the treatment of atypical hemolytic uremic syndrome (aHUS) by inhibiting the terminal complement complex C5b-9. In a pediatric patient with aHUS of 14 months, the administration of eculizumab therapy was accompanied by the inclusion of meningococcal vaccine as part of the national immunization program. Notably, no other antibiotics were administered prior to or during the course of eculizumab treatment. Moreover, there were no occurrences of infusion reactions or meningococcal infections observed throughout the course of treatment. Due to the presence of anti-factor H antibodies and insufficient recovery, glucocorticoids and eculizumab were administered at week 0 and week 1, followed by the initiation of mycophenolate mofetil (MMF) at a dosage of 250 mg (approximately 548 mg/m2) per day starting from Day 10. Due to the recovered of complement antibody after 8 doses of eculizumab, the therapeutic interval was extended from once every 3 weeks to once a month since 9th administration. We experienced and successfully treated a rare case of aHUS with eculizumab in a 14-month-old Chinese pediatric patient.

Practical approach to thrombocytopenia in patients with sepsis: a narrative review

Thrombocytopenia frequently occurs in patients with sepsis. Disseminated intravascular coagulation (DIC) may be a possible cause of thrombocytopenia owing to its high prevalence and association with poor outcomes; however, it is important to keep the presence of other diseases in mind in sepsis practice. Thrombotic microangiopathy (TMA), which is characterized by thrombotic thrombocytopenic purpura, Shiga toxin-producing Escherichia coli hemolytic uremic syndrome (HUS), and complement-mediated HUS, is characterized by thrombocytopenia, microangiopathic hemolytic anemia, and organ damage. TMA has become widely recognized in recent years because of the development of specific treatments. Previous studies have reported a remarkably lower prevalence of TMA than DIC; however, its epidemiology is not well defined, and there may be cases in which TMA is not correctly diagnosed, resulting in poor outcomes. Therefore, it is important to differentiate DIC from TMA. Nevertheless, differentiating between DIC and TMA remains a challenge as indicated by previous reports that most patients with TMA can be diagnosed as DIC using the universal coagulation scoring system. Several algorithms to differentiate sepsis-related DIC from TMA have been suggested, contributing to improving the care of septic patients with thrombocytopenia; however, it may be difficult to apply these algorithms to patients with coexisting DIC and TMA, which has recently been reported. This review describes the disease characteristics, including epidemiology, pathophysiology, and treatment, of DIC, TMA, and other diseases with thrombocytopenia and proposes a novel practical approach flow, which is characterized by the initiation of the diagnosis of TMA in parallel with the diagnosis of DIC. This practical flow also refers to the longitudinal diagnosis and treatment flow with TMA in mind and real clinical timeframes. In conclusion, we aim to widely disseminate the results of this review that emphasize the importance of incorporating consideration of TMA in the management of septic DIC. We anticipate that this practical new approach for the diagnostic and treatment flow will lead to the appropriate diagnosis and treatment of complex cases, improve patient outcomes, and generate new epidemiological evidence regarding TMA.

Integrated Applied Clinical Pharmacology in the Advancement of Rare and Ultra-Rare Disease Therapeutics

The introduction of safe and effective rare/ultra-rare disease treatments is a focus of many biotherapeutic enterprises. Despite this increased activity, a significant unmet need remains, and the responsibility to meet this need is augmented by enhanced genomic, biologic, medical, analytical, and informatic tools. It is recognized that the development of an effective and safe rare/ultra-rare disease therapeutic faces a number of challenges with an important role noted for clinical pharmacology. Clinical pharmacology is foundationally an integrative discipline which must be embedded in and is interdependent upon understanding the pathogenic biology, clinical presentation, disease progression, and end-point assessment of the disease under study. This manuscript presents an overview and two case examples of this integrative approach, the development of C5-targeted therapeutics for the treatment of generalized myasthenia gravis and asfotase alpha for the treatment of hypophosphatasia. The two presented case examples show the usefulness of understanding the biological drivers and clinical course of a rare disease, having relevant animal models, procuring informative natural history data, importing assessment tools from relevant alternative areas, and using integrated applied clinical pharmacology to inform target engagement, dose, and the cascade of pharmacodynamic and clinical effects that follow. Learnings from these programs include the importance of assuring cross-validation of assays throughout a development program and continued commitment to understanding the relationship among the array of Pd end points and clinical outcomes. Using an integrative approach, substantive work remains to be done to meet the unmet needs of patients with rare/ultra-rare disease.

Transplant-associated thrombotic microangiopathy in pediatrics: incidence, risk factors, therapeutic options, and outcome based on data from a single center

Background

Transplant-associated thrombotic microangiopathy (TA-TMA) is a critical complication of hematopoietic stem cell transplantation. Awareness about TA-TMA has increased in recent years, resulting in the implementation of TA-TMA screening in most centers.

Methods

Retrospective analysis of children who underwent autologous or allogeneic hematopoietic stem cell transplantation at our center between January 2018 and December 2022 was conducted to evaluate the incidence, clinical features, and outcomes of TA-TMA following the administration of different therapeutic options.

Results

A total of 45 patients comprised the study cohort, of whom 10 developed TA-TMA with a cumulative incidence of 22% by 100 days after transplantation. Patients with and without TA-TMA in our cohort displayed an overall survival of 80% and 88%, respectively (p = 0.48), and a non-relapse mortality of 0% and 5.7%, respectively (p = 0.12), at 1 year after transplantation. Risk factors for TA-TMA development included allogeneic transplantation and total body irradiation-based conditioning regime. Among the 10 patients with TA-TMA, 7 did not meet the high-risk criteria described by Jodele and colleagues. Of these seven patients, two responded to calcineurin-inhibitor withdrawal without further therapy and five developed multiorgan dysfunction syndrome and were treated with anti-inflammatory steroids (prednisone), and all responded to therapy. The three patients with high-risk TA-TMA were treated with complement blockade or prednisone, and all responded to therapy.

Conclusion

TA-TMA is a multifactorial complication with high morbidity rates. Patients with high-risk TA-TMA may benefit from complement blockade using eculizumab. No consensus has been reached regarding therapy for patients who do not meet high-risk criteria. Our analysis showed that these patients may respond to anti-inflammatory treatment with prednisone.

Recombinant Adeno-Associated Virus Vectors for Gene Therapy of the Central Nervous System: Delivery Routes and Clinical Aspects

The Central Nervous System (CNS) is vulnerable to a range of diseases, including neurodegenerative and oncological conditions, which present significant treatment challenges. The blood-brain barrier (BBB) restricts molecule penetration, complicating the achievement of therapeutic concentrations in the CNS following systemic administration. Gene therapy using recombinant adeno-associated virus (rAAV) vectors emerges as a promising strategy for treating CNS diseases, demonstrated by the registration of six gene therapy products in the past six years and 87 ongoing clinical trials. This review explores the implementation of rAAV vectors in CNS disease treatment, emphasizing AAV biology and vector engineering. Various administration methods-such as intravenous, intrathecal, and intraparenchymal routes-and experimental approaches like intranasal and intramuscular administration are evaluated, discussing their advantages and limitations in different CNS contexts. Additionally, the review underscores the importance of optimizing therapeutic efficacy through the pharmacokinetics (PK) and pharmacodynamics (PD) of rAAV vectors. A comprehensive analysis of clinical trials reveals successes and challenges, including barriers to commercialization. This review provides insights into therapeutic strategies using rAAV vectors in neurological diseases and identifies areas requiring further research, particularly in optimizing rAAV PK/PD.

Recurrent complement-mediated Hemolytic uremic syndrome after kidney transplantation

Hereditary forms of hemolytic uremic syndrome (HUS), formerly known as atypical HUS, typically involve mutations in genes encoding for components of the alternative pathway of complement, therefore they are often referred to as complement-mediated HUS (cHUS). This condition has a high risk of recurrence in the transplanted kidney, leading to accelerated graft loss. The availability of anti-complement component C5 antibody eculizumab has enabled successful transplantation with a notably reduced recurrence rate and improved prognosis. Open questions are related to the potential for complement inhibitor discontinuation, ideal timing of treatment withdrawal, and patient selection based on genetic abnormalities. Our review delves into the pathophysiology, classification, genetic predispositions, and management strategies for cHUS in the native and transplant kidneys.

Living with Atypical Hemolytic Uremic Syndrome in the Netherlands: Patient and Family Perspective

Introduction

Atypical hemolytic uremic syndrome (aHUS) poses a significant health challenge due to its rarity and severity within the spectrum of thrombotic microangiopathy. Despite efforts to optimize and personalize health care for patients with aHUS, understanding the individual experiences, needs, and desires of patients with aHUS and their relatives remains limited.

Methods

Here, we present a nationwide, exploratory, qualitative interview study with a direct content analysis approach. In-depth interviews and a 6-week evaluation were audio-recorded and conducted using a semistructured topic guide, based on the Institute for Positive Health (IPH) model.

Results

Analysis of 10 interviews involving 6 patients with aHUS and 13 relatives revealed the prevalence of long-term disease symptoms in adult patients, notably fatigue, which significantly impacted daily functioning. Moreover, the resilience demonstrated by patients and their relatives was noteworthy; however, the acute phase of aHUS and the unpredictable nature of disease recurrence could profoundly affect mental well-being. The emotional toll of aHUS is pervasive, with feelings of fear, guilt, and trauma persisting across disease phases in both patients and relatives. Challenges in medical care, including delays in diagnosis and the need for personalized and uniform protocols, were highlighted. Support was deemed crucial, indicating the necessity for enhancements in the accessibility to comprehensible disease information and psychological counseling. Finally, complexities surrounding genetic testing and carriership were discussed.

Conclusion

This study underscores the profound, enduring, and multifaced impact of aHUS. The insights gleaned from the experiences and needs of patients with aHUS and their relatives could lay the foundation for development and implementation of more personalized innovations in aHUS health care.

Complement or Insult: the emerging link between complement cascade deficiencies and pathology of myeloid malignancies

The complement cascade is an ancient and highly conserved arm of the immune system. The accumulating evidence highlights elevated activity of the complement cascade in cancer microenvironment and emphasizes its effects on the immune, cancer and cancer stroma cells, pointing to a role in inflammation-mediated etiology of neoplasms. The role the cascade plays in development, progression and relapse of solid tumors is increasingly recognized, however its role in hematological malignancies, especially those of myeloid origin, has not been thoroughly assessed and remains obscure. As the role of inflammation and autoimmunity in development of myeloid malignancies is becoming recognized, in this review we focus on summarizing the links that have been identified so far for complement cascade involvement in the pathobiology of myeloid malignancies. Complement deficiencies are primary immunodeficiencies that cause an array of clinical outcomes including an increased risk of a range of infectious as well as local or systemic inflammatory and thrombotic conditions. Here, we discuss the impact that deficiencies in complement cascade initiators, mid- and terminal- components and inhibitors have on the biology of myeloid neoplasms. The emergent conclusions indicate that the links between complement cascade, inflammatory signaling and the homeostasis of hematopoietic system exist, and efforts should continue to detail the mechanistic involvement of complement cascade in the development and progression of myeloid cancers.

Urinary complement biomarkers in immune-mediated kidney diseases

The complement system, an important part of the innate system, is known to play a central role in many immune mediated kidney diseases. All parts of the complement system including the classical, alternative, and mannose-binding lectin pathways have been implicated in complement-mediated kidney injury. Although complement components are thought to be mainly synthesized in the liver and activated in the circulation, emerging data suggest that complement is synthesized and activated inside the kidney leading to direct injury. Urinary complement biomarkers are likely a better reflection of inflammation within the kidneys as compared to traditional serum complement biomarkers which may be influenced by systemic inflammation. In addition, urinary complement biomarkers have the advantage of being non-invasive and easily accessible. With the rise of therapies targeting the complement pathways, there is a critical need to better understand the role of complement in kidney diseases and to develop reliable and non-invasive biomarkers to assess disease activity, predict treatment response and guide therapeutic interventions. In this review, we summarized the current knowledge on urinary complement biomarkers of kidney diseases due to immune complex deposition (lupus nephritis, primary membranous nephropathy, IgA nephropathy) and due to activation of the alternative pathway (C3 glomerulopathy, thrombotic microangiography, ANCA-associated vasculitis). We also address the limitations of current research and propose future directions for the discovery of urinary complement biomarkers.

Complement Biosensors Identify a Classical Pathway Stimulus in Complement-Mediated Hemolytic Uremic Syndrome

Complement-mediated hemolytic uremic syndrome (CM-HUS) is a thrombotic microangiopathy characterized by germline variants or acquired antibodies to complement proteins and regulators. Building upon our prior experience with the modified Ham (mHam) assay for ex vivo diagnosis of complementopathies, we have developed an array of cell-based complement "biosensors'' by selective removal of complement regulatory proteins (CD55 and CD59, CD46, or a combination thereof) in an autonomously bioluminescent HEK293 cell line. These biosensors can be used as a sensitive method for diagnosing CM-HUS and monitoring therapeutic complement blockade. Using specific complement pathway inhibitors, this model identifies IgM-driven classical pathway stimulus during both acute disease and in many patients during clinical remission. This provides a potential explanation for ~50% of CM-HUS patients who lack an alternative pathway "driving" variant and suggests at least a subset of CM-HUS is characterized by a breakdown of IgM immunologic tolerance.

Key Points

CM-HUS has a CP stimulus driven by polyreactive IgM, addressing the mystery of why 40% of CM-HUS lack complement specific variantsComplement biosensors and the bioluminescent mHam can be used to aid in diagnosis of CM-HUS and monitor complement inhibitor therapy.

Eculizumab for Shiga-toxin-induced hemolytic uremic syndrome in adults with neurological involvement

The role of eculizumab in treating Shiga-toxin-producing Escherichia coli (STEC) hemolytic uremic syndrome (HUS) patients with neurological involvement remains unclear. We describe two distinctly different STEC-HUS patients with neurologic involvement successfully managed with eculizumab, and perform a literature review of all published cases. Both patients had complete resolution of neurological symptoms after initiation of eculizumab. Eighty patients with STEC-HUS treated with eculizumab were identified in the literature, 68.7% had complete resolution of neurological symptoms. Based on our experience and literature review, three prevailing themes were noted: 1) Early eculizumab administration optimized neurological outcomes, 2) Symptom resolution may not be immediate, neurological symptoms may initially worsen before improvement, and 3) Plasma exchange yielded no benefit. Early administration of eculizumab may reverse neurotoxicity in patients with STEC-HUS.

Therapeutic plasma exchange in paediatric nephrology in Ireland

BACKGROUND

Therapeutic plasma exchange (TPE) is utilised in the management of a limited number of paediatric renal conditions. Despite its widespread acceptance and advancements in the practice of apheresis, there remains a paucity of data pertaining to paediatrics. We present a large retrospective review of our cohort of paediatric patients undergoing TPE for renal indications, outlining their outcomes and complications.

METHODS

A retrospective chart review was conducted for all patients (under 16 years) undergoing TPE for renal conditions between January 2002 and June 2019 in Ireland. Demographic and clinical data were extracted, with patients anonymised and stratified according to their pathology.

RESULTS

A total of 58 patients were identified. A total of 1137 exchanges were performed using heparin sodium anticoagulation. The median age was 35.5 months (IQR 18-110 months). The leading indication was neurological involvement in Shiga toxin-producing Escherichia coli haemolytic uraemic syndrome (STEC-HUS) (n = 29). Complications (minor or major) occurred in 65.5% (n = 38) of patients, with most experiencing minor complications 58.6% (n = 34). Asymptomatic hypocalcaemia was the most common complication in 43.1% (n = 25).

CONCLUSIONS

Our experience of TPE, spanning 1137 exchanges, proved a safe, well-tolerated therapy. Most complications were minor, and with therapy conducted in specialised centres, there are very low levels of adverse events.

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.

Eculizumab for adult patients with atypical haemolytic-uraemic syndrome: full dataset analysis of Japanese post-marketing surveillance

BACKGROUND

Eculizumab has been approved for atypical haemolytic-uraemic syndrome (aHUS) in Japan since 2013. Post-marketing surveillance enrolled patients with aHUS who received ≥ 1 dose of eculizumab to assess eculizumab safety and effectiveness.

METHODS

We evaluated serious adverse events and effectiveness endpoints, i.e., haematologic normalization, a decrease of ≥ 25% in serum creatinine (sCr) levels, and complete thrombotic microangiopathy (TMA) response in adult patients with aHUS without other underlying diseases. In addition, the difference of baseline characteristics between patients who did and did not meet effectiveness endpoints was examined.

RESULTS

In this safety and effectiveness analysis, 79 adult patients were included; median age was 54.0 years, median treatment duration was 30 weeks. Total exposure time of eculizumab was 75.51 patient-years, and 94 serious adverse events were reported in 39 patients. No unexpected safety signals were identified in this population. Mean platelet count, lactate dehydrogenase and estimated glomerular filtration rate significantly improved after 7 days of treatment. Complete TMA response, haematologic normalization and the improvement of sCr levels were met by 35.3%, 40.4% and 51.3% of patients, respectively. Median treatment duration was shorter in patients who did not achieve complete TMA response (6 weeks) than in patients who did (114 weeks). Multivariate analysis suggested that the time from the most recent TMA episode to start of eculizumab treatment was negatively associated with kidney function improvement.

CONCLUSIONS

No unexpected safety signals of eculizumab were identified in Japanese patients with aHUS in a real-world setting. Renal outcomes were negatively associated with the time from the most recent TMA episode to the initiation of eculizumab treatment.

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.

Thrombotic Microangiopathies and the Kidney

Thrombotic microangiopathy (TMA) is a pathological lesion that occurs due to endothelial injury. It can be seen in a heterogenous group of disorders, typically characterized by microangiopathic hemolytic anemia, thrombocytopenia, and end-organ ischemia. TMA can also be renal limited with no systemic manifestations. There are multiple etiologies of a TMA with complement activation being a core underlying mechanism, although the nature and extent of complement involvement can vary. A further complicated factor is the cross talk between complement, neutrophils, and coagulation pathways in the pathophysiology of TMAs. Therefore, a thorough and systematic clinical history and laboratory evaluation are critical to establish the cause and pathophysiology of a TMA. Furthermore, TMAs are associated with significant morbidity and mortality, and timely diagnosis is key for appropriate management and to prevent end-stage kidney disease and other associated complications. In this review, we focus on the pathology, mechanisms, diagnostic work up and treatment of TMAs associated with various etiologies. We also define the complement evaluations that should be conducted in these patients and further highlight the currently approved complement therapies as well as others in the pipeline.

A Severe Form of Atypical Hemolytic Uremic Syndrome in a Two-Year-Old Girl: A Case Report

Hemolytic uremic syndrome (HUS) is a prevalent cause of severe acute kidney injury in children, often leading to chronic renal damage. It is characterized by thrombotic microangiopathy (TMA), which represents a triad of microangiopathic hemolytic anemia, thrombocytopenia, and renal impairment. The choice of treatment and management strategies depends primarily on the underlying etiology. We present the case of a two-year-old girl diagnosed with rapidly progressive glomerulonephritis accompanied by hypertension necessitating renal replacement therapy. Initial laboratory findings indicated positive antinuclear antibodies, prompting immunosuppression and renal biopsy, revealing TMA with minimal chronicity changes. The treatment involved plasmapheresis and a single dose of injection rituximab, resulting in clinical recovery with an improved glomerular filtration rate. Since the anti-complement factor H antibody result was negative, the genetic etiology of atypical HUS was considered. The patient was discharged with favorable outcomes, including normal urine output and the absence of edema. This case concludes that young children with atypical HUS may present with a severe clinical course necessitating early intervention. The lack of genetic analysis facilities in severe cases should not hinder the timely initiation of plasmapheresis to prevent further injury and progression to chronic kidney disease.

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.

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.

Complement-Mediated Thrombotic Microangiopathy after Kidney Transplant: Should Treatment with C5 Inhibitor Be Lifelong?

Complement-mediated thrombotic microangiopathy (CM-TMA) is a rare and life-threatening complication that can occur in kidney transplant recipients, with various potential triggers including immunosuppressive medications. The optimal management and duration of treatment with C5 inhibitors (C5i) for CM-TMA in this patient population remain areas of ongoing investigation. We present the case of a 38-year-old female with a history of IgA nephropathy who underwent preemptive living-related kidney transplantation and subsequently developed CM-TMA 7 years post-transplant. Treatment with ravulizumab led to a rapid hematologic response and stabilized platelet counts. Serial measurements of complement functional tests and clinical stability guided the discontinuation of C5i therapy. The case highlights the complexity of managing CM-TMA in kidney transplant recipients, particularly in determining the appropriate duration of C5i therapy. The absence of an established protocol for discontinuation necessitates a personalized approach based on clinical and laboratory stability, absence of complement gene variants, and serial complement functional tests. Further prospective investigations are warranted to define the optimal strategies for monitoring and safely discontinuing C5i therapy in this unique patient population. This case underscores the importance of individualized care in the management of CM-TMA post-kidney transplantation, offering insights into potential criteria for therapy discontinuation.