Complement Inhibitor Eculizumab Research Articles

Microangiopathy in multiple myeloma: a case of carfilzomib-induced secondary thrombotic microangiopathy successfully treated with plasma exchange and complement inhibition

BackgroundThrombotic microangiopathy (TMA) is a potentially organ and life-threatening condition affecting patients with multiple myeloma (MM). Cases of proteasome inhibitor-induced TMA and specifically carfilzomib-induced TMA have been rarely reported and standards for diagnostic workup and treatment are not available.Case presentationWe describe a case of a male MM patient under salvage therapy including proteasome inhibitor carfilzomib following chemotherapy and autologous stem cell transplantation. The patient then developed acute kidney injury with clinical and laboratory signs of TMA. Hemodialysis became necessary and treatment with plasma exchange was initiated followed by therapy with C5 complement inhibitor eculizumab which led to amelioration of kidney function and hemolysis parameters.ConclusionWe report a patient with suspected proteasome inhibitor-induced secondary thrombotic microangiopathy that has been successfully treated with plasma exchange and eculizumab, a monoclonal antibody targeting complement factor C5.

#3074 CHANGES IN THE CLINICAL CHARACTERISTICS AND MANAGEMENT OF PATIENTS WITH AHUS OVER 10 YEARS: TRENDS FROM THE GLOBAL AHUS REGISTRY

Abstract Background and Aims Atypical haemolytic uraemic syndrome (aHUS) is a rare disease predominantly caused by alternative complement pathway dysregulation. Prior to 2011, before the targeted complement inhibitor eculizumab became available, aHUS frequently led to end-stage kidney disease (ESKD) and early death. Treatment with eculizumab led to notable improvements in outcomes; whether patient characteristics and management has continued to change over time is unknown. Using data from the Global aHUS Registry, we assessed clinical characteristics and management of patients with aHUS over 10 years to identify any potential trends. Method All patients enrolled in the Global aHUS Registry from 2012–2022 were included. Patients were categorised according to age at aHUS onset (adult [≥18 years] vs paediatric [<18 years]); onset of aHUS was defined as the earliest of initial symptom presentation, aHUS diagnosis, or first recorded thrombotic microangiopathy (TMA). Patient characteristics were summarised using descriptive analysis. Results Of the 1994 patients enrolled in the registry between 2012 and 2022, 33 (1.7%) were missing data on age at aHUS onset. Of the remaining 1961 patients, 813 (41.5%) were paediatric and 1148 (58.5%) were adult. Changes in patient characteristics and management are presented in Fig. 1. Plasma exchange/plasma infusion (PE/PI) prior to and including the year of enrolment was less common in paediatric than adult patients (58.5% vs. 71.3%) between 2012–2013 and declined substantially in paediatric (19.6%) relative to adult (55.1%) patients by 2020–2022. Similar proportions of paediatric patients required dialysis at the time of enrolment between 2012–2013 (5.1%) and 2020–2022 (5.9%), while numerically lower proportions of adults required dialysis over time (2012–2013, 15.2%; 2020–2022, 6.5%). The rate of paediatric patients requiring a kidney transplant prior and up to enrolment dropped from 2012–2013 (28.4%) to 2020–2022 (5.9%); however, the rate among adult patients remained comparable (2012–2013, 29.2%; 2020–2022, 27.1%). A decrease in the proportion of patients with a reported identified pathogenic variant and/or anti-CFH antibodies was observed in paediatric and adult patients between 2012–2013 (paediatric, 59.1%; adult, 45.5%) and 2020–2022 (paediatric, 49.0%; adult, 30.8%). The proportion of patients with a reported triggering event increased from 2012–2013 (paediatric, 6.3%; adult, 12.4%) to 2020–2022 (paediatric, 9.8%; adult, 28.0%). In this cohort, a total of 1208 patients were treated with eculizumab/ravulizumab between 2012 and 2022 (paediatrics, 476; adults, 732). Between 2012–2013, the median time from aHUS onset to treatment initiation was 94.9 days for paediatric patients (blue) and 51.1 days for adult patients (orange); this fell to 13.1 days in paediatrics and 24.1 days in adults between 2020–2022 (Fig. 2). Conclusion Utilisation of PE/PI to treat aHUS has decreased more in paediatric than adult patients over time. A decreased requirement for transplant in paediatric patients was evident, suggesting more paediatrics are now being diagnosed and treated earlier, leading to better outcomes with fewer patients progressing to renal failure and requiring kidney transplant. The proportion of both paediatric and adult patients with reported pathogenic variants and/or anti-CFH antibodies decreased over time and may reflect the rate at which a clinical constellation consistent with aHUS is identified. Moreover, aHUS may be recognised more frequently in the presence of a triggering condition, or a lower barrier for clinicians to suspect aHUS in recent years. Patients were more rapidly treated with a complement inhibitor, likely due to better awareness in the clinical community around complement inhibitors and the importance of early treatment initiation. Although patients with aHUS are being treated more promptly in recent years than 10 years ago, more work is needed, especially in adults, to move towards optimal clinical practice.

Germline C1GALT1C1 mutation causes a multisystem chaperonopathy

Mutations in genes encoding molecular chaperones can lead to chaperonopathies, but none have so far been identified causing congenital disorders of glycosylation. Here we identified two maternal half-brothers with a novel chaperonopathy, causing impaired protein O-glycosylation. The patients have a decreased activity of T-synthase (C1GALT1), an enzyme that exclusively synthesizes the T-antigen, a ubiquitous O-glycan core structure and precursor for all extended O-glycans. The T-synthase function is dependent on its specific molecular chaperone Cosmc, which is encoded by X-chromosomal C1GALT1C1. Both patients carry the hemizygous variant c.59C>A (p.Ala20Asp; A20D-Cosmc) in C1GALT1C1. They exhibit developmental delay, immunodeficiency, short stature, thrombocytopenia, and acute kidney injury (AKI) resembling atypical hemolytic uremic syndrome. Their heterozygous mother and maternal grandmother show an attenuated phenotype with skewed X-inactivation in blood. AKI in the male patients proved fully responsive to treatment with the complement inhibitor Eculizumab. This germline variant occurs within the transmembrane domain of Cosmc, resulting in dramatically reduced expression of the Cosmc protein. Although A20D-Cosmc is functional, its decreased expression, though in a cell or tissue-specific manner, causes a large reduction of T-synthase protein and activity, which accordingly leads to expression of varied amounts of pathological Tn-antigen (GalNAcα1-O-Ser/Thr/Tyr) on multiple glycoproteins. Transient transfection of patient lymphoblastoid cells with wild-type C1GALT1C1 partially rescued the T-synthase and glycosylation defect. Interestingly, all four affected individuals have high levels of galactose-deficient IgA1 in sera. These results demonstrate that the A20D-Cosmc mutation defines a novel O-glycan chaperonopathy and causes the altered O-glycosylation status in these patients.

Effect of Eculizumab on Iron Metabolism in Transfusion-independent Patients With Paroxysmal Nocturnal Hemoglobinuria

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare acquired bone marrow disease characterized by intravascular hemolysis, thrombophilia, and bone marrow failure.1 Treatment options for PNH remained limited until the terminal complement inhibitor eculizumab became available. Eculizumab effectively reduces intravascular hemolysis in PNH, but in almost all patients on eculizumab complement C3d-opsonized PNH erythrocytes arise and become a target of phagocytosis by macrophages in liver and spleen resulting in a variable degree of extravascular hemolysis.2 Chronic intravascular hemolysis in untreated PNH patients leads to urinary iron loss from hemosiderinuria and often results in iron deficiency.1 In contrast, in transfusion-independent PNH patients treated with eculizumab, observed increases in ferritin levels have raised concerns about possible iron overload. The major regulator of iron homeostasis is the hepatic peptide hormone hepcidin. Hepcidin modulates the iron availability for erythropoiesis by controlling both iron absorption in the duodenum and recycling of iron by macrophages by 2 mechanisms: occlusion of the open-outward conformation of the cellular exporter ferroportin, and induction of endocytosis and degradation of ferroportin.3 Hepcidin is a negative regulator of iron absorption and mobilization. High levels inhibit both duodenal iron absorption and iron release from macrophages, whereas low levels promote iron absorption.3 Recently, the hormone erythroferrone (ERFE) was discovered as main erythroid regulator of hepcidin. ERFE is produced by erythroblasts and its production is induced by erythropoietin. ERFE suppresses the production of hepcidin to facilitate iron delivery during stress erythropoiesis but also contributes to iron overload in congenital anemias with ineffective erythropoiesis such as β-thalassemia and X-linked sideroblastic anemia.4 Hyperferritinemia during eculizumab therapy has been attributed to a decline of renal iron loss, as well as iron deposition in the reticuloendothelial system (RES) as a result of C3d-mediated extravascular hemolysis.5–7 However, the effect of eculizumab on iron metabolism has not been studied well, and the role hepcidin and ERFE play in the development of hyperferritinemia is unknown. The aim of this study was to investigate how eculizumab affects iron metabolism in PNH. Therefore, a single-center observational study was conducted in the Radboudumc Expertise Center for PNH in Nijmegen, The Netherlands, and included 13 transfusion-independent PNH patients not treated with a complement inhibitor and 23 transfusion-independent PNH patients who received at least 6 months of eculizumab (Suppl. Table S1). In these patients, we characterized the association between degree of hemolysis and iron parameters, including serum hepcidin and ERFE. A detailed description of material and methods is provided in the supplemental digital content. Individual patient data are depicted in Suppl. Table S2. First, serum ferritin levels were retrospectively collected from medical records of the transfusion-independent patients on eculizumab to study ferritin levels during the course of treatment (Suppl. Figure S1). Ferritin levels increased with time. Mean increase of serum ferritin per patient per year of therapy ranged from −28.7 μg/L to 213.5 μg/L (median = 48.9 μg/L). Second, serum ferritin levels and transferrin saturation (TSAT) were measured at a single time-point in all patients (Figure 1A). Note that the duration of eculizumab therapy differed per patient at the time iron parameters were measured. Ferritin levels were significantly higher in treated patients (median, 301 μg/L; range, 11–913 μg/L) than untreated patients (median, 103 μg/L; range, 25–290 μg/L; P = 0.006). In addition, ferritin levels above the upper limit of the reference range were observed in 13 out of 23 treated patients. In patients on eculizumab, ferritin levels significantly correlated with the duration of therapy (r = 0.495, P = 0.016). TSAT did not significantly differ between the groups (P = 0.921), and in 12 out of 13 untreated patients and 22 out of 23 treated patients, TSAT was below 45%.Figure 1.: Iron parameters, and correlations between markers for intravascular and extravascular hemolysis and iron parameters in transfusion-independent PNH patients not treated with a complement inhibitor and PNH patients treated with eculizumab. (A) Serum ferritin and TSAT determined in transfusion-independent PNH patients not treated with a complement inhibitor and transfusion-independent PNH patients treated with eculizumab. Boxes show median and first and third quartiles. Whiskers extend to minimum and maximum values. Dashed lines represents the upper limits of reference ranges. In the graph depicting serum ferritin levels, the lower dashed line represents the upper limit of the reference range of ferritin for premenopausal women and the upper dashed line represents the upper limit of the reference range of ferritin for men and postmenopausal women. Statistical significant differences between groups are highlighted with bars and corresponding P-values, Mann-Whitney U test. (B) Serum hepcidin, hepcidin/ferritin ratio, and ERFE determined in transfusion-independent PNH patients not treated with a complement inhibitor and transfusion-independent PNH patients treated with eculizumab. Boxes show median and first and third quartiles. Whiskers extend to minimum and maximum values. Upper limits of reference ranges of hepcidin and hepcidin/ferritin ratios are not depicted here as these are outside the axis limits. Reference ranges of serum hepcidin levels are <0.5–13.0 nM, <0.5–16.5 nM, and <0.5–15.5 nM for premenopausal women, postmenopausal women, and men, respectively. Reference ranges of hepcidin/ferritin ratios are 3.2–176.4 pmol/μg, 9.6–150.9 pmol/μg, and 3.1–92.7 pmol/μg for premenopausal women, postmenopausal women, and men, respectively.15 For ERFE, no reference intervals are available yet. Median level of ERFE determined in 10 healthy controls is 0.8 ng/mL (range, 0.2–27.5). Statistical significant differences between groups are highlighted with bars and corresponding P-values, Mann-Whitney U test. (C) Correlation between absolute reticulocyte count and hepcidin/ferritin, and absolute reticulocyte count and ERFE in transfusion-independent PNH patients not treated with a complement inhibitor and transfusion-independent PNH patients treated with eculizumab. Two ERFE outliers (1 in the untreated group [ERFE = 43.3 ng/mL] and 1 in the treated group [ERFE = 102.9 ng/mL]) were excluded from the analysis. Spearman correlation coefficients are depicted in each graph with corresponding P-values. P-values <0.05 are considered to be significant. PNH = paroxysmal nocturnal hemoglobinuria; ERFE = erythroferrone; TSAT = transferrin saturation.In both the groups, markers for intravascular hemolysis (lactate dehydrogenase [LDH] and absolute reticulocyte count [ARC]) and extravascular hemolysis (ARC and percentage of C3d-opsonized PNH erythrocytes7) were measured. In patients on eculizumab, intravascular hemolysis was adequately inhibited; however, a variable degree of C3d-mediated extravascular hemolysis occurred. In these patients, we found a significant correlation between mean ferritin increase per year, and both ARC (r = 0.737; P < 0.001; Suppl. Figure S2A) and C3d opsonization (r = 0.533; P = 0.011; Suppl. Figure S2B). Taken together, we showed that PNH patients on eculizumab indeed frequently develop hyperferritinemia. Moreover, we confirmed that the degree of C3d-mediated extravascular hemolysis is strongly associated with the development of iron accumulation in the RES in these patients, as evidenced by hyperferritinemia in the presence of normal TSAT.8–10 Subsequently, serum hepcidin and ERFE levels were determined (Figure 1B), and correlated with markers for hemolysis in both treated and untreated patients. Because there was a significant correlation between LDH and ARC in untreated patients (r = 0.587; P = 0.045; Suppl. Figure S3), and percentage of C3d-opsonized PNH erythrocytes and ARC in treated patients (r = 0.662; P = 0.001; Suppl. Figure S2C), for the rest of the analysis, ARC was used as marker for intravascular and extravascular hemolysis in untreated and treated PNH patients, respectively. Serum hepcidin levels were significantly higher in treated patients (median, 3.8 nM; range, 0.5–9.9 nM) compared with untreated patients (median, 1.0 nM; range, 0.5–7.9 nM; P = 0.001). To correct hepcidin levels for degree of body iron load, and thus to assess other modulators of hepcidin than body iron status, the hepcidin/ferritin ratio was calculated. There was no significant difference in hepcidin/ferritin ratios between the groups (P = 0.193). As reference intervals for ERFE are not available, serum of 10 healthy volunteers (Suppl. Table S3) was collected to compare ERFE levels of patients with those of healthy controls. Serum ERFE levels were significantly increased in both untreated (median, 8.3 ng/mL; range, 0.8–43.3 ng/mL) and treated patients (median, 8.9 ng/mL; range, 1.4–102.9 ng/mL) compared with healthy controls (median, 0.8 ng/mL; range, 0.2–27.5 ng/mL; P < 0.001 and P = 0.002, respectively) but did not significantly differ between the 2 patient groups (P = 0.610). In patients not treated with eculizumab, there was a significant correlation between ARC and both hepcidin/ferritin ratio (r = −0.670; P = 0.012) and ERFE (r = 0.587; P = 0.045; Figure 1C). Therefore, it is likely that untreated patients with intravascular hemolysis have suppressed hepcidin levels as a result of the combination of iron deficiency due to renal iron loss as well as increased ERFE production induced by enhanced erythropoiesis (Figure 2A). In line with Waheed et al,6 we postulated that hepcidin levels remain low relative to ferritin levels upon initiation of eculizumab because of continuous increased erythropoiesis with high iron demand in patients with ongoing C3d-mediated extravascular hemolysis. Indeed, ARC inversely correlated with hepcidin/ferritin ratio (r = −0.503; P = 0.017) and positively correlated with ERFE (r = 0.630; P = 0.002; Figure 1C). Based on these results, we hypothesize that in patients on eculizumab with ongoing extravascular hemolysis, both a decline of renal iron loss and erythropoiesis-mediated suppressed hepcidin levels contribute to a positive net iron balance and subsequent progressive iron deposition in the RES (Figure 2B).Figure 2.: Conceptual model of iron regulation in transfusion-independent untreated and eculizumab-treated patients with PNH. (A) Intravascular hemolysis in untreated PNH patients leads to supressed serum hepcidin levels as a result of iron deficiency due to urinary iron loss from hemosiderinuria as well as increased ERFE production induced by enhanced erythropoiesis. Low serum hepcidin levels promote duodenal absorption and iron release from macrophages of the RES in order to increase the iron availability for erythropoiesis. (B) Once intravascular hemolysis is blocked by the complement-C5 inhibitor eculizumab, urinary iron loss is inhibited. However, patients develop a variable degree of extravascular hemolysis, caused by phagocytosis of complement-C3d-opsonized PNH erythrocytes in the RES, leading to iron sequestration in macrophages. Because of a persistent enhanced erythropoiesis, ERFE production is increased, resulting in serum hepcidin levels that remain low relative to ferritin levels. The combination of both a decline of renal iron loss and erythropoiesis-mediated suppressed hepcidin levels contribute to a positive net iron balance and subsequent progressive iron deposition in the RES in patients on eculizumab with ongoing extravascular hemolysis. Figure created with BioRender.com. PNH = paroxysmal nocturnal hemoglobinuria; ERFE = erythroferrone; RES = reticuloendothelial system.The results of this study do not explain why TSAT remains low, which will limit parenchymal iron overload in hyperferritinemic PNH patients on eculizumab. This is in contrast to what is observed in patients with iron loading anemias due to an ineffective erythropoiesis, where hepcidin is suppressed as well (relative to body iron levels), but leads to severe hepatocyte iron overload.11 One possible explanation is that the degradation of C3d-opsonized erythrocytes takes place in the RES, where iron is directly sequestered in macrophages. Although hepcidin levels are relatively low compared with ferritin levels in patients with more prominent extravascular hemolysis, absolute hepcidin levels in patients on eculizumab are elevated compared with untreated patients and might be not low enough to allow sufficient active ferroportin-mediated cellular iron efflux to compensate for the higher RES influx of iron. An alternative explanation for stable nonincreasing TSATs might be that macrophage iron release is partially impaired independent from the hepcidin-ferroportin axis. Theurl et al12 showed in mice that during massive hemolysis, the Kupffer-cell population in the liver is overwhelmed and these cells die. To compensate, blood-derived monocytes fill the vacant niche in the liver and differentiate into Kupffer-cell like macrophages. Because blood-derived monocytes from PNH patients lack glycosylphosphatidylinositol (GPI)-anchors, these Kuppfer-cell like macrophages are deficient of GPI-anchored proteins. A study of de Domenico et al13 showed that a GPI-linked splice variant of ceruloplasmin might be important for cellular iron export by stabilizing ferroportin on the cell membrane. As GPI-anchor deficient PNH cells lack GPI-linked ceruloplasmin, it is conceivable that iron release from GPI-anchor deficient Kupffer-like cells is impaired, leading to iron deposition in these macrophages. Future research is warranted to study this hypothesis. In conclusion, based on the results of this observational study, we postulate that in transfusion-independent PNH patients on eculizumab, the combination of a decline of renal iron loss as well as the emergence of extravascular hemolysis leading to increased RES-iron influx and erythropoiesis-mediated suppressed hepcidin contribute to progressive iron deposition in the RES. Long-term follow-up of serum iron parameters and organ iron quantification by MRI during therapy with terminal complement inhibitors is warranted to assess whether iron loading of the RES will eventually result in redistribution with toxic parenchymal iron overload, or that iron accumulation in the RES finally reaches a plateau due to further increased hepcidin levels. Given the findings in transfusion-independent patients on eculizumab, physicians should be even more aware of the development of iron overload in transfusion-dependent patients. Future studies may investigate whether proximal complement inhibitors, which prevent C3d-mediated extravascular hemolysis, also prevent the development of RES-iron accumulation.14 AUTHOR CONTRIBUTIONS CS, SS, DS, and SL designed the study. CS, FP, EJ, and CL acquired the data, conducted experiments, and performed data analysis. CS, SS, JJ, NB, DS, and SL wrote the article. JJ, NB, DS, and SL supervised the study. DATA AVAILABILITY Relevant individual patient data that support the findings of this study are available in the supplementary digital content (Suppl. Table S2). Remaining data are available on request from the corresponding author. DISCLOSURES The authors have no conflicts of interest to disclose. SOURCES OF FUNDING The authors declare no sources of funding.

[Myasthenia in adults, children, and adolescents: what's new?]

Therapy of myasthenia gravis (MG) is increasingly oriented to the patient's antibody status. In addition to symptomatic therapy, steroids, classic long-term immunosuppressive therapies and thymectomy are regularly used. In recent years, new therapeutic approaches have been developed that particularly benefit acetylcholine receptor (AChR) antibody (Abs) positive patients with highly active disease. While the C5 complement inhibitor eculizumab was reserved for treatment-refractory generalized courses of AChR-Abs positive MG, two new drugs, the neonatal Fc receptor inhibitor efgartigimod and the more advanced C5 complement inhibitor ravulizumab, have recently been approved as add-on therapy for AChR-Abs positive generalized MG (gMG). In highly active courses of MG with Abs against the muscle-specific receptor tyrosine kinase (MuSK), the use of rituximab should be considered early in the course of the disease. The efficacy of the new drugs in children and adolescents with juvenile MG (JMG) is currently being tested in clinical trials. The new guideline recommends the use of modern immunomodulators based on astep-by-step approach depending on disease activity. With the German Myasthenia Register (MyaReg), the changing therapeutic landscape and quality of life of patients with myasthenic syndromes can be assessed, thus providing real-world data on the care of MG patients. Despite treatment based on the previous guideline, many MG patients suffer considerable impairment to their quality of life. With the new immunomodulators, there is the possibility of early intensified immunotherapy, which, in contrast to long-term immunosuppressants, can lead to arapid improvement in the course of the disease.

[Japanese patient preferences between ravulizumab and eculizumab for the treatment of paroxysmal nocturnal hemoglobinuria].

Ravulizumab is the first long-acting complement inhibitor approved for paroxysmal nocturnal hemoglobinuria (PNH) treatment. We evaluated patient preference for ravulizumab or eculizumab among Japanese adults with PNH. The ALXN1210-PNH-301 (NCT02946463) and ALXN1210-PNH-302 (NCT03056040) studies included 23 Japanese adults who are enrolled in complement inhibitor treatment-naive and eculizumab (≥6 months) treatment. Patient preference was assessed using the PNH-specific patient preference questionnaire (PNH-PPQ©). Most patients preferred ravulizumab (19/23, 82.6%), none preferred eculizumab, and four (17.4%) reported no preference (χ2 test, p<0.005). The preference for ravulizumab was driven by its lower infusion frequency (every 8 weeks) compared with eculizumab (every 2 weeks). The included Japanese patients with PNH preferred ravulizumab because of its reduced infusion frequency, which increases activity planning ability, treatment convenience, and overall quality of life, as compared with eculizumab. These data provide useful insight into patient perspectives and may aid decision-making for PNH treatment.

Complement Activation Is Associated with Endothelial Damage in Hematopoietic Stem Cell Transplant Associated-Thrombotic Microangiopathy

Introduction: Hematopoietic stem cell transplant-associated thrombotic microangiopathy (HSCT-TMA) is a life-threatening complication of HSCT. Identification of at-risk patients is challenging, leading to delays in diagnosis and poor outcomes. Degradation of the glycocalyx and dysregulated complement activation are integral to the pathophysiology. The glycocalyx components thrombomodulin (TM) and syndecan-1 (SYND1) are shed during cell damage, and detection in patient plasma may serve as biomarkers of endothelial cell (EC) dysfunction. Therapeutic intervention to preserve glycocalyx integrity may protect the endothelium and also improve the clinical outcome during HSCT-TMA. Additionally, plasma Ba, an alternative complement pathway (AP) activation product, has been identified as a prognostic biomarker of HSCT-TMA. Our objective was to explore the link between excessive AP activation and endothelial damage in the context of HSCT-TMA and to potentially identify biomarkers to aid in its diagnosis. Methods: Biomarker levels of soluble TM, SYND1, and Ba were measured in plasma of pediatric HSCT patients with and without (controls) TMA obtained from Texas Children's Hospital. Sample acquisition was approved by Baylor College of Medicine Institutional Review Board. Biomarkers were also measured in a pre-clinical in vivo model of inflammation-mediated complement activation similar to HSCT-TMA, in which C57BL/6J mice were injected with lipopolysaccharide (LPS) to induce complement activation, followed by treatment with AP (anti-fB IgG) and terminal complement pathway (anti-C5 IgG) inhibitors or an IgG isotype control. Finally, as the immunosuppressant cyclosporin A (CsA) is a known trigger of HSCT-TMA, the role of complement in CsA-mediated damage in human ECs (HMEC-1 cells and HUVECs) was assessed in vitro. ECs were incubated with CsA followed by normal human serum (NHS) in the presence or absence of the C5 complement inhibitor eculizumab. TM was then measured by fluorescent staining on the cell surface and quantified using mean fluorescence intensity (MFI). Results: HSCT-TMA patients (n=11), compared to HSCT control patients (n=7), had significantly elevated levels of biomarkers of glycocalyx damage (TM: 18.3 ± 10.9 ng/mL and 6.6 ± 2.9 ng/mL, respectively; P<0.01; SYND1: 175.3 ± 177.0 ng/mL and 35.8 ± 18.9, respectively; P<0.05). A strong positive correlation between TM and SYND1 was observed (Pearson r=0.89). Plasma Ba was also significantly elevated in patients with TMA compared to those without (1790.0 ± 1262.0 ng/mL and 652.1 ± 233.5 ng/mL, respectively; P<0.05), and correlated positively with both TM and SYND1 levels (Pearson r=0.72 and 0.50, respectively). We have previously shown in an in vivo model of inflammation-mediated complement activation that LPS-injected mice, compared to saline-injected control mice, had significantly increased plasma Ba levels. Here we demonstrated LPS-injected mice (which also received IgG isotype control) had higher circulating levels of TM than untreated mice (35.1 ± 5.8 ng/mL [n=6] and 10.9 ± 1.6 ng/mL [n=6], respectively; P<0.0001). Inhibition of alternative (anti-fB IgG) and terminal (anti-C5 IgG) pathways of complement significantly attenuated TM levels (compared to isotype control [35.1 ± 5.8 ng/mL]; anti-FB: 25.2 ± 5.3 ng/mL, P<0.01; anti-C5: 26.2 ± 4.9 ng/mL, P<0.05, Fig. 1). TM was positively correlated with Ba (Pearson r=0.68). In vitro treatment of HMEC-1 cells with CsA led to deposition of iC3b and C5b-9, and C5 inhibition with eculizumab significantly reduced C5b-9 deposition (P< 0.0001) but had no effect on iC3b deposition. Treatment of HUVECs with CsA also reduced surface expression of TM (P<0.0001), and TM loss was partially restored by eculizumab (P<0.05, Fig 2). Conclusion: Plasma biomarkers of endothelial damage were elevated in patients with HSCT-TMA and in mice with inflammatory-mediated complement activation. Furthermore, AP activation positively correlated with biomarkers of endothelial damage. Blockade of complement activation significantly reduced markers of endothelial damage in both in vivo and in vitro models. These results provide further evidence linking complement activation and endothelial damage in HSCT-TMA and suggest that the use of these biomarkers may aid in the diagnosis of HSCT-TMA. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Trial in Progress: An Open-Label, Phase 2 Study to Evaluate the Safety, Tolerability, Pharmacokinetics, Pharmacodynamics, and Efficacy of KP104 in Complement Inhibitor-Naïve Subjects with Paroxysmal Nocturnal Hemoglobinuria

Background: Paroxysmal nocturnal hemoglobinuria (PNH) is a life-threatening disease characterized by destruction of red blood cells by the complement system, leading to pathologies such as anemia and thrombosis. Currently approved complement inhibitors target C5 which addresses primarily intravascular hemolysis (IVH). However, many treated patients are still anemic and transfusion dependent since C5 inhibitors cannot treat extravascular hemolysis (EVH), which is driven by the alternative pathway (AP). C3 inhibitors need frequent administration, high dosage, and are associated with breakthrough hemolysis (BTH) (Hillmen, 2021; Rother, 2007; Stern, 2019; Rosario, 2022). Thus, the treatment of PNH still remains a challenge with significant unmet medical needs to develop more efficacious and convenient complement drugs. KP104 is a bi-functional complement inhibitor that can inhibit both C5 and C3 convertase activities and thereby achieve high potency in treating complement mediated pathologies. KP104 is an engineered anti-C5 immunoglobulin G4 monoclonal antibody (mAb) fused with the N-terminal 5 short consensus repeats of human factor H (a potent AP inhibitor) and engineered to extend serum half-life. KP104 was generally well tolerated and safe in the First-in-Human (FIH), healthy volunteer Phase 1 trial (n=66). PD data from this FIH study also support the dual mechanisms of KP104 inhibiting both AP and terminal pathway (TP). In addition, an extended half-life for KP104 has been observed in healthy volunteers, compared to other approved bispecific/fusion proteins on the market. Details of the FIH study will be published at another major conference (Wabinitz, 2022). KP104 is being developed for multiple diseases with complement cascade dysregulation, with PNH being the first indication to be investigated. Study Design and Methods: This is an open-label, 2-part, Phase 2 study to evaluate safety, tolerability, PK, PD, and efficacy of KP104 in complement inhibitor-naïve subjects with PNH (NCT05476887). Approximately 35 subjects with PNH are planned to be enrolled, including up to 18 in the dose-ranging Part 1, and up to 17 in the proof-of-concept (POC) Part 2. The primary objectives of Part 1 are to assess safety and tolerability and estimate optimal biologic dose (OBD) and regimen of KP104 in complement inhibitor-naïve subjects with PNH. Part 1 will include up to 3 cohorts of 3 to 6 subjects/cohort dosed for 12 weeks (Figure 1). When the third subject in the last cohort of Part 1 completes 4 weeks of treatment, a KP104 OBD will be estimated for evaluation in Part 2. Part 2 is to confirm POC by studying the KP104 OBD in 1 cohort of complement inhibitor-naïve subjects with PNH (Figure 1). The primary efficacy endpoint is the proportion of subjects with a ≥2 g/dL increase in hemoglobin from baseline to the end of the treatment period, with the absence of transfusion through the treatment period. The percent of subjects showing an increase from baseline in hemoglobin of ≥2 g/dL at the end of the treatment period will be compared to a 15% reference rate using an exact binomial one-sample test. The sample size was calculated to achieve approximately 90% power with 0.025 type 1 error rate (one-sided). In summary, KP104, through effective inhibition of both AP and TP complement pathways, may achieve high potency and address IVH, EVH, and BTH for treating subjects with PNH. Hillmen P, Szer J, et al. 2021. Pegcetacoplan versus eculizumab in paroxysmal nocturnal hemoglobinuria. N Engl J Med 384:1028-1037. Rosario N, Lucio L. 2022. Breakthrough Hemolysis in PNH with Proximal or Terminal Complement Inhibition. N Engl J Med 387(2):160-166. Rother, R.P., et al. 2007. Discovery and development of the complement inhibitor eculizumab for the treatment of paroxysmal nocturnal hemoglobinuria. Nat Biotechnol 25:1256-1264. Stern, R.M., and Connell, N.T. 2019. Ravulizumab: a novel C5 inhibitor for the treatment of paroxysmal nocturnal hemoglobinuria. Ther Adv Hematol 10:2040620719874728. Wabinitz, P., et al. 2022. SYNERGY-1: A Phase 1, first-in-human, randomized, double-blind, placebo-controlled safety, tolerability, immunogenicity, PK and PD study of KP104 in escalating single and multiple doses. ASN abstract. Under review. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Clinical Utility and Potential Cost Savings of Pharmacologic Monitoring of Eculizumab for Complement-Mediated Thrombotic Microangiopathy.

One of the treatment options for complement-mediated thrombotic microangiopathy (CM-TMA), also known as atypical hemolytic uremic syndrome, is the administration of the C5 complement inhibitor eculizumab. In vivo studies have reported a complete complement blockade with eculizumab serum concentrations above 50 μg/mL in the case of atypical hemolytic uremic syndrome. The eculizumab trough levels and C5 functional activity were monitored in patients with CM-TMA being treated with eculizumab. For those with eculizumab trough concentrations of more than 100 μg/mL, the frequency of eculizumab 1200-mg doses was decreased. In this article, we describe the pharmacologic monitoring data with the use of C5 functional activity and mass spectrometric assessments of eculizumab to allow for a tailored eculizumab schedule for 10 patients with CM-TMA. In 9 out of 10 (90%) patients with a standard administration schedule, eculizumab trough concentrations were more than 100 μg/mL. At the time of the last eculizumab follow-up (median, 250 days; range, 85-898 days), the interval between eculizumab infusions was extended to every 3-6 weeks for 8 patients; no disease relapse was found with the modified dosing interval. Altering the administration of maintenance eculizumab from every 2-3 weeks to 3-6 weeks yields a savings of $78,185 per patient for a 6-month eculizumab treatment course. Although larger standardized cohorts are necessary to confirm these findings, our data suggest that monitoring eculizumab levels in conjunction with C5 assessment allows for safe modification of eculizumab dosing and results in considerable cost savings.

CD55-deficiency in Jews of Bukharan descent is caused by the Cromer blood type Dr(a-) variant.

The complement system regulator CD55 was initially found to carry the Cromer blood group system antigens, and its complete loss of function was subsequently revealed to cause a severe monogenic gastrointestinal syndrome characterized by protein-losing enteropathy and susceptibility to venous thrombosis. Here we present homozygosity to the CD55 c.596C>T; p.Ser199Leu variant, which was previously described as the Cromer Dr(a−) genotype, in two Bukharan Jewish CD55-deficiency patients with variable disease severity. We confirm that this missense variant causes aberrant splicing and deletion of 44 bp in exon 5, leading to premature termination and low expression of the CD55 protein. Furthermore, Patient 1 exhibited a mildly abnormal B cell immunophenotyping profile. By population screening we established that this variant is highly prevalent in the Bukharan Jewish population, with a carrier frequency of 1:17, suggesting that many similar patients are un- or mis-diagnosed. The phenotypic variability, ranging from abdominal pain when eating a high-fat diet to the full CD55-deficiency phenotype, is likely related to modifiers affecting the proportion of the variant that is able to escape aberrant splicing. Establishing the diagnosis of CD55-deficiency in a timely manner, even in patients with milder symptoms, may have a critical effect on their management and quality-of-life since treatment with the complement inhibitor eculizumab is highly effective in ameliorating disease manifestations. Awareness of founder mutations within certain populations can further guide genetic testing and prevent a diagnostic odyssey, by placing this CD55 variant high on the differential diagnosis.

Thrombotic microangiopathy after kidney transplantation: Analysis of the Brazilian Atypical Hemolytic Uremic Syndrome cohort.

Atypical Hemolytic Uremic Syndrome (aHUS) is an ultra-rare disease that potentially leads to kidney graft failure due to ongoing Thrombotic Microangiopathy (TMA). The aim was evaluating the frequency of TMA after kidney transplantation in patients with aHUS in a Brazilian cohort stratified by the use of the specific complement-inhibitor eculizumab. This was a multicenter retrospective cohort study including kidney transplant patients diagnosed with aHUS. We collected data from 118 transplant centers in Brazil concerning aHUS transplanted patients between 01/01/2007 and 12/31/2019. Patients were stratified into three groups: no use of eculizumab (No Eculizumab Group), use of eculizumab for treatment of after transplantation TMA (Therapeutic Group), and use of eculizumab for prophylaxis of aHUS recurrence (Prophylactic Group). Thirty-eight patients with aHUS who received kidney transplantation were enrolled in the study. Patients' mean age was 30 years (24-40), and the majority of participants was women (63% of cases). In the No Eculizumab Group (n = 11), there was a 91% graft loss due to the TMA. The hazard ratio of TMA graft loss was 0.07 [0.01-0.55], p = 0.012 in the eculizumab Prophylactic Group and 0.04 [0.00-0.28], p = 0.002 in the eculizumab Therapeutic Group. The TMA graft loss in the absence of a specific complement-inhibitor was higher among the Brazilian cohort of kidney transplant patients. This finding reinforces the need of eculizumab use for treatment of aHUS kidney transplant patients. Cost optimization analysis and the early access to C5 inhibitors are suggested, especially in low-medium income countries.

PRO77 Preliminary Characterization of Eculizumab Treatment Patterns, Preceding Disease Triggers and Supportive Therapies in Atypical Hemolytic Uremic Syndrome: A US Claims Database Analysis

Patients with atypical hemolytic uremic syndrome (aHUS) may require ongoing treatment of varying duration. The C5 complement inhibitor eculizumab provides transformative benefits in aHUS; however, knowledge gaps remain regarding treatment patterns/preferences. To address this, we sought to characterize real-world eculizumab use, disease triggers, dialysis and plasma exchange/infusion (PE/PI) in patients with aHUS using US claims data.

Discontinuation of Complement-Inhibitor Therapy in Patients with Atypical Hemolytic Uremic Syndrome

The terminal complement inhibitor eculizumab has improved the outlook for patients with atypical hemolytic uremic syndrome (aHUS), especially with

The use of eculizumab in Capnocytophaga canimorsus associated thrombotic microangiopathy: a case report

BackgroundThe use of complement inhibition is well established for complement mediated thrombotic microangiopathy, but its role in secondary forms of thrombotic microangiopathy is debated. We here present a case of thrombotic microangiopathy triggered by Capnocytophaga canimorsus, illustrating the diagnostic difficulties in discriminating between different thrombotic microangiopathies, and the dilemmas regarding how to treat this disease entity.Case presentationA previously healthy 56-year-old woman presented with fever and confusion. She was diagnosed with sepsis from Capnocytophaga canimorsus and thrombotic microangiopathy. Marked activation of both T-cells, endothelium and complement were documented. She was successfully treated with antimicrobial therapy, the complement inhibitor eculizumab and splenectomy. After several weeks, a heterozygote variant in complement factor B was localized, potentially implying the diagnosis of a complement mediated TMA over an isolated infection related TMA.ConclusionsWe discuss the possible interactions between complement activation and other findings in severe infection and argue that complement inhibition proved beneficial to this patient’s rapid recovery.

Two cases of carfilzomib\u2010induced thrombotic microangiopathy successfully treated with Eculizumab in multiple myeloma

BackgroundTreatment with proteasome inhibitors like carfilzomib in patients with multiple myeloma (MM) can induce thrombotic microangiopathy (TMA) characterized by neurological symptoms, acute kidney injury, hemolysis and thrombocytopenia. Successful treatment with the monoclonal antibody eculizumab was described for these patients, but reports of ideal management and definitive treatment protocols are lacking.Case PresentationThe first case describes a 43-years-old IgG-kappa-MM patient that developed TMA during the first course of carfilzomib-lenalidomide-dexamethasone (KRd) consolidation after autologous stem cell transplantation (ASCT). In the second case, a 59-years-old IgG-kappa-MM patient showed late-onset TMA during the fourth and last cycle of elotuzumab-KRd consolidation within the DSMM XVII study of the German study group MM (DSMM; clinicalTrials.gov Identifier: NCT03948035). Concurrently, he suffered from influenza A/B infection. Both patients had a high TMA-index for a poor prognosis of TMA. Therapeutically, in both patients plasma exchange (TPE) was initiated as soon as TMA was diagnosed. In patient #1, dialysis became necessary. For both patients, only when the complement inhibitor eculizumab was administered, kidney function and blood values impressively improved.ConclusionIn this small case series, two patients with MM developed TMA due to carfilzomib treatment (CFZ-TMA), the second patient as a late-onset form. Even though TMA could have been elicited by influenza in the second patient and occurred after ASCT in both patients, with cases of TMA post-transplantation in MM being described, a relation of TMA and carfilzomib treatment was most likely. In both patients, treatment with eculizumab over two months efficiently treated TMA without recurrence and with both patients remaining responsive months after TMA onset. Taken together, we describe two cases of TMA in MM patients on carfilzomib-combination treatment, showing similar courses of this severe adverse reaction, with good responses to two months of eculizumab treatment.

Complement inhibitor for therapy of CHAPLE.

A new study shows successful immunotherapy of a detrimental gastrointestinal disease using the complement inhibitor eculizumab.

Benefits of eculizumab in AQP4+ neuromyelitis optica spectrum disorder: Subgroup analyses of the randomized controlled phase 3 PREVENT trial

BackgroundAntibodies to the aquaporin-4 (AQP4) water channel in neuromyelitis optica spectrum disorder (NMOSD) are reported to trigger the complement cascade, which is implicated in astrocyte damage and subsequent neuronal injury. The PREVENT study demonstrated that the terminal complement inhibitor eculizumab reduces adjudicated relapse risk in patients with anti-AQP4 immunoglobulin G-positive (AQP4+) NMOSD. The objective of this analysis was to evaluate the efficacy of eculizumab in reducing relapse risk and its safety in AQP4+ NMOSD across clinically relevant subgroups in PREVENT. MethodsIn the randomized, double-blind, time-to-event, phase 3 PREVENT trial, 143 adults received eculizumab (maintenance dose, 1200 mg/2 weeks) or placebo (2:1), with stable-dose concomitant immunosuppressive therapy (IST) permitted (except rituximab and mitoxantrone). Post hoc analyses of relapses and adverse events were performed for prespecified and post hoc subgroups based on concomitant IST and prior rituximab use, demographic and disease characteristics, and autoimmune comorbidity. ResultsThe significant reduction in relapse risk observed for eculizumab versus placebo in the overall PREVENT population was consistently maintained across subgroups based on concomitant IST and previous rituximab use, age, sex, region, race, time since clinical onset of NMOSD, historical annualized relapse rate, baseline Expanded Disability Status Scale score, and history of another autoimmune disorder. The serious infection rate was lower with eculizumab than placebo regardless of rituximab use in the previous year, concomitant IST use, or history of another autoimmune disorder. ConclusionAcross a wide range of clinically relevant AQP4+ NMOSD patient subgroups in PREVENT, eculizumab therapy was consistently effective versus placebo in reducing relapse risk, with no apparent increase in serious infection rate. Trial registrationNCT01892345 (ClinicalTrials.gov).

Satralizumab in the treatment of neuromyelitis optica spectrum disorder.

Neuromyelitis optica spectrum disorder (NMOSD) is a rare and debilitating autoimmune astrocytopathy with apredominantly relapsing disease course. Satralizumab, a humanized monoclonal antibody, was designed to treat NMOSD by targeting the IL-6 receptor. Satralizumab builds on positive experiences of off-label usetocilizumab in recentyears. Before 2019, no medications were approved for the treatment of NMOSD. In 2020, satralizumab became the third compound to enter the US market, adding to the complement inhibitor eculizumab and the CD19 inhibitor inebilizumab. Here, we review the two randomized, double-blind, Phase III trials that investigated the subcutaneous administration of satralizumab as add-on treatment and monotherapy. Both studies revealed positive effects concerning the reduction of relapse risk for AQP4seropositive NMOSD patients and generally good tolerability.

Incomplete Complement Inhibition in Patients with PNH on Eculizumab - 5 Year Experience from the National PNH Service Leeds

Background Paroxysmal Nocturnal Hemoglobinuria (PNH) is a rare acquired disorder characterised by intravascular hemolysis and thrombosis. Patients with symptomatic PNH are commenced on the complement inhibitor eculizumab (600mg weekly for 5 weeks then 900mg 2 weekly). This monoclonal antibody targets C5 in the complement cascade, halting terminal complement activation thus inhibiting intravascular hemolysis. In some patients intravascular hemolysis is not adequately controlled on the standard regimen. Patient symptoms, transfusion requirements and raised Lactate dehydrogenase (LDH) levels are indicators for suboptimal control of PNH and review of eculizumab dosing. The 50% hemolytic complement (CH50) test is a functional assay assessing capability of serum complement components of the classical pathway to lyse sheep red blood cells pre-coated with rabbit anti-sheep red blood cell antibody. Patients with complement inhibited PNH should demonstrate absent lysis. As the test is expensive and difficult to organise, we tested if incomplete complete blockade as determined by CH50 activity would be better to confirm under-dosing than LDH value. Methods The Leeds (UK) PNH National Service reviewed patients who underwent CH50 assay between January 2015 and March 2020. All patients were on eculizumab with clinical concerns regarding suboptimal control of PNH. Patients receive eculizumab infusions intravenously every 14 days and routine follow up from the PNH Service. Serum samples were obtained 24 hours prior to infusions for CH50 assay; LDH values were routinely collected. Complete complement blockade was defined by &amp;lt;10% CH50 activity; intravascular hemolysis was indicated by LDH value &amp;gt;1.5x upper limit of normal (ULN). Confidence intervals were set at 95% and significance set at p&amp;lt;0.05. Results In the study period, 327 tests (median 2, range 1 - 8) were carried out in 146 patients (median age 54 years, range 16 - 89; 74 female). 81% (265) were successful; 19% (62) were unsuccessful due to processing errors. Of the successful tests, 74% (197 in 127 patients) indicated complete complement blockade and 26% (68 in 38 patients) indicated incomplete blockade. Of the patients with incomplete blockade, 68% (26) demonstrated complete blockade on repeat testing and 32% (12) had their eculizumab dose increased. Clinical symptoms of under-dosing in the 12 patients requiring a dose increase included increased transfusion requirements and/or breakthrough hemolysis (7), pregnancy (2; both returned to 900mg post pregnancy) and significant lethargy (3). Of the patients requiring a dose increase, 3 were on 1200mg before 2015; their dose was increased to 1500mg. Repeat testing was carried out in 10/12 patients after dose increase; 8 indicated complete blockade; 2 patients were incompletely blocked at 1200mg and received a further dose increase to 1500mg. Further testing indicated complete blockade in 1 patient; 1 required a 3rd dose increase to 1800mg due to incomplete blockade and ongoing transfusion requirement. Corresponding LDH values were analysed; median LDH for the complete blockade group was 1.16xULN (range 0.54 - 2.16) and 1.28xULN (range 0.76 - 2.38) for the incomplete blockade group. LDH values were not significantly higher in the incomplete blockade group compared to the complete blockade group, p=0.08. There was no significant difference in LDH values pre- and post-dose increase, p=0.38 (Figure 1); median pre-dose increase LDH 1.14xULN; median post-dose increase LDH 1.13xULN. Correlation coefficient shows that CH50 activity was positively correlated with LDH value, r(123)=0.18, p=0.04. Conclusion We report the effective utilisation of CH50 analysis where there is clinical concern of suboptimal control of PNH. All patients demonstrating hemolytic activity on CH50 assays indicated subsequent complement blockade following increase of eculizumab dose. Increasing eculizumab is costly requiring robust evidence of suboptimal complement inhibition; a positive correlation between CH50 activity and LDH values was shown however this is not sufficient to guide clinical decisions. LDH values of the incomplete blockade group were not significantly higher than those with complete blockade, suggesting the use of LDH values as an assessment of complement inhibition in patients with ongoing symptoms or transfusion requirements is not sufficient to guide eculizumab dose increases. Disclosures Munir: Alexion: Honoraria; F. Hoffmann-La Roche: Consultancy, Other: Medical writing support, furnished by Scott Battle, PhD, of Health Interactions, was funded by F. Hoffmann-La Roche Ltd, Basel, Switzerland. Pike:Apellis: Research Funding. Arnold:Alexion Pharmaceuticals: Honoraria. Hillmen:AstraZeneca: Consultancy, Speakers Bureau; Alexion: Consultancy, Research Funding, Speakers Bureau; Acerta: Other: Financial or material support; Roche: Consultancy, Other: Financial or material support, Research Funding, Speakers Bureau; AbbVie: Consultancy, Other: Financial or material support, Research Funding, Speakers Bureau; Pharmacyclics: Other: Financial or material support, Research Funding; Janssen: Consultancy, Other: Financial or material support, Research Funding, Speakers Bureau; Apellis: Consultancy, Research Funding, Speakers Bureau; Gilead: Other: Financial or material support, Research Funding. Griffin:Alexion Pharmaceuticals: Honoraria, Other: Conference Support; Biocryst: Membership on an entity's Board of Directors or advisory committees.

Pregnancy in Classical Paroxysmal Nocturnal Hemoglobinuria and Aplastic Anemia-Paroxysmal Nocturnal Hemoglobinuria: A High-Risk Constellation.

Pregnancies in paroxysmal nocturnal hemoglobinuria (PNH) are associated with increased morbidity and mortality. Retrospective studies suggest that outcome has improved with the advent of the complement inhibitor eculizumab. To substantiate this assumption we analyzed the data from patients treated in our department since 2009. All patients were included in the International PNH registry and followed prospectively. We identified 16 pregnancies in 9 patients with classical PNH, and two pregnancies in two patients with aplastic anemia (AA)-PNH. In classical PNH, 13 pregnancies were supported by eculizumab. Breakthrough hemolysis occurred in six pregnancies, necessitating an increase in the biweekly eculizumab dose from 900 mg to 1,200–1,800 mg. Red blood cell transfusions were given in six and platelet transfusions in two pregnancies. A Budd-Chiari syndrome and cholecystitis complicated the course of two pregnancies. Four of 13 pregnancies supported by eculizumab ended in spontaneous abortion or stillbirth, and one was prematurely terminated because of fetal trisomy 21. None of the three pregnancies not supported by eculizumab had a successful outcome. Half the deliveries were preterm. None of the patients died, and, in all but one patient, the post-partum period was uneventful. Both pregnancies in patients with AA-PNH took a favorable course. Our results confirm low maternal mortality and frequent breakthrough hemolysis in pregnant PNH patients receiving eculizumab. Fetal mortality and the rate of preterm delivery were higher than reported previously, possibly related to the use of registry data that are likely to reduce the risk of publication and recall biases.