Crizanlizumab for the Prevention of Pain Crises in Sickle Cell Disease.

BACKGROUND: The up-regulation of P-selectin in endothelial cells and platelets contributes to the cell-cell interactions that are involved in the pathogenesis of vaso-occlusion and sickle cell-related pain crises. The safety and efficacy of crizanlizumab, an antibody against the adhesion molecule P-selectin, were evaluated in patients with sickle cell disease. METHODS: In this double-blind, randomized, placebo-controlled, phase 2 trial, we assigned patients to receive low-dose crizanlizumab (2.5 mg per kilogram of body weight), high-dose crizanlizumab (5.0 mg per kilogram), or placebo, administered intravenously 14 times over a period of 52 weeks. Patients who were receiving concomitant hydroxyurea as well as those not receiving hydroxyurea were included in the study. The primary end point was the annual rate of sickle cell-related pain crises with high-dose crizanlizumab versus placebo. The annual rate of days hospitalized, the times to first and second crises, annual rates of uncomplicated crises (defined as crises other than the acute chest syndrome, hepatic sequestration, splenic sequestration, or priapism) and the acute chest syndrome, and patient-reported outcomes were also assessed. RESULTS: A total of 198 patients underwent randomization at 60 sites. The median rate of crises per year was 1.63 with high-dose crizanlizumab versus 2.98 with placebo (indicating a 45.3% lower rate with high-dose crizanlizumab, P=0.01). The median time to the first crisis was significantly longer with high-dose crizanlizumab than with placebo (4.07 vs. 1.38 months, P=0.001), as was the median time to the second crisis (10.32 vs. 5.09 months, P=0.02). The median rate of uncomplicated crises per year was 1.08 with high-dose crizanlizumab, as compared with 2.91 with placebo (indicating a 62.9% lower rate with high-dose crizanlizumab, P=0.02). Adverse events that occurred in 10% or more of the patients in either active-treatment group and at a frequency that was at least twice as high as that in the placebo group were arthralgia, diarrhea, pruritus, vomiting, and chest pain. CONCLUSIONS: In patients with sickle cell disease, crizanlizumab therapy resulted in a significantly lower rate of sickle cell-related pain crises than placebo and was associated with a low incidence of adverse events. (Funded by Selexys Pharmaceuticals and others; SUSTAIN ClinicalTrials.gov number, NCT01895361 .).

Long-term effect of the complement inhibitor eculizumab on kidney function in patients with paroxysmal nocturnal hemoglobinuria.

Paroxysmal nocturnal hemoglobinuria (PNH) is a debilitating and life-threatening disease in which lysis of PNH red blood cells frequently manifests with chronic hemolysis, anemia, and thrombosis. Renal damage in PNH is associated with chronic hemosiderosis and/or microvascular thrombosis. We determined the incidence of renal dysfunction or damage, defined by stages of chronic kidney disease (CKD), in a large cohort of PNH patients and evaluated the safety and efficacy of the complement inhibitor eculizumab in altering its progression. Renal dysfunction or damage was observed in 65% of the study population at baseline with 21% of patients with later stage CKD or kidney failure (glomerular filtration rate [GFR]

Anti-GD1a antibodies activate complement and calpain to injure distal motor nodes of Ranvier in mice.

The motor axonal variant of Guillain-Barré syndrome is associated with anti-GD1a immunoglobulin antibodies, which are believed to be the pathogenic factor. In previous studies we have demonstrated the motor terminal to be a vulnerable site. Here we show both in vivo and ex vivo, that nodes of Ranvier in intramuscular motor nerve bundles are also targeted by anti-GD1a antibody in a gradient-dependent manner, with greatest vulnerability at distal nodes. Complement deposition is associated with prominent nodal injury as monitored with electrophysiological recordings and fluorescence microscopy. Complete loss of nodal protein staining, including voltage-gated sodium channels and ankyrin G, occurs and is completely protected by both complement and calpain inhibition, although the latter provides no protection against electrophysiological dysfunction. In ex vivo motor and sensory nerve trunk preparations, antibody deposits are only observed in experimentally desheathed nerves, which are thereby rendered susceptible to complement-dependent morphological disruption, nodal protein loss and reduced electrical activity of the axon. These studies provide a detailed mechanism by which loss of axonal conduction can occur in a distal dominant pattern as observed in a proportion of patients with motor axonal Guillain-Barré syndrome, and also provide an explanation for the occurrence of rapid recovery from complete paralysis and electrophysiological in-excitability. The study also identifies therapeutic approaches in which nodal architecture can be preserved.

Effect of eculizumab on haemolysis-associated nitric oxide depletion, dyspnoea, and measures of pulmonary hypertension in patients with paroxysmal nocturnal haemoglobinuria.

Pulmonary hypertension (PH) is a common complication of haemolytic anaemia. Intravascular haemolysis leads to nitric oxide (NO) depletion, endothelial and smooth muscle dysregulation, and vasculopathy, characterized by progressive hypertension. PH has been reported in patients with paroxysmal nocturnal haemoglobinuria (PNH), a life-threatening haemolytic disease. We explored the relationship between haemolysis, systemic NO, arginine catabolism and measures of PH in 73 PNH patients enrolled in the placebo-controlled TRIUMPH (Transfusion Reduction Efficacy and Safety Clinical Investigation Using Eculizumab in Paroxysmal Nocturnal Haemoglobinuria) study. At baseline, intravascular haemolysis was associated with elevated NO consumption (P < 0.0001) and arginase-1 release (P < 0.0001). Almost half of the patients in the trial had elevated levels (> or =160 pg/ml) of N-terminal pro-brain natriuretic peptide (NT-proBNP), a marker of pulmonary vascular resistance and right ventricular dysfunction previously shown to indicate PH. Eculizumab treatment significantly reduced haemolysis (P < 0.001), NO depletion (P < 0.001), vasomotor tone (P < 0.05), dyspnoea (P = 0.006) and resulted in a 50% reduction in the proportion of patients with elevated NT-proBNP (P < 0.001) within 2 weeks of treatment. Importantly, the significant improvements in dyspnoea and NT-proBNP levels occurred without significant changes in anaemia. These data demonstrated that intravascular haemolysis in PNH produces a state of NO catabolism leading to signs of PH, including elevated NT pro-BNP and dyspnoea that are significantly improved by treatment with eculizumab.

Eculizumab prevents intravascular hemolysis in patients with paroxysmal nocturnal hemoglobinuria and unmasks low-level extravascular hemolysis occurring through C3 opsonization.

BACKGROUND: Paroxysmal nocturnal hemoglobinuria is an acquired hemolytic anemia characterized by intravascular hemolysis which has been demonstrated to be effectively controlled with eculizumab. However, lactate dehydrogenase levels remain slightly elevated and haptoglobin levels remain low in some patients suggesting residual low-level hemolysis. This may be due to C3-mediated clearance of paroxysmal nocturnal hemoglobinuria red blood cells through the reticuloendothelial system. DESIGN AND METHODS: Thirty-nine samples from patients not treated with eculizumab and 31 samples from patients treated with eculizumab were obtained (for 17 of these 31 samples there were also samples taken prior to eculizumab treatment). Membrane bound complement was assessed by flow cytometry. Direct antiglobulin testing was carried out using two methods. Lactate dehydrogenase was assayed to assess the degree of hemolysis. RESULTS: Three of 39 patients (8%) with paroxysmal nocturnal hemoglobinuria not on eculizumab had a positive direct antiglobulin test, while the test was positive in 21 of 31 (68%) during eculizumab treatment. Of these 21 patients who had a positive direct antiglobulin test during eculizumab treatment, 17 had been tested prior to treatment; only one was positive. Flow cytometry using anti-C3 monoclonal antibodies was performed on the 21 direct antiglobulin test-positive, eculizumab-treated patients; the median proportion of C3-positive total red blood cells was 26%. Among the eculizumab-treated patients, 16 of the 21 (76.2%) with a positive direct antiglobulin test received at least one transfusion compared with one of ten (10.0%) of those with a negative test (P<0.01). Among the eculizumab-treated patients, the mean hemoglobin value for the 21 with a positive direct antiglobulin test was 9.6+/-0.3 g/dL, whereas that in the ten patients with a negative test was 11.0+/-0.4 g/dL (P=0.02). CONCLUSIONS: These data demonstrate a previously masked mechanism of red cell clearance in paroxysmal nocturnal hemoglobinuria and suggests that blockade of complement at C5 allows C3 fragment accumulation on some paroxysmal nocturnal hemoglobinuria red cells, explaining the residual low-level hemolysis occurring in some eculizumab-treated patients.

The management of pregnancy in paroxysmal nocturnal haemoglobinuria on long term eculizumab.

In Paroxysmal nocturnal haemoglobinuria (PNH), pregnancy is associated with increased maternal and foetal complications to such an extent that the condition has been considered relatively contra-indicated in PNH. Eculizumab has revolutionized the treatment of PNH. We evaluate its use in pregnancy to date. We report on seven patients exposed to eculizumab at different stages of pregnancy including the first two patients to receive the drug from conception to delivery. There was no evidence of complement blockade from cord blood samples taken at delivery. Eculizumab appears safe to use in this setting and is likely to prevent many of the complications usually observed.

Successful liver transplantation for Budd-Chiari syndrome in a patient with paroxysmal nocturnal hemoglobinuria treated with the anti-complement antibody eculizumab.

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare, acquired hemolytic anemia caused by somatic mutations in the phosphatidylinositol glycan-complementation class A gene and the resulting absence of a key complement regulatory protein, CD59. Affected red blood cells in patients with PNH undergo intravascular complement-mediated lysis with resulting anemia, hemoglobinuria, and venous thromboses. Hepatic venous outflow thrombosis [Budd-Chiari syndrome (BCS)] is especially common in PNH patients and often fatal. The few case reports of outcomes in patients undergoing liver transplant for BCS secondary to PNH detail instances of recurrent BCS as well as early thrombotic portal vein occlusion and hepatic artery thrombosis requiring retransplantation. PNH is therefore generally considered a contraindication to liver transplantation. Here we present the first report of a patient with PNH and BCS undergoing successful liver transplantation while receiving eculizumab, a humanized monoclonal antibody that blocks the activation of the terminal complement at C5.

Complement regulator CD59 protects against atherosclerosis by restricting the formation of complement membrane attack complex.

Complement is a central effector system within the immune system and is implicated in a range of inflammatory disorders. CD59 is a key regulator of complement membrane attack complex (MAC) assembly. The atherogenic role of terminal complement has long been suspected but is still unclear. Here, we demonstrate that among mice deficient in apolipoprotein (Apo)E, the additional loss of murine CD59 (mCd59ab(-/-)/ApoE(-/-)) accelerated advanced atherosclerosis featuring occlusive coronary atherosclerosis, vulnerable plaque, and premature death and that these effect could be attenuated by overexpression of human CD59 in the endothelium. Complement inhibition using a neutralizing anti-mouse C5 antibody attenuated atherosclerosis in mCd59ab(-/-)/ApoE(-/-) mice. Furthermore, MAC mediated endothelial damage and promoted foam cell formation. These combined results highlight the atherogenic role of MAC and the atheroprotective role of CD59 and suggest that inhibition of MAC formation may provide a therapeutic approach for the treatment of atherosclerosis.

Eculizumab, a terminal complement inhibitor, improves anaemia in patients with paroxysmal nocturnal haemoglobinuria.

In paroxysmal nocturnal haemoglobinuria (PNH), chronic destruction of PNH red blood cells (RBCs) by complement leads to anaemia and other serious morbidities. Eculizumab inhibits terminal complement-mediated PNH RBC destruction by targeting C5. In the phase III, double-blind, placebo-controlled, TRIUMPH study, eculizumab reduced haemolysis, stabilized haemoglobin levels, reduced transfusion requirements and improved fatigue in patients with PNH. Herein, we explored the effects of eculizumab on measures of anaemia in patients from the TRIUMPH study and the open-label SHEPHERD study, a more heterogeneous population. Eculizumab reduced haemolysis regardless of pretreatment transfusion requirements and regardless of whether or not patients became transfusion-dependent during treatment (P < 0.001). Reduction in haemolysis was associated with increased PNH RBC counts (P < 0.001) while reticulocyte counts remained elevated. Eculizumab-treated patients demonstrated significantly higher levels of haemoglobin as compared with placebo in TRIUMPH and relative to baseline levels in SHEPHERD (P < 0.001 for each study). Eculizumab lowered transfusion requirement across multiple pretreatment transfusion strata and eliminated transfusion support in a majority of both TRIUMPH and SHEPHERD patients (P < 0.001). Patients who required some transfusion support during treatment with eculizumab showed a reduction in haemolysis and transfusion requirements and an improvement in fatigue. Eculizumab reduces haemolysis and improves anaemia and fatigue, regardless of transfusion requirements.

Eculizumab prevents anti-ganglioside antibody-mediated neuropathy in a murine model.

Anti-GQ1b ganglioside antibodies are the serological hallmark of the Miller Fisher syndrome (MFS) variant of the paralytic neuropathy, Guillain-Barré syndrome, and are believed to be the principal pathogenic mediators of the disease. In support of this, we previously showed in an in vitro mouse model of MFS that anti-GQ1b antibodies were able to bind and disrupt presynaptic motor nerve terminals at the neuromuscular junction (NMJ) as one of their target sites, thereby causing muscle paralysis. This injury only occurred through activation of complement, culminating in the formation and deposition of membrane attack complex (MAC, C5b-9) in nerve membranes. Since this step is crucial to the neuropathic process and an important convergence point for antibody and complement mediated membrane injury in general, it forms an attractive pharmacotherapeutic target. Here, we assessed the efficacy of the humanized monoclonal antibody eculizumab, which blocks the formation of human C5a and C5b-9, in preventing the immune-mediated motor neuropathy exemplified in this model. Eculizumab completely prevented electrophysiological and structural lesions at anti-GQ1b antibody pre-incubated NMJs in vitro when using normal human serum (NHS) as a complement source. In a novel in vivo mouse model of MFS generated through intraperitoneal injection of anti-GQ1b antibody and NHS, mice developed respiratory paralysis due to transmission block at diaphragm NMJs, resulting from anti-GQ1b antibody binding and complement activation. Intravenous injection of eculizumab effectively prevented respiratory paralysis and associated functional and morphological hallmarks of terminal motor neuropathy. We show that eculizumab protects against complement-mediated damage in murine MFS, providing the rationale for undertaking clinical trials in this disease and other antibody-mediated neuropathies in which complement activation is believed to be involved.

Multicenter phase 3 study of the complement inhibitor eculizumab for the treatment of patients with paroxysmal nocturnal hemoglobinuria.

The terminal complement inhibitor eculizumab was recently shown to be effective and well tolerated in patients with paroxysmal nocturnal hemoglobinuria (PNH). Here, we extended these observations with results from an open-label, non-placebo-controlled, 52-week, phase 3 clinical safety and efficacy study evaluating eculizumab in a broader PNH patient population. Eculizumab was administered by intravenous infusion at 600 mg every 7 +/- 2 days for 4 weeks; 900 mg 7 +/- 2 days later; followed by 900 mg every 14 +/- 2 days for a total treatment period of 52 weeks. Ninety-seven patients at 33 international sites were enrolled. Patients treated with eculizumab responded with an 87% reduction in hemolysis, as measured by lactate dehydrogenase levels (P < .001). Baseline fatigue scores in the FACIT-Fatigue instrument improved by 12.2 +/- 1.1 points (P < .001). Eculizumab treatment led to an improvement in anemia. The increase in hemoglobin level occurred despite a reduction in transfusion requirements from a median of 8.0 units of packed red cells per patient before treatment to 0.0 units per patient during the study (P < .001). Overall, transfusions were reduced 52% from a mean of 12.3 to 5.9 units of packed red cells per patient. Forty-nine patients (51%) achieved transfusion independence for the entire 52-week period. Improvements in hemolysis, fatigue, and transfusion requirements with eculizumab were independent of baseline levels of hemolysis and degree of thrombocytopenia. Quality of life measures were also broadly improved with eculizumab treatment. This study demonstrates that the beneficial effects of eculizumab treatment in patients with PNH are applicable to a broader population of PNH patients than previously studied. This trial is registered at http://clinicaltrials.gov as NCT00130000.

Anti-C5 antibody treatment ameliorates weakness in experimentally acquired myasthenia gravis.

Myasthenia gravis (MG) is a neuromuscular transmission disorder in which damage to acetylcholine receptors (AChR) on motor endplates by autoantibody-induced complement attack causes muscle weakness. To determine whether and, if so, to what extent, blockade of complement cascade at the C5 step ameliorates disease, we evaluated the effect of administering a functionally blocking anti-C5 mAb in passive experimental MG in Lewis rats induced with AChR Ab McAb-3. In contrast to uniform severe weakness at 24 h requiring euthanasia in untreated animals, anti-C5 mAb-pretreated rats showed no weakness at 48 h. Anti-C5 mAb treatment 24 h after disease induction restored strength in two-thirds of the rats. Immunofluorescence staining of endplates from the treated animals showed that C9 deposition at AChR was reduced and ultrastructural analyses showed that endplates were intact. The results argue that targeting C5 may warrant testing in MG patients and that this approach may be particularly valuable for myasthenic crisis.

Discovery and development of the complement inhibitor eculizumab for the treatment of paroxysmal nocturnal hemoglobinuria.

The complement system provides critical immunoprotective and immunoregulatory functions but uncontrolled complement activation can lead to severe pathology. In the rare hemolytic disease paroxysmal nocturnal hemoglobinuria (PNH), somatic mutations result in a deficiency of glycosylphosphatidylinositol-linked surface proteins, including the terminal complement inhibitor CD59, on hematopoietic stem cells. In a dysfunctional bone marrow background, these mutated progenitor blood cells expand and populate the periphery. Deficiency of CD59 on PNH red blood cells results in chronic complement-mediated intravascular hemolysis, a process central to the morbidity and mortality of PNH. A recently developed, humanized monoclonal antibody directed against complement component C5, eculizumab (Soliris; Alexion Pharmaceuticals Inc., Cheshire, CT, USA), blocks the proinflammatory and cytolytic effects of terminal complement activation. The recent approval of eculizumab as a first-in-class complement inhibitor for the treatment of PNH validates the concept of complement inhibition as an effective therapy and provides rationale for investigation of other indications in which complement plays a role.

Inhibition of terminal complement components in presensitized transplant recipients prevents antibody-mediated rejection leading to long-term graft survival and accommodation.

Ab-mediated rejection (AMR) remains the primary obstacle in presensitized patients following organ transplantation, as it is refractory to anti-T cell therapy and can lead to early graft loss. Complement plays an important role in the process of AMR. In the present study, a murine model was designed to mimic AMR in presensitized patients. This model was used to evaluate the effect of blocking the fifth complement component (C5) with an anti-C5 mAb on prevention of graft rejection. BALB/c recipients were presensitized with C3H donor skin grafts 7 days before heart transplantation from the same donor strain. Heart grafts, transplanted when circulating anti-donor IgG Abs were at peak levels, were rejected in 3 days. Graft rejection was characterized by microvascular thrombosis and extensive deposition of Ab and complement in the grafts, consistent with AMR. Anti-C5 administration completely blocked terminal complement activity and local C5 deposition, and in combination with cyclosporine and short-term cyclophosphamide treatment, it effectively prevented heart graft rejection. These recipients achieved permanent graft survival for >100 days with normal histology despite the presence of systemic and intragraft anti-donor Abs and complement, suggesting ongoing accommodation. Furthermore, double-transplant experiments demonstrated that immunological alterations in both the graft and the recipient were required for successful graft accommodation to occur. These data suggest that terminal complement blockade with a functionally blocking Ab represents a promising therapeutic approach to prevent AMR in presensitized recipients.

Effect of the complement inhibitor eculizumab on thromboembolism in patients with paroxysmal nocturnal hemoglobinuria.

Hemolysis and hemoglobinemia contribute to serious clinical sequelae in hemolytic disorders. In paroxysmal nocturnal hemoglobinuria (PNH) patients, hemolysis can contribute to thromboembolism (TE), the most feared complication in PNH, and the leading cause of disease-related deaths. We evaluated whether long-term treatment with the complement inhibitor eculizumab reduces the rate of TE in patients with PNH. Clinical trial participants included all patients in the 3 eculizumab PNH clinical studies, which recruited patients between 2002 and 2005 (n = 195); patients from these studies continued treatment in the current multinational open-label extension study. Thromboembolism rate with eculizumab treatment was compared with the pretreatment rate in the same patients. The TE event rate with eculizumab treatment was 1.07 events/100 patient-years compared with 7.37 events/100 patient-years (P < .001) prior to eculizumab treatment (relative reduction, 85%; absolute reduction, 6.3 TE events/100 patient-years). With equalization of the duration of exposure before and during treatment for each patient, TE events were reduced from 39 events before eculizumab to 3 events during eculizumab (P < .001). The TE event rate in antithrombotic-treated patients (n = 103) was reduced from 10.61 to 0.62 events/100 patient-years with eculizumab treatment (P < .001). These results show that eculizumab treatment reduces the risk of clinical thromboembolism in patients with PNH. This study is registered at http://clinicaltrials.gov (study ID no. NCT00122317).

The effects of the fibrin-derived peptide Bbeta(15-42) in acute and chronic rodent models of myocardial ischemia-reperfusion.

Many compounds have been shown to prevent reperfusion injury in various animal models, although to date, translation into clinic has revealed several obstacles. Therefore, the National Heart, Lung, and Blood Institute convened a working group to discuss reasons for such failure. As a result, the concept of adequately powered, blinded, randomized studies for preclinical development of a compound has been urged. We investigated the effects of a fibrin-derived peptide Bbeta(15-42) in acute and chronic rodent models of ischemia-reperfusion at three different study centers (Universities of Dusseldorf and Vienna, TNO Biomedical Research). A total of 187 animals were used, and the peptide was compared with the free radical scavenger Tempol, CD18 antibody, alpha-C5 antibody, and the golden standard, ischemic preconditioning. We show that Bbeta(15-42) robustly and reproducibly reduced infarct size in all models of ischemia-reperfusion. Moreover, the peptide significantly reduced plasma levels of the cytokines interleukin 1beta, tumor necrosis factor alpha, and interleukin 6. In rodents, Bbeta(15-42) inhibits proinflammatory cytokine release and is cardioprotective during ischemia-reperfusion injury.

The roles of complement factor C5a and CINC-1 in glucose transport, ultrafiltration, and neutrophil recruitment during peritoneal dialysis.

BACKGROUND: In a recent experimental study, we showed that low molecular weight heparin improved ultrafiltration and blocked complement activation and coagulation in a single peritoneal dialysis (PD) dwell. OBJECTIVE: The aim of the present study was to evaluate the possible contribution of the complement factor C5a and the potential interactions between C5a, the coagulation system, and cytokines of the interleukin (IL)-8 family (cytokine-induced neutrophil chemoattractant; CINC-1). METHODS: Nonuremic rats were exposed through an indwelling catheter to a single dose of 20 mL glucose-(2.5%) based filter-sterilized PD fluid, with or without the addition of anti-rat C5 antibody. The dwell fluid was analyzed 2 and 4 hours later concerning activation of the coagulation cascades, neutrophil recruitment, ultrafiltration volume; CINC-1, glucose, urea, and histamine concentrations; and ex vivo intraperitoneal chemotactic activity. RESULTS: The numbers of neutrophils and levels of thrombin-antithrombin complex (TAT) and CINC-1 increased significantly during the PD dwell. C5 blockade significantly reduced the levels of TAT and increased the ultrafiltration volumes at 2 hours. Glucose concentrations were significantly positively correlated to ultrafiltration volumes. CONCLUSIONS: Blockade of C5 leads to an increase in ultrafiltration, probably by a mechanism that involves a reduction in glucose transport. This effect may form a basis for improving PD efficiency in situations where high glucose transport limits ultrafiltration. Mechanisms connected to complement activation during PD may involve coagulation. Further studies of the intraperitoneal cascade systems under conditions of PD are indicated.

The complement inhibitor eculizumab in paroxysmal nocturnal hemoglobinuria.

BACKGROUND: We tested the safety and efficacy of eculizumab, a humanized monoclonal antibody against terminal complement protein C5 that inhibits terminal complement activation, in patients with paroxysmal nocturnal hemoglobinuria (PNH). METHODS: We conducted a double-blind, randomized, placebo-controlled, multicenter, phase 3 trial. Patients received either placebo or eculizumab intravenously; eculizumab was given at a dose of 600 mg weekly for 4 weeks, followed 1 week later by a 900-mg dose and then 900 mg every other week through week 26. The two primary end points were the stabilization of hemoglobin levels and the number of units of packed red cells transfused. Biochemical indicators of intravascular hemolysis and the patients' quality of life were also assessed. RESULTS: Eighty-seven patients underwent randomization. Stabilization of hemoglobin levels in the absence of transfusions was achieved in 49% (21 of 43) of the patients assigned to eculizumab and none (0 of 44) of those assigned to placebo (P<0.001). During the study, a median of 0 units of packed red cells was administered in the eculizumab group, as compared with 10 units in the placebo group (P<0.001). Eculizumab reduced intravascular hemolysis, as shown by the 85.8% lower median area under the curve for lactate dehydrogenase plotted against time (in days) in the eculizumab group, as compared with the placebo group (58,587 vs. 411,822 U per liter; P<0.001). Clinically significant improvements were also found in the quality of life, as measured by scores on the Functional Assessment of Chronic Illness Therapy-Fatigue instrument (P<0.001) and the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire. Of the 87 patients, 4 in the eculizumab group and 9 in the placebo group had serious adverse events, none of which were considered to be treatment-related; all these patients recovered without sequelae. CONCLUSIONS: Eculizumab is an effective therapy for PNH.