Natural history of paroxysmal nocturnal hemoglobinuria

Stratification of responders towards eculizumab using a structural epitope mapping strategy

The complement component 5 (C5)-binding antibody eculizumab is used to treat patients with paroxysmal nocturnal hemoglobinuria (PNH) and atypical haemolytic uremic syndrome (aHUS). As recently reported there is a need for a precise classification of eculizumab responsive patients to allow for a safe and cost-effective treatment. To allow for such stratification, knowledge of the precise binding site of the drug on its target is crucial. Using a structural epitope mapping strategy based on bacterial surface display, flow cytometric sorting and validation via haemolytic activity testing, we identified six residues essential for binding of eculizumab to C5. This epitope co-localizes with the contact area recently identified by crystallography and includes positions in C5 mutated in non-responders. The identified epitope also includes residue W917, which is unique for human C5 and explains the observed lack of cross-reactivity for eculizumab with other primates. We could demonstrate that Ornithodorus moubata complement inhibitor (OmCI), in contrast to eculizumab, maintained anti-haemolytic function for mutations in any of the six epitope residues, thus representing a possible alternative treatment for patients non-responsive to eculizumab. The method for stratification of patients described here allows for precision medicine and should be applicable to several other diseases and therapeutics.

Eculizumab in the management of paroxysmal nocturnal hemoglobinuria: patient selection and special considerations

Paroxysmal nocturnal hemoglobinuria (PNH) is a nonmalignant clonal disorder resulting from somatic mutation in the PIG-A gene leading to a deficiency of the membrane-anchoring molecule glycosylphosphatidylinositol. The lack of expression of two glycosylphosphatidylinositol-anchored proteins involved in the regulation of the complement system renders PNH erythrocytes susceptible to complement-mediated lysis. Clinical manifestations include thromboembolic disease, chronic kidney injury, pulmonary hypertension, smooth muscle dysfunction, and chronic hemolysis. Until recently, treatment was mainly supportive with most patients suffering from significant morbidity and shortened survival compared to age-matched controls. The development of eculizumab, a humanized monoclonal antibody directed against the terminal complement protein C5, has resulted in dramatic improvements of survival and reduction in complications. In this paper, we review some special considerations pertaining to the use of eculizumab for PNH.

Interim analysis of post-marketing surveillance of eculizumab for paroxysmal nocturnal hemoglobinuria in Japan

Data characterizing the safety and effectiveness of eculizumab in patients with paroxysmal nocturnal hemoglobinuria (PNH) are limited. We describe the safety and effectiveness of eculizumab in PNH patients enrolled in a post-marketing surveillance study. Types and frequencies of observed adverse events were similar to those reported in previous clinical trials and no meningococcal infection was reported. Effectiveness outcomes included the reduction of intravascular hemolysis, the change in hemoglobin (Hb) level, the withdrawal of transfusion and corticosteroids, the change of renal function, and overall survival. The effect of eculizumab on intravascular hemolysis was demonstrated by a reduction in lactate dehydrogenase levels at all measurements after baseline. Significant increases in Hb levels from baseline were also observed after 1 month's treatment with eculizumab (p < 0.01). Of those who were transfusion-dependent at baseline, the median number of transfusions decreased significantly from 18 to 0 unit/year after 1 year of treatment with eculizumab (p < 0.001). An increase in Hb and a high rate of transfusion independence were observed, especially in patients with platelet count ≥150 × 10⁹/L. Approximately 97 % of patients showed maintenance or improvement of renal function. Overall survival rate was about 90 % (median follow-up 1.9 years). These results suggest an acceptable safety profile and favorable prognosis after eculizumab intervention.

Inhibition of terminal complement: a novel therapeutic approach for the treatment of systemic lupus erythematosus

The importance of the complement system in the pathophysiology of systemic lupus erythematosus (SLE) is clear although individual complement components play very different roles in the disease process. Early complement proteins are critical in the clearance of immune complexes and apoptotic bodies, and their absencepredisposesindividualsto SLE. Conversely, activationof terminalcomplement is associated with exacerbations of disease and damage to tissues and organs, particularly in lupus nephritis. Monoclonal antibodies that specifically inhibit terminal complement activation while preserving the critical functions of the early complement cascade have now been developed. These antibodies target the C5 complement protein, blocking its cleavage and the subsequent generation of potent proinflammatory molecules. Anti-C5 therapeutics have recently been investigated in an animal model of SLE and in a Phase I single dose study in humans. The results of these studiesand the multiple roles of complement in SLE are discussed.

Cerebral haemostasis and antiphospholipid antibodies

One of the major clinical concerns of the antiphospholipid syndrome (APS) is the propensity of antiphospholipid(aPL) antibodiesto cause thrombosis in both the large and small vessels of the brain. In this article, we review the current understandingof haemostasis in cerebral circulation and discuss this in the context of antiphospholipidantibodies. The systemic-defect-local-phenotypeparadox is of particular importance in this discussion. In this paradigm, a systemic defect in thrombosis and haemostasis leads to a localized pattern of thrombotic disease because the regional physiological variations in the several prothromboticand anticoagulantfactors and the defect interact so as to favour thrombosis at a particular site. One possible mechanism of initiation of thrombosis in APS is the activation of endothelialcells by aPL that could occur in the cerebral vessels and provoke thrombosis. We review the evidence from gene knockout mice, other animal models and human postmortem examination studies as to which pro- and antithrombotic mechanisms are effecting haemostasis in the cerebral circulation. We conclude that there are large deficits in the understanding of the regulation of haemostasis in the human brain. As a consequencethere is a lack of knowledgeabout the effect of aPL on cerebral endothelium and thrombosis. Recent developments in gene expression profiling may have an impact on our understandingof endothelialfunctionin the brain. More research is required.

Therapeutic complement inhibition in complement-mediated hemolytic anemias: Past, present and future

The introduction in the clinic of anti-complement agents represented a major achievement which gave to physicians a novel etiologic treatment for different human diseases. Indeed, the first anti-complement agent eculizumab has changed the treatment paradigm of paroxysmal nocturnal hemoglobinuria (PNH), dramatically impacting its severe clinical course. In addition, eculizumab is the first agent approved for atypical Hemolytic Uremic Syndrome (aHUS), a life-threatening inherited thrombotic microangiopathy. Nevertheless, such remarkable milestone in medicine has brought to the fore additional challenges for the scientific community. Indeed, the list of complement-mediated anemias is not limited to PNH and aHUS, and other human diseases can be considered for anti-complement treatment. They include other thrombotic microangiopathies, as well as some antibody-mediated hemolytic anemias. Furthermore, more than ten years of experience with eculizumab led to a better understanding of the individual steps of the complement cascade involved in the pathophysiology of different human diseases. Based on this, new unmet clinical needs are emerging; a number of different strategies are currently under development to improve current anti-complement treatment, trying to address these specific clinical needs. They include: (i) alternative anti-C5 agents, which may improve the heaviness of eculizumab treatment; (ii) broad-spectrum anti-C3 agents, which may improve the efficacy of anti-C5 treatment by intercepting the complement cascade upstream (i.e., preventing C3-mediated extravascular hemolysis in PNH); (iii) targeted inhibitors of selective complement activating pathways, which may prevent early pathogenic events of specific human diseases (e.g., anti-classical pathway for antibody-mediated anemias, or anti-alternative pathway for PNH and aHUS). Here we briefly summarize the status of art of current and future complement inhibition for different complement-mediated anemias, trying to identify the most promising approaches for each individual disease.

Impact of eculizumab treatment on paroxysmal nocturnal hemoglobinuria: a treatment versus no-treatment study

Intravascular hemolysis in Paroxysmal nocturnal hemoglobinuria (PNH) can effectively be controlled with eculizumab, a humanized monoclonal antibody that binds complement protein C5. We report here a retrospective comparison study between 123 patients treated with eculizumab in the recent period (>2005) and 191 historical controls (from the French registry). Overall survival (OS) at 6 years was 92% (95%CI, 87 to 98) in the eculizumab cohort versus 80% (95%CI 70 to 91) in historical controls diagnosed after 1985 (HR 0.38 [0.15 to 0.94], P = 0.037). There were significantly fewer thrombotic events (TEs) in the group of patients treated with eculizumab (4% [1-10]) as compared to the historical cohort (27% [20-34]). However, we found that TEs may still occur after the initiation of eculizumab treatment and that previous TEs still have a negative impact on survival. Evolutions to myelodysplastic syndrome or acute leukemia were similar in both cohorts. There was less evolution to aplastic anemia in the treatment group. In multivariate analysis, absence of a previous TE and treatment with eculizumab were associated with a better OS. Treatment with eculizumab improves overall survival in classic PNH patients without increasing the risk of clonal evolution.

Clonal hematopoiesis in acquired aplastic anemia

Clonal hematopoiesis (CH) in aplastic anemia (AA) has been closely linked to the evolution of late clonal disorders, including paroxysmal nocturnal hemoglobinuria and myelodysplastic syndromes (MDS)/acute myeloid leukemia (AML), which are common complications after successful immunosuppressive therapy (IST). With the advent of high-throughput sequencing of recent years, the molecular aspect of CH in AA has been clarified by comprehensive detection of somatic mutations that drive clonal evolution. Genetic abnormalities are found in ∼50% of patients with AA and, except for PIGA mutations and copy-neutral loss-of-heterozygosity, or uniparental disomy (UPD) in 6p (6pUPD), are most frequently represented by mutations involving genes commonly mutated in myeloid malignancies, including DNMT3A, ASXL1, and BCOR/BCORL1 Mutations exhibit distinct chronological profiles and clinical impacts. BCOR/BCORL1 and PIGA mutations tend to disappear or show stable clone size and predict a better response to IST and a significantly better clinical outcome compared with mutations in DNMT3A, ASXL1, and other genes, which are likely to increase their clone size, are associated with a faster progression to MDS/AML, and predict an unfavorable survival. High frequency of 6pUPD and overrepresentation of PIGA and BCOR/BCORL1 mutations are unique to AA, suggesting the role of autoimmunity in clonal selection. By contrast, DNMT3A and ASXL1 mutations, also commonly seen in CH in the general population, indicate a close link to CH in the aged bone marrow, in terms of the mechanism for selection. Detection and close monitoring of somatic mutations/evolution may help with prediction and diagnosis of clonal evolution of MDS/AML and better management of patients with AA.

The role of complement activation in thrombosis and hemolytic anemias

OBJECTIVE

The objective of this study was to describe complement activation in hemostatic and pathologic states of coagulation and in the acquired and congenital hemolytic anemias.

METHODS AND RESULTS

We review published and emerging data on the involvement of the classic, alternative and lectin-based complement pathways in coagulation and the hemolytic anemias. The alternative pathway in particular is always "on," at low levels, and is particularly sensitive to hyper-activation in a variety of physiologic and pathologic states including infection, autoimmune disorders, thrombosis and pregnancy, requiring tight control predicated on a variety of soluble and membrane bound regulatory proteins. In acquired hemolytic anemias such as paroxysmal nocturnal hemoglobinuria (PNH) and cold agglutinin disease (CAD), the complement system directly induces red blood cell injury, resulting in intravascular and extravascular hemolysis. In congenital hemolytic anemias such as sickle cell disease and β-thalassemia, the complement system may also contribute to thrombosis and vascular disease. Complement activation may also lead to a storage lesion in red blood cells prior to transfusion.

CONCLUSION

Complement pathways are activated in hemolytic anemias and are closely linked with thrombosis. In acquired disorders such as PNH and possibly CAD, inhibition of the alternative complement pathway improves clinical outcomes and reduces thrombosis risk. Whether complement inhibition has a similar role in congenital hemolytic anemias apart from the atypical hemolytic-uremic (aHUS)-type thrombotic microangiopathies remains to be determined.

A comparative analysis of clinical characteristics of patients with paroxysmal nocturnal hemoglobinuria between Asia and Europe/America

To accurately analyze the clinical characteristics of paroxysmal nocturnal hemoglobinuria (PNH) in different ethnic backgrounds, we retrieved all retrospective studies on clinical characteristics of PNH with a median follow-up period >60 months published after 2000, analyzed the clinical characteristics of PNH patients in Asia and European/America, and statistically compared enumeration data in these studies. We included 1665 patients in this analysis. The proportion of female patients in Asia was significantly lower than that in Europe/America (P = 0.000). Incidence rates of hemoglobinuria and thromboembolism in Asia were significantly lower than in Europe/America (both P values were 0.000). Within the subgroups of patients with thromboembolism, Asian patients had a higher proportion of arterial thrombosis while Western patients had a higher proportion of abdominal venous thrombosis. Bone marrow failure was not clearly defined in most studies. The proportion of patients with pancytopenia was higher in China than in France (P = 0.048). The total death rates were similar in both ethnic groups (P > 0.05). In Europe/America the major cause of death was thromboembolism and in Asian countries was serious infections. Differences in population characteristics of PNH patients among different ethnic groups indicate the possibility of differential pathogenesis and may be informative for treatment decisions.

Pregnancy outcomes of patients with paroxysmal nocturnal hemoglobinuria treated with eculizumab: a Japanese experience and updated review

Pregnancy with paroxysmal nocturnal hemoglobinuria (PNH) is associated with significant risk of complications, such as life-threatening thrombosis. Recently, eculizumab has come into clinical use and revolutionized the treatment of PNH. However, clinical information regarding eculizumab use for PNH during pregnancy is limited. The present report describes pregnancies with PNH treated with eculizumab that were registered with the Japan PNH study group and reviews the literature. In case 1, the patient received eculizumab throughout pregnancy and delivered a healthy neonate at term, although breakthrough hemolysis occurred at 20 weeks of gestation. In case 2, the patient discontinued eculizumab before pregnancy and developed preeclampsia at 27 weeks of gestation. She received eculizumab and delivered a preterm, but healthy, neonate by cesarean section. In case 3, the patient received eculizumab from 18 weeks of gestation and delivered a healthy neonate at term without any complications. Reports of 11 pregnant women treated with eculizumab were identified in the literature. Of 14 pregnancies, including our own cases, breakthrough hemolysis and preeclampsia occurred in five and two cases, respectively. There were no thrombotic complications, maternal or neonatal deaths, or fetal structural abnormalities. Thus, eculizumab appears to be safe and effective for managing PNH during pregnancy.

Predictive Factors of Mortality in Population of Patients with Paroxysmal Nocturnal Hemoglobinuria (PNH): Results from a Korean PNH Registry

Paroxysmal nocturnal hemoglobinuria (PNH) is a progressive, systemic, life-threatening disease, characterized by chronic uncontrolled complement activation. A retrospective analysis of 301 Korean PNH patients who had not received eculizumab was performed to systematically identify the clinical symptoms and signs predictive of mortality. PNH patients with hemolysis (lactate dehydrogenase [LDH] ≥ 1.5 × the upper limit of normal [ULN]) have a 4.8-fold higher mortality rate compared with the age- and sex-matched general population (P < 0.001). In contrast, patients with LDH < 1.5 × ULN have a similar mortality rate as the general population (P = 0.824). Thromboembolism (TE) (odds ratio [OR] 7.11; 95% confidence interval [CI] (3.052-16.562), renal impairment (OR, 2.953; 95% CI, 1.116-7.818) and PNH-cytopenia (OR, 2.547; 95% CI, 1.159-5.597) are independent risk factors for mortality, with mortality rates 14-fold (P < 0.001), 8-fold (P < 0.001), and 6.2-fold (P < 0.001) greater than that of the age- and sex-matched general population, respectively. The combination of hemolysis and 1 or more of the clinical symptoms such as abdominal pain, chest pain, or dyspnea, resulted in a much greater increased mortality rate when compared with patients with just the individual symptom alone or just hemolysis. Early identification of risk factors related to mortality is crucial for the management of PNH. This trial was registered at www.clinicaltrials.gov as NCT01224483.

Postpartum thrombotic complication in a patient with paroxysmal nocturnal hemoglobinuria

Paroxysmal nocturnal hemoglobinuria (PNH) is a clonal nonneoplastic hematopoietic stem cell disease characterized by an acquired mutation of the PIG-A gene with reduction or absence of CD55 and CD59. The absence of these proteins renders PNH erythrocytes susceptible to complement-mediated hemolysis. We report the case of a PNH patient before and during pregnancy until delivery. We observed and treated some postpartum thrombotic complications. Eculizumab should be used with caution in pregnancy. There are several reports supporting its use in these patients. This case should be considered paradigmatic of a series of clinical situations that may occur in the course of a pregnancy in patients with PNH: increased need for transfusion, need to increase the dose of Eculizumab, and insurgence of fetal sufferance. Moreover, after delivery, the patient, despite adequate prophylaxis with low-molecular-weight heparins, presented severe complications: development of pleural and peritoneal effusion, pulmonary embolism, bilateral upper limbs thrombophlebitis, and a possible abdominal angina with a transient paralytic ileus. All these complications were overcome and now the baby is healthy and the mother has returned to the usual therapeutic regimen.

Successful Treatment of Ascites using a Denver® Peritoneovenous Shunt in a Patient with Paroxysmal Nocturnal Hemoglobinuria and Budd-Chiari syndrome

A 56-year-old man was diagnosed with aplastic anemia and paroxysmal nocturnal hemoglobinuria at 43 years of age and treatment with cyclosporin A was started. Liver cirrhosis, ascites, and thrombus in the hepatic veins were found at 56 years of age and Budd-Chiari syndrome (BCS) was diagnosed according to angiography findings. He was treated with diuretics and paracentesis was performed several times, but with limited efficacy. A Denver^® peritoneovenous shunt (PVS) was inserted into the right jugular vein; his ascites and renal function improved immediately and his general condition has remained good for 12 months since starting the above treatment regimen. A PVS is a treatment option for ascites due to BCS.

Overview of Laboratory Testing and Clinical Presentations of Complement Deficiencies and Dysregulation

Historically, complement disorders have been attributed to immunodeficiency associated with severe or frequent infection. More recently, however, complement has been recognized for its role in inflammation, autoimmune disorders, and vision loss. This paradigm shift requires a fundamental change in how complement testing is performed and interpreted. Here, we provide an overview of the complement pathways and summarize recent literature related to hereditary and acquired angioedema, infectious diseases, autoimmunity, and age-related macular degeneration. The impact of complement dysregulation in atypical hemolytic uremic syndrome, paroxysmal nocturnal hemoglobinuria, and C3 glomerulopathies is also described. The advent of therapeutics such as eculizumab and other complement inhibitors has driven the need to more fully understand complement to facilitate diagnosis and monitoring. In this report, we review analytical methods and discuss challenges for the clinical laboratory in measuring this complex biochemical system.

Evaluation of paroxysmal nocturnal hemoglobinuria screening by flow cytometry through multicentric interlaboratory comparison in four countries

OBJECTIVES

Paroxysmal nocturnal hemoglobinuria (PNH) is currently diagnosed by flow cytometry; although highly sensitive, its interpretation and reporting appear as critical as its technique. Thus, we developed a quality control scheme for the French-speaking region based on the international recommendations for PNH screening.

METHODS

After a topical workshop, we proposed a 1-year, two-step survey program to any volunteering French-speaking clinical laboratory. The first survey consisted of sending raw data files to evaluate gating and the interpretation strategy of each center. The second stipulated sending fresh whole-blood samples to evaluate the whole process and its practice.

RESULTS

Forty-nine participants from voluntary centers returned results for each of the two successive surveys. On virtual survey, 27% reported false-positive PNH created by immature granulocytes, whereas the minor PNH clone was not detected by 9%. On fresh survey, 63% of centers used at least the same six-color combination (CD24, CD14, CD33, CD15, CD45, and fluorescent aerolysin), and nearly 70% of participants were able to perform a sensitivity test less than 0.1% on neutrophils. All participants detected the major PNH clone, yet 16% returned false-positive results for the non-PNH clone case.

CONCLUSIONS

We succeeded in rallying numerous French-speaking clinical laboratories for both surveys and in harmonizing the technical practice by highlighting common pitfalls.

Neutrophil activation and nucleosomes as markers of systemic inflammation in paroxysmal nocturnal hemoglobinuria: effects of eculizumab

BACKGROUND

Paroxysmal nocturnal hemoglobinuria (PNH) is characterized by complement-mediated hemolysis and a high risk of life-threatening venous and arterial thrombosis. Uncontrolled complement activation and the release of cell-free heme may result in systemic inflammation, neutrophil activation, and the release of procoagulant neutrophilic proteases. Eculizumab, an antibody to complement factor C5, inhibits hemolysis and reduces thrombotic risk.

OBJECTIVES

To study neutrophil activation and nucleosome levels in relation to thrombosis in PNH patients before and during treatment with eculizumab.

PATIENTS/METHODS

In 51 untreated PNH patients, including 20 patients before and after commencing eculizumab treatment, we have assessed neutrophil activation by measuring elastase-α1 -antitrypsin (EA) complexes and circulating nucleosomes, as established markers for systemic inflammation and cell death.

RESULTS

Nucleosomes (median; range; 95% confidence interval [CI]), but not EA complexes, were higher in PNH patients with a history of thrombosis (16; 7-264; 0.3-94 U mL(-1) , n = 12) than in those without (6; 6-35; 7-11 U mL(-1) , n = 39) or controls (8; 6-23; 7-12 U mL(-1) , n = 17). EA complexes, but not nucleosomes, decreased promptly and markedly upon eculizumab treatment. EA complexes (estimated marginal means; 95% CI) remained low at ≥ 12 weeks (50; 34-67) compared with baseline (12; -6 to 29).

CONCLUSIONS

The increased nucleosome levels in PNH patients with a history of thrombosis suggest systemic inflammation and/or cell death. Neutrophil activation markers did not differ between patients with and without a history of thrombosis and healthy controls. Interestingly, basal neutrophil activation in PNH patients significantly decreases on treatment with eculizumab, indicating that neutrophil activation is C5a driven.

Distinct subgroups of paroxysmal nocturnal hemoglobinuria (PNH) with cytopenia: results from South Korean National PNH Registry

We retrospectively assessed the clinical characteristics of patients with paroxysmal nocturnal hemoglobinuria (PNH) according to severity of cytopenia. A total of 282 patients with hematological parameters assessed at the time of diagnosis of PNH were included. There were 24 patients with PNH/severe aplastic anemia (SAA) (at least two of the three criteria; hemoglobin ≤8 g/dL; absolute neutrophil count (ANC) <0.5 × 10(9)/L; platelet count <20 × 10(9)/L), 96 patients with PNH/aplastic anemia (AA) (at least two of the three criteria; hemoglobin ≤10 g/dL; ANC 0.5-1.5 × 10(9)/L; platelet count 20-100 × 10(9)/L), and 162 classic PNH patients. Compared with the classic PNH subgroup, the PNH/SAA subgroup had a significantly lower median granulocyte PNH clone size (26.7 vs. 51.0 %, P = 0.021) and lower incidence of lactate dehydrogenase ≥1.5 times the upper limit of normal (52.9 vs. 80.0 %, P = 0.049). The incidence of thromboembolism was similar in both subgroups. Overall survival was significantly lower in the PNH/SAA subgroup than in the classic PNH subgroup (P = 0.033). Our findings suggest that identification of patients with PNH/SAA at the time of diagnosis is important because of different clinical manifestations and poorer outcome compared with patients with classic PNH (clinicaltrials.gov identifier: #NCT01224483).

Eculizumab in Pregnant Patients with Paroxysmal Nocturnal Hemoglobinuria

BACKGROUND

Eculizumab, a humanized monoclonal antibody against complement protein C5 that inhibits terminal complement activation, has been shown to prevent complications of paroxysmal nocturnal hemoglobinuria (PNH) and improve quality of life and overall survival, but data on the use of eculizumab in women during pregnancy are scarce.

METHODS

We designed a questionnaire to solicit data on pregnancies in women with PNH and sent it to the members of the International PNH Interest Group and to the physicians participating in the International PNH Registry. We assessed the safety and efficacy of eculizumab in pregnant patients with PNH by examining the birth and developmental records of the children born and adverse events in the mothers.

RESULTS

Of the 94 questionnaires that were sent out, 75 were returned, representing a response rate of 80%. Data on 75 pregnancies in 61 women with PNH were evaluated. There were no maternal deaths and three fetal deaths (4%). Six miscarriages (8%) occurred during the first trimester. Requirements for transfusion of red cells increased during pregnancy, from a mean of 0.14 units per month in the 6 months before pregnancy to 0.92 units per month during pregnancy. Platelet transfusions were given in 16 pregnancies. In 54% of pregnancies that progressed past the first trimester, the dose or the frequency of use of eculizumab had to be increased. Low-molecular-weight heparin was used in 88% of the pregnancies. Ten hemorrhagic events and 2 thrombotic events were documented; both thrombotic events occurred during the postpartum period. A total of 22 births (29%) were premature. Twenty cord-blood samples were examined for the presence of eculizumab; the drug was detected in 7 of the samples. A total of 25 babies were breast-fed, and in 10 of these cases, breast milk was examined for the presence of eculizumab; the drug was not detected in any of the 10 breast-milk samples.

CONCLUSIONS

Eculizumab provided benefit for women with PNH during pregnancy, as evidenced by a high rate of fetal survival and a low rate of maternal complications. (ClinicalTrials.gov number, NCT01374360.).

Flow cytometry screening for paroxysmal nocturnal hemoglobinuria: A single-center experience in Saudi Arabia

BACKGROUND

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare acquired clonal hematopoietic stem cell disorder, characterized by the deficiency of glycosylphosphatidylinositol (GPI) that anchors proteins in cell membranes. PNH is manifest variously with hemoglobinuria, thrombosis, or bone marrow failure. This retrospective study was aimed at assessing the incidence and characteristics of patients diagnosed with PNH in the King Fisal Specialist Hospital and research center.

METHODS

Patients referred for PNH diagnosis at King Faisal Specialist Hospital and Research Centre, Riyadh, during the 2-year period (2012-2013) were included in the analysis. Peripheral blood samples were used for multi-parametric flow cytometry analysis based on fluorescent inactive aerolysin (FLAER), and the markers, CD235a and CD59 on red blood cells (RBCs), and CD14, CD45, CD64, CD24, and CD15 on white blood cells (WBCs) exclusively monocytes and granulocytes. Univariate analysis of the disease characteristics was performed.

RESULTS

Of the 366 samples submitted for PNH screening, 14 were positive (4%) and 11 were evaluable. Of the 11 patients analyzed, 8 patients (73%) presented with aplastic anemia, 1 patient (9%) each with pancytopenia, Budd-Chiari syndrome, and immune thrombocytopenia purpura. All samples showed type II and III GPI-deficient clones with a median clone size of 15% (range, 0.7%-56%) in the RBCs, and 63% (range, 3.8%-100%) in WBCs (monocytes and granulocytes).

CONCLUSIONS

This study confirms the rarity of PNH and its predominant presentation as aplastic anemia or thrombosis in a Saudi Arabian population, similar to the worldwide incidence.

[Paroxysmal nocturnal hemoglobinuria: An unknown cause of thrombosis?]

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare acquired disorder of hematopoietic stem cells. Somatic mutation in the phosphatidylinositol glycan class A (PIG-A), X-linked gene, is responsible for a deficiency in glycosphosphatidylinositol-anchored proteins (GPI-AP). The lack of one of the GPI-AP complement regulatory proteins (CD55, CD59) leads to hemolysis. The disease is diagnosed with hemolytic anemia, marrow failure and thrombosis. Thromboembolic complication occurs in 30% of patient after 10 years of follow-up and is the first event in one out of 10 patients. The two most common sites are hepatic and cerebral veins. These locations are correlated with high risk of death. Currently, these data are balanced with the use of a monoclonal antibody (Eculizumab), which has significantly improved the prognosis with a survival similar to general population after 36 months of follow-up. Anticoagulant treatment is recommended after a thromboembolic event but has no place in primary prophylaxis.

Paroxysmal nocturnal haemoglobinuria at Oslo University Hospital 2000-2010

BACKGROUND

Paroxysmal nocturnal haemoglobinuria (PNH) is a rare haematological disease characterised by chronic haemolysis, pancytopenia and venous thrombosis. The condition is attributable to a lack of control of complement attack on erythrocytes, thrombocytes and leukocytes, and can be diagnosed by means of flow cytometry. In this quality assurance study, we have reviewed information from the medical records of all patients tested for PNH using flow cytometry at our laboratory over a ten-year period.

MATERIAL AND METHOD

In the period 2000-2010 a total of 28 patients were tested for PNH using flow cytometry at the Department of Immunology and Transfusion Medicine, Oslo University Hospital. We have reviewed the results of these examinations retrospectively together with information from medical records and transfusion data for the patients concerned.

RESULTS

Flow cytometry identified 22 patients with PNH: four with classic disease and 18 with PNH secondary to another bone marrow disease. Five patients had atypical thrombosis. Seventeen patients received antithymocyte globulin or drug treatment; of these, six recovered from their bone marrow disease, while six died and five had a need for long-term transfusion. Five patients with life-threatening bone marrow disease underwent allogeneic stem cell transplantation, three of whom died. Six of 22 patients received eculizumab; the need for transfusion has been reduced or eliminated in three patients treated with eculizumab over a longer period.

INTERPRETATION

Flow cytometry identified PNH in a majority of patients from whom we obtained samples. Most patients had a PNH clone secondary to bone marrow failure. Atypical thrombosis should be borne in mind as an indication for the test. Treatment with eculizumab is relevant for selected patients with PNH.

Alterations in markers of coagulation and fibrinolysis in patients with Paroxysmal Nocturnal Hemoglobinuria before and during treatment with eculizumab

BACKGROUND

Paroxysmal Nocturnal Hemoglobinuria is characterized by complement-mediated hemolysis and an increased thrombosis risk. Eculizumab, an antibody to complement factor C5, reduces thrombotic risk via unknown mechanisms. Clinical observations suggest that eculizumab has an immediate effect.

OBJECTIVES

A better understanding of the mechanism via which eculizumab reduces thrombotic risk by studying its pharmacodynamic effect on coagulation and fibrinolysis.

METHODS

We measured microparticles (MP), tissue factor (TF) activity, prothrombin fragment 1+2 (F1+2), D-dimer and simultaneously thrombin and plasmin generation in 55 PNH patients. In 20 patients, parameters were compared before and during eculizumab treatment (at 1 and 2hours, 1, 4 and≥12weeks after commencement).

RESULTS

Patients with a history of thrombosis had elevated D-dimers (p=0.02) but not MP. Among patients on anticoagulants, those with thrombosis had higher F1+2 concentrations (p=0.003). TF activity was undetectable in plasma MP. Unexpectedly, thrombin peak height and thrombin potential were significantly lower in PNH patients than in healthy controls. Fibrinolysis parameters were normal. During eculizumab treatment D-dimer levels significantly decreased after 1hour (p=0.008) and remained decreased at≥12weeks (p=0.03). F1+2 (p=0.03) and thrombin peak height (p=0.02) in patients not on anticoagulants significantly decreased at≥week 12. MP remained unchanged.

CONCLUSIONS

Eculizumab induces an immediate decrease of D-dimer levels but not of other markers. The decrease in thrombin peak height and F1+2 suggests that eculizumab reduces thrombin generation. Elevated D-dimer levels in untreated PNH patients with a history of thrombosis suggest possible value in predicting thrombotic risk.

Further evidence that paroxysmal nocturnal haemoglobinuria is a disorder of defective cell membrane lipid rafts

The glycolipid glycosylphosphatidylinositol anchor (GPI-A) plays an important role in lipid raft formation, which is required for proper expression on the cell surface of two inhibitors of the complement cascade, CD55 and CD59. The absence of these markers from the surface of blood cells, including erythrocytes, makes the cells susceptible to complement lysis, as seen in patients suffering from paroxysmal nocturnal haemoglobinuria (PNH). However, the explanation for why PNH-affected hematopoietic stem/progenitor cells (HSPCs) expand over time in BM is still unclear. Here, we propose an explanation for this phenomenon and provide evidence that a defect in lipid raft formation in HSPCs leads to defective CXCR4- and VLA-4-mediated retention of these cells in BM. In support of this possibility, BM-isolated CD34⁺ cells from PNH patients show a defect in the incorporation of CXCR4 and VLA-4 into membrane lipid rafts, respond weakly to SDF-1 stimulation, and show defective adhesion to fibronectin. Similar data were obtained with the GPI-A⁻ Jurkat cell line. Moreover, we also report that chimeric mice transplanted with CD55^−/− CD59^−/− BM cells but with proper GPI-A expression do not expand over time in transplanted hosts. On the basis of these findings, we propose that a defect in lipid raft formation in PNH-mutated HSPCs makes these cells more mobile, so that they expand and out-compete normal HSPCs from their BM niches over time.

Screening of patients with idiopathic venous thromboembolism for paroxysmal nocturnal hemoglobinuria clones

Paroxysmal nocturnal hemoglobinuria (PNH) is an uncommon disorder characterized by hemolysis, thrombosis and marrow failure. Whereas venous and arterial thrombosis is a very common symptom of the disease, the frequency of PNH clones in patients with unexplained venous thromboembolism, including deep vein thrombosis and pulmonary embolism, has not been studied. We conducted a cross sectional study evaluating the presence of PNH clones in patients with prevalent venous thromboembolism using a high sensitivity flow cytometry assay for erythrocytes and neutrophils. Among the 388 patients enrolled in the study one patient had a detectable PNH clone of 0.02% in the neutrophil population (0.26%; 95% CI 0.05 to 1.45) and no detectable erythrocyte clone. We conclude that the presence of PNH clones in patients with idiopathic venous thrombosis is rare. Screening for PNH clones among VTE patients might be better reserved for patients with signs of hemolysis.

Congenital CD59 Deficiency

The severe clinical symptoms of inherited CD59 deficiency confirm the importance of CD59 as essential complement regulatory protein for protection of cells against complement attack, in particular protection of hematopoietic cells and human neuronal tissue. Targeted complement inhibition might become a treatment option as suggested by a case report. The easy diagnostic approach by flow cytometry and the advent of a new treatment option should increase the awareness of this rare differential diagnosis and lead to further studies on their pathophysiology.

Paroxysmal nocturnal haemoglobinuria: to prednisone or not to prednisone?--a case report of a patient previously treated with steroids for 15 yrs and significant response on eculizumab

BACKGROUND

Paroxysmal nocturnal haemoglobinuria (PNH) is a rare acquired haematopoietic stem cell disorder characterised by persistent haemolysis and platelet activation, severe end-organ damage, an increased risk of thrombosis and early mortality. We present the case of a 56-year-old male with long-standing PNH and significant disease-related morbidity who underwent steroid therapy for approximately 15 yrs before treatment with eculizumab, a humanized monoclonal antibody that blocks the terminal phase of the complement cascade at the C5 level.

CASE HISTORY

The patient presented with a severely impaired quality of life in 1997 and was diagnosed with PNH 8 months later, soon after which he was commenced on steroid therapy with prednisone. During long-term steroid therapy with progressive increases in prednisone dose, the patient had frequent haemolytic episodes as well as thrombosis and renal complications. He also experienced Cushing's syndrome with arterial hypertension, insulin-dependent diabetes mellitus, osteoporosis, acne and portal fibrosis. Eculizumab therapy was started in late-2009 and led to rapid improvements in haemoglobin and lactate dehydrogenase levels with a complete cessation of haemolytic episodes. Eculizumab has been well tolerated.

CONCLUSIONS

Long-term steroid therapy was not effective in controlling PNH in this patient and was associated with significant comorbidities. Treatment with eculizumab led to major improvements, even after such a long period with relatively uncontrolled disease.

Complement the hemostatic system: an intimate relationship

The complement system is important part of our innate immune system and interacts directly with the hemostatic system. Disorders of complement activation or dysregulation resulting in excess complement generation, such as Paroxysmal Nocturnal Hemoglobinuria (PNH), atypical Hemolytic uremic Syndrome (aHUS) and antiphospholipid syndrome (APLS) have been associated with significant thrombophilia. Terminal Complement (C5b-9) deposition on endothelial and tumor cell membranes has also been reported in a variety of cancer. Recent developments in complement inhibition have given us new insights into the mechanism of thrombosis in these disorders.

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

The complement inhibitor eculizumab is a humanized monoclonal antibody against C5. It was developed to specifically target cleavage of C5 thus preventing release of C5a and activation of the terminal pathway. Paroxysmal nocturnal hemoglobinuria (PNH) and atypical hemolytic uremic syndrome (aHUS) are 2 diseases with distinctly different underlying molecular mechanisms. In PNH, progeny of hematopoietic stem cells that harbor somatic mutations lead to a population of peripheral blood cells that are deficient in complement regulators resulting in hemolysis and thrombosis. In aHUS, germline mutations in complement proteins or their regulators fail to protect the glomerular endothelium from complement activation resulting in thrombotic microangiopathy and renal failure. Critical to the development of either disease is activation of the terminal complement pathway. Understanding this step has led to the study of eculizumab as a treatment for these diseases. In clinical trials, eculizumab is proven to be effective and safe in PNH and aHUS.

Paroxysmal nocturnal hemoglobinuria clone in 103 Brazilian patients: diagnosis and classification

BACKGROUND

Paroxysmal nocturnal hemoglobinuria is an acquired chronic hemolytic anemia, which often manifests as peripheral blood cytopenias and thrombosis.

OBJECTIVE

The aim of this study is to describe a Brazilian population of paroxysmal nocturnal hemoglobinuria patients.

METHODS

One hundred and three paroxysmal nocturnal hemoglobinuria cases were retrospectively reviewed and the clinical presentation, thrombosis, survival, and clone size were assessed. Diagnosis was established by flow cytometry.

RESULTS

Fifty-two male and 51 female patients with a median age of 24.1 years (5.5-62 years) were studied. Clinical symptoms included hemoglobinuria (18.4%), infection (46.6%) and thrombosis (16.5%), and 80.6% had pancytopenia. Patients were classified as classic paroxysmal nocturnal hemoglobinuria (10), paroxysmal nocturnal hemoglobinuria with aplastic anemia (39), and paroxysmal nocturnal hemoglobinuria with subclinical features and aplastic anemia (54). There were significant differences in terms of median age, size of clone, clinical symptoms, and peripheral blood cell counts between the three subcategories. The clone size in erythrocytes and granulocytes were respectively 0.04% (range: 0-18%) and 7.3% (range: 0.3-68.7%) in patients with subclinical features and aplastic anemia, 15.8% (range: 0-99.7%) and 63.0% (range: 1.7-99.8%) in patients with aplastic anemia alone, and 82.2% (range: 0-99.85%) and 98.0% (81.3-100.0%) in Classic disease. Statistical differences were identified for platelets (p-value=0.001), lactate dehydrogenase (p-value=0.002) and the clone size (p-value<0.001) in patients who suffered thrombotic events compared to those who did not. Overall survival was 81.7%, with patients with subclinical features and aplastic anemia having lower overall survival (76.5%).

CONCLUSION

This retrospective review of 103 patients over an 11-year period represents the largest collection of paroxysmal nocturnal hemoglobinuria cases from a single center in Brazil. Flow cytometry showed that a larger clone was associated with classical symptoms and increased risk of thrombosis, even in patients with bone marrow failure, whereas a smaller clone was associated with bone marrow aplasia.

Cerebral venous thrombosis in paroxysmal nocturnal hemoglobinuria: a series of 15 cases and review of the literature

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare acquired disorder of hematopoietic stem cells characterized by hemolytic anemia, marrow failure, and a high incidence of life-threatening venous thrombosis. Cerebral venous system is the second most frequent location of thrombosis after hepatic veins. However, data about PNH-related cerebral venous thrombosis (CVT) are very scarce because of the rarity of both the disorders.We report a French study about PNH patients with CVT. Patients were recruited retrospectively, from the Société Française d'Hématologie (SFH) registry of 465 patients with PNH; the Lariboisière registry of 399 patients with CVT; and a direct contact with 26 French Hematology Units. We review cases reported since 1938 in the English and French language literature. We then compared patients of our series with cases from the literature, with non-PNH-related CVT cases from Lariboisière registry, and with PNH patients without CVT from SFH registry.Fifteen patients were included between 1990 and 2012. Most patients were women (12/15) and half of them presented associated hormonal venous thrombosis risk factors. Three patients had concomitant hepatic vein thrombosis. CVT was the first manifestation of PNH in 4 patients. No major difference in CVT characteristics was found compared with non-PNH-related CVT cases, except for a younger age at diagnosis in PNH patients (P < 0.001). All patients were treated with anticoagulation therapy. One death occurred in acute stage. All surviving patients were independent 1 year after. Median survival time was 9 years. Recurrent thrombosis rate was 50% at 6 years, occurring in patients that did not have bone marrow transplantation or eculizumab therapy. Cases of death were mainly related to hepatic vein thrombosis.Prognosis of CVT was good in our series. However, these patients have a poor long-term prognosis due to PNH disease by itself. PNH treatment should be proposed as soon as possible to avoid recurrent thrombosis. Besides, inaugural CVT events encourage investigating PNH in case of cytopenia, hemolysis, abdominal veins thrombosis, or aplastic anemia history associated with the neurological complication.

Complement in paroxysmal nocturnal hemoglobinuria: exploiting our current knowledge to improve the treatment landscape

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare hematological disorder associated with an acquired deficiency in glycophosphatidylinositol-anchor biosynthesis that renders erythrocytes susceptible to complement attack. Intravascular hemolysis via the membrane attack complex is a clinical hallmark of the disease, and C5 blockade is currently the only approved treatment for PNH. However, residual anemia is an emerging observation for many PNH patients receiving anti-C5 treatment. A range of complement-targeted therapeutic approaches, encompassing surface-directed inhibition of C3 convertases, blockade of membrane attack complex assembly or C3 interception using peptidic inhibitors, has yielded promising results and offers leverage for even more effective treatment of PNH. This article discusses recent advances in this rapidly evolving field, integrating critical perspectives from preclinical PNH models and diverse complement modulation strategies with genetic insights and therapy response profiles. It also evaluates the relative efficacy, limitations and benefits afforded by C3 or C5 inhibition in the context of PNH therapeutics.

Efficacy and safety of eculizumab in children and adolescents with paroxysmal nocturnal hemoglobinuria

BACKGROUND

Paroxysmal nocturnal hemoglobinuria (PNH) is rare in children, but represents a similarly serious and chronic condition as in adults. Children with PNH frequently experience complications of chronic hemolysis, recurrent thrombosis, marrow failure, serious infections, abdominal pain, chronic fatigue, and decreased quality of life with reduced survival. The terminal complement inhibitor eculizumab is proven to be effective and safe in adults and approved by the FDA for treatment of PNH.

PROCEDURE

This 12-week, open-label, multi-center phase I/II study evaluated pharmacokinetics, pharmacodynamics, efficacy, and safety in seven children with PNH 11-17 years of age. Eculizumab was intravenously administered at 600 mg weekly for 4 weeks, 900 mg in week 5, and 900 mg every 2 weeks thereafter (http://clinicaltrials.gov NCT00867932).

RESULTS

Eculizumab therapy resulted in complete and sustained inhibition of hemolysis in all participants with a reduction of lactate dehydrogenase to normal levels. All hematological parameters stabilized. No definitive, study drug-related adverse events were observed. Only one severe SAE of hospitalization due to aplastic anemia occurred, which was not study drug-related.

CONCLUSION

Eculizumab appears to be a safe and effective therapy for children with PNH.

Paroxysmal nocturnal hemoglobinuria presenting as cerebral venous sinus thrombosis: a case report

Paroxysmal Nocturnal Hemoglobinuria (PNH) is a rare type of acquired hemolytic anemia that is frequently associated with thrombophilia. It may rarely present with cerebral venous sinus thrombosis, which manifests clinically with signs of raised intracranial pressure and requires lifelong anticoagulation therapy. One such rare presentation was seen in a 28 years old male who had history of recurrent episodes of passing red colored urine and this time presented with severe headache. He was diagnosed to have cerebral venous sinus thrombosis and on further workup was found to be suffering from PNH.

Opportunity cost of funding drugs for rare diseases: the cost-effectiveness of eculizumab in paroxysmal nocturnal hemoglobinuria

BACKGROUND

Both ethical and economics concerns have been raised with respect to the funding of drugs for rare diseases. This article reports both the cost-effectiveness of eculizumab for the treatment of paroxysmal nocturnal hemoglobinuria (PNH) and its associated opportunity costs.

METHODS

Analysis compared eculizumab plus current standard of care v. current standard of care from a publicly funded health care system perspective. A Markov model covered the major consequences of PNH and treatment. Cost-effectiveness was assessed in terms of the incremental cost per life year and per quality-adjusted life year (QALY) gained. Opportunity costs were assessed by the health gains foregone and the alternative uses for the additional resources.

RESULTS

Eculizumab is associated with greater life years (1.13), QALYs (2.45), and costs (CAN$5.24 million). The incremental cost per life year and per QALY gained is CAN$4.62 million and CAN$2.13 million, respectively. Based on established thresholds, the opportunity cost of funding eculizumab is 102.3 discounted QALYs per patient funded. Sensitivity and subgroup analysis confirmed the robustness of the results. If the acquisition cost of eculizumab was reduced by 98.5%, it could be considered cost-effective.

LIMITATIONS

The nature of rare diseases means that data are often sparse for the conduct of economic evaluations. When data were limited, assumptions were made that biased results in favor of eculizumab.

CONCLUSIONS

This study demonstrates the feasibility of conducting economic evaluations in the context of rare diseases. Eculizumab may provide substantive benefits to patients with PNH in terms of life expectancy and quality of life but at a high incremental cost and a substantial opportunity cost. Decision makers should fully consider the opportunity costs before making positive reimbursement decisions.