Safety of current treatments for paroxysmal nocturnal hemoglobinuria.

Introduction: Eculizumab, which is indicated to treat patients with paroxysmal nocturnal hemoglobinuria (PNH), is proven to decrease intravascular hemolysis and thrombosis and improve survival. Ravulizumab is a long-acting, second-generation complement component 5 (C5) inhibitor designed to alleviate the burden of the eculizumab treatment schedule and reduce the frequency of breakthrough hemolysis. As the clinical benefits of these treatments have been emphasized, their safety also should be considered. Areas covered: This article reviews safety data for the current approved PNH treatments from published articles about eculizumab and ravulizumab in patients with PNH. Special settings (pregnancy, pediatrics, long-term safety of continued eculizumab treatment, and extravascular hemolysis) are also discussed. Expert opinion: In phase 3 trials, eculizumab and ravulizumab were found to be safe and well tolerated. In addition, 10 years of experience with eculizumab provided evidence that mitigates initial concerns about infectious events. However, to minimize meningococcal infections, vaccination and close monitoring remain essential. Because extravascular hemolysis limits eculizumab efficacy in some patients, continued investigation of proximal complement inhibitors is warranted to obviate this mechanism. Long-term safety data for ravulizumab treatment are needed.

Paroxysmal nocturnal hemoglobinuria: role of the complement system, pathogenesis, and pathophysiology.

The complement system is part of the innate immune response system, which comprises more than 50 distinct plasma and serum proteins that interact to opsonize pathogens (i.e., mark pathogens for destruction) and induce inflammatory responses to fight infection. The role of the complement system is 2-fold: immune surveillance and host defense. Paroxysmal nocturnal hemoglobinuria (PNH) is a rare, chronic, acquired, hematologic disease caused by somatic mutations in the gene PIGA in the hematopoietic stem cells. These stem cells produce abnormal clone blood cells that lack the complement regulatory proteins CD55 and CD59, causing the body to recognize these otherwise healthy red blood cells as damaged. The complement system destroys cells without these protective proteins, resulting in general hemolysis. PNH is characterized by fatigue; hemolytic anemia that can be severe and debilitating; increased lactic dehydrogenase level, reticulocyte count, and bilirubin level; propensity for thrombotic events; and renal dysfunction. Epidemiologic data, while sparse, suggest that an estimated 5,000-6,000 individuals in the United States are affected by PNH. If left untreated, PNH has a 10-year mortality rate of 29%, although the natural history of this disease has been recently altered by the introduction of complement inhibitors for the treatment of PNH. DISCLOSURES: This research was developed under a research contract between RTI Health Solutions and Apellis Pharmaceuticals and was funded by Apellis Pharmaceuticals. Bektas, Copley-Merriman, and Khan are employees of RTI Health Solutions. Sarda is an employee of Apellis Pharmaceuticals. Shammo consults for Apellis Pharmaceuticals.

Modeling the activation of the alternative complement pathway and its effects on hemolysis in health and disease.

The complement system is a powerful mechanism of innate immunity poised to eliminate foreign cells and pathogens. It is an intricate network of >35 proteins, which, once activated, leads to the tagging of the surface to be eliminated, produces potent chemoattractants to recruit immune cells, and inserts cytotoxic pores into nearby lipid surfaces. Although it can be triggered via different pathways, its net output is largely based on the direct or indirect activation of the alternative pathway. Complement dysregulation or deficiencies may cause severe pathologies, such as paroxysmal nocturnal hemoglobinuria (PNH), where a lack of complement control proteins leads to hemolysis and life-threatening anemia. The complexity of the system poses a challenge for the interpretation of experimental data and the design of effective pharmacological therapies. To address this issue, we developed a mathematical model of the alternative complement pathway building on previous modelling efforts. The model links complement activation to the hemolytic activity of the terminal alternative pathway, providing an accurate description of pathway activity as observed in vitro and in vivo, in health and disease. Through adjustment of the parameters describing experimental conditions, the model was capable of reproducing the results of an array of standard assays used in complement research. To demonstrate its clinical applicability, we compared model predictions with clinical observations of the recovery of hematological biomarkers in PNH patients treated with the complement inhibiting anti-C5 antibody eculizumab. In conclusion, the model can enhance the understanding of complement biology and its role in disease pathogenesis, help identifying promising targets for pharmacological intervention, and predict the outcome of complement-targeting pharmacological interventions.

Analysis of clinical characteristics of 92 patients with paroxysmal nocturnal hemoglobinuria: A single institution experience in China.

OBJECTIVES: We performed a retrospective analysis to investigate the clinical characteristics and therapeutic strategies of Chinese paroxysmal nocturnal hemoglobinuria (PNH) patients, and assessed the efficacy and safety of glucocorticoid in PNH patients. METHODS: The clinical data of 92 PNH cases in our hospital were analyzed, including clinical manifestation, laboratory examination, treatment efficacy, and survival. RESULTS: The main clinical manifestations of these patients included hemoglobinuria, anemia, fatigue, dyspnea, headache, abdominal pain, and erectile dysfunction. Glucocorticoid is still the first-line treatment for PNH patients to control hemolytic attack, and the short-term remission rate (12 months) is 79.01% (64/81). Meanwhile, the overall survival (OS) of 10 years after diagnosis was estimated as 70.77% (46/65). Moreover, Cox proportional risk model for multivariate analysis showed that the increase in LDH multiple, thrombosis complications, and complicated with bone marrow failure were the independent adverse prognostic factors affecting the survival of PNH patients. CONCLUSION: Paroxysmal nocturnal hemoglobinuria patients in mainland China have various clinical features, while lower incidences of thrombosis and renal damage. Thrombosis and bone marrow failure are two complications with worse prognosis.

Pediatric Hepatic Venous Outflow Tract Obstruction: Experience from a Transplant Center.

We performed a review of case records of children diagnosed with hepatic venous outflow tract obstruction at our center in last 10 years. Out of 11 cases identified, 6 had variable blocks in the hepatic venous system and 4 had combined hepatic venous and inferior vena cava (IVC) block. One child with paroxysmal nocturnal hemoglobinuria (PNH) had isolated IVC involvement. Angioplasty was attempted in 3 patients; among them 2 had successful outcome. Seven children with advanced liver disease underwent transplantation, which was successful in six. With availability of modalities like interventional radiology and transplantation, the overall prognosis of hepatic venous outflow tract obstruction seems to be good when managed in a well-equipped center.

Complement and Coagulation: Cross Talk Through Time.

Two complex protein defense systems-complement and coagulation-are based on amplifying enzyme cascades triggered by specific local stimuli. Excess systemic activation of either system is pathologic and is normally prevented by a family of regulatory proteins. The 2 systems are ancient biological processes which share a common origin that predates vertebrate evolution. Recent research has uncovered multiple opportunities for cross talk between complement and coagulation including proteins traditionally viewed as coagulation factors that activate and regulate complement, and proteins traditionally seen as part of the complement system that participate in coagulation. Ten examples of cross talk between the 2 systems are described. The mutual engagement of both systems is increasingly recognized to occur in human diseases. Three conditions-paroxysmal nocturnal hemoglobinuria, atypical hemolytic uremic syndrome, and the antiphospholipid syndrome-provide examples of the importance of interactions between complement and coagulation in human biology. A better understanding of the mutual engagement of these 2 ancient defense systems is expected to result in improved diagnostics and new treatments for systemic diseases.

Comparative study on baseline clinical characteristics of Asian versus non-Asian patients with paroxysmal nocturnal hemoglobinuria.

A difference in clinical manifestations of paroxysmal nocturnal hemoglobinuria (PNH) among different races has been suggested. The aim of this study was to clarify whether the clinical characteristics of patients with PNH in the International PNH Registry differ by ethnic background. Patients, who were eculizumab naïve at baseline and had ≥ 1% PNH clone size, were eligible for this analysis. Totally, 1793 patients were enrolled and divided into two cohorts, Asian (N = 246) and non-Asian (N = 1547). The Asian cohort was further divided into Asians in Asia cohort (N = 202) and Asians in non-Asia cohort (N = 44), based on geographical region. The Asian cohort had significantly higher PNH clone size in granulocytes, higher lactate dehydrogenase levels, and lower hemoglobin levels. However, the frequencies of symptoms including abdominal pain, backache, easy bleeding, fatigue and headache at baseline were significantly lower in the Asian cohort. The proportion of patients with a history of thromboembolism (TE) was significantly lower in the Asian than in the non-Asian cohort (3.6% vs. 8.9%, P < 0.01); however, there was no difference between Asians in Asia and Asians in non-Asia (3.3% vs. 4.9%, P = 0.61). These findings suggested that genetic factors may play a stronger role in developing TE than lifestyle factors in PNH patients.

Spontaneous Remission in Paroxysmal Nocturnal Hemoglobinuria-Return to Health or Transition Into Malignancy?

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired syndrome characterized by intravascular hemolysis, thrombosis, and bone marrow failure. The disease is caused by a mutation in the PIG-A gene that leads to the lack of glycosylphosphatidylinositol-anchored complement regulatory molecules CD55 and CD59 on affected blood cell surfaces. In previous studies, spontaneous clinical remissions have been described. The disease manifestations are very heterogeneous, and we wanted to examine if true remissions and disappearance of the clone occur. In a follow-up of a nation-wide cohort of 106 Finnish patients with a PNH clone, we found six cases, where the clone disappeared or was clearly diminished. Two of the patients subsequently developed leukemia, while the other four are healthy and in clinical remission. According to our data, spontaneous remissions are not as frequent as described earlier. Since the disappearance of the PNH cell clone may indicate either a favorable or a poor outcome-remission or malignancy-careful clinical monitoring in PNH is mandatory. Nevertheless, true remissions occur, and further studies are needed to understand the immunological background of this phenomenon and to obtain a better understanding of the natural history of the disease.

Evolutionary dynamics of paroxysmal nocturnal hemoglobinuria.

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired clonal blood disorder characterized by hemolysis and a high risk of thrombosis, that is due to a deficiency in several cell surface proteins that prevent complement activation. Its origin has been traced to a somatic mutation in the PIG-A gene within hematopoietic stem cells (HSC). However, to date the question of how this mutant clone expands in size to contribute significantly to hematopoiesis remains under debate. One hypothesis posits the existence of a selective advantage of PIG-A mutated cells due to an immune mediated attack on normal HSC, but the evidence supporting this hypothesis is inconclusive. An alternative (and simpler) explanation attributes clonal expansion to neutral drift, in which case selection neither favours nor inhibits expansion of PIG-A mutated HSC. Here we examine the implications of the neutral drift model by numerically evolving a Markov chain for the probabilities of all possible outcomes, and investigate the possible occurrence and evolution, within this framework, of multiple independently arising clones within the HSC pool. Predictions of the model agree well with the known incidence of the disease and average age at diagnosis. Notwithstanding the slight difference in clonal expansion rates between our results and those reported in the literature, our model results lead to a relative stability of clone size when averaging multiple cases, in accord with what has been observed in human trials. The probability of a patient harbouring a second clone in the HSC pool was found to be extremely low ([Formula: see text]). Thus our results suggest that in clinical cases of PNH where two independent clones of mutant cells are observed, only one of those is likely to have originated in the HSC pool.

ERCC6L2-associated inherited bone marrow failure syndrome.

BACKGROUND: ERCC6L2-associated disorder has recently been described and only five patients were reported so far. The described phenotype included bone marrow, cerebral, and craniofacial abnormalities. The aim of this study was to further define the genetic and phenotypic spectrum of the disorder by summarizing the five published cases and an additional case that we identified through whole-exome sequencing performed at the University of Toronto. METHODS: Clinical data was extracted from the Canadian Inherited Marrow Failure Registry. Whole exome sequencing was performed to identify causative mutations. RESULTS: All six cases had homozygous truncating mutations either at or upstream of the helicase domain of ERCC6L2. All patients displayed bone marrow failure, learning or developmental delay and microcephaly. Our patient was unique in displaying features of cerebellar disease, including ataxia and dysmetria as well as an interval deterioration of the corpus callosum and generalized volume loss on MRI. Another unique feature of our patient was retinal dystrophy with macular involvement. Along with one other patient, our patient displayed craniofacial abnormalities by presenting with low-set prominent ears, a pointed prominent chin, and deep-set eyes. Leukemia is common among patients with inherited bone marrow failure, but thus far, none of the patients have developed this complication. CONCLUSIONS: ERCC6L2-associated disorder is a multisystem disorder. The phenotype spectrum includes bone marrow failure, cerebral, and craniofacial abnormalities, as well as cerebellar and retinal abnormalities.

Refining the phenotype associated with biallelic DNAJC21 mutations.

Inherited bone marrow failure syndromes (IBMFS) are caused by mutations in genes involved in genomic stability. Although they may be recognized by the association of typical clinical features, variable penetrance and expressivity are common, and clinical diagnosis is often challenging. DNAJC21, which is involved in ribosome biogenesis, was recently linked to bone marrow failure. However, the specific phenotype and natural history remain to be defined. We correlate molecular data, phenotype, and clinical history of 5 unreported affected children and all individuals reported in the literature. All patients present features consistent with IBMFS: bone marrow failure, growth retardation, failure to thrive, developmental delay, recurrent infections, and skin, teeth or hair abnormalities. Additional features present in some individuals include retinal abnormalities, pancreatic insufficiency, liver cirrhosis, skeletal abnormalities, congenital hip dysplasia, joint hypermobility, and cryptorchidism. We suggest that DNAJC21-related diseases constitute a distinct IBMFS, with features overlapping Shwachman-Diamond syndrome and Dyskeratosis congenita, and additional characteristics that are specific to DNAJC21 mutations. The full phenotypic spectrum, natural history, and optimal management will require more reports. Considering the aplastic anemia, the possible increased risk for leukemia, and the multisystemic features, we provide a checklist for clinical evaluation at diagnosis and regular follow-up.

Renal involvement in paroxysmal nocturnal hemoglobinuria: an update on clinical features, pathophysiology and treatment.

OBJECTIVES: The present review summarizes the available knowledge regarding acute and chronic kidney dysfunction in patients with paroxysmal nocturnal hemoglobinuria (PNH) focusing on its clinical features, pathophysiology and treatment. METHODS: A thorough PubMed search was performed using as main keywords: 'paroxysmal nocturnal hemoglobinuria', 'acute kidney injury', 'chronic kidney disease' and 'eculizumab'. RESULTS: PNH's etiopathogenesis is based on acquired mutations that lead to the reduction or absence of CD55 and CD59 complement regulators, which are responsible for some of the disease's major clinical features, like intravascular hemolysis, cytopenias and thrombosis. PNH is often underdiagnosed, mainly due to its occasional mild manifestations and to its ability to mimic other severe clinical conditions. Various mechanisms have been proposed for the kidney damage attributed to the release of cell-free heme and free iron, including inflammatory response, oxidative stress, nitric oxide depletion, renal ischemia, membrane damage and apoptosis. Eculizumab, a terminal complement inhibitor, provides a safe and effective treatment option, especially when it is initiated early in the presence of kidney damage. DISCUSSION: Kidney injury is a poorly investigated clinical feature of PNH that affects a significant portion of patients. Increased awareness is needed by physicians to recognize the early signs and symptoms of acute and chronic renal insufficiency, so as to initiate the necessary therapy. It is also important to re-evaluation of PNH-specific treatments during the course of the disease. CONCLUSION: Understanding the difficult but at the same time impressive mechanisms behind PNH remains a challenge for treating physicians.

Screening and diagnostic clinical algorithm for paroxysmal nocturnal hemoglobinuria: Expert consensus.

OBJECTIVE: Paroxysmal nocturnal hemoglobinuria (PNH) is a severe, life-threatening disorder for which early diagnosis is essential. However, given the rarity of the disease and non-specificity of symptoms, correct diagnosis may be delayed or missed. While various hematologic guidelines note common signs and symptoms associated with PNH, international expert consensus based on real-world clinical experience and an actionable algorithm for non-specialists to facilitate screening and diagnosis are lacking. The objective of the study is to develop a clinically relevant, consensus-driven screening and diagnostic algorithm on PNH for non-specialist clinicians. METHODS: An expert advisory committee of PNH experts from North America, Europe, and Japan was convened, and a modified Delphi methodology was employed to develop an algorithm to assist non-specialist clinicians in identifying signs/symptoms of PNH and conducting appropriate differential diagnosis. Twelve globally representative Delphi panelists with clinical expertise in PNH were identified and recruited. Panelists provided their differential diagnosis for 5 blinded case studies via 2 rounds of online questionnaires. Responses mentioned by >50% of panelists in the first round were included in the second-round questionnaire, at which point consensus was attained if >80% of panelists agreed on an approach. RESULTS: Consensus was reached for 95% of screening and diagnostic decision points and 90% of tests required at decision points. CONCLUSION: These results facilitated development of a consensus-based, clinically relevant algorithm, providing non-specialist clinicians with actionable guidance on PNH screening and diagnosis.

Hematopoietic development: a gap in our understanding of inherited bone marrow failure.

Inherited bone marrow failure syndromes (IBMFS) represent a heterogeneous group of multisystem disorders that typically present with cytopenia in early childhood. Efforts to understand the underlying hematopoietic stem cell (HSC) losses have generally focused on postnatal hematopoiesis. However, reflecting the role of many of the involved genes in core cellular functions and the diverse nonhematologic abnormalities seen in patients at birth, studies have begun to explore IBMFS manifestations during fetal development. Here, I consider the current evidence for fetal deficits in the HSC pool and highlight emerging concepts regarding the origins and unique pathophysiology of hematopoietic failure in IBMFS.

Bone marrow failure syndrome caused by homozygous frameshift mutation in the ERCC6L2 gene.

Inherited bone marrow failure syndromes (IBMFS) are group of disorders that lead to inadequate production of blood cells. Mutations in genes involved in telomere maintenance, DNA repair, and the cell cycle cause IBMFS. ERCC6L2 gene mutations have been associated with bone marrow failure that includes developmental delay and microcephaly. We report 2 cases of bone marrow failure with no extra-hematopoietic manifestations in patients from unrelated families with a homozygous truncating mutation in ERCC6L2. Bone marrow failure without developmental delay or microcephaly with ERCC6L2 mutation has not been previously described.

The Mechanism of Mitochondria-Mediated Pathway in the Apoptosis of Platelets in Immune-Induced Bone Marrow Failure.

Excessive platelet apoptosis is one of the pathogenic causes of immune-induced bone marrow failure (BMF). The aim of the present study was to explore the role of mitochondria-mediated pathway in the apoptosis of platelets in immune-induced BMF. An immune-induced BMF model was established in mice, which were randomly divided into three groups: normal control (CTL) group, BMF group and cyclosporine (CSA) group (n = 10 in each group). Mice were given 0.027 g/kg CSA daily in the CSA group. Platelet count (PLT), mitochondrial transmembrane potential (ΔΨm), cytochrome C (CytC), phosphatidylserine (PS), calcium ion (Ca²âº) and expression of proteins of the mitochondrial apoptotic pathway, including Bak, Bax, caspase-3, caspase-8 and caspase-9, was examined and compared. Compared with the CTL group, the BMF group had significantly a lower level of PLC and ΔΨm, but higher levels of CytC, PS, Ca²âº and higher expression levels of Bak, Bax, cleaved caspase-9 and cleaved caspase-3 (P < 0.05). CSA restored the above changes in the BMF model (P < 0.05). Further studies showed that intravenous injection of the caspase-9 inhibitor Z-LE(OMe)HD(OMe)-fluoromethylketone (FMK) into the mice could significantly inhibit apoptosis of the platelets and the effect of CSA treatment when compared to the BMF group, and exerted a better protective effect from apoptosis if the caspase-9 inhibitor was combined with the CSA treatment. These results revealed that platelet apoptosis may play an important role in the reduction of platelet of immune-induced BMF probably through the mitochondrial pathway.

Long-term systolic function in children and young adults after hematopoietic stem cell transplant.

Congestive heart failure and subclinical left ventricular systolic dysfunction (LVSD) affect long-term survivors of hematopoietic stem cell transplant (HSCT). Echocardiographic measurements of global longitudinal and circumferential strain have shown promise in identifying subclinical LVSD in cancer survivors. We analyzed echocardiograms in 95 children and young adults with malignancies or bone marrow failure syndromes performed before HSCT and 1-6 years after HSCT. We additionally measured the biomarkers soluble suppression of tumorigenicity-2 (sST-2) and cardiac troponin-I (cTn-I) in the same children through 49 days post HSCT. Ejection fraction (EF) after HSCT was unchanged from baseline (baseline: z-score -0.73 vs long-term follow up: -0.44, P=0.11). Global longitudinal strain was unchanged from baseline (-20.66 vs -20.74%, P=0.90) as was global circumferential strain (-24.3 vs -23.5%, P=0.32). Levels of sST-2 were elevated at all time points compared with baseline samples and cTn-I was elevated at days 14 and 28. Cardiac biomarkers at any time point did not correlate with long-term follow-up EF. In children and young adult survivors of HSCT, EF was unchanged in the first years after HSCT. Elevation in cardiac biomarkers occurring after HSCT suggest subclinical cardiac injury occurs in many patients and long-term monitoring for LVSD should continue.