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

Complement Inhibition in Paroxysmal Nocturnal Hemoglobinuria (PNH): A Systematic Review and Expert Opinion from Central Europe on Special Patient Populations

INTRODUCTION

Hemolysis in paroxysmal nocturnal hemoglobinuria (PNH) is complement-mediated due to the lack of complement inhibitors in the hemopoietic cell membranes, making complement inhibition the best approach to manage PNH. Three complement inhibitors are approved by the European Medicines Agency as targeted therapy for PNH: eculizumab and ravulizumab, two humanized monoclonal antibodies targeting the same complement 5 (C5) epitope, approved in 2007 and 2019, respectively, and the more recently approved cyclic peptide, the complement 3 (C3) inhibitor pegcetacoplan. Although national and international PNH treatment guidelines exist, they do not take into consideration the latest clinical trial evidence. Given the lack of evidence-based data for some clinical situations encountered in real life, we identified specific populations of patients who may benefit from switching to proximal C3 from terminal C5 inhibition.

METHODS

The expert recommendations presented here were created using a Delphi-like process by a group of expert PNH specialists across Central Europe. Based on an initial advisory board meeting discussion, recommendations were prepared and reviewed as part of a Delphi survey to test agreement.

RESULTS

Using a systematic approach, literature databases were searched for relevant studies, and 50 articles were reviewed by the experts and included as supporting evidence.

CONCLUSION

Implementation of these recommendations uniformly across healthcare institutions will promote the best use of complement inhibition in managing PNH, and has the potential to positively impact patient outcomes in Central Europe and worldwide.

Pegcetacoplan for Treating Paroxysmal Nocturnal Haemoglobinuria: An Evidence Review Group Perspective of a NICE Single Technology Appraisal

As part of the Single Technology Appraisal (STA) process, the UK National Institute for Health and Care Excellence (NICE) invited Apellis Pharmaceuticals/Sobi to submit evidence for the clinical and cost effectiveness of pegcetacoplan versus eculizumab and pegcetacoplan versus ravulizumab for treating paroxysmal nocturnal haemoglobinuria (PNH) in adults whose anaemia is uncontrolled after treatment with a C5 inhibitor. The Liverpool Reviews and Implementation Group at the University of Liverpool was commissioned as the Evidence Review Group (ERG). The company pursued a low incremental cost-effectiveness ratio (ICER) Fast Track Appraisal (FTA). This was a form of STA processed in a shorter time frame and designed for technologies with company base-case ICER < £10,000 per quality-adjusted life-year (QALY) gained and most plausible ICER < £20,000 per QALY gained. This article summarises the ERG's review of the company's evidence submission, and the NICE Appraisal Committee's (AC's) final decision. The company presented clinical evidence from the PEGASUS trial that assessed the efficacy of pegcetacoplan versus eculizumab. At Week 16, patients in the pegcetacoplan arm had statistically significantly greater change from baseline in haemoglobin levels and a higher rate of transfusion avoidance than patients in the eculizumab arm. Using the PEGASUS trial and Study 302 data (a non-inferiority trial that assessed ravulizumab versus eculizumab), the company conducted an anchored matching-adjusted indirect comparison (MAIC) to indirectly estimate the efficacy of pegcetacoplan versus ravulizumab. The company identified key differences between trial designs and populations that could not be adjusted for using anchored MAIC methods. The company and ERG agreed that the anchored MAIC results were not robust and should not inform decision making. In the absence of robust indirect estimates, the company assumed that ravulizumab had equivalent efficacy to eculizumab in the PEGASUS trial population. Results from the company base-case cost-effectiveness analysis showed that treatment with pegcetacoplan dominated eculizumab and ravulizumab. The ERG considered that the long-term effectiveness of pegcetacoplan was uncertain and ran a scenario assuming that after 1 year the efficacy of pegcetacoplan would be the same as eculizumab; treatment with pegcetacoplan continued to dominate eculizumab and ravulizumab. The AC noted that treatment with pegcetacoplan had lower total costs than treatment with eculizumab or ravulizumab because it is self-administered and reduces the need for blood transfusions. If the assumption that ravulizumab has equivalent efficacy to eculizumab does not hold, then this will affect the estimate of the cost effectiveness of pegcetacoplan versus ravulizumab; however, the AC was satisfied that the assumption was reasonable. The AC recommended pegcetacoplan as an option for the treatment of PNH in adults who have uncontrolled anaemia despite treatment with a stable dose of a C5 inhibitor for ≥ 3 months. Pegcetacoplan was the first technology recommended by NICE via the low ICER FTA process.

Management of infection in PNH patients treated with eculizumab or other complement inhibitors: Unmet clinical needs

This article presents the results of group discussion among an ad hoc constituted panel of experts aimed at identifying and addressing unmet clinical needs (UCNs) in the management of infectious risk associated with eculizumab or new terminal complement inhibitors (CIs) in paroxysmal nocturnal hemoglobinuria (PNH). With the Delphi technique, the most clinically relevant UCNs in PNH patients candidate to or on terminal CI were selected. They resulted to be: optimizing the infection prevention measures; developing non pharmacological infectious risk-mitigation strategies; improving the management of disease exacerbation during infectious complications. For each of these issues consensus opinions were provided and, when appropriate, proposals for advancement in clinical practice were addressed. The hope is that this comprehensive overview will serve to improve the practice of CIs therapy and inform the design and implementation of new studies in the field.

A phase III, randomised, double-blind, multi-national clinical trial comparing SB12 (proposed eculizumab biosimilar) and reference eculizumab in patients with paroxysmal nocturnal haemoglobinuria

Treatment of paroxysmal nocturnal haemoglobinuria (PNH) includes the monoclonal antibody eculizumab. This randomised, double-blind, multi-national cross-over Phase III study in PNH patients aimed to demonstrate the equivalence of the proposed eculizumab biosimilar SB12 and reference eculizumab (Soliris, ECU). PNH patients with lactate dehydrogenase (LDH) ≥1·5× upper limit of normal were randomised into treatment sequences SB12-ECU or ECU-SB12. Four weekly infusions of 600 mg eculizumab were followed by fortnightly infusions of 900 mg until week 50 (ECU/SB12 cross-over at week 26). Primary endpoints were LDH at week 26 and the time-adjusted area under the effect curve (AUEC) of LDH over weeks 14‒26 and 40‒52. Among 46 patients (92%) who completed the study, the least squares mean (LSM) difference in LDH at week 26 (34·48; 95% confidence interval [CI] -47·66‒116·62 U/l) and geometric LSM ratio of time-adjusted AUEC of LDH (1·08; 90% CI 0·95‒1·23) were within pre-defined equivalence margins. Mean numbers of transfused red blood cell units, other secondary endpoints, pharmacokinetics, and pharmacodynamics were comparable. No patients developed anti-drug antibodies. Treatment-emergent adverse events were reported in 72% and 68% of patients in the SB12 and ECU treatment groups, respectively. The results demonstrate equivalence of SB12 to ECU and support SB12-use in PNH patients.

Targeting the Complement-Sphingolipid System in COVID-19 and Gaucher Diseases: Evidence for a New Treatment Strategy

Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2)-induced disease (COVID-19) and Gaucher disease (GD) exhibit upregulation of complement 5a (C5a) and its C5aR1 receptor, and excess synthesis of glycosphingolipids that lead to increased infiltration and activation of innate and adaptive immune cells, resulting in massive generation of pro-inflammatory cytokines, chemokines and growth factors. This C5a-C5aR1-glycosphingolipid pathway- induced pro-inflammatory environment causes the tissue damage in COVID-19 and GD. Strikingly, pharmaceutically targeting the C5a-C5aR1 axis or the glycosphingolipid synthesis pathway led to a reduction in glycosphingolipid synthesis and innate and adaptive immune inflammation, and protection from the tissue destruction in both COVID-19 and GD. These results reveal a common involvement of the complement and glycosphingolipid systems driving immune inflammation and tissue damage in COVID-19 and GD, respectively. It is therefore expected that combined targeting of the complement and sphingolipid pathways could ameliorate the tissue destruction, organ failure, and death in patients at high-risk of developing severe cases of COVID-19.

Iptacopan monotherapy in patients with paroxysmal nocturnal hemoglobinuria: a 2-cohort open-label proof-of-concept study

Iptacopan (LNP023) is a novel, oral selective inhibitor of complement factor B under clinical development for paroxysmal nocturnal hemoglobinuria (PNH). In this ongoing open-label phase 2 study, PNH patients with active hemolysis were randomized to receive single-agent iptacopan twice-daily, at a dose of either 25 mg for 4 weeks followed by 100 mg for up to 2 years (cohort 1) or 50 mg for 4 weeks followed by 200 mg for up to 2 years (cohort 2). At the time of interim analysis, of 13 PNH patients enrolled, all 12 evaluable for efficacy achieved the primary endpoint of reduction in serum lactate dehydrogenase (LDH) levels by at least 60% by week 12 as compared to baseline; mean LDH levels dropped rapidly and durably, namely by 77% and 85% at week 2 and by 86% and 86% at week 12 in cohorts 1 and 2, respectively. Most patients achieved a clinically meaningful improvement in hemoglobin levels and all but one patient remained transfusion-free up to week 12. Other markers of hemolysis, including bilirubin, reticulocytes and haptoglobin, showed consistent improvements. No thromboembolic events were reported, and iptacopan was well tolerated, with no severe or serious adverse events reported up until the data cutoff. In addition to the previously reported beneficial effect of iptacopan add-on therapy to eculizumab, this study showed that iptacopan monotherapy in treatment-naïve PNH patients resulted in normalization of hemolytic markers and rapid transfusion-free improvement of hemoglobin levels in most patients. Registered at www.clinicaltrials.gov as NCT03896152.

Real-World Eculizumab Dosing Patterns Among Patients with Paroxysmal Nocturnal Hemoglobinuria in a US Population

Purpose

Current pharmacologic management of paroxysmal nocturnal hemoglobinuria (PNH) consists of C5 inhibitors, eculizumab and ravulizumab; however, because patients experience incomplete symptom control, off-label doses may be utilized. We conducted a retrospective, longitudinal cohort study of provider-based claims data to assess the real-world eculizumab dosing patterns in PNH patients.

Patients and Methods

Patients were ≥12 years, received ≥2 eculizumab infusions between January 1, 2015 and September 30, 2019, and had ≥3 months of continuous clinical activity prior to index. The index date was the first claim for eculizumab. Patients with ≥1 diagnosis of another indication for eculizumab were excluded. Treatment patterns including the proportion with high, label-recommended, and low dosages during induction (first 28 days) and maintenance (beginning day 29) phases were described. The proportion and time-to-first dose escalation, defined as an increase in dose or frequency of infusion, were assessed among a subset of patients (ie, escalation analysis cohort).

Results

A total of 707 patients were examined. Mean (standard deviation [SD]) starting dose was 862mg (412mg) and was higher than label-recommended 600mg for 64% of the patients. Mean (SD) dose per infusion was 859mg (391mg) during the induction phase; average dose was higher than label-recommended 600mg for 68%. Mean (SD) dose per infusion during the maintenance phase was 1005mg (335mg); average dose was higher than label-recommended 900mg for 43%. Dose escalation occurred in 40/121 escalation analysis cohort patients. Median time-to-first dose escalation was ~12 months.

Conclusion

Results suggest that deviations from label-recommended dosing patterns were common. Future budget impact assessments of eculizumab should account for real-world dosing patterns to comprehensively assess costs and benefits.

Rescue of Glycosylphosphatidylinositol-Anchored Protein Biosynthesis Using Synthetic Glycosylphosphatidylinositol Oligosaccharides

The attachment of proteins to the cell membrane using a glycosylphosphatidylinositol (GPI) anchor is a ubiquitous process in eukaryotic cells. Deficiencies in the biosynthesis of GPIs and the concomitant production of GPI-anchored proteins lead to a series of rare and complicated disorders associated with inherited GPI deficiencies (IGDs) in humans. Currently, there is no treatment for patients suffering from IGDs. Here, we report the design, synthesis, and use of GPI fragments to rescue the biosynthesis of GPI-anchored proteins (GPI-APs) caused by mutation in genes involved in the assembly of GPI-glycolipids in cells. We demonstrated that the synthetic fragments GlcNAc-PI (1), Man-GlcN-PI (5), and GlcN-PI with two (3) and three lipid chains (4) rescue the deletion of the GPI biosynthesis in cells devoid of the PIGA, PIGL, and PIGW genes in vitro. The compounds allowed for concentration-dependent recovery of GPI biosynthesis and were highly active on the cytoplasmic face of the endoplasmic reticulum membrane. These synthetic molecules are leads for the development of treatments for IGDs and tools to study GPI-AP biosynthesis.

Infectious Complications in Autoimmune Hemolytic Anemia

Autoimmune hemolytic anemia (AIHA) may be frequently challenged by infectious complications, mainly as a result of immunosuppressive treatments administered. Furthermore, infectious agents are known triggers of AIHA onset and relapse. Although being risk factors for mortality, infections are an underestimated issue in AIHA. This review will collect the available evidence on the frequency and type of infectious complications in AIHA, detailing the risk related to each treatment (i.e., steroids, rituximab, splenectomy, classic immunosuppressive agents, and new target drugs). Moreover, we will briefly discuss the infectious complications in AIHA secondary to other diseases that harbor an intrinsic infectious risk (e.g., primary immunodeficiencies, systemic autoimmune diseases, lymphoproliferative disorders, solid organ and hematopoietic stem cell transplants). Finally, viral and bacterial reactivations during immune suppressive therapies will be discussed, along with suggested screening and prophylactic strategies.

Small hepatic veins Budd-Chiari syndrome and paroxysmal nocturnal hemoglobinuria - The association of two rare entities: a case report

Small hepatic veins Budd-Chiari syndrome is a rare disorder characterized by hepatic venous outflow obstruction limited to the small intrahepatic veins, with normal appearance of the large hepatic veins at imaging. In this case only a liver biopsy can demonstrate the presence of a small vessels outflow block. Paroxysmal nocturnal haemoglobinuria (PNH) is one of the most severe acquired thrombophilic state and represents one of the main aetiological factors of Budd-Chiari syndrome. In patient affected by PNH with liver impairment and/or ascites, Budd-Chiari syndrome must be always taken into consideration and, if necessary, a liver biopsy performed to exclude the small hepatic veins involvement. We report a case of small hepatic veins Budd–Chiari syndrome secondary to paroxysmal nocturnal haemoglobinuria.

Preventing infectious complications when treating non-malignant immune-mediated hematologic disorders

Immunosuppressants, targeted antibody therapies, and surgical splenectomy are amongst the treatment choices for immune-mediated non-malignant hematologic disorders, with infection being the most common non-hematological adverse event from these therapies. Corticosteroids are associated with a length-of-treatment and dose-dependent risk for infection, including opportunistic infections. Screening and antimicrobial prophylaxis against tuberculosis, Strongyloides stercoralis, and Pneumocystis jirovecii pneumonia, are indicated in selected patients on steroids and with certain risk factors for infection. Rituximab is associated with hepatitis B virus reactivation. All patients planned to be started on rituximab should be screened for hepatitis B surface antigen and total core antibody, with antiviral prophylaxis given depending on test results. In eculizumab treated patients, immunization against meningococcal serogroups ACWY and B is recommended. In addition, some guidelines suggest antibiotic prophylaxis for the duration of eculizumab treatment. In splenectomized patients, counseling and immunization are cornerstones of infection prevention. Several federal and society guidelines about immunizations and prophylactic antimicrobial therapies for patients treated with various immunosuppressive agents exist and are summarized in this manuscript in a clinical-focused table. In addition, management suggestions are made where no formal guidelines exist.

Multi-component meningococcal serogroup B (MenB)-4C vaccine induces effective opsonophagocytic killing in children with a complement deficiency

Vaccination against meningococcal serogroup B is recommended for patients with a complement deficiency; however, although immunogenicity in this patient group has been shown, efficacy has not yet been established. In this study, we collected serum from children with a complement deficiency in the alternative pathway or in late terminal pathway before and after vaccination with multi-component meningococcal serogroup B (MenB)-4C. MenB-4C is a multi-component, protein-based vaccine against MenB consisting of factor H-binding protein, Neisserial heparin-binding protein, Neisserial adhesion A and outer membrane vesicles containing Porin A. We assessed the vaccine immunogenicity and vaccine-mediated protection by a whole cell enzyme-linked immunosorbent assay with Neisseria meningitidis serogroup B strains H44/76, 5/99 and NZ98/254, which shows that vaccination induced antibody titers against meningococcus. We show that the classical serum bactericidal activity assay with exogenous serum indicates the presence of vaccine-induced antibodies and capacity to activate complement-mediated pathogen lysis. However, in children with a late terminal pathway deficiency, no complement-mediated pathogen lysis was observed when autologous serum was applied in the serum bactericidal activity assay, demonstrating a lack of serum bactericidal activity in children with complement deficiencies. However, MenB-4C vaccination still induced effective complement-dependent opsonophagocytic killing against N. meningitidis serogroup B in reconstituted whole blood with autologous serum from children with an alternative pathway or late terminal pathway deficiency. These findings support the recommendation to vaccinate all complement-deficient children against MenB.

The Extended Use of Eculizumab in Pregnancy and Complement Activation⁻Associated Diseases Affecting Maternal, Fetal and Neonatal Kidneys-The Future Is Now?

Excessive complement activation is involved in the pathogenesis of many diseases and the kidney is an organ with particular susceptibility to complement-mediated injury. Apart from paroxysmal nocturnal hemoglobinuria (PNH) and atypical hemolytic uremic syndrome (aHUS), there are several other diseases with clear evidence of complement activation affecting both maternal and fetal kidneys during pregnancy and causing long-term adverse outcomes. Several novel drugs have been recently developed for blocking the complement cascade, including purified plasma proteins, new monoclonal antibodies, recombinant proteins, small molecules, and small interfering RNA agents. Eculizumab, the humanized monoclonal IgG2/4-antibody targeting C5 was approved by the United States Food and Drug Administration (FDA) and the European Medicines Agency (EMA) for treatment of two rare diseases: PNH in 2007 and aHUS in 2011. There is an increasing number of publications of successful use of eculizumab for off-label indications, e.g., in pregnant women with antiphospholipid syndrome, sickle-cell anemia, and HELLP syndrome. These severe diseases are associated with both high maternal and fetal morbidity and mortality rate and substantial prematurity. Eculizumab has considerably improved overall outcome of patients with PNH and aHUS, enabling safe pregnancy for many women. Prolongation of pregnancy and the use of eculizumab, even for only a few weeks, may protect not only maternal renal function, but also alleviate acute and long-term renal consequences of prematurity in offspring.

Differential miRNA expression profile and proteome in plasma exosomes from patients with paroxysmal nocturnal hemoglobinuria

Paroxysmal Nocturnal Hemoglobinuria (PNH) is a clonal disease of blood cells caused by the lack of glycosyl phosphatidyl inositol anchored proteins bound to the cell membrane. In consequence, erythrocytes lead to intravascular hemolysis upon complement activation, which promotes high risk of thrombosis, intravascular hemolytic anemia, and bone marrow failure in patients. The mechanisms of thrombosis in PNH are still poorly understood. Treatment with eculizumab reduces intravascular hemolysis and thrombotic risk, but not in all cases. Exosomes are extracellular vesicles released by cells and whose secretion is closely related to the inflammatory status. They participate in cell communication by activating signaling pathways and transferring genetic material and proteins to host cells. In consequence, exosomes may serve as surrogate biomarkers for the prognosis and/or diagnosis of a disease. Isolation of exosomes was carried out from healthy controls and from three groups of PNH patients, i.e. i) with no eculizumab treatment; ii) under treatment with eculizumab that have not suffered thrombosis; and iii) under treatment with eculizumab but that have suffered thrombosis. The miRNAome and proteome was analyzed using plasma focus miRNAs PCR panel and LC-MS analysis respectively. We found differential expression of miRNAs miR-148b-3p, miR-423-3p, miR29b-3p, miR15b-5p, let-7e-5p, miR126-3p, miR-125b-5p and miR-376c-3p as well as hemoglobin, haptoglobin, protein S and C4-binding protein in healthy controls vs PNH patients. Our results warrant further research and provide new information on the content of exosomes that could play a role in the hypercoagulable state in this disease.

A Single-Domain Antibody Targeting Complement Component C5 Acts as a Selective Inhibitor of the Terminal Pathway of the Complement System and Thus Functionally Mimicks the C-Terminal Domain of the Staphylococcus aureus SSL7 Protein

The complement system is an efficient anti-microbial effector mechanism. On the other hand abnormal complement activation is involved in the pathogenesis of multiple inflammatory and hemolytic diseases. As general inhibition of the complement system may jeopardize patient health due to increased susceptibility to infections, the development of pathway-specific complement therapeutics has been a long-lasting goal over the last decades. In particular, pathogen mimicry has been considered as a promising approach for the design of selective anti-complement drugs. The C-terminal domain of staphylococcal superantigen-like protein 7 (SSL7), a protein secreted by Staphylococcus aureus, was recently found to be a specific inhibitor of the terminal pathway of the complement system, providing selective inhibition of cell lysis mediated by the membrane attack complex (MAC). We describe here the selection by phage display of a humanized single-domain antibody (sdAb) mimicking the C-terminal domain of SSL7. The antibody, called sdAb_E4, binds complement C5 with an affinity in the low micromolar range. Furthermore, sdAb_E4 induces selective inhibition of MAC-mediated lysis, allowing inhibition of red blood cell hemolysis and inhibition of complement deposition on apopto-necrotic cells, while maintaining efficient bactericidal activity of the complement terminal pathway. Finally, we present preliminary results indicating that sdAb_E4 may also be efficient in inhibiting hemolysis of erythrocytes from patients with paroxysmal nocturnal hemoglobinuria. Our data provide a proof of concept for the design of a selective MAC inhibitor capable of retaining complement bacteriolytic activity and this study opens up promising perspectives for the development of an sdAb_E4-derived therapeutics with application in the treatment of complement-mediated hemolytic disorders.

Therapeutic challenges in pregnant women with paroxysmal nocturnal hemoglobinuria: A case report

INTRODUCTION

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare acquired disease, arising from the mutation of clonal hematopoietic stem cells, with an estimated incidence of 1 to 5 cases per million individuals. In pregnant women, adequate information regarding the prevalence of PNH is lacking, and its management has been a challenge because of the significant complications in this group. The condition is diagnosed based on clinical findings and laboratory tests. Eculizumab, the drug of choice for the treatment of PNH, reduces hemolysis and stabilizes hemoglobin levels, thereby decreasing the need for blood transfusions and improving the overall quality of life.

CASE PRESENTATION

A 38-year-old woman was diagnosed with PNH in 2007 and eculizumab therapy was initiated at the end of 2014. She became pregnant in September 2015 and presented various decompensations from forced reductions in therapy due to the nonavailability of eculizumab. The pregnancy was interrupted in week 35, but the well-being of the newborn was not compromised. The patient, however, had to remain hospitalized for resolution of acute kidney insufficiency, anemia, and intense hemolysis, which were reverted by means of intravenous hydration, transfusion of 10 packed red blood cell units, and eculizumab therapy.

CONCLUSION

The rarity of the disease and the lack of protocols for its management during pregnancy hampered the treatment of the patient. However, the symptoms were progressively treated as they appeared, based on laboratory tests since it was necessary to circumvent and handle the lack of eculizumab which was not readily available in Brazil's Public Health System.

Complement and Bacterial Infections: From Molecular Mechanisms to Therapeutic Applications

Complement is a complex protein network of plasma, and an integral part of the innate immune system. Complement activation results in the rapid clearance of bacteria by immune cells, and direct bacterial killing via large pore-forming complexes. Here we review important recent discoveries in the complement field, focusing on interactions relevant for the defense against bacteria. Understanding the molecular interplay between complement and bacteria is of great importance for future therapies for infectious and inflammatory diseases. Antibodies that support complement-dependent bacterial killing are of interest for the development of alternative therapies to treat infections with antibiotic-resistant bacteria. Furthermore, a variety of novel therapeutic complement inhibitors have been developed to prevent unwanted complement activation in autoimmune inflammatory diseases. A better understanding of how such inhibitors may increase the risk of bacterial infections is essential if such therapies are to be successful.

Diagnostic algorithm for lower-risk myelodysplastic syndromes

Rapid advances over the past decade have uncovered the heterogeneous genomic and immunologic landscape of myelodysplastic syndromes (MDS). This has led to notable improvements in the accuracy and timing of diagnosis and prognostication of MDS, as well as the identification of possible novel targets for therapeutic intervention. For the practicing clinician, however, this increase in genomic, epigenomic, and immunologic knowledge needs consideration in a "real-world" context to aid diagnostic specificity. Although the 2016 revision to the World Health Organization classification for MDS is comprehensive and timely, certain limitations still exist for day-to-day clinical practice. In this review, we describe an up-to-date diagnostic approach to patients with suspected lower-risk MDS, including hypoplastic MDS, and demonstrate the requirement for an "integrated" diagnostic approach. Moreover, in the era of rapid access to massive parallel sequencing platforms for mutational screening, we suggest which patients should undergo such analyses, when such screening should be performed, and how those data should be interpreted. This is particularly relevant given the recent findings describing age-related clonal hematopoiesis.

High sensitivity 8-color flow cytometry assay for paroxysmal nocturnal hemoglobinuria granulocyte and monocyte detections

Flow cytometry is the gold standard in diagnosis of paroxysmal nocturnal hemoglobinuria (PNH) by detecting the absence of glycol-phosphatidyl inositol (GPI)-linked protein expression on granulocyte and monocyte surfaces. However, the current assays are not optimized and require improvement, particularly in reducing background fluorescence and optimizing sensitivity and specificity. With more fluorochromes available and with advances in instrument engineering, rare populations may be identified with high sensitivity. The present study assessed an 8-color combination of comprehensive GPI-linked markers, namely fluorescein-labeled proaerolysin (FLAER), cluster of differentiation 157 (CD157), CD24 and CD14, and the lineage markers for granulocyte (CD15) and monocyte (CD64) cells to detect PNH clones. Additionally, to optimize the PNH flow assay, a 'dump' channel was used, comprised of CD5 and CD19, to exclude non-specific binding in order to reduce background. This method aimed to improve sensitivity and reduce the background to create an optimized PNH flow cocktail. The results demonstrated that the current 4-color PNH combination identifies a CD55^- and FLAER⁺ population that is not PNH clones. By contrast, the 8-color panel delineated PNH clones from both monocyte and granulocytes by using granulocyte antigen (CD15) and monocyte antigen (CD64) as a gating strategy. The sensitivity was 0.01% for granulocytes and 0.05% for monocytes with an acquisition of 100,000 monocyte and granulocyte events. The background on a normal whole blood sample was 0.00076% on monocytes and 0.00277% on granulocytes. Thus, overall, the 8-color PNH assay exhibited high levels of specificity and sensitivity. The 8-color combination facilitated the improvement and enhancement of sensitivity in PNH clone identification, and may provide a useful tool for pathologists in PNH diagnosis and for monitoring patients at risk of developing classical/hemolytic PNH, to enable treatment to be delivered promptly.

The MFHR1 Fusion Protein Is a Novel Synthetic Multitarget Complement Inhibitor with Therapeutic Potential

The complement system is essential for host defense, but uncontrolled complement system activation leads to severe, mostly renal pathologies, such as atypical hemolytic uremic syndrome or C3 glomerulopathy. Here, we investigated a novel combinational approach to modulate complement activation by targeting C3 and the terminal pathway simultaneously. The synthetic fusion protein MFHR1 links the regulatory domains of complement factor H (FH) with the C5 convertase/C5b-9 inhibitory fragment of the FH-related protein 1. In vitro, MFHR1 showed cofactor and decay acceleration activity and inhibited C5 convertase activation and C5b-9 assembly, which prevented C3b deposition and reduced C3a/C5a and C5b-9 generation. Furthermore, this fusion protein showed the ability to escape deregulation by FH-related proteins and form multimeric complexes with increased inhibitory activity. In addition to substantially inhibiting alternative and classic pathway activation, MFHR1 blocked hemolysis mediated by serum from a patient with aHUS expressing truncated FH. In FH-/- mice, MFHR1 administration augmented serum C3 levels, reduced abnormal glomerular C3 deposition, and ameliorated C3 glomerulopathy. Taking the unique design of MFHR1 into account, we suggest that the combination of proximal and terminal cascade inhibition together with the ability to form multimeric complexes explain the strong inhibitory capacity of MFHR1, which offers a novel basis for complement therapeutics.

Optimization of capillary zone electrophoresis for charge heterogeneity testing of biopharmaceuticals using enhanced method development principles

CZE is a well-established technique for charge heterogeneity testing of biopharmaceuticals. It is based on the differences between the ratios of net charge and hydrodynamic radius. In an extensive intercompany study, it was recently shown that CZE is very robust and can be easily implemented in labs that did not perform it before. However, individual characteristics of some examined proteins resulted in suboptimal resolution. Therefore, enhanced method development principles were applied here to investigate possibilities for further method optimization. For this purpose, a high number of different method parameters was evaluated with the aim to improve CZE separation. For the relevant parameters, design of experiments (DoE) models were generated and optimized in several ways for different sets of responses like resolution, peak width and number of peaks. In spite of product specific DoE optimization it was found that the resulting combination of optimized parameters did result in significant improvement of separation for 13 out of 16 different antibodies and other molecule formats. These results clearly demonstrate generic applicability of the optimized CZE method. Adaptation to individual molecular properties may sometimes still be required in order to achieve optimal separation but the set screws discussed in this study [mainly pH, identity of the polymer additive (HPC versus HPMC) and the concentrations of additives like acetonitrile, butanolamine and TETA] are expected to significantly reduce the effort for specific optimization.

Efficacy of eculizumab in paroxysmal nocturnal hemoglobinuria patients with or without aplastic anemia: prospective study of a Korean PNH cohort

BACKGROUND

Patients with paroxysmal nocturnal hemoglobinuria (PNH) often have concurrent aplastic anemia (AA). This study aimed to determine whether eculizumab-treated patients show clinical benefit regardless of concurrent AA.

METHODS

We analyzed 46 PNH patients ≥18 years of age who were diagnosed by flow cytometry and treated with eculizumab for more than 6 months in the prospective Korean PNH registry. Patients were categorized into two groups: PNH patients with concurrent AA (PNH/AA, N=27) and without AA (classic PNH, N=19). Biochemical indicators of intravascular hemolysis, hematological laboratory values, transfusion requirement, and PNH-associated complications were assessed at baseline and every 6 months after initiation of eculizumab treatment.

RESULTS

The median patient age was 46 years and median duration of eculizumab treatment was 34 months. Treatment with eculizumab induced rapid inhibition of hemolysis. At 6-month follow-up, LDH decreased to near normal levels in all patients; this effect was maintained until the 36-month follow-up regardless of concurrent AA. Transfusion independence was achieved by 53.3% of patients within the first 6 months of treatment and by 90.9% after 36 months of treatment. The mean number of RBC units transfused was significantly reduced, from 8.5 units during the 6 months prior to initiation of eculizumab to 1.6 units in the first 6 months of treatment, for the total study population; this effect was similar in both PNH/AA and classic PNH.

CONCLUSION

This study demonstrated that eculizumab is beneficial in the management of patients with PNH/AA, similar to classic PNH.