Biomarkers and laboratory assessments for monitoring the treatment of patients with paroxysmal nocturnal hemoglobinuria: Differences between terminal and proximal complement inhibition

Anchored Indirect Treatment Comparison Finds Comparable Effects of Pegcetacoplan and Iptacopan in Paroxysmal Nocturnal Haemoglobinuria

BACKGROUND

Paroxysmal nocturnal haemoglobinuria (PNH) is an ultra-rare, acquired non-malignant haematological disorder characterised by thrombosis risk, serious complications and debilitating symptoms in untreated patients.

OBJECTIVE

This anchored indirect treatment comparison (ITC) evaluated efficacy data between proximal complement 3 inhibitor (C3i) pegcetacoplan and factor B inhibitor, iptacopan, in patients with PNH previously treated with complement 5 inhibitors (C5i; eculizumab, ravulizumab).

METHODS

Respective pivotal studies provided patient-level trial data for pegcetacoplan (16-week PEGASUS [NCT03500549]) and published data for iptacopan (24-week APPLY PNH [NCT04558918]). Differences in study design, duration and statistical methods between PEGASUS and APPLY PNH necessitated the comparative analyses to be conducted on secondary measures based on haemoglobin (Hb) levels, absolute reticulocyte count (ARC), lactate dehydrogenase (LDH) levels, and patient-reported outcomes on the Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-Fatigue) scale scores. The availability of a common reference C5i treatment group in both PEGASUS and APPLY PNH studies allowed anchored ITC (Bucher method). Simulated treatment comparison (STC) assessed the robustness of the main analysis.

RESULTS

Overall, baseline characteristics of the populations in the PEGASUS and APPLY PNH studies were broadly comparable. Anchored ITC showed comparable outcomes (mean difference, [95% CI]) on change-from-baseline to end of study for pegcetacoplan versus C5i, and iptacopan versus C5i, respectively, across endpoints: Hb level (-0.49 g/dL [-1.78, 0.80]); ARC (-34.41 × 109/L [-90.02, 21.21]); LDH level (-115.16 U/L [-244.40, 14.01]); FACIT-Fatigue score (3.57 [-5.60, 12.73]). Finally, the STC produced results consistent with the main Bucher analyses across all clinical endpoints and patient-reported fatigue, providing similar point estimates and confidence intervals.

CONCLUSION

This anchored ITC, based on data from pivotal trials, did not indicate significant differences in clinical or patient-reported outcomes between pegcetacoplan and iptacopan in PNH treatment. The findings suggest that PNH treatment decisions should also consider individualised disease- and patient-related factors.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT03500549.

Long-term efficacy and safety of danicopan as add-on therapy to ravulizumab or eculizumab in PNH with significant EVH

ABSTRACT

Complement C5 inhibitor treatment with ravulizumab or eculizumab for paroxysmal nocturnal hemoglobinuria (PNH) improves outcomes and survival. Some patients remain anemic due to clinically significant extravascular hemolysis (cs-EVH; hemoglobin [Hb] ≤9.5 g/dL and absolute reticulocyte count [ARC] ≥120 × 109/L). In the phase 3 ALPHA trial, participants received oral factor D inhibitor danicopan (150 mg 3 times daily) or placebo plus ravulizumab or eculizumab during the 12-week, double-blind treatment period 1 (TP1); those receiving placebo switched to danicopan during the subsequent 12-week, open-label TP2 and continued during the 2-year long-term extension (LTE). There were 86 participants randomized in the study, of whom 82 entered TP2, and 80 entered LTE. The primary end point was met, with Hb improvements from baseline at week 12 (least squares mean change, 2.8 g/dL) with danicopan. For participants switching from placebo to danicopan at week 12, improvements in mean Hb were observed at week 24. Similar trends were observed for the proportion of participants with ≥2 g/dL Hb increase, ARC, proportion of participants achieving transfusion avoidance, and Functional Assessment of Chronic Illness Therapy-Fatigue scale scores. Improvements were maintained up to week 72. No new safety signals were observed. The breakthrough hemolysis rate was 6 events per 100 patient-years. These long-term data demonstrate sustained efficacy and safety of danicopan plus ravulizumab/eculizumab for continued control of terminal complement activity, intravascular hemolysis, and cs-EVH in PNH. This trial was registered at www.clinicaltrials.gov as #NCT04469465.

Monitoring and Treatment of Paroxysmal Nocturnal Hemoglobinuria in Patients with Aplastic Anemia in Asia: An Expert Consensus

Paroxysmal nocturnal hemoglobinuria (PNH) clones can be identified in a significant proportion of patients with aplastic anemia (AA). Screening for PNH clones at the time of an AA diagnosis is recommended by national and international guidelines. In this report, an expert panel of physicians discusses current best practices and provides recommendations for managing PNH in patients with AA in the Asia-Pacific region. Plasma/serum lactate dehydrogenase (LDH) levels and reticulocyte count should be measured with every blood test. PNH clone size should be monitored regularly by flow cytometry, with on-demand testing in the event of a rise in LDH level ± reticulocyte count or development of symptoms such as thrombosis. Monitoring for PNH clones can guide the choice of initial AA treatment, although flow cytometry has resource implications which may present a challenge in some Asia-Pacific countries. The treatment of patients with both PNH and AA depends on which condition predominates; following PNH treatment guidelines if hemolysis is the main symptom and AA treatment guidelines if bone marrow failure is severe (regardless of whether hemolysis is mild or moderate). The expert panel's recommendations on the monitoring and treatment of PNH in patients with AA are practical for healthcare systems in the Asia-Pacific region.

Thrombosis in Paroxysmal Nocturnal Hemoglobinuria (PNH): From Pathogenesis to Treatment

Paroxysmal Nocturnal Hemoglobinuria (PNH) constitutes a rare bone marrow failure syndrome characterized by hemolytic anemia, thrombotic events (TEs), and bone marrow aplasia of variable degrees. Thrombosis is one of the major clinical manifestations of the disease, affecting up to 40% of individuals with PNH. Venous thrombosis is more prevalent, affecting mainly unusual sites, such as intrabdominal and hepatic veins. TEs might be the first clinical manifestation of PNH. Complement activation, endothelial dysfunction, hemolysis, impaired bioavailability of nitric oxide, and activation of platelets and neutrophils are implicated in the pathogenesis of TEs in PNH patients. Moreover, a vicious cycle involving the coagulation cascade, complement system, and inflammation cytokines, such as interleukin-6, is established. Complement inhibitors, such as eculizumab and ravulizumab (C5 inhibitors), have revolutionized the care of patients with PNH. C5 inhibitors should be initiated in patients with PNH and thrombosis, while they constitute a great prophylactic measure for TEs in those individuals. Anticoagulants, such as warfarin and low-molecular-weight heparin, and, in selected cases, direct oral anticoagulants (DOACs) should be used in combination with C5 inhibitors in patients who develop TEs. Novel complement inhibitors are considered an alternative treatment option, especially for those who develop extravascular or breakthrough hemolysis when terminal inhibitors are administered.

Navigating the Complement Pathway to Optimize PNH Treatment with Pegcetacoplan and Other Currently Approved Complement Inhibitors

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare and potentially life-threatening hematologic disorder caused by a somatic mutation in a relevant portion of hematopoietic stem cells. Mutation of the phosphatidylinositol glycan biosynthesis class A (PIGA) gene prevents the expression of cell-surface proteins, including the complement regulatory proteins CD55 and CD59. With decreased or a lack of CD55 and CD59 expression on their membranes, PNH red blood cells become susceptible to complement-mediated hemolysis (symptoms of which include anemia, dysphagia, abdominal pain, and fatigue), leading to thrombosis. State-of-the-art PNH treatments act by inhibiting the dysregulated complement at distinct points in the activation pathway: late at the C5 level (C5 inhibitors, eculizumab, ravulizumab, and crovalimab), centrally at the C3 level (C3/C3b inhibitors and pegcetacoplan), and early at the initiation and amplification of the alternative pathway (factor B inhibitor, iptacopan; factor D inhibitor, danicopan). Through their differing mechanisms of action, these treatments elicit varying profiles of disease control and offer valuable insights into the molecular underpinnings of PNH. This narrative review provides an overview of the mechanisms of action of the six complement inhibitors currently approved for PNH, with a focus on the C3/C3b-targeted therapy, pegcetacoplan.

Three Years On: The Role of Pegcetacoplan in Paroxysmal Nocturnal Hemoglobinuria (PNH) since Its Initial Approval

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare disease characterized by complement-mediated hemolysis and potentially life-threatening complications. Pegcetacoplan, an inhibitor of complement components C3 and C3b, was approved by the US Food and Drug Administration (FDA) and European Medicines Agency (EMA) in 2021. A recent expansion to its indication by the EMA has made pegcetacoplan available for the treatment of both complement inhibitor-naïve and -experienced patients with PNH who have hemolytic anemia, a similarly broad patient population as in the US. This approval was based on results from the Phase 3 PEGASUS study, where pegcetacoplan showed superiority over the C5 inhibitor eculizumab with regard to improving the hemoglobin level in patients with anemia despite eculizumab treatment, and the Phase 3 PRINCE study, where pegcetacoplan showed superiority over supportive care with regard to hemoglobin stabilization and improving the lactate dehydrogenase level in complement inhibitor-naïve patients. In light of this recent indication expansion by the EMA, this article describes how the strong efficacy of pegcetacoplan is linked to its mechanism of action, which provides broad hemolysis control over both intravascular and extravascular hemolysis to improve a range of disease markers and enhance patients' quality of life. Furthermore, additional data and learnings obtained from over 3 years of experience with pegcetacoplan are summarized, including long-term efficacy and safety results, real-world clinical experiences, pharmacokinetic characteristics, and extensive practical guidance for the first-to-market proximal complement inhibitor for PNH.

Usefulness and analytical performances of complement multiplex assay for measuring complement biomarkers in plasma

INTRODUCTION

The complement system is involved in numerous diseases, through diverse mechanisms and degree of activation. With the emergence of complement targeting therapeutic, simple and accessible tools to evaluate the extent of complement activation are strongly needed.

METHODS

We evaluated two multiplex panels, measuring complement activation fragments (C4a, C3a, C5a, Bb, Ba, sC5b9) and intact components or regulators (C1q, C2, C3, C4, C5, FD, FP, FH, FI). The specificity of each measurement was assessed by using complement proteins depleted sera and plasma collected from patients with complement deficiencies. Normal values distribution was estimated using 124 plasma samples from healthy donors and complement activation profile was assessed in plasma collected from 31 patients with various complement-mediated disorders.

RESULTS

We observed good inter-assay variation. All tested protein deficiencies were accurately detected. We established assay-specific reference values for each analyte. Except for C3, C4 and C4a, the majority of the measurements were in good agreement with references methods or published data.

CONCLUSION

Our study substantiates the utility of the Complement Multiplex assay as a tool for measuring complement activation and deficiencies. Quantifying complement cleavage fragments in patients exhibiting classical or alternative pathway activation allowed evaluating the activation state of the whole cascade.

Efficacy of complement inhibitors for patients with paroxysmal nocturnal hemoglobinuria: a systematic review and meta-analysis

Background

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare acquired hematological disease. The development of complement inhibitors such as eculizumab, ravulizumab, and pegcetacoplan has revolutionized the management of PNH, leading to improvements in overall survival and quality of life for patients.

Objectives

This systematic review aims to provide comprehensive evidence of the efficacy of complement inhibitors in relation to treatment duration.

Design

This is a systematic review and meta-analysis.

Data sources and methods

A thorough literature search was conducted in MEDLINE, EMBASE, and the Cochrane Library up to 3 May 2022. We included all prospective interventional studies including single-arm trials. The primary outcomes of interest were lactate dehydrogenase (LDH) levels, hemoglobin (Hb) concentrations, transfusion avoidance, and Functional Assessment of Chronic Illness Therapy Fatigue (FACIT-F) scores.

Results

Our study included a total of 27 studies, comprising 5 randomized controlled trials and 11 single-arm trials, with a total of 912 patients with PNH. We stratified the studies according to treatment duration, based on the most frequently reported period of 26 weeks. Our analysis showed that treatment-naïve patients who received complement inhibitors had a pooled estimate of a decrease in LDH levels from baseline by -1462.0 U/L (95% CI: -1735.6 to -1188.5) for treatment ⩽26 weeks and -1696.5 U/L (95% CI: -2122.7 to -1270.2) for treatment >26 weeks. The mean Hb levels were increased by 1.4 g/dL (95% CI: 0.5-2.3) and 1.9 g/dL (95% CI: 0.7-3.1) in each group. Treatment with any complement inhibitor prevented the need for transfusion in at least 50% of patients with PNH in all treatment periods. Clinically meaningful improvements in FACIT-F were observed both before and after 26 weeks, with a pooled estimate of 6.8 (95% CI: 6.0-7.6) and 9.5 (95% CI: 7.0-12.0), respectively.

Conclusion

Our findings suggest that complement inhibitors can result in positive treatment outcomes and sustained benefits for patients with PNH.

Paroxysmal Nocturnal Hemoglobinuria: Current Management, Unmet Needs, and Recommendations

Paroxysmal nocturnal hemoglobinuria (PNH) is an ultra-rare, acquired clonal abnormality, which renders hematopoietic cells exquisitely sensitive to complement-mediated destruction. Classical features of PNH include intravascular hemolytic anemia, increased thrombotic risk, and manifestations related to end-organ damage (eg fatigue, chest pain, dyspnea, renal failure, and pulmonary hypertension). With supportive care alone, mortality rate of patients with PNH is approximately 35%. The anti-C5 monoclonal antibody, eculizumab, was the first targeted therapy approved for PNH, and led to improved hemoglobin, quality of life, reduced transfusion need, reduced thrombosis, and greater overall survival. More recently, therapeutics such as longer acting anti-C5 (ravulizumab) and anti-C3 (pegcetacoplan) medications have been approved, along with other novel therapeutics in late-stage clinical trials. Biosimilars of eculizumab are also now available. Proximal inhibitors (against C3, factor B, and factor D) have shown significant improvements in hemoglobin and transfusion-avoidance in patients who remain anemic despite C5 inhibition. Despite these novel therapies, some unmet challenges remain, including management of breakthrough hemolysis, clinically significant iatrogenic extravascular hemolysis, optimal management in pregnancy, and infection risk mitigation as new targets in the complement system are blocked. In addition, the use of self-administered subcutaneous and oral therapies raises concerns around treatment adherence and the risks of uncontrolled terminal complement. Given the ultra-rare nature of PNH, development is underway of a centralized international registry to capture and analyze the data as they mature for various new therapies and characterize the clinical challenges related to PNH management.