Complement-mediated Hemolysis Research Articles

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.

Moving toward Individual Treatment Goals with Pegcetacoplan in Patients with PNH and Impaired Bone Marrow Function.

Paroxysmal nocturnal haemoglobinuria (PNH) is a rare, potentially life-threatening haematological disease characterised by chronic complement-mediated haemolysis with multiple clinical consequences that impair quality of life. This post hoc analysis assessed haematological and clinical responses to the first targeted complement C3 inhibitor pegcetacoplan in patients with PNH and impaired bone marrow function in the PEGASUS (NCT03500549) and PRINCE (NCT04085601) studies. For patients with impaired bone marrow function, defined herein as haemoglobin <10 g/dL and absolute neutrophil count <1.5 × 109 cells/L, normalisation of the parameters may be difficult. Indeed, 20% and 43% had normalised haemoglobin in PEGASUS and PRINCE, respectively; 60% and 57% had normalised LDH, and 40% and 29% had normalised fatigue scores. A new set of parameters was applied using changes associated with clinically meaningful improvements, namely an increase in haemoglobin to ≥2 g/dL above baseline, decrease in LDH to ≤1.5× the upper limit of normal, and an increase in fatigue scores to ≥5 points above baseline. With these new parameters, 40% and 71% of PEGASUS and PRINCE patients had improved haemoglobin; 60% and 71% had an improvement in LDH, and 60% and 43% had an improvement in fatigue scores. Thus, even patients with impaired bone marrow function may achieve clinically meaningful improvements with pegcetacoplan.

The complement model disease paroxysmal nocturnal hemoglobinuria.

We describe initial, current, and future aspects of complement activation and inhibition in the rare hematological disease paroxysmal nocturnal hemoglobinuria (PNH). PNH is a rare but severe hematological disorder characterized by complement-mediated intravascular hemolysis resulting in anemia and severe thrombosis. Insights into the complement-mediated pathophysiology ultimately led to regulatory approval of the first-in-class complement inhibitor, eculizumab, in 2007. This anti-complement C5 therapy resulted in the stabilization of many hematologic parameters and dramatically reduced the often fatal, coagulant-resistant thrombotic events. Despite the remarkable clinical success, a substantial proportion of PNH patients experience suboptimal clinical responses during anti-C5 therapy. We describe the identification and mechanistic dissection of four unexpected processes responsible for such suboptimal clinical responses: (1) pharmacokinetic and (2) pharmacodynamic intravascular breakthrough hemolysis, (3) continuing low-level residual intravascular hemolysis, and (4) extravascular hemolysis. Novel complement therapeutics mainly targeting different complement proteins proximal in the cascade attempt to address these remaining problems. With five approved complement inhibitors in the clinic and many more being evaluated in clinical trials, PNH remains one of the complement diseases with the highest intensity of clinical research. Mechanistically unexpected breakthrough events occur not only with C5 inhibitors but also with proximal pathway inhibitors, which require further mechanistic elaboration.

Acute paroxysmal cold hemoglobinuria upon dengue fever: A case report

Rationale: Dengue fever is capable of inciting the formation of transient polyclonal antibodies directed at red blood cell antigens, resulting in complement-mediated hemolysis, leading to intravascular hemolysis and hemoglobinuria. Patient’s concern: A 12-year-old male patient who recovered from dengue fever a week ago had red blood cell agglutination, spherocytes, and engulfment of red blood cells (erythrophagocytosis) by monocytes and neutrophils on routine hematological peripheral blood smear. The unexpected blood smear results prompted the lab physicians to investigate autoimmune hemolytic anemia, which revealed a monospecific positive direct antiglobulin test for complement (C3d, C3b) and the presence of Donath-Landsteiner antibody. Diagnosis: Paroxysmal cold hemoglobinuria (PCH), secondary to dengue fever. Interventions: Oxygen supplements, antibiotics, intravenous immunoglobulins, steroid therapy, and packed cell transfusions were administered. Outcomes: The patient’s condition was improved following the therapy. Lessons: Post-dengue PCH is a rare complication that requires a thorough peripheral smear examination for erythrophagocytosis, as advanced hematology analyzers fail to detect such findings.

Cost-effectiveness of sutimlimab in cold agglutinin disease.

Primary cold agglutinin disease (CAD) is a rare autoimmune hemolytic anemia caused by cold-reactive antibodies that bind to red blood cells and lead to complement-mediated hemolysis. Patients with primary CAD experience the burden of increased health resource utilization and reduced quality of life. The standard-of-care (SOC) in patients with primary CAD has included cold avoidance, transfusion support, and chemoimmunotherapy. The use of sutimlimab, a humanized monoclonal antibody that selectively inhibits C1-mediated hemolysis, was shown to reduce transfusion-dependence and improve quality of life across two pivotal phase 3 studies, further supported by 2-year extension data. Using data from the transfusion-dependent patient population that led to sutimlimab's initial FDA approval, we performed the first-ever cost-effectiveness analysis in primary CAD. The projected incremental cost-effectiveness ratio (ICER) in our Markov model was $2 340 000/QALY, significantly above an upper-end conventional US willingness-to-pay threshold of $150 000/QALY. These results are consistent across scenarios of higher body weight and a pan-refractory SOC patient phenotype (i.e., treated sequentially with bendamustine-rituximab, bortezomib, ibrutinib, and eculizumab). No parameter variations in deterministic sensitivity analyses changed our conclusion. In probabilistic sensitivity analysis, SOC was favored over sutimlimab in 100% of 10 000 iterations. Exploratory threshold analyses showed that significant price reduction (>80%) or time-limited treatment (<18 months) followed by lifelong clinical remission off sutimlimab would allow sutimlimab to become cost-effective. The impact of sutimlimab on health system costs with longer term follow-up data merits future study and consideration through a distributional cost-effectiveness framework.

Thrombosis and meningococcal infection rates in pegcetacoplan-treated patients with paroxysmal nocturnal hemoglobinuria in the clinical trial and postmarketing settings

BackgroundParoxysmal nocturnal hemoglobinuria (PNH) is a rare, acquired hematologic disease characterized by complement-mediated hemolysis and thrombosis. Complement component 5 (C5) inhibitors have decreased PNH-related thrombosis rates and reduced mortality compared with those of age-matched controls. A small but significantly increased risk of life-threatening Neisseria infections, especially N meningitidis, represents a long-term safety risk of complement inhibition. ObjectivesTo evaluate the rates of thrombosis and meningococcal infections in patients with PNH treated with the complement component 3–targeted therapy pegcetacoplan. MethodsCumulative patient-year exposure to pegcetacoplan was calculated, and thrombotic events and meningococcal infections were reviewed in 7 clinical trials and in the postmarketing setting. The clinical trial protocols and pegcetacoplan labeling required vaccination against Streptococcus pneumoniae, N meningitidis, and Haemophilus influenzae before pegcetacoplan use; the label allowed for prophylactic antibiotic use if pegcetacoplan must be administered before vaccination. ResultsAs of November 13, 2022, 464 patients with PNH had 619.4 patient-years of pegcetacoplan exposure in completed/ongoing clinical trials and the postmarketing setting. Seven thrombotic events were reported: 5 in clinical trials (2 in the same patient) and 2 in the postmarketing setting. The overall thrombosis rate was 1.13 events per 100 patient-years (clinical trials: 1.22 events/100 patient-years in 409.4 years; postmarketing: 0.95 events/100 patient-years in 210.0 years). No infections with meningococcal bacteria were reported. ConclusionEvent rates for thrombosis were comparable between pegcetacoplan and previously reported rates of C5 inhibitors in patients with PNH, and no cases of meningococcal infection were reported with pegcetacoplan. Continued follow-up is required.

Safety and Efficacy of Pegcetacoplan in Adult Patients with Paroxysmal Nocturnal Hemoglobinuria over 48Weeks: 307 Open-Label Extension Study.

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare, life-threatening disease characterized by complement-mediated hemolysis and thrombosis. Pegcetacoplan, the first targeted complement component3 (C3) PNH therapy, was safe and efficacious in treatment-naive and pre-treated patients with PNH in five clinical trials. The 307 open-label extension (OLE) study (NCT03531255) is a non-randomized, multicenter extension study of long-term safety and efficacy of pegcetacoplan in adult patients with PNH who completed a pegcetacoplan parent study. All patients received pegcetacoplan. Outcomes at the 48-week data cutoff (week48 of 307-OLE or August 27, 2021, whichever was earlier) are reported. Hemoglobin concentrations, Functional Assessment of Chronic Illness Therapy (FACIT)-Fatigue scores, and transfusion avoidance were measured. Hemoglobin > 12g/dL and sex-specific hemoglobin normalization (i.e., male, ≥ 13.6g/dL; female, ≥ 12g/dL) were assessed as percentage of patients with data available and no transfusions 60days before data cutoff. Treatment-emergent adverse events, including hemolysis, were reported. Data from 137 patients with at least one pegcetacoplan dose at data cutoff were analyzed. Mean (standard deviation [SD]) hemoglobin increased from 8.9 (1.22) g/dL at parent study baseline to 11.6 (2.17) g/dL at 307-OLE entry and 11.6 (1.94) g/dL at data cutoff. At parent study baseline, mean (SD) FACIT-Fatigue score of 34.1 (11.08) was below the general population norm of 43.6; scores improved to 42.8 (8.79) at 307-OLE entry and 42.4 (9.84) at data cutoff. In evaluable patients, hemoglobin > 12g/dL occurred in 40.2% (43 of 107) and sex-specific hemoglobin normalization occurred in 31.8% (34 of 107) at data cutoff. Transfusion was not required for 114 of 137 patients (83.2%). Hemolysis was reported in 23 patients (16.8%). No thrombotic events or meningococcal infections occurred. Pegcetacoplan sustained long-term improvements in hemoglobin concentrations, fatigue reduction, and transfusion burden. Long-term safety findings corroborate the favorable profile established for pegcetacoplan. ClinicalTrials.gov identifier, NCT03531255.

Iptacopan: First Approval.

Iptacopan (FABHALTA®) is an oral complement Factor B inhibitor developed by Novartis Pharmaceuticals for the treatment of complement-mediated diseases. Acting upstream of complement 5 in the alternative pathway, iptacopan inhibits both terminal complement-mediated intravascular haemolysis and complement 3-mediated extravascular haemolysis. On 5 December 2023, iptacopan received approval in the USA for the treatment of adults with paroxysmal nocturnal haemoglobinuria (PNH). This article summarizes the milestones in the development of iptacopan leading to this first approval for PNH.

Expert consensus on the management of pharmacodynamic breakthrough-hemolysis in treated paroxysmal nocturnal hemoglobinuria

ABSTRACT Introduction: Paroxysmal nocturnal hemoglobinuria (PNH) is a rare, acquired, non-malignant hematologic disease characterized by complement-mediated hemolysis (with or without hemoglobinuria), fatigue, increased susceptibility to thrombosis, and bone marrow dysfunction. The development of complement inhibitors has transformed outcomes for patients with PNH, but patients may still experience pharmacodynamic breakthrough hemolysis (BTH), which can be caused by exposure to a complement amplifying condition (CAC), such as vaccination, infection, or surgery. Materials and methods: A 13-member expert panel used a validated methodology (a RAND/UCLA modified Delphi panel) to develop consensus on how to classify pharmacodynamic BTH in patients with complement-inhibitor treated PNH. Physicians reviewed literature, rated the appropriateness of over 400 scenarios, and discussed the ratings at an in-person meeting. Results: After the meeting, the panel agreed on 77% of scenarios. Here, we present the group’s agreed-upon recommendations on how to manage BTH caused by a CAC, as well as provide a severity classification system for BTH and strategies to mitigate risk of BTH in special circumstances (e.g. vaccination, planned or unplanned surgery, and pregnancy). Discussion: In general, as severity of BTH increased, experts agreed more interventions to manage the BTH were appropriate. These recommendations are based on clinical experience and opinion. Without clear data from randomized trials to guide the management of BTH, expert opinion can be useful to support patient care.

In vitro immunoregulatory role of recombinant Ancylostoma ceylanicum calreticulin.

Ancylostoma ceylanicum is a zoonotic soil-derived nematode that parasitizes the intestines of humans and animals (dogs and cats), leading to malnutrition and iron-deficiency anemia. Helminth parasites secrete calreticulin (CRT), which regulates or blocks the host's immune response. However, no data on A. ceylanicum calreticulin (Ace-CRT) are available. We investigated the biological function of recombinant Ace-CRT (rAce-CRT). rAce-CRT showed reliable antigenicity and stimulated the proliferation of mouse splenocytes and canine peripheral blood mononuclear cells. Quantitative reverse-transcription PCR assays revealed that rAce-CRT primarily promoted the expression of T helper 2 cytokines, particularly IL-13, in canine peripheral blood lymphocytes. rAce-CRT inhibited complement-mediated sheep erythrocyte hemolysis in vitro. Our findings indicate that Ace-CRT plays an immunomodulatory role and may be a promising candidate molecule for a hookworm vaccine.

Multisite Thrombosis in a Patient with Paroxysmal Nocturnal Hemoglobinuria

AbstractCase: Paroxysmal nocturnal hemoglobinuria (PNH) is an extremely rare bone marrow disorder caused by acquired mutations in the phosphatidylinositol glycan class A gene, which lead to a partial or total loss of the cellular complement regulators CD55 and CD59.1 In addition to complement-mediated hemolysis and cytopenia, venous and arterial thromboses at multiple and/or unusual sites are a common complication and occur in up to 44% of patients in historic PNH cohorts.1 2

Management of acute breakthrough hemolysis with intensive pegcetacoplan dosing in patients with PNH

AbstractParoxysmal nocturnal hemoglobinuria (PNH) is characterized by complement-mediated intravascular hemolysis leading to anemia, fatigue, and potentially life-threatening thrombotic complications. Breakthrough hemolysis (BTH) was first described in patients with PNH treated with terminal complement C5 inhibitors when intravascular hemolysis reoccurred despite treatment. Pegcetacoplan, the first proximal complement C3 inhibitor, offers broad hemolysis control in patients with PNH. While experience of managing BTH on C5 inhibitors is documented, very limited guidance exists for proximal complement inhibitors. This interim analysis assessed the effect of intensive treatment with pegcetacoplan following an acute BTH event in a subset of patients enrolled in the ongoing open-label extension study of pegcetacoplan in PNH. Thirteen patients with acute BTH included in the analysis received either a single IV dose of 1080 mg (n = 4) or 1080 mg subcutaneous (SC) dosing on 3 consecutive days (n = 9). A potential, clinically-relevant complement-amplifying condition, such as infection or vaccination, was reported in approximately half of the patients experiencing an acute BTH. Lactate dehydrogenase (LDH) levels decreased between day 1 and day 2 in 8 of 12 evaluable patients and in all 13 patients at day 7 to 12. Nine of 13 patients (69%) achieved LDH <2× the upper limit of normal by day 14 to 19. All adverse events associated with the acute BTH event were considered resolved by the investigators. Overall, intensive treatment with pegcetacoplan was safe and well tolerated. These novel data support effective management of acute BTH events in patients on pegcetacoplan with intensive IV or SC pegcetacoplan dosing. This trial was registered at www.clinicaltrials.gov as #NCT03531255.

CL-K1 Promotes Complement Activation and Regulates Opsonophagocytosis of Macrophages with CD93 Interaction in a Primitive Vertebrate.

Collectin is a crucial component of the innate immune system and plays a vital role in the initial line of defense against pathogen infection. In mammals, collectin kidney 1 (CL-K1) is a soluble collectin that has recently been identified to have significant functions in host defense. However, the evolutionary origins of immune defense of CL-K1 and its mechanism in clearance of pathogenic microorganisms remain unclear, especially in early vertebrates. In this study, the Oreochromis niloticus CL-K1 (OnCL-K1) protein was purified and identified, which was capable of binding to two important pathogens of tilapia, Streptococcus agalactiae and Aeromonas hydrophila. Interestingly, OnCL-K1 exhibited direct bactericidal activity by binding to lipoteichoic acid or LPS on cell walls, disrupting the permeability and integrity of the bacterial membrane invitro. Upon bacterial challenge, OnCL-K1 significantly inhibited the proliferation of pathogenic bacteria, reduced the inflammatory response, and improved the survival of tilapia. Further research revealed that OnCL-K1 could associate with OnMASPs to initiate and regulate the lectin complement pathway. Additionally, OnCD93 reduced the complement-mediated hemolysis by competing with OnMASPs for binding to OnCL-K1. More importantly, OnCL-K1 could facilitate phagocytosis by collaborating with cell surface CD93 in a lectin pathway-independent manner. Moreover, OnCL-K1 also promoted the formation of phagolysosomes, which degraded and killed ingested bacteria. Therefore, this study reveals the antibacterial response mechanism of CL-K1 in primitive vertebrates, including promoting complement activation, enhancing opsonophagocytosis, and killing of macrophages, as well as its internal links, all of which provide (to our knowledge) new insights into the understanding of the evolutionary origins and regulatory roles of the collectins in innate immunity.

ПАРОКСИЗМАЛЬНАЯ НОЧНАЯ ГЕМОГЛОБИНУРИЯ (случай из практики)

The non-tumor blood disease paroxysmal nocturnal hemoglobinuria, which develops as a result of acquired mutations in the PIG-A gene, is presented. As a result of mutation, there is a loss of complement-regulating proteins (GPI-AP) on the surface of blood cells (on erythrocytes – CD55, CD59, on granulocytes – CD16, CD24, on monocytes – CD14, CD48). A clone of cells subject to complement-mediated hemolysis is formed. With intravascular hemolysis of erythrocytes, a lot of hemoglobin appears in the bloodstream, then it enters the urine, it darkens. Neutrophils are also destroyed, platelet aggregation increases. Venous and arterial thrombosis can occur throughout the body. The criteria and forms of PNG are described. The clinical manifestations are highlighted, the knowledge of which is necessary for doctors of different specialties to suspect PNG at the beginning of its development. When the diagnosis is delayed, the patient with thrombosis is treated under different diagnoses, time is running out… Identification of patients at risk can affect the outcome of PNG. Highly sensitive flow cytometry makes it possible to detect an APG clone with a size of 0.01% or more. Monoclonal antibody therapy changed the natural course of APG. The article presents the medical history of a patient with PNG. The diagnosis was made in our clinic at the stage of serious thrombotic complications, after a stay in two Moscow clinics where this disease was not suspected.

A Critical Appraisal of Clinical Practice Guidelines for Pharmacological Treatments of Paroxysmal Nocturnal Hemoglobinuria

Aims: Paroxysmal nocturnal hemoglobinuria (PNH) is a rare chronic disease characterized by complement-mediated hemolysis, thrombosis, and bone marrow failure. This study aims to identify methodological limitations in Clinical Practice Guidelines (CPG) for the treatment of PNH. Thus, we critically evaluate the guidelines, highlighting relevant recommendations supported by high-quality evidence to improve healthcare strategies.&#x0D; Methodology: A systematic search was carried out in PubMed/MEDLINE, Scopus, Embase, COCHRANE, and TRIP databases. From 1995 initially identified references, 1649 articles underwent title and abstract screening. Twenty-three references were selected for full-text screening. Ultimately, 12 CPGs were included. Four independent reviewers assessed the CPGs’ methodological quality using the instruments “Appraisal of Guidelines for Research and Evaluation II” (AGREE II) and “Recommendation Excellence” (AGREE-REX). Their characteristics, as well as any differences in recommendations, were summarized and compared.&#x0D; Results: Twelve guidelines published from 2011 to 2022 by Spain, Brazil, Mexico, Israel, Canada, Turkey, Scotland, and the United Kingdom were included. The UK’s and Brazil’s CPGs received the highest scores. Overall, the CPGs scored strongly in the domains of “Scope and Purpose” and “Clarity of Presentation” since they addressed fundamental aspects, such as aim, specific health questions, target population, and language. All guidelines presented deficiencies in the “Editorial Independence” in AGREE II, and “Values and Preferences” in AGREE-REX, demonstrating the need for a careful revision and improvement of future versions.&#x0D; Conclusion: We found disparities in the methodological quality of the available CPGs. Despite being extremely important, recommendations on adapting treatment to local policies and further updates that include newly approved medications were absent. Approaches that prioritize the engagement of methodologists and multidisciplinary collaborators may also lead to higher quality CPGs for treating PNH.

Complement-targeted therapy for autoimmune diseases.

The success and safety seen in treating complement-mediated hemolysis conditions has sparked the development of targeted therapies for rare autoimmune diseases, with expansion to more common autoimmune conditions. Various classes of drugs, including small molecules, peptides, monoclonal antibodies, and small interfering RNA (siRNA), are undergoing development to specifically address complement activity. A dual approach targeting both complement and other immune components may be required for autoimmune diseases characterized by inflammation and complex pathogenic mechanisms. siRNA, which suppresses complement production, is emerging as a potent therapeutic tool. Combining a complement-blocking siRNA drug with a treatment that reduces autoantibodies could prove clinically feasible and impactful in managing these conditions.

COVID-19 vaccination prevents a more severe course and treatment with complement inhibitors reduce worsening hemolysis during the Omicron pandemic in patients with PNH: a single-center study

Objective Paroxysmal nocturnal hemoglobinuria (PNH) is a rare acquired disease characterized by chronic complement-mediated hemolysis. The concentrated outbreak of coronavirus disease 2019 (COVID-19) in China after 6 December 2022, provided an opportunity to observe the disease course of PNH during an active Omicron infection epidemic. Patients and method Patients diagnosed with PNH at Peking Union Medical College Hospital (PUMCH) before 6 December 2022, were followed up until 10 April 2023. Clinical data related to coronavirus infection and hemolysis were recorded. Factors influencing the infection and severity rate of Omicron, as well as hemolysis provocation, were analyzed. Results In total, 131 patients with PNH were included in this retrospective analysis; 87.8% were infected with Omicron. Among them, 15.7% met the criteria for severity, and 1 patient died (0.87%). No protective factors were identified against Omicron infections. However, patients with severe Omicron infection (n = 18) had a lower vaccination rate than those with non-severe infection (n = 97; p = 0.015). Among those infected (n = 115) with Omicron, there was a significant increase in lactate dehydrogenase (LDH) levels compared with those in the uninfected group (n = 16, p = 0.000). Patients with severe infections (n = 18) had even higher LDH increase rates than those without severe infections (n = 97; p = 0.002). 10 (37.0%) patients treated with complement inhibitors developed breakthrough hemolysis (BTH). Patients treated with complement inhibitors (n = 27) exhibited less severe hemolysis than treatment-naïve patients (n = 104; p = 0.003). Conclusions Omicron infection exacerbates hemolytic attacks in patients with PNH. Vaccination helps mitigate the severity of Omicron infection, and using complement inhibitors reduces hemolysis exacerbation.

Alternative Pathway Masp-3 Inhibitor OMS906 Effectively and Potently Inhibits Complement-Mediated Hemolysis in Preclinical Models Mechanistically Similar to Paroxysmal Nocturnal Hemoglobinuria

Introduction: Mannan-binding lectin-associated serine protease-3 (MASP-3) activates pro-complement Factor D (CFD) to form mature CFD, a rate-limiting enzyme in the alternative pathway (AP) of the complement system. CFD controls cleavage of complement Factor B (CFB) to form AP C3 convertase, which drives an amplification loop of protease complexes that activates both C3b-mediated opsonization and the terminal pathway. OMS906 is a humanized IgG4 monoclonal antibody (mAb) that binds to and inhibits MASP-3, thereby blocking maturation of CFD and downstream AP activity. Data from mice and monkeys demonstrated that OMS906 is highly selective and effectively inhibits AP activity. MASP-3 inhibition could provide therapeutic benefit in a variety of AP-mediated diseases, such as paroxysmal nocturnal hemoglobinuria (PNH). In PNH, a rare and life-threatening disorder, red blood cells (RBCs) lacking CD59 and CD55 regulatory surface proteins are targeted for rapid clearance via intravascular hemolysis and extravascular hemolysis, due to AP dysregulation. Clinical efficacy of OMS906 in a study of patients with PNH has been reported. To provide mechanistic support, we conducted in vitro and in vivo studies using preclinical models of complement-mediated hemolysis that have mechanistic overlap with PNH. Methods: In vitro potency of OMS906 was assessed using RBCs deficient in CD55 and CD59 to mimic the physiological effect of PNH. Healthy human donor RBCs were treated with inhibitory CD55 and CD59 antibodies, then incubated under AP assay conditions with human serum (diluted to 50%) containing OMS906, anti-C5 IgG4 mAb, or an isotype mAb control. The potency of OMS906, expressed as the half-maximal inhibitory concentration (IC 50), was assessed based on prevention of hemolysis of the PNH-like RBCs in vitro. Lysis was quantified by measuring hemoglobin released into sample supernatants using spectrophotometric absorbance. The in vivo effect of OMS906 on survival of murine RBCs prone to rapid clearance was assessed using RBCs from Crry -/- mice, which lack a rodent-specific complement regulatory protein that blocks AP activation. C57BL/6J male mice were intravenously injected with fluorescent labelled Crry -/- RBCs and received OMS906 or isotype mAb control via subcutaneous injection, or anti-CFB mAb via intraperitoneal injection. Blood samples were taken daily until Day 14 and the remaining number of Crry -/- RBCs measured by flow cytometry. Results: In vitro, OMS906 inhibited terminal cell lysis in human PNH-like RBCs more potently than a C5 inhibitor. Comparison of representative drug concentration-response showed that the average functional potency was 58-fold greater with OMS906 (IC 50: 0.8 μg/mL; 3 experiments; 12 total RBC donors) than with anti-C5 mAb (IC 50: 46.2 μg/mL; 2 experiments; 4 total RBC donors). In addition, the maximal extent to which lysis was inhibited was consistently greater with OMS906 than with anti-C5 mAb. In vivo, the rate of decline in number of Crry -/- RBCs was significantly slowed in mice treated with OMS906, in contrast to the rapid loss observed in isotype mAb control-treated mice ( Figure). OMS906 recipients showed a rate of Crry -/- RBC survival similar to the anti-CFB mAb group. Conclusion: OMS906 inhibited RBC lysis more potently than a C5 inhibitor, providing evidence that MASP-3 inhibition blocks downstream terminal activity and thus intravascular hemolysis. In addition, OMS906 improved survival of Crry -/- RBCs comparably to a CFB inhibitor, indicating that MASP-3 inhibition prevents the AP-mediated destruction of RBCs predictive of extravascular hemolysis. OMS906 is currently in clinical development for the treatment of PNH.

Disease Management and Outcomes in Patients with Paroxysmal Nocturnal Hemoglobinuria: A Retrospective Analysis of Observational Data from the United States

Background: Paroxysmal nocturnal hemoglobinuria (PNH) is a rare hemolytic disease characterized by complement-mediated hemolysis, thrombophilia, bone marrow failure (BMF), and renal disease. PNH is clinically heterogeneous, and hospitalization and regular blood transfusions may be needed. Treatment with currently approved C5 inhibitors (C5i), eculizumab and ravulizumab, have shown efficacy in intravascular hemolysis control and reduction in thrombosis risk. Yet, in routine clinical practice, a limited number of patients receive C5i in the United States. Moreover, less than 70% of patients treated with eculizumab continue to receive treatment 1 year following PNH diagnosis. If the disease is managed inadequately, patients may experience prolonged morbidity, increased frequency and severity of symptoms, and early mortality. There is limited real-world evidence available on PNH disease management. Aim: To better understand the disease management and consequences of PNH. Methods: In this retrospective observational study, we analyzed 1227 patients aged ≥18 years in the TriNetX network who were diagnosed with PNH on or after 1 January 2007 and had ≥180 days of post-diagnosis follow-up data (97% were based in the United States). Patients were followed from 1 January 2007 to 6 May 2023. Disease management and outcomes were analyzed for all patients, including those with chronic anemia who were complement-inhibitor naïve. Chronic anemia was defined as hemoglobin &amp;lt;10 g/dL without any hemoglobin measure of ≥10 g/dL between 3 months prior to PNH diagnosis (index date) and 6 months after diagnosis. PNH-related hospitalization was defined by specific International Classification of Diseases codes. The baseline period was defined as 1 year prior to PNH diagnosis. Event rates were estimated for hospitalization (recurrent), transfusions (recurrent), BMF, and death. Rates are adjusted for exposure time (time between diagnosis and end of follow-up) and reported as per person-year with 95% confidence intervals (CIs). Results: In the overall cohort, 58% of patients were female, and the median (interquartile range) age was 56 (38-68) years. During a median 35 (19-62) months of follow-up, 322 (26%) patients received blood transfusions and 172 (14%) patients received C5i. Median time to C5i initiation since diagnosis was 1 (0-10) month with a median treatment duration of 14 (0-49) months. Out of 1227 patients, 50 (4%) had chronic anemia and were complement-inhibitor naïve. The median length of follow-up in this subgroup was 14 (7-43) months. Most of these patients (96%) had PNH with bone marrow disorder subtype. Median hemoglobin and lactate dehydrogenase levels at baseline were 8 (7-8) g/dL and 313 (218-489) U/L, respectively. Out of these 50 patients, first-line treatment was initiated a median of 1 (1-6) month after diagnosis, with anticoagulants and corticosteroids being the most frequently prescribed. During follow-up, 32 (64%) of these patients experienced ≥1 hospitalization (rate 0.78, 95% CI 0.62-0.95) with a median of 3 (2-9) days stay for the first hospitalization. Anemia (42%), abdominal pain (36%), and infections (9%) were the leading causes of admission. In addition, 26 (52%) patients were transfusion dependent (rate 1.52, 95% CI 1.30-1.77) and 30 (60%) experienced BMF (rate 0.71, 95% CI 0.48-0.99). Moreover, 21 (42%) of these patients died during follow-up (rate 0.19, 95% CI 0.12-0.28). Discussion: These findings indicate that complement-inhibitor naïve patients with chronic anemia have substantial disease burden, including frequent hospitalization, high transfusion dependency, and early mortality. In addition, the results show that only a minority of patients in this cohort received C5i. Study limitations include that mortality is likely to be underestimated, as only in-hospital deaths are captured in these data. The small sample size limits the drawing of robust conclusions. However, overall, these findings support the need to address PNH disease burden and improve disease management.

Efficacy and Safety Is Maintained in Adult Patients with Paroxysmal Nocturnal Hemoglobinuria Receiving Pegcetacoplan for up to 3 Years

Introduction: Paroxysmal nocturnal hemoglobinuria (PNH) is a rare, life-threatening disease characterized by complement-mediated hemolysis and thrombosis. Pegcetacoplan, the first complement component 3 (C3) inhibitor for PNH, increased hemoglobin (Hb) levels in complement component 5 inhibitor (C5i)-experienced and -naive adult patients with PNH in 2 phase 3 clinical trials (PEGASUS [NCT03500549] and PRINCE [NCT04085601], respectively). This integrated analysis of data from the pivotal phase 3 trials and the subsequent open-label extension (study 307; NCT03531255) evaluated the long-term efficacy and safety of pegcetacoplan for PNH treatment. Methods: For this integrated analysis, baseline was defined as the initiation of pegcetacoplan, regardless of when in the trials this occurred. Patients initially received pegcetacoplan 1080 mg subcutaneously twice weekly; dose escalations to once every 3 days or 3 times weekly were permitted. Efficacy was evaluated from baseline up to Weeks 132 (2.5 years, PRINCE) and 156 (3 years, PEGASUS) by Hb, lactate dehydrogenase (LDH; upper limit of normal [ULN] 226 IU/L), absolute reticulocyte count (ARC), and indirect bilirubin values; Functional Assessment of Chronic Illness Therapy (FACIT)-Fatigue scores; and transfusion avoidance rates (percentages of patients who did not require a transfusion during treatment). Safety was assessed by incidence of adverse events (AEs) and serious AEs (SAEs) during pegcetacoplan monotherapy for up to 3 years. Results: Of the 133 patients in the phase 3 trials (PEGASUS, 80; PRINCE, 53), 114 enrolled in the extension study (PEGASUS, 64; PRINCE, 50). At least 75% had received a transfusion in the year before enrolling in PEGASUS or PRINCE. Prior to pegcetacoplan initiation, mean (SD) Hb levels were 8.95 (1.09) g/dL in PEGASUS, 9.27 (1.44) g/dL in PRINCE, and 9.08 (1.24) g/dL in the total population; median (interquartile range) LDH levels were 217.0 (184.8, 276.5) IU/L in PEGASUS, 1964.0 (1409.0, 2503.3) IU/L in PRINCE; and mean (SD) FACIT-Fatigue scores were 31.6 (11.7) in PEGASUS, 36.6 (10.0) in PRINCE, and 33.6 (11.3) in the total population. After pegcetacoplan initiation, mean Hb levels markedly improved from baseline and remained stable through Weeks 132 (2.5 years, PRINCE) and 156 (3 years, PEGASUS) ( Figure). Median LDH rapidly decreased and stabilized below the ULN ( Figure). Improvements in ARC and indirect bilirubin were similarly maintained. Average FACIT-Fatigue scores increased (indicating less fatigue) rapidly and were maintained near the general population norm of 43.6. Annual transfusion avoidance ranged from 71%-79% in PEGASUS and 80%-86% in PRINCE, with 52% of patients from PEGASUS avoiding transfusion for up to 3 years of pegcetacoplan treatment and 67% of patients from PRINCE avoiding transfusion for up to 2.5 years. Overall, &amp;gt;92% patients had compliance rates of at least 95%. Over 3 years, most patients experienced an AE; SAEs were reported in 50.0% of patients, with 4.5% experiencing a SAE deemed related to pegcetacoplan. Overall, 17 patients discontinued pegcetacoplan due to an AE; of those, 9 discontinued due to a hemolytic disorder, 7 of which discontinued within 1 year of starting pegcetacoplan. Over 3 years, 4 (3.0%) deaths occurred, none were deemed related to pegcetacoplan; 3 (2.3%) patients experienced a thrombotic event (in the context of multiple associated comorbidities or discontinuation of pegcetacoplan) and no cases of meningitis were reported. Overall, no new or unexpected safety findings were identified. Conclusions: Rapid improvements in Hb, LDH, ARC, indirect bilirubin, and FACIT-Fatigue values were observed and maintained up to 3 years in C5i-experienced patients and up to 2.5 years in C5i-naive patients. The transfusion burden was significantly reduced. No new safety findings were identified. This analysis demonstrates sustained efficacy and continued safety of long-term pegcetacoplan for patients with PNH, regardless of prior C5i treatment.