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

Thrombosis at Unusual Sites: Focus on Myeloproliferative Neoplasms and Paroxysmal Nocturnal Hemoglobinuria

Patients with thrombosis at an unusual site will need to be explored for rare causes of thrombosis. Two of these rare causes include myeloproliferative neoplasms (MPNs) and paroxysmal nocturnal hemoglobinuria (PNH). It is important not to overlook these causes, since they require specific management, in addition to antithrombotic treatment (anticoagulants, antiplatelet agents). Unusual sites of venous thrombosis include upper extremity veins, splanchnic veins, cerebral veins, and retinal veins, and unusual sites of arterial thrombosis include renal, adrenal, splenic and mesenteric arteries, and intracardiac and aortal locations. Suspicion for MPN and PNH should be raised if there are concomitant abnormalities, such as elevated or decreased blood cell counts or splenomegaly. Diagnosis of MPN and PNH should include JAK2V617F mutational screening as well as flow cytometric assessment of GPI-anchored proteins in the peripheral blood, respectively. Specific treatments for MPN may include phlebotomy or cytoreductive drugs such as hydroxyurea, anagrelide, pegylated interferon-alpha, or Janus kinase inhibitors. Drugs used for PNH treatment include terminal complement inhibitors, such as eculizumab and ravulizumab, as well as proximally acting inhibitors such as pegcetacoplan or iptacopan. Patients with MPN and PNH are at high risk for thrombosis during their entire lifetime and should thus be followed by specialists experienced in the care of these diseases.

Population Pharmacokinetic and Pharmacokinetic/Pharmacodynamic Analyses of Pegcetacoplan in Patients with Paroxysmal Nocturnal Hemoglobinuria

BACKGROUND AND OBJECTIVE

Paroxysmal nocturnal hemoglobinuria is a rare blood disorder characterized by life-threatening hemolysis and thrombosis. Complement C5 inhibitor therapy improves symptoms and life prognosis; however, it can result in insufficient hemolysis control, with residual intravascular hemolysis and extravascular hemolysis in some patients. Pegcetacoplan, the first complement C3 inhibitor approved for patients with paroxysmal nocturnal hemoglobinuria, targets both intravascular and extravascular hemolysis. This analysis evaluated population pharmacokinetic/pharmacodynamic profiles of pegcetacoplan.

METHODS

Pooled clinical study data were used to predict pegcetacoplan concentrations and biomarker responses indicative of hemolysis (hemoglobin and lactate dehydrogenase) over time, including the impact of patient characteristics and prior or concurrent complement C5 inhibitor treatment, to support the approved dose of subcutaneous pegcetacoplan 1080 mg twice weekly.

RESULTS

The population pharmacokinetoc analysis included 284 subjects, and the pharmacokinetic/pharmacodynamic analysis included 165 subjects. Subcutaneous pegcetacoplan 1080 mg twice weekly resulted in rapid serum exposures and robust biomarker response within 4 weeks after treatment initiation. Steady-state serum concentrations demonstrated consistent exposure (median ≥ 600 µg/mL) with minimal peak-to-trough variation. The median effective half-life was 8.6 days in patients with paroxysmal nocturnal hemoglobinuria. Body weight significantly impacted pegcetacoplan exposure, and other covariates impacted hemoglobin (sex and creatinine clearance) or lactate dehydrogenase (prior or concurrent complement C5 inhibitor treatment); however, effects were not clinically meaningful.

CONCLUSIONS

The approved dose of pegcetacoplan is predicted to produce rapid and sustained exposure and robust hemoglobin and lactate dehydrogenase responses in adult patients with paroxysmal nocturnal hemoglobinuria, with no initial dose adjustments required for any specific patient population.

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.

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.