Evaluation of the Long-Term Safety and Efficacy of Pegcetacoplan Treatment for Paroxysmal Nocturnal Hemoglobinuria Patients: An Extension Study
Authors: Hoffman Kate , Machaidze Zurab , Yeh Michael , Weitz Ilene C. 
Published: November 2021

Abstract
Background: Paroxysmal nocturnal hemoglobinuria (PNH) is a rare, potentially life-threatening disease characterized by complement mediated hemolysis and thrombosis. Current C5-inhibitors, such as eculizumab and ravulizumab, are able to partially treat these symptoms by controlling intravascular but not extravascular hemolysis, manifesting as persistent anemia in up to 72% of treated patients and transfusion dependence in up to 36% of patients.
Pegcetacoplan (PEG) is a Food and Drug Administration (FDA)-approved C3-inhibitor that controls both intravascular and extravascular hemolysis (IVH and EVH). In the PEGASUS phase 3, multi- center, active-comparator controlled, randomized trial (NCT03500549), improvements in hemoglobin levels from baseline to Week 16 demonstrated the superiority of PEG over eculizumab; 85% of the patients receiving PEG achieved transfusion independence when compared with the 15% of patients on eculizumab. The extension study will evaluate the long-term safety and efficacy of PEG in patients with PNH.
Acute hemolytic (AH) events occurred during the PEG clinical development program. As part of the long-term extension study, we aim to better understand how to manage acute hemolytic events through dose adjustments in patients treated with PEG
Aims: Determine the long-term safety and efficacy of PEG for PNH treatment, as well as evaluate a treatment regimen to address acute hemolytic (AH) events in these patients.
Study Design: The PEG extension study (NCT03531255) is an active, multi-center, open-label, non-randomized trial with an estimated enrollment of up to160 adult PNH patients (≥18 years), who have completed prior PEG trials - phase 1b PADDOCK (NCT02588833) and PHAROAH (NCT02264639), phase 2a PALOMINO (NCT03593200), and the phase 3 PEGASUS (NCT03500549) and PRINCE (NCT04085601) trials. The main study will determine long-term safety and efficacy of PEG dosing on complement-mediated hemolytic activity, hemoglobin levels, and transfusion independence in PNH patients. For enrolled subjects experiencing AH episodes, a substudy to evaluate safety and efficacy of intensive SC or IV dosing of PEG acute treatments will be offered. Dose adjustments will be offered for AH subjects declining to enter the substudy, but continuing to participate in the main study.
Inclusion criteria for the management of AH substudy specify that lactate dehydrogenase (LDH) levels in patients must be &gt;2 times the upper limit of normal, accompanied by new or worsening clinical signs of hemolysis (hemoglobinuria, fatigue, decreased hemoglobin, etc.). Notable exclusion criteria include subjects who have withdrawn from a previous PEG trial, co-morbidities and infections that can enhance risk profiles for adverse events or confound study interpretation, and complement deficiency.
The safety population consisting of patients that will receive at least one dose of the drug will be used for all efficacy analyses. Descriptive statistics will be used in documenting changes from baseline, along with qualitative descriptors (improved, maintained, or worsened).
Intervention: Patients in the long-term extension study receive subcutaneous (SC) administration of 1080 mg PEG twice weekly, every 3 days, or 3 times weekly. For AH events substudy, patients with steady-state PEG dose of 1080 mg SC twice weekly will receive a loading dose of 1080 mg IV once, or 1080 mg SC every 24 hours for 3 doses, followed by increase in maintenance dose to 1080 mg SC every 3 days; for those receiving 1080 mg SC every 3 days, identical loading dose will be followed by subsequent maintenance dose of 1080 mg SC 3 times weekly.
Primary and Secondary Outcome Measures: The study will monitor safety outcomes such as occurrence and severity of adverse events within a 2-year timeframe from baseline. Additional biomarkers include recurrent acute hemolysis, thromboembolism, laboratory and electrocardiogram (ECG) parameters. Efficacy endpoint measurements over a 48-week timeframe include mean change from baseline levels of hemoglobin, LDH, and indirect bilirubin, absolute reticulocyte counts, RBC transfusions, and functional assessment of fatigue scale scores.
Results: Trial results are anticipated in 2022, upon study completion.

Disclosures
Hoffman: Apellis Pharmaceuticals, Inc.: Current Employment, Current equity holder in publicly-traded company. Machaidze: Apellis Pharmaceuticals: Current Employment, Current equity holder in publicly-traded company. Yeh: Apellis Pharmaceuticals, Inc.: Current Employment, Current equity holder in publicly-traded company. Weitz: Alexion: Consultancy, Honoraria, Speakers Bureau; Apellis Pharmaceuticals: Consultancy, Honoraria; Biocryst: Consultancy, Honoraria; Novartis Corporation: Consultancy, Honoraria; Sanofi Genxyme: Consultancy, Honoraria.

OffLabel Disclosure:
Pegcetacoplan is a Food and Drug Administration approved C3-inhibitor that controls both intravascular and extravascular hemolysis. As part of the long-term extension study, we aim to better understand how to manage acute hemolytic events through dose adjustments in patients treated with pegcetacoplan.