Paroxysmal nocturnal hemoglobinuria (PNH) is a rare hematologic disease of uncontrolled terminal complement activation leading to intravascular hemolysis, thrombotic events, increased morbidity and mortality. This phase 3, open-label, single-arm multicenter study (NCT03406507) evaluated ravulizumab treatment in eculizumab-naive or -experienced pediatric patients (aged <18 years) with PNH over a 26-week primary evaluation period (PEP) and 4-year extension period (EP). Patients included in the study received weight based intravenous ravulizumab dosing. Primary endpoints were pharmacokinetic and pharmacodynamic parameters to confirm complement component 5 (C5) inhibition by ravulizumab; secondary endpoints assessed the efficacy (including percentage change in lactate dehydrogenase levels over time) and safety of ravulizumab. Thirteen patients, 5 (38.5%) eculizumab-naive and 8 (61.5%) experienced, were enrolled. Ravulizumab Ctrough levels were above the pharmacokinetic threshold of 175 μg/mL in the PEP and EP except in one patient. At the end of the study, pre-and post-infusion mean ± standard deviation serum ravulizumab concentrations were 610.50 ± 201.53 μg/mL and 518.29 ± 109.67 μg/mL for eculizumab-naive and -experienced patients, respectively. After the first ravulizumab infusion, serum free C5 concentrations were <0.5 µg/mL in both cohorts until the end of the study (0.061 ± 0.021 μg/mL and 0.061 ± 0.018 μg/mL for eculizumab-naive and -experienced patients, respectively). Compared with baseline, ravulizumab improved and maintained efficacy outcomes in both groups. Ravulizumab had an acceptable safety profile with no new safety signals identified, and provided immediate, complete, and sustained terminal complement inhibition, translating to clinical benefit for pediatric patients with PNH.-