Pharmacokinetics, pharmacodynamics, efficacy, and safety of ravulizumab in pediatric paroxysmal nocturnal hemoglobinuria

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare hematologic disease of uncontrolled terminal complement activation leading to intravascular hemolysis, thrombotic events and increased morbidity and mortality. This phase 3, open-label, single-arm, multicenter study 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 end points were pharmacokinetic and pharmacodynamic parameters to confirm complement component 5 (C5) inhibition by ravulizumab; secondary end points 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%) eculizumab-experienced, were enrolled. Ravulizumab Ctrough levels were above the pharmacokinetic threshold of 175 jig/mL in the PEP and EP except in 1 patient. At the end of the study, pre- and post-infusion mean +/- standard deviation serum ravulizumab concentrations were 610.50 +/- 201.53 jig/mL and 518.29 +/- 109.67 jig/mL for eculizumab-naive and eculizumab-experienced patients, respectively. After the first ravulizumab infusion, serum-free C5 concentrations were <0.5 jig/mL in both cohorts until the end of the study (0.061 +/- 0.021 jig/mL and 0.061 +/- 0.018 jig/mL for eculizumab-naive and eculizumabexperienced 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. This trial was registered at www.ClinicalTrials.gov as #NCT03406507.