Switching between complement inhibitors in paroxysmal nocturnal hemoglobinuria: Analysis of strategy, efficacy, and safety.

Paroxysmal nocturnal hemoglobinuria (PNH) is an ultra-orphan disease. In 2026, approved complement inhibitors (CIs) for PNH include three C5 inhibitors (C5i) and three proximal inhibitors (PIs). Clinical trials for the approved PI pegcetacoplan, iptacopan, and C5i + danicopan had clear protocols for changing from terminal to PI, extrapolated into real-world practice. There is no guidance for patients changing from a PI to a different CI. We present the largest international cohort to date. The inclusion criteria were as follows: patients established on a PI, who have changed treatment to a different CI. Sixty-five patients with a median age at PNH diagnosis of 40 years were included. Indications for CI switch were as follows: hemolysis (extravascular/recurrent breakthrough/not specified), side effects, trial termination, patient choice, and other. CI changes (149) were classified as (1) terminal-to-proximal (75/149), 6 hemolytic events reported within 14 days of CI change; (2) proximal-to-proximal (45/149), 2 hemolytic events reported within 14 days of CI change; and (3) proximal-to-terminal (29/149), 13 hemolytic events within 14 days of CI change. This is the largest cohort of PNH patients facing multiple CI changes. With the increasing availability of different CI classes, patients may experience several treatment changes over their disease course. CI should not be interrupted. The cohort would suggest that overlapping treatment for patients changing from PI to another CI is not required. Tapering of treatment does not seem to be effective at preventing hemolysis complications. Patients should be monitored closely for hemolysis, especially when changing from proximal-to-terminal inhibition. Prospective clinical/laboratory analysis is recommended for further clarification management for this patient group.