Pozelimab and Cemdisiran Combination Treatment in Adult Participants With Paroxysmal Nocturnal Hemoglobinuria Who Have Received Pozelimab Monotherapy

The primary objective of the study is to evaluate the safety and tolerability of 2 dosing regimens of pozelimab and cemdisiran combination therapy during the open-label treatment period (OLTP) The secondary objectives of the study are: * To evaluate the effect of the combination treatment on the following parameters of intravascular hemolysis: lactate dehydrogenase (LDH) control, breakthrough hemolysis, and inhibition of total complement hemolysis activity (CH50) * To evaluate the effect of the combination treatment on hemoglobin levels * To evaluate the effect of the combination treatment on red blood cell (RBC) transfusion requirements * To evaluate the effect of the combination treatment on clinical outcome assessments (COAs) measuring fatigue and health related quality of life * To assess the concentrations of total pozelimab in serum and total complement component (C) 5 and cemdisiran in plasma * To assess immunogenicity to pozelimab and cemdisiran * To evaluate the long-term safety and efficacy of pozelimab and cemdisiran in an optional open-label extension period (OLEP) * To assess safety after treatment intensification with pozelimab and cemdisiran