A Study to Evaluate How Pozelimab + Cemdisiran Combination Therapy Works in Adult Patients With Paroxysmal Nocturnal Hemoglobinuria (PNH) Whose Current Treatment is Not Working Efficiently

This study is researching a treatment combination with two experimental drugs called pozelimab and cemdisiran referred to as "study drugs". Researchers are looking for a better way to treat Paroxysmal Nocturnal Hemoglobinuria (PNH). The aim of the study is to see how well the pozelimab and cemdisiran combination works to lower hemolysis in participants whose PNH has been not well controlled even after taking other complement component 5 (C5) inhibitors, eculizumab/eculizumab biosimilar, ravulizumab or crovalimab. The study is looking at several other research questions, including: * What side effects may happen from taking the study drugs? * How much of the study drugs are in the blood at different times? * Whether the body makes antibodies against the study drug (which could make the study drugs not work as well or could lead to side effects)