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)
Diagnosis of PNH confirmed by a history of high-sensitivity flow cytometry from prior testing
Currently treated with marketed eculizumab, ravulizumab, or crovalimab at the labeled dose for at least 6 months
LDH persistently > 1.5 × Upper Limit of Normal (ULN) in the previous 6 months that the Principal Investigator (PI) attributes is due to intravascular hemolysis
At least 2 screening LDH values from different visits as described in the protocol
Receipt of an organ transplant, history of bone marrow transplantation or other hematologic transplants
Body weight <40 kilograms at screening visit
Patients with a known or suspected C5 mutation that is refractory to their current C5i treatment as described in the protocol
Any active or ongoing infection within 2 weeks of screening or during the screening period or any recent infection as described in the protocol