This study is researching an experimental treatment combination with two experimental drugs called pozelimab and cemdisiran. The study is focused on people with paroxysmal nocturnal hemoglobinuria (PNH). The aim of this study is to see how safe and effective the pozelimab + cemdisiran combination is for people with PNH in the long term. The pozelimab + cemdisiran combination may be referred to as "study drugs" in this section.
This study is looking at several other research questions, including:
* How effective is the pozelimab + cemdisiran combination? * What side effects may happen from taking the study drugs? * How much of each study drug is in the blood at different times? * Whether the body makes antibodies against the study drugs (which could make the drugs less effective or could lead to side effects)
Patients with PNH who have completed, without permanent discontinuation, study treatment in the parent study (R3918-PNH-2021[NCT05133531]), including the post-Open-label treatment period (OLTP) transition period, if applicable.
Willing and able to comply with clinic visits and study-related procedures, including meningococcal vaccinations required per protocol.
Patients with PNH who have a documented C5 polymorphism rendering them refractory to eculizumab or ravulizumab (eg, p.Arg885His, p.Arg885Cys), as described in the protocol
Diagnosis of PNH confirmed by high-sensitivity flow cytometry testing with PNH granulocytes or monocytes
Significant protocol deviation(s) in the parent study based on the investigator's judgment and to the extent that these would (if continued) impact the study objectives and/or safety of the patient
Any new condition or worsening of an existing condition which, in the opinion of the investigator, would make the patient unsuitable for enrollment or could interfere with the patient participating in or completing the study
Prior treatment with complement inhibitors within 5 half-lives of the respective agent prior to screening, except for prior eculizumab or ravulizumab which are not exclusionary
Receipt of an organ transplant, history of bone marrow transplantation or other hematologic transplant