A Study in Adult Patients With Paroxysmal Nocturnal Hemoglobinuria (PNH) to Evaluate How Safe Long-term Treatment With Pozelimab + Cemdisiran Combination Therapy is and How Well it Works.

Key Inclusion Criteria:

Patients Entering from the Parent Study

1. Patients with PNH who have completed, without permanent discontinuation, studytreatment in the parent study (R3918-PNH-2021[NCT05133531]), including thepost-Open-label treatment period (OLTP) transition period, if applicable.

2. Willing and able to comply with clinic visits and study-related procedures,including meningococcal vaccinations required per protocol.

Patients Entering with C5 polymorphism

1. Patients with PNH who have a documented C5 polymorphism rendering them refractory toeculizumab or ravulizumab (eg, p.Arg885His, p.Arg885Cys), as described in theprotocol

2. Diagnosis of PNH confirmed by high-sensitivity flow cytometry testing with PNHgranulocytes or monocytes

3. Active disease, as defined by the presence of 1 or more PNH-related sign or symptomas described in the protocol

4. LDH level ≥2 × upper limit of normal (ULN) at the screening visit

5. Willing and able to comply with clinic visits and study-related procedures,including meningococcal vaccinations required per protocol

Key Exclusion Criteria:

Patients Entering from the Parent Study

1. Significant protocol deviation(s) in the parent study based on the investigator'sjudgment and to the extent that these would (if continued) impact the studyobjectives and/or safety of the patient

2. Any new condition or worsening of an existing condition which, in the opinion of theinvestigator, would make the patient unsuitable for enrollment or could interferewith the patient participating in or completing the study

Patients Entering with C5 polymorphism

1. Prior treatment with complement inhibitors within 5 half-lives of the respectiveagent prior to screening, except for prior eculizumab or ravulizumab which are notexclusionary

2. Receipt of an organ transplant, history of bone marrow transplantation or otherhematologic transplant

3. Not meeting meningococcal vaccination requirements and, at a minimum, documentationof quadrivalent meningococcal vaccination within 5 years prior to enrollment andserotype B vaccine within 3 years prior to enrollment as described in the protocol

4. Positive hepatitis B surface antigen or hepatitis C virus Ribonucleic acid (RNA)during screening

5. Patients with known HIV with history of opportunistic infections in the last 1 yearas described in the protocol

6. Known hereditary complement deficiency

7. Documented history of active, uncontrolled, ongoing systemic autoimmune diseases

8. Documented history of liver cirrhosis or patients with liver disease with evidenceof current impaired liver function or patients with elevations in Alanineaminotransferase (ALT) or Aspartate aminotransferase (AST) (unrelated to PNH or itscomplications) as described in the protocol

Note: Other protocol-defined Inclusion/ Exclusion Criteria apply