A Study to Evaluate How Safe Pozelimab + Cemdisiran Combination Therapy is and How Well it Works in Adult Patients With Paroxysmal Nocturnal Hemoglobinuria (PNH) Who Have Not Recently Received or Have Not Received Complement Inhibitor Treatment

Key Inclusion Criteria:

1. Diagnosis of PNH confirmed by high-sensitivity flow cytometry testing with PNHgranulocytes or monocytes as described in the protocol

2. Active disease, as defined by the presence of 1 or more PNH-related signs orsymptoms as described in the protocol

3. LDH level ≥2 × ULN at the screening visit

4. Willing and able to comply with clinic/remote visits and study-related procedures,including completion of the full series of meningococcal vaccinations required perprotocol

Key Exclusion Criteria:

1. Prior treatment with eculizumab within 3 months prior to screening, ravulizumabwithin 6 months prior to screening, or other complement inhibitors within 5half-lives of the respective agent prior to screening

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

3. Body weight <40 kilograms at screening visit

4. Planned use of any complement inhibitor therapy other than study drugs during thetreatment period

5. Not meeting meningococcal vaccination requirements and, at a minimum documentationof quadrivalent meningococcal vaccination within 5 years prior to the screeningvisit and serotype B vaccine within 3 years prior to the screening visit asdescribed in the protocol.

6. Any contraindication for receiving Neisseria meningitidis vaccinations (serotypesACWY and B).

7. Unable to take antibiotics for meningococcal prophylaxis (if required by localravulizumab [Cohort A] or eculizumab [Cohort B] prescribing information, whereavailable, or national guidelines/local practice, or if necessary whenadministration of the first dose of the vaccination is less than 2 weeks prior tostudy treatment initiation)

8. Any active, ongoing infection or a recent infection requiring ongoing systemictreatment with antibiotics, antivirals, or antifungals within 2 weeks of screeningor during the screening period

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

Note: Other protocol-defined Inclusion/ Exclusion Criteria apply