A First-in-Human Safety and Efficacy Study of ALN-CFB, a Small Interfering RNA (siRNA) Targeting Complement Factor B, in Adult Participants With Paroxysmal Nocturnal Hemoglobinuria With Persistent Anemia on a C5 Inhibitor

The protocol will be amended to describe Part B of the study after Part A data have been analyzed.

Key Inclusion Criteria:

• Has been diagnosed with PNH confirmed by a history of high flow cytometry from prior testing
• Treated with a stable dose of C5 inhibitor (eculizumab or approved eculizumab biosimilar, ravulizumab, or crovalimab) for at least 24 weeks prior to screening visit, as described in the protocol
• Has hemoglobin ≤10.5 g/dL at screening visit 1, with evidence of anemia prior to this visit, as described in the protocol
• Has peripheral blood reticulocyte count of ≥100 x 10^9/L at screening visit 1

Key Exclusion Criteria:

• Has history of bone marrow transplantation or receipt of an organ transplant
• Has history of meningococcal infection or similar recurrent infections by other encapsulated bacterial organisms
• Has any active, ongoing infection or a recent infection requiring ongoing systemic treatment with antibiotics, antivirals, or antifungals within 2 weeks of screening or during the screening period
• Has laboratory evidence of bone marrow failure, as described in the protocol
• Have recent, unstable medical conditions, not related to PNH or PNH-related complications, as described in the protocol

NOTE: Other Protocol Defined Inclusion / Exclusion Criteria Apply