A Phase 2a, Randomized, Double-blind, Placebo-controlled, Parallel-Group, Multicenter Study to Evaluate the Efficacy, Safety, Tolerability, Pharmacokinetics, Pharmacodynamics, and Immunogenicity of ALXN1920 in Adult Participants With PMN (Primary Membranous Nephropathy) Who Are at a High Risk for Disease Progression

Inclusion Criteria: * Participants who have a documented diagnosis of PMN, established by positive antiPLA2R antibody level (\> 20 RU/mL) at Screening, which must be confirmed by a central laboratory * Participants are willing to receive the background Standard of Care (SoC) * Participants at high risk for disease progression, defined as: 1. Receiving ACE inhibitor or ARB for a minimum of 8 weeks prior to Screening, with the dose titrated to the maximally tolerated level. Participants with less than 8 weeks on ACE inhibitor or ARB before Screening or who have not yet reached maximally tole…