A Study to Assess Effectiveness and Safety of Efgartigimod in Chinese Patients with Primary Membranous Nephropathy (ZL-1103-014)

Inclusion Criteria: * Aged ≥18 years when signing the informed consent form (ICF) * Capable of providing signed informed consent and complying with protocol requirements * Diagnosis of idiopathic (primary) MN confirmed by renal biopsy within 24 months before randomization. A renal biopsy may be taken at any time during the screening period to confirm the diagnosis of MN for participant eligibility, if the most recent biopsy was performed greater than 24 months before randomization * Receiving stable dose at maximum tolerated or allowed dose of ACEi and/or ARB for at least 12 weeks before randomization * Agree to use contraceptives consistent with local regulations. Full inclusion criteria can be found in the protocol Exclusion Criteria: * Active or chronic infection requiring treatment * Diagnostic renal biopsy showing evidence of crescent formation in glomeruli, suggestive of an alternative or additional diagnosis to pMN; evidence on renal biopsy of \>50% interstitial fibrosis/tubular atrophy in the cortical area * History of malignancy unless deemed cured by adequate treatment with no evidence of recurrence for ≥3 years before randomization. * Any evidence of diabetic glomerulopathy on renal biopsy that is: Greater than Class I diabetic glomerulopathy, or Class I diabetic glomerulopathy with a history of poor diabetic control (eg, HbA1c ≥9.0%) since time of biopsy * Currently on renal dialysis or expected to require dialysis during study period * Previous kidney transplantation or planned transplantation during study period * Any other known autoimmune disease that, requires systemic immunosuppressive treatments, or in the opinion of the investigator, would interfere with an accurate assessment of clinical symptoms of pMN or put the participant at undue risk * Clinical evidence of other significant or uncontrolled serious diseases (ie, cardiovascular, pulmonary, hematologic, gastrointestinal, hepatic, renal, neurological), have had a recent major surgery, or have any other condition, that in the opinion of the investigator, could confound the results of the study or put the participant at undue risk * Use of complementary therapies, including Traditional Chinese Medicine, herbs, or procedures (eg, acupuncture) within 4 weeks before randomization that can potentially interfere with the efficacy and safety of participants as assessed by the investigator * Received live/live-attenuated vaccine within 28 days before randomization. The receipt of any inactivated, subunit, polysaccharide, or conjugate vaccine at any time before screenings is not considered exclusionary. It is recommended that participants are up to date with vaccination before the first dose of IMP * Previously participated in a clinical study with efgartigimod * SARS-CoV-2 positive test at screening. The test is required regardless of whether the participant has been vaccinated * Known hypersensitivity or contraindication to efgartigimod, or any excipient of the IMP * In the opinion of the investigator, current or history of (ie, within 12 months of randomization) alcohol, drug, or medication abuse * Pregnant or lactating females and those who intend to become pregnant during study participation * Any conditions or circumstances that in the opinion of the investigator may make the participant unsuitable for the study