A Study to Examine the Efficacy and Safety of Zanubrutinib Given to Adults With Primary Membranous Nephropathy

Inclusion Criteria:

1. Biopsy-confirmed PMN within 5 years before the initial screening (ie, the day the informed consent is signed)
2. UPCR (based on 24-hour urine collection) > 3.5 at initial screening and at confirmation assessment
3. Treatment with a maximally tolerated or allowed dose of an angiotensin-converting enzyme inhibitor (ACEI) or angiotensin II receptor blocker (ARB) for ≥ 24 weeks before randomization (12 weeks before initiation of study drug for Part 1) and with adequate blood pressure control (blood pressure < 130/80 mmHg, measured on ≥ 2 occasions [not on the same day] within 4 weeks before the assignment of study treatment)
4. Anti-PLA2R antibody > 50 RU/mL at confirmation assessment (Part 1 only)

Exclusion Criteria:

1. Participants with a secondary cause of membranous nephropathy
2. Type 1 or 2 diabetes mellitus with hemoglobin A1c (HbA1c) ≥ 7% at screening
3. Severe renal disease as determined by rapid decline in eGFR (defined as > 15 mL/min/1.73m^2 within 24 weeks prior to randomization, not otherwise explained)
4. A known history of a primary immunodeficiency or an underlying condition such as human immunodeficiency virus (HIV) infection or splenectomy that predisposes the participant to infections
5. Patients at risk for tuberculosis at screening
6. Known infection with serologic status reflecting active or chronic hepatitis B virus infection, or presence of hepatitis C virus antibody
7. Severe hepatic insufficiency (Child-Pugh C)
8. Clinically significant cardio-cerebrovascular diseases

Note: Other protocol defined Inclusion/Exclusion criteria may apply.