This is a randomized, parallel group, active-controlled, open-label, Phase III study comparing the efficacy and safety of obinutuzumab versus cyclophosphamide combined with glucocorticoids in patients with primary membranous nephropathy (pMN). Approximately 144 patients with pMN who have been diagnosed by biopsy or serum anti-PLA2R antibody will be enrolled.

Intervention: Intravenous infusion of 1,000 mg obinutuzumab at weeks 0, 2, 24 and 26 Comparator: Cyclical cyclophosphamide and glucocorticoids Methylprednisolone 500 mg iv will be given for 3 consecutive days at the start of month 1,3,5 and followed by prednisone 0.5mg/kg/d (max 40 mg/d) for 27 days.

Oral cyclophosphamide will be given for 30 days in month 2, 4, 6.

Inclusion Criteria:

• Aged 18～75 years (including 18 and 75)old at the time of signing Informed Consent Form
• pMN patients diagnosed according to renal biopsy (original biopsy needs to include light, immunofluorescence, and electron microscopy) within 5 years or serum anti-PLA2R antibody (≥14 RU/ml )
• 24-hour UPCR ≥ 4 g/g and serum albumin (sALB) < 30 g/L,despite being treated with ACEi and/or ARB for ≥ 6 months prior to screening, or 24-hour UPCR ≥ 5 g/g and sALB < 30 g/L , despite being treated with ACEi and/or ARB for ≥ 3 months prior to screening; or 24-hour UPCR ≥ 8 g/g and sALB < 25 g/L, despite being treated with ACEi and/or ARB for ≥ 1 month prior to screening,.
• eGFR ≥40 mL/min/1.73m2 (CKD-EPI), a renal biopsy is required to exclude renal damage due to other co-morbidities if eGFR <60mL/min/1.73 m2.
• Ability to comply with the study protocol, in the investigator's judgment

Exclusion Criteria:

• Patients with a secondary cause of MN (e.g. hepatitis B, systemic lupus erythematosus, medications, malignancies)
• Type 1 or 2 diabetes mellitus
• eGFR <40 mL/min/1.73m2 (CKD-EPI) or dialysis or kidney transplantation
• Evidence of 50% reduction in proteinuria or serum anti-PLA2R antibody within 6 months prior to screening

In signing the final protocol, every participating Investigator agrees to keep all information and results concerning the study and the investigational product confidential for as long as the data remain unpublished. The confidentiality obligation applies to all personnel involved at the investigational site.

In the conduct of this trial 10 centers will be involved. The size of the author list will be dictated by the journal(s) to which the abstract is submitted, but will include Professor Chuan-Ming Hao, the Primary Investigator for the study, as first or corresponding author. Other named authors will be included up to the maximum number allowed by the journal and will be selected based on recruitment at individual sites. If data is to be presented outside the individual institutions involved in the study, the Sponsor and Steering Committee should approve the content.