Trial to Assess Safety and Efficacy of MOR202 in Anti-PLA2R + Membranous Nephropathy (aMN)

Key Inclusion Criteria: * \> 18 to \< 80 years (at date of signing informed consent form \[ICF\]). * Urine protein to creatinine ratio (UPCR) of ≥ 3.000 g/g OR proteinuria ≥ 3.500 g/24 h from 24-h urine at screening * Active anti-PLA2R antibody positive MN in need of immunosuppressive therapy (IST) according to investigator judgement and diagnosed on the basis of a biopsy, archival biopsy acquired within 5 years prior to screening is acceptable. * Estimated glomerular filtration rate ≥ 50 ml/min/1.73m² or ≥ 30 and \<50 ml/min/1.73m², and interstitial fibrosis and tubular atrophy score of less than 25% on a renal biopsy obtained within the last 6 months prior to start of screening. * Not in spontaneous remission despite proper treatment with ACEIs, ARBs (sufficient dose and treatment duration) as per clinical practice and scientific guidelines. If the subject is intolerant to an ACEI or ARB, the reason must be documented and approval obtained prior to enrolment. * Systolic blood pressure BP ≤150 mmHg and diastolic BP ≤100 mmHg after 5 minutes of rest * Vaccinated against Pneumococcus within the last 5 years prior to date of signing informed consent (subjects may be vaccinated during screening to meet this criterion; interval to first dose of MOR202 must be at least 14 days). * Cohort 1 comprises newly diagnosed or relapsed subjects: Serum anti-PLA2R antibodies ≥50.0 RU/mL * Cohort 2 comprises therapy refractory subjects: a Subject did not achieve immunological remission after prior IST(s) as documented by the investigator AND b Subject is without promising standard therapeutic options as documented by the investigator (i.e. investigator expects efficacy or safety issues with remaining IST options) AND c Serum anti-PLA2R antibodies ≥ 20.0 RU/mL measured at screening Note: France will only enroll patients in Cohort 2. Key Exclusion Criteria: * Hemoglobin \< 80 g/L. * Thrombocytopenia: Platelets \< 100.0 x 109/L. * Neutropenia: Neutrophils \< 1.5 x 109/L. * Leukopenia: Leukocytes \< 3.0 x 109/L. * Hypogammaglobulinemia: Serum immunoglobulins ≤ 4.0 g/L. Subjects may receive supportive therapies to meet the above criteria * B-cells \< 5 x 106/L. * Secondary cause of MN (e.g. Systemic lupus erythematosus, medications, malignancies) * Concomitant renal disease other than MN (e.g., diabetic renal disease, lupus nephritis, IgA nephropathy).