Atacicept in Multiple Glomerular Diseases

Inclusion Criteria: * Weight of at least 40 kg * On a stable prescribed standard of care (SoC) treatment regimen according to local guidelines and the specific requirements for each disease * Systolic blood pressure ≤160 mmHg and diastolic blood pressure ≤90 mmHg at Screening. For participants aged ≥10 to \<18 years, the average of 3 separate systolic and/or diastolic blood pressures \<95th percentile for age, gender, and height Diagnosis of IgAN, IgAVN, pMN, MCD, FSGS, or primary nephrotic syndrome For patients enrolling in IgAN cohorts (eligibility varies by cohort): * Age ≥ 10 years * Biopsy proven IgAN or IgAVN, * UPCR ≥ 0.5 g/g * eGFR≥ 20 mL/min/1.73m2 For patients enrolling in pMN cohorts (eligibility varies by cohort): * Age ≥ 18 years * Biopsy-proven pMN * Anti PLA2R antibodies ≥ 25 RU/mL * UPCR ≥ 1.5 g/g * At low risk for spontaneous remission (based on severity or duration of disease) For patients enrolling in Nephrotic Syndrome cohorts (MCD, FSGS, or pediatric idiopathic nephrotic syndrome): * Age ≥ 10 years * eGFR≥30 mL/min/1.73m2 * Biopsy diagnosis of primary MCD or FSGS (adults) or challenging clinical course with steroids in children (frequenlty relapsing, steroid-dependent, or steroid-resistant) * UPCR ≥ 1.0 g/g at Screening, * Evidence of anti-nephrin antibodies Key Exclusion Criteria * Evidence of rapidly progressive glomerulonephritis (loss of ≥50% of eGFR) within 3 months prior to and at Screening) * Active viral or bacterial infections * Existing conditions or clinically significant laboratory abnormalities that may interfere with participation in this study * Administration of live and live-attenuated vaccinations within 30 days prior to enrollment * Known hypersensitivity to atacicept or any component of the formulated atacicept * Additional criteria apply to each cohort/disease.