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.

Diagnosis of IgAN, IgAVN, pMN, MCD, FSGS, or primary nephrotic syndrome

For patients enrolling in IgAN cohorts (eligibility varies by cohort):

* Age ≥ 18 years
* Biopsy proven IgAN, IgAVN, or recurrent IgAN in kidney transplant
* UPCR ≥ 0.5 g/g or UPE ≥ 0.5 g/day on 24h urine
* eGFR≥ 20 mL/min/1.73m2

For patients enrolling in pediatric IgAN Cohorts (eligibility varies by cohort):

* Age ≥ 2 years and \< 18 years
* Biopsy proven IgAN or IgAVN
* On stable prescribed regimen of RAASi (or SoC) for at least 8 weeks
* UPCR ≥ 1.0 g/g or UPE ≥ 1.0 g/d on 24h urine
* eGFR≥ 30 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 or UPE ≥ 1.5 g/d on 24h urine
* 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
* Adults with biopsy diagnosis of primary MCD or FSGS (adults) or children with challenging clinical course with steroids (frequenlty relapsing, steroid-dependent, or steroid-resistant)
* UPCR ≥ 1.0 g/g or UPE ≥ 1.0 g/d on 24h urine
* Evidence of anti-nephrin antibodies

Key Exclusion Criteria:

* Evidence of rapidly progressive glomerulonephritis (loss of ≥50% of eGFR) within 12 weeks 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
* Immunosuppressant medications within 4 weeks prior to dosing with atacicept (except transplant maintenance immunosuppression).
* Known hypersensitivity to atacicept or any component of the formulated atacicept
* Additional criteria apply to each cohort/disease.