Monthly Dosing of Atacicept in IgAN

Inclusion Criteria:

• Must have the ability to understand and sign a written informed consent form, whichmust be obtained prior to initiation of study assessments

• Adult male or female of ≥18 years of age, or as per country specific legally ornationally recognized adult age, who provides written informed consent prior toperforming any study assessments

• Diagnosis of IgAN as demonstrated by renal biopsy conducted within 10 years

• Total urine protein excretion ≥0.75 g per 24-hour or urine protein-to-creatinineratio (UPCR) ≥0.75 mg/mg based on a 24-hour urine sample

• eGFR ≥30 mL/min/1.73 m2 at screening, as per the Chronic Kidney Disease EpidemiologyCollaboration (CKD-EPI)

• On a stable prescribed regimen of RASi (angiotensin converting enzyme inhibitor orangiotensin II receptor blocker) for at least 8 weeks that is at the maximum labeledor tolerated dose at screening and from screening to study Day 1

Exclusion Criteria:

• IgAN secondary to another condition (eg, liver cirrhosis), or other causes ofmesangial IgA deposition including IgA vasculitis (ie, Henoch-Schonlein purpura),systemic lupus erythematosus, dermatitis herpetiformis, ankylosing spondylitis

• Evidence of rapidly progressive glomerulonephritis (loss of ≥50% of eGFR within 3months of screening)

• Evidence of nephrotic syndrome within 6 months of screening (serum albumin <3.0 g/dLin association with UPCR >3.5 mg/mg)

• Renal or other organ transplantation prior to or expected during the study, with theexception of corneal transplants

• Concomitant chronic renal disease in addition to IgAN (eg, diabetic nephropathy,primary focal segmental glomerulosclerosis, membranous nephropathy, C3glomerulopathy, lupus nephritis)