Atacicept in Subjects With IgA Nephropathy

Key Inclusion Criteria:

   - Must have the ability to understand and sign a written informed consent form

   - Male or female of ≥18 years of age

   - Total urine protein excretion ≥1.0 g per 24-hour or urine protein to creatinine ratio
   (UPCR) ≥1.0 mg/mg based on a 24-hour urine sample during the Screening Period

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

   - eGFR ≥ 30 mL/min/1.73 m2, as per the Chronic Kidney Disease Epidemiology Collaboration
   (CKD-EPI) equation.

   - On a stable prescribed regimen of RAASi for at least 12 weeks that is at the maximum
   labeled or tolerated dose at Screening

   - Systolic blood pressure ≤150 mmHg and diastolic blood pressure ≤90 mmHg

Key Exclusion Criteria:

   - IgAN secondary to another condition (e.g., liver cirrhosis), or other causes of
   mesangial IgA deposition including IgA vasculitis (i.e., Henoch-Schonlein purpura),
   systemic lupus erythematosus (SLE), dermatitis herpetiformis, ankylosing spondylitis

   - Total urine protein excretion ≥ 5g per 24-hour or urine protein to creatinine ratio
   (UPCR) ≥ 5 mg/mg based on a 24-hour urine sample during the Screening Period

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

   - Evidence of nephrotic syndrome within 6 months of screening (serum albumin <30g/L in
   association with UPCR >3.5 mg/mg

   - Renal or other organ transplantation prior to, or expected during the study

   - Concomitant chronic renal disease in addition to IgAN

   - Uncontrolled diabetes, defined as hemoglobin-A1c (HbA1c) >7.5% at screening

   - History of tuberculosis (TB), untreated latent TB infection (LTBI), or evidence of
   active TB determined by a positive Quantiferon test

   - Participation in the Phase 2b (Parts A and B) study or any previous treatment with
   atacicept