Atrasentan in Patients With IgA Nephropathy

Inclusion Criteria:

Double-Blind period:

• Biopsy-proven IgA nephropathy.

• Receiving a maximally tolerated dose of RAS inhibitor therapy (ACEi or ARB) that hasbeen stable for at least 12 weeks. Exceptions from this requirement will be made forsubjects who are unable to tolerate RAS inhibitor therapy.

• Total urine protein ≥1 g/day as measured via 24-hour urine collection by centrallaboratory at Screening.

• eGFR of at least 30 mL/min/1.73 m^2 at Screening based on the CKD-EPI equation.

• Willing and able to provide informed consent and comply with all study requirements.

• SGLT2i Stable Stratum Only - Receiving a stable dose of an SGLT2i (per Investigatorchoice) in addition to a maximally tolerated and optimized dose of a RAS inhibitorthat has been stable for at least 12 weeks prior to Screening.

• All fertile men and WOCBP who engage in heterosexual intercourse must be willing toabide with highly effective forms of contraception, as specified in the protocol,throughout the study and for 1 month afterward. In WOCBP, use of contraceptiveagents must have been started at least 1 month prior to Baseline.

Open-Label Period:

• Willing and able to provide informed consent and comply with all OL extension studyvisits and study procedures.

• Completed treatment through Week 132 and completed the Week 136 visit.

• All fertile men and WOCBP who engage in heterosexual intercourse must be willing toabide with highly effective forms of contraception, as specified in the protocol,throughout the study and for 1 month afterward. In WOCBP, use of contraceptiveagents must have been continued after completing the double-blind portion of thestudy.

Exclusion Criteria:

Double-blind period:

• Concurrent diagnosis of another cause of chronic kidney disease including diabetickidney disease or another primary glomerulopathy.

• Clinical diagnosis of nephrotic syndrome.

• BNP value of > 200 pg/mL at Screening.

• Platelet count <80,000 per μL at Screening.

• History of organ transplantation (subjects with history of corneal transplant arenot excluded).

• Use of systemic immunosuppressant medications.

• Hemoglobin below 9 g/dL at Screening or prior history of blood transfusion foranemia within 3 months of Screening.

Open-label period:

• eGFR < 25 mL/min/1.73m^2 or evidence of rapidly decreasing eGFR, includingunrecovered acute kidney injury or expected to require renal replacement therapywithin 3 months

• BNP value of > 200 pg/mL at OL Screening.

• Platelet count < 80,000 per μL at OL Screening.

• Hemoglobin below 9 g/dL at OL screening or prior history of blood transfusion foranemia within 3 months of OL Screening.