2. Male or female ≥18 years with biopsy-confirmed IgAN; eGFR ≥30 mL/min/1.73 m² for main cohort; \>40 mL/min/1.73 m² for optional biopsy cohort.
3. Screening UPCR ≥0.5 g/g measured by first morning void.
4. Maximally tolerated or locally approved maximal ACEi/ARB dose before enrollment; diuretics, other antihypertensives and SGLT2i, if used, stabilized for at least 90 days before baseline.
5. WOCBP and sexually active participants must comply with protocol contraception requirements.
You may not be if
1. Hypersensitivity to study treatment/excipients or similar drug classes.
2. CKD primarily attributable to non-IgAN etiology.
3. Suspected RPGN or IgA vasculitis.
4. Nephrotic syndrome.
5. BNP \>200 pg/mL or NT-proBNP \>450 pg/mL at screening.
6. Platelets \<80,000/µL.
7. Organ transplant history other than corneal transplant.
8. Systemic immunosuppressants \>2 weeks in prior 3 months or rituximab within 6 months.
9. Confirmed BP \>150/95 mmHg based on mean of 3 screening measurements.
10. Heart failure/fluid overload.
11. Significant liver disease or transaminases/bilirubin \>2× ULN.
12. Hemoglobin \<9 g/dL or transfusion for anemia within 3 months.
13. Malignancy unless protocol-defined exception.
14. Pregnancy/breastfeeding or intent to become pregnant.
15. Male intent to father a child/donate sperm during study and 1 month after.
16. Recent investigational/approved IgAN treatment per protocol washout.
17. Clinically significant unstable/uncontrolled medical disorder that may confound results or add risk.
18. Alcohol/illicit drug-related disorder within 3 years.
19. WOCBP not using highly effective contraception; sexually active males unwilling to use condoms.
20. Prohibited therapies.
21. MRI contraindications.
22. Optional biopsy cohort exclusion if biopsy risk is unacceptably high.
Clareo Health | Mechanistic Evaluation of Atrasentan in Patients With IgA Nephropathy (IgAN)
