A Study to Investigate Safety and Effect of Sparsentan in Combination With SGLT2 Inhibition in Participants With IgAN

• Aged ≥18 years at the time of signing the informed consent.
• Biopsy-proven IgAN. The biopsy may have been performed at any time in the past.
• UA/C ≥0.3 g/g at screening
• An eGFR value of ≥25 mL/min/1.73m\^2 at screening.
• On a stable dose of an SGLT2 inhibitor for at least 12 weeks prior to screening.

• On a stable dose of ACEI and/or ARB therapy for at least 12 weeks prior to screening that is:

  • The participant's maximum tolerated dose (MTD), and
  • at least one half of the maximum labeled dose (MLD)
• Systolic BP must be ≤160 mmHg, and diastolic BP must be ≤110 mmHg at screening.
• For participants receiving chronic low dose systemic corticosteroids (defined as ≤10 mg/day prednisone or equivalent), or an enteric formulation of budesonide and/or a mineralocorticoid receptor antagonist (MRA), the dosage must be stable for ≥12 weeks prior to screening.

Exclusion Criteria:

• IgAN secondary to another condition or immunoglobulin A (IgA) vasculitis.
• Undergone any organ transplant, with the exception of corneal transplants.
• Documented history of heart failure.
• Taking high dose (defined as >10 mg/day prednisone) or other any systemic immunosuppressive medications within 12 weeks of prior to screening.
• Has clinically significant cerebrovascular disease (transient ischemic attack or stroke) and/or coronary artery disease (hospitalization for myocardial infarction unstable angina, new onset of angina with positive functional tests, coronary angiogram revealing stenosis, or a coronary revascularization procedure) within 3 months prior to screening.
• Has jaundice, hepatitis, or known hepatobiliary disease (excluding asymptomatic cholelithiasis), or ALT and/or AST >2 times the ULN range at screening.
• Has a history of malignancy other than adequately treated basal cell or squamous cell skin cancer or cervical carcinoma within the past 2 years.
• Has a history of serious side effect or allergic response to any AngII antagonist, ERA or sparsentan, or has a hypersensitivity to any of the excipients in the study intervention.
• Requires any of the prohibited concomitant medications.
• Treatment with sparsentan within 12 weeks prior to screening
• Has participated in a study of another investigational product within 28 days prior to screening or plans to participate in such a study during the course of this study.
• Has a screening hematocrit value \<27% (0.27 Volume/Volume) or hemoglobin value \<9 g/dL (90 g/L).
• Has a screening potassium value of >5.5 mEq/L (5.5 mmol/L).
• Is pregnant, plans to become pregnant during the course of the study, or is breastfeeding.
• The participant, in the opinion of the Investigator, is unable to adhere to the requirements of the study, including the ability to swallow the study intervention capsules whole.