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

Inclusion Criteria: * 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.