1. Diagnosed IgAN with biopsy verification
2. Female or male participants greater than or equal to 18 years of age
3. Completion of 9 months of treatment with TARPEYO 16 mg QD at the Baseline visit
4. Access to retrospective local laboratory assessment data on UPCR and serum creatinine.

Available retrospective data should include at least 1 assessment timepoint within 3 months prior to the first dose of TARPEYO® commercial treatment

1. Proteinuria at Screening based on 2 consecutive measurements (24-hour urine collection) after informed consent, separated by at least 1 week and calculated by the central laboratory.

Both samples of the same parameter must show either of the following:

• Proteinuria greater than or equal to 0.5 g per day (greater than or equal to 500 mg per day) in 2 consecutive measurements, or
• UPCR greater than or equal to 0.3 g/gram in 2 consecutive measurements

1. On stable treatment with renin-angiotensin system (RAS) inhibitor therapy for at least 8 weeks prior to the Baseline visit. A stable dose is defined as a dose within 25% of the dose at Baseline
2. If on current treatment with sodium-glucose cotransporter-2 (SGLT2) inhibitor, the treatment should have been stable for at least 8 weeks prior to the Baseline visit. A stable dose is defined as a dose within 25% of the dose at Baseline

1. Participants who have been treated with systemic immunosuppressive medications including glucocorticosteroids (GCS) other than TARPEYO during the TARPEYO commercial treatment period. Topical or inhalation products containing GCS or immunosuppressants are allowed
2. Presence of other glomerulopathies (e.g., C3 glomerulopathy and/or diabetes nephropathy)
3. Presence of nephrotic syndrome (i.e., proteinuria greater than 3.5 g per day and serum albumin less than 3.0 g/dL, with or without edema)
4. Presence of medical condition excluding continued TARPEYO treatment, as assessed by the Investigator
5. On current or planned dialysis.
6. Undergone kidney transplant.
7. Poorly controlled diabetes mellitus or hypertension, as assessed by the Investigator.
8. Participants with known osteoporosis in the medium- or high-risk category according to the 2010 American College of Rheumatology recommendations.
9. Any medical or social circumstance making trial participation and/or TARPEYO treatment unsuitable, as assessed by the Investigator.
10. Participants with clinically significant infections that put the participant at risk, at the discretion of the Investigator.
11. Participants unwilling or unable to meet the requirements of the protocol.
12. Intake of another investigational drug during trial, or during the preceding 9-month commercial TARPEYO treatment period.
13. Females who are pregnant, breastfeeding, or plan to become pregnant in the trial period.
14. Participants taking potent inhibitors of cytochrome P450 (CYP) 3A4