The inclusion criteria are: (1) diagnosis of IgAN by kidney biopsy, (2) age 18 to 65 years, (3) blood pressure of ≤140/90 mmHg, (4) estimated glomerular filtration rate (eGFR) ≥45 ml/min/1.73 m
2 (calculated with the use of the CKD-EPI Creatinine Equation 2009) [
13], (5) 24-h proteinuria range of between 0.5 and 3.0 g, (6) agreement to participate and provision of signed informed consent. Additional file
2 shows the Informed Consent Form in more detail. The exclusion criteria are: (1) secondary IgAN, (2) allergy to AM or losartan potassium, (3) history of AM and ACE-I and/or ARB use within the last 6 months, (4) history of glucocorticoid, immunosuppressant, or
Tripterygium drug use within the previous 1 year, (5) blood pressure of <90/60 mmHg, (6) serum potassium >5.5 mmol/L, (7) serum albumin <30 g/L, (8) unilateral or bilateral renal artery stenosis, (9) pregnant or lactating women, (10) severe heart, brain, liver, or hematopoietic system disease, or other serious illnesses that may affect survival, (11) participation in another clinical investigation. The exit criteria are: (1) endpoint event: proteinuria ≥3.5 g/24 h, doubling of serum creatinine, or receiving blood purification treatment, (2) blood pressure of >160/90 mmHg after antihypertensive drug combination therapy (convinced by measuring blood pressure three times within 2 weeks), (3) blood pressure of <90/60 mmHg after stopping using other antihypertensive agents, (4) serum potassium >5.5 mmol/L after antihyperkalemia drug treatment, (5) serum creatinine rapidly rising to >50% of the baseline within 4 weeks after treatment, (6) serious adverse events (SAEs): hospitalization (initial or prolonged), disability or permanent damage, life-threatening, death, congenital anomaly/birth defect and other serious events (important medical events) [
14], (7) serious breach of protocol: participants failing to take medications according to protocol or taking some drugs that have a significant impact on the primary and secondary outcomes during the 48-week observation period, (8) loss to follow-up or withdrawal from the trial, (9) pregnancy during the trial.