Rationale and protocol of the Study Of diabetic Nephropathy with AtRasentan (SONAR) trial: A clinical trial design novel to diabetic nephropathy

Aims Individuals with diabetes and chronic kidney disease (CKD) are at high risk for renal events. Recent trials of novel treatments have been negative, possibly because of variability in response to treatment of the target risk factor. Atrasentan is a selective endothelin A receptor antagonist that reduces urinary albumin‐to‐creatinine ratio (UACR), with a large variability between patients. We are assessing its effect on renal outcomes in the Study Of diabetic Nephropathy with AtRasentan (SONAR; NCT01858532) with an enrichment design (>30% lowering of albuminuria) to select patients most likely to benefit. Materials and Methods SONAR is a randomized, double‐blind, placebo‐controlled trial with approximately 3500 participants who have stage 2–4 CKD and macroalbuminuria and are receiving a maximum tolerated dose of a renin‐angiotensin system inhibitor. Results After 6 weeks of exposure to atrasentan 0.75 mg once daily (enrichment period), participants with ≥30% UACR decrease and no tolerability issues (responders) were randomly assigned to placebo or atrasentan 0.75 mg/day. The responder group will be used for primary efficacy and safety analyses. Approximately 1000 participants with