Effect of AST-120 in Chronic Kidney Disease Treatment: Still a Controversy?

AST-120 (kremezin; Kureha Chemical, Tokyo, Japan) is an oral spherical carbonaceous adsorbent, which was approved for clinical use in Japanese chronic kidney disease (CKD) patients in 1991. It adsorbs indole, the precursor of indoxyl sulfate, in the intestines and prevents indoxyl sulfate production. Indoxyl sulfate, initially identified as a major uremic toxin that causes uremic symptoms, contributes to CKD progression. Since AST-120 decreases serum indoxyl sulfate in a dose-dependent manner, multicenter prospective trials have been conducted in Japan in the 1980s; these trials were mostly in favor of the efficacy of AST-120 in delaying the initiation of dialysis in patients with advanced stage CKD. Many animal studies support the effects of AST-120 on renal outcomes as well as on cardiovascular complications. However, there are yet no reports that unequivocally demonstrate the improvement of hard renal endpoints and/or cardiovascular endpoints. This commentary briefly reviews the major outcomes of the recent clinical trials on AST-120.