Binding and inhibitory activities: A novel oral therapeutic agent for the treatment of hyperphosphataemia rats.

Novel oral therapeutic agents based on inhibition or binding activity without adverse events in CKD patients are urgently needed. Here, 5/6 nephrectomy (NX) rats were used to construct a CKD model. Aminated cellulose (AC711), which is metal-free, non-absorbable, and low-volume expansive, was used as a novel oral therapeutic agent for hyperphosphataemia treatment in rats. The efficacy of AC711 on serum and urinary phosphate levels, the expression of type II sodium-dependent phosphate cotransporter (NPT2b), and type III Na-dependent phosphate cotransporter (PiT-1/2) was examined. Serum fibroblast growth factor-23 (FGF-23) levels, parathyroid hormone (PTH) levels, and the phenotypic transformation of vascular smooth muscle cell markers (smooth muscle 22 (SM22) and Runx2) are considered an adaptive response to elevated serum phosphate levels. A similar efficacy of AC711 was observed on serum and urinary phosphate levels when the same dose of AC711 and sevelamer was administered to 5/6 NX rats. The decreasing expression of NPT2b, PiT-1, and PiT-2 was examined in the AC711 groups in a dose-dependent manner. The sevelamer and AC711-MD groups for FGF-23 and PTH indicated no significant difference. The down-regulation of Runx2 expression and up-regulation of SM22 expression were seen in the AC711 groups in a dose-dependent manner. Two suppression mechanisms (binding and inhibiting activities) were observed in the gastrointestinal (GI) tract in the AC711 groups. A novel oral phosphate binder, AC711, showed both binding and inhibition characteristics. The low-volume expansion of AC711 following exposure to simulated intestinal fluid provides the potential therapeutic benefits with the advantage of moderate GI side effects.