RnaGel(R), a novel calcium- and aluminium-free phosphate binder, inhibits phosphate absorption in normal volunteers

Background: Available phosphate binders contain aluminium or calcium which can be associated with undesirable effects. RenaGel®, cross-linked poly(allyl-amine hydrochloride) is a non-absorbed phosphate binding polymer, free of calcium and aluminium. We conducted this study to examine the safety and phosphate binding efficacy of RenaGel in volunteers. Method: During 18 days (days 0-17) at the clinical study unit, 24 subjects consumed a phosphate-controlled diet designed to provide 37.5 mmol (1200 mg) elemental phosphorus per day. From the morning of day 5 to the morning of day 9, urine and faeces were collected. Average base line urine and faecal phosphorus contents were determined. On days 9-16, the subjects received either RenaGel 1 g, 2.5 g, or 5 g or placebo three times per day immediately prior to the meals. From the morning of day 13 to the morning of day 17, urine and faeces were again collected and phosphorus contents on treatment were determined. Results: RenaGel inhibited dietary phosphate absorption as measured by a decline in average daily urinary phosphorus excretion and an increase in average daily fecal phosphorus excretion. Average urine phosphorus contents on treatment were 2.7.2 mmol (870 mg) per day in the placebo group vs 23.8 mmol (762 mg), 19.5 mmol (625 mg), and 16.6 mmol (530 mg) per day in the renaGel 1-g, 2.5-g, and 5-g groups. Average daily faecal phosphorus content on treatment was markedly higher in the RenaGel 5-g group, 19.1 mmol (611 mg) per day vs 10.7 mmol (342 mg) per day for the placebo group. RenaGel also decreased total serum cholesterol by 0.71 mmol/L (27.5 mg/dl), 0.55mmol/l (21.3 mg/dl), and 1.08 mmol/l (41.8 mg/dl for the RenaGel 1-g,and 5-g groups. RenaGel was well tolerated with adverse events similar to placebo. Conclusion: RenaGel is a safe, effective, and well tolerated phosphate binder in normal volunteers. The degree of phosphate binding is consistent with its potential use as a phosphate binder in renal failure patients.