FGF23 Reduction : Efficacy of a New Phosphate Binder in CHronic Kidney Disease

Inclusion Criteria: * Patients who gave their written consent * Women or men over 18 years * No concomitant treatment with phosphate binders * CKD patients not on dialysis stage 3b or 4, as a GFR (glomerular filtration rate) between 15 and 45 ml/min/1.73m2, using simplified MDRD formula * At the inclusion visit,patients with blood results as levels of C-terminal FGF-23 \> 120 rU/ml and fasting phosphatemia \> 1.0 mmol/l * Able to comply with the study procedures during all the study period * Willing to abstain from taking any following medication during all the study period :antiacid and phosphate binders with aluminium, magnesium, calcium or lanthanum;Treatment for hyperparathyroid : active vitamin D and calcimimetic ; native vitamin D * Female subjects who are of childbearing potential must have a reliable contraceptive methods during all the study period (hormonal, barrier methods or intrauterine device) * No Participation in any clinical trial using an investigational product or device during the 30 days preceding the first protocol visit * Informed patient who agreed with the utilisation of his data for the study * Able to read and understand french and study objectives * Inscription to medical assurance Exclusion Criteria: * predisposition with or presence of intestinal or ileus obstruction or severe gastrointestinal motility disorder(like severe constipation) * Antecedent of major gastrointestinal surgery * Abusive consumption of alcohol and drug (exclude tabacco) a…