Supplementary Material for: Effects of Phosphate Binder Therapy on Vascular Stiffness in Early-Stage Chronic Kidney Disease

<b><i>Background/Aims:</i></b> Cardiovascular disease (CVD) is increased in chronic kidney disease (CKD), and contributed to by the CKD-mineral bone disorder (CKD-MBD). CKD-MBD begins in early CKD and its vascular manifestations begin with vascular stiffness proceeding to increased carotid artery intima-media thickness (cIMT) and vascular calcification (VC). Phosphorus is associated with this progression and is considered a CVD risk factor in CKD. We hypothesized that modifying phosphorus balance with lanthanum carbonate (LaCO<sub>3</sub>) in early CKD would not produce hypophosphatemia and may affect vascular manifestations of CKD-MBD. <b><i>Methods:</i></b> We randomized 38 subjects with normophosphatemic stage 3 CKD to a fixed dose of LaCO<sub>3</sub> or matching placebo without adjusting dietary phosphorus in a 12-month randomized, double-blind, pilot and feasibility study. The primary outcome was the change in serum phosphorus. Secondary outcomes were changes in measures of phosphate homeostasis and vascular stiffness assessed by carotid-femoral pulse wave velocity (PWV), cIMT and VC over 12 months. <b><i>Results:</i></b> There were no statistically significant differences between LaCO<sub>3</sub> and placebo with respect to the change in serum phosphorus, urinary phosphorus, tubular reabsorption of phosphorus, PWV, cIMT, or VC. Biomarkers of the early CKD-MBD such as plasma fibroblast growth factor-23, Dickkopf-related protein 1 (DKK1), and sclerostin were increased 2- to 3-fold at baseline, but were not affected by LaCO<sub>3</sub>. <b><i>Conclusion</i></b>: Twelve months of LaCO<sub>3</sub> had no effect on serum phosphorus and did not alter phosphate homeostasis, PWV, cIMT, VC, or biomarkers of CKD-MBD.