Effects of Patiromer on Markers of Mineral Metabolism

New Orleans—The TOURMALINE study examined the use of patiromer to treat patients with hyperkalemia. Patiromer is a non-absorbed potassium-binding polymer that is FDA approved for the treatment of hyperkalemia; it uses calcium as the counter-exchange ion. Results of the 4-week TOURMASLINE study demonstrated that, when given without food, once daily patiromer reduced serum potassium similarly to when given with food.

During a poster session at Kidney Week 2017, David B. Bushinsky, MD, and colleagues reported data from TOURMALINE on markers of mineral metabolism. The poster was titled Effects of the Potassium Binding Polymer Patiromer on Markers of Mineral Metabolism.

The initial dose of patiromer was 8.4 g once daily; the dose was adjusted to achieve and maintain serum K between 3.8 and 5.0 mEq/L. In this prescribed analysis, baseline and week 4 serums and 24-hour urine markers of mineral metabolism normalized for urine-creatinine excretion, to correct for collection errors, are reported for a total cohort of 112 patients.

At baseline, serum calcium was 9.31 mg/dl and serum phosphate was 4.10 mg/dL; there was no change in those levels at week 4 (9.34 and 3.99 mg/dL, respectively). At baseline, sixteen patients had elevated serum potassium (>4.8 mg/dL). Of those patients, treatment with patiromer decreased serum potassium from 5.32 to 4.68 mg/dL at week 4 (P<.02). In the total cohort, patiromer decreased creatinine-normalized urine phosphate from 628.2 mg/24 hours at baseline to 573.6 mg/24 hours at week 4 (P<.01).

At baseline, creatinine-normalized urine calcium was 50.8 mg/24 hours; there was no change at week 4. Levels of serum 1,25(OH)2D decreased from 37.3 at baseline to 34.1 pg/mL at week 4 (P<.05). Parathyroid hormone (PTH) decreased from 85.1 pg/mL at baseline to 65.2 pg/mL at week 4 (P<.0001). Mean levels of fibroblast growth factor 23 and 25(OH)D did not change.

In conclusion, the researchers said, “In addition to lowering serum potassium, patiromer decreased mean urine phosphate excretion in the overall population and mean serum phosphate in patients with hyperphosphatemia, while not changing mean urine calcium or mean serum calcium. PTH and 1,25(OH) 2D both decreased. These findings suggest that when patiromer exchanges intestinal potassium for calcium, some of the released calcium binds to intestinal phosphate lowering urine phosphate and serum phosphate in hyperphosphatemic patients and some of the calcium is absorbed, lowering PTH and 1,25(OH) 2D without changing serum calcium.”

Source: Bushinsky D, Spiegel DM, Yuan J, Warren S, Pergola PE. Effects of the potassium binding polymer patiromer on markers of mineral metabolism. Abstract of a poster presented at the American Society of Nephrology 2017 Kidney Week, November 3, 2017, New Orleans, Louisiana. Funding was provided by Relypsa, Inc., a Vifor Pharma Company.