Novel Iron-Based Phosphate Binder Effective, Well Tolerated

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DENVER—An experimental iron-based phosphate binder is effective for treating hyperphosphatemia in hemodialysis (HD) patients, and is well tolerated, new data show.

James A. Tumlin, MD, and colleagues compared the new binder, called PA21, with sevelamer hydrochloride in a study of 154 HD patients on a phosphorus-restricted diet and who underwent HD three times a week. The patients had phosphorus levels of 5.5 mg/dL or higher. The investigators randomized subjects equally to five PA21 treatment arms (1.25, 5.0, 7.5, 10.0, or 12.5 g/day) or to a control arm of sevelamer at a dosage of 4.8 g/day for six weeks of treatment.

All PA21 treatment arms except for the 1.25 g/day group showed a significant decrease in phosphorus from baseline to the end of treatment, the researchers reported. The mean decrease was 1.3, 1.3, 1.6, and 1.8 mg/dL for 5.0, 7.5, 10.0, and 12.5 g/day groups, respectively. Patients who received sevelamer had a decrease of 1.3 mg/dL.

The median time to the first controlled phosphorus level (3.5-5.5 mg/dL) was one week in the four higher PA21 groups and two weeks in the sevelamer group. During treatment, the percentage of subjects with controlled phosphorus levels ranged from 68% to 91% in the PA21 5.0 to 12.5 g/day groups; it was 83% in the sevelamer arm.

Apart from hypophosphatemia, the researchers noted, adverse events reported with PA21 were not dose dependent. They were mainly related to the gastrointestinal (GI) tract and occurred with a frequency similar to that of the sevelamer group. No patients treated with PA21 and two patients treated with sevelamer discontinued treatment because of GI events.

“While larger studies need to be done, it appears that PA21 provides better phosphate control per unit dose,” said Dr. Tumlin, Associate Professor Medicine at the University of Tennessee College of Medicine at Chattanooga and the Director of the Southeast Renal Research Institute in Chattanooga. “This has the clear advantage for patients already burdened with heavy pill counts. As in the case with tight blood pressure control, recent studies also indicate that multiple binders working via different mechanisms will be ultimately needed to achieve maximum phosphate control. Thus the addition of a new binder working through different pathways may facilitate phosphate management.”

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