Keryx Biopharmaceuticals Inc on Tuesday said its drug to treat iron deficiency anemia in chronic kidney disease patients not yet requiring dialysis met the goals of a late stage clinical trial, potentially paving the way for an expanded approval of the treatment.

In the 16-week study of 234 patients with moderate to severe kidney disease, 52 percent of those who received Keryx's ferric citrate saw their hemoglobin levels rise by at least 1 gram per deciliter (g/dl) of blood during the trial. That compared with 19 percent in the placebo group who experienced a 1g/dl increase.

The initial results for the oral, iron-based drug were both statistically significant and clinically meaningful, the company said.

Based on the study of patients who had not adequately responded to or were unable to tolerate current oral iron therapies, Keryx said it would apply in the third quarter for an expanded approval with U.S. regulators for ferric citrate in moderate to advanced chronic kidney patients not dependent on dialysis.

The drug was previously approved under the brand name Auryxia to lower the amount of phosphate in the blood of chronic kidney disease patients on dialysis.

An estimated 1.6 million people in the United States suffer from stage 3 to stage 5 non-dialysis dependent chronic kidney disease and iron deficiency anemia, Keryx said.

Side effects were primarily mild to moderate and included diarrhea, constipation and nausea. Twelve of 31 ferric citrate patients who discontinued treatment did so because of side effects, the company reported.

Two patients in the drug group died during the study, but researchers deemed those deaths to be unrelated to the treatment.

The drug also met secondary goals of the trial compared with placebo, including mean change in hemoglobin and proportion of patients with a durable response, Keryx reported.

"We believe that the ability to treat iron deficiency anemia, managing hemoglobin and iron levels, could have an important effect on the way kidney specialists treat these patients," Keryx Chief Medical Officer John Neylan said in a statement.

(Reporting by Bill Berkrot, editing by G Crosse)