Keryx Biopharma will start 2 studies of Zerenex this year after FDA agrees on study goals

Keryx agrees with FDA on kidney drug trial design

NEW YORK — Keryx Biopharmaceuticals Inc. said Tuesday it agreed with regulators about the design of clinical studies for its drug candidate Zerenex, which is intended to treat a side effect of kidney disease.

Keryx said it will begin two late-stage trials of Zerenex this year. A short study of the drug’s effectiveness will begin by March, and a yearlong trial of its safety and effectiveness will start in the middle of the year. Zerenex is intended to treat high levels of serum phosphorous, or hyperphosphatemia, in the blood of patients with end-stage kidney disease

The company agreed to what is called a special protocol assessment with the Food and Drug Administration, a process in which a drugmaker and the agency confer about the design of clinical trials. Because the FDA has cleared the design of the trial, it is more likely Zerenex will be approved if it reaches its goals in the studies.

In afternoon trading, Keryx stock rose 10 cents, or 4 percent, to $2.61.

The shorter study will include about 150 dialysis patients. After stopping treatment for two weeks, they will be given Zerenex once a day for 28 days. Each patient will take the same dose of 1 milligram to 8 milligrams for the entire study, and after four weeks, their phosphorous levels will be measured.

Serum phosphorus is a chemical that helps people take energy from food. Patients with kidney disease often cannot properly filter the chemical, which causes it to build up in the body, leading to calcification of tissues. Keryx said data from the study should be available by the second half of the year.

The second study will involve 300 patients, and after a two-week break from treatment, they will take Zerenex or an equal dose of an approved drug for 52 weeks. After that portion of the trial is over, the patients who took Zerenex will either keep taking that drug or switch to a placebo. That part of the study will last another four weeks.

Keryx said there are about 485,000 people in the U.S. with end-stage kidney disease. It said the U.S. market for hyperphosphatemia treatment is worth more than $600 million and is growing at about 25 percent per year.