NEW YORK (AP) — Shares of Keryx Biopharmaceuticals Inc. jumped Monday after the company reported positive midstage safety results for its kidney disease drug. The stock rose 34 cents, or 31.6 percent, to $1.42 in morning trading. Shares earlier reached $1.58, their highest point in the past 52 weeks. The company is developing Zerenex as a treatment of elevated serum phosphorous levels, or hyperphosphatemia, in patients with end-stage kidney disease. Those patients are on hemodialysis, which is used to remove waste products from the blood. The drug candidate met its key safety goals in the study. Meanwhile, the midstage study results suggested that the drug is effective in regulating serum phosphorous levels, though the study is not designed to test for effectiveness. Keryx is now in the process of developing a late-stage development program for the drug and is consulting with the FDA. The regulatory agency has already said the current studies are adequate to support late-stage clinical trials.