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Amgen parathyroid drug found effective in kidney patient trial

(Adds future trial data detail)

July 17 (Reuters) - An experimental drug proved effective in a late-stage study in reducing excess levels of a hormone associated with a serious condition often seen in patients with chronic kidney disease requiring dialysis, Amgen Inc said on Thursday.

More than 75 percent of patients who received the drug, AMG 416, had a drop in their parathyroid hormone levels of more than 30 percent, compared with 9.6 percent who experienced a similar reduction among those who got a placebo.

Patients with chronic kidney disease who are receiving dialysis often suffer from a progression of secondary hyperparathyroidism (SHPT), a serious condition that develops in response to declining kidney function when the parathyroid glands increase production of the hormone.

The result of the 515-patient, 26-week study was deemed to be statistically significant, Amgen, the world's largest biotechnology company, said.

Amgen obtained AMG 416 through its acquisition of Kai Pharmaceuticals in 2012.

The drug, which is administered intravenously, works by binding to and activating the calcium-sensing receptor on the parathyroid gland.

The study also met its secondary goals, which included the percent change from baseline in serum phosphorus concentration observed between weeks 20 and 27, and corrected calcium concentration. In both cases, AMG 416 achieved statistically significant improvements compared with placebo, Amgen said.

The rate of side effects reported during treatment was high for both groups, occurring in 91.7 percent of the AMG 416 patients and 81.1 percent among the placebo group. The side effects included blood calcium reductions, diarrhea and muscle spasms.

Adverse side effects deemed to be serious were reported in 24.6 percent and 27.4 percent of patients who received AMG 416 and placebo, respectively.

"We are encouraged by the results of this study and look forward to sharing results from a second placebo-controlled study later this year," Amgen research chief Sean Harper said in a statement.

Amgen also said it expects data from a head-to-head trial testing AMG 416 against its own Sensipar in 2015. Sensipar had global sales of $270 million in the first quarter.

(Reporting by Bill Berkrot; Editing by Tom Brown and Leslie Adler)