Credit: Reuters/Jason Reed
A view shows the U.S. Food and Drug Administration (FDA) headquarters in Silver Spring, Maryland August 14, 2012.
NPS shares gained 15 percent in pre-market trading to $29.40 from a close of $25.77, returning to levels it was trading at on Sept. 4 before investors grew concerned that the FDA documents would contain negative information about the treatment.
The report, posted on Wednesday on the FDA's website, comes two days ahead of a meeting of outside advisers to the agency who will discuss the drug and recommend whether it should be approved. The FDA reviewers said serious adverse events were similar between the treatment group and the placebo group.
Natpara is designed to treat hypoparathyroidism, a condition in which the body's parathyroid gland does not secrete enough parathyroid hormone (PTH). The hormone works with vitamin D to regulate body calcium.
Low levels of PTH can cause tingling in the fingers and toes, muscle spasms, fatigue, muscle aches, hair loss, dry skin, headaches, mood swings and memory problems.
The condition can be caused by congenital disorders or surgery and is currently treated with high doses of calcium and vitamin D. Natpara is a bioengineered version of the hormone.
About 180,000 people globally suffer from hypoparathyroidism, according to NPS. In about 40 percent of cases, the condition cannot be controlled with calcium and vitamin D.
That uncontrolled population is the audience NPS initially plans to target. In the United States that translates into about 20,000 patients, the company said.
Data from a late-stage clinical trial showed that 53 percent of patients treated with Natpara were able to reduce their calcium and vitamin D supplements by 50 percent or more, compared with 2 percent of placebo-treated patients.
By week 24, 43 percent of patients treated with Natpara were able to stop vitamin D therapy and required 500 mg a day or less of calcium, compared with only five percent of patients treated with placebo.
(Reporting by Toni Clarke; Editing by Susan Heavey and Chizu Nomiyama)
