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Natpara (Parathyroid Hormone) Gets Green Light to Control Hypocalcemia in Patients With Hypoparathyroidism

Rare disease affects about 60,000 people in U.S.

The FDA has approved Natpara (parathyroid hormone, NPS Pharmaceuticals) to control hypocalcemia in patients with hypoparathyroidism, a rare disease that affects approximately 60,000 people in the U.S.

Hypoparathyroidism occurs when the body secretes abnormally low levels of parathyroid hormone, which helps regulate calcium and phosphorus levels in the body. The disorder is caused by the loss of function of the parathyroid glands and occurs most often as a result of surgical removal of these glands and more rarely as a result of autoimmune or congenital diseases.

Patients with hypoparathyroidism can experience numbness, tingling, muscle twitching, spasms or cramps, abnormal heart rhythm, and seizures as a consequence of low blood calcium levels. Hypoparathyroidism is also associated with long-term complications, such as kidney damage, kidney stones, cataracts, and the calcification of soft tissues.

Natpara, a hormonal injection administered once daily, helps regulate the body’s calcium levels. The FDA granted Natpara an “orphan drug” designation.

“People with hypoparathyroidism have limited treatment options and face challenging symptoms that can severely impact their quality of life,” said Jean-Marc Guettier, MD, director of the Division of Metabolism and Endocrinology Products in the FDA’s Center for Drug Evaluation and Research. “This product offers an alternative to patients whose calcium levels cannot be controlled on calcium supplementation and active forms of vitamin D.”

The safety and efficacy of Natpara were evaluated in a clinical trial involving 124 subjects who were randomly assigned to active treatment or placebo. The study was designed to determine whether Natpara can be used as a substitute for, or be used to help reduce the amount of, active forms of vitamin D or oral calcium taken by the subjects.

The results showed that 42% of the subjects treated with Natpara achieved normal blood calcium levels on reduced doses of calcium supplements and active forms of vitamin D, compared with 3% of placebo-treated subjects.

The labeling for Natpara includes a boxed warning that osteosarcoma has been observed in animal studies of Natpara. It is unknown whether Natpara causes osteosarcoma in humans, but because of a potential risk of this cancer, the tretament is recommended only for patients whose hypocalcemia cannot be controlled with calcium supplementation and active forms of vitamin D, and for whom the potential benefits of Natpara are considered to outweigh this potential risk. Natpara is available only through a restricted program under a risk evaluation and mitigation strategy.

The most common side effects observed in Natpara-treated subjects included sensations of tingling, tickling, pricking, or paresthesia; low blood calcium levels; headache; high blood calcium levels; and nausea.

Source: FDA; January23, 2015.

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