FDA Approves Hormone Treatment for Hypoparathyroidism

The FDA has approved NPS Pharmaceuticals’ parathyroid hormone (Natpara), a once-daily hormonal injection to control low blood calcium levels (hypocalcemia) in patients with hypoparathyroidism.

Hypoparathyroidism is a disease in which the parathyroid glands produce an insufficient amount of parathyroid hormone, which helps to regulate calcium and phosphorus levels in the body. Patients with hypoparathyroidism can experience numbness, tingling, muscle twitching, spasms or cramps, abnormal heart rhythm, and seizures as a result of their low blood calcium levels, and can develop long-term complications such as kidney damage, kidney stones, development of cataracts and calcification of soft tissues.

According to the FDA, the disorder affects approximately 60,000 patients in the United States.

The FDA’s nod was based on the results of a placebo-controlled clinical trial in which Natpara’s safety and effectiveness were evaluated in 124 patients, with the research team seeking to determine whether the then-investigational drug could be used to reduce the amount of calcium supplements or active forms of vitamin D or taken by patients, or replace them entirely. The researchers found that, when given reduced doses of calcium supplements and active forms of vitamin D, 42% of patients treated with Natpara achieved normal blood calcium levels, compared with 3% of placebo-treated patients.

“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, in a press release. “This product offers an alternative to patients whose calcium levels cannot be controlled on calcium supplementation and active forms of vitamin D.”

Natpara carries a boxed warning that bone cancer (osteosarcoma) has been observed in rats. The most common adverse events observed in trial patients treated with Natpara were sensations of tingling, tickling, pricking, or burning of the skin, low blood calcium, headache, high blood calcium, and nausea.

Due to a potential risk of bone cancer (osteosarcoma) observed in rat studies, Natpara is only recommended for use in patients whose hypocalcemia cannot be controlled on calcium supplementation and active forms of vitamin D, and for whom the potential benefits are considered to outweigh this potential risk.