NPS Pharmaceuticals Inc. received an approvable letter for Preos, its parathyroid hormone to reduce fracture risk, but the company’s shares fell 37.5 percent amid safety concerns raised by the FDA.

In its letter, the agency referred to pivotal data that demonstrated significant fracture reductions in postmenopausal women with osteoporosis, but also showed a higher incidence of hypercalcemia in patients receiving Preos (parathyroid hormone [rDNA origin] for injection) compared to placebo.

The FDA asked for additional information regarding these data, as well as the use of the injection device for administering the drug.

At this time, "we don’t yet know fully what the extent of those questions are," said Tony Coles, president and CEO of the Salt Lake City-based company. "The agency has just provided us a sense about these two particular issues, and we have already requested a meeting with the FDA to find out more about their concerns and to figure out the best path forward."

Among the issues will be whether the company’s existing Preos data will be sufficient, or whether additional studies will have to be conducted. Following that meeting, NPS expects to provide an updated projection on the potential approval of the drug.

"We’re really going to try to get to the bottom of the FDA’s concerns and questions, and report on that basis," Coles told BioWorld Today.

Shares of NPS (NASDAQ:NPSP) lost $5.27 Friday, to close at $8.77.

The pivotal Phase III study involved about 2,600 patients randomized to receive a daily subcutaneous injection of 100 micrograms of Preos or placebo, in addition to daily calcium and vitamin D supplements.

Results from the 18-month study showed that Preos demonstrated a relative fracture risk reduction of 66 percent.

However, a total of 21 percent of Preos-treated patients experienced a measurement of baseline serum calcium at greater than 10.7 mg/dL, compared to 3 percent of placebo patients, and 0.7 percent of patients in the Preos group discontinued treatment due to the increased serum calcium. (See BioWorld Today, Oct. 25, 2004.)

NPS has received better news regarding its marketing authorization application for Preos in Europe, where it would be sold as Preotact to treat osteoporosis in premenopausal women.

Last month, the Committee for Medicinal Products for Human Use recommended approval of the drug, and the European regulatory agency is expected to make its decision next quarter.

Upon approval in Europe, the drug would be launched by NPS’ partner, Nycomed Group, of Roskilde, Denmark, during the second half of 2006.

Preos is expected to compete with Indianapolis-based Eli Lilly & Co.’s Forteo (teriparatide), which posted total sales of $118 million for the fourth quarter of 2005.