By Lisa Seachrist

Washington Editor

Currently in a Phase III study as a monotherapy, NPS Pharmaceuticals Inc.'s recombinant parathyroid hormone is being tested by a group of researchers as a combination therapy to treat severe osteoporosis.

The study will test NPS' parathyroid hormone in combination with FDA-approved Fosamax (alendronate sodium), which is marketed by Merck & Co. Inc., of Whitehouse Station, N.J., to see if the combination of the drugs builds bone better than either drug alone. Salt Lake City-based NPS is supplying the parathyroid hormone for the trial, but researchers at the University of California at San Francisco are leading the study, which is being funded by the National Institutes of Health.

"We're not designing the trial; it's being supported by NIH," said David Clark, vice president of operations at NPS. "We do have an agreement to use the data and we may include it in our ultimate submission. Whether or not we do that depends on whether or not the study is completed in time."

The trial is designed to take advantage of the ways the two different agents work. Bone is constantly being formed, destroyed and reformed. Osteoporosis occurs when more bone is destroyed (resorbed) than is being formed. Alendronate slows down the resorption of bone. Parathyroid hormone speeds up the formation and resorption of bone with the net effect being an increase in bone mineral density.

The combination study looks to use the two drugs together to both speed up bone formation and slow bone resorption overall. That study is being lead by Dennis Black, UCSF professor of epidemiology and biostatistics. The trial is a collaborative effort including the universities of Maine, Minnesota and Pittsburgh as well as Columbia University.

"This is a fantastic study for us," Clark said. "This will give us the ability to obtain data on the combination of an anabolic therapy (parathyroid hormone) with an anti-resorptive therapy. Even if we don't end up using the data as part of a registration statement, it will be very important for us to have the information on the combination available for physicians."

Preliminary studies of a shortened parathyroid hormone in combination with estrogen, another anti-resorptive, suggest the two types of agents together can result in greater increases in bone mass than can be realized by either alone. One preliminary study showed the combination increased bone mass by as much as 25 percent over two years.

The combination study will enroll 240 women and last for two years. NPS' single-agent Phase III study, which is already under way, seeks to enroll 2,000 women and treat them for 18 months. Clark said that study is expected to be completed by 2002.

NPS' stock (NASDAQ:NPSP) closed Friday at $12, down 12.5 cents.