AMGEN TESTING BONE DRUG.

Byline: Ben Sullivan Daily News Staff Writer

Biotechnology drug maker Amgen announced Wednesday that a drug designed to fight osteoporosis, a condition common in the elderly in which bones easily break, is being tested on humans.

The drug, osteoprotegrin or OPG, a genetically engineered version of a naturally occurring human protein, appears to regulate bone mass, according to Amgen.

In the initial trial phase, Amgen researchers will evaluate whether OPG is safe for use by healthy, post-menopausal women. Four times as many women as men develop osteoporosis.

If that test is successful, later trial phases will study whether OPG plays a role in maintaining bone mass and whether that in turn leads to fewer osteoporosis-related ailments, like broken bones.

Analysts project the potential market for a successful osteoporosis drug could reach as high as $1 billion a year in the United States, though they caution that profits for Thousand Oaks-based Amgen - the world's largest biotech concern - from OPG remain years away.

``Osteoporosis is a big, big market,'' said analyst Catherine Copithorne at Prudential Securities. But because osteoporosis is a condition that develops over a number of years, ``the drawback is that the clinical trial schedules tend to be very long,'' she said.

Copithorne said it could be up to five years before Amgen completes all the trials needed for U.S. Food and Drug Administration approval of OPG.

Amgen shares closed down $1.3125 Wednesday at $68.4375.