By Mary Welch
The FDA has cleared Metra Biosystems Inc. to market Alkphase-B, its serum-basedlaboratory test to detect bone formation, for use in monitoring the effectiveness of drugsused in the treatment of osteoporosis.
The Mountain View, Calif., company currently sells Alkphase-B for Paget's disease, thesecond most common metabolic bone disease, following osteoporosis.
"Alkphase-B can show a doctor early on if the treatment drugs are effective or not. It'sanalogous to a cholesterol test. You go in, get a blood test, and see if you're in the normalrange. If you're not, the doctor will try another treatment, therapy or dosage and then testagain." said Karen Shepard, senior marketing manager.
A biochemical marker for bone formation, Alkphase-B measures serum levels of bone-specific alkaline phosphatase (BAP), an enzyme released into the bloodstream as a resultof bone formation. Metra intends for doctors and laboratories to use Alkphase-B to testthe effectiveness of osteoporosis therapies such as estrogen hormonal replacement, andFosamax (alendronate sodium), which is marketed by Merck & Co. Inc., ofWhitehouse Station, N.J.
Bone mass accumulates through a balanced system of removing old bone — orresorption — by osteoclasts, and forming new bone, a process handled byosteoblasts. The system works well until a person reaches about age 35. After that,particularly in women, the bone begins to break down faster than new bone can form.
Estrogen is a hormone that protects against bone degradation, and in post-menopausalwomen, the loss of hormone often results in osteoporosis and osteoporosis-relatedfractures.
Osteoporosis affects some 7 million to 8 million Americans a year (another 17 million havelow bone mass) and usually goes undetected until a sudden injury or fall leads to afracture. One in two women and one in eight men over the age of 50 will suffer a fracturerelated to the disease — that means more than 1.5 million fractures. As a result ofosteoporosis-related hip fractures, 37,500 people will die and 20 percent of those whosurvive will be admitted to a nursing home for long-term care. Direct costs incurred forthe treatment of osteoporosis-related bone fractures in the U.S. in 1995 were $13.8billion.
Metra's 510(k) premarket FDA notification was based on two randomized placebo-controlled clinical trials involving alendronate, one of the first non-hormonal osteoporosistherapies, and estrogen replacement therapy. The first study involved post-menopausalwomen diagnosed with osteoporosis who received alendronate and a calcium supplement,or only a calcium supplement (the placebo group). Alkphase-B was used to comparebone-specific alkaline phosphatase levels.
The second study, also done to compare bone-specific alkaline phosphatase levels,involved healthy post -menopausal women who received estrogen replacement therapy ora calcium supplement (the placebo group).
Both studies confirmed the effectiveness of Alkphase-B in monitoring the effects of thedrugs or hormone supplements.
"We showed in the second trial that within six months the BAP levels returned to thenormal range," said Shepard.
Metra, which reported revenues of $2.5 million for the third quarter of its fiscal year,ending March 31, will launch Alkphase-B for osteoporosis at the end of the month. Thetest should cost between $40 to $60, Shepard said.
Expanded Claims Yield Unique Position
With the expanded claims for Alkphase-B, Metra is now the only diagnostics companywith regulatory clearance for both bone resorption and bone formation assays, Shepardsaid.
The company also markets Pyrilinks-D. It measures deoxypyridinoline (Dpd), a specificmarker of bone resorption which is excreted unmetabolized in urine. A high level of Dpdindicates the body may be removing bone more quickly than it can be replaced, resulting inbone loss.
"With the two tests, a woman can find out how active the degradation process is —or bone loss is — and then, find out if the bone-producing cells are active. Sheshould be able to see if the treatment to stop or slow down osteoporosis is working aboutsix months following the start of treatment," Shepard said.
Metra Biosystems' stock (NASDAQ:MTRA) closed Monday at $2.50, up $0.25.*