Teriparatide to be tested for osteogenesis imperfecta
May 19, 2006 - 7:35:37 PM
Jimmy Fox isn't typical of a person with the genetic, "brittle bone" disorder osteogenesis imperfecta (OI). He lifts weights almost daily, participates in grueling wheelchair races, chops wood and enjoys hunting in rough backcountry.
Still, Fox, who owns a busy combination grocery store-gun shop in Cloverdale, Ore., is eager to participate in an Oregon Health & Science University-led study of a drug that may help reduce the debilitating effects of OI, an inherited disorder characterized by weak bones that break easily. People with the most severe forms of OI have short stature, can suffer hundreds if not thousands of fractures in a lifetime, and are confined to a wheelchair.
"I didn't think it could do me any harm," Fox, 40, said of the study. He has a less-severe form of OI, allowing him to be more mobile - he walks on his hands when he's not in his wheelchair - and suffer fewer fractures than many others with the disorder. Fox had both of his legs amputated when he was 18 due to continued fracturing. "The study might do me some good, so I thought I might as well do it and give it a try. It will help other people."
The alternative is unacceptable to Fox, who acknowledges that his significant upper-body strength has kept many of the disorder's most debilitating effects at bay. "They told me 'If you weren't as active as you are, you would be totally screwed up by now.' To be honest, that's what really swayed me to do this."
The study, headed by Eric Orwoll, M.D., professor of medicine (endocrinology, diabetes and clinical nutrition) and director of the Bone and Mineral Unit, OHSU School of Medicine, is examining the effectiveness of the synthesized parathyroid hormone, teriparatide, in increasing bone mass and improving bone structure in adults affected by OI. Teriparatide, derived from the human parathyroid gland, is manufactured and sold by Eli Lilly and Co. under the brand name FORTEO.
FORTEO already is approved for use by men and postmenopausal women with osteoporosis who are at high risk for having fractures, according to Lilly's Web site.
"It gives a lot of hope to a lot of people who wouldn't have much to look forward to," Orwoll said.
In most OI patients, the disorder is caused by a mutation in one of two genes, COL1A1 and COL1A2, that encode for type 1 collagen, the fibrous protein that serves as the scaffolding for bone and which also is present in ligaments, tendons, teeth, the white portion of the eyes, and even skin. The defect impairs the body's ability to mineralize bone and other collagen-containing tissue, leading to bone fragility, loose joints, eye discoloration, dental problems and premature hearing loss.
Although exact incidence isn't known, OI is believed to affect 1 of every 5,000 to 10,000 individuals of all racial and ethnic origins, with between 20,000 and 50,000 Americans living with the disorder. Parents with OI have a 50 percent chance with each pregnancy of having an affected child and most children with the disorder have inherited it from a parent. About a fourth of all children with OI are born into families with no history of the disorder.
Janet Reeder, M.S., PA-C, a former faculty member of the OHSU Bone and Mineral Unit who developed the study, said people with OI are largely ignored by the medical community because few treatment options exist, or doctors fear treatment will cause more fractures.
"Many practitioners say, 'We don't know what to do with you. Sorry, have a nice life,'" Reeder said. "But they pay taxes, they work full time. They have incredible tenacity. This is a group of people that has really triumphed over a lot of disability and deformity. What we're trying to do is help them by hopefully decreasing fractures and thereby increasing quality of life."
There is no cure for the disorder, and while drugs have been studied for use in children with OI, there is no established medical therapy for affected adults. Adult OI treatment varies depending on the degree of impairment and the patient's age. Doctors sometimes surgically implant rods to support long bones or prescribe braces to support lower limbs. Patients also are encouraged to take calcium and vitamin D supplements daily.
"What we're interested in is, after kids make it through childhood and into adulthood, what can we do for them?" Orwoll said.
Each of the three national study sites - OHSU, Kennedy Krieger Institute at Johns Hopkins University, and Baylor School of Medicine - are recruiting a total of 90 men and women ages 18 and older for the 18-month, blinded trial. Participants will receive either FORTEO or a placebo, which is self-administered once a day using an injection pen. They will be examined at the first, third, sixth, 12th and 18th months after initial screening, and their spine, hip, forearm and total body bone mineral density will be measured every six months.
FORTEO offers hope of suffering fewer bone fractures for individuals with OI such as Anton Borissov, a 40-year-old Portland resident who has never walked and lives in his wheelchair. It also will increase awareness about the disorder, which may lead to even more drug therapies.
"For me, it is a big, big thing not to have breaks. When I lift something it's just 'break, break, break,'" said Borissov, a native of Russia who estimates he's suffered a thousand fractures in his lifetime, and who can break ribs just by coughing. He is not a participant in the FORTEO study. "If they're doing this study, it's good. And people will know something about OI, even doctors, and that I'm no different."
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