Friday, March 2, 2001
The U.S. Food and Drug Administration (FDA) is dragging its feet in approving growth factors that could heal broken bones and aid in spinal fusion, said Thomas A. Einhorn, MD, a Boston University professor of orthopaedic surgery, in a Wednesday press conference.
"Bone morphogenic protein 7 has demonstrated potential, said Dr. Einhorn, a consultant for Stryker Biotech, the drug's manufacturer. "It's been approved for use in patients in Europe and Australia but not the U.S. The FDA is holding things up."
Growth factors might be used, for example, in a patient whose tibia is smashed in an automobile accident. Instead of transplanting bone from the pelvis to replace bone lost in the accident, surgeons could stimulate the tibia to regenerate.
"You'll never hear me say a bad word about the FDA with respect to safety," said Dr. Einhorn. "It's efficacy where I think they need to relax. Everyday I go into work taking care of patients and I don't want to hear them say, 'My tibia is fine but my pelvis still hurts.'"
Dr. Einhorn said the FDA had needlessly challenged the way Stryker Biotech analyzed data on a study initiated in the early 1990s. But Scott D. Boden, MD, an Emory University professor of orthopaedics and consultant for rival drug makers, said he had some reservations about the study because it focused on a type of tibia injury in which conventional treatments are already very effective.
The comments came during a press conference on growth factors and gene therapy in orthopaedics.
Gene therapy is in earlier stages of development, said Dr. Einhorn, but holds even greater potential. In gene therapy, cells are generally altered to make them produce growth factors on their own. Soon, he predicted, orthopaedic surgeons will be able to treat osteoporosis by giving patients bone marrow transplants along with genes that start bone growth and genes that stop bone growth. Doctors will be able to turn on the bone growth genes with one drug, and turn them off with another.
"It sounds like science fiction," said Dr. Einhorn. "But that's the sort of thing we'll see in 10 years."
Gene therapy and growth factors may also be used in preventing disk degeneration, said James D. Kang, MD, a University of Pittsburgh spinal surgery professor. "We can introduce growth factors and genes that produce proteins in hopes of altering the degeneration cascade," he said. "We have done initial animal studies that give us great enthusiasm. We are now able to introduce these factors in rabbits."
The research on growth factors in aiding spinal fusion is even farther along, said Dr. Boden. In a pilot trial, all of the 11 patients given growth factor had successful fusions. Without growth factor, spinal fusion is unsuccessful in 5 to 40 percent of procedures.
The last panelist, Freddie Fu, MD, chairman of orthopaedic surgery at the University of Pittsburgh, said he was researching ways to use gene therapy in sports medicine. "It's hard to convince sports medicine surgeons to think biologically," he said. "I'm one of the few."
But potentially growth factors and gene therapy could have big advantages over conventional treatments, said Dr. Fu. For example, when an anterior cruciate ligament is injured, cartilage, the meniscus and the nerve may also be damaged in a way that conventional surgery can't help but growth factors might.
The new therapies pose ethical problems as well, Dr. Fu said. For example, it now takes months to train for a marathon because microvasculature changes develop so slowly. Growth factors might shorten that time dramatically, and could not be detected in drug tests at the time of the race.
|2001 Academy News March 2 Index A|
Last modified 02/March/2001 by IS