Gene Therapy for Hemophilia Passes Test
Altered cells may correct genetic flaw
WEDNESDAY, June 6, 2001 (HealthDayNews) -- A new kind of gene therapy for hemophilia that uses altered cells from the patients themselves to correct a genetic flaw has passed its first preliminary test in humans, researchers report.
If the technique works, it may apply to other diseases such as diabetes, says Dr. Richard F. Selden, president of Transkaryotic Therapies, the company that developed the biotechnology. He is an author of a report on the results in the New England Journal of Medicine.
The technique is aimed at diseases caused by insufficient amounts or flawed versions of essential proteins. In diabetes, the protein is insulin. In hemophilia, it is factor VIII, a protein responsible for blood clotting. One of every 5,000 babies born in the United States has a flawed gene for factor VIII, and about 15,000 Americans, almost all males, have hemophilia.
About 60 percent of people with the flawed gene have less than 1 percent of normal factor VIII activity. They are vulnerable to episodes of uncontrolled bleeding that can damage joints and soft tissue. Current treatment requires frequent injections of factor VIII. Several gene therapy studies are underway, generally using an altered virus to carry the normal gene into the body.
However, scientists worry that using a virus to carry the gene could cause problems, such as an inflammatory immune response. The Transkaryotic technique puts plasmids, DNA units that carry the factor VIII gene, into skin cells taken from the patient. The altered cells are grown in the lab and then injected back into the same patient.
The injected cells caused no problems in the first six patients to undergo the treatment. While the 12-month study was designed only to determine whether the treatment is safe, four of the six patients had increased blood levels of factor VIII, the researchers report. The favorable changes lasted for 10 months in one patient.
The results are very preliminary, says study leader Dr. David A. Roth, director of hemophilia clinical research at Beth Israel Deaconess Medical Center in Boston.
"We need to evaluate the patients for two years to complete this study," Roth says. "We need to analyze the data and formulate a plan for moving forward to another study."
The plan is open to change, Roth says. "What we are doing now may not be done this way in the future. We may be using different plasmids at higher levels or different numbers of cells."
But "the fact that we have not seen any abnormalities or any immune reaction is a wonderful observation," Roth says.
And while the altered cells must be injected into the abdominal area, which clearly is inconvenient, "these patients are having injections continually into their veins throughout life," he says.
Selden says the current work is based on an idea he had when he was a student taking courses at Harvard Medical School on retroviruses, the kind of viruses used in most gene therapy studies.
"What was clear was that they can cause cancer in animals, but not in humans," he says. "That appeared to present a substantial safety problem, but when I published papers talking about the safety of viral systems, people thought it was not a reasonable idea."
Selden, who founded Transkaryotic Therapies in 1988, says it is the only biotechnology company using altered cells taken from patients. His longer-term goal is to produce gene therapies for major diseases such as diabetes.
"Now we are focusing on hemophilia, but if we could demonstrate efficacy in hemophilia, we could expand into other disorders, such as diabetes, osteoporosis and some forms of cancer," Selden says.
What To Do
Nothing. The research is in its earliest stages and may still run aground.
Or, read these previous HealthDay stories on gene therapy.