Gene Therapy: One Family's Story
For Dave and Lynn Frohnmayer of Eugene, Ore., and their children Mark, 24, Jonathan, 14, and Amy, 12, the joys of family life mingle with anger, denial, and grief. Missing from their portrait are two daughters, Kirsten and Katie, claimed by a rare and poorly understood genetic disease called Fanconi anemia. Kirsten, who responded to a controversial experimental treatment with a male hormone, lived to be 24. Katie, with more serious complications, died at 12.
The shadow of illness has still not left the Frohnmayers. Their third daughter, Amy, who just finished sixth grade, has long, blond, gently curling hair, blue eyes, and a fondness just now for green nail polish--and is also afflicted. This time, however, the family is hoping they will not, once again, be compelled to watch helplessly as a daughter dies.
Researchers around the world are beginning the first human trials of promising new methods of gene therapy--curing disease at the most fundamental level by correcting the genetic errors responsible for it. The newest gene-therapy techniques represent a substantial advance over methods that were only partly successful a decade ago. These new efforts, and the further advances sure to follow, could ultimately transform the treatment of heart disease, cancer, and scores of other ailments--including inherited disorders such as Fanconi anemia.
Whether the new techniques will be perfected in time to save Amy is uncertain. But the Frohnmayers had no hope at all with their first two daughters. Fanconi anemia was a mystery to geneticists, who could describe the symptoms but had no idea what caused them. Dave, then Oregon's attorney general and now president of the University of Oregon, and Lynn, a social worker, launched an effort to learn everything they could about the disease. When they realized how little was known, they started raising money to fund research. That effort blossomed into the Fanconi Anemia Research Fund Inc., a full-fledged research program that has raised $6 million and led directly to the characterization of three of the eight genes known to be responsible for Fanconi anemia.
When the Frohnmayers began, only a handful of researchers had more than a casual familiarity with the disease. Now there are more than 40 scientists studying it in Amsterdam, Paris, Seattle, Boston, at the National Institutes of Health (NIH) in Bethesda, Md., and elsewhere. When Kirsten and Katie fell sick, the Frohnmayers could do little but comfort them. With Amy, they are in a race.
The first attempt to correct a genetic disease in a human being was made in September, 1990. W. French Anderson, then at the NIH, treated a four-year-old Cleveland girl named Ashanthi DeSilva suffering from a genetic disorder called adenosine deaminase deficiency. The disease stems from a mutation in the gene for an enzyme called adenosine deaminase, or ADA, and cripples the immune system, leaving its victims defenseless against infections. Anderson's treatment had worked well when applied to cells in a lab dish, but when he gave it to his young patient, it was disappointing. It produced only a partial correction of her ADA deficiency.
TROJAN HORSE. The treatment depended upon a clever strategy under development at the time in a handful of laboratories. The problem the researchers faced was that gene therapy would not be effective unless the corrective genes were inserted into the nuclei of thousands or even millions of diseased cells. In most cases, simply injecting the genes into the specific tissue where they were needed would have no effect, because the genes would not reach the cells' nuclei.
Investigators then realized that nature had given them an unlikely tool for the job. Many viruses produce disease by entering cell nuclei and integrating their genes with those of the cells. Anderson removed white blood cells from his young patient and mixed them with a specially engineered virus in which the key disease-causing genes had been removed and a working copy of the adenosine deaminase gene added. If the virus behaved as expected, it would infect the cells but instead of inserting viral disease genes, it would pass on the ADA gene. The infected cells would then begin to produce ADA, correcting Ashanthi's deficiency.
The experiment proved that the concept could work. Over a period of two years, the procedure was repeated about a dozen times, and her body now produces about 25% of the normal amount of ADA. But that's not quite enough, and Ashanthi, now 12 years old and in the seventh grade, continues to need injections of ADA. The gene therapy isn't very efficient--the number of cells that acquired the corrective gene was too small. "We got a rude awakening," says Anderson. "It is much more difficult to get genes into cells than we thought it would be, and once in the cells, genes were turned off after a few days or weeks." The gene therapy eased Ashanthi's symptoms, but it wasn't yet close to a cure.
The disappointing outcome sent researchers back to their labs to design better viral delivery systems and other means of getting genes where they needed to go. "All along, the three problems [with] gene therapy have been delivery, delivery, and delivery," says Dr. R. Michael Blaese, one of Anderson's colleagues at the NIH. Researchers began to fine-tune their viral carriers to try to improve their efficiency. They also began to explore other means of getting genes into cells: Now, a new set of gene therapy "tools" is available (below). "Within the next decade, there will be an exponential increase in the use of gene therapy," predicts Helen M. Blau, director of the gene-therapy technology program at Stanford University.
The research has also moved from academic laboratories to industry. Dozens of companies are now involved in developing gene therapy. Treatments for heart disease are likely to be available in the next two to three years from Valentis, Vical, and Vascular Genetics, a subsidiary of Human Genome Sciences. Vical and Introgen Therapeutics are completing human trials of gene therapy for melanoma and head and neck cancer. Targeted Genetics has completed promising but preliminary human trials of gene therapy to treat cystic fibrosis, while Cell Genesys, Avigen, and Chiron Technologies are targeting hemophilia.
The Frohnmayers have been waiting for treatments like this since 1983. "That had been a good time in our lives," Lynn remembers. "We had three wonderful, healthy children, and felt very blessed--when suddenly Kirsten got sick." Then 10 years old, Kirsten began to feel weak and tired and bruised easily. But she didn't have the signs of Fanconi anemia, which can include missing fingers, extra digits, or shortened arms and legs. Kirsten was, to all appearances, normal. "We had read about Fanconi anemia as a possible diagnosis, and we were grateful she didn't seem to fit the mold, because everything about the disease was so discouraging," Lynn says.
Lynn and Dave were celebrating their 13th wedding anniversary when they got the dreadful news about Kirsten. Additional genetic tests revealed that Katie, then four, also had the disease. Mark was unaffected. "In one blow, we went from thinking we had three very healthy children to realizing that both our daughters had a life-threatening illness....It was just an overwhelming experience." And there was an element of unreality. "Passing either one of them on the street, you would never know anything was wrong with them," says Dave. "Kirsten was pale, but Katie was bouncy, bright, and vibrant."
Fanconi anemia is a recessive disease--it occurs only when children inherit two copies of the defective gene, one from each parent. The disease appeared only because Dave and Lynn, who each carry a single copy of the Fanconi gene, came together. Each of their children had a one-in-four chance of getting two copies of the gene. It is only by chance that the disease struck their daughters and not their sons.
When Katie and Kirsten Frohnmayer were first diagnosed, little was known about the disease. It was far too uncommon to attract much attention from researchers: Fanconi anemia affects only about 1,500 Americans and 3,000 people worldwide. No one knew what gene was responsible for the disease or how it did its damage. All that was known was that something was destroying blood-producing bone-marrow cells. Patients also had increased susceptibility to cancer, especially leukemia. And there was no cure. The Frohnmayers learned about the potential of gene therapy from an episode of the National Public Broadcasting show Nova and realized that might be the one hope for their children. "If there was going to be a fix," says Dave, "that's the way it had to go."
Dave and Lynn immediately set out to find other families with Fanconi anemia to see what they could learn. "Our first support group had 19 families in it," says Lynn. "And David and I wrote out a newsletter at the computer on our kitchen table" in 1985. Kirsten's blood counts, meanwhile, were plummeting. "It was just horrific to watch," says Lynn. They took her to Harvard Medical School, where doctors advised treatment with a male hormone called oxymethalone. On the West Coast, experts said the treatment was worthless. "When she was 13, we put her on a male hormone. It was a horrible thing to do, but we felt that our backs were completely against the wall." Kirsten responded to the drug. Her blood counts improved and held steady. Then Katie developed the first symptoms.
By 1988, the Frohnmayers were beginning to interest researchers in the disease. Dr. Arleen D. Auerbach, a geneticist at Rockefeller University, asked if they could raise $50,000 for research. They wrote letters to friends and relatives and soon had the money. The following year, two more researchers asked for funding. The Frohnmayers realized they would need help, so they assembled a scientific review board to assess the value of the proposed research. In 1989, the Frohnmayers formalized their work with the establishment of the Fanconi Anemia Research Fund.
They also held their first scientific symposium that year. They invited every scientist who was working on the disease or who they thought might be interested. About 18 scientists attended, along with a number of patients. When one session of the symposium ended, Lynn found a scientist crying in the ladies' room. "I have been working with cells under a microscope," the researcher told her. "I have never ever seen a person with this disease."
DECODING TASK. The Frohnmayers used the funds they were raising to promote projects to find the gene or genes responsible for Fanconi anemia. In 1991, they also held the first of their annual summer-camp meetings for Fanconi anemia families. The getaways proved deeply comforting. "The camps are phenomenal," says Jack Redekop of Calgary, Alberta, who has a nine-year-old daughter with the disease. "With a disorder like this, you feel very distanced, without a lot of people to relate to." When he went to his first camp, he met several hundred people and some of the leading Fanconi anemia researchers. Of the Frohnmayers, he says: "They have to deal with their grief and an incredible amount of suffering, and yet it is inspirational to see them....They deal with their grief and continue on."
By that time, Katie had developed severe complications, including a condition called moya moya, a narrowing of the carotid artery running up through the neck to the brain. That led to one stroke, and then two more, from which, finally, she could not recover. When she was 7, Katie had been told she had at most two months to live. She lived for five more years. "Mom, I am just so glad that I have had these years," she told Lynn. At that point she had been hospitalized 18 times in 14 months. Katie died in 1991. She was 12 years old.
The summer camps were giving researchers their first opportunity to collect blood and test DNA from a comparatively large number of Fanconi anemia families. Just after Katie died, the first Fanconi anemia gene was found--a direct result of the Frohnmayers' efforts to promote research. Two more genes have been found since, and researchers now know there are eight genes that can cause the disease. Without this knowledge, gene therapy would be impossible.
While the genetics of Fanconi anemia were slowly being decoded, gene therapy was moving closer to reality. Researchers who had been humbled by the earlier disappointments began to devise improved methods of delivering genes to cells. One of the most promising new techniques relies on a tiny organism called adeno-associated virus (AAV), already present in 80% of the human population. AAV is able to avoid the defenses of the human immune system, possibly because it does not cause disease. It can worm its way into a variety of cells in the brain, the nervous system, and the lungs that could not be reached by the first-generation gene-therapy viruses. When tested in mice and monkeys, the corrective AAV genes have functioned for up to two years so far.
Dr. James M. Wilson, director of the Institute for Human Gene Therapy at the University of Pennsylvania, expects to begin human-safety trials using AAV to treat muscular dystrophy and hemophilia later this year. "Now we have a more realistic view of what the delivery systems can and cannot do. That means we can match them to the diseases they are most likely to treat," says Wilson. Chiron Technologies Corp. is experimenting with AAV to treat dogs with hemophilia, while Targeted Genetics Corp., in conjunction with Stanford University, is using it to treat sinus inflammation in cystic fibrosis patients. The results from early safety trials, which were announced in late March, showed that the therapy caused no side-effects and reduced the sinusitis of the 23 patients.
UNLIKELY HELPER. In perhaps the most stunning turnabout in gene therapy, Dr. Inder M. Verma, a virologist at the Salk Institute for Biological Studies in La Jolla, Calif., is using the AIDS virus to make a gene-therapy delivery system. He has developed a pared-down, deactivated version of the virus that retains the ability to infect cells but no longer contains the deadly genes that allow it to reproduce and spread. Like AAV, HIV can infect virtually every cell in the body. But because HIV is easier to manufacture and can hold larger pieces of DNA than AAV, Verma believes it could one day be the preferred viral delivery system.
Verma's lab has used the virus to deliver genes into the brain, liver, muscle, bone marrow, and retinal cells of rats and mice. The genes seem to function for at least five months. Verma hopes his modified AIDS virus can do as well in humans. He expects his first human experiments to be directed against hemophilia and Fanconi anemia. There are at least 40 other viruses being tested as potential gene carriers, including Epstein Barr virus (EBV) and the herpes virus.
Some researchers are simply abandoning the virus approach. Transgene and Valentis Inc. are developing tiny fat globules designed to carry tumor-suppressor genes directly into cancer tumors. Vical Inc. and Vascular Genetics Inc. have dispensed with delivery systems altogether. They inject genes directly into muscle cells in a procedure as simple as administering a shot of penicillin. The naked DNA, as it's called, is taken up by some of the muscle cells, where the genes begin to function for at least a brief period. In the April issue of the journal Nature Biotechnology, researchers at GeneMedicine Inc., now part of Valentis, in The Woodlands, Tex., reported using this technique to produce the promising anticancer drug endostatin in the muscle cells of laboratory mice. The drug has proved difficult to manufacture, but with injections of endostatin genes, the muscle cells took over that job. The drug was soon moving through the bloodstreams of the mice, where it inhibited the growth of cancer tumors and helped prevent the cancer's spread.
One drawback of these nonviral delivery systems is that they may be far less efficient than viruses at getting genes into cells. In addition, the genes might not survive long enough to be of substantial help. Companies such as Chromos Molecular Systems Inc. and Athersys Inc. are trying to find a way around these problems by developing artificial chromosomes--long, fibrous strings of genetic material that behave like human chromosomes. The artificial chromosomes are constructed so that the corrective gene is accompanied by components essential for long-term function in the cell. So far, studies of cultured human cells show that artificial chromosomes can be maintained for the lifetime of the cell. Getting enough of them into the target tissue is still a problem, however. Gil van Bokkelen, the CEO of Athersys, says human trials are several years away.
Even more fantastic are the attempts by some researchers to do more than simply add a corrective gene--they want to repair the existing error. "It's a form of molecular Wite-Out to correct the genetic typos," says Blaese, formerly of the NIH and now the chief scientific officer at Kimeragen Inc. The process would still require a delivery system, but the corrective genes would be constructed in such a way that they would replace the defective genes rather than just plugging in anywhere and going to work. With this approach, doctors would not have to worry about DNA inserting itself into the wrong place and potentially causing harm.
PRESSING ON. Dr. Johnson M. Liu, a hematologist at NIH, is using this approach with Fanconi anemia. Working with Amy Frohnmayer's bone-marrow cells, he has shown that he can correct the genetic defect that is causing her illness. The next step is to show that the technique will correct anemia in a mouse. If that works, humans--maybe even Amy--could be next. The first human trials are likely to be years away, but the Frohnmayers are pressing on. "You can never afford to lose hope," says Dave.
The most recent findings on Fanconi anemia were released on May 15 at the Frohnmayers' scientific symposium in Chicago. This year, the focus was on gene therapy. Verma presented the results of his most recent experiments, which use the AIDS virus to deliver Fanconi genes to bone-marrow cells. "I am quite excited," he says. "We haven't overcome all the obstacles, but it looks good."
Gene therapy's immediate goal is to slow or stop illness in Amy and millions of others who cannot be helped by conventional treatment. Ultimately, researchers could move toward gene therapy that includes correcting genetic defects in human sperm and eggs. Such germ-line therapy, as it's called, would not only correct disease in an individual but it would also eliminate the genetic flaw from all of that individual's offspring. Such a treatment could wipe out Fanconi anemia in the Frohnmayer family, for example. It could also mean that families plagued by heart disease or breast cancer could avoid passing on that genetic vulnerability to their children.
If all this comes to pass, the genetic legacy we pass on to our children will, for the first time, be under our control. That would be a boon for treatment of disease, but it raises troubling moral and ethical questions. Some bioethicists worry that the power to alter genes could be turned to questionable ends, such as making human beings stronger or more intelligent. "We are kidding ourselves if we think we can say yes to therapy and no to enhancements," says Erik Parens, a bioethicist at the Hastings Center in Garrison, N.Y.
As with any emerging technology, gene therapy has met its share of failures. Enthusiasts were accused of overselling the concept when they couldn't deliver the goods five years ago. In 1995, a review panel at NIH published a report criticizing researchers and investors for rushing patients into clinical trials before fully understanding the unsolved problems that remained. Despite the advances in recent years, some researchers are still taking a wait-and-see attitude. "Gene therapy has not cured any disease up to this point. It's exciting, but a lot more animal research needs to be done," says Rockefeller University's Auerbach. Still, researchers are hopeful that recent advances signal that the second wave of therapies will be successful. "It appears that gene therapy may have turned a corner," says Anderson.
Sadly, these advances have come too late to help Kirsten Frohnmayer. The male hormone treatments she began as a child helped her to survive until she was 24. She died in June, 1997. Amy's future is uncertain, but it's conceivable that the experiments now under way could pay off in time to save her life. On the wall in their living room, the Frohnmayers display a pastel drawing of Katie when she was Amy's age. They look so much alike they could be twins. But Amy's future might be different from her sister's.
"It is a constant race against the old clock," says Lynn. "It is terrifying to be a patient--or the parents of a patient--and to be desperately counting on gene therapy right now." The Frohnmayers have made an enormous contribution to the research that could help millions of others. "What pushes us," says Lynn, "is the hope that we can still save Amy." No one could have a more powerful incentive.
In August, the Frohnmayers will gather with other families in Lake Geneva, Wis., for their annual family camp. Some faces will be missing--the faces of children who have died since the last gathering. With the promise of gene therapy, the Frohnmayers can hope that one day they will leave such a gathering knowing that the next time they meet, everyone will return.
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