NPR

Scientists Still Hopeful About Gene Therapy's Promise

A technician at pharmaceutical company pursuing new gene therapy treatments collects re-engineered viruses, called "vectors." Viruses, stripped of their virulence and ability to replicate, are the most common delivery vehicles for healthy DNA. (AP)

Twenty-five years ago, it seemed as if gene therapy was on the verge of revolutionizing medicine. But that revolution never occurred, and scientists realized that they had been overly optimistic about how quickly they could develop such therapies.

Now, however, there are signs that the field of gene therapy is making definite progress, even if the revolution is still on hold.

The concept of gene therapy is simple. Some diseases are caused by damage to a single gene — for example, cystic fibrosis and hemophilia. Give patients the healthy gene, and in theory, the disease is cured.

Dr. Mark Kay, who now runs the gene therapy program at Stanford University, says that in the early days of gene therapy, it turned out to be extremely difficult to get healthy genes into the cells that needed them.

"If we saw one cell out of a million, or even 10 million or 100 million, that were genetically modified with the gene therapeutic, we would be excited," he says.

How Gene Therapy Works

It's no simple job to get genes into individual cells, but there is one organism that is extremely good at it: a virus.

"What a virus does is deliver its own genetic material to a cell," says Ken Cornetta, president of the American Society of Gene and Cell Therapy.

"What we can do in the setting of gene therapy is to re-engineer that virus to allow it to do what it does best, which is deliver genetic material to a cell. But we can also remove the viral genes, and replace them with the genes that we need to deliver to the cell to treat the disease," he says.

But there were problems. When scientists used viruses to insert genes into patients, their immune systems tried to fight off the virus. And then, when the genes did get in, in some cases they switched on other genes that caused cancer, making the cure nearly as bad as the disease.

"The field was in big trouble 10 years ago, says Joseph Glorioso, a researcher and editor of the journal Gene Therapy. "A lot of people were disillusioned — 'Oh this is never going to work, we thought it would be easy,' and all that."

But Glorioso says gene therapists are a stubborn bunch, and despite the setbacks, many researchers kept at it. He says many therapies take a long time to make it from the lab bench to the bedside.

Take bone marrow transplants. They were first attempted in the 1950s, but it wasn't until the 1980s that they began to be used routinely to treat leukemia and other blood disorders.

A Reason To Be Optimistic

The field of gene therapy is now seeing positive results. Scientists have found new ways to modify viruses to make them better at delivering genes, and several studies are showing that the gene therapy can effectively treat an array of disorders.

There's a therapy for a rare immune disorder called ADA deficiency, and more recently scientists at the Children's Hospital of Philadelphia reported dramatic success using gene therapy to treat a rare inherited form of blindness. It was a small study — only 12 subjects.

"All of the subjects showed improvement," says Kathy High, a Howard Hughes Medical Institute investigator and one of the leaders of the study. She says the improvement was greatest for the children in the study.

High says we should expect to hear more success stories in the coming months and years — and not just for rare disorders, but for more common diseases like AIDS and cancer.

"I really do think that the field, you know, after a long labor, is beginning to deliver," says High. "It's a nice time to be working in this field."

Maybe now, scientists' optimism is justified.

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Transcript

STEVE INSKEEP, host:

And as Iceland considers how to pay, let's move next to some research that has yet to pay off. For nearly 20 years now, scientists have been saying that successful gene therapies were just around the corner. We have yet to round that corner. Many scientists admit they were probably a little too optimistic. But there are signs that these therapies will work for some diseases someday. NPR's science correspondent Joe Palca has more.

JOE PALCA: Twenty-five years ago, Mark Kay was finishing up a PhD in genetics and preparing to enter medical school. He was intrigued by the notion of gene therapy, but he thought it might be a waste of time to enter the field, because he still had four years of medical school to finish and then a medical residency.

Dr. MARK KAY (Director, Gene Therapy, Stanford University): And I thought by that time all the interesting diseases would be treated by gene therapy because the concept itself was so simple.

PALCA: And the concept is simple. Some diseases are caused by damage to a single gene - cystic fibrosis and hemophilia are examples. So give patients the healthy gene and the disease is cured - in theory. Mark Kay stuck with gene therapy and now runs the program at Stanford University. He says it turned out to be extremely difficult to get healthy genes into the cells that needed them.

Dr. KAY: We saw one cell out of a million, or even 10 million or 100 million, that were genetically modified with the gene therapeutic, we would be excited.

PALCA: It's no simple job to get genes into individual cells. But there is one organism that is extremely good at it - a virus.

Dr. KEN CORNETTA (President, American Society of Gene and Cell Therapy): What a virus does is it delivers its own genetic material to a cell.

PALCA: Ken Cornetta says that's what viruses do when they infect cells. Cornetta is the president of the American Society of Gene and Cell Therapy.

Dr. CORNETTA: What we can do in the setting of gene therapy is to re-engineer that virus to allow it to continue to do what it does best, which is deliver genetic material. But we can also remove the viral genes, and replace it with the genetic material that we need to deliver to the cell to treat the disease.

PALCA: But there were problems. When scientists used viruses to insert genes into patients, their immune systems tried to fight off the virus. And then, when the genes did get in, in some cases they switched on other genes that caused cancer, making the cure nearly as bad as the disease.

Mr. JOSEPH GLORIOSO (Editor, Gene Therapy): The field was in big trouble 10 years ago.

PALCA: Joseph Glorioso is a researcher and editor of the journal Gene Therapy.

Mr. GLORIOSO: A lot of people were disillusioned, you know: oh, this can never work. We thought it was going to be easy, and all that.

PALCA: But Glorioso says gene therapists are a stubborn bunch, and despite the setbacks, many researchers kept at it. And finally, the field of gene therapy is seeing some positive results. Scientists have found new ways to modify viruses to make them better at delivering genes, and several gene therapy studies are having positive results.

There's a therapy for a rare immune disorder called ADA deficiency, and more recently, scientists at Children's Hospital of Philadelphia reported dramatic success using gene therapy to treat a rare inherited form of blindness. It was a small study - only 12 subjects.

Dr. KATHY HIGH (Investigator, Howard Hughes Medical Institute): All of the subjects showed improvement.

PALCA: Kathy High is a Howard Hughes investigator and one of the leaders of the study. She says the improvements were greatest for the children in the study. But a 44-year-old woman who was also in the study had better vision. High recalls talking to her and learning that she had a daughter who was a star softball player.

Dr. HIGH: What she described is that she used to go to the games, and her husband would sit next to her and do sort of a play by play. And about two months after she got the injection, she actually saw her daughter steal home in a game. And, you know - so, you know, that's really - some of these stories I can never tell without getting emotional.

PALCA: High says we should expect to hear more success stories in the coming months and years, and not just for rare disorders, but for more common diseases like AIDS and cancer.

Dr. HIGH: I really do think that the field, you know, after a - after a long labor, is beginning to deliver. And so I think that that's good. I mean, it's a nice time to be working in this field.

PALCA: Maybe now, scientists' optimism is justified.

Joe Palca, NPR News, Washington.

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INSKEEP: You're listening to MORNING EDITION from NPR News. Transcript provided by NPR, Copyright NPR.

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