The unprecedented study involves using the gene-editing technique CRISPR to edit a gene while it's still inside a patient's body. In exclusive interviews, NPR talks with two of the first participants.

Transcript

STEVE INSKEEP, HOST:

Doctors are making a new use of the revolutionary gene-editing technique called CRISPR. They're changing people's genes while the patients' DNA is still inside their bodies. The hope here is they'll be able to restore vision to people who lost their sight to a genetic disorder. NPR health correspondent Rob Stein has the first interviews with these patients.

ROB STEIN, BYLINE: Carlene Knight longs to do things that most people take for granted.

CARLENE KNIGHT: Well, I would like to be able to - I don't know - read signs as I go down the street and know where I'm at and pictures and watching movies and facial expressions and to be able to see my granddaughter especially. My granddaughter's face - it would be huge (laughter). It would be really - I think it would be awesome.

STEIN: Michael Kalberer yearns to watch his nieces and nephews play soccer instead of just listening to the games and move around the world without help, read a computer screen. But that's not all.

MICHAEL KALBERER: Maybe be able to, as romantically poetic as it sounds, see a sunset again, see a smile on somebody's face again - it's the little things that I miss.

STEIN: Kalberer is 43 and lives on Long Island in N.Y. Knight is 54 and lives outside Portland, Ore. Both were born with Leber congenital amaurosis, a rare genetic disease that destroys light-sensing cells in the retina, devastating vision.

KNIGHT: I have no peripheral vision whatsoever. That means I cannot see off to the side at all. I can only see straight-ahead about the size of a pencil lead. So just picture looking through a window and trying to see a spider on the floor through a hole about the size of a pencil lead. That kind of gives you an idea of what I can see.

STEIN: And her eyes jump around a lot, often blurring even that tiny window into the world. Something like that happens to Kalberer, too, blurring his small porthole.

KALBERER: Picture - if you've ever gone swimming and gotten water in the goggle. Picture that sensation. But I don't know when that underwater sensation is going to take place. It comes and goes.

STEIN: Both are legally blind.

KALBERER: I do not have visual independence. I do not have visual autonomy. The diagnosis could have broken me, and for a while it did.

STEIN: But then doctors told them about something new. Scientists were trying to use the gene-editing technique called CRISPR to treat people like them. CRISPR allows scientists to make very precise changes in DNA. So doctors think it could help patients fighting many diseases. It's already showing promise for blood disorders like sickle cell disease and being tested for cancer. But in those experiments, doctors are taking cells out of the body, editing them in the lab and then infusing the genetically edited cells back into patients. The experiment Knight and Kalberer volunteered for is the first time scientists are using CRISPR to edit DNA when it's still inside patients' bodies.

KNIGHT: It's mind-boggling to me. It's not an everyday subject where people can say, oh, I had my genes altered (laughter).

STEIN: Doctors infused billions of copies of a harmless virus into Knight's left eye and into Kalberer's right eye. Each virus had been genetically engineered to carry instructions to manufacture the CRISPR gene editor inside their retinas. The hope was that CRISPR would act like a microscopic surgeon, literally slicing out the genetic mutation in cells in the retinas and hopefully restoring at least some of their vision.

Dr. Eric Pierce at Mass Eye and Ear in Boston is helping conduct the study.

ERIC PIERCE: It sounds a bit like science fiction to be injecting billions of tiny, little virus particles under the retina so that they can go make spelling corrections of a gene inside patients' own retinal cells. But it's really happening, and it's very exciting to be part of it. And we're very optimistic about the potential of these kinds of approaches.

STEIN: Doctors started by treating only one eye in each patient with the lowest dose in older patients who had the least to lose because their vision was already so bad, just in case something went wrong. Dr. Lisa Michaels is the chief medical officer at Editas Medicine, the company sponsoring the study.

LISA MICHAELS: No one had ever done direct treatment of gene editing inside the human body. And as a consequence, there was a lot of concerns whether by taking these patients with a very limited vision, we might have had risks such as disturbing their vision and even loss of the little bit they had.

STEIN: So far, it looks safe. So the researchers have already treated two more volunteers with a slightly higher dose and are hoping to treat six more adults and eventually eight children. Doctors are comparing their vision before and after the procedure and between their treated and untreated eyes. But they say it's too soon to say whether it's working. For their part, Knight and Kalberer can't help but hope it will.

KALBERER: It's hard to put into words. You know, you hope for it. You do the best you can. But to even have the possibility - it's a gift.

STEIN: Researchers say the approach could offer a way to treat many other diseases that can't be treated by taking cells out of the body, too, including brain disorders like Huntington's and muscle diseases like muscular dystrophy. They expect to report their first clues about whether it's helping blind people see by the end of the year - Rob Stein, NPR News.

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