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Gene-Editing Experiment Improves Sight In Patients With Impaired Vision


For the first time, doctors are reporting that they have restored vision to people blinded by a rare genetic disorder using the revolutionary gene-editing technique known as CRISPR.

NPR health correspondent Rob Stein joins us now. Rob, helping blind people see sounds miraculous. What exactly do they do?

ROB STEIN, BYLINE: Yeah. So they use this gene-editing technique called CRISPR, which lets scientists make very precise changes in DNA much more easily than ever before. It's been showing promise for treating blood disorders, like sickle cell disease. And doctors are trying to use it to treat cancer. But those experiments involve taking cells out of the body, editing them in the lab and then infusing the modified cells back into patients' bodies. In this case, they did something completely different. You can't take cells out of the retina in the eye and put them back in. So they infused the CRISPR gene editor directly into cells in the retina in the eye to edit a gene while still inside the body - inside the eye.

Here's Dr. Eric Pierce at the Harvard Medical School. He's helping conduct this experiment.

ERIC PIERCE: This is the first time we're having evidence that gene editing is functioning inside somebody. And it's improving, in this case, visual function. We're thrilled about this.

STEIN: Now, you know, Pierce stresses that this is very preliminary. Doctors have only tried this on seven volunteers so far. And they have to treat a lot more patients and follow them a lot longer to really know for sure how well it's working. But nevertheless, they're ecstatic that it looks safe and it looks like it could be helping people. And, you know, A, NPR got exclusive access to interview two of these volunteers, and they're thrilled, too.

MARTÍNEZ: Yeah - blown away by everything so far, Rob, especially getting that access. So what can you tell us about these people?

STEIN: Yeah. So they were both born with a rare genetic condition called Leber congenital amaurosis, which is caused by a genetic mutation that progressively disables the function of key light-sensing cells in the retina. Dr. Pierce and his colleagues infused billions of harmless viruses that were genetically modified to carry the CRISPR gene editor into their retinas to literally cut out the mutation. The hope is that it would restore the function of the cells in the retina and restore at least some vision. And it looks like it worked for at least some of the patients.

One of them is Carlene Knight. She's 55, and lives outside Portland, Ore. Her vision is still far from normal. But everything is much brighter and clearer. She can find doorways and move around a lot easier, look down and she things she's dropped in the floor. And then there's colors. They're so much more vibrant now.

CARLENE KNIGHT: I've always loved color since I was a kid. It's one of the things I could really, you know, enjoy, even with just a small amount of vision. But now I realize how much brighter they were as a kid because I can see them a lot more brilliantly now. It's - well, it's just amazing.

STEIN: You know, to celebrate, she dyed her hair her favorite color...

MARTÍNEZ: (Laughter).

STEIN: ...Green. Yeah. You know, and I also talked to Michael Kalberer. He's 43 and lives on Long Island. He's reporting a lot of the same things and can do something he hasn't been able to do for years - watch sunsets.

MICHAEL KALBERER: The first time I saw one, I was coming home from a meal with a friend. I see pink in the sky. She goes, yeah, you see the sunset. That's the sunset. And we both smiled at each other. So it was a great moment.

MARTÍNEZ: I'm thinking Carlene's in Oregon. She might be an Oregon Ducks fan. That's why she painted it green - or dyed it.

STEIN: (Laughter) Yeah. That's right.

MARTÍNEZ: Now, Rob, what else could this be used for?

STEIN: Yeah. You know, scientists hope that there are many other diseases that they could use this on, where it's not possible to take cells out of the body, edit them in the lab and infuse them back in - you know, brain diseases like Huntington's and muscle diseases like muscular dystrophy. Now, no one is trying that yet, but this could open the door to that. But these researchers are trying a higher dose on adults and planning kids, too.

MARTÍNEZ: That's NPR health correspondent Rob Stein. Rob, thanks a lot.

STEIN: You bet.

(SOUNDBITE OF MUSIC) Transcript provided by NPR, Copyright NPR.

Rob Stein is a correspondent and senior editor on NPR's science desk.