In a first, doctors injected the gene-editing tool CRISPR directly into cells in patients' eyes. The experiment helped these vision-impaired patients see shapes and colors again.

Transcript

LEILA FADEL, HOST:

For the first time, scientists are reporting they've used the gene-editing technique called CRISPR to restore some vision to people blinded by a rare genetic disease. NPR health correspondent Rob Stein has this remarkable story.

ROB STEIN, BYLINE: Carlene Knight's eyes were so bad she couldn't find her way through the call center where she works, even using her cane.

CARLENE KNIGHT: We have cubicles at work, and I was bumping into the cubicles and really scaring people that were sitting at them (laughter). It's nice. I don't scare people, and I don't have as many bruises on my body (laughter).

STEIN: She can see so much clearer now, and things are so much brighter that she can find doorways, navigate hallways and spot things she drops on the floor instead of having to reach around blindly, like the other day when she dropped a fork on her kitchen floor.

KNIGHT: I just leaned down to pick it up and didn't know where it was, and then I saw it on the floor. So it's very cool.

STEIN: And then there's colors. They're way bolder, more vivid.

KNIGHT: Well, 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: So Knight, who's 55 and lives outside Portland, Ore., dyed her hair her favorite color - green - to celebrate.

Michael Kalberer can now see colors, too, for the first time in years. He noticed it on the dance floor of his cousin's wedding.

MICHAEL KALBERER: I could see the DJ's strobe lights change color and identify them to my cousins who were dancing with me. That was a very, very fun, joyous moment.

STEIN: Kalberer, who's 43 and lives on Long Island, can recognize shapes and light much better, too, and his tunnel vision has opened up, making it way easier to do simple things like eat in a restaurant.

KALBERER: It has enabled me to navigate a plate of food. If I look down at a plate of food and there's a spoon or utensil in it, I can see the edge of the utensil on the outside of the bowl or plate. So those changes are very, very significant to me.

STEIN: He's even doing something he only dreamed about before - watching sunsets again.

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.

STEIN: Knight and Kalberer were born with a rare disease caused by a genetic mutation that disables crucial cells in the retina. The CRISPR gene-editing technique has already shown promise for treating devastating 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 them back into patients. That's impossible for diseases like Knight and Kalberer's.

ERIC PIERCE: We're thrilled about this.

STEIN: Dr. Eric Pierce is a professor of ophthalmology at Harvard Medical School who's helping run the experiment testing the approach. Pierce and his colleagues infuse billions of harmless viruses that have been genetically modified to ferry the CRISPR gene editor into the retinas of Knight, Kalberer and five other patients so far. The hope was that CRISPR would slice out the genetic mutation causing the disease and activate vision-restoring cells. And it looks like it worked, at least for some patients.

PIERCE: We're thrilled to see early signs of efficacy because that means gene editing is working. Right? This is the first time we're having evidence that gene editing is functioning inside somebody and it's improving their, in this case, visual function.

STEIN: It didn't work for all the patients, perhaps because their dose was too low, perhaps because their vision was too damaged. But Kalberer and one other volunteer are reporting improvement, and Knight and one other patient who got a higher dose seem like they can see even better. For two others, it's too soon to tell. Now, none of the patients have normal vision - far from it. Many more patients will have to be treated and followed for much longer to confirm it's safe and know just how much it might be helping. But Dr. Mark Pennesi says the vision of the patients treated so far could continue to improve with time. Pennesi is helping run the experiment at the Oregon Health & Science University in Portland, Ore.

MARK PENNESI: When you improve the function of the retina, sometimes there's a lag for the brain being able to recognize and use that vision. It takes time to learn how to use that improved vision.

STEIN: For their part, Knight and Kalberer are just thrilled that they can see at least a little better.

KALBERER: I'm just incredibly honored and privilege to be part of this and very, very excited to literally hopefully see what comes in the future.

STEIN: Pennesi and Pierce have started trying a higher dose on more adults and are planning to try it on kids, who could benefit the most. And this could open the door to use the same approach to treat other diseases where you can't take cells out of the body, including brain disorders like Huntington's and muscle diseases like muscular dystrophy.

Rob Stein, NPR News.

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Tags: Leber congenital amaurosis  gene-editing  crispr  Treatments  Series: The CRISPR Revolution