CRISPR base editing saved Alyssa Tapley’s life

At 13, Alyssa Tapley’s T-cell leukaemia moved too fast after chemotherapy and a bone marrow transplant failed. She was offered a trial at Great Ormond Street Hospital in London using CRISPR base editing to modify CAR T-cells so they would not attack T-cells li

When Alyssa Tapley’s breathing changed in the early hours, her father noticed before anyone else. Soon after, she was in A&E and then intensive care with double pneumonia for days. When she woke up. the grim reason for the decline was already being treated: she’d been started on chemotherapy for leukaemia—cancer that develops when immune cells in the blood turn cancerous.

She was 13, and the speed of the crisis felt absolute. Her parents were told it was a matter of weeks. Not years. Not months. Weeks.

Alyssa remembers what that meant to someone her age. “Oh my gosh, this is my last birthday,” she said she was thinking. She pictured a life cut short before ordinary milestones—growing up, starting a family, doing the everyday things most people assume they’ll get to do.

After Easter in 2021, she had returned to school when coronavirus lockdown ended. She was tired and struggling to walk home, falling asleep during breaks and lunches. Eventually she was too sick to attend school.

By then, doctors would also have had to figure out exactly what kind of leukaemia she had. Alyssa’s mother and father say it took the doctors a few days to work out what was wrong, and that she had T-cell leukaemia, which is less common than B-cell leukaemia.

Once the diagnosis landed, everything moved quickly. Alyssa had a month of chemotherapy at Leicester Royal Infirmary. It didn’t work. She was given more intense chemotherapy that also failed. At the end of October, she was taken to Sheffield Children’s Hospital for a bone marrow transplant. The plan was familiar in concept even when the outcome is not: doctors kill off blood stem cells—including the cancerous ones—and then replace them with the transplant.

She stayed in hospital for five and a half weeks. She still got home for Christmas, but the reprieve was temporary. Afterward, she developed a fever and had to return to Sheffield. That’s when she learned the transplant hadn’t worked.

“There was nothing else the doctors could do,” Alyssa says. She describes how it didn’t immediately sink in for her, but how it hit her parents hard. Her mother says the hardest part was not having hope.

So they started searching—trying to find anything that could work, even considering other countries. Alyssa’s parents looked as far as remortgaging the house. They kept hearing about CAR T-cells, a treatment in which T-cells are changed so they can attack cancerous cells. They were also told it can work even when a bone marrow transplant fails.

But they were confronted with a brutal limitation. CAR T-cells typically work for B-cell leukaemia, Alyssa says, because if you make T-cells attack T-cells, they kill each other.

Then her consultant from Sheffield heard about a trial that Professor Waseem Qasim was organising. The approach used CRISPR base editing to modify the CAR T-cells so they would not look like T-cells—and therefore would not destroy the very cells they were programmed to attack.

Alyssa’s consultant suggested she might be a good fit. That prompted a trip to Great Ormond Street Hospital in London, where she met Professor Waseem and Doctor Robert Chiesa, who ran the trial.

Her parents weren’t sure she should do it. They worried it wouldn’t work, and that Alyssa would spend what might be her last weeks in hospital in pain, rather than doing something normal—like going to Disneyland. Still, they let her decide.

Alyssa chose to go ahead. She says she felt driven by the lack of control she’d had for so long and by the idea that. even if the treatment didn’t help her. it could help someone else. “I’m doing it,” she said she told herself. At 13. she also felt she hadn’t yet had the chance to live the life that felt so close and so suddenly threatened—so she wanted to take control of something that might change her future.

Before the CAR T-cells were given, she had two weeks of conditioning in hospital. Camera crews filmed part of it. “It was really amazing,” Alyssa said, recalling what it looked and felt like to be at the centre of an experiment that aimed to change the rules of how her immune system behaved.

A week later, Dr Chiesa told her family the cells had multiplied—“the first sign it was working,” Alyssa said.

The trial period also brought companionship in unusual ways. Alyssa says everybody at Great Ormond Street was “so great.” She made a friend even though they didn’t meet for two months. texting instead. and asked the nurses and play specialists to put things on each other’s windows. There was another friend next door, but that girl couldn’t undergo a bone marrow transplant and died.

After four weeks, doctors tested Alyssa’s bone marrow and found nothing detectable—no blood cells to detect. Two weeks later, there was still nothing, and they proceeded with her second bone marrow transplant to replace the blood stem cells.

Even after the treatment worked in the way clinicians can measure, the hardest part came later: going home. In hospital, she says, there was almost always someone nearby to talk to. At home. she was not allowed out of the house in case she caught something. and she wasn’t allowed to see her friends. Her mother went back to work, leaving Alyssa mostly with her dog Holly for almost a year.

She is still in remission now. But not everything is resolved. Her thyroid is underactive, and she says this is because of all the chemotherapy, not because of the CAR Ts.

That detail sits behind her message about the next steps for treatment. She wants the process to become less punishing—less intensive chemo, and more direct movement to CAR Ts when possible. “This is why it’s so important to keep pushing it,” she said. “So maybe someday people won’t have to have this intensive chemo and can go straight on to have CAR Ts.”.

Alyssa turned 17 in January. She is studying for her A-levels and learning to drive—she calls it “a bit scary.” She wants a degree apprenticeship in biomedical science.

She also gets to talk about her experience at conferences. At one of them, she met Professor David Liu, who developed base editing. Alyssa said she cried when she met him, describing the video from the moment as “quite embarrassing.”

For her, the scientific breakthrough isn’t an abstract milestone. It’s the reason she’s here to talk—about why research matters, and why it matters fast enough to change the outcome of a life.

She says she feels “so pleased and privileged” to have the opportunity to speak. Without it, she wouldn’t be here.

CRISPR base editing CAR T-cells T-cell leukaemia bone marrow transplant Great Ormond Street Hospital Waseem Qasim Robert Chiesa David Liu Alyssa Tapley