A teenage girl's incurable cancer was removed from her body after the first use of a revolutionary new type of treatment.
All other types of treatment for Alice's leukemia were unsuccessful.
That's why doctors at Great Ormond Street Hospital used "base editing" to perform a feat of bioengineering and create a new, living drug for her.
Six months later, the cancer is gone, but doctors are still keeping a close eye on Alisa in case it comes back.
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Alisa, a 13-year-old from Leicester, England, was diagnosed with T-cell acute lymphoblastic leukemia in May last year.
T-cells are supposed to be the body's guardians, seeking out and destroying threats, but for Alice, they have become a threat themselves and are beginning to spiral out of control.
Her cancer was aggressive.
Chemotherapy, followed by a bone marrow transplant, failed to remove it from her body.
Without administering the experimental drug, the only thing left was to make Alice as comfortable as possible.
"I'd end up dead," Alice said.
Her mother, Kiona, says that this time last year she dreaded Christmas "thinking it was our last with her".
And then in January, she just "cried" on her daughter's 13th birthday.
What happened next would have been unimaginable just a few years ago, made possible by incredible advances in genetics.
The Great Ormond Street team used a technique called base editing, which was invented just six years ago.
Databases are the dictionary of life.
Four types of bases - adenine (A), cytosine (C), guanine (G) and thymine (T) - are the building blocks of our genetic code.
Just as the letters of the alphabet make up words that carry meaning, the billions of bases in our DNA make up the instructions for using our bodies.
Base editing allows scientists to target a precise part of the genetic code and then alter the molecular structure of just one base, turning it into a different one and changing its genetic instructions.
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A large team of doctors and scientists used this tool to build a new type of T-cell that can hunt down and kill Alice's cancerous T-cells.
They started with healthy T-cells that came from a donor and began to modify them.
- The first base edit disabled the targeting mechanism of the T-cells so they wouldn't attack Alice's body
- Another edit removed a chemical marker, called CD7, found on all T-cells
- The third edit was an invisibility cloak that prevented the chemotherapy drug from killing the cells.
The final stage of genetic modification instructed the T-cells to hunt down anything with the CD7 label on it to destroy all T-cells in its tissue, including the cancerous ones.
That's why this branding must be removed from therapy, otherwise it would simply destroy itself.
If the therapy is successful, Alice's immune system, including T-cells, will be rebuilt through a second bone marrow transplant.
When the idea was explained to the family, Kiona's mother was left wondering: "You can do it?".
It was Alisa who made the decision to be the first to undergo the experimental therapy - which contained millions of modified cells - in May this year.
"She is the first patient to be treated with this technology," says Professor Wasim Kasim, from UCL and Great Ormond Street.
He said this genetic manipulation was a "very rapidly developing area of science" with huge potential for a wide range of diseases.
Alisa was left vulnerable to infection, as the engineered cells attacked both the cancerous T-cells in her body and those that protect her from disease.
After a month, Alisa was in remission and received a second transplant to rebuild her immune system.
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Alisa spent 16 weeks in the hospital and could not see her brother, who was still going to school, lest he accidentally spread the germs to her.
Everyone was worried when they noticed signs of cancer again during the examination after three months.
But her two most recent scans were clean.
"You just learn to appreciate every little thing. I am extremely grateful to be here now," says Alisa.
"It's crazy. It's just fantastic that I got this opportunity, I'm very grateful for it, and it will help other children in the future."
She is currently looking forward to Christmas, being a maid of honor at her aunt's wedding, getting back on her bike and "all the things that normal people do".
The family hopes the cancer won't return, but they're already grateful for the extra time they bought.
"Getting this extra year, these last three months that she was home, was a gift in itself," Kiona says.
Father James said: “It's quite difficult for me to talk about how proud we are. When you see what she's been through and the vitality she brings to every situation, it's just amazing."
Most children with leukemia respond to the main treatment methods, but it is believed that up to a dozen of them a year could benefit from this therapy.
Alisa is only the first of 10 people who received the drug as part of a clinical trial.
Dr Robert Chisa, from the Bone Marrow Transplant Unit at Great Ormond Street, said:
"It's extremely exciting. This is clearly a new area of medicine, and it's fascinating that we can redirect the immune system to fight cancer."
This technology, however, has only scratched the surface of what editing bases can do.
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Dr. David Liu, one of the inventors of base editing at the Brod Institute, told me that it was "a little surreal" that people were being treated just six years after the technique was invented in the first place.
During Alice's therapy, a part of the genetic code had to be broken every time the base was edited so that it would no longer function.
But there is also a more subtle application, when instead of turning off instructions, you can fix a faulty base.
Sickle cell anemia, for example, causes only one change in the base that can be corrected.
Therefore, trials of editing bases in sickle cell disease, as well as hereditary high cholesterol and the blood disorder beta-thalassemia are already underway.
Dr. Liu said that "the therapeutic application of base editing is just beginning" and that it is "a great honor to be a part of this era of therapeutic gene editing in humans" as science is now "taking crucial steps towards taking control of our genomes".
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