A therapy that until recently could have been considered science fiction has halted the evolution of aggressive forms of leukemia in several patients, announce British doctors, quoted by the BBC. The experimental treatment involves precisely editing the DNA in white blood cells to turn them into a ‘living medicine’ that fights cancer. The first teenage girl to receive the treatment, in 2022, is still healthy and plans to become a cancer researcher. Eight more children and two adults diagnosed with T-cell acute lymphoblastic leukemia have received treatment, and nearly two-thirds (64%) of them are in remission.
Alyssa Tapley, the teenager who got cured
T cells are considered the body’s defenders, seeking out and destroying threats, but in this form of leukemia they multiply out of control. For those who entered the experimental program, chemotherapy and bone marrow transplants had failed and there was no other solution.
“I really thought I was going to die and not be able to grow up, do all those things that all children deserve to be able to do,” says Alyssa Tapley, the first person in the world to enter the clinical trial, at Great Ormond Street Hospital, in Great Britain, three years ago.
Now the cancer is undetectable and the 16-year-old is taking driving lessons and making plans for the future. She wants to study Biomedical Sciences and hopes to one day be involved in leukemia research.
How scientists did it
The revolutionary treatment three years ago involved destroying her old immune system and developing a new one, writes the BBC.
Teams from University College London (UCL) and Great Ormond Street Hospital used a technology to edit bases in DNA.
The researchers aimed to harness the natural power of healthy T cells to seek out and destroy threats and direct it against T-cell acute lymphoblastic leukemia without the treatment self-annihilating. They started with healthy T cells from a donor and began to modify them.
The first base edit disabled the targeting mechanism of the T cells so they could not attack the patient’s body.
The second edit removed a chemical tag, called CD7, present on all T cells. Its removal was essential to prevent the therapy from self-destructing.
The third edit created an “invisibility cloak” that prevented cells from being destroyed by a chemotherapy drug
The final stage of genetic modification instructed the T cells to seek out and destroy anything bearing the CD7 mark. At this stage, the modified T cells would destroy any other T cell they encountered, whether cancerous or healthy, but would not attack each other.
The therapy is given to patients, and if after four weeks the cancer can no longer be detected, they can have a bone marrow transplant to regenerate their immune system.
“A few years ago, that would have been science fiction.” says Professor Waseem Qasim from UCL and Great Ormond Street Hospital.
Doctor: “I’m very happy that we managed to give hope”
The study, published in the New England Journal of Medicine, presents the results of the first 11 patients treated at Great Ormond Street and King’s College Hospital. According to the report, nine of them achieved a deep remission, which allowed them to have a bone marrow transplant.
In the case of seven patients, the disease was no longer detected, between three months and three years after treatment. In two cases, the cancer lost its CD7 markers, which allowed it to hide from the therapy and reappear in the body.
Experimental treatment also has risks. One of the biggest includes infections, while the immune system is destroyed.
“Given how aggressive this form of leukemia is, the clinical results are truly remarkable and I am obviously very happy that we have been able to offer hope to patients who would otherwise have lost it” said Dr Robert Chiesa, from Great Ormond Street Hospital’s Department of Bone Marrow Transplantation.
Commenting on the research, Dr Tania Dexter, senior physician at UK stem cell organization Anthony Nolan, said: “Given that these patients had a poor chance of survival before the study, these results bring hope that similar treatments will continue to evolve and become available to more and more patients.”
