A revolutionary therapy that would once belong to the realm of science fiction has now shown the ability to reverse aggressive blood cancers in certain patients, according to recent reports from doctors. This treatment hinges on the precise editing of DNA within white blood cells, effectively turning them into "living drugs" to combat cancer. The first recipient of this treatment, a young girl featured in news stories from 2022, remains cancer-free and aspires to become a cancer researcher herself. Recently, eight additional children and two adults suffering from T-cell acute lymphoblastic leukemia have received this treatment, with a remarkable success rate of nearly 64% achieving remission.
In healthy individuals, T-cells are part of the body's defense system, destroying potential threats. However, this type of leukemia causes these cells to grow uncontrollably. Prior to this trial, affected individuals had exhausted options like chemotherapy and bone marrow transplants and faced palliative care as the only remaining choice. Sixteen-year-old Alyssa Tapley from Leicester, who was the first to undergo the treatment at Great Ormond Street Hospital, reflected on her once grim prognosis. "I really did think that I was going to die and I wouldn't be able to grow up and do all the things that every child deserves," she admitted. Now, she is living a full life, pursuing academic and personal goals.
Alyssa's treatment entailed the complete removal and subsequent regeneration of her immune system. Although she endured a four-month hospital stay with strict infection prevention measures, her cancer is now undetectable, requiring merely annual check-ups. She is engaging in normal teenager activities like preparing for A-levels, undertaking the Duke of Edinburgh Award, learning to drive, and exploring future career paths. "I'm looking into doing an apprenticeship in biomedical science, and hopefully one day I'll go into blood cancer research as well," Alyssa shared.
The cutting-edge treatment was developed by a team at University College London and Great Ormond Street Hospital using a technique known as base editing. DNA is composed of four bases: adenine (A), cytosine (C), guanine (G), and thymine (T). Base editing allows scientists to pinpoint and modify a single base within the DNA sequence, altering its molecular structure to revamp the genetic instructions. The researchers aimed to harness the healthy T-cells' ability to target and eliminate threats by reprogramming them to battle T-cell acute lymphoblastic leukemia, a formidable task requiring the redirection of T-cells' aggressive targeting capabilities.
The process began with healthy T-cells from a donor, subjected to multiple genetic modifications: firstly, disabling the T-cells' natural targeting to prevent self-attack; secondly, removing a key marker, CD7, from all T-cells—a critical step to prevent the therapy from self-destructing. The subsequent "invisibility cloak" edit protected the cells from destruction by chemotherapy drugs. Finally, the T-cells were instructed to target any cell displaying the CD7 marker, effectively destroying other T-cells while sparing themselves. Post-treatment, if cancer is undetectable after four weeks, patients undergo a bone marrow transplant to rebuild their immune system.
"A few years ago, this would have been science fiction," said Prof Waseem Qasim from UCL and Great Ormond Street. "We have to basically dismantle the entire immune system. It's a deep, intensive treatment, it's very demanding on the patients, but when it works, it's transformative."