Scientists in the UK have used a revolutionary new type of gene therapy to treat a young patient with relapsed T-cell leukaemia. The administration of the technique – a world first – has raised hopes it could soon help to tackle other childhood cancers and serious diseases. Alyssa, from Leicester, had undergone chemotherapy and a bone marrow transplant in a bid to alleviate her leukaemia, without success. With no further treatments available, prospects for the 13-year-old were grim. But after receiving an infusion of donated T-cells, altered using a new technology known as base editing, Alyssa is recovering and has been in remission for six months. “We are in a strange cloud nine to be honest. It’s amazing,” said her mother, Kiona. Now the team at London’s Great Ormond Street hospital (Gosh) who treated Alyssa are preparing to recruit another 10 T-cell leukaemia patients, who have also exhausted all conventional treatments, for further trials. If these are successful, it is hoped base-edited cells could be given to patients affected by other types of leukaemia and other diseases. “This is our most sophisticated cell engineering so far, and it paves the way for other new treatments and ultimately better futures for sick children,” said immunologist Professor Waseem Qasim, one of the project’s leaders. He will present the results of the trial at the American Society of Haematology meeting in New Orleans this weekend. T-cell leukaemia is a cancer that affects a class of white blood cells known as T-cells. These fail to develop properly and grow too quickly, interfering with blood cell growth in the body. Standard treatments include bone marrow transplants and chemotherapy. In Alyssa’s case, these failed to halt the progress of the disease and her only option appeared to be palliative care. But recent progress in cell therapy offered a new method for tackling her condition. T-cells were collected from a healthy donor and changed so that they could kill other T-cells, including her leukaemia cells. This was done using base editing, which allows scientists to make a single change in the billions of letters of DNA that make up a person’s genetic code. Other technologies can achieve such minute changes, but are associated with more side effects. This is less of a problem with base editing and allowed the Gosh team to make a series of separate changes to the donated T-cells. These complex alterations were needed to ensure the realigned T-cells only attacked leukaemic T-cells and did not destroy each other through “friendly fire”. They also allowed the cells to work after chemotherapy and also prevented them from affecting normal cells. Following her original treatments, Alyssa never achieved complete remission. After her base-edited cell therapy and a second bone marrow transplant to restore her immune system, she has been leukaemia-free for more than six months. “The doctors have said the first six months are the most important,” said Kiona. “We don’t want to get too cavalier, but we kept thinking: ‘If they can just get rid of it, just once, she’ll be OK.’ And maybe we’ll be right.” The crucial point is that Alyssa’s therapy was based on donated T-cells which can be edited, so donor-matching is not a problem. “This is an ‘off the shelf’ universal cell therapy and – if replicated – will mark a huge step forward in these types of treatments,” said Dr Louise Jones of the Medical Research Council, which funded the project.