Two babies rescued from previously incurable leukemia after receiving infusions of gene-edited immune cells are doing well at home more than a year after initial treatment, scientists said on Wednesday.
Layla Richards became the first person in the world to get the "off-the-shelf" cell therapy developed by French biotech firm Cellectis at Britain's Great Ormond Street Hospital in 2015. A second girl was treated soon afterwards.
Now the team involved in both cases have published details of their work in a peer-reviewed journal, reporting that the two girls remained disease-free 18 and 12 months after treatment respectively.
Waseem Qasim, a consultant immunologist at the London hospital, said the two cases showed the gene-edited cells were working, although long term monitoring was still required.
"While both patients are now at home and are doing well, we must treat these results with some caution as we don't yet know if the technique will be successful in treating a larger number of patients," he said.
Initial Phase I clinical trials using the cell therapy, known as UCART19, are now underway in both children and adults.
The idea of genetically altering immune cells called T cells so that they can attack cancers more effectively is currently one of the hottest areas of medical research.
But while other drugmakers such as Novartis, Juno and Kite have treatments that use modified T-cells extracted from individual patients, UCART19 is derived from healthy donors and aims to be a universal therapy.
That should make it cheaper to produce and particularly suitable for patients who do not have sufficient quantities of healthy T cells to start with, such as very young children.
One risk is that such a universal approach could trigger graft versus host disease (GVHD), where the patient's body reacts against the donated cells.
Writing in the journal Science Translational Medicine, Qasim and colleagues reported that Layla did indeed develop GVHD in the skin two months after treatment but the problem was resolved after she received steroids and a bone marrow transplant.
Simon Waddington of University College London, who was not directly involved, said the findings showed the promise of this new type of cell therapy and would help teach scientists how to improve the process both in terms of efficiency and safety.