Leukaemia success heralds wave of gene-editing therapies

Layla, a one-year-old girl with leukaemia, is in remission thanks to gene-editing technology that allowed her to receive modified immune cells from another person.

Her case represents the second trial of gene-editing as a therapy – the first was carried out last year in patients with HIV. More similar trials are planned – and companies are also preparing to trial therapies that inject DNA that codes for gene-editing enzymes directly into the human body.

Immunologist Waseem Qasim of Great Ormond Street Hospital for Children NHS Trust in London, whose team treated the girl, says that his team had planned to start a safety trial next year in 10–12 patients.

But when the researchers came across the baby, in whom all other treatments had failed, they were able to obtain special permission to treat her with the new technology, developed by researchers from Cellectis, a company headquartered in Paris. Several months after the procedure, Qasim says that she is doing well.

To administer the therapy, the researchers extract immune cells called T-cells from a healthy donor, and expose them to a type of DNA-cutting enzyme called a TALEN. The enzyme deactivates immune genes that would otherwise cause the donor cells to attack when injected into a person with leukaemia, and modifies genes to protect the new cells from anti-cancer drugs that the patient is taking.

The individual then undergoes therapy to destroy his or her own immune system, which is replaced with the modified cells. The treatment is not a permanent solution for leukaemia patients, says Qasim, but rather a ’bridge‘ to keep the person alive until a matched T cell donor can be found.