Treatment with genetically modified immune cells caused remission in patients with a particular type of acute leukaemia, according to a small US trial.

Once in remission, four of the five patients on the trial became eligible for stem cell transplants - a potential cure.

The findings are published in the journal Science Translational Medicine.

B-cell acute lymphoblastic leukaemia (B-ALL) is a fast-growing form of leukaemia, characterised by high levels of malignant white blood cells known as B-cells.

Patients are offered chemotherapy, and this can cure some. But if the disease doesn't respond, or if it comes back again they can be given further chemotherapy. If this doesn't work they have few options.

One option is to have further chemotherapy to induce a remission, and carry out a stem cell transplant. This too can cure the disease.

Dr Renier Brentjens and his team at the Memorial Sloan-Kettering Cancer Center in New York set out to develop a treatment aimed at B-ALL patients who had chemotherapy, but who had relapsed and were ineligible for a stem cell transplant.

The researchers used genetic engineering techniques to modify patients's own immune cells to recognise and kill their leukaemia cells.

Immune cells known as 'T-cells', which usually target bacteria and other pathogens, were modified to target tumour cells, by making the T-cells produce artificial laboratory-generated receptors, called chimeric antigen receptors (CARs).

These receptors were designed specifically to target a protein called CD19, known to be present on the surface of B-ALL cells.

Scientists tested the engineered T-cells in five adult relapsed B-ALL patients, and saw rapid improvement in their leukaemia.

One patient's disease become undetectable just eight days after treatment, while the other four patients achieved remission within 18-59 days.

The T-cell therapy allowed four of the patients to undergo a subsequent stem cell transplant.

The remaining patient experienced a relapse that coincided with the disappearance of the modified T-cells from their bloodstream.

The treatment now needs to be fined-tuned to have the right strength and persistence, and to minimise known side effects, the study's authors said.

Immunotherapy expert Professor Paul Moss, who runs the Birmingham Cancer Research UK Centre, said "The results of this small study are a good example of why many researchers are so excited about immunotherapy's potential.

"Although this treatment may not itself be a cure, it does seem to be able to produce remissions in patients whose B-cell ALL has relapsed.

Professor Moss said it was just one of several similar approaches being tested in clinical trials around the world, including in the UK.

"Although it's early days for these trials, the approach of modifying a patient's T-cells to attack their cancer is looking increasingly like one that will, in time, have a place alongside more traditional treatments like chemotherapy, radiotherapy and surgery," he added.

The New York researchers are currently planning an additional clinical trial, testing modified T-cells in patients with chronic lymphocytic leukaemia (CLL) who have become resistant to chemotherapy.

Source: CRUK