Scientists have figured out how to reprogram the blood of cancer patients to attack their leukaemia, and 19 of the 30 patients who received the treatment remain in complete remission.

A team of researchers led by immunotherapist Carl June from the University of Pennsylvania in the US has announced the results of a new treatment for leukaemia patients that turns their own blood cells against their disease.

The researchers chose to work with patients who were dealing with particularly aggressive cases of leukaemia. All of the participants in the study had cancers that had returned at least four times before.

According to Elizabeth Lopatto at the Verge, the treatment works by first having a patient’s T cells – a type of white blood cell that plays a crucial role in the body’s immune response – harvested through a blood transfusion process. These T cells are then engineered to seek out a particular protein called a B cell receptor, found on the surface of the patient’s B cells. B cells are another type of white blood cell that’s specifically targeted by leukaemia.

The patient’s altered T cells will then be transplanted back into their blood stream so they can start hunting B cell receptor proteins, and kill the leukaemia and the B cells they’re attached to.

Of course, this means that the patient’s entire supply of B cells will be wiped out by this treatment. Because the main role of B cells is to produce antibodies to fight anything that might threaten our bodies, including viruses and bacteria, the patients will be left extremely vulnerable until they can generate more. This is something that hospitals will need to be aware of if the treatment ends up being used more widely, but the benefit of this treatment is that it only has to be administered once for it to work.

According to the study, which was published in the New England Journal of Medicine, of the 30 children and adults that received the treatment, complete remission was achieved in 27 patients (90 percent). Remission was sustained past the six-month point in 19 of the 30 patients. One of the early success stories is a nine-year-old girl called Emily Whitehead, who started the treatment when she was six. She’s been cancer-free now for two years.

“This is unlike almost all cell and gene therapies in that it’s actually ahead of the schedule we set for ourselves when we first started treating patients,” June told Lopatto at the Verge. “We pinch ourselves because, you know, until recently we didn’t know if we got lucky or if it would last. Our initial patients are still in remission, so we know it’s durable and reproducible. That’s something that makes us excited every day.”

The team is now working on easing the side effects of the treatment, which include fever, nausea, muscle pain and difficulty breathing.