For Adults with Leukaemia,Immune-system therapy shows some hope

An experimental therapy shows that cancer patients' own immune cells to recognize an often-deadly form of leukaemia has shrunk tumours and sent the cancer into remission in adults, for the first time, though it has worked in children earlier.

The experimental therapy targeted acute lymphoblastic leukaemia (ALL), a blood-cell cancer that often proves resistant to chemotherapy and can kill in mere weeks. It is more common in children but especially deadly when it occurs in adults.

Although current treatments cure an estimated 80 percent to 90 percent of children with ALL, they are effective in only 30 percent or fewer of adult cases.

Adults whose ALL has returned after being temporarily beaten back with chemotherapy, have a dismal prognosis.

The study hopes that harnessing the immune system to destroy tumours could turn back many cancers.

In the new study, scientists started with their patients' T cells, a form of white blood cell. These foot soldiers of the immune system make a beeline for both viruses and cancer cells, which sport molecules that act like homing beacons to attract the T cells.

Normal T cells find and attack only invaders studded with homing beacons they're able to recognize. That's why the immune system does not sweep out all cancers, let alone viruses such as HIV: T cells have not been trained to detect their beacons.

The scientists therefore re-trained the T cells to do so.

After extracting T cells from patients with ALL, a process that takes a few hours, the scientists mixed them with a harmless virus that inserted genes for a three-part molecule: one part that trains T cells to recognize homing beacons on the leukaemia cells, called CD19; one part that instructs T cells to kill any such cells they find; and one part that makes T cells survive longer than usual.

After 10 to 12 days, the T cells were now genetically-engineered to detect those beacons. The cells were then returned to patients. The T cells are living drugs. They see the CD19, they kill the cancer cells, and they persist in the body.

One patient  developed a 105 degree fever as the T cells ignited what's called a cytokine storm, in which cytokines - hormones - are produced in vast quantities, leading to plummeting blood pressure and high fever. A second patient also suffered this cytokine storm, but they're treated with steroids successfully.