New immunotherapy for leukemia discovered

Acute lymphoblastic leukemia is the most common form of childhood leukemia, affecting approximately 70 children a year in Sweden. The disease is characterised by the unregulated growth of immature white blood cells, an essential component of the immune system, in the bone marrow and suppression of other healthy blood cells.

The condition is normally treated with chemotherapy or, in severe cases, bone marrow transplantation or immunotherapy, involving the genetic modification of the patient’s own T cells to make them attack another type of white blood cell called B cells. However, the therapy, known as CAR-T after the name of the genetically modified receptor, only works on patients with B-cell leukemia and not those with T-cell leukemia, which affects an estimated 15 to 20 percent of patients with acute lymphoblastic leukemia. Side effects can also occur, as healthy B cells can also be affected.

Spares healthy immune cells

Scientists at Karolinska Institutet, University of Oslo and Oslo University Hospital have now discovered another way to reprogramme the T cells so that they bind to a target expressed inside the cancer cells instead of on the cell surface. The new immunotherapy is focused on the enzyme terminal deoxynucleotidyl transferase (TdT), which is expressed in both T and B-cell leukemia, but only momentarily during the early development of healthy T and B cells. This means that the therapy has the potential to spare healthy T and B cells while eliminating leukemia cells of both the B and T cell type.

To date, the method, which has been developed by Professor Johanna Olweus at the University of Oslo, has been tested on mice with B-cell leukemia and on cell samples from patients with acute lymphoblastic leukemia of both cell types.