New variation of CAR T-cell therapy holds promise for leukemia

Scientists at Stanford University have identified a molecule that can be targeted to cure leukaemia - the most common form of cancer in childhood.

The therapy is similar to but distinct from CD19-targeted chimeric antigen receptor T-cell therapy, or CAR T-cell therapy, in which a patient's T cells are genetically modified to target a molecule called CD19 on the surface of the cancer cells.

This therapy was recently approved by the US Food and Drug Administration (FDA) for the treatment of some types of blood cancers, according to a study published in the journal Nature Medicine.

B-cell acute lymphoblastic leukemia is the most common childhood cancer. Usually, it can be treated with chemotherapy, but sometimes patients suffer relapses or don't improve after treatments such as chemotherapy or bone marrow transplants.

Cell therapy is a new approach to tackle these difficult forms of cancer. The first such drug, Kymriah, developed by Novartis, was approved by the US Food and Drug Administration earlier this year for the treatment of lymphoblastic leukemia in cases where other types of treatment fail.

The modification introduces a chimeric antigen receptor that targets a specific protein molecule found on the surface of cancer cells - CD19 - in leukemia and lymphoma. But even patients who have undergone this therapy suffer recurrences. Now, researchers from Stanford University School of Medicine and the National Cancer Institute designed a new CAR T-cell therapy that targets a different surface molecule, CD22.

The new therapy involves extracting millions of a patient's T-cells and genetically modifying them to destroy malignant cancer cells before returning them. The therapy genetically modifies a patient's T cells to target a different molecule called CD22, scientists at the Stanford University in the US said.

The approach is helpful because the cancer cells of some patients who undergo CD19-targeted CAR T-cell therapy stop expressing the CD19 molecule on their cell surfaces.

CAR T-cell therapy relies on a patient's own T cells – a type of immune cell that can be a powerful killing machine.

Fifteen of the 21 patients in the study had previously either relapsed or failed to respond to anti-CD19 CAR T-cell treatment.

At the lowest dose level, one in six patients achieved complete remission after treatment with the anti-CD22 CAR T cells.

However, when the researchers escalated the dose to the next level in the study, 11 of 15 patients, or 73 per cent, entered remission.

They hope that targeting CD19 and CD22 simultaneously may result in a powerful therapy - one that cancer cells are unable to evade