Stem cell transplant, a form of cell replacement therapy in which the diseased stem cells are replaced with healthy donor cells, is a potential curative therapy for patients with treatment-resistant blood cancers.

Progressive disease is a leading cause of death after stem cell transplant.

If a patient’s cancer continues to spread after transplant, the current standard treatment is to infuse the patient with unmanipulated donor white blood cells to fight the disease.

However, this procedure is often ineffective and increases risk of graft-versus-host disease (GVHD), a complication that occurs when the new cells attack the patient’s body.

Instead of unmanipulated white blood cells, researchers hypothesised that an infusion of genetically engineered donor T cells would eradicate progressive disease after stem cell transplant in patients with B-cell malignancies, which include types of leukaemia and non-Hodgkin lymphoma.

Researchers conducted a clinical trial in which donor T cells were engineered to express a chimeric antigen receptor (CAR). 

Their results have been presented by Dr James Kochenderfer at the ASH 2015 conference in Florida, USA.

CAR T cells are programmed to first recognise CD19, a protein on the surface of most B-cells, and then attack the targeted cell.

Patients who experienced resurgence of B-cell malignancies after stem cell transplant received a single infusion of CAR T cells obtained from each recipient’s stem cell donor.

No chemotherapy or other therapies were administered.

Eight of the 20 total patients obtained remissions, including six complete remissions and two partial remissions.

Response rates were highest for patients with acute lymphocytic leukaemia, with four of five patients achieving complete remission.

The longest ongoing complete remission is more than 30 months in a patient with chronic lymphocytic leukaemia.

No patient developed GVHD after infusion with CAR T cells.

The findings support the hypothesis that infusing anti-CD19 donor CAR T cells is a promising method for treating B-cell malignancies that emerge after stem cell transplant.

Source: ASH