Blood cancer sent into remission with gene therapy

Gene therapy trials using engineered immune cells have shown considerable progress in treating blood disorders, according to findings presented at the American Society of Hematology's annual meeting.

Several studies reported their results on using 'chimeric antigen receptor (CAR) cell engineering' to treat blood cancers. In this method, T-cells- one of several types of immune cell - are taken from a patient and genetically modified to specifically recognise proteins on cancer cells. Once reintroduced to the patient, these engineered cells are now able to 'seek and destroy' cancer cells.

'It's really exciting. You can take a cell that belongs to a patient and engineer it to be an attack cell', Dr Janis Abkowitz, president of the American Society of Hematology, told the Associated Press.

Many groups of researchers have used this method over several years to treat more than 120 patients with different forms of blood cancer. It was effective in both adults and children, many with advanced cancers that could no longer be treated by other means.

The largest numbers of patients have been treated in trials at the Children's Hospital of Philadelphia and  the University of Pennsylvania. In one study, all five adults and 19 of 22 children with treatment-resistant acute lymphocytic leukaemia (ALL) achieved complete remission, although six have since relapsed.

Author Dr Stephan Grupp of the Children's Hospital of Philadelphia said: 'Our results serve as another important milestone in demonstrating the potential of this treatment for patients who truly have no other therapeutic options'.

The team hope to get federal approval for the treatment as early as 2016.

In an unrelated preliminary study presented at the same meeting, researchers at Dana Farber/Boston Children's Cancer and Blood Disorders Center used engineered immune cells to treat children suffering from X-Linked Severe Combined Immunodeficiency (SCID) — a rare disease in which patients lack a functional immune system.

SCID arises as patients have an inactive version of the IL2RG gene, meaning that haematopoietic (blood- forming) stem cells are unable to develop into an immune system. Researchers took bone marrow stem cells from nine patients and used a viral vector to insert a normal copy of IL2RG into the DNA. Once returned to the patients, these cells are able to divide and restore the immune system.

The vector used in this study has been modified so that it does not activate other genes that can lead to leukaemia — something that occurred in a quarter of participants in a previous trial for SCID.

Almost three years after being given this new therapy, seven boys are showing signs of producing healthy T cells.

Author Dr Sung Yun Pai stressed the importance of closely monitoring the children and said: 'We have preliminary evidence that using this new vector approach is just as effective but may eliminate the long-term risk of leukaemia in these children'.

One important similarity between all of these studies is the use of the patients' own cells to develop the therapy. This avoids waiting for matched donors and reduces the risk of graft-versus-host disease — a severe complication where donor immune cells also attack healthy patient's cells as foreign tissue.

Despite these promising results, Dr Laurence Cooper of The University of Texas (who was not involved in the studies), said a challenge still to address is 'why some patients benefit and others have less durable responses'.