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'.