An experimental therapy that tweaks cancer patients' own
immune cells to recognise an often-deadly form of leukaemia has shrunk tumours
and sent the cancer into remission in adults, according to a US study published
Although a similar immune-system approach has shown promise
in children with this cancer as well as in adults with a related form of leukaemia, it is the first time this particular therapy has worked in adults.
Scientists said the finding, which was based on a study of
five adults, had "life-saving potential." The study was published in
the journal Science Translational Medicine. The experimental therapy targeted
acute lymphoblastic leukaemia (ALL), a blood-cell cancer that often proves
resistant to chemotherapy and can kill in mere weeks.
How the study was
It is more common in children but especially deadly when it
occurs in adults. Although current treatments cure an estimated 80% to 90% of
children with ALL, they are effective in only 30% or fewer of adult cases, said
Dr Michel Sadelain of Memorial Sloan-Kettering Cancer Center in New York,
co-leader of the study.
Adults whose ALL has returned after being temporarily beaten
back with chemotherapy, Sadelain and his colleagues wrote, "have a dismal
prognosis."The study adds to the evidence that harnessing the immune
system to destroy tumours could turn back many cancers.
For instance, a therapeutic vaccine against deadly melanoma,
called Yervoy and manufactured by Bristol-Myers Squibb, was approved in 2011,
and scores of other immune-system-based drugs to treat cancer are in the
The costs of immune-based
IMS Health has estimated that global sales of immune-based
oncology drugs could reach $75 billion by 2015.In the new study, scientists
started with their patients' T cells, a form of white blood cell. These foot
soldiers of the immune system make a beeline for both viruses and cancer cells,
which sport molecules that act like homing beacons to attract the T cells.
Normal T cells find and attack only invaders studded with
homing beacons they're able to recognize. That's why the immune system does not
sweep out all cancers, let alone viruses such as HIV: T cells have not been
trained to detect their beacons.
The scientists therefore re-trained the T cells to do so. After
extracting T cells from patients with ALL, a process that takes a few hours,
the scientists mixed them with a harmless virus that inserted genes for a
three-part molecule: one part that trains T cells to recognise homing beacons
on the leukaemia cells, called CD19; one part that instructs T cells to kill any
such cells they find; and one part that makes T cells survive longer than
What the results in
After 10 to 12 days, the T cells were now
genetically-engineered to detect those beacons. The cells were then returned to
their five patients, aged 23, 58, 56, 59 and 66."The T cells are living
drugs," said Sadelain. "They see the CD19, they kill the cancer
cells, and they persist in the body."Four of the patients' leukaemia became
undetectable in 18 to 59 days. One patient achieved the remission eight days
after treatment - a dramatic result considering that several of the patients
had bone marrow "chock full of leukaemia," Sadelain said.
But the treatment wasn't always easy on patients. After one
got back his genetically-engineered T cells, he developed a 105 degree fever as
the T cells ignited what's called a cytokine storm, in which cytokines -
hormones - are produced in vast quantities, leading to plummeting blood
pressure and spiking fever. A second patient also suffered this cytokine storm,
but in both cases it was managed with steroids.
The researchers are raising funds for a larger study, with
50 patients or more, at Sloan-Kettering as well as other cancer centers,
including the Dana-Farber Cancer Institute in Boston.
They already have successfully treated three additional
patients beyond the five described in the paper, Dr Renier Brentjens of
Sloan-Kettering said, and suspect they might get even better results if they
began treatment earlier in the disease.