Of seven patients available to be evaluated
following a 28-day cycle of treatment with the drug, AG-221, six had
what researchers deemed objective responses to the medicine.
Three of them achieved complete remission and two achieved complete
remission with incomplete platelet recovery, meaning that the
leukemia had exited their bone marrow but the blood platelet count
had not yet returned to normal levels.
"I'm very excited about what has happened with those patients so far
who have responded," the study's lead investigator, Dr. Eytan Stein
of Memorial Sloan Kettering Cancer Center in New York, said in a
AML, the most common type of acute leukemia in adults, is a cancer
of the blood and bone marrow that progresses quickly if left
untreated. AG-221 targets a gene mutation that is present in 10
percent to 15 percent of AML patients, Stein explained.
Stein, who presented the results at the American Association for
Cancer Research (AACR) meeting in San Diego, cautioned that this was
very preliminary data.
"If the results are confirmed (in upcoming larger trials) that would
be a remarkably exciting result," Stein said of the first-in-class
Patients in the study had AML that had progressed after, or failed
to respond to, up to four other therapies.
They all had the specific genetic mutation in the leukemic cells
that the drug is designed to impact, called isocitrate
dehydrogenase-2, or IDH2. The treatment led to substantially lower
levels of a cancer metabolite in the blood called 2HG that
researchers believe reprograms white blood cells, stripping their
ability to become infection fighters.
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Stein noted that in the tiny group of patients there were no
observable side effects that appear related to the drug itself,
"which is very different from chemotherapy."
Patients in the study received either 30 milligrams or 50 mg of
AG-221 twice a day. Another arm of the trial was studying two higher
doses, but that data was not yet available.
Stein said researchers were not expecting the impact seen with the
lowest doses in the first handful of patients.
"We were actually kind of surprised that at the first dose level
we're seeing dramatic clinical activity. That usually doesn't
happen," he said.
(Reporting by Bill Berkrot; editing by Raissa Kasolowsky)
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