FDA OKs Merck's Keytruda to Treat Cancers With Genetic Defects -- Update
May 23 2017 - 5:50PM
Dow Jones News
By Peter Loftus
The U.S. Food and Drug Administration on Tuesday approved Merck
& Co.'s Keytruda drug to treat tumors with a certain genetic
defect -- the first time the agency has cleared a cancer drug for a
use not tied to the site of a tumor.
The FDA approved Keytruda to treat tumors with genetic defects
known as "microsatellite instability" or "mismatch repair"
deficiencies, which are present in an estimated 4% of cancers.
Studies showed the drug shrank tumors in a significant number of
patients with colorectal and 14 other cancer types that had the
genetic defect.
The FDA's action -- its first "site-agnostic" approval for a
cancer drug -- signals a potential shift in cancer treatment. For
decades, cancer drugs have typically been approved and used to
treat site-specific tumors like those of the brain or breast.
With the site-agnostic approach, "instead of the classical way
of treating patients based on their tumor type, you treat based on
a genetic alteration," said Bert Vogelstein, co-director of the
Ludwig Center at the Johns Hopkins Kimmel Cancer Center. Dr.
Vogelstein's research linked mismatch-repair defects to cancer in
the 1990s.
The approach holds promise to improve treatment for patients
whose tumors have less common molecular traits, and who might not
benefit from standard treatments approved for specific tumor sites.
But it also requires additional tests of tumor samples to find
patients with the right genetic fit.
Tests for "mismatch repair" typically cost between $300 and
$600, according to Johns Hopkins. Dr. Vogelstein said the cost is
minor compared with other costs for cancer care.
Merck's Keytruda costs about $13,000 a month per patient. The
drug, which works by harnessing the body's immune system to attack
tumors, has previously been approved to treat several site-specific
tumors such as those of the skin and lung. Last year Keytruda
generated global sales of $1.4 billion.
Other drugs are being developed for "site-agnostic" uses in
tumors with particular genetic or molecular traits, regardless of
where they are in the body. Loxo Oncology Inc., of Stamford, Conn.,
is developing a drug targeting certain proteins that contribute to
tumor-cell growth in many cancers. If clinical studies are
successful the company may seek an FDA approval of the drug for use
in any tumor that has the proteins.
The new FDA approval allows Keytruda's use in tumors with the
genetic defect that have progressed following prior treatment with
other drugs, and have no satisfactory alternative treatment
options.
The FDA action was based on results from five clinical trials
totaling nearly 150 patients with the genetic defect. More than
half had colorectal cancer and the rest had 14 different cancer
types. Nearly 40% of patients experienced significant tumor
shrinkage, according to the FDA. Side effects included fatigue and
diarrhea. Because of how it works, Keytruda also can cause
immune-mediated side effects like colitis.
John Shinnick, 75 years old, of Barnegat, N.J., was diagnosed
with pancreatic cancer in April 2015. He underwent surgery followed
by chemotherapy and radiation, but the cancer began to advance
again last year. A test determined that his tumor had
microsatellite instability, and in June 2016 he enrolled in a
clinical trial of Keytruda at Hopkins. He said the drug has been
effective for him, and he is due to continue taking it until June
2018.
"I'm ecstatic with the results," he said.
Write to Peter Loftus at peter.loftus@wsj.com
(END) Dow Jones Newswires
May 23, 2017 18:35 ET (22:35 GMT)
Copyright (c) 2017 Dow Jones & Company, Inc.
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