F.D.A. Approves Breast Cancer
Drug
By ANDREW POLLACK
The Food and Drug Administration on Friday approved a
new type of drug that combines the widely used breast cancer medicine Herceptin
with a powerful toxin to more effectively kill cancer cells while potentially
reducing side effects.
The drug, which will be called Kadcyla but was known
as T-DM1 during its development, extended the median survival of women with
advanced breast cancer by nearly half a year in a clinical trial.
Genentech, which developed the drug, said it would
cost about $9,800 a month, or $94,000 for a typical course of treatment. That is
about twice the price of Herceptin itself, which is also made by Genentech, but
it is similar to the price of some other new cancer drugs. It is approved for
patients with HER2-positive breast cancer, about 20 percent of cases.
Kadcyla is one of the first successful examples of a
new class of drug that link toxins to proteins known as monoclonal antibodies.
The antibodies latch onto tumors and deliver the toxic payload. Because the
toxin is not activated until it reaches the tumor, some side effects are
avoided.
Such medicines, known as antibody-drug conjugates,
are
a hot area for cancer drug developers, with around two dozen such drugs in
clinical trials. Another antibody-drug conjugate, Adcetris, developed by Seattle
Genetics, was approved in 2011 as a treatment for two rare types of lymphoma.
The linker and toxin used in Kadcyla was developed by
ImmunoGen, based in Waltham, Mass., which will receive royalties on sales of the
drug. This is the first approved product for ImmunoGen, which has been working
on antibody-drug conjugates for three decades.
The main clinical trial leading to approval of Kadcyla
involved 991 patients with metastatic breast cancer that was worsening despite
treatment with Herceptin and a taxane chemotherapy drug, such as paclitaxel.
Half the women were given infusions of Kadcyla and the other half took two pills
now commonly used for such patients: Tykerb, also known as lapatinib, and
Xeloda, also known as capecitabine.
The patients getting Kadcyla lived a median of 30.9
months, compared with 25.1 months for those getting the two pills. The median
time before the disease worsened, a measure known as progression-free survival,
was 9.6 months for those getting Kadcyla, compared with 6.4 months for those
getting the other drugs.
While having greater efficacy, Kadcyla also had fewer
side effects. About 43 percent of patients on Kadcyla had serious side effects
compared with 59 percent for those getting the two pills.
Still, the label of Kadcyla has a warning saying the
drug can cause liver toxicity, heart toxicity and death. It also can cause
serious birth defects or fetal death, so women of childbearing age taking the
drug are urged to use contraception.
Herceptin, also known as trastuzumab, binds to a
protein on the surface of breast cancer cells called HER2. Since Kadcyla
incorporates Herceptin, it too is approved only for the roughly 20 percent of
breast cancer cases with an overabundance of HER2.
Kadcyla’s approval is for use after a patient has
already failed to respond to Herceptin and a taxane. But Roche, the Swiss
company that owns Genentech, is already testing it for use as an initial
treatment for metastatic cancer. It is also testing it in combination with
Perjeta, another of its drugs for HER2-positive breast cancer, which was
approved last June.
Roche executives say they hope that Kadcyla, along
with Perjeta, will make Herceptin somewhat obsolete by the time it could face
competition from cheaper biosimilars, which are similar to generics. Roche says
the United States patent on Herceptin expires in 2019.
Herceptin had global sales of 5.9 billion Swiss francs
($6.3 billion at current exchange rates) in 2012. It was the world’s
best-selling drug used only for cancer in 2012.
Genentech tried to win approval for T-DM1 in 2010 as a
treatment for breast cancer patients who had run out of options, based on a
small trial without a control group. But the F.D.A. turned down the application,
angering some patients and patient advocates.
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