ImmunoGen, Inc. Announces FDA Approval of Kadcyla (Ado-Trastuzumab Emtansine; Also Known as T-DM1)

  ImmunoGen, Inc. Announces FDA Approval of Kadcyla (Ado-Trastuzumab
  Emtansine; Also Known as T-DM1)

  *Product demonstrates the power of ImmunoGen’s Targeted Antibody Payload
    (TAP) technology – first antibody-drug conjugate approved for a solid
    tumor indication.
  *Compound to be marketed in the US by Genentech, a member of the Roche
    Group, under the brand name Kadcyla™; was previously referred to as T-DM1.
  *FDA approval triggers $10.5 million milestone payment to ImmunoGen; paves
    way for royalties on commercial sales.
  *Three wholly owned ImmunoGen TAP compounds advancing in clinic along with
    six additional partner TAP compounds.

Business Wire

WALTHAM, Mass. -- February 22, 2013

ImmunoGen, Inc. (Nasdaq: IMGN), a biotechnology company that develops
anticancer therapeutics using its TAP technology, today announced that Roche
has reported that the U.S. Food and Drug Administration (FDA) has granted
marketing approval to Kadcyla for the treatment of people with HER2-positive
metastatic breast cancer who have received prior treatment with Herceptin^®
(trastuzumab) and a taxane chemotherapy.

“This is a big day for the patients with this cancer and for ImmunoGen,”
commented Daniel Junius, President and CEO. “In clinical testing, the findings
with Kadcyla in this patient population have been impressive, and we’re
delighted the product can now be used by practicing oncologists across the US.
In addition to its importance from a medical perspective, commercialization of
Kadcyla also marks the start of ImmunoGen earning royalty income.”

Mr. Junius continued, “The efficacy and tolerability seen with Kadcyla
underscores the transformative potential of our technology. Kadcyla is the
most advanced of ten compounds with our TAP technology already in the clinic,
with more in earlier stages of development. We are hopeful that in the future
many different types of cancers will be routinely treated with TAP compounds.”

Kadcyla has gained FDA approval for the treatment of people with HER2-positive
metastatic breast cancer who have received prior treatment with Herceptin and
a taxane chemotherapy. People should either:

  *Have already been treated for their metastatic cancer, or
  *Have had their early-stage cancer come back during or within six
    monthsafter they completed a course of treatment following surgery.

FDA approval of Kadcyla triggers a $10.5 million milestone payment to
ImmunoGen. The Company also earns royalties on commercial sales of Kadcyla.
Genentech is prepared to launch the product imminently.

“I am thrilled to see our concept of a trastuzumab-DM1 conjugate become a
reality today,” commented John Lambert, Ph.D., Executive Vice President and
Chief Scientific Officer. “We have always believed this product could make an
enormous difference for appropriate patients and are delighted to see it move
into the hands of practicing oncologists.”

Collaboration History

ImmunoGen conceived of the idea of attaching the Company’s DM1 maytansinoid
cell-killing agent to Genentech’s trastuzumab antibody to achieve a highly
effective, HER2-targeted anticancer agent. In 2000, Genentech licensed from
ImmunoGen exclusive rights to use the Company’s maytansinoid TAP technology to
develop anticancer products targeting HER2.

In 2006, Genentech advanced the compound that became known as Kadcyla into
clinical testing. Genentech has implemented a broad Kadcyla clinical
development program that has continued to expand subsequent to Genentech’s
acquisition by Roche.

Today, multiple Phase III trials are underway or planned evaluating Kadcyla
for a number of HER2-positive breast cancer indications. The compound also is
being evaluated for the treatment of HER2-positive gastric cancer.

Multiple TAP Compounds Advancing in the Clinic

In addition to Kadcyla, nine other compounds with the Company’s TAP technology
are in clinical testing for the treatment of an array of cancer types. Three
of these compounds are wholly owned by ImmunoGen:

  *IMGN901, in Phase II testing for the treatment of small-cell lung cancer;
  *IMGN853, in Phase I testing for the treatment of ovarian, lung, and other
    cancers that over-express folate receptor 1; and
  *IMGN529, in Phase I testing for the treatment of non-Hodgkin’s lymphoma.

The Company expects to advance a fourth TAP compound, IMGN289, into the clinic
in 2013. IMGN289 targets EGFR and is a potential treatment for cancers that
overexpress this target, including many head and neck and non-small cell lung

About ImmunoGen, Inc.

ImmunoGen, Inc. develops targeted anticancer therapeutics. The Company's TAP
technology uses a tumor-targeting monoclonal antibody to deliver one of
ImmunoGen's highly potent cancer-killing agents specifically to tumor cells.
Ten TAP compounds are now in clinical testing, of which three are wholly owned
by the Company. The most advanced compound using ImmunoGen's TAP technology,
Kadcyla (formerly T-DM1) has been approved for marketing in the US and is
undergoing regulatory review in Europe and Japan; it is being commercialized
in the US by Genentech, a member of the Roche Group. More information about
ImmunoGen can be found at

This press release includes forward-looking statements. For these statements,
ImmunoGen claims the protection of the safe harbor for forward-looking
statements provided by the Private Securities Litigation Reform Act of 1995.
It should be noted that there are risks and uncertainties related to the
development of novel anticancer products, including risks related to
preclinical and clinical studies, their timings and results. A review of these
risks can be found in ImmunoGen’s Annual Report on Form 10-K for the fiscal
year ended June 30, 2012 and other reports filed with the Securities and
Exchange Commission.

Herceptin® is a registered trademark of Genentech.
Kadcyla™ is a trademark of Genentech.


For Investors:
ImmunoGen, Inc.
Carol Hausner, 781-895-0600
Executive Director, Investor Relations and Corporate Communications
For Media:
The Yates Network
Barbara Yates, 781-258-6153
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