ImmunoGen, Inc. Announces Preclinical Findings with its IMGN289 Product Candidate for the Treatment of EGFR-Overexpressing

  ImmunoGen, Inc. Announces Preclinical Findings with its IMGN289 Product
  Candidate for the Treatment of EGFR-Overexpressing Cancers

  *Novel antibody-drug conjugate (ADC) can kill Epidermal Growth Factor
    Receptor (EGFR)-overexpressing cancer cells via two mechanisms –
    EGFR-inhibition and direct cell-killing.
  *In preclinical testing, IMGN289 was highly active against
    EGFR-overexpressing cancer cells, including those not dependent on EGFR
    signaling and those resistant to tyrosine kinase inhibitors (TKIs).
  *ImmunoGen is on track to submit the IND for IMGN289 in mid-2013.

Business Wire

WALTHAM, Mass. -- April 10, 2013

ImmunoGen, Inc. (Nasdaq: IMGN), a biotechnology company that develops targeted
anticancer therapeutics using its Targeted Antibody Payload (TAP) technology,
disclosed for the first time today preclinical data for its EGFR-targeting
ADC, IMGN289. The data are being presented at the American Association for
Cancer Research (AACR) Annual Meeting 2013 in Washington, DC (abstracts# 5463,
5467, and 5483). ImmunoGen developed IMGN289 to treat EGFR-overexpressing
cancers, which include many cases of squamous cell carcinoma of the head and
neck (SCCHN) and non-small cell lung cancer (NSCLC), and expects to begin
clinical testing of the compound later this year.

IMGN289 contains an EGFR-binding antibody that can achieve significant
inhibition of EGFR-signaling, an important mechanism of action for
EGFR-overexpressing cancers being fueled by EGFR. In studies reported today,
the antibody in IMGN289 was shown to provide potency comparable to or better
than cetuximab (Erbitux^®) in preclinical models of SCCHN and NSCLC.

An ADC, IMGN289 also contains the Company’s potent DM1 cancer cell-killing
agent, which is attached to the EGFR-binding antibody using ImmunoGen’s SMCC
thioether linker. The linker/cell-killing agent format of IMGN289 is the same
as that of ado-trastuzumab emtansine (Kadcyla™) and IMGN529 – other TAP
compounds that also contain antibodies with anticancer properties.

The DM1 enables IMGN289 to kill EGFR-overexpressing cancers by a second method
that is independent of the sensitivity of these cells to EGFR inhibition. In
preclinical models of EGFR-overexpressing cancers reported today, IMGN289 was
highly active against NSCLC not dependent on EGFR signaling and against NSCLC
with acquired resistance to TKIs; in SCCHN models responsive to EGFR, IMGN289
was significantly more active than cetuximab.

“IMGN289 represents a highly promising new therapy for EGFR-overexpressing
cancers,” commented John Lambert, Ph.D., Executive Vice President and Chief
Scientific Officer. “Its dual mechanisms of action – ability to kill cancers
through EGFR inhibition and through direct cell killing – should enable
IMGN289 to be more effective than current EGFR-targeting agents against
EGFR-overexpressing cancers, both those that are responsive to EGFR inhibition
and those that are not.”

Dr. Lambert continued, “In developing IMGN289, our scientists identified a new
class of EGFR-binding antibody – one that, in preclinical testing, achieves
potent EGFR inhibition, but with less skin toxicity than marketed anti-EGFR
antibodies. We expect IMGN289, comprising our TAP technology and this
antibody, to provide significant efficacy benefits in the clinic with a
favorable tolerability profile.”

IMGN289 is on track to become the Company’s fourth wholly owned clinical-stage
compound. The Company is preparing to submit the IMGN289 IND in mid-2013 and
to begin IMGN289 clinical testing later this year.

About Squamous Cell Carcinoma of the Head and Neck (SCCHN)

Approximately 52,000 people in the US were diagnosed with head and neck
cancers last year.^1 These cancers typically originate in the squamous cells
of the mucosal linings of the (e.g., of the nose, mouth, or throat), and thus
are categorized as squamous cell carcinomas of the head and neck.^1 Research
conducted at ImmunoGen has found that EGFR is overexpressed on virtually all
cases of SCCHN, and that it is almost always highly overexpressed.^2

About Non-Small Cell Lung Cancer (NSCLC)

In 2012, approximately 194,000 patients in the US were diagnosed with NSCLC,
which accounts for about 85% of all lung cancer diagnoses.^3 Research
conducted at ImmunoGen has found that EGFR is highly overexpressed on many of
the cases of the most common subtypes, adenocarcinoma, squamous cell
carcinoma, and large cell carcinoma.^4

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-cell killing agents specifically to tumor
cells. Ten TAP compounds are now in the clinic, 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


^1 National Cancer Institute (version reviewed 2/1/2013), Fact Sheets: Head &
Neck Cancers,
^2 Ponte et al., AACR 2013, abstract #5483
^3 American Cancer Society (2013), Cancer Facts & Figures
^4 Chittenden et al., AACR 2013, abstract #5467

Erbitux^® is a registered trademark of ImClone LLC, a wholly-owned subsidiary
of Eli Lilly and Company.
Kadcyla™ is a trademark of Genentech, a member of the Roche Group.

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 IMGN289, 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.


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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