ImmunoGen, Inc. Announces IMGN901 Clinical Data Presented at ASH

  ImmunoGen, Inc. Announces IMGN901 Clinical Data Presented at ASH

 Benefit seen in both lenalidomide-naïve and lenalidomide-refractory multiple

Business Wire

WALTHAM, Mass. -- December 10, 2012

ImmunoGen, Inc. (NASDAQ: IMGN), a biotechnology company that develops
anticancer therapeutics using its Targeted Antibody Payload (TAP) technology
and antibody expertise, today announced the presentation of new clinical data
with the Company’s targeted anticancer compound, IMGN901. The data were from a
Phase I clinical study assessing IMGN901 used in combination with lenalidomide
(Revlimid^®) and dexamethasone to treat patients with CD56-expressing relapsed
or relapsed/refractory multiple myeloma. The data were reported in an oral
presentation (abstract #728) at the 54^th American Society of Hematology (ASH)
Annual Meeting and Exposition in Atlanta, Georgia.

“The level and duration of the responses to the study regimen confirm the
activity seen with IMGN901 in earlier trials – where it was evaluated as
single-agent therapy – and support the further development of IMGN901 as a
treatment for CD56-expressing cancers,” commented James O’Leary, MD, Vice
President and Chief Medical Officer.

The trial was designed to assess IMGN901, given weekly for three weeks in a
4-week cycle, used in combination with lenalidomide and dexamethasone. As
reported previously, a dose of 75mg/m^2/week was established for IMGN901 in
the dose-finding phase of the trial for evaluation in its expansion phase.
Patients received lenalidomide and dexamethasone at standard doses (25 mg
daily for 21 days in a 4-week cycle and 40 mg weekly for four weeks,

A total of 44 patients with relapsed or relapsed/refractory multiple myeloma
were enrolled in the trial. Most of the patients had previously received
bortezomib (Velcade®) (91%) and/or lenalidomide (59%), and many had received
prior thalidomide (46%). Many patients also had received prior alkylating
agents (64%) and/or anthracyclines (41%). About half of the patients had prior
stem cell transplant.

The response findings reported for the 39 efficacy-evaluable patients

  *Sixty-four percent of patients had a clinical response (minimal response,
    MR, or better)to treatment and another 31% had stable disease (SD).
    Thirty-one percent of these 39 patients had a VGPR (very good partial
    response) or better, with VGPR being a category established by the
    International Myeloma Working Group to distinguish patients with excellent
    responses that may have outcomes comparable to patients with complete
    responses (CR).^1

  *Among the 16 lenalidomide-naïve patients, 14 (88%) had a partial response
    or better to treatment, with the remaining two patients having stable
  *Among the 23 patients who had received prior lenalidomide (including
    lenalidomide-refractory patients), 48% had a clinical response to
    treatment – three (13%) had a VGPR, five (22%) had a PR, and three (13%)
    had a MR. Another 10 (44%) of these patients had SD. Among the five
    lenalidomide-refractory patients, one had a VGPR, one had a PR, two had
    MRs, and one had SD.

  *Among the 13 patients with known poor prognostic mutations, 9 (69%) had a
    clinical response. The other four patients had SD.

Of particular note, median time-to-progression was 7.7 months with the study
regimen (IMGN901 at 75 mg/m^2).

The safety profile was consistent with the previously observed profiles of the
drugs. The most common adverse events associated with the study regimen
(occurring in >25% patients) consisted of Grade 1/2 peripheral neuropathy,
fatigue, neutropenia, thrombocytopenia, nausea and diarrhea. Of note, the
majority of patients entering the trial had Grade 1 peripheral neuropathy from
prior therapy.

About IMGN901

IMGN901, also known as lorvotuzumab mertansine, is wholly owned by ImmunoGen
and consists of the Company's DM1 cancer-cell killing agent attached to its
lorvotuzumab CD56-binding antibody using one of the Company’s engineered

Encouraging findings have been reported with IMGN901 in initial evaluations
for the treatment of multiple myeloma, small-cell lung cancer (SCLC), and
Merkel cell carcinoma (MCC). IMGN901 is in Phase II testing, in the NORTH
trial, for front-line treatment of SCLC. It has been granted orphan drug
designation for multiple myeloma, SCLC, and MCC in the US and Europe.

About ImmunoGen, Inc.

ImmunoGen, Inc. develops targeted anticancer therapeutics using its TAP
technology together with the Company’s expertise in monoclonal antibodies and
tumor biology. A TAP compound uses a tumor-targeting monoclonal antibody to
deliver one of ImmunoGen's purpose-developed cancer-killing agents
specifically to tumor cells. Ten TAP compounds are now in clinical testing, of
which three are wholly owned by the Company. Marketing applications for
trastuzumab emtansine (T-DM1), the most advanced compound using ImmunoGen's
TAP technology, are under review in the US and Europe. Roche is developing
this compound globally under an agreement between ImmunoGen and Genentech, a
member of the Roche Group. More information about ImmunoGen can be found at

Revlimid^® is a registered trademark of Celgene Corporation.
Velcade® is a registered trademark of Millennium Pharmaceuticals, Inc.

^1Durie et al. Blood. 2006

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 IMGN901, 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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