Daniel Junius to Retire as President and CEO of ImmunoGen, Inc.

– Successor Expected to be Announced Shortly –

ImmunoGen, Inc. (Nasdaq: IMGN) a biotechnology company that develops targeted anticancer therapeutics using its antibody-drug conjugate (ADC) technology, today announced that Daniel Junius, age 63, has decided to retire from his positions of President and CEO of the Company. This will become effective when his successor joins ImmunoGen. Mr. Junius has been the Company’s CEO since January 2009. Following his retirement, Mr. Junius will continue to serve on ImmunoGen’s Board of Directors.

In September 2015, Mr. Junius discussed with ImmunoGen’s Board that he was considering retiring by the end of the Company’s fiscal year in June if an appropriate successor could be found within that timeframe. The Board then formed a search committee, retained an executive recruitment firm, and began formal succession planning. It is currently anticipated that a successor to Mr. Junius will be announced shortly.

“Dan has taken ImmunoGen from being a research company with a validated technology to one with strong research, development, clinical and manufacturing functions that is advancing a rich pipeline of product candidates driven by an expanding technology portfolio,” commented Stephen McCluski, Chairman of the Board. “The Board is grateful to Dan for his extensive contributions to ImmunoGen and his commitment to making a difference for patients with cancer.”

“For over seven years, I have had the privilege of leading a company full of smart, team-oriented employees committed to developing better treatments for cancer,” noted Mr. Junius. “I believe ImmunoGen is in a strong position today and look forward to its continued advancement under the next CEO.”

About ImmunoGen, Inc.

ImmunoGen is a clinical-stage biotechnology company that develops targeted anticancer therapeutics using its proprietary ADC technology. The Company’s lead product candidate, mirvetuximab soravtansine, is in Phase 2 testing for the treatment of folate receptor α-positive ovarian cancer. ImmunoGen's ADC technology is used in Roche's marketed product, Kadcyla®, and in programs in development by partners Amgen, Bayer, Biotest, CytomX, Lilly, Novartis, Sanofi and Takeda. More information about the Company can be found at www.immunogen.com.

Kadcyla® is a registered trademark of Genentech, a member of the Roche Group.

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