ImmunoGen, Inc. (Nasdaq: IMGN), a biotechnology company that develops novel anticancer therapeutics using its antibody-drug conjugate (ADC) technology, today announced that the European Commission has granted marketing approval for Kadcyla (trastuzumab emtansine; ado-trastuzumab emtansine in the US) in the European Union (EU). This event triggers a $5 million milestone payment to ImmunoGen. Kadcyla has been approved for the treatment of adult patients with HER2-positive, unresectable locally advanced or metastatic breast cancer who previously received Herceptin ® (trastuzumab) and a taxane, separately or in combination. Patients should have either: (1) received prior therapy for locally advanced or metastatic disease or (2) developed disease recurrence during or within six months of completing adjuvant therapy. As with the Kadcyla approvals that have been granted in the US, Japan, and other geographies, the approval in the EU is based on the findings in the EMILIA Phase III trial. In the EU and other international markets, the timing of the commercial availability of Kadcyla after approval can vary due to national differences in processes for establishing pricing/reimbursement, with some countries – including Germany – able to launch shortly after approval. “The European Commission’s decision is an important step toward Kadcyla becoming commercially available across the EU for patients with advanced HER2-positive breast cancer,” commented Daniel Junius, ImmunoGen President and CEO. About Kadcyla Kadcyla consists of Roche’s trastuzumab antibody with ImmunoGen’s DM1 cytotoxic agent attached using one of the Company’s engineered linkers. Roche has global development and commercialization rights for Kadcyla; ImmunoGen is entitled to receive royalties on product sales as well as specified milestone payments. Roche is conducting studies assessing Kadcyla for a number of additional potential uses. These include for the first-line treatment of HER2-positive metastatic breast cancer, for early stage HER2-positive breast cancer and for advanced HER2-positive gastric cancer. About ImmunoGen, Inc. ImmunoGen, Inc. develops targeted anticancer therapeutics. The Company’s ADC technology uses a tumor-targeting engineered antibody to deliver one of ImmunoGen's highly potent cancer-cell killing agents specifically to tumor cells. The most advanced compound with ImmunoGen’s ADC technology is Roche’s Kadcyla, which is marketed in the US by Genentech and starting to be commercialized internationally. Additional compounds are in clinical testing by ImmunoGen and through the Company’s partnerships with Amgen, Bayer HealthCare, Biotest and Sanofi. More information about ImmunoGen can be found at www.immunogen.com. Kadcyla ® and Herceptin ® are registered trademarks of Genentech, Inc., 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 risks related to reimbursement decisions, 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, 2013 and other reports filed with the Securities and Exchange Commission.