WALTHAM, Mass.--(BUSINESS WIRE)--ImmunoGen, Inc. (NASDAQ: IMGN) today announced its intention to offer and sell to the initial purchasers, subject to market and other conditions, $100 million aggregate principal amount of convertible senior notes due 2021 in a private placement. The Notes will be offered by the initial purchasers only to qualified institutional buyers pursuant to Rule 144A under the Securities Act of 1933, as amended. The sale is expected to close on June 20, 2016. ImmunoGen also intends to grant the initial purchasers of the Notes an option, exercisable for 30 days, to purchase up to an additional $15 million aggregate principal amount of the Notes on the same terms and conditions to cover over-allotments, if any.

About ImmunoGen

ImmunoGen is a clinical-stage biotechnology company that develops targeted cancer therapeutics using its proprietary antibody-drug conjugate (“ADC”) technology. ImmunoGen’s lead product candidate, mirvetuximab soravtansine, is being advanced to Phase 3 testing for FR?-positive platinum-resistant ovarian cancer, and is also in Phase 1b/2 testing in combination regimens for earlier-stage disease. ImmunoGen’s ADC technology is used in Roche's marketed product, Kadcyla®, and in two other clinical-stage ImmunoGen product candidates, and in programs in development by partners Amgen, Bayer, Biotest, CytomX, Lilly, Novartis, Sanofi and Takeda.