Subsequent Events	9 Months Ended
Sep. 30, 2021
Subsequent Events
Subsequent Events	J.Subsequent Events Debiopharm In May 2017, Debiopharm International S.A. (Debiopharm) acquired the Company’s IMGN529 program, a clinical-stage anti-CD37 ADC for the treatment of patients with B-cell malignancies, such as non-Hodgkin lymphomas (NHL). Under the terms of the Exclusive License and Asset Purchase agreement, the Company received a $25.0 million upfront payment for specified assets related to IMGN529 and an exclusive license to additional intellectual property necessary or useful for Debiopharm to develop and commercialize IMGN529. The Company also received a $5.0 million milestone payment upon transfer of ImmunoGen technologies related to the program. In October 2021, the Company and Debiopharm amended their agreement, pursuant to which the Company is entitled to receive a percentage of all payments generated from future sublicenses of naratuximab emtansine, including upfront fees, milestones, and royalties, up to an aggregate of $30.0 million and in lieu of a potential $25.0 million development milestone payment under the original agreement. License Commitment In October 2021, as a result of a dispute regarding terms of a 2012 license agreement with a contract manufacturing vendor, the Company and vendor amended their agreement to replace certain annual fees and potential royalties payable by the Company on future sales of mirvetuximab with capped development and sales-based milestone payments totaling $18.0 million, of which $3.0 million was recorded as research and development expense during the nine months ended September 30, 2021. The Company has evaluated all other events or transactions that occurred after September 30, 2021, up through the date the Company issued these financial statements. The Company did not have any other material recognized or unrecognized subsequent events during this period.

Subsequent Events

9 Months Ended

Sep. 30, 2021

J.Subsequent Events

Debiopharm

In May 2017, Debiopharm International S.A. (Debiopharm) acquired the Company’s IMGN529 program, a clinical-stage anti-CD37 ADC for the treatment of patients with B-cell malignancies, such as non-Hodgkin lymphomas (NHL). Under the terms of the Exclusive License and Asset Purchase agreement, the Company received a $25.0 million upfront payment for specified assets related to IMGN529 and an exclusive license to additional intellectual property necessary or useful for Debiopharm to develop and commercialize IMGN529. The Company also received a $5.0 million milestone payment upon transfer of ImmunoGen technologies related to the program.

In October 2021, the Company and Debiopharm amended their agreement, pursuant to which the Company is entitled to receive a percentage of all payments generated from future sublicenses of naratuximab emtansine, including upfront fees, milestones, and royalties, up to an aggregate of $30.0 million and in lieu of a potential $25.0 million development milestone payment under the original agreement.

License Commitment

In October 2021, as a result of a dispute regarding terms of a 2012 license agreement with a contract manufacturing vendor, the Company and vendor amended their agreement to replace certain annual fees and potential royalties payable by the Company on future sales of mirvetuximab with capped development and sales-based milestone payments totaling $18.0 million, of which $3.0 million was recorded as research and development expense during the nine months ended September 30, 2021.

The Company has evaluated all other events or transactions that occurred after September 30, 2021, up through the date the Company issued these financial statements. The Company did not have any other material recognized or unrecognized subsequent events during this period.