UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington,  D.C. 20549 

FORM 8-K

CURRENT REPORT

PURSUANT TO SECTION 13 OR 15(d)

OF THE SECURITIES EXCHANGE ACT OF 1934

Date of Report (Date of earliest event reported): December 18, 2020

ImmunoGen, Inc.

(Exact name of registrant as specified in its charter)

830 Winter Street, Waltham, MA 02451

(Address of principal executive offices)   (Zip Code)

Registrant's telephone number, including area code: (781) 895-0600

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

¨   Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

¨   Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

¨   Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

¨   Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company ¨

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ¨

Item 8.01 - Other Events.

In connection with the filing of a registration statement on Form S-3 with the Securities and Exchange Commission (the “SEC”), ImmunoGen, Inc. (the “Company”) is updating the risk factor disclosure contained in its prior public filings, including the risk factor disclosure included under the heading “Risk Factors” included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019, filed with the SEC on March 11, 2020, principally as a result of amendments to Item 105 of Regulation S-K adopted by the SEC which became effective on November 9, 2020. The updated risk factor disclosure is filed herewith as Exhibit 99.1 to the Current Report on Form 8-K and is incorporated herein by reference.

Item 9.01 - Financial Statements and Exhibits.

(d)  Exhibits.

SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.