Sec Form 4 Filing - Thackray Helen M. @ ImmunoGen, Inc. - 2024-02-12

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person Thackray Helen M. 2. Issuer Name and Ticker or Trading Symbol ImmunoGen, Inc. [ IMGN] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director _____ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O IMMUNOGEN, INC., 830 WINTER STREET 3. Date of Earliest Transaction (MM/DD/YY) 02/12/2024 (Street) WALTHAM, MA02451 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 02/12/2024 D( 1 ) 3,074 D 0 D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Restricted Stock Unit $ 0 ( 2 ) 02/12/2024 D( 2 ) 13,090 ( 2 ) ( 2 ) Common Stock 13,090 ( 2 ) 0 D Deferred Share Unit $ 0 ( 3 ) 02/12/2024 D( 3 ) 40,932 ( 3 ) ( 3 ) Common Stock 40,932 ( 3 ) 0 D Stock Option (Right to Buy) $ 5.97 02/12/2024 D( 4 ) 44,000 ( 4 ) 09/22/2031 Common Stock 44,000 ( 4 ) 0 D Stock Option (Right to Buy) $ 3.37 02/12/2024 D( 4 ) 32,066 ( 4 ) 06/15/2032 Common Stock 32,066 ( 4 ) 0 D Stock Option (Right to Buy) $ 17.72 02/12/2024 D( 4 ) 19,597 ( 4 ) 06/14/2033 Common Stock 19,597 ( 4 ) 0 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Thackray Helen M. C/O IMMUNOGEN, INC. 830 WINTER STREET WALTHAM, MA02451 X Signatures /s/ Joseph J. Kenny, Attorney-in-Fact 02/12/2024 Signature of Reporting Person Date

Explanation of Responses:

( 1 )This Form 4 reports securities disposed of pursuant to the terms of the Agreement and Plan of Merger (the "Merger Agreement"), dated November 30, 2023, by and among the Issuer, AbbVie Inc., a Delaware corporation ("AbbVie"), Athene Subsidiary LLC, a Delaware limited liability company and wholly owned subsidiary of AbbVie ("Intermediate Sub"), and Athene Merger Sub Inc., a Massachusetts corporation and wholly owned subsidiary of Intermediate Sub ("Purchaser"), pursuant to which Purchaser merged with and into the Issuer with the Issuer continuing as the surviving corporation (the "Merger"). At the effective time of the Merger (the "Effective Time"), each share of common stock, par value $.01 per share, of the Issuer (the "Common Stock"), that was issued and outstanding immediately prior to the Effective Time was converted into the right to receive an amount in cash equal to $31.26, without interest (the "Merger Consideration"). ( 2 )Pursuant to the Merger Agreement, at the Effective Time, each restricted stock unit ("RSU") granted prior to the date of the Merger Agreement that was outstanding immediately prior to the Effective Time was canceled, and the Reporting Person was entitled to receive (without interest), in consideration of the cancellation of such RSU, an amount in cash (less any applicable withholding taxes) equal to (i) the number of shares of Common Stock subject to such RSU immediately prior to the Effective Time, multiplied by (ii) the Merger Consideration. ( 3 )Pursuant to the Merger Agreement, at the Effective Time, each deferred share unit ("DSU") granted prior to the date of the Merger Agreement that was outstanding immediately prior to the Effective Time was canceled, and the Reporting Person was entitled to receive (without interest), in consideration of the cancellation of such DSU, an amount in cash (less any applicable withholding taxes) equal to (i) the number of shares of Common Stock subject to such DSU immediately prior to the Effective Time, multiplied by (ii) the Merger Consideration. ( 4 )Pursuant to the Merger Agreement, at the Effective Time, each option to purchase shares of Common Stock ("Stock Option") granted prior to the date of the Merger Agreement that was outstanding immediately prior to the Effective Time was canceled and the Reporting Person was entitled to receive (without interest), in consideration of the cancellation of such Stock Option, an amount in cash (less any applicable withholding taxes) equal to (i) the total number of shares of Common Stock subject to such Stock Option immediately prior to the Effective Time, multiplied by (ii) the excess, if any, of the Merger Consideration over the applicable exercise price per share of Common Stock under such Stock Option.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

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