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 OF SECURITIES 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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(Print or Type Responses)

1. Name and Address of Reporting Person * PIEN HOWARD H   2. Issuer Name and Ticker or Trading Symbol IMMUNOGEN INC [IMGN] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner _____ Officer (give title below) __X__ Other (specify below) Former Director (Last) (First) (Middle) 6 CARRIAGE HOUSE COURT 3. Date of Earliest Transaction (Month/Day/Year) 05/16/2007 (Street) CHERRY HILL, NJ 08003 4. If Amendment, Date Original Filed(Month/Day/Year) 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 (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 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 05/16/2007   M   2,168 A $ 5.03 2,168 D

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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 (Month/Day/Year)

3A. Deemed Execution Date, if any (Month/Day/Year)

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 (Month/Day/Year)

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

Deferred Share Unit

$ 0 (1)

05/16/2007

M

2,168

(2)(3)

(2)

Common Stock (2)

2,168

$ 0 (1)

2,168

D

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
PIEN HOWARD H 6 CARRIAGE HOUSE COURT CHERRY HILL, NJ 08003				Former Director

Signatures

/s/ Daniel M. Junius		05/18/2007
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 4(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1)	The deferred share units were issued pursuant to the Issuer's 2004 Non-Employee Director Compensation and Deferred Share Unit Plan, as amended, and are convertible into Common Stock on a one-to-one basis.
(2)	On May 16, 2007, the reporting person resigned from the Board of Directors, and as a result, the vested deferred share units are settled 100% in shares of Common Stock of the Company. The unvested portions of the deferred share units have expired by their terms.
(3)	The deferred share units are fully vested. The reporting person received 131, 862, and 18 deferred share units on Februray 14, 2007, May 14, 2007, and May 16, 2007, respectively, which vested immediately. The reporting person also received a grant on January 31, 2007 for 13,888 deferred share units, which vested ratably over a three year period in quarterly increments at the end of each quarter, of which 1,157 shares were fully vested upon the reporting person's resignation.

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