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                       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):  June 6, 1996
                                                   ------------

                                 IMMUNOGEN, INC.          
                                 ---------------      
             (Exact name of registrant as specified in its charter)

Massachusetts                      0-17999                04-2726691
- -------------                      -------                ----------
(State or other jurisdiction      (Commission           (IRS Employer
of incorporation)                 File Number)         Identification No.)


                128 Sidney Street, Cambridge, Massachusetts 02139
               -------------------------------------------------
                    (Address of principal executive offices)

       Registrant's telephone number, including area code: (617) 661-9312
                                                           --------------

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ITEM 5.     OTHER EVENTS
- -------     ------------

     On June 6, 1996, the Registrant amended its agreement with Capital Ventures
International dated March 15, 1996. This amendment is filed as Exhibit 10.29
hereto and incorporated herein by reference.

ITEM 7.     FINANCIAL STATEMENTS AND EXHIBITS
- -------     ---------------------------------

(c)         Exhibits.

            10.29 Letter Agreement dated as of June 6, 1996 by and among the
                  Registrant and Capital Ventures International regarding an
                  Amendment to their agreement dated March 15, 1996



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                                   SIGNATURES

     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.

                                          ImmunoGen, Inc.
                                          --------------- 
                                          (Registrant)




Date: June 10, 1996                       /s/ Frank J. Pocher            
      -------------                       -------------------    
                                          Frank J. Pocher
                                          Vice President and       
                                          principal financial officer


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                                EXHIBIT INDEX
                                -------------

Exhibit                                                      Sequential
Number            Description                                Page Number
- -------           -----------                                -----------

 10.29            Letter Agreement dated as of
                  June 6, 1996 by and among the
                  Registrant and Capital Ventures
                  International regarding an amendment
                  to their agreement dated March 15, 1996.       5


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                                 IMMUNOGEN, INC.




                                                            June 6, 1996

Capital Ventures International
c/o Bala International, Inc. (f/k/a Arbit, Inc.)
1900 Market Street
Philadelphia, PA  19102

Gentlemen:

     This letter is to confirm our agreement to modify the terms of the
debenture financing reflected in the Securities Purchase Agreement (the
"Purchase Agreement") dated March 15, 1996 between ImmunoGen, Inc. ("ImmunoGen")
and you, and the $2,500,000 principal amount convertible debenture (the "First
Debenture") dated March 25, 1996 issued to you pursuant to the Purchase
Agreement, subject to the terms and conditions provided below. Capitalized terms
used herein and not otherwise defined shall have the same meaning herein as in
the Purchase Agreement and the exhibits thereto. The Purchase Agreement and the
First Debenture are hereby amended as follows:

     1.   The First Debenture shall be automatically converted into shares of
          Common Stock in accordance with the terms of such Debenture on June 6,
          1996. For purposes of the foregoing, June 6, 1996 shall be deemed to
          be the "Conversion Date."

     2.   Notwithstanding anything in the Purchase Agreement or the First
          Debenture to the contrary, the conversion of the First Debenture
          pursuant to Paragraph 1 above shall be deemed to occur after the 80th
          day following the First Closing, so that the Debenture is convertible
          into Common Stock and Warrants as otherwise set forth therein with
          respect to conversions occurring after such 80th day. Accordingly,
          1,018,000 shares of Common Stock and Warrants to purchase 509,000
          shares of Common Stock are issuable upon conversion of the First
          Debenture.

     3.   Upon conversion of the First Debenture in accordance with Paragraph 1
          above, additional warrants (the "Additional Warrants") to purchase
          500,000 shares of Common Stock at an exercise price of $6.00 per share
          of Common Stock will be delivered to you along with the Common Stock
          and Warrants otherwise issuable in accordance with the terms of the
          First Debenture as modified hereunder. Except for the Exercise Price
          and the number of shares issuable thereunder, the Additional Warrants
          shall be in the Form of Exhibit A-1 to the First Debenture.


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Capital Ventures International
June 6, 1996
Page 2


     In addition to the foregoing, ImmunoGen plans to seek stockholder approval
of an amendment to its Restated Articles of Organization to authorize a new
class of preferred stock. If and when the preferred stock is approved by
ImmunoGen's stockholders, at ImmunoGen's request, you will convert the Debenture
issued in the Second Closing into shares of such preferred stock having the
following terms, for each $1 million of Debenture converted:

     i.   a purchase price and a liquidation preference over the Common Stock of
          $1 million;
     ii.  a floating cumulative dividend payable quarterly in cash or stock (in
          each case, based on the conversion rate), at the Company's option, at
          the rate of 9% per annum;
     iii. no voting rights (except as otherwise required by law);
     iv.  convertible at any time at your option into Common Stock and Warrants,
          so that the number of shares of Common Stock and Warrants into which
          the preferred stock is convertible shall be the same as the number of
          shares of Common Stock and Warrants into which the Debenture would
          have been convertible were it then outstanding;
     v.   protective provisions restricting the issuance of senior or pari passu
          securities without the majority of the preferred stock approving; and
     vi.  other terms negotiated in good faith consistent with the Purchase
          Agreement and exhibits.

     ImmunoGen agrees to register the resale of the shares of Common Stock
underlying the Additional Warrants, as well as the shares of Common Stock
issuable (including Common Stock underlying the Warrants) upon conversion of the
preferred stock, if any. The Common Stock underlying the Additional Warrants
issued upon conversion of the First Debenture shall be registered as promptly as
practicable following June 6, 1996, but in no event later than sixty days
hereafter. The Common Stock underlying the preferred stock (including Common
Stock underlying the Warrants) shall be registered as soon as practicable
following the issuance of the preferred stock, but no later than sixty days
thereafter. All of such Common Stock shall be deemed to be Registrable
Securities as defined in the Registration Rights Agreement. The penalties set
forth in Section 2(c) of the Registration Rights Agreement shall apply to any
failure to register Common Stock in accordance with this Paragraph. The
Registration Rights Agreement, as modified by that certain side letter dated
March 21, 1996 shall govern such registration.

     Except as expressly modified hereof, the Purchase Agreement and the
documents entered into in connection therewith shall remain in full force and
effect.


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Capital Ventures International
June 6, 1996
Page 3


     The Company represents that its shareholders have approved an increase in
the authorized Common Stock of the Company to 30 million. By execution of the
Agreement the Company confirms its agreement to issue the second Debenture as
promptly as practicable in accordance with the terms of the Purchase Agreement.

     This agreement reflects the present agreement of the parties hereto with
respect to the transactions contemplated hereby and shall be binding upon and
enforceable against the parties hereto.

     If the foregoing reflects your understanding of our agreement, please so
indicate by signing below.

                                    Very truly yours,

                                    /s/ Mitchel Sayare
                                    ---------------------
                                    Mitchel Sayare
                                    Chairman and Chief Executive Officer

Agreed to and Accepted:



By: _______________________
Name: _____________________
Its: ______________________



MS/cdl


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