EXHIBIT 4.3

                                                       NO. _____________________

                        THE COMMONWEALTH OF MASSACHUSETTS
- --------                     WILLIAM FRANCIS GALVIN
Examiner                  Secretary of the Commonwealth
              One Ashburton Place, Boston, Massachusetts 02108-1512


                              ARTICLES OF AMENDMENT
                    (General Laws, Chapter 156B, Section 72)
- --------
Name
Approved      We, MITCHEL SAYARE                                  , *President
                  ------------------------------------------------

              and JONATHAN KRAVETZ                                , *Clerk
                  ------------------------------------------------

              of IMMUNOGEN, INC.                                  ,
                 -------------------------------------------------
                          (EXACT NAME OF CORPORATION)

              located at 128 SIDNEY STREET, CAMBRIDGE, MA 02139 ,
                         -----------------------------------------------------
                            (STREET ADDRESS OF CORPORATION IN MASSACHUSETTS)

              certify that these Articles of Amendment affecting articles
              numbered:

                 3
              ----------------------------------------------------------------
               (NUMBERED THOSE ARTICLES 1, 2, 3, 4, 5 AND/OR 6 BEING AMENDED)

             of the Articles of Organization were duly adopted at a meeting
             held on NOVEMBER 13, 2001, BY VOTE OF:

             33,250,272 shares of COMMON STOCK of 39,680,326 shares outstanding,
             ----------           ------------    ----------
                                  (TYPE, CLASS
                                   & SERIES,
                                    IF ANY)

                     NO PREFERRED STOCK ISSUED & OUTSTANDING

                        shares of              of            shares outstanding,
             ----------           ------------    ----------
                                  (TYPE, CLASS
                                   & SERIES,
                                    IF ANY)

                        shares of              of            shares outstanding,
             ----------           ------------    ----------
                                  (TYPE, CLASS
                                   & SERIES,
                                    IF ANY)

C    [  ]
P    [  ] 1**being at least a majority of each type, class or series outstanding
          and entitled to vote thereon: / or  2** being at
M    [  ] least two-thirds of each type, class or series outstanding and
          entitled to vote thereon and of each type, class or
R.A. [  ] series of stock whose rights are adversely affected thereby:


- -----------
P.C.

- -------------------------------

*      DELETE THE INAPPLICABLE WORDS.

**     DELETE THE INAPPLICABLE CLAUSE.

1      FOR AMENDMENTS ADOPTED PURSUANT TO CHAPTER 156B, SECTION 70.

2      FOR AMENDMENTS ADOPTED PURSUANT TO CHAPTER 156B, SECTION 71.

NOTE:  IF THE SPACE PROVIDED UNDER ANY ARTICLE OR ITEM ON THIS FORM IS
       INSUFFICIENT, ADDITIONS SHALL BE SET FORTH ON ONE SIDE ONLY OF SEPARATE 8
       1/2 X 11 SHEETS OF PAPER WITH A LEFT MARGIN OF AT LEAST 1 INCH. ADDITIONS
       TO MORE THAN ONE ARTICLE MAY BE MADE ON A SINGLE SHEET SO LONG AS EACH
       ARTICLE REQUIRING EACH ADDITION IS CLEARLY INDICATED.




To CHANGE the number of shares and the part value (if any) of any type, class or
series of stock which the corporation is authorized to issue, fill in the
following:

The total PRESENTLY authorized is:



- ----------------------------------------------------- -----------------------------------------------------------------------------
              WITHOUT PAR VALUE STOCKS                                           WITH PAR VALUE STOCKS
                                                                                             
- -------------------- -------------------------------- ----------------- --------------------------------- -------------------------
       TYPE:                NUMBER OF SHARES                TYPE                NUMBER OF SHARES                 PAR VALUE
- -------------------- -------------------------------- ----------------- --------------------------------- -------------------------
      Common:                                             Common:       50,000,000                        $.01
- -------------------- -------------------------------- ----------------- --------------------------------- -------------------------

- -------------------- -------------------------------- ----------------- --------------------------------- -------------------------
     Preferred                                           Preferred:     5,000,000*                        $.01
- -------------------- -------------------------------- ----------------- --------------------------------- -------------------------

- -------------------- -------------------------------- ----------------- --------------------------------- -------------------------


CHANGE the total authorized to:



- ----------------------------------------------------- -----------------------------------------------------------------------------
              WITHOUT PAR VALUE STOCKS                                           WITH PAR VALUE STOCKS
                                                                                             
- -------------------- -------------------------------- ----------------- --------------------------------- -------------------------
       TYPE:                NUMBER OF SHARES                TYPE                NUMBER OF SHARES                 PAR VALUE
- -------------------- -------------------------------- ----------------- --------------------------------- -------------------------
      Common:                                             Common:       75,000,000                        $.01
- -------------------- -------------------------------- ----------------- --------------------------------- -------------------------

- -------------------- -------------------------------- ----------------- --------------------------------- -------------------------
     Preferred                                           Preferred:     5,000,000*                        $.01
- -------------------- -------------------------------- ----------------- --------------------------------- -------------------------

- -------------------- -------------------------------- ----------------- --------------------------------- -------------------------



          *Preferred:           Series A Convertible Preferred     2,500
                                Shares $.01 par value
                                Series B Convertible Preferred     3,000
                                Shares $.01 par value
                                Series C Convertible Preferred     3,000
                                Shares $.01 par value
                                Series D Convertible Preferred     1,000
                                Shares $.01 par value
                                Series E Convertible Preferred     2,400
                                Shares $.01 par value









The foregoing amendment(s) will become effective when these Articles of
Amendment are filed in accordance with General Laws, Chapter 156B, Section 6
unless these articles specify, in accordance with the vote adopting the
amendment, a LATER effective date not more than THIRTY DAYS after such filing,
in which event the amendment will become effective on such later date.

Late effective date:                                                   .
                     --------------------------------------------------

SIGNED UNDER THE PENALTIES OF PERJURY, this 13TH day of NOVEMBER   , 2001      ,
                                            ----        -----------     --------


/S/ MITCHEL SAYARE                                                  , *President
- --------------------------------------------------------------------


/S/ JONATHAN L. KRAVETZ                                               *Clerk
- --------------------------------------------------------------------

*DELETE THE INAPPLICABLE WORDS.





                        THE COMMONWEALTH OF MASSACHUSETTS

                              ARTICLES OF AMENDMENT
                    (GENERAL LAWS, CHAPTER 156B, SECTION 72)


- --------------------------------------------------------------------------------

I hereby approve the within Articles of Amendment and, the filing fee in the
amount of $________ having been paid, said articles are deemed to have been
filed with me this ____ day of ____________, 20 ______.

EFFECTIVE DATE:
               ----------------------------------------------------------------



                             WILLIAM FRANCIS GALVIN
                          SECRETARY OF THE COMMONWEALTH


                         TO BE FILLED IN BY CORPORATION
                      PHOTOCOPY OF DOCUMENT TO BE SENT TO:



        JONATHAN KRAVETZ, ESQUIRE
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        MINTZ, LEVIN, COHN, FERRIS, GLOVSKY AND POPEO, P.C.
        -----------------------------------------------------------

        ONE FINANCIAL CENTER, BOSTON, MA 02111
        -----------------------------------------------------------

        Telephone: 617 542-6000
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