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                                  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): May 4, 2000


                                 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.)


              333 Providence Highway, Norwood, Massachusetts 02062
              ----------------------------------------------------
              (Address of principal executive offices) (Zip Code)

       Registrant's telephone number, including area code: (781) 769-4242






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ITEM 5.           OTHER EVENTS

On May 4, 2000, ImmunoGen, Inc. and Genentech, Inc. announced that Genentech has
exclusively  licensed  ImmunoGen's  maytansinoid  Tumor-Activated  Prodrug (TAP)
technology for use with anti-HER2 antibodies such as Herceptin.  Under the terms
of  the  agreement,   Genentech  will  receive  exclusive  worldwide  rights  to
commercialize  anti-HER2  targeting products using ImmunoGen's  maytansinoid TAP
platform.  Genentech will be responsible for manufacturing,  product development
and  marketing  of  products  resulting  from  the  license;  ImmunoGen  will be
reimbursed for any  preclinical  and clinical  materials that it makes under the
agreement. ImmunoGen will receive an up-front payment of $2 million. In addition
to  royalties  on net  sales,  the  terms  of the  agreement  include  milestone
payments, assuming all benchmarks are met, for potentially up to $40 million.



The press release  announcing the exclusive  license  agreement is  incorporated
herein by reference and filed as exhibit 99.1 hereto.



ITEM 7.   FINANCIAL STATEMENTS AND EXHIBITS

(C)       Exhibits.

          99.1 The Registrant's Press Release dated May 4, 2000.

















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                               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 hereto duly authorized.




                                          ImmunoGen, Inc.
                                          (Registrant)


Date:     May 4, 2000                     /s/Kathleen A. Carroll
                                          --------------------------------------
                                          Kathleen A. Carroll
                                          Vice President, Finance and
                                            Administration, and principal
                                            financial officer










                                   Page 3 of 6
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EXHIBIT INDEX


Exhibit                                                             Sequential
Number                             Description                    Page Number(s)

99.1                     The Registrant's Press Release
                         dated May 4, 2000                              5



























                                   Page 4 of 6

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                                                                    Exhibit 99.1



IMMUNOGEN CONTACT:           Mitchel Sayare, Ph.D.
                             Chairman and CEO
                             ImmunoGen, Inc.
                             (781)769-4242
                                www.immunogen.com

GENENTECH CONTACTS:          www.gene.com

                             Media Contact:
                             Sabrina Johnson (650)225-2742

                                Investor Contact:
                          Mike Burchmore (650)225-8852


FOR IMMEDIATE RELEASE
- ---------------------

            ImmunoGen and Genentech Sign Exclusive License Agreement

     Cambridge, Mass. and South San Francisco,  Calif., May 4, 2000 - ImmunoGen,
     Inc.  (Nasdaq:  IMGN) and Genentech,  Inc. (NYSE: DNA) today announced that
     Genentech has exclusively licensed ImmunoGen's maytansinoid Tumor-Activated
     Prodrug (TAP)  technology  for use with  antibodies  such as Herceptin (R).
     Under  the  terms  of  the  agreement,  Genentech  will  receive  exclusive
     worldwide  rights  to  commercialize  anti-HER2  targeting  products  using
     ImmunoGen's  maytansinoid  TAP platform.  Genentech will be responsible for
     manufacturing, product development and marketing of products resulting from
     the license;  ImmunoGen will be reimbursed for any preclinical and clinical
     materials  that it makes under the  agreement.  ImmunoGen  will  receive an
     up-front payment of $2 million.  In addition to royalties on net sales, the
     terms of the agreement include milestone payments,  assuming all benchmarks
     are met, for potentially up to $40 million.


     "Genentech  has made a substantial  commitment to the  development of novel
     antibody  therapeutics,"  said  Dennis  Henner,  Senior Vice  President  of
     Research at Genentech, Inc. "Our preclinical work suggests that ImmunoGen's
     TAP technology  may be able to enhance the efficacy of antibodies  directed
     against  tumors.  This  collaboration  adds  a  potentially  important  new
     component to our BioOncology initiatives."

     "Genentech's  leadership in developing and  commercializing  antibody-based
     products for cancer is exceptional," said Mitchel Sayare,  Ph.D.,  Chairman
     and CEO of ImmunoGen,  Inc. "We are delighted that Genentech has recognized
     the value of our maytansinoid  platform as a way to create a new generation
     of anti-HER2 antibody products for the treatment of cancer."

     Genentech,   Inc.  is  a  leading  biotechnology  company  that  discovers,
     develops,  manufactures and markets human  pharmaceuticals  for significant
     unmet medical  needs.  Thirteen of the approved  products of  biotechnology
     stem from Genentech  science.  Genentech markets seven products directly in
     the United  States.  The company has  headquarters  in South San Francisco,
     California  and is traded on the New York Stock  Exchange  under the symbol
     DNA.

     ImmunoGen,  Inc.  develops  innovative  biopharmaceuticals,  primarily  for
     cancer treatment. The Company has created potent tumor-activated  prodrugs,
     consisting of drugs coupled to  monoclonal  antibodies  for delivery to and
     destruction of cancer cells.  The most advanced TAP,  huC242-DM1/SB-408075,
     designed to treat  colorectal  and  pancreatic  cancer,  is in a Phase I/II
     human clinical study. In addition to its maytansinoid platform of TAPs, the
     Company is working on other  proprietary TAP platforms  comprising  agents,
     such as taxanes, which exert cell-killing activity via different mechanisms
     of action.

     This  press   release   includes   forward-looking   statements   based  on
     management's current expectations.  Factors that could cause future results
     to differ  materially from such expectations  include,  but are not limited
     to: the ability to secure  future  funding;  the  success of the  Company's
     research strategy;  the applicability of the discoveries made therein;  the
     difficulties  inherent in the  development  of  pharmaceuticals,  including
     uncertainties as to the timing and results of preclinical studies;  delayed
     achievements of milestones;  reliance on  collaborators;  uncertainty as to
     whether the Company's  potential  products  will succeed in entering  human
     clinical  trials  and  uncertainty  as  to  the  results  of  such  trials;
     uncertainty as to whether  adequate  reimbursement  for these products will
     exist from the  government,  private  healthcare  insurers and  third-party
     payors;  and  the  uncertainties  as to the  extent  of  future  government
     regulation of the pharmaceutical business.
                                       ###