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                                                                    Exhibit 10.2

                                LICENSE AGREEMENT

                                     between

                         SMITHKLINE BEECHAM CORPORATION

                                       and

                                 IMMUNOGEN, INC.
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                                LICENSE AGREEMENT

         THIS LICENSE AGREEMENT (hereinafter "AGREEMENT"), made as of the 1st
day of February, 1999, between ImmunoGen, Inc., a corporation organized and
existing under the laws of the Commonwealth of Massachusetts, having a principal
place of business at 333 Providence Highway, Norwood, Massachusetts 02062 and
SmithKline Beecham Corporation, a corporation organized and existing under the
laws of the Commonwealth of Pennsylvania, and having its principal office at One
Franklin Plaza, Philadelphia, Pennsylvania 19101,

                                WITNESSETH THAT:

         WHEREAS, IMMUNOGEN, as defined below, is the owner of all right, title
and interest in, or otherwise controls certain patents, identified in APPENDIX A
hereto, and know-how relating to a conjugated antibody known as huC242-DM1 and
the components thereof; and

         WHEREAS, SB, as defined below, desires to obtain certain licenses in
all countries of the world from IMMUNOGEN to develop and commercialize
huC242-DM1 in such countries under the aforesaid patents and know-how, and
IMMUNOGEN is willing to grant to SB such licenses;

         NOW, THEREFORE, in consideration of the covenants and obligations
expressed herein, and intending to be legally bound, and otherwise to be bound
by proper and reasonable conduct, the parties agree as follows:

1.       DEFINITIONS

         1.01 "AFFILIATES" shall mean any corporation, firm, partnership or
other entity, whether de jure or de facto, which directly or indirectly owns, is
owned by or is under common ownership with a party to this AGREEMENT where
"owns" or "ownership" means possession of at least fifty percent (50%) of the
equity of such corporation, firm, partnership or other entity (or such lesser
percentage which is the maximum allowed to be owned by a foreign corporation in
a particular jurisdiction) having the power to vote on or direct the affairs of
the entity and any person, firm, partnership, corporation or other entity
actually controlled by, controlling or under common control with a party to this
AGREEMENT.
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         1.02 "BLA" shall mean a Biologics License Application, or New Drug
Application, whichever is applicable to PRODUCT, as defined by the regulations
promulgated under the United States FD&C Act and PHS Act and any supplements
thereunder, as amended from time to time.

         1.03 "C242" shall mean any antibody or fragment thereof which binds to
the same epitope as the antibody produced by hybridoma cell line C242:II, which
cell line has ECACC identification number 90012601.

         1.04 "DM1" shall mean that maytansinoid drug whose more specific
chemical name is N2'-deacetyl-N2'-(3-mercapto-1-oxopropyl)-maytansine.

         1.05 "EFFECTIVE DATE" shall mean the date upon which this AGREEMENT is
effective and shall be the date of this AGREEMENT first written above.

         1.06 "FDA" shall mean the United States Food and Drug Administration or
its successor entity.

         1.07 "FIELD" shall mean any human use of PRODUCT.

         1.08 "huC242" shall mean a humanized antibody which binds to the same
epitope as C242. One such humanized antibody has the cDNA sequence outlined in
APPENDIX E.

         1.09 "huC242-DM1" shall mean huC242 conjugated to DM1.

         1.10 "IMMUNOGEN" shall mean ImmunoGen, Inc., a corporation of the
Commonwealth of Massachusetts, having a principal place of business at 333
Providence Highway, Norwood, Massachusetts 02062.

         1.11 "IND" shall mean an Investigational New Drug Application as
defined in the regulations promulgated by the FDA.

         1.12 "IRL AGREEMENT" shall mean the November 17, 1998 letter agreement
between Industrial Research Ltd. ("IRL"), having a mailing address of Box
31-310, Lower Hutt, New Zealand and IMMUNOGEN related to the selection by IRL of
a strain producing Ansamitocin P-3.

         1.13 "JOINT DEVELOPMENT COMMITTEE" shall mean the committee appointed
by the parties as set forth in Paragraph 5.02.

         1.14 "KNOW-HOW" shall mean all present and future information and
know-how which relates to PRODUCT in the FIELD in the TERRITORY which is not in
the public domain



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which is or becomes owned, in whole or in part, by IMMUNOGEN, or to which
IMMUNOGEN otherwise has, now or in the future, the right to grant licenses, and
shall include, without limitation, all biological, chemical, pharmacological,
toxicological, clinical, assay, control and manufacturing data and materials and
any other information relating to PRODUCT in the FIELD and useful for the
development and commercialization of PRODUCT in the FIELD.

         1.15 "LAUNCH" shall mean the first commercial sale of a PRODUCT in a
given country of the TERRITORY by or on behalf of SB after the PRODUCT has been
granted regulatory approval by the competent authorities in such country.

         1.16 "MAA" shall mean that regulatory application in the European
Community which is the equivalent of a BLA.

         1.17 "MAY" shall mean any maytansinoid drug, including but not limited
to, maytansine and DM1, whether produced by a botanical source, natural
fermentation, or chemical synthesis, and any derivative thereof.

         1.18 "NET SALES" shall mean the gross receipts representing commercial
sales of PRODUCT in the FIELD in the TERRITORY under this AGREEMENT by SB, its
AFFILIATES or sublicensees ("the Selling Party") to THIRD PARTIES:

         (a) in finished product form (i.e., packaged and labeled for sale to
         the ultimate consumer); or
         (b) in any product form other than finished
         product form (such as final stage bulk material ready for conversion to
         final form, or bulk tablets, bulk capsules, bulk ampoules or bulk
         vials) to distributors who are not AFFILIATES of the Selling Party who
         subsequently convert such product form into finished product form and
         sell to THIRD PARTIES, provided that such distributors shall not be
         considered sublicensees for purposes of this NET SALES definition, and
         further provided that for purposes of this Paragraph, such sales of
         PRODUCT in final stage bulk material form shall occur only where such
         sales are due to local country requirements as such requirements are
         determined in good faith by SB;

less deductions actually allowed or specifically allocated to PRODUCT by the
Selling Party using generally accepted accounting standards for:


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                  (i) transportation charges, including insurance, for
transporting PRODUCT, to the extent that they are included in the price or
otherwise paid by the purchaser;

                  (ii) sales and excise taxes and duties paid or allowed by the
Selling Party and any other governmental charges imposed upon the actual
production, importation, use or sale of such PRODUCT;

                  (iii) trade, quantity and cash discounts actually allowed or
taken on PRODUCT;

                  (iv) allowances or credits to customers on account of
rejection or return of PRODUCT or on account of retroactive price reductions
affecting such PRODUCT; and

                  (v) PRODUCT rebates and PRODUCT charge backs including those
granted to managed-care entities. Sales between SB, its AFFILIATES and its or
their sublicensees and affiliates of such sublicensees shall be excluded from
the computation of NET SALES and no royalties will be payable on such sales
except where such AFFILIATES, sublicensees, or affiliates of such sublicensees
are end users of the PRODUCT. Notwithstanding the immediately preceding
sentence, it is understood that any transactions between SB or any of its
AFFILIATES or any of its or their sublicensees on the one hand and any PSB on
the other hand will be deemed to be transactions with THIRD PARTIES for the
purposes of computing NET SALES, provided that the conditions of such sales to
such PSB, including any and all rebates and discounts allocated to transactions
with any such PSB, shall be on an arm's length basis and shall be fully
deductible for such computation purposes. In the event that any PSB type
activity is within SB or within any of its AFFILIATES or its or their
sublicensees as only part of its or their total activities rather than in a
separate AFFILIATE, a notional Net Sales figure will be calculated in good faith
on an arm's length basis to cover such activities.

         1.19 "PATENTS" shall mean all patents and patent applications in the
FIELD in the TERRITORY which are or become owned, in whole or in part, by
IMMUNOGEN, or to which IMMUNOGEN otherwise has, now or in the future, the right
to grant licenses, which generically or specifically claim PRODUCT and/or MAY
and/or huC242 and/or C242, a process for manufacturing PRODUCT and/or MAY and/or
huC242 and/or C242, an intermediate used in such process or a use of PRODUCT
and/or MAY and/or huC242 and/or C242. Included within


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the definition of PATENTS are all continuations, continuations-in-part,
divisions, patents of addition, reissues, renewals or extensions thereof and all
SPCs. Also included within the definition of PATENTS are any patents or patent
applications which generically or specifically claim any improvements on PRODUCT
and/or MAY and/or huC242 and/or C242 or intermediates or manufacturing processes
required or useful for production of PRODUCT and/or MAY and/or huC242 and/or
C242 which are developed by or on behalf of IMMUNOGEN, or which IMMUNOGEN
otherwise has the right to grant licenses, now or in the future, during the term
of this AGREEMENT. The current list of patent applications and patents
encompassed within PATENTS is set forth in APPENDIX A attached hereto. APPENDIX
A shall be updated by IMMUNOGEN on a semi-annual basis during the term of this
AGREEMENT, beginning in the first calendar year following the EFFECTIVE DATE.

         1.20 "PRODUCT" shall mean any composition of matter for use in the
FIELD, the PATENTS and/or KNOW-HOW to which are owned in whole or in part or
otherwise controlled by IMMUNOGEN, and to which IMMUNOGEN has the right to grant
a license to SB in accordance with Article 2 of this AGREEMENT as of the
EFFECTIVE DATE or acquires such right during the term of this AGREEMENT, which
is directed against the CanAg Determinant whether such is unconjugated or
conjugated to a radioisotope, cytotoxic chemical, biological toxin, chemical
antineoplastic or biological antineoplastic, and shall include compositions
comprising such composition of matter. An example of a PRODUCT includes, but is
not limited to any antibody (whether fully human, fully murine, chimeric, or
humanized, or otherwise derivatized) or fragment thereof, or any derivative
thereof, which binds to the same epitope as the antibody produced by hybridoma
cell line C242:II, which cell line has ECACC identification number 90012601,
such as, but not limited to huC242-DM1. By the term 'CanAg Determinant' as used
in this provision is meant the CA-242 antigen as such is defined in Column 4,
line 30 of U.S. Patent 5,552,293, issued September 3, 1996, as well as in
Johansson et al., Tumor Biol., 1991; 12:159-170.

         1.21 "P&U AGREEMENT" shall mean the License Agreement between Pharmacia
and Upjohn AB, a company organized and existing under the laws of Sweden, having
an address of Lindhagensgatan 133 SE-11287 Stockholm, Sweden and IMMUNOGEN,
which was effective as of June 1, 1998, and amended by IMMUNOGEN and Pharmacia
and Upjohn AB as of



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October 23, 1998. It is mutually understood that, as of the EFFECTIVE DATE, the
rights granted to IMMUNOGEN by Pharmacia and Upjohn AB are limited to those
defined in the P&U AGREEMENT.

         1.22 "PSB" shall mean any present or future AFFILIATE of SB or its
sublicensees which conducts a Pharmaceutical Service Business for or on behalf
of THIRD PARTIES, including, but not limited to, Pharmaceutical Benefits
Management Services (hereinafter "PBM"), wholesaler distribution, pharmacy
distribution, managed-care services, disease-management services, hospital
services, or mail-order prescription pharmacy services. As of the EFFECTIVE
DATE, an AFFILIATE of SB which is included within the definition of PBM is
Diversified Pharmaceutical Services, a corporation of the state of Minnesota and
having a place of business at 3600 West 80th Street, Seventh Floor, Bloomington,
Minnesota 55431-1085, U.S.A.

         1.23 "SB" shall mean SmithKline Beecham Corporation, a corporation
organized and existing under the laws of the Commonwealth of Pennsylvania, and
having its principal office at One Franklin Plaza, Philadelphia, Pennsylvania
19101.

         1.24 "SPC" shall mean a right based upon a PATENT to exclude others
from making, using or selling PRODUCT, such as a Supplementary Protection
Certificate.

         1.25 "TAKEDA AGREEMENT" shall mean the April 8, 1994 License Agreement
between Takeda Chemical Industries, Ltd. and IMMUNOGEN.

         1.26 "TERRITORY" shall mean all the countries and territories of the
world except for Japan, China, Korea, Taiwan, Hong Kong, Burma, Malaysia,
Philippines, Thailand, Vietnam, Singapore, India, Pakistan, Syria, Jordan,
Lebanon and Saudi Arabia. In the event that IMMUNOGEN determines that the
countries excluded from the TERRITORY are not subject to the TAKEDA AGREEMENT,
IMMUNOGEN shall promptly notify SB, and if SB confirms IMMUNOGEN's
determination, such countries shall thereafter automatically become part of the
TERRITORY.

         1.27 "THIRD PARTY(IES)" shall mean any party other than SB and
IMMUNOGEN.

         1.28 "U.S.A." shall mean the United States of America, including all of
its territories and possessions


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         1.29 "ZENECA JOINDER" shall mean the receipt by IMMUNOGEN from Zeneca
Group PLC, a corporation of the country of England, having its registered office
at 15 Stanhope Gate, London, W1Y6GN, England (hereinafter "Zeneca") of Zeneca's
written consent to the P&U AGREEMENT and to IMMUNOGEN's grant of a sublicense to
SB under IMMUNOGEN's rights under the P&U AGREEMENT, or the corresponding
consent from an affiliate of Zeneca who has the right to grant such consent.

2.       GRANT

         2.01 IMMUNOGEN hereby grants to SB an exclusive license, with the right
to grant sublicenses, under PATENTS and KNOW-HOW, to the extent of IMMUNOGEN's
rights therein, to make, have made, use, sell, offer for sale and import PRODUCT
in the FIELD in the TERRITORY, subject to the other terms and conditions of this
AGREEMENT. The rights to make, have made, use, sell, offer for sale and import
shall include all activities relevant to the FIELD concerning the subject matter
of PATENTS and KNOW-HOW which activities would, but for the license herein
granted, infringe PATENTS and KNOW-HOW.

3.       PAYMENTS AND ROYALTIES

         3.01 In consideration for the license under PATENTS and KNOW-HOW
granted to SB in this AGREEMENT, SB shall make the following milestone payments
to IMMUNOGEN, up to a maximum of forty-one million five hundred thousand U.S.
dollars (U.S. $ 41,500,000) in the specified incremental amounts, within thirty
(30) days after the first occurrence of each of the following milestones,
subject to any credit which may be due SB under Paragraphs 4.02(a) and 4.02(c),
and subject to any reduction in the relevant payment amount, or elimination of
SB's obligation to make any such payment, as outlined in Paragraphs 3.01(2),
(3), (7), (9), and (12):

[*]


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provided that:

     (1) each such payment shall be made only one time upon the first
achievement of the relevant milestone, regardless of how many times such
milestones are achieved and regardless of how many times PRODUCT achieves such
milestones, and no payment shall be owed for a milestone which is not reached
during the term of the AGREEMENT;

     (2) the term [*] as used in this Paragraph shall mean the

         [*]


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                  (a) Based on the results of the [*] , IMMUNOGEN will decide in
good faith if [*] has been achieved and notify SB in writing of such
achievement, including all of the data outlined in Paragraph 3.01(2)(i) - (v).
SB will review the same data in good faith. If SB concurs, based on such data,
that a [*] has been achieved, the milestone outlined in Paragraph 3.01(b) shall
be deemed to be achieved on the day of SB's concurrence. SB shall notify
IMMUNOGEN, in writing, within thirty (30) days after receipt of IMMUNOGEN's
written notification, and all data outlined in Paragraph 3.01(2)(i) - (v),
whether or not SB has determined that a [*] has been achieved by June 30, 1999.

                  (b) Notwithstanding the above, if a [*] is not achieved by
June 30, 1999:

                      (i) no payment shall be owed by SB to IMMUNOGEN under
Paragraph 3.01(b),

                      (ii) no payments shall be owed by SB to IMMUNOGEN under
Paragraphs 3.01(c), (d), and (e) for the achievement of the milestones related
to [*] respectively,

                      (iii) SB's payment obligation under Paragraph 3.01(f)
shall be reduced by [*] and

                      (iv) the provisions of Paragraph 5.07 shall be applicable.

                  (c) In the event that SB does not agree with IMMUNOGEN's
assertion that a [*] has been achieved by June 30, 1999, SB shall so notify
IMMUNOGEN in writing, and the parties shall promptly submit such issue
thereafter to the Chairman, Research & Development of SB and the Chief Executive
Officer of


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IMMUNOGEN for resolution. In the event that the Chairman, Research &
Development of SB and the Chief Executive Officer of IMMUNOGEN are unable to
agree on the issue, then the parties shall submit such issue to a mutually
acceptable THIRD PARTY who has suitable expertise on the topic in question
(hereafter "Unaffiliated Expert"), such Unaffiliated Expert to be chosen by the
parties within ten (10) business days after the Chairman, Research & Development
of SB and the Chief Executive Officer of IMMUNOGEN are unable to agree on the
issue, and request resolution within thirty (30) days after the date of such
submission to such Unaffiliated Expert, and SB's obligation to make any payment
under Paragraph 3.01(b) shall be stayed during the period of time that the
Unaffiliated Expert is making a resolution of the matter. The resolution of such
Unaffiliated Expert shall be binding upon both parties. If such Unaffiliated
Expert determines that such [*] has been achieved by the required date, the
expenses of engaging such Unaffiliated Expert for such determination shall be
borne by SB, and SB shall owe IMMUNOGEN the payment under Paragraph 3.01(b),
such payment to be made within thirty (30) days after the date of the
Unaffiliated Expert's resolution of such matter. If such Unaffiliated Expert
determines that such demonstration has not been achieved by the required date:

                      (i) the expenses of engaging such Unaffiliated Expert for
         such determination shall be borne by IMMUNOGEN, and

                      (ii) the provisions of Paragraph 3.01(2)(b) shall be
         applicable. 

         (3) the term [*] as used in this Paragraph shall mean [*]


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         Notwithstanding the above, if [*] is not achieved by November 30, 1999,
then either:

              (a) the payment outlined under Paragraph 3.01(c) shall be owed by
SB to IMMUNOGEN if [*]

                                                                              or

              (b) if Paragraph 3.01(3)(a) is not applicable, the payment owed by
SB to IMMUNOGEN under Paragraph 3.01(c) shall be reduced to [*] and SB's payment
obligation thereunder shall not vest until the date SB has received [*] (as
defined in Paragraph 3.01(3) except that the [*] and the following shall also be
applicable:

                    (i) no payments shall be owed by SB to IMMUNOGEN under
Paragraphs 3.01(d) and (e) for the achievement of the milestones related to [*]
respectively, and 

                   (ii) the provisions of Paragraph 5.08 shall be applicable.

         (4) the term [*] as used in this Paragraph shall mean the date on which
the [*]

                           under this AGREEMENT in accordance with APPENDIX D,
which is intended to [*]

         (5) the term [*] as used in this Paragraph shall mean [*] such
demonstration to be determined by SB using the same standards SB would use in
assessing whether or not to [*]


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SB shall make its determination of whether or not [*] has been demonstrated no
later than ninety (90) days after the [*] agreed by the JOINT DEVELOPMENT
COMMITTEE and provisionally outlined as of the EFFECTIVE DATE in APPENDIX B, and
SB shall notify IMMUNOGEN of its determination within the same time period;

         (6) by the term [*] as used in this Paragraph shall mean the earlier
of;

                  (a) the date [*]

or

                  (b) the date [*]

         (7) by the term [*] with respect to each of the indicated milestones is
meant that [*] will be paid for [*] indicated milestones to occur, i.e., up to a
total of [*] provided that a milestone payment shall be due for [*]

         (8) by the term [*] as used in this Paragraph is meant, with respect
[*]

         (9) by the term [*] as used in this Paragraph is meant the [*]


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Notwithstanding the above, in the event that the [*] has not been achieved at
the time that [*] is achieved [*] or IMMUNOGEN has not otherwise [*] SB shall
owe IMMUNOGEN only [*] of the amount outlined in Paragraph 3.01(h) for such [*]
milestone.

         (10) by the term [*] as used in this Paragraph is meant [*]

         (11) by the term [*] as used in this Paragraph is meant [*]

         (12) by the term [*] is meant that, [*]





         3.02 (i) In the event that Paragraph 5.07 is not applicable then, in
further consideration for the licenses and sublicenses under PATENTS granted to
SB under this AGREEMENT, and subject to Paragraph 4.02, SB shall make the
following royalty payments to IMMUNOGEN on a per PRODUCT basis:

                  (a) [*] of annual NET SALES of such PRODUCT up to and
including [*]

                  (b) [*] of annual NET SALES of such PRODUCT in excess of [*])
up to and including [*] and

                  (c) [*] of annual NET SALES of such PRODUCT in excess of [*]


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provided that, for purposes of this Paragraph, achievement of the NET SALES
thresholds recited above shall be determined by adding the total annual NET
SALES of such PRODUCT during each calendar year in all countries of the
TERRITORY in which there is an issued PATENT which claims the particular PRODUCT
at the time such NET SALES of such PRODUCT occur.

                  (ii) In the event that Paragraph 5.07 is applicable then, in
further consideration for the licenses and sublicenses under PATENTS granted to
SB under this AGREEMENT, and subject to Paragraph 4.02, SB shall make the
following royalty payments to IMMUNOGEN on a per PRODUCT basis:

                      (a) [*] of annual NET SALES of such PRODUCT up to and
including [*] and

                      (c) [*] of annual NET SALES of such PRODUCT in excess of 
[*] provided that, for purposes of this Paragraph, achievement of the NET SALES
thresholds recited above shall be determined by adding the total annual NET
SALES of such PRODUCT during each calendar year in all countries of the
TERRITORY in which there is an issued PATENT which claims the particular PRODUCT
at the time such NET SALES of such PRODUCT occur.

         3.03 As further consideration for the license to KNOW-HOW granted to SB
under this AGREEMENT, in those countries of the TERRITORY in which NET SALES of
a particular PRODUCT are not subject to the royalty obligation outlined in
Paragraph 3.02, royalties payable by SB to IMMUNOGEN shall be calculated
separately on each such PRODUCT at [*] the applicable royalty rates set forth in
Paragraph 3.02.

         3.04 NET SALES of PRODUCT formulated in combination with one or more
additional therapeutically active ingredients shall be calculated separately
from the royalties outlined in Paragraphs 3.02 and 3.03, and [*] of the
royalties outlined in Paragraphs 3.02 and 3.03 [*]

         3.05 [*] of the royalties outlined in Paragraphs 3.02 and 3.03 for 
NET SALES of PRODUCT if SB determines that it wants to promote PRODUCT for other
than human prescription pharmaceutical use (e.g., over-the-counter, diagnostic,
pharmacy only) [*], in good faith, by the parties.


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         3.06 SB's royalty obligations under Paragraph 3.02 shall become
effective in each country in the TERRITORY at such time as there is a LAUNCH of
PRODUCT by SB, its AFFILIATES or its sublicensees in such country and there is
an enforceable PATENT granted in such country claiming the PRODUCT sold. SB's
royalty obligations under Paragraph 3.03 shall become effective in each country
in the TERRITORY either (a) at such time as there is a LAUNCH of PRODUCT by SB,
its AFFILIATES or its sublicensees in those countries of the TERRITORY in which
the PRODUCT is not subject to the royalty obligation outlined in Paragraph 3.02,
or (b) after the expiration in such country of the royalty obligation outlined
in Paragraph 3.02 subject to Paragraph 10.01.

         3.07 In the event that any person or party initiates any legal or
administrative proceeding challenging the validity, scope or enforceability of a
PATENT in any country in the FIELD in the TERRITORY, such as by opposing the
grant of the PATENT in the European Patent Office, and in the event such
challenge were successful, there would be no PATENT claiming the PRODUCT sold in
such country, then, at the time there is a THIRD PARTY product on the market in
such country, the making, use or sale of which is covered by the challenged
PATENT, the royalty obligation in Paragraph 3.03 shall be applicable to NET
SALES in such country during the pendency of the proceeding, and the royalty
obligation on NET SALES in such country outlined in Paragraph 3.02 shall be [*]:

                  (a) If the enforceability of at least one claim in the PATENT
claiming the PRODUCT sold is upheld by a court or other legal or administrative
tribunal from which no appeal is or can be taken, then the amount of royalties
owed under Paragraph 3.02 during the period of suspension, less any amount paid
under Paragraph 3.03, shall be promptly paid [*], to IMMUNOGEN from [*].

                  (b) If the claims in the PATENT are held to be invalid or
otherwise unenforceable by a court or other legal or administrative tribunal
from which no appeal is or can be taken, then (i) the amount of royalties which
would have otherwise been owed under Paragraph 3.02 during the period of
suspension shall be promptly paid, [*], to SB [*], (ii) no further royalties
under Paragraph 3.02 shall be


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owed with respect to the sale of such PRODUCT in such country, (iii) the royalty
obligation in Paragraph 3.03 shall thereafter be applicable in such country, and
(iv) SB shall retain the licenses granted herein.

         3.08 In addition to the payments set forth in Paragraphs 3.01 through
3.07, and provided that Paragraph 5.07 is not applicable, SB shall purchase from
IMMUNOGEN, at IMMUNOGEN's option, up to five million U.S. dollars (U.S.
$5,000,000) worth of IMMUNOGEN common stock pursuant to the terms and conditions
of a separate Stock Purchase Agreement to be executed simultaneously herewith.

4.       COMPULSORY LICENSES AND THIRD PARTY LICENSES

         4.01 In the event that a governmental agency in any country or
territory of the TERRITORY grants or compels IMMUNOGEN to grant a license to any
THIRD PARTY for PRODUCT, SB shall have the benefit in such country or territory
of the terms granted to such THIRD PARTY to the extent that such terms are more
favorable than those of this AGREEMENT. SB shall have the same benefit in all
countries and territories outside the country in which the compulsory license is
granted in which the THIRD PARTY product is sold in competition with SB if the
THIRD PARTY compulsory licensee's sales in such other countries and territories
are permitted by the compulsory license.

         4.02 It is acknowledged that prior to the EFFECTIVE DATE, IMMUNOGEN and
SB have each entered into certain THIRD PARTY license agreements in the
TERRITORY, or may enter into certain additional THIRD PARTY license agreements
in the TERRITORY after the EFFECTIVE DATE, under which payments will be required
in order to avoid infringement during the exercise of the license herein granted
(collectively "Third Party License Agreements").

                  (a) Payments Required by the P&U AGREEMENT: [*] Pharmacia and
Upjohn AB, a company organized and existing under the laws of Sweden, having an
address of Lindhagensgatan 133 SE-11287 Stockholm, Sweden (hereafter "P&U"),
[*], all payments which are accrued by IMMUNOGEN under the P&U AGREEMENT after
the EFFECTIVE DATE and which are required as a direct result of SB's or
IMMUNOGEN's activities in the TERRITORY in the FIELD under this AGREEMENT


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(hereafter "P&U Payments") in accordance with the provisions of the P&U
AGREEMENT. [*]. It is understood that SB shall have no liability for any
payments owed by IMMUNOGEN under the P&U AGREEMENT which are related to the
activities of IMMUNOGEN or its licensees outside of the FIELD and/or outside of
the TERRITORY.

                  (b) Payments Required by Third Party License Agreements Other
than the P&U AGREEMENT Entered Into by IMMUNOGEN Prior to or During the Term of
this AGREEMENT: IMMUNOGEN shall have sole financial responsibility for all
royalty and other payments required to be paid by IMMUNOGEN under any Third
Party License Agreements entered into by IMMUNOGEN [*] as a result of either
party's activities under this AGREEMENT, including, without limitation, the
TAKEDA AGREEMENT, or under any agreement between IMMUNOGEN and Zeneca (as
defined in Paragraph 1.29) related to the subject matter of the P&U AGREEMENT,
or as a result of IMMUNOGEN's or its licensee's activities outside of the
TERRITORY or outside of the FIELD, such payments to be made by IMMUNOGEN
directly to the relevant THIRD PARTY in accordance with the provisions of the
applicable Third Party License Agreement.

                  (c) Payments Required by Third Party License Agreements
Entered Into by SB Prior to or During the Term of this AGREEMENT: [*] all
royalty or other payments required to be paid by SB under any such Third Party
License Agreements which payments are required as a result of either IMMUNOGEN's
or SB's activities under this AGREEMENT, [*] directly to the relevant THIRD
PARTY in accordance with the provisions of the applicable Third Party License
Agreement. SB agrees that [*]


                                                                         Page 17
   19
5.       DEVELOPMENT AND SUPPLY OF PRODUCT

         5.01 As of the EFFECTIVE DATE, SB shall have full control and authority
over the research, development, registration and commercialization of PRODUCT in
the FIELD in the TERRITORY, including preclinical work (e.g., pharmaceutical
development work on the final formulation) and all clinical studies, and all
such activity shall be undertaken at SB's expense, except as otherwise provided
in this AGREEMENT, specifically in Article 5. SB will exercise its reasonable
efforts and diligence in developing and commercializing PRODUCT in accordance
with its business, legal, medical and scientific judgment, and in undertaking
investigations and actions required to obtain appropriate governmental approvals
to market PRODUCT in the FIELD in the TERRITORY, such reasonable efforts and
diligence to be in accordance with the efforts and resources SB would use for a
compound owned by it or to which it has rights, which is of similar market
potential at a similar stage in its product life, taking into account the
competitiveness of the marketplace, the proprietary position of the compound,
the regulatory


                                                                         Page 18
   20
structure involved, the profitability of the applicable products,
and other relevant factors including, without limitation, technical, legal,
scientific or medical factors.

         5.02 (a) Promptly after the EFFECTIVE DATE, the parties shall form a
JOINT DEVELOPMENT COMMITTEE whose mandate shall be to direct the regulatory and
scientific development of PRODUCT necessary to receive regulatory approval for
the commercialization of PRODUCT in the FIELD in the TERRITORY. The ongoing
existence of the JOINT DEVELOPMENT COMMITTEE shall be subject to Paragraph 5.07.
Within thirty (30) days following the EFFECTIVE DATE, the parties shall each
nominate up to three (3) representatives for membership on the JOINT DEVELOPMENT
COMMITTEE. Membership shall include representation from each party's scientific,
clinical development, and regulatory affairs departments and/or representation
from such other departments as the JOINT DEVELOPMENT COMMITTEE may deem
appropriate. Each party may change its representatives on the JOINT DEVELOPMENT
COMMITTEE as it may deem necessary to reflect the stage of development or
commercialization of PRODUCT by notice to the other party. The input of the
IMMUNOGEN representatives on the JOINT DEVELOPMENT COMMITTEE shall be fully
considered by the JOINT DEVELOPMENT COMMITTEE, provided however, that all
decisions of the JOINT DEVELOPMENT COMMITTEE shall be subject to the final
approval of SB.

                  (b) Notwithstanding the JOINT DEVELOPMENT COMMITTEE, and
subject to Paragraph 5.07, the respective PRODUCT project teams from each party
shall meet as often as they may deem appropriate, either by telephone or by
meetings at appropriate locations as they may deem appropriate, to discuss each
party's respective development efforts with respect to PRODUCT. Each party shall
bear all expenses, including travel and lodging expense, that may be incurred by
its project team representatives as a result of such meetings.

                  (c) Notwithstanding any other provision of this AGREEMENT
except for Paragraph 5.07, IMMUNOGEN will have the responsibilities outlined in
APPENDIX D with respect to the development of huC242-DM1, provided that all such
responsibilities shall be conducted in strict accordance with the directions of
the JOINT DEVELOPMENT COMMITTEE, including, without limitation, seeking approval
of the JOINT DEVELOPMENT COMMITTEE in advance of initiating any of the
activities outlined in APPENDIX D, or if work is already in progress, prior to
completing the activity, seeking

                                                                         Page 19
   21
approval from the JOINT DEVELOPMENT COMMITTEE on the design of protocols and
methodologies, as well as selection of specification standards and THIRD PARTY
contractors, where appropriate. and further provided that all such
responsibilities shall be conducted at IMMUNOGEN's expense. Any approvals
required by the JOINT DEVELOPMENT COMMITTEE shall be determined in accordance
with the rules and regulations of the FDA.

                  (d) [*]

         5.03 The chairman of the JOINT DEVELOPMENT COMMITTEE shall be one of
the SB representatives on the JOINT DEVELOPMENT COMMITTEE, except that, during
the first twelve (12) months after the EFFECTIVE DATE, the JOINT DEVELOPMENT
COMMITTEE shall be co-chaired by one of the SB representatives on the JOINT
DEVELOPMENT COMMITTEE and one of the IMMUNOGEN representatives on the JOINT
DEVELOPMENT COMMITTEE. All decisions of the JOINT DEVELOPMENT COMMITTEE shall be
subject to the approval of the SB chairman (including during the period where
there is a Co-Chair from IMMUNOGEN). The JOINT DEVELOPMENT COMMITTEE shall meet
on a semi-annual basis, or more frequently if otherwise agreed, unless no later
than thirty (30) days in advance of any meeting there is a determination by the
Chairman (or Co-Chairmen during the first twelve (12) months) of the JOINT
DEVELOPMENT COMMITTEE that no new business or other activity has transpired
since the previous meeting, and that there is no need for a meeting. In such
instance, the next semi-annual meeting will be scheduled. The location of such
meetings shall alternate between IMMUNOGEN's offices in the Cambridge,
Massachusetts metropolitan area and SB's offices in the Philadelphia,
Pennsylvania metropolitan area unless otherwise agreed upon between the parties.
JOINT DEVELOPMENT COMMITTEE meetings may not necessarily be face-to-face
meetings but, upon the agreement of both parties, can be via other methods of
communication such as teleconferences and/or videoconference. Each party shall
bear all expenses, including travel and lodging expense, that may be incurred by
its JOINT DEVELOPMENT COMMITTEE representatives as a result of such meetings.
Minutes of each JOINT DEVELOPMENT COMMITTEE meeting will be transcribed and
issued to the members of the JOINT DEVELOPMENT COMMITTEE by the Chairman, or the
SB co-chair as the case


                                                                         Page 20
   22
may be, within thirty (30) days after each meeting and shall be reviewed and
modified as mutually required to obtain approval promptly thereafter. The first
meeting of the JOINT DEVELOPMENT COMMITTEE shall occur within thirty (30) days
after the EFFECTIVE DATE at a mutually acceptable location. The purpose of the
initial meeting shall be to review the current status of the development of
PRODUCT in the world, particularly the TERRITORY.

         5.04 (a) SB shall keep IMMUNOGEN informed of the progress of SB's
efforts to develop and commercialize PRODUCT in the FIELD in the TERRITORY via
the JOINT DEVELOPMENT COMMITTEE (for so long as it is in existence), and
directly through IMMUNOGEN's designated representative after the JOINT
DEVELOPMENT COMMITTEE is no longer in existence, provided that, notwithstanding
the above, in no event shall SB be obligated to disclose or transfer to
IMMUNOGEN or its designee any SB technology for the manufacture, purification,
formulation of monoclonal antibodies, or the conjugation of monoclonal
antibodies to any moiety (such as, without limitation, any radioisotope,
cytotoxic chemical, biological toxin, chemical antineoplastic or biological
antineoplastic conjugate). Nothing in this provision or any other provision of
this AGREEMENT shall be construed as a grant to IMMUNOGEN of any rights or
license with respect to any know-how owned or controlled by SB, any information
transferred to IMMUNOGEN under this AGREEMENT, or any patents, trademarks, or
other technical information owned or controlled by SB, and IMMUNOGEN warrants
and represents that it shall not transfer or disclose any such know-how,
information, patents or trademarks to any THIRD PARTY without SB's prior written
consent, except to the extent that such disclosure is required by regulatory
authorities.

                  (b) (i) IMMUNOGEN shall keep SB informed of the progress of
IMMUNOGEN's efforts (and the efforts of its licensees) to develop and
commercialize PRODUCT outside of the TERRITORY via the JOINT DEVELOPMENT
COMMITTEE to the extent that IMMUNOGEN is not prohibited from doing so by the
TAKEDA AGREEMENT. Notwithstanding any other provision of this AGREEMENT,
IMMUNOGEN warrants and represents that (a) neither it nor any of its licensees
shall begin any clinical development of PRODUCT outside of the TERRITORY until
IMMUNOGEN has received prior written approval from the JOINT DEVELOPMENT
COMMITTEE, and (b) IMMUNOGEN shall not share any KNOW-HOW or other data
generated by SB or IMMUNOGEN under this


                                                                         Page 21
   23
AGREEMENT with any THIRD PARTY who is developing and/or commercializing PRODUCT
outside of the TERRITORY.

                  (ii) In addition, IMMUNOGEN shall provide the JOINT
DEVELOPMENT COMMITTEE with summaries of the protocols for IMMUNOGEN's
preclinical and clinical studies for PRODUCT outside of the TERRITORY prior to
carrying out such studies to the extent that IMMUNOGEN is not prohibited from
doing so by the TAKEDA AGREEMENT, and IMMUNOGEN warrants and represents that it
shall not carry out any such studies until IMMUNOGEN has received prior written
approval from the JOINT DEVELOPMENT COMMITTEE.

                  (iii) In the event that IMMUNOGEN believes that the JOINT
DEVELOPMENT COMMITTEE is being unreasonable in not providing the requisite
written approval under Paragraph 5.04(b)(i) or (ii), it shall so notify SB in
writing and, at IMMUNOGEN's request, the parties shall promptly submit such
issue thereafter to a mutually acceptable THIRD PARTY who has suitable expertise
on the topic in question (hereafter "Unaffiliated Expert"), such Unaffiliated
Expert to be chosen by the parties within ten (10) business days after IMMUNOGEN
has provided such written notice to SB, and request resolution of such issue
within thirty (30) days after such submission to such Unaffiliated Expert. The
resolution of such Unaffiliated Expert shall be binding upon both parties. If
such Unaffiliated Expert determines that the JOINT DEVELOPMENT COMMITTEE was
appropriate in withholding the requisite written approval under Paragraph
5.04(b)(i) or (ii), whichever is relevant, the expenses of engaging such
Unaffiliated Expert for such determination shall be borne by IMMUNOGEN. If such
Unaffiliated Expert determines that the JOINT DEVELOPMENT COMMITTEE was not
appropriate in withholding the requisite written approval under Paragraph
5.04(b)(i) or (ii), whichever is relevant, the expenses of engaging such
Unaffiliated Expert for such determination shall be borne by SB.

              (c) IMMUNOGEN shall promptly provide SB, free of charge, via the
JOINT DEVELOPMENT COMMITTEE, with the data from all studies related to PRODUCT
to support registration of PRODUCT outside of the TERRITORY which have been
completed as of the EFFECTIVE DATE and from all future JOINT DEVELOPMENT
COMMITTEE approved studies to support registration of PRODUCT outside of the
TERRITORY to the extent that


                                                                         Page 22
   24
IMMUNOGEN is not prohibited from doing so by the TAKEDA AGREEMENT, provided that
SB shall use such data exclusively to support registration by or on behalf of SB
of PRODUCT in the FIELD in the TERRITORY, and shall otherwise keep such
information confidential according to the provisions of this AGREEMENT. In
addition, to the extent that IMMUNOGEN is not prohibited from doing so by the
TAKEDA AGREEMENT, SB shall be permitted, free of charge, to have access to
IMMUNOGEN's or its licensees' regulatory dossiers for PRODUCT outside the
TERRITORY, provided that SB shall use such dossiers exclusively to support SB's
registration files for PRODUCT in the FIELD in the TERRITORY, and shall
otherwise keep such information confidential according to the provisions of this
AGREEMENT.

         5.05 In addition to the assistance outlined in Paragraph 5.04(b), SB's
access to IMMUNOGEN's data and regulatory dossiers as outlined in Paragraph
5.04(c), and IMMUNOGEN's participation in the JOINT DEVELOPMENT COMMITTEE as
outlined in this Article 5, IMMUNOGEN shall provide to SB, at SB's request,
technical assistance within its area of expertise concerning development,
registration, production and commercialization of PRODUCT. Provision of such
technical assistance shall include, but not be limited to, visits by IMMUNOGEN
personnel to SB, [*] and visits by SB personnel to IMMUNOGEN, [*], at times and
for periods of time upon which the JOINT DEVELOPMENT COMMITTEE will agree, and
supply of any KNOW-HOW that SB may require, provided that [*].

         5.06     (a)      [*] Requirements:

                           In the event that Paragraph 5.07 is not applicable,
and the JOINT DEVELOPMENT COMMITTEE determines that [*] for [*] should be
conducted, IMMUNOGEN shall be responsible for [*] required for the [*] as 
provided in APPENDIX D, as well as [*] required for the [*] The [*] of such [*]
shall be as specified in the [*] [*] attached hereto as APPENDIX B as such may 
be modified by the JOINT DEVELOPMENT


                                                                         Page 23
   25
COMMITTEE. The form and timing of such [*] shall be as specified by IMMUNOGEN
and approved, in writing, by the JOINT DEVELOPMENT COMMITTEE. The
"Specifications" of such [*] (i.e. the [*] and [*]) shall be as determined by
IMMUNOGEN and approved, in writing, by the JOINT DEVELOPMENT COMMITTEE. [*]. Any
of such [*] held by IMMUNOGEN which is remaining after the completion of its [*]
obligations with respect to [*] [*] attached hereto as APPENDIX B [*] IMMUNOGEN
warrants and represents that:

                  (i)   [*]

                  (ii)  it will not make any commitments for [*]

                  (iii) [*]

                  (iv)  [*]

                  (v)   [*]


                                                                         Page 24
   26
SB shall be responsible, at its expense, for [*].

                  (b)      [*] Requirements:

                           Except as otherwise provided in Paragraph 5.06(a), 
[*].

         5.07 Notwithstanding any other provision of this AGREEMENT, in the
event that the [*] (as defined in Paragraph 3.01(2)) is not achieved by June 30,
1999:

                  (a) IMMUNOGEN shall thereafter have none of the
responsibilities for [*] as outlined in APPENDIX B, or for development as
outlined in APPENDIX D;

                  (b) IMMUNOGEN will immediately transfer to SB all KNOW-HOW for
PRODUCT then known to the extent that such has not already been transferred to
SB;

                  (c) IMMUNOGEN will still retain the responsibilities outlined
in Paragraphs 5.04(b), 5.04(c), and 5.05;

                  (d) the JOINT DEVELOPMENT COMMITTEE will no longer exist, and
IMMUNOGEN will interact with SB's designated representative for the purposes of
carrying out IMMUNOGEN's responsibilities outlined in Paragraphs 5.04(b),
5.04(c), and 5.05;

                  (e) the provisions of Paragraph 3.01(2)(b) shall be
applicable;

                  (f) the provisions of Paragraph 3.02(ii) shall be applicable;
and

                  (g) any PRODUCT, or components or intermediates thereof, which
were produced by or on behalf of IMMUNOGEN for the purposes of this AGREEMENT
and which are remaining and either in IMMUNOGEN's possession, or to which
IMMUNOGEN is otherwise entitled to, shall be promptly transferred to SB.

         5.08 Notwithstanding any other provision of this AGREEMENT, in the
event that the provisions of Paragraph 5.07 are not applicable, but [*] (as
defined in Paragraph 3.01(3)) is not achieved by November 30, 1999 or is not
achieved in accordance with Paragraph 3.01(3)(a):

                  (a) IMMUNOGEN shall thereafter have none of the
responsibilities for [*] as outlined in APPENDIX B, or for development as
outlined in APPENDIX D;


                                                                         Page 25
   27
                  (b) IMMUNOGEN will immediately transfer to SB all KNOW-HOW for
PRODUCT then known to the extent that such has not already been transferred to
SB;

                  (c) IMMUNOGEN will still retain the responsibilities outlined
in Paragraphs 5.04(b), 5.04(c), and 5.05;

                  (d) the JOINT DEVELOPMENT COMMITTEE will no longer exist, and
IMMUNOGEN will interact with SB's designated representative for the purposes of
carrying out IMMUNOGEN's responsibilities outlined in Paragraphs 5.04(b),
5.04(c), and 5.05;

                  (e) the provisions of Paragraphs 3.01(3)(b) shall be
applicable;

and

                  (f) any PRODUCT, or components or intermediates thereof, which
were produced by or on behalf of IMMUNOGEN and which are remaining shall be
promptly transferred to SB.

         5.09 Notwithstanding any other provision of this AGREEMENT, in the 
event that the [*] (as defined in Paragraph 3.01(2)) is achieved by June 30,
1999, IMMUNOGEN will immediately transfer to SB all KNOW-HOW including, without
limitation, all PRODUCT and process history for PRODUCT, then known to the
extent that such has not already been transferred to SB.

         5.10 Notwithstanding any other provision of this AGREEMENT, on the date
that IMMUNOGEN receives payment from SB under Paragraph 3.01(f) for [*] (as
defined in Paragraph 3.01(5)), all of IMMUNOGEN's rights and interests in the
[*] which was the subject of the [*] (as defined in Paragraph 3.01(2)) shall
immediately transfer to SB, except that IMMUNOGEN shall retain the right to use
such [*] for the purposes of fulfilling its obligations under Article 5,
APPENDIX B, and APPENDIX D.

6.       EXCHANGE OF INFORMATION AND CONFIDENTIALITY

         6.01 Promptly after the EFFECTIVE DATE, IMMUNOGEN shall disclose and
supply to SB all KNOW-HOW. Thereafter, IMMUNOGEN shall promptly disclose and
supply to SB any further KNOW-HOW which may become known to IMMUNOGEN. Such
disclosure shall include, without limitation, any improvements to huC242-DM1,
any derivatives or analogs to huC242-DM1, any KNOW-HOW relating to MAY,
including any derivatives or analogs of


                                                                         Page 26
   28
DM1, or any PRODUCT in addition to huC242-DM1 made and/or tested or otherwise
evaluated by IMMUNOGEN.

         6.02 (a) As used in this Paragraph, the term "Adverse Experience(s)"
shall mean any noxious, pathological or unintended change in anatomical,
physiological or metabolic function as indicated by physical signs, symptoms
and/or laboratory changes occurring in clinical trials, post-marketing
surveillance, or clinical practice during use of PRODUCT, or published in the
medical literature, whether or not considered causally related to PRODUCT. This
includes an exacerbation of a pre-existing condition, intercurrent illness
(i.e., a disease occurring in the course of another disease), drug interaction,
significant worsening of a disease under investigation or treatment, and
significant failure of expected pharmacological or biological action.

                  (b) For the reporting of Adverse Experiences related to
PRODUCT to regulatory authorities throughout the TERRITORY, the responsibilities
of the parties shall be performed in accordance with the pharmacovigilance
agreement attached to this AGREEMENT as APPENDIX C.

                  (c) In the event that, as a result of the TAKEDA AGREEMENT,
Takeda Chemical Industries, Ltd. decides to develop PRODUCT outside of the
TERRITORY, IMMUNOGEN shall use its commercially reasonable efforts to execute a
pharmacovigilance agreement with Takeda Chemical Industries, Ltd. which is
consistent with the terms and conditions of the pharmacovigilance agreement
attached to this AGREEMENT as APPENDIX C. Notwithstanding the above, IMMUNOGEN
acknowledges that SB will need Adverse Experience data related to PRODUCT
generated by Takeda Chemical Industries, Ltd. and its licensees outside of the
TERRITORY to enable SB to comply with the Adverse Experience reporting
requirements inside of the TERRITORY, and IMMUNOGEN warrants and represents
that, in the event that it is unable to execute the aforementioned
pharmacovigilance agreement with Takeda Chemical Industries, Ltd., IMMUNOGEN
will supply to SB, in accordance with the terms and conditions of the
pharmacovigilance agreement attached to this AGREEMENT as APPENDIX C, all
relevant Adverse Experience data related to PRODUCT generated by Takeda Chemical
Industries, Ltd. and its licensees outside of the TERRITORY to the extent that
IMMUNOGEN is able to acquire access to such data.


                                                                         Page 27
   29
         6.03 During the term of this AGREEMENT and for five (5) years 
thereafter, or ten (10) years with respect to information which is subject to 
the confidentiality obligation outlined in the P&U AGREEMENT, irrespective of 
any termination earlier than the expiration of the term of this AGREEMENT, 
IMMUNOGEN and SB shall not use or reveal or disclose to THIRD PARTIES any 
confidential information received from the other party or otherwise developed 
by either party in the performance of activities in furtherance of this 
AGREEMENT without first obtaining the written consent of the disclosing party,
except as may be otherwise provided herein, or as may be required for purposes 
of investigating, developing, manufacturing or marketing PRODUCT or for 
securing essential or desirable authorizations, privileges or rights from 
governmental agencies, or is required to be disclosed to a governmental agency 
or is necessary to file or prosecute patent applications concerning PRODUCT or 
to carry out any litigation concerning PRODUCT. This confidentiality obligation
shall not apply to such information which is or becomes a matter of public 
knowledge, or is already in the possession of the receiving party, or is 
disclosed to the receiving party by a THIRD PARTY having the right to do so, or
is subsequently and independently developed by employees of the receiving party
or AFFILIATES thereof who had no knowledge of the confidential information 
disclosed, or is required by law to be disclosed. In addition, this 
confidentiality obligation shall not apply to IMMUNOGEN with respect to any 
information transferred by SB to IMMUNOGEN under Paragraph 10.04, but only to 
the extent necessary to enable IMMUNOGEN or its subsequent PRODUCT sublicensees
to develop and/or commercialize PRODUCT in the TERRITORY. The parties shall 
take the same measures it employs internally to assure that no unauthorized use
or disclosure is made by others to whom access to such information is granted.

         6.04 Nothing herein shall be construed as preventing SB from disclosing
any information received from IMMUNOGEN to an AFFILIATE, sublicensee or
distributor of SB, provided, in the case of a sublicensee or distributor, such
sublicensee or distributor has undertaken a similar obligation of
confidentiality with respect to the confidential information.

         6.05 All confidential information disclosed by one party to the other
shall remain the intellectual property of the disclosing party. In the event
that a court or other legal or administrative tribunal, directly or through an
appointed master, trustee or receiver, assumes partial or complete control over
the assets of a party to this AGREEMENT based on the


                                                                         Page 28
   30
insolvency or bankruptcy of such party, the bankrupt or insolvent party shall
promptly notify the court or other legal or administrative tribunal or
appointee, as appropriate (i) that confidential information received from the
other party under this AGREEMENT remains the property of the other party and
(ii) of the confidentiality obligations under this AGREEMENT. In addition, the
bankrupt or insolvent party shall, to the extent permitted by law, take all
steps necessary or desirable to maintain the confidentiality of the other
party's confidential information and to ensure that the court, other tribunal or
appointee maintains such information in confidence in accordance with the terms
of this AGREEMENT.

         6.06 No public announcement or other disclosure to THIRD PARTIES
concerning the existence of or terms of this AGREEMENT shall be made, either
directly or indirectly, by any party to this AGREEMENT, except as may be legally
required or as may be required for recording purposes, without first obtaining
the written approval of the other party and agreement upon the nature and text
of such announcement or disclosure. The party desiring to make any such public
announcement or other disclosure shall inform the other party of the proposed
announcement or disclosure in reasonably sufficient time prior to public
release, and shall provide the other party with a written copy thereof, in order
to allow such other party to comment upon such announcement or disclosure. Once
any such public announcement or disclosure has been approved in accordance with
this Paragraph, then either party may appropriately communicate information
contained in such permitted announcement or disclosure, but only to the extent
disclosed, without further approval from the other party. Each party agrees that
it shall cooperate fully with the other with respect to all disclosures
regarding this AGREEMENT to the Securities Exchange Commission and any other
governmental or regulatory agencies, including requests for confidential
treatment of proprietary information of either party included in any such
disclosure. The Parties will, promptly after the EFFECTIVE DATE, agree to the
nature and text of an announcement and disclosure of the existence of this
AGREEMENT.

         6.07 IMMUNOGEN shall not submit for written or oral publication any
manuscript, abstract or the like which includes data or other information
relating to PRODUCT without first obtaining the prior written consent of SB,
which consent shall not be unreasonably withheld or delayed. The contribution of
each party shall be noted in all publications or presentations by acknowledgment
or coauthorship, whichever is appropriate. In the event that, as a result of the


                                                                         Page 29
   31
TAKEDA AGREEMENT, Takeda Chemical Industries, Ltd. decides to develop PRODUCT
outside of the TERRITORY, IMMUNOGEN shall use its commercially reasonable
efforts to bind Takeda Chemical Industries, Ltd. to a publication clause which
is consistent with this Paragraph 6.07, and in such event, IMMUNOGEN shall not
grant consent to any Takeda Chemical Industries, Ltd. publication without first
obtaining the prior written consent of SB, which consent shall not be
unreasonably withheld.

         6.08 Nothing in this AGREEMENT shall be construed as preventing or in
any way inhibiting SB from complying with statutory and regulatory requirements
governing the development, manufacture, use and sale or other distribution of
PRODUCT in any manner which it reasonably deems appropriate, including, for
example, by disclosing to regulatory authorities confidential or other
information received from IMMUNOGEN or THIRD PARTIES.

7.       PATENT PROSECUTION AND LITIGATION

         7.01 Each party shall have and retain sole and exclusive title to all
inventions, discoveries and know-how which are made, conceived, reduced to
practice or generated by its employees, agents, or other persons acting under
its authority in the course of or as a result of this AGREEMENT. Notwithstanding
the foregoing, each party shall own a fifty percent (50%) undivided interest in
all such inventions, discoveries and know-how which are made, conceived, reduced
to practice or generated jointly by employees, agents, or other persons acting
under the authority of both parties in the course of or as a result of this
AGREEMENT.

         7.02 IMMUNOGEN warrants and represents that it has disclosed to SB the
complete texts of all patent applications filed by IMMUNOGEN as of the EFFECTIVE
DATE which relate to PRODUCT as well as all information received as of the
EFFECTIVE DATE concerning the institution or possible institution of any
interference, opposition, re-examination, reissue, revocation, nullification or
any official proceeding involving a PATENT anywhere in the TERRITORY. IMMUNOGEN
further warrants and represents that it will disclose to SB the complete texts
of all patent applications filed by IMMUNOGEN after the EFFECTIVE DATE which
relate to PRODUCT as well as all information received after the EFFECTIVE DATE
concerning the institution or possible institution of any interference,
opposition, re-examination, reissue, revocation, nullification or any official
proceeding involving a PATENT anywhere in the


                                                                         Page 30
   32
TERRITORY. SB shall have the right to review all such pending applications and
other proceedings and make recommendations to IMMUNOGEN concerning them and
their conduct. IMMUNOGEN agrees to keep SB promptly and fully informed of the
course of patent prosecution or other proceedings, such as by providing SB with
copies of substantive communications, search reports and third party
observations submitted to or received from patent offices or its THIRD PARTY
licensors throughout the TERRITORY. SB shall provide such patent consultation to
IMMUNOGEN at no cost to IMMUNOGEN. SB shall hold all information disclosed to it
under this section as confidential subject to the provisions of Paragraphs 6.03
and 6.04.

         7.03 During the term of this AGREEMENT, SB shall, [*], file, prosecute
and maintain PATENTS, including those which embrace inventions outlined in
Paragraph 7.01 in which IMMUNOGEN has an ownership interest, to the extent that
such is permitted by the P&U AGREEMENT and the TAKEDA AGREEMENT. IMMUNOGEN shall
have the right, but not the obligation, to assume responsibility for any PATENT
or any part of a PATENT, at IMMUNOGEN's expense, which SB intends to abandon or
otherwise cause or allow to be forfeited. SB shall give IMMUNOGEN reasonable
written notice prior to abandonment or other forfeiture of any PATENT or any
part of a PATENT so as to permit IMMUNOGEN to exercise its rights under this
Paragraph.

         7.04 In the event of the institution of any suit by a THIRD PARTY
against IMMUNOGEN, SB, its AFFILIATES, its sublicensees or distributors for
patent infringement involving the manufacture, use, sale, distribution or
marketing of PRODUCT anywhere in the TERRITORY, the party sued shall promptly
notify the other party in writing. SB shall have the right, but not the
obligation, to defend such suit at its own expense. IMMUNOGEN and SB shall
assist one another and cooperate in any such litigation at the other's request
without expense to the requesting party, except that the requesting party shall
reimburse the other party's reasonable out-of-pocket expense (other than legal
fees or expenses) incurred by the other party in providing such assistance.

         7.05 In the event that IMMUNOGEN or SB becomes aware of actual or
threatened infringement of a PATENT anywhere in the TERRITORY, that party shall
promptly notify the other party in writing. With respect to any PATENT owned by
IMMUNOGEN, SB shall have


                                                                         Page 31
   33
the first right, but not the obligation, to bring, at its own expense, an
infringement action against any THIRD PARTY and to use IMMUNOGEN's name in
connection therewith and to name IMMUNOGEN as a party thereto. If SB does not
commence a particular infringement action within ninety (90) days of receipt of
the notice of infringement, then IMMUNOGEN, after notifying SB in writing, shall
be entitled to bring such infringement action at its own expense. The party
conducting such action shall have full control over its conduct, including
settlement thereof subject to Paragraph 7.07. In any event, IMMUNOGEN and SB
shall assist one another and cooperate in any such litigation at the other's
request without expense to the requesting party, except that the requesting
party shall reimburse the other party's reasonable out-of-pocket expense (other
than legal fees or expenses) incurred by the other party in providing such
assistance.

         7.06 In any action brought pursuant to Paragraph 7.05, the party
bringing the action shall indemnify the other party, its officers, directors,
shareholders, employees, agents, successors and assigns from any loss, damage or
liability, including attorney's fees and costs, which may result from claims,
counterclaims or crossclaims asserted by a defendant, except to the extent that
such losses, damages or liabilities result from the negligence or willful
misconduct of the other party.

         7.07 IMMUNOGEN and SB shall recover their respective actual
out-of-pocket expenses, or equitable proportions thereof, associated with any
litigation or settlement thereof from any recovery made by any party. Any excess
amount shall [*].

         7.08 The parties shall keep one another informed of the status of and
of their respective activities regarding any litigation or settlement thereof
concerning PRODUCT, provided however that no settlement or consent judgment or
other voluntary final disposition of any suit defended or action brought by a
party pursuant to this Article 7 may be entered into without the consent of the
other party if such settlement would require the other party to be subject to an


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injunction or to make a monetary payment or would otherwise adversely affect the
other party's rights under this AGREEMENT.

         7.09 SB shall have the right but not the obligation to seek extensions
of the terms of PATENTS owned by IMMUNOGEN. At SB's request, IMMUNOGEN shall
either authorize SB to act as IMMUNOGEN's agent for the purpose of making any
application for any extensions of the term of PATENTS and provide reasonable
assistance therefor to SB or shall diligently seek to obtain such extensions, 
[*].

         7.10 At SB's request, IMMUNOGEN shall seek to obtain SPCs based on
PATENTS owned by IMMUNOGEN or authorize SB to obtain SPCs based on such PATENTS
on IMMUNOGEN's behalf. Where SB holds a relevant Marketing Authorization, SB
shall provide to IMMUNOGEN a copy of said Marketing Authorization and any
information necessary for the purpose of obtaining an SPC based on a PATENT
owned by IMMUNOGEN.

         7.11 At SB's request, IMMUNOGEN shall cooperate with SB to obtain
"pipeline" protection for PATENTS owned by IMMUNOGEN which may be available
under the patent laws of countries in the TERRITORY in which the patent laws
thereof are amended to provide improved protection for PRODUCT.

8.       TRADEMARKS AND NON-PROPRIETARY NAMES

         8.01 SB shall be responsible for the selection of all trademarks which
it employs in connection with PRODUCT in the TERRITORY and shall own and control
such trademarks. SB shall be responsible for registration and maintenance of all
such trademarks. Nothing in this AGREEMENT shall be construed as a grant of
rights, by license or otherwise, to IMMUNOGEN to use such trademarks or any
other trademarks or tradenames owned by SB for any purpose. SB shall own such
tradenames and trademarks and shall retain such ownership upon termination or
expiration of this AGREEMENT.

         8.02 SB, at its expense, shall be responsible for the selection and
registration of non-proprietary names for PRODUCT in the FIELD in the TERRITORY.

9.       STATEMENTS AND REMITTANCES


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   35
         9.01 SB shall keep and require its AFFILIATES and sublicensees to keep
complete and accurate records of all sales of PRODUCT under the licenses granted
herein. IMMUNOGEN shall have the right, at IMMUNOGEN's expense, through a
certified public accountant or like person reasonably acceptable to SB, to
examine such records during regular business hours during the life of this
AGREEMENT and for six (6) months after its termination; provided, however, that
such examination shall not take place more often than once a year and shall not
cover such records for more than the preceding two (2) calendar years and
provided further that such accountant shall report to IMMUNOGEN only as to the
accuracy of the royalty statements and payments.

         9.02 Within [*] days after the end of each quarter, SB shall provide a
true accounting of all PRODUCT sold by SB, its AFFILIATES and its sublicensees
in the FIELD during such quarter in the TERRITORY, and SB shall, at the same
time, pay any royalties due for such quarter under Article 3, subject to any
credits which may be due SB under Paragraph 4.02(a) and 4.02(c). Such accounting
shall show sales on a country-by-country and PRODUCT-by-PRODUCT basis.

         9.03 Any tax, duty or other levy paid or required to be withheld by SB
on account of royalties payable to IMMUNOGEN under this AGREEMENT shall be
deducted from the amount of royalties otherwise due. SB shall secure and send to
IMMUNOGEN proof of any such taxes, duties or other levies withheld and paid by
SB or its sublicensees for the benefit of IMMUNOGEN, and shall cooperate with
IMMUNOGEN in seeking relief from any such taxes or other levies to the extent
legally permissible and without prejudice to SB.

         9.04 All royalties and other payments due under this AGREEMENT shall be
payable in U.S. Dollars. If governmental regulations prevent remittances from a
foreign country with respect to sales made in that country, the obligation of SB
to pay royalties on sales in that country shall be suspended until such
remittances are possible. IMMUNOGEN shall have the right, upon giving written
notice to SB, to receive payment in that country in local currency.

         9.05 Monetary conversion from the currency of a foreign country, in
which PRODUCT is sold, into U.S. Dollars shall be calculated at the actual
average rates of exchange for the year to date as used by SB in producing its
quarterly and annual accounts, as confirmed by SB's auditors.


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   36
         9.06 Without limiting IMMUNOGEN's other remedies under this AGREEMENT
or otherwise, in the event that any payment due hereunder is not made within the
time period provided under this AGREEMENT, the payment shall accrue interest
beginning upon the first day following the end of such time period, calculated
at the average annual prime rate or equivalent rate quoted by Citibank N.A. on
the day after the end of such time period.

10.      TERM AND TERMINATION

         10.01 (a) Subject to Paragraph 3.07, royalty obligations under
Paragraph 3.02 in each country of the TERRITORY shall expire upon [*].
Expiration of SB's royalty obligations under Paragraph 3.02 for a particular
PRODUCT under this provision shall not preclude SB from continuing to market
such PRODUCT and to use KNOW-HOW in such country without further royalty
payments or any other remuneration to IMMUNOGEN, except to the extent that
Paragraph 3.03 is still applicable to the NET SALES of the particular PRODUCT in
the particular country.

                  (b) Royalty obligations under Paragraph 3.03 in each country
shall expire upon the earlier of: (1) [*] from the date of LAUNCH in such
country, or (2) in those countries which are member states of the European
Union, when all KNOW-HOW used by SB in the making, using or selling of PRODUCT
has become publicly known otherwise than through the fault of SB or an
undertaking connected therewith. Expiration of SB's royalty obligations for a
particular PRODUCT under this provision shall not preclude SB from continuing to
market such PRODUCT and to use KNOW-HOW in such country without further royalty
payments or any other remuneration to IMMUNOGEN. Expiration of SB's royalty
obligations in a particular country of the TERRITORY shall constitute an
expiration of this AGREEMENT in such country.

         10.02 Unless otherwise terminated, this AGREEMENT shall expire in its
entirety upon the later of (a) [*], or (b) [*] from the date of LAUNCH in the 
last country in the TERRITORY in which the PRODUCT is marketed by SB .
Expiration of this AGREEMENT under this provision shall not preclude SB from
continuing to make, have made,


                                                                         Page 35
   37
use and sell PRODUCT and to use KNOW-HOW in the TERRITORY without further
royalty payments or any other remuneration to IMMUNOGEN.

         10.03 If either party fails or neglects to perform covenants or
provisions of this AGREEMENT and if such default is not corrected within [*]
days after receiving written notice from the other party with respect to such
default, such other party shall have the right to terminate this AGREEMENT by
giving written notice to the party in default provided the notice of termination
is given within [*] of the date the non-breaching party became aware of the
default and prior to correction of the default.

         10.04 (a) SB may terminate this AGREEMENT on a country by country
basis, or in its entirety, by giving IMMUNOGEN at least [*] written notice
thereof at any time before LAUNCH of PRODUCT in such country by or on behalf of
SB based on a reasonable determination by SB, using the same standards SB would
use in assessing whether or not to continue development and marketing of a
product of its own making, that the patent, medical/scientific, technical,
regulatory or commercial profile of PRODUCT does not justify continued
development or marketing of any PRODUCT in such country.

                  (b) After LAUNCH of PRODUCT by or on behalf of SB in a
particular country of the TERRITORY, SB may terminate this AGREEMENT in such
country or in its entirety, by giving IMMUNOGEN at least [*] prior written
notice thereof based on a reasonable determination by SB, using the same
standards SB would use in assessing whether or not to continue development and
marketing of a product of its own making, that the patent, medical/scientific,
technical, regulatory or commercial profile of every PRODUCT does not justify
continued development or marketing of any PRODUCT in such country.

                  (c) In the event that SB terminates this AGREEMENT in any
country of the TERRITORY in accordance with Paragraph 10.04(a) or 10.04(b), SB
shall,[*] after the effective date of such termination, [*]


                                                                         Page 36
   38

[*]








                                                                         Page 37
   39
[*]
                  (d) In the event that SB has terminated this AGREEMENT under
Paragraph 10.04(b) in one or more countries of the TERRITORY, and IMMUNOGEN
wants to obtain rights to SB technology related to the manufacture,
purification, formulation of monoclonal antibodies, or the conjugation of
monoclonal antibodies to any moiety (such as, without limitation, any
radioisotope, cytotoxic chemical, biological toxin, chemical antineoplastic or
biological antineoplastic conjugate), and/or IMMUNOGEN wants SB to supply
PRODUCT to IMMUNOGEN in such countries, IMMUNOGEN shall provide written
notification to SB, together with a proposal regarding the terms and conditions
for obtaining such rights and/or supply. SB shall seriously consider IMMUNOGEN's
proposal, but shall have no obligation to grant such rights or provide such
supply under the terms and conditions of IMMUNOGEN's proposal or any other terms
and conditions.

         10.05 Either party may terminate this AGREEMENT if, at any time, the
other party shall file in any court or agency pursuant to any statute or
regulation of any state or country, a petition in bankruptcy or insolvency or
for reorganization or for an arrangement or for the appointment of a receiver or
trustee of the party or of its assets, or if the other party proposes a written
agreement of composition or extension of its debts, or if the other party shall
be served with an involuntary petition against it, filed in any insolvency
proceeding, and such petition shall not be dismissed within [*] after the filing
thereof, or if the other party shall propose or be a party to any dissolution or
liquidation, or if the other party shall make an assignment for the benefit of
creditors.

         10.06 Notwithstanding the bankruptcy of IMMUNOGEN, or the impairment of
performance by IMMUNOGEN of its obligations under this AGREEMENT as a result of
bankruptcy or insolvency of IMMUNOGEN, SB shall be entitled to retain the
licenses granted herein, subject to IMMUNOGEN's rights to terminate this
AGREEMENT for reasons other than bankruptcy or insolvency as expressly provided
in this AGREEMENT.

         10.07 All rights and distribution rights granted under or pursuant to
this AGREEMENT by IMMUNOGEN to SB are, and shall otherwise be deemed to be, for
purposes of Section


                                                                         Page 38
   40
365(n) of the U.S. Bankruptcy Code, licenses of rights to "intellectual
property" as defined under Section 101(52) of the U.S. Bankruptcy Code. The
parties agree that SB, as a licensee of such rights under this AGREEMENT, shall
retain and may fully exercise all of its rights and elections under the U.S.
Bankruptcy Code, subject to performance by SB of its preexisting obligations
under this AGREEMENT. The parties further agree that, in the event of the
commencement of a bankruptcy proceeding by or against IMMUNOGEN under the U.S.
Bankruptcy Code, SB shall be entitled to a complete duplicate of (or complete
access to, as appropriate) any such intellectual property and all embodiments of
such intellectual property, and same, if not already in its possession, shall be
promptly delivered to SB (a) upon any such commencement of a bankruptcy
proceeding upon written request therefor by SB, unless IMMUNOGEN elects to
continue to perform all of its obligations under this AGREEMENT, or (b) if not
delivered under (a) above, upon the rejection of this AGREEMENT by or on behalf
of IMMUNOGEN upon written request therefor by SB, provided, however, that upon
IMMUNOGEN's (or its successor's) written notification to SB that it is again
willing and able to perform all of its obligations under this AGREEMENT, SB
shall promptly return all such tangible materials to IMMUNOGEN, but only to the
extent that SB does not require continued access to such materials to enable SB
to perform its obligations under this AGREEMENT.

11.      RIGHTS AND DUTIES UPON TERMINATION

         11.01 Upon termination of this AGREEMENT, IMMUNOGEN shall have the
right to retain any sums already paid by SB hereunder, and SB shall pay all sums
accrued hereunder prior to the date of any such termination.

         11.02 Upon termination of this AGREEMENT in its entirety or with
respect to any PRODUCT in any country under Paragraphs 10.03, 10.04, or 10.05,
SB shall notify IMMUNOGEN of the amount of PRODUCT SB, its AFFILIATES,
sublicensees and distributors then have on hand, the sale of which would, but
for the termination, be subject to royalty, and SB, its AFFILIATES, sublicensees
and distributors shall thereupon be permitted to sell that amount of PRODUCT
provided that SB shall pay the royalty thereon at the time herein provided for.


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         11.03 Termination of this AGREEMENT in its entirety shall terminate all
outstanding obligations and liabilities between the parties arising from this
AGREEMENT except those described in Paragraphs 6.02, 6.03 (to the extent
provided therein), 6.04, 6.05, 6.06, 6.07 (for data or information developed
during the term of the AGREEMENT), 6.08, 7.01, 7.02 (1st, 2nd and 5th sentences
only), 7.04 (for suits which arise with respect to activities which occurred
during the term of the AGREEMENT), 7.05 (for alleged or actual infringement
activities which occurred during the term of the AGREEMENT), 7.06, 7.07, 7.08,
10.04(c) and 10.04(d), and in Articles 8, 9, 11, 12, 13, 14, 15, 16, 17, 18, 19,
20, 21 and 22. In addition, any other provision required to interpret and
enforce the parties' rights and obligations under this AGREEMENT shall also
survive, but only to the extent required for the full observation and
performance of this AGREEMENT.

         11.04 Termination of this AGREEMENT in accordance with the provisions
hereof shall not limit remedies which may be otherwise available in law or
equity.

12.      WARRANTIES, REPRESENTATIONS, INDEMNIFICATIONS
         AND INSURANCE

         12.01 IMMUNOGEN warrants and represents that it owns the entire right,
title and interest, or otherwise has the right to grant the licenses to SB
contemplated in this AGREEMENT, in the PATENTS listed in APPENDIX A, or filed by
or on behalf of IMMUNOGEN pursuant to Article 7, and the KNOW-HOW provided to SB
under this AGREEMENT, and that it otherwise has the right to enter into this
AGREEMENT. IMMUNOGEN further warrants and represents that it has not and will
not encumber its ownership interest in any such PATENTS and KNOW-HOW with liens,
mortgages, security interests or otherwise. IMMUNOGEN further warrants and
represents that there is nothing in any THIRD PARTY agreement IMMUNOGEN has
entered into as of the EFFECTIVE DATE which, in any way, will limit IMMUNOGEN's
ability to perform all of the obligations undertaken by IMMUNOGEN hereunder, and
that it will not enter into any AGREEMENT after the EFFECTIVE DATE under which
IMMUNOGEN would incur any such limitations.

         12.02    IMMUNOGEN warrants and represents that it:


                                                                         Page 40
   42
                  (a) has received any consent required under the P&U AGREEMENT,
the IRL AGREEMENT, and the TAKEDA AGREEMENT, and any other agreement that
IMMUNOGEN may have with a THIRD PARTY to grant the licenses to SB contemplated
by this AGREEMENT and to perform its obligations to SB under this AGREEMENT;

                  (b) shall pay all royalties or other sums and other payments
which IMMUNOGEN may owe by virtue of this AGREEMENT under the P&U AGREEMENT
(except as otherwise provided in Paragraph 4.02(a)(i)(a)), the IRL AGREEMENT,
the TAKEDA AGREEMENT, and any agreement that IMMUNOGEN may have with a THIRD
PARTY, and shall perform and observe all of the other obligations outlined in
the P&U AGREEMENT, the IRL AGREEMENT, and the TAKEDA AGREEMENT, and any and all
present and future agreements between IMMUNOGEN and a THIRD PARTY which are in
any way related to IMMUNOGEN's ability to grant the rights granted to SB under
this AGREEMENT or to IMMUNOGEN's ability to perform its obligations to SB under
this AGREEMENT; and

                  (c) has received no notices that IMMUNOGEN is in breach of its
obligations under P&U AGREEMENT, the IRL AGREEMENT, the TAKEDA AGREEMENT or any
agreements IMMUNOGEN may have with any other THIRD PARTY which are in any way
related to IMMUNOGEN's ability to grant the rights granted to SB under this
AGREEMENT or to IMMUNOGEN's ability to perform its obligations to SB under this
AGREEMENT. In the event that IMMUNOGEN receives notice from any such THIRD PARTY
that IMMUNOGEN has committed a breach of its obligations under any such
agreement, or if IMMUNOGEN anticipates such breach, such as may give rise to a
right by such THIRD PARTY to diminish IMMUNOGEN's ability to grant rights to SB
contemplated by this AGREEMENT, or otherwise diminish IMMUNOGEN's ability to
perform its obligations to SB under this AGREEMENT, IMMUNOGEN shall immediately
notify SB of such situation, and IMMUNOGEN shall promptly cure such breach.
However, if IMMUNOGEN is unable to cure such breach, IMMUNOGEN shall, to the
extent possible, permit SB to cure such breach and to negotiate directly with
such THIRD PARTY.

         12.03 Nothing in this AGREEMENT shall be construed as a warranty that
PATENTS are valid or enforceable. IMMUNOGEN hereby warrants and represents that,
to the best of its knowledge and belief, PATENTS are not invalid. IMMUNOGEN
further warrants and


                                                                         Page 41
   43
represents that, to the best of its knowledge and belief, and to the extent not
disclosed to SB as of the EFFECTIVE DATE, the process by which it manufactures
PRODUCT, and all intermediates of such process, will not infringe patent rights
of THIRD PARTIES in both the country in which the PRODUCT is produced as well as
all countries of the TERRITORY.

         12.04 IMMUNOGEN acknowledges that, in entering into this AGREEMENT, SB
has relied or will rely upon information supplied by IMMUNOGEN, information to
be supplied by IMMUNOGEN, and information which IMMUNOGEN has caused or will
cause to be supplied to SB by IMMUNOGEN's agents, representatives and/or
licensees, pursuant to the Confidentiality Agreement, dated October 21, 1997,
between the parties, and Article 6 hereof, and IMMUNOGEN warrants and represents
that, to the best of its knowledge and belief, all such information is and will
be timely and accurate in all material respects. IMMUNOGEN further warrants and
represents that, to the best of its knowledge and belief, it has not, up through
and including the EFFECTIVE DATE, omitted to furnish SB with any information
concerning PRODUCT or the transactions contemplated by this AGREEMENT, which
would be material to SB's decision to enter into this AGREEMENT and to undertake
the commitments and obligations set forth herein.

         12.05 IMMUNOGEN warrants and represents that it has no present
knowledge of the existence of any pre-clinical or clinical data or information
concerning the PRODUCT which has caused IMMUNOGEN to believe that there may
exist quality, toxicity, safety and/or efficacy concerns which may materially
impair the utility and/or safety of the PRODUCT.

         12.06 SB hereby agrees to save, defend and hold IMMUNOGEN, its
AFFILIATES and their respective officers, directors, shareholders,
representatives, agents, employees, successors and assigns harmless from and
against any and all suits, claims, actions, demands, liabilities, expenses
and/or losses, including reasonable legal expense and attorneys' fees, brought
by a THIRD PARTY or that arise in connection with any claim brought by a THIRD
PARTY with respect to the PRODUCT ("Losses"), except to the extent such Losses
result from (i) the negligence or willful misconduct of IMMUNOGEN or breach by
IMMUNOGEN of any provision, term, representation or warranty contained in this
AGREEMENT, or (ii) IMMUNOGEN's manufacture (including its manufacture through
THIRD PARTY suppliers) of PRODUCT.


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   44
         12.07 IMMUNOGEN hereby agrees to save, defend and hold SB, its
AFFILIATES and their respective officers, directors, shareholders,
representatives, agents, employees, successors and assigns harmless from and
against any and all suits, claims, actions, demands, liabilities, expenses
and/or losses, including reasonable legal expense and attorneys' fees, brought
by a THIRD PARTY or that arise in connection with any claim brought by a THIRD
PARTY with respect to the PRODUCT ("Losses"), but only to the extent such Losses
result from (i) the negligence or willful misconduct of IMMUNOGEN or breach by
IMMUNOGEN of any provision, term, representation or warranty contained in this
AGREEMENT, or (ii) IMMUNOGEN's manufacture (including its manufacture through
THIRD PARTY suppliers) of PRODUCT.

         12.08    Indemnification Procedure.

                  (a) In the event IMMUNOGEN is seeking indemnification from SB
under Paragraph 12.06, SB shall have no such obligation unless IMMUNOGEN:

                      (i) gives SB prompt notice of any claim or lawsuit or
other action for which it seeks to be indemnified under this AGREEMENT;

                      (ii) cooperates fully with SB and its agents in defense of
any such claim, complaint, lawsuit or other cause of action; and

                      (iii) SB is granted full authority and control over the
defense, including settlement or other disposition thereof, against such claim
or lawsuit or other action, provided that IMMUNOGEN shall have the right to
retain counsel of its choice to participate in the defense of any such claim or
lawsuit at IMMUNOGEN's own expense, provided that such counsel shall not
interfere with SB's full authority and control.

                  (b) In the event SB is seeking indemnification from IMMUNOGEN
under Paragraph 12.07, IMMUNOGEN shall have no such obligation unless SB:

                      (i) gives IMMUNOGEN prompt notice of any claim or lawsuit
or other action for which it seeks to be indemnified under this AGREEMENT;

                      (ii) cooperates fully with IMMUNOGEN and its agents in
defense of any such claim, complaint, lawsuit or other cause of action; and

                      (iii) IMMUNOGEN is granted full authority and control over
the defense, including settlement or other disposition thereof, against such
claim or lawsuit or


                                                                         Page 43
   45
other action, provided that SB shall have the right to retain counsel of its
choice to participate in the defense of any such claim or lawsuit at SB's own
expense, provided that such counsel shall not interfere with IMMUNOGEN's full
authority and control.

         12.09 Prior to or immediately upon the first administration of PRODUCT
prepared by IMMUNOGEN under this AGREEMENT to a human in accordance with this
AGREEMENT, and for a period of five (5) years after the expiration of this
AGREEMENT or earlier termination, each party shall obtain and/or maintain,
respectively, at its sole cost and expense, product liability insurance in
amounts, respectively, which are reasonable and customary in the U.S.
pharmaceutical industry for companies of comparable size and activities at the
respective place of business of each party. Such product liability insurance
shall insure against all liability, including liability for personal injury,
physical injury and property damage. Each party shall provide written proof of
the existence of such insurance to the other party upon request.

13.      FORCE MAJEURE

         13.01 If the performance of any part of this AGREEMENT by either party,
or of any obligation under this AGREEMENT, is prevented, restricted, interfered
with or delayed by reason of any cause beyond the reasonable control of the
party liable to perform, unless conclusive evidence to the contrary is provided,
the party so affected shall, upon giving written notice to the other party, be
excused from such performance to the extent of such prevention, restriction,
interference or delay, provided that the affected party shall use its reasonable
best efforts to avoid or remove such causes of non-performance and shall
continue performance with the utmost dispatch whenever such causes are removed.
When such circumstances arise, the parties shall discuss what, if any,
modification of the terms of this AGREEMENT may be required in order to arrive
at an equitable solution.

14.      GOVERNING LAW

         14.01 This AGREEMENT shall be deemed to have been made in the
Commonwealth of Pennsylvania, U.S.A. and its form, execution, validity,
construction and effect shall be determined in accordance with the laws of the
Commonwealth of Pennsylvania, U.S.A.


                                                                         Page 44
   46
         14.02 Subject to Paragraph 5.04(b)(iii) and Paragraph 3.01(2)(c), any
dispute, controversy or claim arising out of or relating to this AGREEMENT
(hereinafter collectively referred to as "Dispute") shall be attempted to be
settled by the parties, in good faith, by submitting each such Dispute to
appropriate senior management representatives of each party in an effort to
effect a mutually acceptable resolution thereof. In the event no mutually
acceptable resolution of such Dispute is achieved in accordance with Paragraph
14.02 within a reasonable period of time, then either party shall be entitled to
seek final settlement of such Dispute by any administrative or judicial
mechanism which may be available.

15.      WAIVER OF BREACH

         15.01 The failure of either party at any time or times to require
performance of any provision hereof shall in no manner affect its rights at a
later time to enforce the same. No waiver by either party of any condition or
term in any one or more instances shall be construed as a further or continuing
waiver of such condition or term or of another condition or term.

16.      SEPARABILITY

         16.01 In the event any portion of this AGREEMENT shall be held illegal,
void or ineffective, the remaining portions hereof shall remain in full force
and effect.

         16.02 If any of the terms or provisions of this AGREEMENT are in
conflict with any applicable statute or rule of law, then such terms or
provisions shall be deemed inoperative to the extent that they may conflict
therewith and shall be deemed to be modified to conform with such statute or
rule of law.

         16.03 In the event that the terms and conditions of this AGREEMENT are
materially altered as a result of Paragraphs 16.01 or 16.02, the parties will
renegotiate the terms and conditions of this AGREEMENT to resolve any
inequities.

17       ENTIRE AGREEMENT

         17.01 This AGREEMENT, entered into as of the date written above,
constitutes the entire agreement between the parties relating to the subject
matter hereof and supersedes all previous writings and understandings. No terms
or provisions of this AGREEMENT shall be


                                                                         Page 45
   47
varied or modified by any prior or subsequent statement, conduct or act of
either of the parties, except that the parties may amend this AGREEMENT by
written instruments specifically referring to and executed in the same manner as
this AGREEMENT.

18.      NOTICES

         18.01 Notices required or permitted under this AGREEMENT shall be in
writing and sent by prepaid registered or certified air mail or by overnight
express mail (e.g., FedEx), or by facsimile confirmed by prepaid registered or
certified air mail letter or by overnight express mail (e.g., FedEx), and shall
be deemed to have been properly served to the addressee upon receipt of such
written communication, to the following addresses of the parties:

                  If to IMMUNOGEN:

                  ImmunoGen, Inc.
                  333 Providence Highway
                  Norwood, Massachusetts 02062

                  Attention:  Chief Executive Officer

                           copy to:

                           Mintz, Levin, Cohn, Ferris, Glovsky and Popeo PC
                           One Financial Center
                           Boston, Massachusetts   02111
                           Attention:  Jeffrey M. Wiesen, Esq.

                  If to SB:

                  SmithKline Beecham Corporation
                  One Franklin Plaza (Mail Code FP1935)
                  P.O. Box 7929
                  Philadelphia, Pennsylvania 19101
                  U.S.A.


                  Attention: Senior Vice President, Business Development

                           copy to:

                           SmithKline Beecham Corporation
                           One Franklin Plaza (Mail Code FP2360)
                           P.O. Box 7929
                           Philadelphia, Pennsylvania 19101, U.S.A.
                                                                         Page 46
   48
                           Attention:  Corporate Law-U.S.

19.      ASSIGNMENT

         19.01 This AGREEMENT and the licenses herein granted shall be binding
upon and inure to the benefit of the successors in interest of the respective
parties. Neither this AGREEMENT nor any interest hereunder shall be assignable
by either party without the written consent of the other, which consent shall
not be unreasonably withheld; provided, however, that (a) SB may assign this
AGREEMENT or any part of its rights and obligations hereunder, or any PATENT
owned by it, to any AFFILIATE of SB or to any corporation with which SB may
merge or consolidate, or to which it may transfer all or substantially all of
its assets to which this AGREEMENT relates, without obtaining the consent of
IMMUNOGEN, and (b) after IMMUNOGEN has completed its obligations outlined in
Article 5, IMMUNOGEN may assign this AGREEMENT or any part of its rights and
obligations hereunder, or any PATENT owned by it, to any AFFILIATE of IMMUNOGEN
or to any corporation with which IMMUNOGEN may merge or consolidate, or to which
it may transfer all or substantially all of its assets to which this AGREEMENT
relates, without obtaining the consent of SB.

20.      RELATIONSHIP BETWEEN THE PARTIES.

         20.01 Both parties are independent contractors under this AGREEMENT.
Nothing contained in this AGREEMENT is intended nor shall be construed so as to
constitute IMMUNOGEN or SB as partners or joint venturers with respect to this
AGREEMENT. Neither party shall have the express or the implied right nor
authority to assume or create any obligations on behalf of or in the name of the
other party, nor to bind the other party to any other contract, agreement or
undertaking with any THIRD PARTY.

21.      NO INTELLECTUAL PROPERTY RIGHTS GRANTED.

         21.01 No rights or licenses with respect to a party's patents,
trademarks, know-how, technical information, or other proprietary rights are
granted or deemed granted to the other party hereunder or in connection
herewith, other than those rights expressly granted in this AGREEMENT.


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22.      RECORDING

         22.01 SB shall have the right, at any time, to record, register, or
otherwise notify this AGREEMENT in appropriate governmental or regulatory
offices anywhere in the TERRITORY, and IMMUNOGEN shall provide reasonable
assistance to SB in effecting such recording, registering or notifying.

23.      EXECUTION IN COUNTERPARTS

         23.01 This AGREEMENT may be executed in any number of counterparts,
each of which shall be deemed an original but all of which together shall
constitute one and the same instrument.



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         IN WITNESS WHEREOF, the parties, through their authorized officers,
have executed this AGREEMENT as of the date first written above.

SMITHKLINE BEECHAM CORPORATION

BY: /s/ Jean-Pierre Garnier
    ----------------------------

TITLE: COO
      --------------------------

IMMUNOGEN, INC.

BY: /s/ Mitchel Sayare
   -----------------------------

TITLE: CEO
      --------------------------




                                                                         Page 49
   51
                                LICENSE AGREEMENT
                 SMITHKLINE BEECHAM CORPORATION- IMMUNOGEN, INC.
                                   APPENDIX A
                                     PATENTS
                                       [*]
   52
                                LICENSE AGREEMENT
                 SMITHKLINE BEECHAM CORPORATION-IMMUNOGEN, INC.
                                   APPENDIX B
                                       [*]
   53
                                LICENSE AGREEMENT
                 SMITHKLINE BEECHAM CORPORATION-IMMUNOGEN, INC.
                                   APPENDIX C
                           PHARMACOVIGILANCE AGREEMENT
              PROCEDURE FOR EXCHANGE OF ADVERSE EVENT DATA BETWEEN
    SB WORLDWIDE CLINICAL SAFETY AND IMMUNOGEN FOR PRODUCT (E.G., HUC242-DM1)



BACKGROUND
huC242-DM1 is a conjugated antibody being co-developed by SB and IMMUNOGEN. [*]
and SB will [*] excluding those territories held by other IMMUNOGEN licensing
partners. [*].


DEFINITIONS
The following definitions reflect and are consistent with FDA and International
Conference on Harmonization (ICH) regulations/guidelines.

- -   ADVERSE EXPERIENCE (AE)
    The ICH has defined an AE as "any untoward medical occurrence in a patient
    or clinical investigation subject administered a pharmaceutical product and
    which does not necessarily have to have a causal relationship with this
    treatment."

- -   ADVERSE DRUG REACTION (ADR)
    In the pre-approval clinical experience or in other clinical trial
    experiences The ICH has defined an ADR in clinical trials as "all noxious
    and unintended responses to a medical product related to any dose".

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   54
    The phrase "responses to a medicinal product" means that a causal
    relationship between a medicinal product and an adverse event is at least a
    reasonable possibility, i.e. the relationship cannot be ruled out.

- -   UNEXPECTED ADR
    The ICH has defined an unexpected ADR as "an adverse reaction, the nature or
    severity of which is not consistent with the applicable product information
    (e.g. Investigator Brochure) for an unapproved investigational medicinal
    product.

    This definition includes an AE/adr of which the nature, specificity, or
    severity is inconsistent with the applicable product information. For an
    AE/ADR from a clinical trial, the reference document shall be the
    Investigator Brochure.

- -        SERIOUS AE OR SERIOUS ADR
         A serious AE or ADR is any untoward medical occurrence that:
         *        results in death
         *        is life-threatening
                  NOTE: The term "life-threatening" in the definition of
                  "serious" refers to an event in which the patient was at risk
                  of death at the time of the event; it does not refer to an
                  event which hypothetically might have caused death if it were
                  more severe.
         *        requires inpatient hospitalization or prolongation of 
                  existing hospitalization
         *        results in persistent or significant disability/incapacity, or
         *        is a congenital anomaly/birth defect.
         Medical and scientific judgment should be exercised in deciding whether
         expedited reporting is appropriate in other situations, such as
         important medical events that may not be immediately life-threatening
         or result in death or hospitalization but may jeopardize the patient or
         may require intervention to prevent one of the other outcomes listed in
         the definition above. These should also usually be considered serious.
         (Examples of such events are intensive treatment in an emergency room
         or at home for allergic bronchospasm; blood dyscrasias or convulsions
         that do not result in hospitalization; or development of drug
         dependency or drug abuse.)

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   55
- -        NON-SERIOUS AE
         A non-serious AE is any experience which does not meet the definition 
         of serious as defined above.

         Clinical trial experiences which are not considered "serious" include:
         hospitalization for a pre-planned/elective procedure for a medical
         condition present before treatment started; a pre-existing medical
         condition which does not increase in severity or frequency following
         treatment; or an experience which is simply a treatment failure
         according to the efficacy criteria for the study.

REPORTING
- -        REPORTS OF PREGNANCY AND OVERDOSE
         While such reports are not AEs or ADRs as defined herein, reports of
         pregnancies should be followed up until the outcome of the pregnancy is
         known. "Overdose" will be defined as any dose that the reporter
         indicates was an overdose.

- -        MINIMUM CRITERIA FOR REPORTING
         Initial reports should be submitted within the agreed timelines as long
         as the following minimum criteria are met: 
                  an identifiable patient; a suspect medicinal product; an
                  identifiable reporting source; and an event or outcome

- -        FOLLOW-UP OF CASES
         Follow-up information should be actively sought by the party conducting
         the trial and submitted within the same timelines as an initial report.

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POLICY
- -        SB will hold the recognized worldwide safety database for huC242-DM1.
- -        SB is responsible for regulatory reporting in the TERRITORY and 
         IMMUNOGEN is responsible for regulatory reporting outside of the
         TERRITORY.
- -        [*]
- -        [*]
- -        If either party becomes aware of a safety issue they will immediately
         inform the other party.
- -        Each party will inform the other party of any safety related queries
         from a regulatory authority.
- -        This agreement will be updated periodically in response to regulatory
         changes, at the request of either party, or once one party gains
         marketing approval for huC242-DM1.


DATA EXCHANGE
- -        Data will be transferred in English by fax.
- -        IMMUNOGEN is responsible for receiving and forwarding reports to and
         from other IMMUNOGEN licensees (if applicable)
- -        SB is responsible for receiving and forwarding reports to and from
         other SB sub-licensees (if applicable)

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   57
- -        SB WILL SEND IMMUNOGEN WRITTEN NOTICE OF:

         *        Fatal and life-threatening events which are unexpected and
                  considered possibly drug related by fax within 24 hours of
                  receipt
         *        All other serious adverse events within 5 days
         *        Copies of end of study reports

- -        IMMUNOGEN WILL SEND TO SB WRITTEN NOTICE OF:
         *        Fatal and life-threatening events which are unexpected and
                  considered possibly drug related by fax within 24 hours of
                  receipt
         *        All other serious adverse events within 5 days
         *        Copies of end of study reports
         *        Copies of any investigator letters generated while IMMUNOGEN
                  hold the IND for the compound

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PHARMACOVIGILANCE CONTACTS IN EACH PARTY:


    FOR SMITHKLINE BEECHAM:                 CONTACT ADDRESS AND NUMBERS:

    [*]











    FOR IMMUNOGEN:                          CONTACT ADDRESS AND NUMBERS:

    [*]

                                                                         Page 60
   59
                                LICENSE AGREEMENT
                 SMITHKLINE BEECHAM CORPORATION-IMMUNOGEN, INC.
                                   APPENDIX D
         IMMUNOGEN DEVELOPMENT RESPONSIBILITIES UNDER PARAGRAPH 5.02(C)

[*]

                                                                         Page 61
   60
                                LICENSE AGREEMENT
                 SMITHKLINE BEECHAM CORPORATION-IMMUNOGEN, INC.
                                   APPENDIX E
[*]

                                                                         Page 64