Exhibit 4.1


 


IMMUNOGEN, INC.


 


PRE-FUNDED
WARRANT TO PURCHASE COMMON STOCK


 


Number of Shares: [●]

(subject to adjustment)


 


	Warrant No. [●]	 	     Original Issue
    Date: December 6, 2021




 


ImmunoGen, Inc., a Massachusetts corporation
(the “Company”), hereby certifies that, for good and valuable consideration, the receipt and sufficiency of which
are hereby acknowledged, [●] or its permitted registered assigns (the “Holder”), is entitled, subject to the
terms set forth below, to purchase from the Company up to a total of [●] shares of common stock, $0.01 par value per share (the
 “Common Stock”), of the Company (each such share, a “Warrant Share” and all such shares, the “Warrant
Shares”) at an exercise price per share equal to $0.01 per share (as adjusted from time to time as provided in Section 9
herein, the “Exercise Price”), upon surrender of this Pre-Funded Warrant to Purchase Common Stock (including any Warrants
to Purchase Common Stock issued in exchange, transfer or replacement hereof, the “Warrant”) at any time and from time
to time on or after the date hereof (the “Original Issue Date”), and subject to the following terms and conditions:


 


		1.	Definitions. For purposes of this Warrant, the following terms
                                            shall have the following meanings:



 


		(a)	“Affiliate” means any Person directly or indirectly
                                            controlled by, controlling, or under common control with, a Holder, but only for so long
                                            as such control shall continue. For purposes of this definition, “control” (including,
                                            with correlative meanings, “controlled by,” “controlling” and “under
                                            common control with”) means, with respect to a Person, possession, direct or indirect,
                                            of (a) the power to direct or cause direction of the management and policies of such
                                            Person (whether through ownership of securities or partnership or other ownership interests,
                                            by contract or otherwise), or (b) at least 50% of the voting securities (whether directly
                                            or pursuant to any option, warrant, or other similar arrangement) or other comparable equity
                                            interests.



 


		(b)	“Commission” means the United States Securities
                                            and Exchange Commission.



 


		(c)	“Exchange Act” means the Securities Exchange
                                            Act of 1934, as amended.



 


		(d)	“Principal Trading Market” means the national
                                            securities exchange or other trading market on which the Common Stock is primarily listed
                                            and quoted for trading, which, as of the Original Issue Date, shall be The Nasdaq Global
                                            Select Market.



 


		(e)	“Registration Statement” means the Company’s
                                            registration statement on Form S-3 (File No. 333-251502), which was filed, and
                                            became effective, on December 18, 2020.



 


		(f)	“Securities Act” means the Securities Act of
                                            1933, as amended.



 


		(g)	“Trading Day” means any weekday on which the
                                            Principal Trading Market is open for trading.



 






    


     


    

 


		(h)	“Transfer Agent” means Broadridge Corporate Issuer
                                            Solutions, Inc., the Company’s transfer agent and registrar for the Common Stock,
                                            and any successor appointed in such capacity.



 


		(i)	“VWAP” means, for any date, the price determined
                                            by the first of the following clauses that applies: (i) if the Common Stock is then
                                            listed or quoted on a national securities exchange or other trading market, the daily volume
                                            weighted average price of the Common Stock for such date (or the nearest preceding date)
                                            on the Principal Trading Market as reported by Bloomberg L.P. (based on a Trading Day from
                                            9:30 a.m. (New York City time) to 4:02 p.m. (New York City time)), (ii) if
                                            the Common Stock is then listed or quoted for trading and neither OTCQB nor OTCQX is the
                                            Principal Trading Market, the volume weighted average price of the Common Stock for such
                                            date (or the nearest preceding date) on OTCQB or OTCQX, as applicable, (iii) if the
                                            Common Stock is not then listed or quoted for trading on OTCQB or OTCQX and if prices for
                                            the Common Stock are then reported in the “Pink Sheets” published by OTC Markets
                                            Group, Inc. (or a similar organization or agency succeeding to its functions of reporting
                                            prices), the most recent bid price per share of the Common Stock so reported, or (iv) in
                                            all other cases, the fair market value of a share of Common Stock as determined by an independent
                                            appraiser selected in good faith by the Holder and reasonably acceptable to the Company,
                                            the fees and expenses of which shall be paid by the Company.



 


		2.	Issuance of Securities; Registration of Warrants. The Warrant,
                                            as initially issued by the Company, is offered and sold pursuant to the Registration Statement.
                                            As of the Original Issue Date, the Warrant Shares are issuable under the Registration Statement.
                                            Accordingly, the Warrant and, assuming issuance pursuant to the Registration Statement or
                                            an exchange meeting the requirements of Section 3(a)(9) of the Exchange Act as
                                            in effect on the Original Issue Date, the Warrant Shares, are not “restricted securities”
                                            under Rule 144 promulgated under the Securities Act. The Company shall register this
                                            Warrant, upon records to be maintained by the Company for that purpose (the “Warrant
                                            Register”), in the name of the record Holder (which shall include the initial Holder
                                            or, as the case may be, any registered assignee to which this Warrant is permissibly assigned
                                            hereunder) from time to time. The Company may deem and treat the registered Holder of this
                                            Warrant as the absolute owner hereof for the purpose of any exercise hereof or any distribution
                                            to the Holder, and for all other purposes, absent actual notice to the contrary.



 


		3.	Registration of Transfers. Subject to compliance with all
                                            applicable securities laws, the Company shall, or will cause its Transfer Agent to, register
                                            the transfer of all or any portion of this Warrant in the Warrant Register, upon surrender
                                            of this Warrant, and payment for all applicable transfer taxes (if any). Upon any such registration
                                            or transfer, a new warrant to purchase Common Stock in substantially the form of this Warrant
                                            (any such new warrant, a “New Warrant”) evidencing the portion of this
                                            Warrant so transferred shall be issued to the transferee, and a New Warrant evidencing the
                                            remaining portion of this Warrant not so transferred, if any, shall be issued to the transferring
                                            Holder. The acceptance of the New Warrant by the transferee thereof shall be deemed the acceptance
                                            by such transferee of all of the rights and obligations in respect of the New Warrant that
                                            the Holder has in respect of this Warrant. The Company shall, or will cause its Transfer
                                            Agent to, prepare, issue, and deliver at the Company’s own expense any New Warrant
                                            under this Section 3. Until due presentment for registration of transfer, the Company
                                            may treat the registered Holder hereof as the owner and holder of this Warrant for all purposes
                                            and the Company shall not be affected by any notice to the contrary.



 






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		4.	Exercise and Duration of Warrants.



 


		(a)	All or any part of this Warrant shall be exercisable by the registered
                                            Holder in any manner permitted by Section 10 of this Warrant at any time and from time
                                            to time on or after the Original Issue Date.



 


		(b)	The Holder may exercise this Warrant by delivering to the Company
                                            (i) an exercise notice, in the form attached as Schedule 1 hereto (the “Exercise
                                            Notice”), completed and duly signed, and (ii) payment of the Exercise Price
                                            for the number of Warrant Shares as to which this Warrant is being exercised (which may take
                                            the form of a “cashless exercise” if so indicated in the Exercise Notice pursuant
                                            to Section 10 below), and the date on which the last of such items is delivered to the
                                            Company (as determined in accordance with the notice provisions hereof) is an “Exercise
                                            Date.” The Holder shall not be required to deliver the original Warrant in order
                                            to effect an exercise hereunder. Execution and delivery of the Exercise Notice shall have
                                            the same effect as cancellation of the original Warrant and issuance of a New Warrant evidencing
                                            the right to purchase the remaining number of Warrant Shares.



 


		5.	Delivery of Warrant Shares.



 


		(a)	Upon exercise of this Warrant, the Company shall promptly (but in
                                            no event more than three (3) Trading Days after the Exercise Date), upon the request
                                            of the Holder, credit such aggregate number of shares of Common Stock to which the Holder
                                            is entitled pursuant to such exercise to the Holder’s or its designee’s balance
                                            account with The Depository Trust Company (“DTC”) through its Deposit
                                            Withdrawal Agent Commission system, or if the Transfer Agent is not participating in the
                                            Fast Automated Securities Transfer Program (the “FAST Program”) or if
                                            the certificates or book entry position are required to bear a legend regarding restriction
                                            on transferability, issue and dispatch by overnight courier to the address as specified in
                                            the Exercise Notice, a certificate or book entry position, registered in the Company’s
                                            share register in the name of the Holder or its designee, for the number of shares of Common
                                            Stock to which the Holder is entitled pursuant to such exercise. The Holder, or any natural
                                            person or legal entity (each, a “Person”) permissibly so designated by
                                            the Holder to receive Warrant Shares, shall be deemed to have become the holder of record
                                            of such Warrant Shares as of the Exercise Date, irrespective of the date such Warrant Shares
                                            are credited to the Holder’s DTC account or the date of delivery of the certificates
                                            or book entry position evidencing such Warrant Shares, as the case may be.



 


		(b)	If by the close of the third Trading Day after the Exercise Date,
                                            the Company fails to credit the Holder’s balance account with DTC for such number of
                                            Warrant Shares to which the Holder is entitled, and if after such third Trading Day and prior
                                            to the receipt of such Warrant Shares, the Holder purchases (in an open market transaction,
                                            provided such purchases shall be made in a commercially reasonable manner at prevailing market
                                            prices) shares of Common Stock to deliver in satisfaction of a sale by the Holder of the
                                            Warrant Shares which the Holder anticipated receiving upon such exercise (a “Buy-In”),
                                            then the Company shall, within two Trading Days after the Holder’s request, in the
                                            Holder’s sole discretion, either (i) pay in cash to the Holder an amount equal
                                            to the Holder’s total purchase price (including commercially reasonable brokerage commissions,
                                            if any) for the shares of Common Stock so purchased, at which point the Company’s obligation
                                            to deliver such Warrant Shares shall terminate, or (ii) (A) pay in cash to the
                                            Holder the amount, if any, by which (1) the Holder’s total purchase price (including
                                            commercially reasonable brokerage commissions, if any) for the shares of Common Stock purchased
                                            in the Buy-In exceeds (2) the product of (x) the number of Warrant Shares that
                                            the Company was required to deliver to the Holder in connection with the exercise at issue,
                                            times (y) the price at which the sell order giving rise to such purchase obligation
                                            was executed (assuming such sale was executed on commercially reasonable terms at prevailing
                                            market prices and, if the sale was executed in multiple transactions, the volume weighted
                                            average price), and (B) at the option of the Holder, either (1) reinstate the portion
                                            of the Warrant and equivalent number of Warrant Shares for which such exercise was not honored
                                            (in which case such exercise shall be deemed rescinded) or (2) deliver to the Holder
                                            the number of shares of Common Stock that would have been issued had the Company timely complied
                                            with its exercise and delivery obligations hereunder. The provisions of this Section 5(b) shall
                                            be the only remedy available to the Holder in the event the Company fails to deliver to the
                                            Holder the required number of Warrant Shares in the manner required pursuant to Section 5(a) and
                                            a Buy-In occurs. Irrespective of whether there is a Buy-In, no remedy shall be available,
                                            notwithstanding the requirements of Section 5(a), unless and until the Company fails
                                            to deliver to the Holder the required number of Warrant Shares by the close of the third
                                            Trading Day after the Exercise Date.



 






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		(c)	To the extent permitted by law and subject to Section 5(b),
                                            the Company’s obligations to issue and deliver Warrant Shares in accordance with and
                                            subject to the terms hereof (including the limitations set forth in Section 11 below)
                                            are absolute and unconditional, irrespective of any action or inaction by the Holder to enforce
                                            the same, any waiver or consent with respect to any provision hereof, the recovery of any
                                            judgment against any Person or any action to enforce the same, or any setoff, counterclaim,
                                            recoupment, limitation or termination, or any breach or alleged breach by the Holder or any
                                            other Person of any obligation to the Company or any violation or alleged violation of law
                                            by the Holder or any other Person, and irrespective of any other circumstance that might
                                            otherwise limit such obligation of the Company to the Holder in connection with the issuance
                                            of Warrant Shares. Subject to Section 5(b), nothing herein shall limit the Holder’s
                                            right to pursue any other remedies available to it hereunder, at law or in equity including,
                                            without limitation, a decree of specific performance and/or injunctive relief with respect
                                            to the Company’s failure to timely deliver certificates or a book entry position representing
                                            shares of Common Stock upon exercise of the Warrant as required pursuant to the terms hereof.



 


		6.	Charges, Taxes and Expenses. Issuance and delivery of a book
                                            entry position for shares of Common Stock upon exercise of this Warrant shall be made without
                                            charge to the Holder for any issue or transfer tax, transfer agent fee or other incidental
                                            tax or expense (excluding any applicable stamp duties) in respect of the issuance of such
                                            or book entry shares, all of which taxes and expenses shall be paid by the Company; provided,
                                            however, that the Company shall not be required to pay any tax that may be payable in respect
                                            of any transfer involved in the registration of any certificates for Warrant Shares or the
                                            Warrants in a name other than that of the Holder or an Affiliate thereof. The Holder shall
                                            be responsible for all other tax liability that may arise as a result of holding or transferring
                                            this Warrant or receiving Warrant Shares upon exercise hereof.



 


		7.	Replacement of Warrant. If this Warrant is mutilated, lost,
                                            stolen, or destroyed, the Company shall issue or cause to be issued in exchange and substitution
                                            for and upon cancellation hereof, or in lieu of and substitution for this Warrant, a New
                                            Warrant, but only upon receipt of evidence reasonably satisfactory to the Company of such
                                            loss, theft, or destruction (in such case) and, in each case, a customary and reasonable
                                            indemnity and surety bond if requested by the Company. Applicants for a New Warrant under
                                            such circumstances shall also comply with such other reasonable regulations and procedures
                                            and pay such other reasonable third-party costs as the Company may prescribe. If a New Warrant
                                            is requested as a result of a mutilation of this Warrant, then the Holder shall deliver such
                                            mutilated Warrant to the Company as a condition precedent to the Company’s obligation
                                            to issue the New Warrant.



 






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		8.	Reservation of Warrant Shares. The Company covenants that
                                            it will at all times while this Warrant is outstanding reserve and keep available out of
                                            the aggregate of its authorized but unissued and otherwise unreserved Common Stock, solely
                                            for the purpose of enabling it to issue Warrant Shares upon exercise of this Warrant as herein
                                            provided, the number of Warrant Shares that are then issuable and deliverable upon the exercise
                                            of this Warrant, free from preemptive rights or any other contingent purchase rights of persons
                                            other than the Holder (taking into account the adjustments and restrictions of Section 9).
                                            The Company covenants that all Warrant Shares so issuable and deliverable shall, upon issuance
                                            and the payment of the applicable Exercise Price in accordance with the terms hereof, be
                                            duly and validly authorized, issued and fully paid, and nonassessable. The Company will take
                                            all such action as may be reasonably necessary to assure that such shares of Common Stock
                                            may be issued as provided herein without violation of any applicable law or regulation or
                                            of any requirements of any securities exchange or automated quotation system upon which the
                                            Common Stock may be listed.



 


		9.	Certain Adjustments. The number of Warrant Shares issuable
                                            upon exercise of this Warrant is subject to adjustment from time to time as set forth in
                                            this Section 9.



 


		(a)	Stock Dividends and Splits. If the Company, at any time while
                                            this Warrant is outstanding, (i) pays a stock dividend on its Common Stock or otherwise
                                            makes a distribution on any class of capital stock issued and outstanding on the Original
                                            Issue Date and in accordance with the terms of such stock on the Original Issue Date or as
                                            amended, that is payable in shares of Common Stock, (ii) subdivides its outstanding
                                            shares of Common Stock into a larger number of shares of Common Stock, (iii) combines
                                            its outstanding shares of Common Stock into a smaller number of shares of Common Stock or
                                            (iv) issues by reclassification of shares of capital stock any additional shares of
                                            Common Stock of the Company, then in each such case the number of Warrant Shares then underlying
                                            this Warrant shall be divided by a fraction, the numerator of which shall be the number of
                                            shares of Common Stock outstanding immediately before such event and the denominator of which
                                            shall be the number of shares of Common Stock outstanding immediately after such event. Any
                                            adjustment made pursuant to clause (i) of this paragraph shall become effective immediately
                                            after the record date for the determination of stockholders entitled to receive such dividend
                                            or distribution, provided, however, that if such record date shall have been fixed and such
                                            dividend is not fully paid on the date fixed therefor, the number of Warrant Shares shall
                                            be recomputed accordingly as of the close of business on such record date and thereafter
                                            the Warrant Shares shall be adjusted pursuant to this paragraph as of the time of actual
                                            payment of such dividends. Any adjustment pursuant to clause (ii) or (iii) of this
                                            paragraph shall become effective immediately after the effective date of such subdivision
                                            or combination.



 


		(b)	Pro Rata Distributions. If the Company, at any time while
                                            this Warrant is outstanding, distributes to all holders of Common Stock for no consideration
                                            (i) evidences of its indebtedness, (ii) any security (other than a distribution
                                            of Common Stock covered by the preceding paragraph), (iii) rights or warrants to subscribe
                                            for or purchase any security, or (iv) cash or any other asset (in each case, “Distributed
                                            Property”), then, upon any exercise of this Warrant that occurs after the record
                                            date fixed for determination of stockholders entitled to receive such distribution, the Holder
                                            shall be entitled to receive, in addition to the Warrant Shares otherwise issuable upon such
                                            exercise (if applicable), the Distributed Property that such Holder would have been entitled
                                            to receive in respect of such number of Warrant Shares had the Holder been the record holder
                                            of such Warrant Shares immediately prior to such record date without regard to any limitation
                                            on exercise contained therein.



 






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		(c)	Fundamental Transactions. If, at any time while this Warrant
                                            is outstanding (i) the Company effects any merger or consolidation of the Company with
                                            or into another Person, in which the Company is not the surviving entity or the stockholders
                                            of the Company immediately prior to such merger or consolidation do not own, directly or
                                            indirectly, at least 50% of the voting power of the surviving entity immediately after such
                                            merger or consolidation, (ii) the Company effects any sale to another Person of all
                                            or substantially all of its assets in one transaction or a series of related transactions,
                                            (iii) pursuant to any tender offer or exchange offer (whether by the Company or another
                                            Person), holders of capital stock who tender shares representing more than 50% of the voting
                                            power of the capital stock of the Company and the Company or such other Person, as applicable,
                                            accepts such tender for payment, (iv) the Company consummates a stock purchase agreement
                                            or other business combination (including, without limitation, a reorganization, recapitalization,
                                            spin-off or scheme of arrangement) with another Person whereby such other Person acquires
                                            more than the 50% of the voting power of the capital stock of the Company (except for any
                                            such transaction in which the stockholders of the Company immediately prior to such transaction
                                            maintain, in substantially the same proportions, the voting power of such Person immediately
                                            after the transaction) or (v) the Company effects any reclassification of the Common
                                            Stock or any compulsory share exchange pursuant to which the Common Stock is effectively
                                            converted into or exchanged for other securities, cash or property (other than as a result
                                            of a subdivision or combination of shares of Common Stock covered by Section 9(a) above)
                                            (in any such case, a “Fundamental Transaction”), then following such Fundamental
                                            Transaction the Holder shall have the right to receive, upon exercise of this Warrant, the
                                            same amount and kind of securities, cash or property as it would have been entitled to receive
                                            upon the occurrence of such Fundamental Transaction if it had been, immediately prior to
                                            such Fundamental Transaction, the holder of the number of Warrant Shares then issuable upon
                                            exercise in full of this Warrant without regard to any limitations on exercise contained
                                            herein (the “Alternate Consideration”). The Company shall not effect any
                                            Fundamental Transaction in which the Company is not the surviving entity or the Alternate
                                            Consideration includes securities of another Person unless (x) the Alternate Consideration
                                            is solely cash and the Company provides for the simultaneous “cashless exercise”
                                            of this Warrant pursuant to Section 10 below or (y) prior to, simultaneously with
                                            or promptly following the consummation thereof, any successor to the Company, surviving entity
                                            or other Person (including any purchaser of assets of the Company) shall assume the obligation
                                            to deliver to the Holder, such Alternate Consideration as, in accordance with the foregoing
                                            provisions, the Holder may be entitled to receive, and the other obligations under this Warrant.
                                            The provisions of this paragraph (c) shall similarly apply to subsequent transactions
                                            analogous of a Fundamental Transaction type.



 


		(d)	Calculations. All calculations under this Section 9
                                            shall be made to the nearest share.



 


		(e)	Notice of Adjustments. Upon the occurrence of each adjustment
                                            pursuant to this Section 9, the Company at its expense will, at the written request
                                            of the Holder, promptly compute such adjustment, in good faith, in accordance with the terms
                                            of this Warrant and prepare a certificate setting forth such adjustment, including a statement
                                            of the adjusted number or type of Warrant Shares or other securities issuable upon exercise
                                            of this Warrant (as applicable), describing the transactions giving rise to such adjustments
                                            and showing in detail the facts upon which such adjustment is based. Upon written request,
                                            the Company will promptly deliver a copy of each such certificate to the Holder and to the
                                            Transfer Agent.



 






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		(f)	Notice of Corporate Events. If, while this Warrant is outstanding,
                                            the Company (i) declares a dividend or any other distribution of cash, securities or
                                            other property in respect of its Common Stock, including, without limitation, any granting
                                            of rights or warrants to subscribe for or purchase any capital stock of the Company or any
                                            subsidiary, (ii) enters into any definitive agreement contemplating or soliciting stockholder
                                            approval for any Fundamental Transaction or (iii) authorizes the voluntary dissolution,
                                            liquidation or winding up of the affairs of the Company, then, except if such notice and
                                            the contents thereof shall be deemed to constitute material non-public information, the Company
                                            shall deliver to the Holder a notice of such transaction at least ten (10) days prior
                                            to the applicable record or effective date on which a Person would need to hold Common Stock
                                            in order to participate in or vote with respect to such transaction; provided, however,
                                            that the failure to deliver such notice or any defect therein shall not affect the validity
                                            of the corporate action required to be described in such notice. In addition, if while this
                                            Warrant is outstanding, the Company enters into any definitive agreement contemplating or
                                            solicits stockholder approval for any Fundamental Transaction contemplated by Section 9(c),
                                            other than a Fundamental Transaction under clause (iii) of Section 9(c),
                                            the Company shall deliver to the Holder a notice of such Fundamental Transaction at least
                                            ten (10) days prior to the date such Fundamental Transaction is consummated. Holder
                                            agrees to maintain any information disclosed pursuant to this Section 9(f) in confidence
                                            until such information is publicly available and shall comply with applicable law with respect
                                            to trading in the Company’s securities following receipt any such information.



 


		10.	Payment of Exercise Price. Notwithstanding anything contained
                                            herein to the contrary, the Holder may, in its sole discretion, satisfy its obligation to
                                            pay the Exercise Price through a “cashless exercise,” in which event the Company
                                            shall issue to the Holder the number of Warrant Shares determined as follows:



 


X = Y [(A-B)/A]


 


where:


 


“X” equals the number of Warrant Shares
to be issued to the Holder;


 


“Y” equals the total number of Warrant
Shares with respect to which this Warrant is then being exercised;


 


“A” equals the last VWAP immediately
preceding the time of delivery of the Exercise Notice giving rise to the applicable “cashless exercise,” as set forth in
the applicable Exercise Notice (to clarify, the “last VWAP” will be the last VWAP as calculated over an entire Trading Day
such that, in the event that this Warrant is exercised at a time that the Trading Market is open, the prior Trading Day’s VWAP
shall be used in this calculation); and


 


“B” equals the Exercise Price then
in effect for the applicable Warrant Shares at the time of such exercise.


 






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For purposes of Rule 144 promulgated under
the Securities Act, it is intended, understood, and acknowledged that the Warrant Shares issued in a “cashless exercise”
transaction shall be deemed to have been acquired by the Holder, and the holding period for the Warrant Shares shall be deemed to have
commenced, on the date this Warrant was originally issued (provided that the Commission continues to take the position that such treatment
is proper at the time of such exercise).


 


Except as set forth in Section 12 (payment
of cash in lieu of fractional shares), in no event will the exercise of this Warrant be settled in cash.


 


		11.	Limitations on Exercise.



 


		(a)	Notwithstanding anything to the contrary contained in any Section herein,
                                            the Company shall not effect any exercise of this Warrant, and the Holder shall not be entitled
                                            to exercise this Warrant for a number of Warrant Shares in excess of that number of Warrant
                                            Shares which, upon giving effect to such exercise, would cause (i) the aggregate number
                                            of shares of Common Stock beneficially owned by the Holder and its Affiliates and any other
                                            Persons whose beneficial ownership of Common Stock would be aggregated with the Holder’s
                                            for purposes of Section 13(d) of the Exchange Act, to exceed 9.99% of the total
                                            number of issued and outstanding shares of Common Stock of the Company following such exercise,
                                            or (ii) the combined voting power of the securities of the Company beneficially owned
                                            by the Holder and its Affiliates and any other Persons whose beneficial ownership of Common
                                            Stock would be aggregated with the Holder’s for purposes of Section 13(d) of
                                            the Exchange Act to exceed 9.99% of the combined voting power of all of the securities of
                                            the Company then outstanding following such exercise. For purposes of this Warrant, in determining
                                            the number of outstanding shares of Common Stock, the Holder may rely on the number of outstanding
                                            shares of Common Stock as reflected in (x) the Company’s most recent Quarterly
                                            Report on Form 10-Q or Annual Report on Form 10-K, as the case may be, filed with
                                            the Commission prior to the date hereof, (y) a more recent public announcement by the
                                            Company or (z) any other notice by the Company or its transfer agent setting forth the
                                            number of shares of Common Stock outstanding. Upon the written request of the Holder, the
                                            Company shall within three (3) Trading Days confirm in writing or by electronic mail
                                            to the Holder the number of shares of Common Stock then outstanding. In any case, the number
                                            of outstanding shares of Common Stock shall be determined after giving effect to the conversion
                                            or exercise of securities of the Company, including this Warrant, by the Holder since the
                                            date as of which such number of outstanding shares of Common Stock was reported. By written
                                            notice to the Company, the Holder may from time to time increase or decrease the Maximum
                                            Percentage to any other percentage specified not in excess of 19.99% in such notice; provided
                                            that any such increase will not be effective until the sixty-first (61st) day
                                            after such notice is delivered to the Company. For purposes of this Section 11(a), the
                                            aggregate number of shares of Common Stock or voting securities beneficially owned by the
                                            Holder and its Affiliates and any other Persons whose beneficial ownership of Common Stock
                                            would be aggregated with the Holder’s for purposes of Section 13(d) of the
                                            Exchange Act shall include the shares of Common Stock issuable upon the exercise of this
                                            Warrant with respect to which such determination is being made, but shall exclude the number
                                            of shares of Common Stock which would be issuable upon (x) exercise of the remaining
                                            unexercised and non-cancelled portion of this Warrant by the Holder and (y) exercise
                                            or conversion of the unexercised, non-converted or non-cancelled portion of any other securities
                                            of the Company that do not have voting power (including, without limitation, any securities
                                            of the Company which would entitle the holder thereof to acquire at any time Common Stock,
                                            including, without limitation, any debt, preferred stock, right, option, warrant or other
                                            instrument that is at any time convertible into or exercisable or exchangeable for, or otherwise
                                            entitles the holder thereof to receive, Common Stock), is subject to a limitation on conversion
                                            or exercise analogous to the limitation contained herein and is beneficially owned by the
                                            Holder or any of its Affiliates and other Persons whose beneficial ownership of Common Stock
                                            would be aggregated with the Holder’s for purposes of Section 13(d) of the
                                            Exchange Act.



 






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		(b)	This Section 11 shall not restrict the number of shares of
                                            Common Stock that a Holder may receive or beneficially own in order to determine the amount
                                            of securities or other consideration that such Holder may receive in the event of a Fundamental
                                            Transaction as contemplated in Section 9 of this Warrant.



 


		12.	No Fractional Shares. No fractional Warrant Shares will be
                                            issued in connection with any exercise of this Warrant. In lieu of any fractional shares
                                            that would otherwise be issuable, the number of Warrant Shares to be issued shall be rounded
                                            down to the next whole number and the Company shall pay the Holder in cash the fair market
                                            value (based on the last VWAP immediately preceding the time of delivery of the applicable
                                            Exercise Notice) for any such fractional shares.



 


		13.	Notices. Any and all notices or other communications or deliveries
                                            hereunder (including, without limitation, any Exercise Notice) shall be in writing and shall
                                            be deemed given and effective on the earliest of (i) the date of transmission, if such
                                            notice or communication is delivered via confirmed e-mail at the e-mail address specified
                                            below prior to 4:00 P.M., New York City time, on a Trading Day, (ii) the next Trading
                                            Day after the date of transmission, if such notice or communication is delivered via confirmed
                                            e-mail at the e-mail address specified below on a day that is not a Trading Day or later
                                            than 4:00 P.M., New York City time, on any Trading Day, (iii) the second Trading Day
                                            following the date of mailing, if sent by nationally recognized overnight courier service
                                            specifying next business day delivery, or (iv) upon actual receipt by the Person to
                                            whom such notice is required to be given, if by hand delivery. The e-mail address for purposes
                                            of providing notice hereunder is: legal.department@immunogen.com.



 


		14.	Warrant Agent. The Company shall initially serve as warrant
                                            agent under this Warrant. Upon ten (10) days’ notice to the Holder, the Company
                                            may appoint a new warrant agent. Any corporation into which the Company or any new warrant
                                            agent may be merged or any corporation resulting from any consolidation to which the Company
                                            or any new warrant agent shall be a party or any corporation to which the Company or any
                                            new warrant agent transfers substantially all of its corporate trust or shareholders services
                                            business shall be a successor warrant agent under this Warrant without any further act. Any
                                            such successor warrant agent shall promptly cause notice of its succession as warrant agent
                                            to be mailed (by first class mail, postage prepaid) to the Holder at the Holder’s last
                                            address as shown on the Warrant Register.



 


		15.	Miscellaneous.



 


		(a)	No Rights as a Stockholder. The Holder, solely in such Person’s
                                            capacity as a holder of this Warrant, shall not be entitled to vote or receive dividends
                                            or be deemed the holder of share capital of the Company for any purpose, nor shall anything
                                            contained in this Warrant be construed to confer upon the Holder, solely in such Person’s
                                            capacity as the Holder of this Warrant, any of the rights of a stockholder of the Company
                                            or any right to vote, give or withhold consent to any corporate action (whether any reorganization,
                                            issue of stock, reclassification of stock, consolidation, merger, amalgamation, conveyance
                                            or otherwise), receive notice of meetings, receive dividends or subscription rights, or otherwise,
                                            prior to the issuance to the Holder of the Warrant Shares which such Person is then entitled
                                            to receive upon the due exercise of this Warrant. In addition, nothing contained in this
                                            Warrant shall be construed as imposing any liabilities on the Holder to purchase any securities
                                            (upon exercise of this Warrant or otherwise) or as a stockholder of the Company, whether
                                            such liabilities are asserted by the Company or by creditors of the Company.



 






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		(b)	Authorized Shares. Except and to the extent as waived or
                                            consented to by the Holder, the Company shall not by any action, including, without limitation
                                            amending its articles of organization or effect any reorganization, transfer of assets, consolidation,
                                            merger, dissolution, issue, or sale of securities or any other voluntary action to avoid
                                            or seek to avoid the observance or performance of any of the terms of this Warrant, but will
                                            at all times in good faith assist in the carrying out of all such terms and in the taking
                                            of all such actions as may be necessary or appropriate to protect the rights of Holder as
                                            set forth in this Warrant against impairment. Without limiting the generality of the foregoing,
                                            the Company will (i) not increase the par value of any Warrant Shares above the amount
                                            payable therefor upon such exercise immediately prior to such increase in par value, (ii) take
                                            all such action as may be necessary or appropriate in order that the Company may validly
                                            and legally issue fully paid and nonassessable Warrant Shares upon the exercise of this Warrant,
                                            and (iii) use commercially reasonable efforts to obtain all such authorizations, exemptions
                                            or consents from any public regulatory body having jurisdiction thereof as may be necessary
                                            to enable the Company to perform its obligations under this Warrant.



 


		(c)	Successors and Assigns. Subject to compliance with applicable
                                            securities laws, this Warrant may be assigned by the Holder. This Warrant may not be assigned
                                            by the Company without the written consent of the Holder except to a successor in the event
                                            of a Fundamental Transaction. This Warrant shall be binding on and inure to the benefit of
                                            the Company and the Holder and their respective successors and assigns. Subject to the preceding
                                            sentence, nothing in this Warrant shall be construed to give to any Person other than the
                                            Company and the Holder any legal or equitable right, remedy, or cause of action under this
                                            Warrant. This Warrant may be amended only in writing signed by the Company and the Holder,
                                            or their successors and assigns.



 


		(d)	Amendment and Waiver. Except as otherwise provided herein,
                                            the provisions of the Warrants may be amended and the Company may take any action herein
                                            prohibited, or omit to perform any act herein required to be performed by it, only if the
                                            Company has obtained the written consent of the Holder.



 


		(e)	Acceptance. Receipt of this Warrant by the Holder shall constitute
                                            acceptance of and agreement to all of the terms and conditions contained herein.



 


		(f)	Governing Law; Jurisdiction. ALL QUESTIONS CONCERNING THE
                                            CONSTRUCTION, VALIDITY, ENFORCEMENT, AND INTERPRETATION OF THIS WARRANT SHALL BE GOVERNED
                                            BY, AND CONSTRUED AND ENFORCED IN ACCORDANCE WITH, THE LAWS OF THE COMMONWEALTH OF MASSACHUSETTS
                                            WITHOUT REGARD TO THE PRINCIPLES OF CONFLICTS OF LAW THEREOF. EACH OF THE COMPANY AND THE
                                            HOLDER HEREBY IRREVOCABLY SUBMITS TO THE EXCLUSIVE JURISDICTION OF THE STATE AND FEDERAL
                                            COURTS SITTING IN THE COMMONWEALTH OF MASSACHUSETTS, FOR THE ADJUDICATION OF ANY DISPUTE
                                            HEREUNDER OR IN CONNECTION HEREWITH OR WITH ANY TRANSACTION CONTEMPLATED HEREBY OR DISCUSSED
                                            HEREIN (INCLUDING WITH RESPECT TO THE ENFORCEMENT OF ANY OF THE TRANSACTION DOCUMENTS), AND
                                            HEREBY IRREVOCABLY WAIVES, AND AGREES NOT TO ASSERT IN ANY SUIT, ACTION OR PROCEEDING, ANY
                                            CLAIM THAT IT IS NOT PERSONALLY SUBJECT TO THE JURISDICTION OF ANY SUCH COURT. EACH OF THE
                                            COMPANY AND THE HOLDER HEREBY IRREVOCABLY WAIVES PERSONAL SERVICE OF PROCESS AND CONSENTS
                                            TO PROCESS BEING SERVED IN ANY SUCH SUIT, ACTION OR PROCEEDING BY MAILING A COPY THEREOF
                                            VIA REGISTERED OR CERTIFIED MAIL OR OVERNIGHT DELIVERY (WITH EVIDENCE OF DELIVERY) TO SUCH
                                            PERSON AT THE ADDRESS IN EFFECT FOR NOTICES TO IT AND AGREES THAT SUCH SERVICE SHALL CONSTITUTE
                                            GOOD AND SUFFICIENT SERVICE OF PROCESS AND NOTICE THEREOF. NOTHING CONTAINED HEREIN SHALL
                                            BE DEEMED TO LIMIT IN ANY WAY ANY RIGHT TO SERVE PROCESS IN ANY MANNER PERMITTED BY LAW.
                                            EACH OF THE COMPANY AND THE HOLDER HEREBY WAIVES ALL RIGHTS TO A TRIAL BY JURY.



 






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		(g)	Headings. The headings herein are for convenience only, do
                                            not constitute a part of this Warrant, and shall not be deemed to limit or affect any of
                                            the provisions hereof.



 


		(h)	Severability. In case any one or more of the provisions of
                                            this Warrant shall be invalid or unenforceable in any respect, the validity and enforceability
                                            of the remaining terms and provisions of this Warrant shall not in any way be affected or
                                            impaired thereby, and the Company and the Holder will attempt in good faith to agree upon
                                            a valid and enforceable provision which shall be a commercially reasonable substitute therefor,
                                            and upon so agreeing, shall incorporate such substitute provision in this Warrant.



 


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    11


     


    

 


IN WITNESS WHEREOF, the Company has caused this
Warrant to be duly executed by its authorized officer as of the date first indicated above.


 


	 	IMMUNOGEN, INC.
	 	 
	 	 
	 	By: 	       
	 	 	Name:
	 	 	Title:




 






    


     


    

 


SCHEDULE
1


 


FORM OF
EXERCISE NOTICE


 


[To be executed by the Holder to purchase shares
of Common Stock under the Warrant]


 


Ladies and Gentlemen:


 


		(1)	The undersigned is the Holder of Warrant No. ______ (the “Warrant”)
                                            issued by ImmunoGen, Inc., a Massachusetts corporation (the “Company”).
                                            Capitalized terms used herein and not otherwise defined herein have the respective meanings
                                            set forth in the Warrant.



 


		(2)	The undersigned hereby exercises its right to purchase Warrant Shares
                                            pursuant to the Warrant.



 


		(3)	The Holder intends that payment of the Exercise Price shall be made
                                            as (check one):



 


 ̈           Cash
Exercise


 


 ̈           “Cashless
Exercise” under Section 10 of the Warrant


 


(4)    If the Holder has
elected a Cash Exercise, the Holder shall pay the sum of $______ in immediately available funds to the Company in accordance with the
terms of the Warrant.


 


		(5)	Pursuant to this Exercise Notice, the Company shall deliver to the
                                            Holder Warrant Shares determined in accordance with the terms of the Warrant.



 


		(6)	By its delivery of this Exercise Notice, the undersigned represents
                                            and warrants to the Company that in giving effect to the exercise evidenced hereby the Holder
                                            will not beneficially own in excess of the number of shares of Common Stock (as determined
                                            in accordance with Section 13(d) of the Securities Exchange Act of 1934, as amended)
                                            permitted to be owned under Section 11(a) of the Warrant to which this notice relates.



 


	Dated:	 	 
	 	 	 
	Name of Holder:	 	 
	 	 	 
	By:	 	 
	 	 	 
	Name:	 	 
	 	 	 
	Title:	 	 




 


(Signature must conform in all respects to name
of Holder as specified on the face of the Warrant)