CHANGE IN CONTROL SEVERANCE AGREEMENT

CHANGE IN CONTROL SEVERANCE AGREEMENT

This Agreement is entered into as of the 31st day of March, 2017 (the “Effective Date”) by and between ImmunoGen, Inc., a Massachusetts corporation (the “Company”), and Richard J. Gregory (the “Executive”).

WHEREAS, the Company recognizes that the Executive’s service to the Company is very important to the future success of the Company;

WHEREAS, the Executive desires to enter into this Agreement to provide the Executive with certain financial protection in the event that his employment terminates under certain conditions following a change in control of the Company; and

WHEREAS the Board of Directors of the Company (the “Board”) has determined that it is in the best interests of the Company to enter into this Agreement.

NOW, THEREFORE, for good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the Company and the Executive hereby agree as follows:

(b)Change in Control.  For purposes of this Agreement, a “Change in Control” shall mean the occurrence of any of the following events:

(i)Ownership.  Any “Person” (as such term is used in Sections 13(d) and 14(d) of the Securities Exchange Act of 1934, as amended) becomes the “Beneficial Owner” (as defined in Rule 13d-3 under said Act), directly or indirectly, of securities of the Company representing 50% or more of the total voting power represented by the Company’s then outstanding voting securities (excluding for this purpose any such voting securities held by the Company or its Affiliates (as defined in the Company’s 2016 Employee, Director and Consultant Equity Incentive Plan) or by any employee benefit plan of the Company) pursuant to a transaction or a series of related transactions which the Board does not approve; or

(ii)Merger/Sale of Assets.  (A) A merger or consolidation of the Company whether or not approved by the Board, other than a merger or consolidation which would result in the voting securities of the Company outstanding immediately prior thereto continuing to represent (either by remaining outstanding or by being converted into voting securities of the surviving entity or the parent of such corporation) at least 50% of the total voting power represented by the voting securities of the Company or such surviving entity or parent of such corporation, as the case may be, outstanding immediately after such merger or consolidation; or (B) the stockholders of the Company approve an agreement for the sale or disposition by the Company of all or substantially all of the Company’s assets; or

(iii)Change in Board Composition.  A change in the composition of the Board, as a result of which fewer than a majority of the directors are Incumbent Directors.  “Incumbent Directors” shall mean directors who either (A) are directors of the Company as of December 10, 2016, or (B) are elected, or nominated for election, to the Board with the affirmative votes of at least a majority of the Incumbent Directors at the time of such election or nomination (but shall not include an individual whose election or nomination is in connection with an actual or threatened proxy contest relating to the election of directors to the Company).

(c)Disability.  For purposes of this Agreement, “Disability” shall mean that the Executive (i) is unable to engage in any substantial gainful activity because of any medically determinable physical or mental impairment which can be expected to result in death or can be expected to last for a continuous period of at least twelve (12) months, or (ii) is receiving income replacement benefits for a period of at least three (3) months under a Company-sponsored disability plan because of any medically determinable physical or mental impairment which can be expected to result in death or can be expected to last for a continuous period of at least twelve (12) months.  Whether the Executive has a Disability will be determined by a majority of the Board based on evidence provided by one or more physicians selected by the Board and approved by the Executive, which approval shall not be unreasonably withheld.  In any case, if a disability is determined to trigger the payment of any “deferred compensation” as defined in Section 409A of the Internal Revenue Code of 1986, as amended (the “Code”), disability shall be determined in accordance with Section 409A of the Code.

(d)Good Reason.  For purposes of this Agreement, “Good Reason” shall mean the occurrence of one or more of the following without the Executive’s consent: (i) a change in the principal location at which the Executive performs his duties for the Company to a new location that is at least a  forty (40) mile longer commute for the Executive from the prior work location; (ii) a material change in the Executive's authority, functions, duties or responsibilities as an executive of the Company, which would cause his position with the Company to become of less responsibility, importance or scope than his highest position with the Company at any time from the date of this Agreement to immediately prior to the Change in Control, provided,  however, that such material change is not in connection with the termination of the Executive's employment by the Company for Cause or death or Disability and further provided that it shall not be considered a material change if the Company becomes a subsidiary of another entity and the Executive continues to hold a position in the subsidiary that is at least as high (in both title and scope of responsibilities) as the highest position he held with the Company at any time from

the date of this Agreement to immediately prior to the Change in Control; (iii) a material reduction in the Executive’s annual base salary; or (iv) a material reduction in the Executive’s target annual bonus as compared to the target annual bonus set for the previous fiscal year.

For purposes of any determination regarding the existence of Good Reason, any claim by the Executive that Good Reason exists shall be presumed to be correct unless the Company establishes by clear and convincing evidence that Good Reason does not exist.

(iii)  provided Executive elects continuation of medical insurance coverage for the Executive and/or the Executive’s family subject to and in accordance with the Consolidated Omnibus Budget Reconciliation Act (“COBRA”), the Company will subsidize the Executive’s COBRA premium at the same percentage as it subsidized health insurance premiums for the Executive immediately prior to the Executive’s Termination Date (or, if more favorable to the Executive,  

immediately prior to the consummation of the Change in Control) (the “COBRA Premium Subsidy”) for a period of up to eighteen (18) months from the Executive’s Termination Date;  provided that the Company shall have no obligation to provide the COBRA Premium Subsidy after the date the Executive becomes eligible for medical coverage with another employer or becomes entitled to Medicare, notice of which the Executive shall provide to the Company within five (5) business days of the eligibility event.  If the Company determines that the COBRA Premium Subsidy is taxable income to the Executive, the income will be reported on Form W-2 as imputed income; and

(iv)  the Company shall pay the cost of providing the Executive with outplacement services up to a maximum of $40,000, provided that (A) the Executive begins to use such services within six (6) months following the Executive’s Termination Date, and (B) such services are provided by an outplacement services provider approved by the Company (which approval shall not be unreasonably withheld, conditioned or delayed).  Such payment shall be made by the Company directly to the service provider promptly following the presentation to the Company of documentation of the enrollment by the Executive with the provider of outplacement services and the service provider’s invoice for such services.  In no event will the Executive be entitled to receive the cash value of the outplacement services in lieu of the outplacement services.

For purposes of this Agreement, “Annual Salary” shall mean the Executive’s annual base salary then in effect or, if higher, in effect at the time of the Change in Control, excluding reimbursements and amounts attributable to stock options and other non-cash compensation; and the “Severance Compensation” shall mean the compensation set forth in (i), (ii), (iii), and (iv) above.

Any further dispute or controversy arising under or in connection with this Agreement shall be settled exclusively by arbitration, paid for by the Company, in Boston, Massachusetts, in accordance with the rules of the American Arbitration Association then in effect; provided,  however, that the evidentiary standards set forth in this Agreement shall apply; and further provided that the parties agree that the binding arbitration protocol shall be structured such that a decision will issue not later than ninety (90) days following notice in the event of a dispute concerning Good Reason pursuant to Section 3(b).  Judgment may be entered on the arbitrator’s award in any court having jurisdiction.  Notwithstanding any provision of this Agreement to the contrary, the Executive shall be entitled to seek specific performance of the Executive’s right to

be paid until the Termination Date during the pendency of any dispute or controversy arising under of in connection with this Agreement.

[Signature Page follows]

IN WITNESS WHEREOF, the parties have executed and delivered this Change in Control Severance Agreement as of the day and year first above written.

COMPANY:

IMMUNOGEN, INC.

/s/ Mark J. Enyedy

Name: Mark J. Enyedy

Title: President and Chief Executive Officer

EXECUTIVE:

/s/ Richard J.Gregory

Name:  Richard J. Gregory

Exhibit A

GENERAL RELEASE

1.General Release.  In consideration of the payments and benefits to be made under that certain Change in Control Severance Agreement, dated March 31, 2017 (the “Agreement”), Richard J. Gregory (the “Executive”), with the intention of binding the Executive and the Executive's heirs, executors, administrators and assigns, does hereby release, remise, acquit and forever discharge ImmunoGen, Inc. (the “Company”) and each of its subsidiaries and affiliates (collectively, the “Company Affiliated Group”), their present and former officers, directors, executives, agents, insurers, attorneys, employees, and employee benefits plans (and the fiduciaries thereof), and the successors, predecessors, and assigns of each of the foregoing (collectively with the Company Affiliated Group, the “Company Released Parties”), of and from any and all claims, actions, causes of action, complaints, charges, demands, rights, damages, debts, sums of money, accounts, financial obligations, suits, expenses, attorneys' fees and liabilities of whatever kind or nature in law, equity or otherwise, whether accrued, absolute, contingent, unliquidated or otherwise and whether now known or unknown, suspected or unsuspected which the Executive, individually or as a member of a class, now has, owns or holds, or has at any time heretofore had, owned or held, against any Company Released Party in any capacity, including, without limitation, any and all claims (i) arising out of or in any way connected with the Executive's service to any member of the Company Affiliated Group (or the predecessors thereof) in any capacity, or the termination of such service in any such capacity, (ii) for severance or vacation benefits, unpaid wages, rights in or for equity based awards, salary or incentive payments, (iii) for breach of contract, wrongful discharge, impairment of economic opportunity, defamation, intentional infliction of emotional harm or other tort and (iv) for any violation of applicable state and local labor and employment laws (including, without limitation, all laws concerning unlawful and unfair labor and employment practices), any and all claims based on the Employee Retirement Income Security Act of 1974 (“ERISA”), any and all claims arising under the civil rights laws of any federal, state or local jurisdiction, including, without limitation, Title VII of the Civil Rights Act of 1964 (“Title VII”), the Age Discrimination in Employment Act (“ADEA”), the Americans with Disabilities Act (“ADA”), Sections 503 and 504 of the Rehabilitation Act the Family and Medical Leave Act, the Massachusetts Fair Employment Practices Act, the Massachusetts Payment of Wages Law, An Act Relative to Domestic Violence, and any and all claims under any whistleblower laws or whistleblower provisions of other laws.

2.No Admissions.  The Executive acknowledges and agrees that this General Release is not to be construed in any way as an admission of any liability whatsoever by any Company Released Party, any such liability being expressly denied.

3.Application to all Forms of Relief.  This General Release applies to any relief no matter how called, including, without limitation, wages, back pay, front pay, compensatory damages, liquidated damages, punitive damages for pain or suffering, costs and attorney's fees and expenses.

4.Specific Waiver.  The Executive specifically acknowledges that his acceptance of the terms of this General Release is, among other things, a specific waiver of his rights, claims and causes of action under Title VII, ADEA, ADA, the Massachusetts Fair Employment Practices Act and any state or local law or regulation in respect of discrimination of any kind; provided, however, that nothing herein shall be deemed, nor does anything herein purport, to be a waiver of any right or claim or cause of action which by law the Executive is not permitted to waive.

The Executive expressly agrees and understands that the release of claims contained herein is a General Release and that any references to specific claims arising out of or in connection with the Executive’s employment or termination are not intended to limit the release of claims.  The Executive expressly agrees and understands that this General Release means that the Executive is releasing, remising and discharging the Released Parties from and with respect to all claims, whether known or unknown, asserted or unasserted, and whether or not the claims arise out of or in connection with the Executive’s employment or termination, or otherwise, to the extent permitted by law.

5.No Complaints or Other Claims.  The Executive acknowledges and agrees that he has not, with respect to any transaction or state of facts existing prior to the date hereof, filed any complaints, charges or lawsuits against any Company Released Party with any governmental agency, court or tribunal.  This General Release does not: (i) prohibit or restrict Executive from communicating, providing relevant information to or otherwise cooperating with the U.S. Equal Employment Opportunity Commission or any other governmental authority with responsibility for the administration of fair employment practices laws regarding a possible violation of such laws or responding to any inquiry from such authority, including an inquiry about the  existence of this General Release or its underlying facts, or (ii) require Executive to notify the Company of such communications or inquiry.

6.Conditions of General Release.

(a)   Terms and Conditions.  From and after the date of termination of employment, the Executive shall abide by all the terms and conditions of this General Release and the terms and any conditions set forth in any employment or confidentiality agreements signed by the Executive, which is incorporated herein by reference.

(b)   Confidentiality.  The Executive shall not, without the prior written consent of the Company or as may otherwise be required by law or any legal process, or as is necessary in connection with any adversarial proceeding against any member of the Company Affiliated Group (in which case the Executive shall cooperate with the Company in obtaining a protective order at the Company's expense against disclosure by a court of competent jurisdiction), communicate, to anyone other than the Company and those designated by the Company or on behalf of the Company in the furtherance of its business, any trade secrets, confidential information, knowledge or data relating to any member of the Company Affiliated Group, obtained by the Executive during the Executive's employment by the Company that is not generally available public knowledge (other than acts by the Executive in violation of this General Release).  This confidentiality obligation is in addition to, and not in lieu of, any other

contractual, statutory and common law confidentiality obligation of the Executive to the Company.

(c)   Return of Company Material.  The Executive represents that he has returned to the Company all Company Material (as defined below).  For purposes of this Section 6(c), "Company Material" means any documents, files and other property and information of any kind belonging or relating to (i) any member of the Company Affiliated Group, (ii) the current and former suppliers, creditors, directors, officers, employees, agents and customers of any of them or (iii) the businesses, products, services and operations (including without limitation, business, financial and accounting practices) of any of them, in each case whether tangible or intangible (including, without limitation, credit cards, building and office access cards, keys, computer equipment, cellular telephones, pagers, electronic devices, hardware, manuals, files, documents, records, software, customer data, research, financial data and information, memoranda, surveys, correspondence, statistics and payroll and other employee data, and any copies, compilations, extracts, excerpts, summaries and other notes thereof or relating thereto), excluding only information (x) that is generally available public knowledge or (y) that relates to the Executive's compensation or Executive benefits.

(d)   Cooperation.  Following the date of termination of employment, the Executive shall reasonably cooperate with the Company upon reasonable request of the Board of Directors and be reasonably available to the Company with respect to matters arising out of the Executive's services to the Company Affiliated Group.

(e)   Nondisparagement.  The Executive acknowledges and agrees that, following execution of this General Release, he shall not make any statements that are professionally or personally disparaging about or adverse to the interests of any Company Released Party, including, but not limited to, any statements that disparage in any way whatsoever the Company’s products, services, businesses, finances, financial condition, capabilities or other characteristics.

(f)   Ownership of Inventions, Non-Disclosure, Non-Competition and Non-Solicitation.  The Executive expressly acknowledges and agrees that the Proprietary Information, Inventions, and Competition Agreement executed by him is incorporated herein by reference, and shall survive the execution of this General Release in full force and effect pursuant to its terms.

(g)   No Representation.  The Executive acknowledges that, other than as set forth in this General Release and the Agreement, (i) no promises have been made to him and (ii) in signing this General Release the Executive is not relying upon any statement or representation made by or on behalf of any Company Released Party and each or any of them concerning the merits of any claims or the nature, amount, extent or duration of any damages relating to any claims or the amount of any money, benefits, or compensation due the Executive or claimed by the Executive, or concerning the General Release or concerning any other thing or matter.

(h)   Injunctive Relief.  In the event of a breach or threatened breach by the Executive of this Section 6, the Executive agrees that the Company shall be entitled to injunctive

relief in a court of appropriate jurisdiction to remedy any such breach or threatened breach, the Executive acknowledging that damages would be inadequate or insufficient.

7.Voluntariness.  The Executive agrees that he is relying solely upon his own judgment; that the Executive is over eighteen years of age and is legally competent to sign this General Release; that the Executive is signing this General Release of his own free will; that the Executive has read and understood the General Release before signing it; and that the Executive is signing this General Release in exchange for consideration that he believes is satisfactory and adequate.

8.Legal Counsel.  The Executive acknowledges that he has been informed of the right to consult with legal counsel and has been encouraged to do so.

9.Complete Agreement/Severability.  Other than the agreements and/or obligations specifically referenced as surviving herein, this General Release constitutes the complete and final agreement between the parties and supersedes and replaces all prior or contemporaneous agreements, negotiations, or discussions relating to the subject matter of this General Release.  All provisions and portions of this General Release are severable.  If any provision or portion of this General Release or the application of any provision or portion of the General Release shall be determined to be invalid or unenforceable to any extent or for any reason, all other provisions and portions of this General Release shall remain in full force and shall continue to be enforceable to the fullest and greatest extent permitted by law.

10.Acceptance.  The Executive acknowledges that he has been given a period of twenty-one (21) days within which to consider this General Release, unless applicable law requires a longer period, in which case the Executive shall be advised of such longer period and such longer period shall apply.  The Executive may accept this General Release at any time within this period of time by signing the General Release and returning it to the Company.

11.Revocability.  This General Release shall not become effective or enforceable until seven (7) calendar days after the Executive signs it.  The Executive may revoke his acceptance of this General Release at any time within that seven (7) calendar day period by sending written notice to the Company.  Such notice must be received by the Company within the seven (7) calendar day period in order to be effective and, if so received, would void this General Release for all purposes.

12.Governing Law.  Except for issues or matters as to which federal law is applicable, this General Release shall be governed by and construed and enforced in accordance with the laws of the Commonwealth of Massachusetts without giving effect to the conflicts of law principles thereof.

[Signature page follows]

IN WITNESS WHEREOF, the Executive has executed this General Release as of the date last set forth below.

EXECUTIVE

_______________________________Date: __________________________

Name: Richard J. Gregory