EX-10.13




 Exhibit 10.13 

AMENDED AND RESATED 

EMPLOYMENT AGREEMENT 
 This
Amended and Restated Employment Agreement (“Agreement”) is made by and between Magenta Therapeutics, Inc., a Delaware corporation (the “Company”), and Stephen Mahoney (the “Executive”) and is effective as of
March 3, 2022 (the “Effective Date”). 
 WHEREAS, the Executive is currently serving as the Company’s Chief Financial
and Operating Officer and possesses certain experience and expertise that qualify the Executive to provide the direction and leadership required by the Company and its affiliates; 

WHEREAS, the Company and the Executive are party to an Employment Agreement dated as of November 9, 2020 (the “Original
Agreement”); and 
 WHEREAS, the Company and the Executive wish to amend and restate the Original Agreement in accordance with the
terms and conditions set forth in this Agreement. 
 NOW, THEREFORE, in consideration of the mutual covenants and agreements herein
contained and other good and valuable consideration, the receipt and sufficiency of which is hereby acknowledged, the parties agree as follows: 
  

	 	1.	 Employment. 



(a)    Term. The Company and the Executive desire to continue their employment relationship pursuant to this
Agreement as of the Effective Date and continuing in effect until terminated by either party in accordance with this Agreement (the “Term”). The Executive’s employment will continue to be “at will,” meaning that the
Executive’s employment may be terminated by the Company or the Executive any time and for any reason, subject to the terms of this Agreement. 

(b)    Position and Duties. During the Term, the Executive shall serve as the Chief Financial and Operating Officer
of the Company and shall have powers and duties that may from time to time be prescribed by the Company’s Chief Executive Officer (the “CEO”) or another authorized executive. The Executive shall devote Executive’s
full working time and efforts to the business and affairs of the Company. Notwithstanding the foregoing, the Executive may serve on up to two (2) for-profit boards of directors, with the prior written
approval of the CEO, or engage in not-for-profit, charitable or other community activities, as long as the foregoing does not, individually or in the aggregate,
materially interfere with the Executive’s performance of Executive’s duties to the Company as provided in this Agreement. The Executive reaffirms that Executive has no contractual commitments or other legal obligations that would prohibit
Executive’s from fully performing Executive’s duties for the Company. 
 (c)    Regular Place of
Employment. The Executive’s regular place of work will be at Magenta Therapeutics, Inc., which is currently located at 100 Technology Square, Cambridge, MA 02139, provided that the Executive may be required to travel from time to time,
consistent with business needs. 

  
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	 	2.	 Compensation and Related Matters. 



(a)    Base Salary. The Executive’s annual base salary shall be $448,000, which is subject to review and
redetermination by the Company’s Board or the Compensation Committee thereof. The base salary in effect at any given time is referred to herein as “Base Salary.” The Base Salary shall be payable in a manner that is consistent with the
Company’s usual payroll practices for senior executives. 
 (b)    Incentive Compensation. During the Term,
the Executive shall be eligible to receive cash incentive compensation as determined by and in the sole discretion of the Board or the Compensation Committee from time to time. The Executive’s target annual incentive compensation shall be 40%
of the Executive’s Base Salary, as may be redetermined from time to time (the “Target Incentive Compensation”), with any incentive compensation for the year in which employment commences to be prorated based on the Effective Date. To
earn incentive compensation, the Executive must be employed by the Company on the day such incentive compensation is paid. 

(c)    Expenses. The Executive shall be entitled to receive prompt reimbursement for all reasonable expenses
incurred by Executive during the Term in performing services hereunder, in accordance with the policies and procedures then in effect and established by the Company for its senior executive officers. 

(d)    Other Benefits. During the Term, the Executive shall be entitled to participate in or receive benefits under
the Company’s employee benefit plans in effect from time to time, including paid sick time under applicable law, subject to the terms of such plans and to the Company’s ability to amend, modify, replace or terminate such plans and
programs.  
 (e)    Vacations. During the Term, the Executive shall be entitled to take paid
vacation in accordance with the Company’s vacation policy, as may be in effect from time to time. The Executive shall also be entitled to all paid holidays given by the Company to its executives. 

(f)    Equity Awards. The equity awards held by the Executive shall be governed by the terms and conditions of the
Company’s applicable equity incentive plan(s) and the applicable award agreement(s) governing the terms of such equity awards held by the Executive (collectively, the “Equity Documents”); provided, however, and notwithstanding
anything to the contrary in the Equity Documents, Section 6(a)(ii) of this Agreement shall apply in the event of a termination by the Company without Cause or by the Executive for Good Reason in either event within the Change in Control Period
(as such terms are defined below). 
 3.     Termination. During the Term, the Executive’s employment
hereunder may be terminated without any breach of this Agreement under the following circumstances: 

(a)    Death. The Executive’s employment hereunder shall terminate upon his death. 

  
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 (b)    Disability. The Company may terminate the Executive’s
employment if Executive is disabled and unable to perform the essential functions of the Executive’s then existing position or positions under this Agreement with or without reasonable accommodation for a period of 180 days (which need not be
consecutive) in any 12-month period. If any question shall arise as to whether during any period the Executive is disabled so as to be unable to perform the essential functions of the Executive’s
then-existing position or positions with or without reasonable accommodation, the Executive may, and at the request of the Company shall, submit to the Company a certification in reasonable detail by a physician selected by the Company to whom the
Executive or the Executive’s guardian has no reasonable objection as to whether the Executive is so disabled or how long such disability is expected to continue, and such certification shall for the purposes of this Agreement be conclusive of
the issue. The Executive shall cooperate with any reasonable request of the physician in connection with such certification. If such question shall arise and the Executive shall fail to submit such certification, the Company’s determination of
such issue shall be binding on the Executive. Nothing in this Section 3(b) shall be construed to waive the Executive’s rights, if any, under existing law including, without limitation, the Family and Medical Leave Act of 1993, 29 U.S.C.
§2601 et seq. and the Americans with Disabilities Act, 42 U.S.C. §12101 et seq. 

(c)    Termination by Company for Cause. The Company may terminate the Executive’s employment hereunder for
Cause. For purposes of this Agreement, “Cause” shall mean: (i) the Executive’s dishonest statements or acts with respect to the Company or any affiliate of the Company, or any current or prospective customers, suppliers, vendors
or other third parties with which such entity does business; (ii) the Executive’s commission of (A) a felony or (B) any misdemeanor involving moral turpitude, deceit, dishonesty or fraud; (iii) the Executive’s failure
to perform Executive’s assigned duties and responsibilities to the reasonable satisfaction of the Company which failure continues, in the reasonable judgment of the Company, thirty (30) or more days after written notice has been given to
the Executive by the Company reasonably describing such failure; (iv) the Executive’s gross negligence, willful misconduct or insubordination with respect to the Company or any affiliate of the Company; or (v) the Executive’s
material violation of any provision of any agreement(s) between the Executive and the Company relating to noncompetition, nonsolicitation, nondisclosure, nondisparagement and/or assignment of inventions. 

(d)    Termination Without Cause. The Company may terminate the Executive’s employment hereunder at any time
without Cause. Any termination by the Company of the Executive’s employment under this Agreement which does not constitute a termination for Cause under Section 3(c) and does not result from the death or disability of the Executive under
Section 3(a) or (b) shall be deemed a termination without Cause. 
 (e)    Termination by the
Executive. The Executive may terminate his employment hereunder at any time for any reason, including but not limited to Good Reason. For purposes of this Agreement, “Good Reason” shall mean that the Executive has complied with the
“Good Reason Process” (hereinafter defined) following the occurrence of any of the following events: (i) a material diminution in the Executive’s responsibilities, authority or duties ; provided that, a change in title,
reporting relationships and/or responsibilities of the Executive could, but 

  
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do not necessarily in and of themselves, individually or in the aggregate, constitute a material diminution for purposes of this Section 3(e), and in all instances, the determination of
whether a material diminution has occurred shall be made by the Company in good faith; (ii) a material diminution in the Executive’s Base Salary except for
across-the-board salary reductions based at least in part on the Company’s financial performance similarly affecting all or substantially all senior management
employees of the Company; (iii) a material change in the geographic location of the principal office of the Company to which the Executive is assigned such that there is an increase of at least thirty (30) additional miles of diving
distance to such new location from the Executive’s principal residence as of such change; or (iv) the material breach of this Agreement by the Company. “Good Reason Process” shall mean that (i) the Executive reasonably
determines in good faith that a “Good Reason” condition has occurred; (ii) the Executive notifies the Company in writing of the first occurrence of the Good Reason condition within sixty (60) days of the first occurrence of such
condition; (iii) the Executive cooperates in good faith with the Company’s efforts, for a period not less than thirty (30) days following such notice (the “Cure Period”), to remedy the condition; (iv) notwithstanding
such efforts, the Good Reason condition continues to exist; and (v) the Executive terminates his employment within 60 days after the end of the Cure Period. If the Company cures the Good Reason condition during the Cure Period, Good Reason
shall be deemed not to have occurred. 
 If the Executive’s employment with the Company is terminated for any reason, the Company shall pay or provide
to the Executive (or to his authorized representative or estate) (i) any Base Salary earned through the Date of Termination, unpaid expense reimbursements (subject to, and in accordance with, Section 2(c) of this Agreement) on or before
the time required by law but in no event more than 30 days after the Executive’s Date of Termination; (ii) accrued but unused vacation and personal days (if applicable and in accordance with Company policy and applicable law); and
(iii) any vested benefits the Executive may have under any employee benefit plan of the Company through the Date of Termination, which vested benefits shall be paid and/or provided in accordance with the terms of such employee benefit plans
(collectively, the “Accrued Benefits”). 
  

	 	4.	 Notice and Date of Termination. 



(a)    Notice of Termination. Except for termination as specified in Section 3(a), any termination of the
Executive’s employment by the Company or any such termination by the Executive shall be communicated by written Notice of Termination to the other party hereto. For purposes of this Agreement, a “Notice of Termination” shall
mean a notice which shall indicate the specific termination provision in this Agreement relied upon. 
 (b)    Date
of Termination. “Date of Termination” shall mean: (i) if the Executive’s employment is terminated by his death, the date of his death; (ii) if the Executive’s employment is terminated on account of disability under
Section 3(b) or by the Company for Cause under Section 3(c), the date on which Notice of Termination is given; (iii) if the Executive’s employment is terminated by the Company under Section 3(d), the date on which a Notice
of Termination is given; (iv) if the Executive’s employment is terminated by the Executive under Section 3(e) without Good Reason, 30 days after the date on which a Notice of Termination is given, and (v) if the
Executive’s employment is terminated by the Executive under Section 3(e) 

  
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for Good Reason, the date on which a Notice of Termination is given after the end of the Cure Period. Notwithstanding the foregoing, in the event that the Executive gives a Notice of Termination
to the Company, the Company may unilaterally accelerate the Date of Termination and such acceleration shall not result in a termination by the Company for purposes of this Agreement.  

5.    Compensation Upon Termination by the Company without Cause or by the Executive for Good Reason Outside the Change
in Control Period. During the Term, if the Executive’s employment is terminated by the Company without Cause as provided in Section 3(d), or the Executive terminates his employment for Good Reason as provided in Section 3(e), each
outside of the Change in Control Period (as defined below), then the Company shall pay the Executive his Accrued Benefits. In addition, subject to (i) the Executive signing a separation agreement and release in a form and manner satisfactory to
the Company, which shall include, without limitation, a general release of claims against the Company and all related persons and entities, a reaffirmation of all of the Executive’s Continuing Obligations (as defined below) and,
in the Company’s sole discretion, a one year post- employment noncompetition covenant, and shall provide that if the Executive breaches any of the Continuing Obligations, all payments of the Severance Amount shall immediately cease (the
“Separation Agreement and Release”), and (ii) the Separation Agreement and Release becoming irrevocable, all within sixty (60) days after the Date of Termination (or such shorter period as set forth in the Separation Agreement
and Release): 
 (a)    the Company shall pay the Executive an amount equal to (A) 0.75 times the
Executive’s Base Salary plus (B) a pro-rata portion of the Executive’s Target Incentive Compensation, based on the number of days that have passed as of the Date of Termination in the year in
which the Date of Termination occurs (the “Severance Amount”); provided that in the event the Executive is entitled to any payments pursuant to the Restrictive Covenants Agreement, the Severance Amount received in any calendar year will be
reduced by the amount the Executive is paid in the same such calendar year pursuant to the Restrictive Covenants Agreement (the “Restrictive Covenants Agreement Setoff”); and 

(b)    if the Executive was participating in the Company’s group health plan immediately prior to the Date of
Termination and elects COBRA health continuation, then the Company shall pay the full monthly COBRA premium for the same level of group health coverage as in effect for the Executive on the Date of Termination until the earliest of the following:
(i) the 9-month anniversary of the Date of Termination; (ii) the Executive’s eligibility for group health coverage through other employment; or (iii) the end of the Executive’s
eligibility under COBRA for continuation coverage for health care. If the payment of any COBRA or health insurance premiums by Company on behalf of Executive as described herein would otherwise violate any applicable nondiscrimination rules or cause
the reimbursement of claims to be taxable under the Patient Protection and Affordable Care Act of 2010, together with the Health Care and Education Reconciliation Act of 2010 (collectively, the “Healthcare Acts”) or Section 105(h) of
the Code, the COBRA premiums paid by the Company shall be treated as taxable payments (subject to customary and required taxes and employment-related deductions) and be subject to imputed income tax treatment to the extent necessary to eliminate any
discriminatory treatment or taxation under the Healthcare Acts or Section 105(h) of the Code. If Company determines in its sole discretion that it cannot provide the COBRA benefits described herein under Company’s health


  
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insurance plan without potentially violating applicable law (including, without limitation, Section 2716 of the Public Health Service Act), Company shall in lieu thereof provide to Executive
a taxable lump-sum payment in an amount equal to the sum of the monthly (or then remaining) COBRA premiums that Executive would be required to pay to maintain Executive’s group health insurance coverage
in effect on the separation date for the remaining portion of the period for which Executive shall receive the payments described in this Section 5(b). 

(c)    The amounts payable under this Section 5 shall be paid out in substantially equal installments in accordance
with the Company’s payroll practice, with the first installment commencing within 60 days after the Date of Termination; provided, however, that if the 60-day period begins in one calendar year and ends
in a second calendar year, the Severance Amount shall begin to be paid in the second calendar year by the last day of such 60-day period; provided, further, that the initial payment shall include a catch-up payment to cover amounts retroactive to the day immediately following the Date of Termination. Each payment pursuant to this Agreement is intended to constitute a separate payment for purposes of Treasury
Regulation Section 1.409A-2(b)(2). 
 6.    Compensation Upon
Termination by the Company without Cause or by the Executive for Good Reason within the Change in Control Period. The provisions of this Section 6 shall apply in lieu of, and expressly supersede, the provisions of Section 5 regarding
severance pay and benefits upon a termination by the Company without Cause or by the Executive for Good Reason if such termination of employment occurs during the three (3) months before through twelve (12) months after the occurrence of
the first event constituting a Change in Control (such period, the “Change in Control Period”). These provisions shall terminate and be of no further force or effect beginning twelve (12) months after the occurrence of a Change in
Control. 
 (a)    Change in Control. If during the Change in Control Period the Executive’s employment is
terminated by the Company without Cause as provided in Section 3(d) or the Executive terminates his employment for Good Reason as provided in Section 3(e), then, subject to the signing of the Separation Agreement and Release by the
Executive and the Separation Agreement and Release becoming irrevocable, all within 60 days after the Date of Termination (or such shorter period as set forth in the Separation Agreement and Release): 

(i)    the Company shall pay the Executive a lump sum in cash in an amount equal to the sum of (A) 1.00
times the Executive’s current Base Salary (or the Executive’s Base Salary in effect immediately prior to the Change in Control, if higher) plus (B) one hundred percent (100%) of the Executive’s Target Incentive Compensation (the
“Change in Control Payment”); provided that the Change in Control Payment shall be reduced by the amount of the Restrictive Covenants Agreement Setoff, if applicable, paid or to be paid in the same calendar year; and 

(ii)    notwithstanding anything to the contrary in any applicable option agreement or stock-based award
agreement, all time-based stock options and other time-based stock-based awards held by the Executive shall immediately accelerate and become fully vested and exercisable or nonforfeitable as of the Date of Termination; and 

  
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 (iii)    if the Executive was participating in the
Company’s group health plan immediately prior to the Date of Termination and elects COBRA health continuation, then the Company shall pay the full monthly COBRA premium for the same level of group health coverage as in effect for the Executive
on the Date of Termination until the earliest of the following: (i) the 12-month anniversary of the Date of Termination; (ii) the Executive’s eligibility for group health coverage through other
employment; or (iii) the end of the Executive’s eligibility under COBRA for continuation coverage for health care. If the payment of any COBRA or health insurance premiums by Company on behalf of Executive as described herein would
otherwise violate any applicable nondiscrimination rules or cause the reimbursement of claims to be taxable under the Healthcare Acts or Section 105(h) of the Code, the COBRA premiums paid by the Company shall be treated as taxable payments
(subject to customary and required taxes and employment-related deductions) and be subject to imputed income tax treatment to the extent necessary to eliminate any discriminatory treatment or taxation under the Healthcare Acts or Section 105(h)
of the Code. If Company determines in its sole discretion that it cannot provide the COBRA benefits described herein under Company’s health insurance plan without potentially violating applicable law (including, without limitation,
Section 2716 of the Public Health Service Act), Company shall in lieu thereof provide to Executive a taxable lump-sum payment in an amount equal to the sum of the monthly (or then remaining) COBRA
premiums that Executive would be required to pay to maintain Executive’s group health insurance coverage in effect on the separation date for the remaining portion of the period for which Executive shall receive the payments described in this
Section 6(b). 
 The amounts payable under this Section 6(a) shall be paid or commence to be paid within sixty (60) days after the Date of
Termination; provided, however, that if the 60-day period begins in one calendar year and ends in a second calendar year, such payment shall be paid or commence to be paid in the second calendar year by the
last day of such 60-day period. 
 (b)    Additional Limitation. 

(i)    Anything in this Agreement to the contrary notwithstanding, in the event that the amount of any
compensation, payment or distribution by the Company to or for the benefit of the Executive, whether paid or payable or distributed or distributable pursuant to the terms of this Agreement or otherwise, calculated in a manner consistent with
Section 280G of the Code and the applicable regulations thereunder (the “Aggregate Payments”), would be subject to the excise tax imposed by Section 4999 of the Code, then the Aggregate Payments shall be reduced (but not below
zero) so that the sum of all of the Aggregate Payments shall be $1.00 less than the amount at which the Executive becomes subject to the excise tax imposed by Section 4999 of the Code; provided that such reduction shall only occur if it would
result in the Executive receiving a higher After Tax Amount (as defined below) than the Executive would receive if the Aggregate Payments were not subject to such reduction. In such event, the Aggregate Payments shall be reduced in the following
order, in each case, in reverse chronological order beginning with the Aggregate Payments that are to be paid the furthest in time from consummation of the transaction that is subject to Section 280G of the Code: (1) cash payments not
subject to Section 409A of the Code; (2) cash payments subject to Section 409A of the Code; (3) equity-based 

  
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payments and acceleration; and (4) non-cash forms of benefits; provided that in the case of all the foregoing Aggregate Payments all amounts or
payments that are not subject to calculation under Treas. Reg. §1.280G-1, Q&A-24(b) or (c) shall be reduced before any amounts that are subject to
calculation under Treas. Reg. §1.280G-1, Q&A-24(b) or (c). 

(ii)    For purposes of this Section 6(b), the “After Tax Amount” means the amount of the
Aggregate Payments less all federal, state, and local income, excise and employment taxes imposed on the Executive as a result of the Executive’s receipt of the Aggregate Payments. For purposes of determining the After Tax Amount, the Executive
shall be deemed to pay federal income taxes at the highest marginal rate of federal income taxation applicable to individuals for the calendar year in which the determination is to be made, and state and local income taxes at the highest marginal
rates of individual taxation in each applicable state and locality, net of the maximum reduction in federal income taxes which could be obtained from deduction of such state and local taxes. 

(iii)    The determination as to whether a reduction in the Aggregate Payments shall be made pursuant to
Section 6(b)(i) shall be made by a nationally recognized accounting firm selected by the Company (the “Accounting Firm”), which shall provide detailed supporting calculations both to the Company and the Executive within 15 business
days of the Date of Termination, if applicable, or at such earlier time as is reasonably requested by the Company or the Executive. Any determination by the Accounting Firm shall be binding upon the Company and the Executive. 

(c)    Definitions. For purposes of this Section 6, Change in Control” shall mean any of the following:

 (i)    any “person,” as such term is used in Sections 13(d) and 14(d) of the Securities
Exchange Act of 1934, as amended (the “Act”) (other than the Company, any of its subsidiaries, or any trustee, fiduciary or other person or entity holding securities under any employee benefit plan or trust of the Company or
any of its subsidiaries), together with all “affiliates” and “associates” (as such terms are defined in Rule 12b-2 under the Act) of such person, shall become the “beneficial
owner” (as such term is defined in Rule 13d-3 under the Act), directly or indirectly, of securities of the Company representing 50 percent or more of the combined voting power of the Company’s
then outstanding securities having the right to vote in an election of the Board (“Voting Securities”) (in such case other than as a result of an acquisition of securities directly from the Company); or 

(ii)    the date a majority of the members of the Board is replaced during any 12- month period by
directors whose appointment or election is not endorsed by a majority of the members of the Board before the date of the appointment or election; or 

(iii)    the consummation of (A) any consolidation or merger of the Company where the stockholders of
the Company, immediately prior to the consolidation or merger, would not, immediately after the consolidation or merger, beneficially own (as such term is defined in Rule 13d-3 under the Act), directly or
indirectly, shares representing 

  
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in the aggregate more than 50 percent of the voting shares of the Company issuing cash or securities in the consolidation or merger (or of its ultimate parent corporation, if any), or
(B) any sale or other transfer (in one transaction or a series of transactions contemplated or arranged by any party as a single plan) of all or substantially all of the assets of the Company. 

Notwithstanding the foregoing, a “Change in Control” shall not be deemed to have occurred for purposes of the foregoing clause
(i) solely as the result of an acquisition of securities by the Company which, by reducing the number of shares of Voting Securities outstanding, increases the proportionate number of Voting Securities beneficially owned by any person to
50 percent or more of the combined voting power of all of the then outstanding Voting Securities; provided, however, that if any person referred to in this sentence shall thereafter become the beneficial owner of any additional shares of Voting
Securities (other than pursuant to a stock split, stock dividend, or similar transaction or as a result of an acquisition of securities directly from the Company) and immediately thereafter beneficially owns 50 percent or more of the combined
voting power of all of the then outstanding Voting Securities, then a “Change in Control” shall be deemed to have occurred for purposes of the foregoing clause (i). 

7.    Section 409A. 

(a)    Anything in this Agreement to the contrary notwithstanding, if at the time of the Executive’s separation from
service within the meaning of Section 409A of the Code, the Company determines that the Executive is a “specified employee” within the meaning of Section 409A(a)(2)(B)(i) of the Code, then to the extent any payment or benefit
that the Executive becomes entitled to under this Agreement on account of the Executive’s separation from service would be considered deferred compensation otherwise subject to the 20 percent additional tax imposed pursuant to
Section 409A(a) of the Code as a result of the application of Section 409A(a)(2)(B)(i) of the Code, such payment shall not be payable and such benefit shall not be provided until the date that is the earlier of (A) six months and one
day after the Executive’s separation from service, or (B) the Executive’s death. If any such delayed cash payment is otherwise payable on an installment basis, the first payment shall include a
catch-up payment covering amounts that would otherwise have been paid during the six- month period but for the application of this provision, and the balance of the installments shall be payable in accordance
with their original schedule. 
 (b)    All in-kind benefits provided and
expenses eligible for reimbursement under this Agreement shall be provided by the Company or incurred by the Executive during the time periods set forth in this Agreement. All reimbursements shall be paid as soon as administratively practicable, but
in no event shall any reimbursement be paid after the last day of the taxable year following the taxable year in which the expense was incurred. The amount of in-kind benefits provided or reimbursable expenses
incurred in one taxable year shall not affect the in-kind benefits to be provided or the expenses eligible for reimbursement in any other taxable year (except for any lifetime or other aggregate limitation
applicable to medical expenses). Such right to reimbursement or in-kind benefits is not subject to liquidation or exchange for another benefit. 

  
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 (c)    To the extent that any payment or benefit described in this
Agreement constitutes “non-qualified deferred compensation” under Section 409A of the Code, and to the extent that such payment or benefit is payable upon the Executive’s termination of
employment, then such payments or benefits shall be payable only upon the Executive’s “separation from service.” The determination of whether and when a separation from service has occurred shall be made in accordance with the
presumptions set forth in Treasury Regulation Section 1.409A-1(h). 

(d)    The parties intend that this Agreement will be administered in accordance with Section 409A of the Code. To
the extent that any provision of this Agreement is ambiguous as to its compliance with Section 409A of the Code, the provision shall be read in such a manner so that all payments hereunder comply with Section 409A of the Code. Each payment
pursuant to this Agreement is intended to constitute a separate payment for purposes of Treasury Regulation Section 1.409A-2(b)(2). The parties agree that this Agreement may be amended, as reasonably
requested by either party, and as may be necessary to fully comply with Section 409A of the Code and all related rules and regulations in order to preserve the payments and benefits provided hereunder without additional cost to either party.

 (e)    The Company makes no representation or warranty and shall have no liability to the Executive or any other
person if any provisions of this Agreement are determined to constitute deferred compensation subject to Section 409A of the Code but do not satisfy an exemption from, or the conditions of, such Section. 

8.    Restrictive Covenants. 

(a)    Restrictive Covenants Agreement. The Executive acknowledges and agrees that in consideration and as a
condition of the commencement of employment by the Company, the Executive is required to enter into the Restrictive Covenants Agreement attached hereto as Exhibit A (the “Restrictive Covenants Agreement”). For
purposes of this Agreement, the obligations in this Section 8 and those that arise in the Restrictive Covenants Agreement and any other agreement relating to confidentiality, assignment of inventions, or other restrictive covenants shall
collectively be referred to as the “Continuing Obligations.” 
 (b)    Third-Party Agreements and
Rights. The Executive hereby confirms that the Executive is not bound by the terms of any agreement with any previous employer or other party which restricts in any way the Executive’s use or disclosure of information or the
Executive’s engagement in any business. The Executive represents to the Company that the Executive’s execution of this Agreement, the Executive’s employment with the Company and the performance of the Executive’s proposed duties
for the Company will not violate any obligations the Executive may have to any such previous employer or other party. In the Executive’s work for the Company, the Executive will not disclose or make use of any information in violation of any
agreements with or rights of any such previous employer or other party, and the Executive will not bring to the premises of the Company any copies or other tangible embodiments of non-public information
belonging to or obtained from any such previous employment or other party. 
 (c)    Litigation and Regulatory
Cooperation. During and after the Executive’s employment, the Executive shall cooperate fully with the Company in the defense or prosecution of any claims or actions now in existence or which may be brought in the future against or on
behalf 

  
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of the Company which relate to events or occurrences that transpired while the Executive was employed by the Company. The Executive’s full cooperation in connection with such claims or
actions shall include, but not be limited to, being available to meet with counsel to prepare for discovery or trial and to act as a witness on behalf of the Company at mutually convenient times. During and after the Executive’s employment, the
Executive also shall cooperate fully with the Company in connection with any investigation or review of any federal, state or local regulatory authority as any such investigation or review relates to events or occurrences that transpired while the
Executive was employed by the Company. The Company shall reimburse the Executive for any reasonable out-of-pocket expenses incurred in connection with the
Executive’s performance of obligations pursuant to this Section 8(c). 
 (d)    Injunction. The
Executive agrees that it would be difficult to measure any damages caused to the Company which might result from any breach by the Executive of the promises set forth in this Section 8, and that in any event money damages would be an inadequate
remedy for any such breach. Accordingly, the Executive agrees that if the Executive breaches, or proposes to breach, any portion of this Agreement, the Company shall be entitled, in addition to all other remedies that it may have, to an injunction
or other appropriate equitable relief to restrain any such breach without showing or proving any actual damage to the Company. 

(e)    Protected Disclosures and Other Protected Actions. Nothing in this Agreement shall be interpreted or applied
to prohibit the Executive from making any good faith report to any governmental agency or other governmental entity (a “Government Agency”) concerning any act or omission that the Executive reasonably believes constitutes a possible
violation of federal or state law or making other disclosures that are protected under the anti-retaliation or whistleblower provisions of applicable federal or state law or regulation. In addition, nothing contained in this Agreement limits the
Executive’s ability to communicate with any Government Agency or otherwise participate in any investigation or proceeding that may be conducted by any Government Agency, including the Executive’s ability to provide documents or other
information, without notice to the Company. In addition, for the avoidance of doubt, pursuant to the federal Defend Trade Secrets Act of 2016, the Executive shall not be held criminally or civilly liable under any federal or state trade secret law
or under this Agreement or the Restrictive Covenants Agreement for the disclosure of a trade secret that (a) is made (i) in confidence to a federal, state, or local government official, either directly or indirectly, or to an attorney; and
(ii) solely for the purpose of reporting or investigating a suspected violation of law; or (b) is made in a complaint or other document filed in a lawsuit or other proceeding, if such filing is made under seal. 

9.    Consent to Jurisdiction. In the event of any dispute regarding the terms or interpretation of this Agreement,
the parties hereby consent to the sole and exclusive jurisdiction of the Superior Court of the Commonwealth of Massachusetts and the United States District Court for the District of Massachusetts. Accordingly, with respect to any such court action,
the Executive (a) submits to the personal jurisdiction and venue of such courts; (b) consents to service of process; and (c) waives any other requirement (whether imposed by statute, rule of court, or otherwise) with respect to
personal jurisdiction, venue or service of process. 

  
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 10.    Indemnification. Executive shall be entitled to
indemnification pursuant to the Officer Indemnification Agreement between the parties effective as of November 2, 2020, 2022 (“Indemnification Agreement”). 

11.    Representations and Warranties. By signing this agreement, Executive represents that Executive has not been
debarred under Subsection (a) or (b) of Section 306 of the United States Federal Food, Drug, and Cosmetic Act (21 U.S. C. 335a); and is not on any FDA clinical investigator enforcement lists (including the (i) Disqualified/Totally
Restricted List, (ii) Restricted List and (iii) Adequate Assurances List). 
 12.    Notice of
Resignation. If Executive elects to resign from employment with the Company, the Executive must provide the Company with written notification of resignation at least three (3) weeks prior to the Executive’s intended resignation date.
The Company may elect to waive all or part of the three (3) week notice period in its sole discretion. 

13.    Integration. This Agreement, together with the Restrictive Covenants Agreement, the Indemnification
Agreement and the Equity Documents, constitutes the entire agreement between the parties with respect to the subject matter hereof and supersedes in all respects all prior agreements between the parties relating to the Executive’s employment
relationship with the Company and/or the ending of that employment relationship. 
 14.    Withholding. All
payments made by the Company to the Executive under this Agreement shall be net of any tax or other amounts required to be withheld by the Company under applicable law. 

15.    Enforceability. If any portion or provision of this Agreement (including, without limitation, any portion or
provision of any section of this Agreement) shall to any extent be declared illegal or unenforceable by a court of competent jurisdiction, then the remainder of this Agreement, or the application of such portion or provision in circumstances other
than those as to which it is so declared illegal or unenforceable, shall not be affected thereby, and each portion and provision of this Agreement shall be valid and enforceable to the fullest extent permitted by law. 

16.    Survival. The provisions of this Agreement shall survive the termination of this Agreement and/or the
termination of the Executive’s employment to the extent necessary to effectuate the terms contained herein. 

17.    Waiver. No waiver of any provision hereof shall be effective unless made in writing and signed by the
waiving party. The failure of any party to require the performance of any term or obligation of this Agreement, or the waiver by any party of any breach of this Agreement, shall not prevent any subsequent enforcement of such term or obligation or be
deemed a waiver of any subsequent breach. 
 18.    Notices. Any notices, requests, demands and other
communications provided for by this Agreement shall be sufficient if in writing and delivered in person or sent by a nationally recognized overnight courier service or by registered or certified mail, postage prepaid, return receipt requested, to
the Executive at the last address the Executive has filed in writing with the Company or, in the case of the Company, at its main offices, attention of the Board. 

  
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 19.    Amendment. This Agreement may be amended or modified only
by a written instrument signed by the Executive and by a duly authorized representative of the Company. 

20.    Effect on Other Plans and Agreements. An election by the Executive to resign for Good Reason under the
provisions of this Agreement shall not be deemed a voluntary termination of employment by the Executive for the purpose of interpreting the provisions of any of the Company’s benefit plans, programs or policies. Nothing in this Agreement shall
be construed to limit the rights of the Executive under the Company’s benefit plans, programs or policies except as otherwise may be provided herein, and except that the Executive shall have no rights to any severance benefits under any Company
severance pay plan, offer letter or otherwise. Except with respect to the Restrictive Covenants Agreement, in the event that the Executive is party to an agreement with the Company providing for payments or benefits under such agreement and this
Agreement, the terms of this Agreement shall govern and the Executive may receive payment under this Agreement only and not both. Further, Section 5 and Section 6 of this Agreement are mutually exclusive and in no event shall the Executive
be entitled to payments or benefits pursuant to Section 5 and Section 6 of this Agreement. 

21.    Governing Law. This is a Massachusetts contract and shall be construed under and be governed in all respects
by the laws of the Commonwealth of Massachusetts, without giving effect to the conflict of laws principles of such Commonwealth. With respect to any disputes concerning federal law, such disputes shall be determined in accordance with the law as it
would be interpreted and applied by the United States Court of Appeals for the First Circuit. 

22.    Assignment. Neither the Executive nor the Company may make any assignment of this Agreement or any interest
in it, by operation of law or otherwise, without the prior written consent of the other; provided, however, that the Company may assign its rights and obligations under this Agreement (including the Restrictive Covenants Agreement) without the
Executive’s consent to any affiliate or to any person or entity with whom the Company shall hereafter effect a reorganization, consolidate with, or merge into or to whom it transfers all or substantially all of its properties or assets;
provided further that if the purchaser in any transaction involving the transfer of all or substantially all of the Company’s assets assumes this Agreement and the Executive accepts a position with the purchaser that is equivalent or better to
his or her position immediately preceding such transaction, then the Executive shall not be entitled to any Severance Amount pursuant to Section 5 or any Change in Control Payment pursuant to Section 6. This Agreement shall
inure to the benefit of and be binding upon the Executive and the Company, and each of the Executive’s and the Company’s respective successors, executors, administrators, heirs and permitted assigns. 

23.    Counterparts. This Agreement may be executed in any number of counterparts, each of which when so executed
and delivered shall be taken to be an original; but such counterparts shall together constitute one and the same document. 

  
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 IN WITNESS WHEREOF, the parties have executed this Agreement, under seal, effective on the
Effective Date. 
  

			
	MAGENTA THERAPEUTICS, INC.
		
	By:	 	 /s/ Jason Gardner

	Its:	 	Chief Executive Officer
	Date:	 	March 3, 2022
	
	EXECUTIVE
	
	 /s/ Stephen Mahoney

	Stephen Mahoney
	
	Date: March 3, 2022



  
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