Document:

EX-10.15

 Exhibit 10.15 

CYTEIR THERAPEUTICS, INC. 

2021 EMPLOYEE STOCK PURCHASE PLAN 
  

	1.	 DEFINED TERMS 

Exhibit A, which is incorporated by reference, defines the terms used in the Plan and sets forth certain operational rules related to
those terms. 
  

	2.	 PURPOSE 

The Plan is intended to enable Eligible Employees to use payroll deductions to purchase shares of Stock, and thereby acquire an interest in the
Company. The Plan is intended to qualify as an “employee stock purchase plan” under Section 423 and to be exempt from the requirements of Section 409A of the Code, and is to be construed consistently with that intent. 

 

	3.	 ADMINISTRATION 

The Plan will be administered by the Administrator. The Administrator has discretionary authority, subject only to the express provisions of
the Plan, to interpret the Plan; to determine eligibility under the Plan; to prescribe forms, rules and procedures relating to the Plan; and to otherwise do all things necessary or desirable to carry out the purposes of the Plan. Determinations of
the Administrator made with respect to the Plan are conclusive and bind all persons. 
  

	4.	 SHARE POOL 

(a) Number of Shares. Subject to adjustment pursuant to Section 17 below, the maximum aggregate number of
shares of Stock available for purchase pursuant to the exercise of Options granted under the Plan will be 300,000 shares (the “Initial Share Pool”). The Initial Share Pool will automatically increase on January 1st of each year beginning in 2022 and continuing through and including 2031 by the least of (i) one (1) percent of the number of shares of Stock outstanding as of such date, (ii) 600,000 shares of
Stock and (iii) the number of shares of Stock determined by the Board on or prior to such date for such year, up to a maximum of 6,300,000 shares in the aggregate (the Initial Share Pool, as it may be so increased, the “Share
Pool”). For purposes of this Section 4(a), shares of Stock shall not be treated as delivered under the Plan, and will not reduce the Share Pool, unless and until, and to the extent, they are actually delivered to a Participant. Without
limiting the generality of the foregoing, if any Option granted under the Plan expires or terminates for any reason without having been exercised in full or ceases for any reason to be exercisable in whole or in part, the unpurchased shares of Stock
subject to such Option will not reduce the Share Pool and will remain available for purchase under the Plan. If, on an Exercise Date, the total number of shares of Stock that would otherwise be purchased upon the exercise of Options granted under
the Plan exceeds the number of shares then available in the Share Pool, the Administrator shall make a pro rata allocation of the shares then available in as uniform a manner as is practicable and as it determines to be equitable. In such event, the
Administrator shall notify each Participant affected by such reduction. 

  
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 (b) Type of Shares. Stock delivered by the Company under the
Plan may be authorized but unissued Stock, treasury Stock or previously issued Stock acquired by the Company. No fractional shares of Stock will be delivered under the Plan. 
  

	5.	 ELIGIBILITY 

(a) Eligibility Requirements. Subject to the limitations contained in the Plan, each Employee
(i) who has been continuously employed by the Company or a Designated Subsidiary, as applicable, for a period of at least ninety (90) calendar days as of the first day of an Option Period, (ii) whose customary Employment with the
Company or a Designated Subsidiary, as applicable, is for more than five (5) months per calendar year, (iii) who customarily works twenty (20) hours or more per week, and (iv) who satisfies the requirements set forth in the Plan,
will be an Eligible Employee. 
 (b) Five Percent Stockholders. No Employee may be granted an
Option under the Plan if, immediately after the Option is granted, the Employee would own (or pursuant to Section 424(d) of the Code would be deemed to own) shares possessing five percent (5%) or more of the total combined voting power or value
of all classes of stock of the Company or of its Parent or Subsidiaries, if any. 
 (c) Additional
Requirements. The Administrator may, for Option Periods that have not yet commenced, establish additional or other eligibility requirements, or amend the eligibility requirements set forth in subsection (a) above, in each
case, consistent with the requirements of Section 423. 
  

	6.	 OPTION PERIODS 

The Plan will generally be implemented by a series of separate offerings referred to as “Option Periods”. Unless otherwise
determined by the Administrator, the Option Periods will be successive periods of approximately six (6) months commencing on the first Business Day in January and July of each year, anticipated to be on or around January 1 and July 1,
and ending approximately six (6) months later on the last Business Day in June or December, as applicable, of each year, anticipated to be on or around June 30 and December 31. The last Business Day of each Option Period will be an
“Exercise Date”. The Administrator may change the Exercise Date, the commencement date, the ending date and the duration of each Option Period, in each case, to the extent permitted by Section 423; provided, however,
that no Option may be exercised after 27 months from its grant date. 
  

	7.	 OPTION GRANTS 

Subject to the limitations set forth herein and the Maximum Share Limit (as defined below), on the first day of an Option Period, each
Participant will automatically be granted an Option to purchase shares of Stock on the Exercise Date; provided, however, that no Participant will be granted an Option under the Plan that permits the Participant’s right to purchase
shares of Stock under the Plan and under all other employee stock purchase plans of the Company and its Parent and Subsidiaries, if any, to accrue at a rate that exceeds $25,000 in Fair Market Value (or such other maximum as may be prescribed from
time to time by the Code) for each calendar year during which any Option granted to such Participant is outstanding at any time, as determined in accordance with Section 423(b)(8) of the Code. 

  
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	8.	 PARTICIPATION 

(a) Election. To participate in an Option Period, an Eligible Employee must execute and deliver to the
Administrator an election form, in accordance with the procedures prescribed by, and in a form acceptable to, the Administrator. Such election form must be delivered not later than five (5) Business Days prior to the first day of an Option
Period, or such other time as specified by the Administrator. An Eligible Employee will become a Participant as of the first day of the Option Period for which he or she timely delivered such election form and will remain a Participant with respect
to subsequent Option Periods until his or her participation in the Plan is terminated as provided herein. 
 (b) Election
Amount. Each election form will authorize payroll deductions as a whole percentage from one (1) to fifteen (15) percent of the employee’s Eligible Compensation per payroll period, to be deducted from the Eligible
Employee’s pay during each payroll period occurring during the applicable Option Period. 
 (c) Payroll Deduction
Account. All payroll deductions made pursuant to this Section 8 will be credited to the Participant’s Account. Amounts credited to a Participant’s Account will not be required to be set aside in trust or
otherwise segregated from the Company’s general assets. 
 (d) Changes to Election for Current Option
Period. During an Option Period, elections and rates of contributions may not be increased. A Participant may decrease his or her rates of contributions during an Option Period, or may terminate his or her participation
in the Plan by canceling his or her Option in accordance with Section 14 below. 
 (e) Changes to Election for Subsequent
Option Periods. A Participant’s election form will remain in effect for subsequent Option Periods unless the Participant files a new election form not later than five (5) Business Days prior to the first day of the
subsequent Option Period (or such other time as specified by the Administrator) or the Participant’s Option is cancelled in accordance with the Plan. 
  

	9.	 METHOD OF PAYMENT 

A Participant must pay for shares of Stock purchased upon the exercise of an Option with the accumulated payroll deductions credited to the
Participant’s Account.     
  

	10.	 PURCHASE PRICE 

The Purchase Price of shares of Stock issued pursuant to the exercise of an Option on each Exercise Date will be eighty-five percent (85%) (or
such other percentage specified by the Administrator to the extent permitted under Section 423) of the lesser of (i) the Fair Market Value of a share of Stock on the date on which the Option was granted (i.e., the first day of the
Option Period) and (ii) the Fair Market Value of a share of Stock on the date on which the Option is deemed exercised (i.e., the Exercise Date). 

  
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	11.	 EXERCISE OF OPTIONS 

(a) Purchase of Shares. Subject to the limitations set forth herein, with respect to each Option
Period, on each Exercise Date, each Participant will be deemed to have exercised his or her Option and the accumulated payroll deductions credited to the Participant’s Account will be applied to purchase the greatest number of shares of Stock
(rounded down to the nearest whole share) that can be purchased with such Account balance at the applicable Purchase Price; provided, however, that no more than 5,000 shares of Stock may be purchased by a Participant on any Exercise Date, or
such other number as the Administrator may prescribe in accordance with Section 423 (the “Maximum Share Limit”). As soon as practicable thereafter, the shares of Stock so purchased will be placed, in book-entry form, into a
recordkeeping account in the name of the Participant. Any accumulated payroll deductions in a Participant’s Account that are not sufficient to purchase a whole share of Stock will be retained in the Participant’s Account for the subsequent
Option Period, subject to earlier withdrawal by the Participant as provided in Section 14 below. 
 (b) Return of Account
Balance. Except as provided in Section 11(a) above, any accumulated payroll deductions in a Participant’s Account for an Option Period that are not used to purchase shares of Stock, whether because of the
Participant’s withdrawal from participation in an Option Period or for any other reason, will be returned to the Participant (or his or her designated beneficiary or legal representative, as applicable), without interest, as soon as
administratively practicable after such withdrawal or other event, as applicable. If the Participant’s accumulated payroll deductions for an Option Period would otherwise enable the Participant to purchase shares of Stock in excess of the
Maximum Share Limit or the maximum Fair Market Value set forth in Section 7 above, the excess of the amount of the accumulated payroll deductions over the aggregate Purchase Price of the shares of Stock actually purchased will be returned to
the Participant, without interest, as soon as administratively practicable after such Exercise Date. 
  

	12.	 INTEREST 

No interest will accrue or be payable on any amount held in the Account of any Participant. 

 

	13.	 TAXES 

Payroll deductions will be made on an after-tax basis. The Administrator will have the right, as a
condition to exercising an Option, to make such provision as it deems necessary to satisfy its obligations to withhold federal, state, local or other taxes incurred by reason of the purchase or disposition of shares of Stock under the Plan. In the
Administrator’s discretion and subject to applicable law, such tax obligations may be satisfied in whole or in part by delivery of shares of Stock to the Company, including shares of Stock purchased under the Plan, valued at Fair Market Value,
but not in excess of the maximum withholding amount consistent with the award being subject to equity accounting treatment under the Accounting Rules. 

  
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	14.	 CANCELLATION AND WITHDRAWAL 

A Participant who holds an Option under the Plan may cancel all (but not less than all) of such Option and terminate his or her participation
in the Plan by delivering a notice to the Administrator in accordance with the procedures prescribed by, and in a form acceptable to, the Administrator. To be effective with respect to an upcoming Exercise Date, such notice must be delivered not
later than five (5) Business Days prior to such Exercise Date (or such other time as specified by the Administrator). Upon such termination and cancellation, the balance in the Participant’s Account will be returned to the Participant,
without interest, as soon as administratively practicable thereafter. For the avoidance of doubt, a Participant who reduces his or her rate of payroll deductions for future payroll periods to zero percent (0%) in accordance with Section 8 above
will be deemed to have terminated his or her participation in the Plan as to all current and future Option Periods, unless and until the Participant has delivered a new election for a subsequent Option Period in accordance with the rules of
Section 8 above. 
  

	15.	 TERMINATION OF EMPLOYMENT 

Upon the termination of a Participant’s employment with the Company or a Designated Subsidiary, as applicable, for any reason (including
the death of a Participant during an Option Period prior to an Exercise Date) or in the event the Participant ceases to qualify as an Eligible Employee, the Participant’s participation in the Plan will terminate, any Option held by the
Participant under the Plan will be canceled, the balance in the Participant’s Account will be returned to the Participant (or his or her estate or designated beneficiary in the event of the Participant’s death), without interest, as soon
as administratively practicable thereafter, and the Participant will have no further rights under the Plan. 
  

	16.	 EQUAL RIGHTS; RIGHTS NOT TRANSFERABLE 

All Participants granted Options in during an Option Period under the Plan will have the same rights and privileges, consistent with the
requirements set forth in Section 423. Any Option granted under the Plan will be exercisable during the Participant’s lifetime only by him or her and may not be sold, pledged, assigned, or transferred in any manner. In the event any
Participant violates or attempts to violate the terms of this Section 16, as determined by the Administrator in its sole discretion, any Options granted to the Participant under the Plan may be terminated by the Company and, upon the return to
the Participant of the balance of his or her Account, without interest, all of the Participant’s rights under the Plan will terminate. 
  

	17.	 CHANGE IN CAPITALIZATION; COVERED TRANSACTION 

(a) Change in Capitalization. In the event of a stock dividend, stock split or combination of shares (including a
reverse stock split), recapitalization or other change in the Company’s capital structure that constitutes an equity restructuring within the meaning of the Accounting Rules, the Administrator shall make appropriate adjustments to the aggregate
number and type of shares of stock available under the Plan, the number and type of shares of stock granted under any outstanding Options, the maximum number and type of shares of stock purchasable under any outstanding Option, and/or the Purchase
Price under any outstanding Option, in any case, in a manner that complies with Section 423. 

  
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 (b) Covered Transaction. In the event of a Covered
Transaction, the Administrator may, in its discretion, (i) provide that each outstanding Option will be assumed or exchanged for a substitute option granted by the acquiror or successor corporation or by a parent or subsidiary of the acquiror
or successor corporation; (ii) cancel each outstanding Option and return the balances in Participants’ Accounts to the Participants; and/or (iii) terminate the Option Period on or before the date of the Covered Transaction. 

 

	18.	 AMENDMENT AND TERMINATION 

(a) Amendment. The Administrator reserves the right at any time or times to amend the Plan to any
extent and in any manner it may deem advisable; provided, that any amendment that would be treated as the adoption of a new plan for purposes of Section 423 will have no force or effect unless approved by the stockholders of the Company
within twelve (12) months before or after its adoption. 
 (b) Termination. The Administrator
reserves the right at any time or times to suspend or terminate the Plan. In connection therewith, the Administrator may provide, in its sole discretion, either that outstanding Options will be exercisable on the Exercise Date for the applicable
Option Period or on such earlier date as the Administrator may specify (in which case such earlier date will be treated as the Exercise Date for the applicable Option Period), or that the balance of each Participant’s Account will be returned
to the Participant, without interest. 
  

	19.	 APPROVALS 

Stockholder approval of the Plan will be obtained prior to the date that is twelve (12) months after the date the Plan is approved by the
Board. In the event that the Plan has not been approved by the stockholders of the Company prior to the one-year anniversary of the date the Plan is approved by the Board, all Options granted under the Plan
will be cancelled and become null and void. 
 Notwithstanding anything herein to the contrary, the obligation of the Company to issue and
deliver shares of Stock under the Plan will be subject to the approval required of any governmental authority in connection with the authorization, issuance, sale or transfer of such shares of Stock and to any requirements of any national securities
exchange applicable thereto, and to compliance by the Company with other applicable legal requirements in effect from time to time. 
  

	20.	 PARTICIPANTS’ RIGHTS AS STOCKHOLDERS AND EMPLOYEES 

A Participant will have no rights or privileges as a stockholder of the Company and will not receive any dividends in respect of any shares of
Stock covered by an Option granted hereunder until such Option has been exercised, full payment has been made for such shares, and the shares have been issued to the Participant. 

Nothing contained in the Plan will be construed as giving to any Employee the right to be retained in the employ of the Company or any
Designated Subsidiary or as interfering with the right of the Company or any Designated Subsidiary to discharge, promote, demote or otherwise re-assign any Employee from one position to another within the
Company or any Designated Subsidiary or any other Subsidiary at any time. 

  
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	21.	 RESTRICTIONS ON TRANSFER; INFORMATION REGARDING DISQUALIFYING DISPOSITIONS 

(a) Restrictions on Transfer. Shares of Stock purchased under the Plan may, in the discretion of the Administrator,
be subject to a restriction prohibiting the transfer, sale, pledge or alienation of such shares of Stock by a Participant, other than by will or by the laws of descent and distribution, for such period following such purchase as may be determined by
the Administrator. 
 (b) Disqualifying Dispositions. By electing to participate in the Plan, each Participant
agrees (or will be deemed to have agreed) to provide such information about any transfer of Stock acquired under the Plan that occurs within two years after the first day of the Option Period in which such Stock was acquired and within one year
after the day such Stock was purchased as may be requested by the Company or any Designated Subsidiary in order to assist it in complying with applicable tax laws. 
  

	22.	 MISCELLANEOUS 

(a) Waiver of Jury Trial. By electing to participate in the Plan, each Participant waives (or will be deemed to
have waived), to the maximum extent permitted under applicable law, any right to a trial by jury in any action, proceeding or counterclaim concerning any rights under the Plan or with respect to any Option, or under any amendment, waiver, consent,
instrument, document or other agreement delivered or which in the future may be delivered in connection therewith, and agrees (or will be deemed to have agreed) that any such action, proceedings or counterclaim will be tried before a court and not
before a jury. By electing to participate in the Plan, each Participant certifies that no officer, representative, or attorney of the Company has represented, expressly or otherwise, that the Company would not, in the event of any action, proceeding
or counterclaim, seek to enforce the foregoing waivers. Notwithstanding anything to the contrary in the Plan, nothing herein is to be construed as limiting the ability of the Company and a Participant to agree to submit any dispute arising under the
terms of the Plan or in respect of any Option to binding arbitration or as limiting the ability of the Company to require any individual to agree to submit any dispute to binding arbitration as a condition of receiving an Option hereunder. 

(b) Limitation of Liability. Notwithstanding anything to the contrary in the Plan, neither the Company, nor any of
its subsidiaries, nor the Administrator, nor any person acting on behalf of the Company, any of its subsidiaries, or the Administrator, will be liable to any Participant or to any other person by reason of any acceleration of income, any additional
tax, or any penalty, interest or other liability asserted by reason of the failure of the Plan or any Option to satisfy the requirements of Section 423, or otherwise asserted with respect to the Plan or any Option. 

(c) Unfunded Plan. The Company’s obligations under the Plan are unfunded, and no Participant will have any
right to specific assets of the Company in respect of any Option. 

  
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Participants will be general unsecured creditors of the Company with respect to any amounts due or payable under the Plan. 

 

	23.	 ESTABLISHMENT OF SUB-PLANS 

Notwithstanding the foregoing or any provision of the Plan to the contrary, consistent with the requirements of Section 423, the
Administrator may, in its sole discretion, amend the terms of the Plan, or an offering and/or provide for separate offerings under the Plan in order to, among other things, reflect the impact of local law outside of the United States as applied to
one or more Eligible Employees of a Designated Subsidiary and may, where appropriate, establish one or more sub-plans to reflect such amended provisions. 

 

	24.	 GOVERNING LAW 

(a) Certain Requirements of Corporate Law. Options and shares of Stock will be granted, issued and administered
consistent with the requirements of applicable Delaware law relating to the issuance of stock and the consideration to be received therefor, and with the applicable requirements of the stock exchanges or other trading systems on which the Stock is
listed or entered for trading, in each case as determined by the Administrator. 
 (b) Other Matters. Except as
otherwise provided by the express terms of a sub-plan described in Section 23 above or as provided in Section 24(a) above, the domestic substantive laws of the Commonwealth of Massachusetts govern
the provisions of the Plan and of Options under the Plan and all claims or disputes arising out of or based upon the Plan or any Option or relating to the subject matter hereof or thereof without giving effect to any choice or conflict of laws
provision or rule that would cause the application of the domestic substantive laws of any other jurisdiction. 
 (c)
Jurisdiction. By electing to participate in the Plan, each Participant agrees or will be deemed to have agreed to (i) submit irrevocably and unconditionally to the jurisdiction of the federal and state courts located
within the geographic boundaries of the United States District Court for the District of Massachusetts for the purpose of any suit, action or other proceeding arising out of or based upon the Plan or any Option; (ii) not commence any suit,
action or other proceeding arising out of or based upon the Plan or any Option, except in the federal and state courts located within the geographic boundaries of the United States District Court for the District of Massachusetts; and
(iii) waive, and not assert, by way of motion as a defense or otherwise, in any such suit, action or proceeding, any claim that he or she is not subject personally to the jurisdiction of the above-named courts that his or her property is exempt
or immune from attachment or execution, that the suit, action or proceeding is brought in an inconvenient forum, that the venue of the suit, action or proceeding is improper or that the Plan or any Option or the subject matter thereof may not be
enforced in or by such court. 
  

	25.	 EFFECTIVE DATE AND TERM 

The Plan will become effective upon adoption of the Plan by the Board and no rights will be granted hereunder after the earliest to occur of
(i) the Plan’s termination by the Administrator; (ii) the issuance of all shares of Stock available for issuance under the Plan and (iii) the day before the ten (10)-year anniversary of the date the Board approves the Plan. 

  
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 EXHIBIT A 

Definition of Terms 

The following terms, when used in the Plan, have the meanings and are subject to the provisions set forth below: 

“401(k) Plan”: A savings plan qualifying under Section 401(k) of the Code that is sponsored by the Company or one of its
Subsidiaries for the benefit of its employees. 
 “Account”: A notional payroll deduction account maintained in the
Participant’s name in the records of the Company. 
 “Accounting Rules”: Financial Accounting Standards Board
Accounting Standards Codification Topic 718, or any successor provision. 
 “Administrator”: The Compensation Committee,
except that the Board may at any time act in the capacity of the Administrator (including with respect to such matters that are not delegated to the Compensation Committee by the Board (whether pursuant to committee charter or otherwise), if
applicable). The Compensation Committee (or the Board) may delegate (i) to one or more of its members (or one or more other members of the Board) such of its duties, powers and responsibilities as it may determine and (ii) to such
Employees or other persons as it determines such ministerial tasks as it deems appropriate. For purposes of the Plan, the term “Administrator” will include the Board, the Compensation Committee, and the person or persons delegated
authority under the Plan to the extent of such delegation, as applicable. 
 “Board”: The Board of Directors of the
Company. 
 “Business Day”: Any day on which the established national exchange or trading system (including the Nasdaq
Global Market) on which the Stock is traded is available and open for trading. 
 “Code”: The U.S. Internal Revenue Code of
1986, as from time to time amended and in effect, or any successor statute as from time to time in effect. 
 “Company”:
Cyteir Therapeutics, Inc., a Delaware corporation. 
 “Compensation Committee”: The Compensation Committee of the Board.

 “Covered Transaction”: Any of (i) a consolidation, merger or similar transaction or series of related transactions,
including a sale or other disposition of stock, in which the Company is not the surviving corporation or which results in the acquisition of all or substantially all of the Company’s then outstanding common stock by a single person or entity or
by a group of persons and/or entities acting in concert; (ii) a sale or transfer of all or substantially all the Company’s assets; (iii) a dissolution or liquidation of the Company or (iv) any other transaction the Administrator
determines to be a Covered Transaction. Where a Covered Transaction involves a tender offer that is reasonably expected to be followed by a merger described in clause (i) (as determined by the Administrator), the Covered Transaction will be deemed
to have occurred upon consummation of the tender offer. 

  
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 “Designated Subsidiary”: A Subsidiary of the Company that has been
designated by the Board or the Compensation Committee from time to time as eligible to participate in the Plan as set forth on Exhibit B, as amended from time to time (with the initial list of Designated Subsidiaries as of the date of
adoption of the Plan by the Board set forth on Exhibit B). For the avoidance of doubt, any Subsidiary of the Company, whether or not a Subsidiary on the date the Plan was adopted by the Board, shall be eligible to be designated as a
Designated Subsidiary hereunder. 
 “Eligible Compensation”: Regular base salary and regular base wages. Eligible
Compensation will not be reduced by any income or employment tax withholdings or any contributions by the Employee to a 401(k) Plan or a plan under Section 125 of the Code, but will be reduced by any contributions made on the Employee’s
behalf by the Company or any Subsidiary to any deferred compensation plan or welfare benefit program now or hereafter established. 

“Eligible Employee”: Any Employee who meets the eligibility requirements set forth in the Plan. 

“Employee”: Any person who is employed by the Company or a Designated Subsidiary. For the avoidance of doubt, independent
contractors and consultants are not “Employees”. 
 “Exercise Date”: The date set forth in the Plan or otherwise
designated by the Administrator with respect to a particular Option Period on which a Participant will be deemed to have exercised the Option granted to him or her for such Option Period. 

“Fair Market Value”: As of a particular date, (i) the closing price for a share of Stock reported on the Nasdaq Global
Market (or any other national securities exchange on which the Stock is then listed) for that date or, if no closing price is reported for that date, the closing price on the immediately preceding date on which a closing price was reported or
(ii) in the event that the Stock is not traded on a national securities exchange, the fair market value of a share of Stock determined by the Administrator consistent with the rules of Section 422 and Section 409A to the extent
applicable. 
 “Maximum Share Limit”: The meaning set forth in Section 11 of the Plan. 

“Option”: An option granted pursuant to the Plan entitling the holder to acquire shares of Stock upon payment of the Purchase
Price per share of Stock. 
 “Option Period”: An offering period established in accordance with Section 6 of the Plan.

 “Parent”: A “parent corporation” as defined in Section 424(e) of the Code. 

  
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 “Participant”: An Eligible Employee who elects to participate in an Option
Period under the Plan. 
 “Plan”: This Cyteir Therapeutics, Inc. 2021 Employee Stock Purchase Plan, as from time to time
amended and in effect. 
 “Purchase Price”: The price per share of Stock with respect to an Option Period determined in
accordance with Section 10 of the Plan. 
 “Section 423”: Section 423 of the Code and the
regulations thereunder. 
 “Stock”: Common stock of the Company, par value $0.001 per share. 

“Subsidiary”: A “subsidiary corporation” as defined in Section 424(f) of the Code. 

  
 A-3 

 EXHIBIT B 

Designated Subsidiaries 

(as of June 10, 2021) 

Cyteir Securities CorporationEX-10.16

 Exhibit 10.16 

CYTEIR THERAPEUTICS, INC. 

2021 CASH INCENTIVE PLAN 
  

	1.	 DEFINED TERMS 

Exhibit A, which is incorporated by reference, defines certain terms used in the Plan and sets forth operational rules related to those
terms. 
  

	2.	 PURPOSE 

The Plan has been established to advance the interests of the Company by providing for the grant of cash-based incentive Awards. 

 

	3.	 ADMINISTRATION 

The Plan will be administered by the Administrator. The Administrator has discretionary authority, subject only to the express provisions of
the Plan, to interpret the Plan and any Award; to determine eligibility for and grant Awards; to adjust the Performance Criterion or Criteria applicable to Awards; to determine, modify or waive the terms and conditions of any Award; to prescribe
forms, rules and procedures relating to the Plan and Awards; and to otherwise do all things necessary or desirable to carry out the purposes of the Plan or any Award. Determinations of the Administrator made with respect to the Plan or any Award are
conclusive and bind all persons. 
  

	4.	 ELIGIBILITY AND PARTICIPATION 

The Administrator may select Participants from among executive officers and key employees of the Company and its subsidiaries. 

 

	5.	 GRANT OF AWARDS 

A Participant who is granted an Award will be entitled to a payment, if any, in respect of the Award only if all conditions to payment have
been satisfied in accordance with the Plan and the terms of the Award, except as otherwise determined by the Administrator in accordance with Section 6 below. By accepting (or being deemed to have accepted) an Award, the Participant agrees (or
will be deemed to have agreed) to the terms and condition of the Award and the Plan. The Administrator will select the Participants, if any, who receive Awards for each Performance Period and, for each Award, will establish the following: 

(a) the Performance Criterion or Criteria applicable to the Award; 

(b) the amount or amounts that will be payable (subject to adjustment in accordance with Section 6 below) if the Performance
Criterion or Criteria are achieved in whole or in part; and 
 (c) such other terms and conditions as the Administrator determines
with respect to the Award. 

	6.	 DETERMINATION OF PERFORMANCE AND AMOUNTS PAYABLE 

As soon as practicable after the end of the applicable Performance Period, the Administrator will determine whether and to what extent, if at
all, the Performance Criterion or Criteria applicable to each Award granted for such Performance Period have been satisfied. The Administrator will then determine the amount payable, if any, under each Award. The Administrator may, in its sole
discretion, after determining the amount that would otherwise be payable in respect of any Award, adjust the actual payment, if any, to be made with respect to such Award. The Administrator may exercise the discretion described in the immediately
preceding sentence either in individual cases or in ways that affect more than one Participant. In each case, the Administrator’s discretionary determination, which may affect different Awards differently, is conclusive and will bind all
persons. 
  

	7.	 PAYMENTS 

The Administrator will determine the payment dates for Awards under the Plan. Except as otherwise determined by the Administrator: 

(a) all payments under the Plan will be made, if at all, not later than the later of (i) two and
one-half months following the end of the Company’s fiscal year in which the Performance Period ends and (ii) March 15th of the calendar year
immediately following the calendar year in which the Performance Period ends; 
 (b) payment will not be made with respect to an Award
unless the Participant has remained employed with the Company and its subsidiaries through the date of payment; and 
 (c) awards
under the Plan are intended to qualify for exemption from Section 409A of the Code and shall be construed and administered accordingly. 

Notwithstanding anything herein to the contrary, the Administrator may authorize elective deferrals of any Award payments in accordance with the deferral
rules of Section 409A. 
  

	8.	 TAX WITHHOLDING 

All payments under the Plan will be reduced by all tax and other amounts required to be withheld with respect to the payment. Any amounts
withheld pursuant to this Section 8 will be treated as though such amounts had been paid directly to the applicable Participant. 
  

	9.	 AMENDMENT AND TERMINATION 

The Administrator may at any time or times amend the Plan or any outstanding Award for any purpose which may at the time be permitted by
applicable law, and may at any time terminate the Plan as to any future grants of Awards. For the avoidance of doubt, no adjustment to any Award or determination made with respect to any Award, in
each case, in accordance with the terms of the Plan will be treated as an amendment that requires the consent of any Participant. 

  
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	10.	 RECOVERY OF COMPENSATION 

The Administrator may provide in any case that any outstanding Award and any amounts received in respect of any Award will be subject to
forfeiture and disgorgement to the Company, with interest and other related earnings, if the Participant to whom the Award was granted is not in compliance with any provision of the Plan or any applicable Award or any
non-competition, non-solicitation, no-hire, non-disparagement, confidentiality, invention
assignment or other restrictive covenant by which he or she is bound. In addition, each Award will be subject to any policy of the Company or any of its affiliates that provides for forfeiture, disgorgement or clawback with respect to incentive
compensation that includes Awards under the Plan and will be further subject to forfeiture and disgorgement to the extent required by law or applicable stock exchange listing standards, including, without limitation, Section 10D of the
Securities Exchange Act of 1934, as amended. Each Participant, by accepting (or being deemed to have accepted) an Award under the Plan, agrees (or will be deemed to have agreed) to the provisions of this Section 10 and any clawback, recoupment
or similar policy of the Company or any of its subsidiaries with respect to incentive compensation that includes Awards under the Plan and further agrees (or will be deemed to have further agreed) to cooperate fully with the Administrator to
effectuate any forfeiture or disgorgement described in this Section 10. Neither the Administrator nor the Company nor any other person, other than the Participant, will be responsible for any adverse tax or other consequences to a Participant
that may arise in connection with this Section 10. 
  

	11.	 MISCELLANEOUS 

(a) Waiver of Jury Trial. By accepting (or being deemed to have accepted) an Award under the Plan, each Participant
waives (or will be deemed to have waived), to the maximum extent permitted under applicable law, any right to a trial by jury in any action, proceeding or counterclaim concerning any rights under the Plan or any Award, or under any amendment,
waiver, consent, instrument, document or other agreement delivered or which in the future may be delivered in connection therewith, and agrees (or will be deemed to have agreed) that any such action, proceedings or counterclaim will be tried before
a court and not before a jury. By accepting (or being deemed to have accepted) an Award under the Plan, each Participant certifies that no officer, representative, or attorney of the Company has represented, expressly or otherwise, that the Company
would not, in the event of any action, proceeding, or counterclaim, seek to enforce the foregoing waivers. Notwithstanding anything to the contrary in the Plan, nothing herein is to be construed as limiting the ability of the Company and a
Participant to agree to submit any dispute arising under the terms of the Plan or any Award to binding arbitration or as limiting the ability of the Company to require any individual to agree to submit such disputes to binding arbitration as a
condition of receiving an Award hereunder. 
  

  
 3 

 (b) Section 409A. Without
limiting the generality of Section 11(c) hereof, each Award will contain such terms as the Administrator determines and will be construed and administered, such that the Award either qualifies for an exemption from the requirements of
Section 409A or satisfies such requirements. Notwithstanding anything to the contrary in the Plan or any Award agreement, the Administrator may unilaterally amend, modify or terminate the Plan or any outstanding Award, including but not limited
to changing the form of the Award, if the Administrator determines that such amendment, modification or termination is necessary or desirable to avoid the imposition of an additional tax, interest or penalty under Section 409A. If a Participant
is determined on the date of the Participant’s termination of Employment to be a “specified employee” within the meaning of that term under Section 409A(a)(2)(B) of the Code, then, with regard to any payment that is considered
nonqualified deferred compensation under Section 409A, to the extent applicable, payable on account of a “separation from service”, such payment will be made or provided on the date that is the earlier of (i) the first business
day following the expiration of the six-month period measured from the date of such “separation from service” and (ii) the date of the Participant’s death.    For
purposes of Section 409A, each payment made under the Plan or any Award will be treated as a separate payment. 
 (c)
Limitation of Liability. Notwithstanding anything to the contrary in the Plan or any Award, neither the Company, nor any of its subsidiaries, nor the Administrator, nor any person acting on behalf of the Company, any of its
subsidiaries, or the Administrator, will be liable to any Participant or to any other person by reason of any acceleration of income, any additional tax, or any penalty, interest or other liability asserted by reason of the failure of an Award to
satisfy the requirements of Section 409A or by reason of Section 4999 of the Code, or otherwise asserted with respect to any Award. 

(d) Unfunded Plan. The Company’s obligations under the Plan are unfunded, and no Participant will have any
right to specific assets of the Company in respect of any Award. Participants will be general unsecured creditors of the Company with respect to any amounts due or payable under the Plan. 

(e) Governing Law. Except as otherwise provided by the express terms of an Award, the domestic substantive laws of
the Commonwealth of Massachusetts govern the provisions of the Plan and any Award, without giving effect to any choice or conflict of laws provision or rule that would cause the application of the domestic substantive laws of any other jurisdiction.

 (f) Jurisdiction. By accepting (or being deemed to have accepted) an Award, each Participant agrees (or will
be deemed to have agreed) to (i) submit irrevocably and unconditionally to the jurisdiction of the federal and state courts located within the geographic boundaries of the United States District Court for the District of Massachusetts for the
purpose of any suit, action or other proceeding arising out of or based upon the Plan or any Award; (ii) not commence any suit, action or other proceeding arising out of or based upon the Plan or any Award, except in the federal and state
courts located within the geographic boundaries of the United States District Court for the District of Massachusetts; and (iii) waive, and not assert, by way of motion as a defense or otherwise, in any such suit, action or proceeding, any
claim that he or she is not subject personally to the jurisdiction of the above-named courts, that his or her property is exempt or immune from attachment or execution, that the suit, action or proceeding is brought in an inconvenient forum, that
the venue of the suit, action or proceeding is improper or that the Plan or any Award or the subject matter thereof may not be enforced in or by such court.  

(g) Other Compensation Arrangements. The existence of the Plan or the grant of any Award will not affect the right
of the Company or any of its subsidiaries to grant any person bonuses or other compensation in addition to Awards under the Plan. 

  
 4 

 (h) Rights Limited. Nothing in the Plan or any Award will be
construed as giving any person the right to be granted an Award or to continued employment or service with the Company or any of its subsidiaries. The loss of any Award will not constitute an element of damages in the event of a termination of a
Participant’s employment for any reason, even if the termination is in violation of an obligation of the Company or any of its subsidiaries to the Participant. 

(i) Effective Date. The Plan will be effective upon adoption of the Plan by the Administrator and will supersede
and replace the Company’s annual cash bonus program with respect to awards granted to eligible executive officers and employees for fiscal years beginning after the date of adoption. 

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 5 

 EXHIBIT A 

Definition of Terms 

The following terms, when used in the Plan, have the meanings and are subject to the provisions set forth below: 

“Administrator”: The Compensation Committee, except that the Board may at any time act in the capacity of the Administrator.
The Compensation Committee (or the Board) may delegate (i) to one or more of its members (or one or more other members of the Board) such of its duties, powers and responsibilities as it may determine; (ii) to one or more officers of the
Company the power to grant Awards to the extent permitted by applicable law; and (iii) to such Employees or other persons as it determines such ministerial tasks as it deems appropriate. For purposes of the Plan, the term
“Administrator” will include the Board, the Compensation Committee, and the person or persons delegated authority under the Plan to the extent of such delegation, as applicable. 

“Award”: A cash bonus award that is granted to a Participant with respect to a Performance Period. An Award opportunity may
be expressed as a percentage of the Participant’s base salary, as a fixed dollar amount, or in such other form determined by the Administrator. 

“Board”: The Board of Directors of the Company. 

“Code”: The U.S. Internal Revenue Code of 1986, as from time to time amended and in effect, or any successor statute as from
time to time in effect. 
 “Company”: Cyteir Therapeutics, Inc., a Delaware corporation. 

“Compensation Committee”: The Compensation Committee of the Board. 

“Participant”: A person who is granted an Award under the Plan. 

“Performance Criteria”: Specified criteria, other than the mere continuation of employment or the mere passage of time, the
satisfaction of which is a condition for the grant, exercisability, vesting, or full enjoyment of an Award. A Performance Criterion and any targets with respect thereto need not be based upon an increase, a positive or improved result, or avoidance
of loss and may be applied to a Participant individually, or to a business unit or division of the Company or to the Company as a whole. A Performance Criterion may also be based on individual performance and/or subjective performance criteria (or a
combination of any of the foregoing criteria described in this definition of “Performance Criteria”). The Administrator may provide that one or more of the Performance Criteria applicable to such Award will be adjusted in a manner to
reflect events (for example, but without limitation, acquisitions or dispositions) occurring during the Performance Period that affect the applicable Performance Criterion or Criteria. 

“Performance Period”: A specified performance period, consisting of the Company’s fiscal year or such other period as
the Administrator determines. 

  
 A-1 

 “Plan”: This Cyteir Therapeutics, Inc. 2021 Cash Incentive Plan, as from
time to time amended and in effect. 
 “Section 409A”: Section 409A of the Code and the regulations
thereunder. 

  
 A-2

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