Document:

EX-10.15

 Exhibit 10.15 

EXECUTIVE EMPLOYMENT AGREEMENT 

This Employment Agreement (the “Agreement”), made and entered into this 14th day of October 2019 (the “Effective Date”),
by and between Checkmate Pharmaceuticals, Inc., a Delaware corporation (“Company”), and Kleem Chaudhary, Ph.D. (“Executive”). 

WHEREAS, Company wishes to employ Executive as its Chief Business Officer. 

WHEREAS, Executive represents that Executive possesses the necessary skills to perform the duties of this position and that Executive
has no obligation to any other person or entity which would prevent, limit or interfere with Executive’s ability to do so; and 

WHEREAS, Executive and Company desire to enter into a formal Employment Agreement to assure the harmonious performance of the affairs
of Company. 
 NOW, THEREFORE, in consideration of the mutual promises, terms, provisions, and conditions contained herein, the
parties agree as follows: 
 1.    Roles and Duties. Subject to the terms and conditions of this
Agreement, Company shall employ Executive as its Chief Business Officer reporting to the CEO. Executive’s duties will include responsibility for the Company’s Business Development, Corporate Strategy and Planning, Investor Relations and
Corporate Communications functions; and other duties as assigned by the CEO. Executive accepts such employment upon the terms and conditions set forth herein and agrees to perform to the best of Executive’s ability the duties normally
associated with such position and as determined by Company in its sole discretion. During Executive’s employment. Executive shall devote all of Executive’s business time and energies to the business and affairs of Company, provided that
nothing contained in this Section 1 shall prevent or limit Executive’s right to manage Executive’s personal investments on Executive’s own personal time, including the right to make passive investments in the securities
of: (a) any entity which Executive does not control, directly or indirectly, and which does not compete with Company, or (b) any publicly held entity so long as Executive’s aggregate direct and indirect interest does not
exceed two percent (2%) of the issued and outstanding securities of any class of securities of such publicly held entity. 

2.    Term of Employment. 

(a)    Term. Subject to the terms hereof, Executive’s employment hereunder shall commence on
November 1, 2019 (the “Commencement Date”) and shall continue until terminated hereunder by either party (such term of employment referred to herein as the “Term”). 

(b)    Termination. Notwithstanding anything else contained in this Agreement, Executive’s employment
hereunder shall terminate upon the earliest to occur of the following: 
 (i)    Death. Immediately upon
Executive’s death: 
 (ii)    Termination by Company. 

 (A)    If because of Executive’s Disability (as
defined in Section 2(c)). upon written notice by Company to Executive that Executive’s employment is being terminated as a result of Executive’s Disability, which termination shall be effective on the date of such notice or such later
date as specified in writing by Company; 
 (B)    If for Cause (as defined in Section 2(d)), upon
written notice by Company to Executive that Executive’s employment is being terminated for Cause, which termination shall be effective on the date of such notice or such later date as specified in writing by Company; or 

(C)    If by Company for reasons other than Disability or Cause, upon written notice by Company to
Executive that Executive’s employment is being terminated, which termination shall be effective immediately after the date of such notice or such later date as specified in writing by Company. 

(iii)    Termination by Executive. 

(A)    If for Good Reason (as defined in Section 2(e)), upon written notice by Executive to
Company that Executive is terminating Executive’s employment for Good Reason and that sets forth the factual basis supporting the alleged Good Reason, which termination shall be effective thirty (30) days after the date of such
notice; provided that if Company has cured the circumstances giving rise to the Good Reason, then such termination shall not be effective; see Section 4 for Severance Payment provisions or 

(B)    If without Good Reason, written notice by Executive to Company that Executive is terminating
Executive’s employment, which termination shall be effective at least thirty’ (30) days after the date of such notice. 

Notwithstanding anything in this Section 2(b), Company may at any point terminate Executive’s employment for Cause prior to the
effective date of any other termination contemplated hereunder. 
 (c)    Definition of “Disability”.
For purposes of this Agreement, “Disability” shall mean Executive’s incapacity or inability to perform Executive’s duties and responsibilities as contemplated herein for one hundred twenty (120) days or more within
any one (1) year period (cumulative or consecutive), because Executive’s physical or mental health has become so impaired as to make it impossible or impractical for Executive to perform the duties and responsibilities contemplated
hereunder. Determination of Executive’s physical or mental health shall be determined by Company after consultation with a medical expert appointed by mutual agreement between Company and Executive who has examined Executive. Executive hereby
consents to such examination and consultation regarding Executive’s health and ability to perform as aforesaid. 

(d)    Definition of “Cause”. As used herein, “Cause” shall include: (i) Executive’s
willful engagement in illegal conduct or gross misconduct, which, in each case, is materially injurious to Company; (ii) Executive’s insubordination or substantial malfeasance or nonfeasance of duty, which, in each case, is
materially injurious to Company; (iii) Executive’s embezzlement, misappropriation or fraud; (iv) Executive’s unauthorized disclosure of confidential 

 
information; or (v) Executive’s breach of a material provision of any employment, non-disclosure, invention assignment, non-competition,
or similar agreement between Executive and Company; provided that (A) Company provides Executive with written notice that Company intends to terminate Executive’s employment hereunder for one of the circumstances set forth in
this Section 2(d) within thirty (30) days of such circumstance occurring, (B) if such circumstance is capable of being cured, Executive has failed to cure such circumstance within a period of thirty
(30) days from the date of such written notice, and (C) Company terminates Executive’s employment within sixty five (65) days from the date that Cause first occurs. For purposes of clarification, the
above-listed conditions shall apply separately to each occurrence of Cause, and failure to adhere to such conditions in the event of Cause shall not disqualify Company from asserting Cause for any subsequent occurrence of Cause. 

(e)    Definition of “Good Reason”. As used herein, “Good Reason” shall mean:
(i) relocation of Executive’s principal business location to a location more than fifty (50) miles from Executive’s then-current business location; (ii) a material diminution in Executive’s duties,
authority or responsibilities; or (iii) a material reduction in Executive’s Base Salary; provided that (A) Executive provides Company with written notice that Executive intends to terminate Executive’s
employment hereunder for one of the circumstances set forth in this Section 2(e) within thirty (30) days of such circumstance occurring, (B) if such circumstance is capable of being cured, Company has failed to
cure such circumstance within a period of thirty (30) days from the date of such written notice, and (C) Executive terminates Executive’s employment within sixty five (65) days from the date that Good Reason
first occurs. For purposes of clarification, the above-listed conditions shall apply separately to each occurrence of Good Reason and failure to adhere to such conditions in the event of Good Reason shall not disqualify Executive from asserting Good
Reason for any subsequent occurrence of Good Reason. For purposes of this Agreement, “Good Reason” shall be interpreted in a manner, and limited to the extent necessary, so that it shall not cause adverse tax consequences for either party
with respect to Section 409A (“Section 409A”) of the Internal Revenue Code of 1986, as amended (the “Code”), and any successor statute, regulation and guidance thereto. 

3.    Compensation. 

(a)    Base Salary. Company shall pay Executive a base salary (the “Base Salary”) at the annual rate of
three hundred and fifty thousand dollars ($350,000), as of the Commencement Date. The Base Salary’ shall be payable in substantially equal periodic installments in accordance with Company’s payroll practices as in effect from time to time.
Company shall deduct from each such installment all amounts required to be deducted or withheld under applicable law or under any employee benefit plan in which Executive participates. The Company shall review the Base Salary on an annual basis and
may increase, but not decrease, the Base Salary. 
 (b)    Annual Performance Bonus. Executive shall be eligible
to receive an annual cash bonus (the “Annual Performance Bonus”), with the target amount of such Annual Performance Bonus equal to Thirty Percent (30%) of Executive’s Base Salary in the year to which the Annual Performance Bonus
relates; provided that the actual amount of the Annual Performance Bonus may be greater or less than such target amount. The amount of the Annual Performance Bonus shall be determined by the Board or an appropriate committee thereof in its sole
discretion, 

 
and shall be paid to Executive no later than March 15th of the calendar year immediately following the calendar year in which it was earned.
Executive must be employed by Company on the last day of the fiscal year on which the Annual Performance Bonus is based in order to be eligible for such Annual Performance Bonus. Company shall deduct from the Annual Performance Bonus all amounts
required to be deducted or withheld under applicable law or under any employee benefit plan in which Executive participates. For the current calendar year, Executive shall be eligible for a prorated Annual Performance Bonus subject to the terms and
conditions described above. 
 (c)    Paid Time Off. Executive may take up to twenty (20) days of paid time
off (“PTO”) per year, to be scheduled to minimize disruption to Company’s operations, pursuant to the terms and conditions of Company policy and practices as applied to Company senior executives. 

(d)    Fringe Benefits. Executive shall be entitled to participate in all benefit/welfare plans and fringe benefits
provided to Company senior executives. Executive understands that, except when prohibited by applicable law, Company’s benefit plans and fringe benefits may be amended by Company from time to time in its sole discretion. 

(e)    Equity Incentive Awards. Executive will eligible to participate in the Company’s equity incentive
program and, subject to approval by the Company’s Board of Directors, to be obtained no later than the Commencement Date, receive a stock option grant equal to 1.1% of the Company’s fully diluted stock vesting over four years, with the
first twenty-five percent (25%) vesting on the twelve (12) month anniversary of your Commencement Date, and the remaining vesting in equal monthly installments over the following thirty-six
(36) months. In the case of a Sale Event, as defined in the Company’s 2015 Stock Option and Grant Plan (“the Plan”), this option shall be treated as provided in Section 3(c) of the Plan and all of the shares
shall vest immediately upon the Completion of a Sale Event (as defined in the Plan). 
 (f)    Sign-On Bonus. Company shall pay Executive a sign-on bonus payment of one hundred thousand dollars ($100,000) within one month after the Commencement Date and an
additional payment of sixty-five thousand dollars ($65,000) within one month after either (i) the twelve (12) month anniversary of the Commencement Date provided that Executive is employed by the Company on the twelve
(12) month anniversary of the Commencement Date or (ii) a change of control of the Company provided that Executive is employed by the Company on the date of the change of control of the Company. 

(g)    Reimbursement of Expenses. Company shall reimburse Executive for all ordinary and reasonable out-of-pocket business expenses incurred by Executive in furtherance of Company’s business in accordance with Company’s policies with respect thereto as in effect
from time to time. Executive must submit any request for reimbursement no later than ninety (90) days following the date that such business expense is incurred. All reimbursements provided under this Agreement shall be made or provided in
accordance with the requirements of Section 409A including, where applicable, the requirement that (i) any reimbursement is for expenses incurred during Executive’s lifetime (or during a shorter period of time specified
in this Agreement); (ii) the amount of expenses eligible for reimbursement during a calendar year may not affect the expenses eligible for reimbursement in any other calendar year; (iii) the reimbursement of an eligible
expense shall be made no later than the last day of the calendar year following the year in which the expense is incurred; and (iv) the right to reimbursement or in kind benefits is not subject to liquidation or exchange for another
benefit. 

 (h)    Indemnification. Executive shall be entitled to
indemnification with respect to Executive’s sendees provided hereunder pursuant to Delaware law, the terms and conditions of Company’s certificate of incorporation and/or by-laws, Company’s
directors and officers (“D&O”) liability insurance policy, and Company’s standard indemnification agreement for directors and officers as executed by Company and Executive. 

(i)    Initial Public Offering. If the Company completes an initial public offering, Executive’s cash
compensation (base salary’ plus target bonus) shall be set at least the median for the Chief Business Officer at comparable public companies as determined by the Company’s Board of Directors. 

4.    Payments Upon Termination. 

(a)    Definition of Accrued Obligations. For purposes of this Agreement, “Accrued Obligations” means the
portion of Executive’s Base Salary that has accrued prior to any termination of Executive’s employment with Company and has not yet been paid, and the amount of any expenses properly incurred by Executive on behalf of Company prior to any
such termination and not yet reimbursed. Executive’s entitlement to any other compensation or benefit under any plan of Company shall be governed by and determined in accordance with the terms of such plans, except as otherwise specified in
this Agreement. 
 (b)    Termination by Company for Cause, by Executive Without Good Reason, or as a Result of
Executive’s Disability or Death. If Executive’s employment hereunder is terminated by Company for Cause, by Executive without Good Reason, or as a result of Executive’s Disability or death, then Company shall pay the Accrued
Obligations to Executive promptly following the effective date of such termination. 
 (c)    Termination by Company
Without Cause or by Executive For Good Reason. In the event that Executive’s employment is terminated by action of Company other than for Cause, or Executive terminates Executive’s employment for Good Reason, then, in addition to the
Accrued Obligations, Executive shall receive the following, subject to the terms and conditions of Section 4(d): 

(i)    Severance Payments. Payment in an amount equal to Executive’s then-current Base Salary for a nine
(9) month period plus any Annual Performance Bonus accrued prior to any termination of Executive’s employment with Company and has not yet been paid (prorated based on the date of termination) less customary and required taxes and
employment-related deductions, paid in one lump sum amount on the first payroll date following the date on which the separation agreement under Section 4(d) becomes effective and non-revocable;
provided that such payment shall be made within seventy (70) days following the effective date of termination from employment, and further provided that if the 70th day falls in the calendar year following the year during
which the termination or separation from service occurred, then the payments will commence in such subsequent calendar year, and further provided that if such payments commence in such subsequent year, the first such payment shall be a lump
sum in an 

 
amount equal to the payments that would have come due since Employee’s separation from service. For the avoidance of doubt, the severance payments in this Section 4(c)(i) apply in the
event of a change of control of the Company. 
 (ii)    Benefits Payments. Upon completion of appropriate forms
and subject to applicable terms and conditions under the Consolidated Omnibus Budget Reconciliation Act of 1985, as amended (“COBRA”), Company shall continue to provide Executive medical insurance coverage at no cost to Executive to the
same extent that such insurance continues to be provided to similarly situated executives at the time of Executive’s termination, until the earlier to occur of twelve (12) months following Executive’s termination date or the date
Executive begins employment with another employer. Executive shall bear responsibility for applying for COBRA continuation coverage. 

(d)    Execution of Separation Agreement. Company shall not be obligated to pay Executive severance payments or
benefits described in this Section 4 unless Executive has executed (without revocation) a timely separation agreement in a form acceptable to Company, which shall include a release of claims and standard terms regarding non-disparagement,
confidentiality, cooperation and the like, which shall be provided to Executive within ten (10) days following separation from service, and signed by Executive and returned to Company no later than sixty (60) days following
Executive’s separation from service (the “Review Period”). 
 (e)    COBRA. 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 “Act”) or Section 105(h) of the Code, the COBRA premiums paid by 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 Act 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 Sections 4(b) or 4(c) above. 

5.    Prohibited Competition And Solicitation. In light of the competitive and proprietary aspects of
the business of Company, and as a condition of employment hereunder, Executive agrees to execute and abide by Company’s Confidentiality, Assignment of Inventions and Non-Competition Agreement. 

6.    Property and Records. Upon the termination of Executive’s employment hereunder, or if
Company otherwise requests, Executive shall: (a) return to Company all tangible business information and copies thereof (regardless how such Confidential Information or copies are maintained), and (b) deliver to Company any
property of Company which may be in Executive’s possession, including, but not limited to, cell phones, smart phones, laptops, products, materials, memoranda, notes, records, reports or other documents or photocopies of the same. 

 7.    Code Sections 409A and 280G. 

(a)    In the event that the payments or benefits set forth in Section 4 of this Agreement constitute
“non-qualified deferred compensation” subject to Section 409A, then the following conditions apply to such payments or benefits: 

(i)    Any termination of Executive’s employment triggering payment of benefits under Section 4 must constitute
a “separation from service” under Section 409A(a)(2)(A)(i) of the Code and Treas. Reg. §1.409A-l(h) before distribution of such benefits can commence. To the extent that the termination of Executive’s employment does
not constitute a separation of service under Section 409A(a)(2)(A)(i) of the Code and Treas. Reg. § 1.409A-1 (h) (as the result of further services that are reasonably anticipated to be provided by Executive to Company
at the time Executive’s employment terminates), any such payments under Section 4 that constitute deferred compensation under Section 409A shall be delayed until after the date of a subsequent event constituting a
separation of service under Section 409A(a)(2)(A)(i) of the Code and Treas. Reg. §1.409A-l(h). For purposes of clarification, this Section 7(a) shall not cause any forfeiture of benefits on Executive’s part, but
shall only act as a delay until such time as a “separation from service” occurs. 
 (ii)    Notwithstanding
any other provision with respect to the timing of payments under Section 4 if, at the time of Executive’s termination, Executive is deemed to be a “specified employee” of Company (within the meaning of
Section 409A(a)(2)(B)(i) of the Code), then limited only to the extent necessary to comply with the requirements of Section 409A, any payments to which Executive may become entitled under Section 4 which are
subject to Section 409A (and not otherwise exempt from its application) shall be withheld until the first (1st) business day of the seventh (7th) month following the termination of Executive’s employment, at which time Executive shall be paid an aggregate amount equal to the accumulated, but unpaid, payments otherwise due to Executive
under the terms of Section 4. 
 (b)    It is intended that each installment of the payments and benefits
provided under Section 4 of this Agreement shall be treated as a separate “payment” for purposes of Section 409A. Neither Company nor Executive shall have the right to accelerate or defer the delivery of any such payments
or benefits except to the extent specifically permitted or required by Section 409A. 

(c)    Notwithstanding any other provision of this Agreement to the contrary, this Agreement shall be interpreted and at
all times administered in a manner that avoids the inclusion of compensation in income under Section 409A, or the payment of increased taxes, excise taxes or other penalties under Section 409A. The parties intend this Agreement to
be in compliance with Section 409A. Executive acknowledges and agrees that Company does not guarantee the tax treatment or tax consequences associated with any payment or benefit arising under this Agreement, including but not limited to
consequences related to Section 409A. 

 (d)    If any payment or benefit Executive would receive under this
Agreement, when combined with any other payment or benefit Executive receives pursuant to a change of control (for purposes of this section, a “Payment”) would: (i) constitute a “parachute payment” within the meaning of
Section 280G the Code; and (ii) but for this sentence, be subject to the excise tax imposed by Section 4999 of the Code (the “Excise Tax”), then such Payment shall be either: (A) the full
amount of such Payment; or (B) such lesser amount as would result in no portion of the Payment being subject to the Excise Tax, whichever of the foregoing amounts, taking into account the applicable federal, state and local employments
taxes, income taxes and the Excise Tax, results in Executive’s receipt, on an after-tax basis, of the greater amount of the Payment notwithstanding that all or some portion of the Payment may be subject to the Excise Tax. With respect to
subsection (B), if there is more than one method of reducing the payment as would result in no portion of the Payment being subject to the Excise Tax, then Executive shall determine which method shall be followed, provided that if Executive
fails to make such determination within thirty (30) days after Company has sent Executive written notice of the need for such reduction, Company may determine the amount of such reduction in its sole discretion. 

8.    General. 

(a)    Notices. Except as otherwise specifically provided herein, any notice required or permitted by this Agreement
shall be in writing and shall be delivered as follows with notice deemed given as indicated: (i) by personal delivery when delivered personally; (ii) by overnight courier upon written verification of receipt; (iii) by
telecopy or facsimile transmission upon acknowledgment of receipt of electronic transmission; or (iv) by certified or registered mail, return receipt requested, upon verification of receipt. 

 

	 	•	 	 Notices to Executive shall be sent to: 

The last known address in Company’s records or such other address as Executive may specify in writing. 

 

	 	•	 	 Notices to Company shall be sent to: 

Checkmate Pharmaceuticals, Inc. 

245 Main St., 4th Floor 

Cambridge, MA 02142 
 Attn:
President and CEO 
 or to such other Company representative as Company may specify in writing, with a copy to: 

Goodwin Procter LLP 
 100 Northern
Avenue 
 Boston, MA 02210 

(b)    Modifications: Amendments: Waivers: Consents. The terms of this Agreement may be modified or amended only by
written agreement executed by the parties hereto. The terms of this Agreement may be waived, or consent for the departure therefrom granted, only 

 
by written document executed by the party entitled to the benefits of such terms or provisions. No such waiver or consent shall be deemed to be or shall constitute a waiver or consent with
respect to any other terms of this Agreement, whether or not similar. Each such waiver or consent shall be effective only in the specific instance and for the purpose for which it was given, and shall not constitute a continuing waiver or consent.

 (c)    Assignment. Company may assign its rights and obligations hereunder to any person or entity that
succeeds to all or substantially all of Company’s business or that aspect of Company’s business in which Executive is principally involved. Executive may not assign Executive’s rights and obligations under this Agreement without the
prior written consent of Company. 
 (d)    Governing Law; Jurisdiction: Venue. This Agreement shall be
governed by and construed in accordance with the substantive laws of the Commonwealth of Massachusetts, without giving effect to any choice or conflict of law provision or rule. Any legal action permitted by this Agreement to enforce an award or for
a claimed breach shall be governed by the laws of the Commonwealth of Massachusetts and shall be commenced and maintained solely in any state or federal court located in the Commonwealth of Massachusetts, and both parties hereby submit to the
jurisdiction and venue of any such court. 
 (e)    Headings and Captions. The headings and captions of the
various subdivisions of this Agreement are for convenience of reference only and shall in no way modify or affect the meaning or construction of any of the terms or provisions hereof. 

(f)    Entire Agreement. This Agreement, together with the other agreements specifically referenced herein,
embodies the entire agreement and understanding between the parties hereto with respect to the subject matter hereof and supersedes all prior oral or written agreements and understandings relating to the subject matter hereof. No statement,
representation, warranty, covenant or agreement of any kind not expressly set forth in this Agreement shall affect, or be used to interpret, change or restrict, the express terms and provisions of this Agreement. 

This Agreement may be executed in two or more counterparts, and by different parties hereto on separate counterparts, each of which shall be
deemed an original, but all of which together shall constitute one and the same instrument. For all purposes a signature by fax shall be treated as an original. 

IN WITNESS WHEREOF, the parties hereto have executed this Agreement as of the date first written above. 

 

							
	KLEEM CHAUDHARY	 		 	CHECKMATE PHARMACEUTICALS, INC.
				
	 /s/ Kleem Chaudhary
	 		 	By:	 	 /s/ Barry Labinger

	Signature	 		 		 	 Name: Barry Labinger
 Title: President and
CEO

 AMENDMENT NO. 1 

TO 
 EMPLOYMENT AGREEMENT

 THIS AMENDMENT NO. 1 (this “Amendment”) to that certain Executive Employment Agreement, dated as of October 14, 2019 (the
“Employment Agreement”), by and between Checkmate Pharmaceuticals, Inc., a corporation, and Kleem Chaudhary (the “Executive”) is made and entered into by and between the Executive and the Company, effective upon the
completion of the Company’s initial public offering (the “Effective Date”). Capitalized terms used and not otherwise defined herein shall have the meanings ascribed to such terms in the Employment Agreement. 

WHEREAS, the Executive and the Company are party to the Employment Agreement; 

WHEREAS, the Company desires to continue to employ the Executive and the Executive desires to continue to be employed by the Company; and 

WHEREAS, the Executive and the Company desire to amend the Employment Agreement effective as of the Effective Date as set forth herein. 

NOW, THEREFORE, in consideration of the foregoing and for other good and valuable consideration, the receipt and sufficiency of which are
hereby acknowledged, the Executive and the Company hereby agree to amend the Employment Agreement effective as of the Effective Date as follows: 

1. The following shall be inserted as a new Section 2(f): 

(f) Definition of “Change in Control”. For purposes of this Agreement, “Change in Control”
shall mean “Sale Event” as such term is defined in the Checkmate Pharmaceuticals, Inc. 2020 Stock Option and Incentive Plan, as the same may be amended from time to time. 

2. The following shall be inserted as a new Section 2(g): 

(g) Definition of “Change in Control Period”. For purposes of this Agreement, “Change in Control Period” means the
twelve (12) month period beginning on the date the Change in Control occurs. 
 3. The following shall be inserted as a new
Section 2(h): 
 (h) Definition of “IPO”. For purposes of this Agreement, “IPO” means the first offering by
the Company of its equity securities to the public pursuant to an effective registration statement filed under the Securities Act of 1933, as amended, or under any similar law then in effect. 

4. Section 2(e) of the Employment Agreement is deleted and replaced with the following: 

 Definition of “Good Reason”. As used herein, “Good Reason” shall
mean the following actions by Company, in each case without Executive’s consent: (i) relocation of Executive’s principal business location to a location more than fifty (50) miles from Executive’s then-current business
location; (ii) a material diminution in Executive’s duties, authority or responsibilities; or (iii) a material reduction in Executive’s Base Salary unrelated to a Company-wide reduction in officer compensation; provided
that (A) Executive provides Company with written notice that Executive intends to terminate Executive’s employment hereunder for one of the circumstances set forth in this Section 2(e) within thirty (30) days of such circumstance
occurring, (B) if such circumstance is capable of being cured, Company has failed to cure such circumstance within a period of thirty (30) days from the date of such written notice, and (C) Executive terminates Executive’s
employment within sixty five (65) days from the date that Good Reason first occurs. For purposes of clarification, the above-listed conditions shall apply separately to each occurrence of Good Reason and failure to adhere to such conditions in
the event of Good Reason shall not disqualify Executive from asserting Good Reason for any subsequent occurrence of Good Reason. For purposes of this Agreement, “Good Reason” shall be interpreted in a manner, and limited to the extent
necessary, so that it shall not cause adverse tax consequences for either party with respect to Section 409A (“Section 409A”) of the Internal Revenue Code of 1986, as amended (the “Code”), and any successor statute,
regulation and guidance thereto. Notwithstanding the foregoing, any of the actions described in subclause (ii) herein that are taken in connection with a transaction in which the owners of the Company’s outstanding voting power immediately
prior to such transaction do not own at least a majority of the outstanding voting power of the Company or any successor entity immediately upon completion of the transaction other than as a result of the acquisition of securities directly from the
Company shall not be deemed to constitute an occurrence of Good Reason. 
 5. The first sentence of Section 3(a) of the Employment
Agreement is deleted and replaced with the following: 
 Company shall pay Executive a base salary (the “Base Salary”) at the
annual rate of three hundred seventy thousand dollars ($370,000). 
 6. The first sentence of Section 3(b) of the Employment Agreement
is deleted and replaced with the following: 
 Executive shall be eligible to receive an annual cash bonus (the “Annual Performance
Bonus”), with the target amount of such Annual Performance Bonus equal to Forty Percent (40%) of Executive’s Base Salary in the year to which the Annual Performance Bonus relates (the “Target Bonus Amount”), provided that
the actual amount of the Annual Performance Bonus may be greater or less than such Target Bonus Amount. 
 7. Section 4(c) of the Employment
Agreement is deleted in its entirety and replaced with the following: 

  
 - 2 - 

 (c) Severance Pay and Benefits Upon Termination by the Company without Cause or by the
Executive for Good Reason Outside the Change in Control Period. If the Executive’s employment is terminated by the Company without Cause or the Executive terminates employment for Good Reason, each outside of the Change in Control Period,
then, in addition to the Accrued Obligations, and 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 obligations under the Company’s Confidentiality, Assignment of Inventions and Non-Competition Agreement of the Agreement, and any
other provisions of this Agreement intended to survive its termination (“Continuing Obligations”), and shall provide that if the Executive breaches any of the Continuing Obligations, all payments or provisions of the Severance Pay and
Benefits shall immediately cease (and may be subject to recoupment) without affecting the other provisions thereof (the “Separation Agreement and Release”), and (ii) the Separation Agreement and Release becoming effective
irrevocable, all within 60 days after the date of termination (or such shorter period as set forth in the Separation Agreement and Release), the Company will pay or provide (as applicable) the following (collectively, the “Severance Pay and
Benefits”): 
 (i) an amount equal to 9 months of the Executive’s Base Salary (the “Severance Amount”);
and 
 (ii) if the Executive was participating in the Company’s group health, dental and/or vision plans immediately
prior to the date of termination and properly elects to continue health coverage under the Consolidated Omnibus Budget Reconciliation Act of 1985, as amended (“COBRA”), then, subject to the Executive’s copayment of the premium amounts
at the applicable active employees’ rate, the Company shall pay to the group health plan provider, the COBRA provider or the Executive a monthly payment equal to the monthly employer contribution that the Company would have made to provide
health insurance to the Executive if the Executive had remained employed by the Company until the earliest of the following: (i) the last day of the nine-month period following the date of termination; (ii) the Executive’s
eligibility for group medical plan benefits under any other employer’s group medical plan or otherwise through other employment; or (iii) the cessation of the Executive’s continuation coverage rights under COBRA.
Notwithstanding the foregoing, if the Company determines at any time that its payments pursuant to this paragraph may be taxable income to the Executive or that it cannot pay such amounts to the group health plan provider or the COBRA provider (if
applicable) without potentially violating applicable law (including, without limitation, Section 2716 of the Public Health Service Act), then the Company may convert such payments to payroll payments directly to the Executive for the
time period specified above; and such payments shall be subject to tax-related deductions and withholdings and shall be paid on the Company’s regular payroll dates. Any other premiums or costs of COBRA continuation coverage not provided above
(including, without limitation, for any COBRA coverage after the time period set forth above) shall be at the sole expense of the Executive. 

  
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 The amounts payable under this Section 4(c), to the extent taxable, shall be paid out
in substantially equal installments in accordance with the Company’s payroll practice over 9 months 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, to the extent it qualifies as “non-qualified deferred compensation” within the meaning of
Section 409A of the Code, 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). 
 8. The following shall be inserted as a new Section 4(d): 

(d) Severance Pay and Benefits 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 4(d) shall apply in lieu of, and expressly supersede, the provisions of Section 4(c) if the date of termination occurs during the Change in Control Period. These provisions shall
terminate and be of no further force or effect after a Change in Control Period. If the Executive’s employment is terminated by the Company without Cause or the Executive terminates employment for Good Reason and, in each case, the date of
termination occurs during the Change in Control Period, then, in addition to the Accrued Obligations, and subject to (i) the Executive signing a Separation Agreement and Release meeting all of the requirements specified in
Section 4(c) of this Agreement, including a reaffirmation that if the Executive breaches any of the Continuing Obligations, all payments or provisions of the Change in Control Pay and Benefits shall immediately cease and may be subject
to recoupment, and (ii) the Separation Agreement and Release becoming effective irrevocable, all within 60 days after the date of termination (or such shorter period as set forth in the Separation Agreement and Release), the Company will
pay or provide (as applicable) the following (collectively, the “Change in Control Pay and Benefits”): 
 (i) the
Company shall pay the Executive a lump sum in cash in an amount equal to the (A) Executive’s then current Base Salary, plus (B) the Target Bonus Amount; 

(ii) notwithstanding anything to the contrary in any applicable option agreement or other stock-based award agreement, all
time-based stock options and other stock-based awards subject to time-based vesting held by the Executive (the “Time-Based Equity Awards”) and granted after the Company’s IPO shall immediately accelerate and become fully exercisable
or nonforfeitable as of the later of (A) the date of termination or (B) the effective date of the Separation Agreement and Release (the “Accelerated Vesting Date”); provided that any

  
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termination or forfeiture of the unvested portion of such Time-Based Equity Awards that would otherwise occur on the date of termination in the absence of this Agreement will be delayed until the
effective date of the Separation Agreement and Release and will only occur if the vesting pursuant to this subsection does not occur due to the absence of the Separation Agreement and Release becoming fully effective within the time period set forth
therein. Notwithstanding the foregoing, no additional vesting of the Time-Based Equity Awards shall occur during the period between the Executive’s date of termination and the Accelerated Vesting Date; and 

(iii) if the Executive was participating in the Company’s group health, dental and/or vision plans immediately prior to
the date of termination and properly elects to continue health coverage under the Consolidated Omnibus Budget Reconciliation Act of 1985, as amended (“COBRA”), then, the Company shall continue to provide Executive medical insurance
coverage at no cost to Executive to the same extent that such insurance continues to be provided to similarly situated executives at the time of Executive’s termination until the earliest of the following: (i) the first anniversary
of the date of termination; (ii) the Executive’s eligibility for group medical plan benefits under any other employer’s group medical plan or otherwise through other employment; or (iii) the cessation of the
Executive’s continuation coverage rights under COBRA. Notwithstanding the foregoing, if the Company determines at any time that its payments pursuant to this paragraph may be taxable income to the Executive or that it cannot pay such amounts to
the group health plan provider or the COBRA provider (if applicable) without potentially violating applicable law (including, without limitation, Section 2716 of the Public Health Service Act), then the Company may convert such payments
to payroll payments directly to the Executive for the time period specified above; and such payments shall be subject to tax-related deductions and withholdings and shall be paid on the Company’s regular payroll dates. 

The amounts payable under this Section 4(d), to the extent taxable, shall be paid or commence to be paid within 60 days after the date of
termination. 
 9. All Agreement references to section numbers and defined terms are amended to reflect the above modifications. 

10. Except to the extent expressly modified or amended by this Amendment, all terms and provisions of the Employment Agreement shall
continue in full force and effect and shall remain enforceable and binding in accordance with their respective terms. 
 11. Any required
notices, meetings or consents that are necessary to make an amendment to the Employment Agreement are hereby waived or satisfied. 
 12.
This Amendment may be executed in counterparts, each of which shall be deemed an original, but all of which together shall be deemed to be one and the same agreement. A signed copy of this Amendment delivered by facsimile, e-mail or other means of electronic transmission shall be deemed to have the same legal effect as delivery of an original signed copy of this Amendment. 

  
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 IN WITNESS WHEREOF, the undersigned have executed this Amendment effective as of the date
first set forth above. 
  

			
	COMPANY:
	
	 CHECKMATE PHARMACEUTICALS, INC.,
 a
Delaware Corporation

		
	By:	 	 /s/ Barry Labinger

	Name:	 	Barry Labinger
	Title:	 	President and Chief Executive Officer
	
	EXECUTIVE:
		
	By:	 	 /s/ Kleem Chaudhary

	Name:	 	Kleem Chaudhary

 Signature Page to Amendment No. 1 to Chaudhary Executive Employment AgreementEX-10.17

 Exhibit 10.17 

EXECUTIVE EMPLOYMENT AGREEMENT 

This Employment Agreement (the “Agreement”), made and entered into this 8th day of April, 2020 (the “Effective Date”), by
and between Checkmate Pharmaceuticals, Inc., a Delaware corporation (“Company”), and Arthur M. Krieg (“Executive”). 

WHEREAS, Company wishes to employ Executive as its Chief Scientific Officer (“CSO”) 

WHEREAS, Executive represents that Executive possesses the necessary skills to perform the duties of this position and that Executive
has no obligation to any other person or entity which would prevent, limit or interfere with Executive’s ability to do so; and 

WHEREAS, Executive and Company desire to enter into a formal Employment Agreement to assure the harmonious performance of the affairs
of Company. 
 NOW, THEREFORE, in consideration of the mutual promises, terms, provisions, and conditions contained herein, the
parties agree as follows: 
 1.    Roles and Duties. Subject to the terms and conditions of this
Agreement, Company shall employ Executive as its Chief Scientific Officer (“CSO”) reporting to the CEO. Executive accepts such employment upon the terms and conditions set forth herein, and agrees to perform to the best of Executive’s
ability the duties normally associated with such position and as determined by Company in its sole discretion. During Executive’s employment, Executive shall devote all of Executive’s business time and energies to the business and affairs
of Company, provided that nothing contained in this Section 1 shall prevent or limit Executive’s right to manage Executive’s personal investments on Executive’s own personal time, including the right to make passive investments
in the securities of: (a) any entity which Executive does not control, directly or indirectly, and which does not compete with Company, or (b) any publicly held entity so long as Executive’s aggregate direct and indirect
interest does not exceed two percent (2%) of the issued and outstanding securities of any class of securities of such publicly held entity. Executive may serve on one corporate Board of Directors (other than Checkmate’s Board of Directors)
subject to prior approval by the CEO , for companies which are not developing a TLR9 agonist, and may be involved in civic and charitable activities so long as such activities do not interfere with Executive’s duties for Company. Executive
agrees that his service on SAB Board will not exceed one day per month. 
 2.    Term of
Employment. 
 (a)    Term. Subject to the terms hereof, Executive’s employment hereunder shall
commence on December 17, 2018 (the “Commencement Date”) and shall continue until terminated hereunder by either party (such term of employment referred to herein as the “Term”). 

(b)    Termination. Notwithstanding anything else contained in this Agreement, Executive’s employment
hereunder shall terminate upon the earliest to occur of the following: 
 (i)    Death. Immediately upon
Executive’s death; 

 (ii)    Termination by Company. 

(A)    If because of Executive’s Disability (as defined in Section 2(c)), upon written notice by
Company to Executive that Executive’s employment is being terminated as a result of Executive’s Disability, which termination shall be effective on the date of such notice or such later date as specified in writing by Company; 

(B)    If for Cause (as defined in Section 2(d)), upon written notice by Company to Executive that
Executive’s employment is being terminated for Cause, which termination shall be effective on the date of such notice or such later date as specified in writing by Company; or 

(C)    If by Company for reasons other than Disability or Cause, upon written notice by Company to
Executive that Executive’s employment is being terminated, which termination shall be effective immediately after the date of such notice or such later date as specified in writing by Company. 

(iii)    Termination by Executive. 

(A)    If for Good Reason (as defined in Section 2(e)), upon written notice by Executive to Company
that Executive is terminating Executive’s employment for Good Reason and that sets forth the factual basis supporting the alleged Good Reason, which termination shall be effective thirty (30) days after the date of such notice;
provided that if Company has cured the circumstances giving rise to the Good Reason, then such termination shall not be effective; [see Section 4 for Severance Payment provisions] or 

(B)    If without Good Reason, written notice by Executive to Company that Executive is terminating
Executive’s employment, which termination shall be effective at least thirty (30) days after the date of such notice. 

Notwithstanding anything in this Section 2(b), Company may at any point terminate Executive’s employment for Cause prior to the
effective date of any other termination contemplated hereunder. 
 (c)    Definition of “Disability”.
For purposes of this Agreement, “Disability” shall mean Executive’s incapacity or inability to perform Executive’s duties and responsibilities as contemplated herein for one hundred twenty (120) days or more within any one
(1) year period (cumulative or consecutive), because Executive’s physical or mental health has become so impaired as to make it impossible or impractical for Executive to perform the duties and responsibilities contemplated
hereunder. Determination of Executive’s physical or mental health shall be determined by Company after consultation with a medical expert appointed by mutual agreement between Company and Executive who has examined Executive. Executive hereby
consents to such examination and consultation regarding Executive’s health and ability to perform as aforesaid. 

(d)    (d) Definition of “Cause”. As used herein, “Cause” shall include:
(i) Executive’s willful engagement in illegal conduct or gross misconduct, which, in each case, is materially injurious to Company; (ii) Executive’s insubordination or substantial malfeasance or

  
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nonfeasance of duty, which, in each case, is materially injurious to Company; (iii) Executive’s embezzlement, misappropriation or fraud; (iv) Executive’s unauthorized
disclosure of confidential information; or (v) Executive’s breach of a material provision of any employment, non-disclosure, invention assignment, non-competition, or similar agreement between Executive and Company; provided
that (A) Company provides Executive with written notice that Company intends to terminate Executive’s employment hereunder for one of the circumstances set forth in this Section 2(d) within thirty (30) days
of such circumstance occurring, (B) if such circumstance is capable of being cured, Executive has failed to cure such circumstance within a period of thirty (30) days from the date of such written notice, and
(C) Company terminates Executive’s employment within sixty five (65) days from the date that Cause first occurs. For purposes of clarification, the above-listed conditions shall apply separately to each occurrence of
Cause, and failure to adhere to such conditions in the event of Cause shall not disqualify Company from asserting Cause for any subsequent occurrence of Cause. 

(e)    Definition of “Good Reason”. As used herein, “Good Reason” shall mean:
(i) relocation of Executive’s principal business location to a location more than fifty (50) miles from Executive’s then-current business location; (ii) a material diminution in Executive’s duties,
authority or responsibilities; or (iii) a material reduction in Executive’s Base Salary; provided that (A) Executive provides Company with written notice that Executive intends to terminate Executive’s employment
hereunder for one of the circumstances set forth in this Section 2(e) within thirty (30) days of such circumstance occurring, (B) if such circumstance is capable of being cured, Company has failed to cure such
circumstance within a period of thirty (30) days from the date of such written notice, and (C) Executive terminates Executive’s employment within sixty five (65) days from the date that Good Reason first
occurs. For purposes of clarification, the above-listed conditions shall apply separately to each occurrence of Good Reason and failure to adhere to such conditions in the event of Good Reason shall not disqualify Executive from asserting Good
Reason for any subsequent occurrence of Good Reason. For purposes of this Agreement, “Good Reason” shall be interpreted in a manner, and limited to the extent necessary, so that it shall not cause adverse tax consequences for either party
with respect to Section 409A (“Section 409A”) of the Internal Revenue Code of 1986, as amended (the “Code”), and any successor statute, regulation and guidance thereto. 

3.    Compensation. 

(a)    Base Salary. Company shall pay Executive a base salary (the “Base Salary”) at the annual rate of
three hundred ninety-two thousand and five hundred fifty-three dollars ($392,553), as of the Commencement Date). The Base Salary shall be payable in substantially equal periodic installments in accordance with
Company’s payroll practices as in effect from time to time. Company shall deduct from each such installment all amounts required to be deducted or withheld under applicable law or under any employee benefit plan in which Executive participates.
The Company shall review the Base Salary on an annual basis and may increase, but not decrease, the Base Salary. 

(b)    Annual Performance Bonus. Executive shall be eligible to receive an annual cash bonus (the “Annual
Performance Bonus”), with the target amount of such Annual Performance Bonus equal to Thirty Percent (30%) of Executive’s Base Salary in the year to which the Annual Performance Bonus relates, provided that the actual amount of the
Annual Performance 

  
 - 3 - 

 
Bonus may be greater or less than such target amount. The amount of the Annual Performance Bonus shall be determined by the Board or an appropriate committee thereof in its sole discretion, and
shall be paid to Executive no later than March 15th of the calendar year immediately following the calendar year in which it was earned. Executive must be employed by Company on the last day of
the fiscal year on which the Annual Performance Bonus is based in order to be eligible for such Annual Performance Bonus. Company shall deduct from the Annual Performance Bonus all amounts required to be deducted or withheld under applicable law or
under any employee benefit plan in which Executive participates. For the current calendar year, Executive shall be eligible for a prorated Annual Performance Bonus subject to the terms and conditions described above. 

(c)    Paid Time Off. Executive may take up to twenty (20) days of paid time off (“PTO”) per year,
to be scheduled to minimize disruption to Company’s operations, pursuant to the terms and conditions of Company policy and practices as applied to Company senior executives. 

(d)    Fringe Benefits. Executive shall be entitled to participate in all benefit/welfare plans and fringe benefits
provided to Company senior executives. Executive understands that, except when prohibited by applicable law, Company’s benefit plans and fringe benefits may be amended by Company from time to time in its sole discretion. 

(e)    Equity Incentive Awards. Executive will eligible to participate in the Company’s equity incentive
program and, provided that Executive continues to serve as the Company’s CSO, once the Company has completed an Initial Public Offering, will receive a stock option grant consistent with the Company’s policies and grants for other C-level employees for the Company’s common stock vesting over four years, assuming continued employment for service, with the first twenty-five percent (25%) vesting ion the twelve (12) month anniversary
of your Start Date, and the remaining vesting in equal monthly installments over the following thirty-six (36) months. In the case of a Sale Event, as defined in the Company’s 2015 Stock Option and
Grant Plan (the :Plan”), all of the shares shall vest immediately upon the Completion of a Sale Event. 

(f)    Reimbursement of Expenses. Company shall reimburse Executive for all ordinary and reasonable out-of-pocket business expenses incurred by Executive in furtherance of Company’s business in accordance with Company’s policies with respect thereto as in effect
from time to time. Executive must submit any request for reimbursement no later than ninety (90) days following the date that such business expense is incurred. All reimbursements provided under this Agreement shall be made or provided in
accordance with the requirements of Section 409A including, where applicable, the requirement that (i) any reimbursement is for expenses incurred during Executive’s lifetime (or during a shorter period of time specified in this
Agreement); (ii) the amount of expenses eligible for reimbursement during a calendar year may not affect the expenses eligible for reimbursement in any other calendar year; (iii) the reimbursement of an eligible expense shall be made no later than
the last day of the calendar year following the year in which the expense is incurred; and (iv) the right to reimbursement or in kind benefits is not subject to liquidation or exchange for another benefit. 

(g)    Indemnification. Executive shall be entitled to indemnification with respect to Executive’s services
provided hereunder pursuant to Delaware law, the terms and conditions of 

  
 - 4 - 

 
Company’s certificate of incorporation and/or by-laws, Company’s directors and officers (“D&O”) liability insurance policy, and
Company’s standard indemnification agreement for directors and officers as executed by Company and Executive. 

4.    Payments Upon Termination. 

(a)    Definition of Accrued Obligations. For purposes of this Agreement, “Accrued Obligations” means the
portion of Executive’s Base Salary that has accrued prior to any termination of Executive’s employment with Company and has not yet been paid, and the amount of any expenses properly incurred by Executive on behalf of Company prior to any
such termination and not yet reimbursed. Executive’s entitlement to any other compensation or benefit under any plan of Company shall be governed by and determined in accordance with the terms of such plans, except as otherwise specified in
this Agreement. 
 (b)    Termination by Company for Cause, by Executive Without Good Reason, or as a Result of
Executive’s Disability or Death. If Executive’s employment hereunder is terminated by Company for Cause, by Executive without Good Reason, or as a result of Executive’s Disability or death, then Company shall pay the Accrued
Obligations to Executive promptly following the effective date of such termination. 
 (c)    Termination by Company
Without Cause or by Executive For Good Reason. In the event that Executive’s employment is terminated by action of Company other than for Cause, or Executive terminates Executive’s employment for Good Reason, then, in addition to the
Accrued Obligations, Executive shall receive the following, subject to the terms and conditions of Section 4(d): 

(i)    Severance Payments. Payment in an amount equal to Executive’s then-current Base Salary for a Twelve
(12) month period, less customary and required taxes and employment- related deductions, paid in one lump sum amount on the first payroll date following the date on which the separation agreement under Section 4(d) becomes effective
and non-revocable; provided that such payment shall be made within seventy (70) days following the effective date of termination from employment, and further provided that if the 70th day
falls in the calendar year following the year during which the termination or separation from service occurred, then the payments will commence in such subsequent calendar year, and further provided that if such payments commence in such
subsequent year, the first such payment shall be a lump sum in an amount equal to the payments that would have come due since Employee’s separation from service. 

(ii)    Benefits Payments. Upon completion of appropriate forms and subject to applicable terms and conditions
under the Consolidated Omnibus Budget Reconciliation Act of 1985, as amended (“COBRA”), Company shall continue to provide Executive medical insurance coverage at no cost to Executive to the same extent that such insurance continues to be
provided to similarly situated executives at the time of Executive’s termination, until the earlier to occur of Twelve (12) months following Executive’s termination date or the date Executive begins employment with another
employer. Executive shall bear responsibility for applying for COBRA continuation coverage. 

  
 - 5 - 

 (d)    Execution of Separation Agreement. Company shall not be
obligated to pay Executive severance payments or benefits described in this Section 4 unless Executive has executed (without revocation) a timely separation agreement in a form acceptable to Company, which shall include a release of claims and
standard terms regarding non-disparagement, confidentiality, cooperation and the like, which shall be provided to Executive within ten (10) days following separation from service, and signed by Executive and returned to Company no later
than sixty (60) days following Executive’s separation from service (the “Review Period”). 

(e)    COBRA. 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 “Act”) or Section 105(h) of the Code, the COBRA premiums paid by 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 Act 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 Sections 4(b) or 4(c) above. 

5.    Prohibited Competition And Solicitation. In light of the competitive and proprietary aspects of
the business of Company, and as a condition of employment hereunder, Executive agrees to execute and abide by Company’s Confidentiality, Assignment of Inventions and Non-Competition Agreement. 

6.    Property and Records. Upon the termination of Executive’s employment hereunder, or if
Company otherwise requests, Executive shall: (a) return to Company all tangible business information and copies thereof (regardless how such Confidential Information or copies are maintained), and (b) deliver to Company any property
of Company which may be in Executive’s possession, including, but not limited to, cell phones, smart phones, laptops, products, materials, memoranda, notes, records, reports or other documents or photocopies of the same. 

7.    Code Sections 409A and 280G. 

(a)    In the event that the payments or benefits set forth in Section 4 of this Agreement constitute “non-qualified deferred compensation” subject to Section 409A, then the following conditions apply to such payments or benefits: 

(i)    Any termination of Executive’s employment triggering payment of benefits under Section 4 must constitute
a “separation from service” under Section 409A(a)(2)(A)(i) of the Code and Treas. Reg. §1.409A-l(h) before distribution of such benefits can commence. To the extent that the termination of Executive’s employment does
not 

  
 - 6 - 

 
constitute a separation of service under Section 409A(a)(2)(A)(i) of the Code and Treas. Reg. § 1.409A-1 (h) (as the result of further services that are reasonably anticipated to
be provided by Executive to Company at the time Executive’s employment terminates), any such payments under Section 4 that constitute deferred compensation under Section 409A shall be delayed until after the date of a
subsequent event constituting a separation of service under Section 409A(a)(2)(A)(i) of the Code and Treas. Reg. §1.409A-l(h). For purposes of clarification, this Section 7(a) shall not cause any forfeiture of benefits
on Executive’s part, but shall only act as a delay until such time as a “separation from service” occurs. 

(ii)    Notwithstanding any other provision with respect to the timing of payments under Section 4 if, at the time
of Executive’s termination, Executive is deemed to be a “specified employee” of Company (within the meaning of Section 409A(a)(2)(B)(i) of the Code), then limited only to the extent necessary to comply with the requirements of
Section 409A, any payments to which Executive may become entitled under Section 4 which are subject to Section 409A (and not otherwise exempt from its application) shall be withheld until the first (1st) business day of the seventh (7th) month following the termination of Executive’s employment, at which time Executive shall be paid an
aggregate amount equal to the accumulated, but unpaid, payments otherwise due to Executive under the terms of Section 4. 

(b)    It is intended that each installment of the payments and benefits provided under Section 4 of this Agreement
shall be treated as a separate “payment” for purposes of Section 409A. Neither Company nor Executive shall have the right to accelerate or defer the delivery of any such payments or benefits except to the extent specifically
permitted or required by Section 409A. 
 (c)    Notwithstanding any other provision of this Agreement to the
contrary, this Agreement shall be interpreted and at all times administered in a manner that avoids the inclusion of compensation in income under Section 409A, or the payment of increased taxes, excise taxes or other penalties under
Section 409A. The parties intend this Agreement to be in compliance with Section 409A. Executive acknowledges and agrees that Company does not guarantee the tax treatment or tax consequences associated with any payment or
benefit arising under this Agreement, including but not limited to consequences related to Section 409A. 

(d)    If any payment or benefit Executive would receive under this Agreement, when combined with any other payment or
benefit Executive receives pursuant to a change of control (for purposes of this section, a “Payment”) would: (i) constitute a “parachute payment” within the meaning of Section 280G the Code; and
(ii) but for this sentence, be subject to the excise tax imposed by Section 4999 of the Code (the “Excise Tax”), then such Payment shall be either: (A) the full amount of such Payment; or
(B) such lesser amount as would result in no portion of the Payment being subject to the Excise Tax, whichever of the foregoing amounts, taking into account the applicable federal, state and local employments taxes, income taxes and the
Excise Tax, results in Executive’s receipt, on an after-tax basis, of the greater amount of the Payment notwithstanding that all or some portion of the Payment may be subject to the Excise Tax. With respect to subsection (B), if there is more
than one method of reducing the payment as would result in no portion of the Payment being subject to the Excise Tax, then Executive shall determine which method shall be followed, provided that if Executive fails to make such determination
within thirty (30) days after Company has sent Executive written notice of the need for such reduction, Company may determine the amount of such reduction in its sole discretion. 

  
 - 7 - 

 8.    General. 

(a)    Notices. Except as otherwise specifically provided herein, any notice required or permitted by this Agreement
shall be in writing and shall be delivered as follows with notice deemed given as indicated: (i) by personal delivery when delivered personally; (ii) by overnight courier upon written verification of receipt; (iii) by
telecopy or facsimile transmission upon acknowledgment of receipt of electronic transmission; or (iv) by certified or registered mail, return receipt requested, upon verification of receipt. 

 

	 	•	 	 Notices to Executive shall be sent to: 

The last known address in Company’s records or such other address as Executive may specify in writing. 

 

	 	•	 	 Notices to Company shall be sent to: 

Checkmate Pharmaceuticals, Inc. 

101 Main St., 14th Floor 

Cambridge, MA 02142 

Attn: President and CEO 

or to such other Company representative as Company may specify in ‘writing, with a copy to: 

Goodwin Procter LLP 

100 Northern Avenue 

Boston, MA 02210 

(b)    Modifications; Amendments; Waivers; Consents. The terms of this Agreement may be modified or amended only by
written agreement executed by the parties hereto. The terms of this Agreement may be waived, or consent for the departure therefrom granted, only by written document executed by the party entitled to the benefits of such terms or provisions. No such
waiver or consent shall be deemed to be or shall constitute a waiver or consent with respect to any other terms of this Agreement, whether or not similar. Each such waiver or consent shall be effective only in the specific instance and for the
purpose for which it was given, and shall not constitute a continuing waiver or consent. 
 (c)    Assignment.
Company may assign its rights and obligations hereunder to any person or entity that succeeds to all or substantially all of Company’s business or that aspect of Company’s business in which Executive is principally involved. Executive may
not assign Executive’s rights and obligations under this Agreement without the prior written consent of Company. 

  
 - 8 - 

 (d)    Governing Law; Jurisdiction; Venue. This Agreement shall
be governed by and construed in accordance with the substantive laws of the Commonwealth of Massachusetts, without giving effect to any choice or conflict of law provision or rule. Any legal action permitted by this Agreement to enforce an award or
for a claimed breach shall be governed by the laws of the Commonwealth of Massachusetts and shall be commenced and maintained solely in any state or federal court located in the Commonwealth of Massachusetts, and both parties hereby submit to the
jurisdiction and venue of any such court. 
 (e)    Headings and Captions. The headings and captions of the
various subdivisions of this Agreement are for convenience of reference only and shall in no way modify or affect the meaning or construction of any of the terms or provisions hereof. 

(f)    Entire Agreement. This Agreement, together with the other agreements specifically referenced herein,
embodies the entire agreement and understanding between the parties hereto with respect to the subject matter hereof and supersedes all prior oral or written agreements and understandings relating to the subject matter hereof. No statement,
representation, warranty, covenant or agreement of any kind not expressly set forth in this Agreement shall affect, or be used to interpret, change or restrict, the express terms and provisions of this Agreement. 

This Agreement may be executed in two or more counterparts, and by different parties hereto on separate counterparts, each of which shall be
deemed an original, but all of which together shall constitute one and the same instrument. For all purposes a signature by fax shall be treated as an original. 

IN WITNESS WHEREOF, the parties hereto have executed this Agreement as of the date first written above. 

 

							
	ARTHUR M. KRIEG	 		 	CHECKMATE PHARMACEUTICALS, INC.
				
	 /s/ Arthur M. Krieg
	 		 	By:	 	 /s/ Barry Labinger

	Signature	 		 		 	Name: Barry Labinger
		 		 		 	Title: President and CEO

  
 - 9 - 

 AMENDMENT NO. 1 

TO 
 EMPLOYMENT AGREEMENT

 THIS AMENDMENT NO. 1 (this “Amendment”) to that certain Executive Employment Agreement, dated as of April 8, 2020 (the
“Employment Agreement”), by and between Checkmate Pharmaceuticals, Inc., a corporation, and Arthur M. Krieg, M.D. (the “Executive”) is made and entered into by and between the Executive and the Company, effective
upon the completion of the Company’s initial public offering (the “Effective Date”). Capitalized terms used and not otherwise defined herein shall have the meanings ascribed to such terms in the Employment Agreement. 

WHEREAS, the Executive and the Company are party to the Employment Agreement; 

WHEREAS, the Company desires to continue to employ the Executive and the Executive desires to continue to be employed by the Company; and 

WHEREAS, the Executive and the Company desire to amend the Employment Agreement effective as of the Effective Date as set forth herein. 

NOW, THEREFORE, in consideration of the foregoing and for other good and valuable consideration, the receipt and sufficiency of which are
hereby acknowledged, the Executive and the Company hereby agree to amend the Employment Agreement effective as of the Effective Date as follows: 

1.    The following shall be inserted as a new Section 2(f): 

(f)    Definition of “Change in Control”. For purposes of this Agreement, “Change in Control”
shall mean “Sale Event” as such term is defined in the Checkmate Pharmaceuticals, Inc. 2020 Stock Option and Incentive Plan, as the same may be amended from time to time. 

2.    The following shall be inserted as a new Section 2(g): 

(g)    Definition of “Change in Control Period”. For purposes of this Agreement, “Change in Control
Period” means the twelve (12) month period beginning on the date the Change in Control occurs. 
 3.    The
following shall be inserted as a new Section 2(h): 
 (h)    Definition of “IPO”. For purposes of
this Agreement, “IPO” means the first offering by the Company of its equity securities to the public pursuant to an effective registration statement filed under the Securities Act of 1933, as amended, or under any similar law then in
effect. 

  
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 4.    Section 2(e) of the Employment Agreement is deleted and replaced
with the following: 
 Definition of “Good Reason”. As used herein, “Good Reason” shall mean the following actions
by Company, in each case without Executive’s consent: (i) relocation of Executive’s principal business location to a location more than fifty (50) miles from Executive’s then-current business location; (ii) a material
diminution in Executive’s duties, authority or responsibilities; or (iii) a material reduction in Executive’s Base Salary unrelated to a Company-wide reduction in officer compensation; provided that (A) Executive provides
Company with written notice that Executive intends to terminate Executive’s employment hereunder for one of the circumstances set forth in this Section 2(e) within thirty (30) days of such circumstance occurring, (B) if such
circumstance is capable of being cured, Company has failed to cure such circumstance within a period of thirty (30) days from the date of such written notice, and (C) Executive terminates Executive’s employment within sixty five
(65) days from the date that Good Reason first occurs. For purposes of clarification, the above-listed conditions shall apply separately to each occurrence of Good Reason and failure to adhere to such conditions in the event of Good Reason
shall not disqualify Executive from asserting Good Reason for any subsequent occurrence of Good Reason. For purposes of this Agreement, “Good Reason” shall be interpreted in a manner, and limited to the extent necessary, so that it shall
not cause adverse tax consequences for either party with respect to Section 409A (“Section 409A”) of the Internal Revenue Code of 1986, as amended (the “Code”), and any successor statute, regulation and guidance
thereto. Notwithstanding the foregoing, any of the actions described in subclause (ii) herein that are taken in connection with a transaction in which the owners of the Company’s outstanding voting power immediately prior to such
transaction do not own at least a majority of the outstanding voting power of the Company or any successor entity immediately upon completion of the transaction other than as a result of the acquisition of securities directly from the Company shall
not be deemed to constitute an occurrence of Good Reason. 
 5.    The first sentence of Section 3(a) of the
Employment Agreement is deleted and replaced with the following: 
 Company shall pay Executive a base salary (the “Base Salary”)
at the annual rate of four hundred twenty-five thousand dollars ($425,000). 
 6.    The first sentence of
Section 3(b) of the Employment Agreement is deleted and replaced with the following: 
 Executive shall be eligible to receive an annual
cash bonus (the “Annual Performance Bonus”), with the target amount of such Annual Performance Bonus equal to Forty Percent (40%) of Executive’s Base Salary in the year to which the Annual Performance Bonus relates (the “Target
Bonus Amount”), provided that the actual amount of the Annual Performance Bonus may be greater or less than such Target Bonus Amount. 

7.    Section 3(e) of the Employment Agreement is deleted in its entirety and replaced with the following: 

(e)    Equity Incentive Awards. Executive will be eligible to receive grants under the Company’s equity
incentive program once the Company has completed an initial public offering consistent with the Company’s policies and grants for other C-level employees, assuming continued employment or service. 

  
 - 11 - 

 8.    Section 4(c) of the Employment Agreement is deleted in its
entirety and replaced with the following: 
 (c)    Severance Pay and Benefits Upon Termination by the Company without
Cause or by the Executive for Good Reason Outside the Change in Control Period. If the Executive’s employment is terminated by the Company without Cause or the Executive terminates employment for Good Reason, each outside of the Change in
Control Period, then, in addition to the Accrued Obligations, and 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 obligations under the Company’s Confidentiality, Assignment of Inventions and
Non-Competition Agreement of the Agreement, and any other provisions of this Agreement intended to survive its termination (“Continuing Obligations”), and shall provide that if the Executive breaches
any of the Continuing Obligations, all payments or provisions of the Severance Pay and Benefits shall immediately cease (and may be subject to recoupment) without affecting the other provisions thereof (the “Separation Agreement and
Release”), and (ii) the Separation Agreement and Release becoming effective irrevocable, all within 60 days after the date of termination (or such shorter period as set forth in the Separation Agreement and Release), the Company will pay
or provide (as applicable) the following (collectively, the “Severance Pay and Benefits”): 

(i)    an amount equal to 9 months of the Executive’s Base Salary (the “Severance Amount”);
and 
 (ii)    if the Executive was participating in the Company’s group health, dental and/or
vision plans immediately prior to the date of termination and properly elects to continue health coverage under the Consolidated Omnibus Budget Reconciliation Act of 1985, as amended (“COBRA”), then, subject to the Executive’s
copayment of the premium amounts at the applicable active employees’ rate, the Company shall pay to the group health plan provider, the COBRA provider or the Executive a monthly payment equal to the monthly employer contribution that the
Company would have made to provide health insurance to the Executive if the Executive had remained employed by the Company until the earliest of the following: (i) the last day of the nine-month period following the date of termination;
(ii) the Executive’s eligibility for group medical plan benefits under any other employer’s group medical plan or otherwise through other employment; or (iii) the cessation of the Executive’s continuation
coverage rights under COBRA. Notwithstanding the foregoing, if the Company determines at any time that its payments pursuant to this paragraph may be taxable income to the Executive or that it cannot pay such amounts to the group health plan
provider or the COBRA provider (if 

  
 - 12 - 

 
applicable) without potentially violating applicable law (including, without limitation, Section 2716 of the Public Health Service Act), then the Company may convert such payments to payroll
payments directly to the Executive for the time period specified above; and such payments shall be subject to tax-related deductions and withholdings and shall be paid on the Company’s regular payroll
dates. Any other premiums or costs of COBRA continuation coverage not provided above (including, without limitation, for any COBRA coverage after the time period set forth above) shall be at the sole expense of the Executive. 

The amounts payable under this Section 4(c), to the extent taxable, shall be paid out in substantially equal installments in accordance
with the Company’s payroll practice over 9 months 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, to the extent it qualifies as “non-qualified deferred compensation” within the meaning of Section 409A of the Code, 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). 

9.    The following shall be inserted as a new Section 4(d): 

(d)    Severance Pay and Benefits 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 4(d) shall apply in lieu of, and expressly supersede, the provisions of Section 4(c) if the date of termination occurs during the Change in Control Period.
These provisions shall terminate and be of no further force or effect after a Change in Control Period. If the Executive’s employment is terminated by the Company without Cause or the Executive terminates employment for Good Reason and, in each
case, the date of termination occurs during the Change in Control Period, then, in addition to the Accrued Obligations, and subject to (i) the Executive signing a Separation Agreement and Release meeting all of the requirements specified
in Section 4(c) of this Agreement, including a reaffirmation that if the Executive breaches any of the Continuing Obligations, all payments or provisions of the Change in Control Pay and Benefits shall immediately cease and may be
subject to recoupment, and (ii) the Separation Agreement and Release becoming effective irrevocable, all within 60 days after the date of termination (or such shorter period as set forth in the Separation Agreement and Release), the
Company will pay or provide (as applicable) the following (collectively, the “Change in Control Pay and Benefits”): 

(i)    the Company shall pay the Executive a lump sum in cash in an amount equal to the
(A) Executive’s then current Base Salary, plus (B) the Target Bonus Amount; 

(ii)    notwithstanding anything to the contrary in any applicable option agreement or other stock-based
award agreement, all time-based stock options and 

  
 - 13 - 

 
other stock-based awards subject to time-based vesting held by the Executive (the “Time-Based Equity Awards”) and granted after the Company’s IPO shall immediately accelerate and
become fully exercisable or nonforfeitable as of the later of (A) the date of termination or (B) the effective date of the Separation Agreement and Release (the “Accelerated Vesting Date”); provided that any
termination or forfeiture of the unvested portion of such Time-Based Equity Awards that would otherwise occur on the date of termination in the absence of this Agreement will be delayed until the effective date of the Separation Agreement and
Release and will only occur if the vesting pursuant to this subsection does not occur due to the absence of the Separation Agreement and Release becoming fully effective within the time period set forth therein. Notwithstanding the foregoing, no
additional vesting of the Time-Based Equity Awards shall occur during the period between the Executive’s date of termination and the Accelerated Vesting Date; and 

(iii)    if the Executive was participating in the Company’s group health, dental and/or vision plans
immediately prior to the date of termination and properly elects to continue health coverage under the Consolidated Omnibus Budget Reconciliation Act of 1985, as amended (“COBRA”), then, the Company shall continue to provide Executive
medical insurance coverage at no cost to Executive to the same extent that such insurance continues to be provided to similarly situated executives at the time of Executive’s termination until the earliest of the following: (i) the first
anniversary of the date of termination; (ii) the Executive’s eligibility for group medical plan benefits under any other employer’s group medical plan or otherwise through other employment; or (iii) the cessation of
the Executive’s continuation coverage rights under COBRA. Notwithstanding the foregoing, if the Company determines at any time that its payments pursuant to this paragraph may be taxable income to the Executive or that it cannot pay such
amounts to the group health plan provider or the COBRA provider (if applicable) without potentially violating applicable law (including, without limitation, Section 2716 of the Public Health Service Act), then the Company may convert
such payments to payroll payments directly to the Executive for the time period specified above; and such payments shall be subject to tax-related deductions and withholdings and shall be paid on the
Company’s regular payroll dates. Any other premiums or costs of COBRA continuation coverage not provided above (including, without limitation, for any COBRA coverage after the time period set forth above) shall be at the sole expense of the
Executive. 
 The amounts payable under this Section 4(d), to the extent taxable, shall be paid or commence to be paid within 60 days
after the date of termination. 
 10.    All Agreement references to section numbers and defined terms are amended to
reflect the above modifications. 

  
 - 14 - 

 11.    Except to the extent expressly modified or amended by this
Amendment, all terms and provisions of the Employment Agreement shall continue in full force and effect and shall remain enforceable and binding in accordance with their respective terms. 

12.    Any required notices, meetings or consents that are necessary to make an amendment to the Employment Agreement are
hereby waived or satisfied. 
 13.    This Amendment may be executed in counterparts, each of which shall be deemed an
original, but all of which together shall be deemed to be one and the same agreement. A signed copy of this Amendment delivered by facsimile, e-mail or other means of electronic transmission shall be deemed to
have the same legal effect as delivery of an original signed copy of this Amendment. 

  
 - 15 - 

 IN WITNESS WHEREOF, the undersigned have executed this Amendment effective as of the date
first set forth above. 
  

			
	COMPANY:
	
	CHECKMATE PHARMACEUTICALS, INC., a Delaware Corporation
		
	By:	 	 /s/ Barry Labinger

	Name:	 	Barry Labinger
	Title:	 	President and Chief Executive Officer
	
	EXECUTIVE:
		
	By:	 	 /s/ Arthur M. Krieg

	Name:	 	Arthur M. Krieg

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