Document:

EX-10.15

 Exhibit 10.15 

Employment Agreement 

This Employment Agreement (this “Agreement”), dated as of October 29, 2020, is made by and between SQZ Biotechnologies
Company, a Delaware corporation (together with any successor thereto, the “Company”), and Lawrence Knopf (“Executive”) (collectively referred to herein as the “Parties” or individually referred to
as a “Party”), and will become effective, if at all, upon the date of the Company’s initial public offering of stock (“IPO”) pursuant to an effective registration statement filed under the Securities Act of
1933, as amended (the “Effective Date”). 
 RECITALS 

 

	A.	 It is the desire of the Company to assure itself of the services of Executive as of the Effective Date and
thereafter by entering into this Agreement. 

  

	B.	 Executive and the Company mutually desire that Executive provide services to the Company on the terms herein
provided. 

 AGREEMENT 

NOW, THEREFORE, in consideration of the foregoing and of the respective covenants and agreements set forth below, the Parties hereto agree as
follows: 
 1. Employment. 
 (a)
General. Effective on the Effective Date, the Company shall employ Executive, and Executive shall be employed by the Company, for the period and in the positions set forth in this Section 1, and subject to the other
terms and conditions herein provided; provided, however, that this Agreement is expressly conditioned upon the IPO closing before March 31, 2021 and will be null and void if this condition is not satisfied. 

(b) At-Will Employment. The Company and Executive acknowledge that Executive’s employment
is and shall continue to be at-will, as defined under applicable law, and that Executive’s employment with the Company may be terminated by either Party at any time for any or no reason (subject to the
notice requirements of Section 3(b)). This “at-will” nature of Executive’s employment shall remain unchanged during Executive’s tenure as an employee and may not
be changed, except in an express writing signed by Executive and a duly authorized officer of the Company. If Executive’s employment terminates for any reason, Executive shall not be entitled to any payments, benefits, damages, award or
compensation other than as provided in this Agreement or otherwise agreed to in writing by the Company or as provided by applicable law. The term of this Agreement (the “Term”) shall commence on the Effective Date and end on the
date this Agreement is terminated under Section 3. 
 (c) Positions and Duties. During the Term, Executive
shall serve as General Counsel of the Company, with such responsibilities, duties and authority normally associated with such position and as may from time to time be assigned to Executive by the Chief Executive Officer of the Company. Executive
shall devote substantially all of Executive’s working time and efforts to the business and affairs of the Company (which shall include service to its affiliates, if applicable) and shall not engage in outside business activities (including
serving on outside boards or committees) without the consent of the Board of Directors of the Company or an authorized committee of the Board (in either case, the “Board”), provided that Executive shall be permitted to
(i) manage Executive’s personal, financial and legal affairs, (ii) participate in trade associations, and (iii) serve on the board of directors of
not-for-profit or tax-

 
exempt charitable organizations, in each case, subject to compliance with this Agreement and provided that such activities do not materially interfere with Executive’s performance of
Executive’s duties and responsibilities hereunder. Executive agrees to observe and comply with the rules and policies of the Company as adopted by the Company from time to time, in each case, as amended from time to time, and as delivered or
made available to Executive (each, a “Policy”). 
 2. Compensation and Related Matters. 

(a) Annual Base Salary. During the Term, Executive shall receive a base salary at a rate of $335,000 per annum, which shall be paid in
accordance with the customary payroll practices of the Company and shall be pro-rated for partial years of employment. Such annual base salary shall be reviewed (and may be adjusted) from time to time by the
Board (such annual base salary, as it may be adjusted from time to time, the “Annual Base Salary”). 
 (b) Annual Cash
Bonus Opportunity. During the Term, Executive will be eligible to participate in an annual incentive program established by the Board. Executive’s annual incentive compensation under such incentive program (the “Annual
Bonus”) shall be targeted at 40% of Executive’s Annual Base Salary (such target, as may be adjusted by the Board from time to time, the “Target Annual Bonus”). The Annual Bonus payable under the incentive program shall
be based on the achievement of performance goals to be determined by the Board and may in the Board’s discretion be calculated in a manner intended to reflect any mid-year changes in Annual Base Salary or
Target Annual Bonus. The payment of any Annual Bonus pursuant to the incentive program shall be subject to Executive’s continued employment with the Company through the date of payment, except as otherwise provided in
Section 4(b). 
 (c) Benefits. During the Term, Executive shall be eligible to participate in employee
benefit plans, programs and arrangements of the Company, subject to the terms and eligibility requirements thereof and as such plans, programs and arrangements may be amended or in effect from time to time. In no event shall Executive be eligible to
participate in any severance plan or program of the Company, except as set forth in Section 4 of this Agreement. 

(d) Vacation. During the Term, Executive shall be entitled to paid personal leave in accordance with the Company’s Policies. Any
vacation shall be taken at the reasonable and mutual convenience of the Company and Executive. 
 (e) Business Expenses. During the
Term, the Company shall reimburse Executive for all reasonable travel and other business expenses incurred by Executive in the performance of Executive’s duties to the Company in accordance with the Company’s expense reimbursement Policy.

 (f) Key Person Insurance. At any time during the Term, the Company shall have the right (but not the obligation) to insure the
life of Executive for the Company’s sole benefit. The Company shall have the right to determine the amount of insurance and the type of policy. Executive shall reasonably cooperate with the Company in obtaining such insurance by submitting to
physical examinations, by supplying all information reasonably required by any insurance carrier, and by executing all necessary documents reasonably required by any insurance carrier, provided that any information provided to an insurance company
or broker shall not be provided to the Company without the prior written authorization of Executive. Executive shall incur no financial obligation by executing any required document, and shall have no interest in any such policy. 

  
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 3. Termination. 

Executive’s employment hereunder and the Term may be terminated by the Company or Executive, as applicable, without any breach of this
Agreement under the following circumstances and the Term will end on the Date of Termination: 
 (a) Circumstances. 

(i) Death. Executive’s employment hereunder shall terminate upon Executive’s death. 

(ii) Disability. If Executive has incurred a Disability, as defined below, the Company may terminate Executive’s
employment. 
 (iii) Termination for Cause. The Company may terminate Executive’s employment for Cause, as
defined below. 
 (iv) Termination without Cause. The Company may terminate Executive’s employment without Cause.

 (v) Resignation from the Company with Good Reason. Executive may resign Executive’s employment with the
Company with Good Reason, as defined below. 
 (vi) Resignation from the Company without Good Reason. Executive may
resign Executive’s employment with the Company for any reason other than Good Reason or for no reason. 
 (b) Notice of
Termination. Any termination of Executive’s employment by the Company or by Executive under this Section 3 (other than termination pursuant to Section 3(a)(i)) shall be communicated by a
written notice to the other Party hereto (i) indicating the specific termination provision in this Agreement relied upon, (ii) setting forth in reasonable detail the facts and circumstances claimed to provide a basis for termination of
Executive’s employment under the provision so indicated, if applicable, and (iii) specifying a Date of Termination which, if submitted by Executive, shall be at least thirty (30) days following the date of such notice (a
“Notice of Termination”); provided, however, that in the event that Executive delivers a Notice of Termination to the Company, the Company may, in its sole discretion, change the Date of Termination to any date that occurs
following the date of the Company’s receipt of such Notice of Termination and is prior to the date specified in such Notice of Termination, but the termination will still be considered a resignation by Executive. A Notice of Termination
submitted by the Company may provide for a Date of Termination on the date Executive receives the Notice of Termination, or any date thereafter elected by the Company. The failure by either Party to set forth in the Notice of Termination any fact or
circumstance which contributes to a showing of Cause or Good Reason shall not waive any right of the Party hereunder or preclude the Party from asserting such fact or circumstance in enforcing the Party’s rights hereunder. 

(c) Company Obligations upon Termination. Upon termination of Executive’s employment pursuant to any of the circumstances listed
in this Section 3, Executive (or Executive’s estate) shall be entitled to receive the sum of: (i) the portion of Executive’s Annual Base Salary earned through the Date of Termination, but not yet paid to
Executive; (ii) any expense reimbursements owed to Executive pursuant to Section 2(e); and (iii) any amount accrued and arising from Executive’s participation in, or benefits accrued under any employee
benefit plans, programs or arrangements, which amounts shall be 

  
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payable in accordance with the terms and conditions of such employee benefit plans, programs or arrangements (collectively, the “Company Arrangements”). Except as otherwise
expressly required by law (e.g., COBRA) or applicable plan, program, or arrangement or as specifically provided herein, all of Executive’s rights to salary, severance, benefits, bonuses and other compensatory amounts hereunder (if any)
shall cease upon the termination of Executive’s employment hereunder. In the event that Executive’s employment is terminated by the Company for any reason, Executive’s sole and exclusive remedy shall be to receive the payments and
benefits described in this Section 3(c) or Section 4, as applicable. 
 (d) Deemed
Resignation. Upon termination of Executive’s employment for any reason, Executive shall be deemed to have resigned from all offices and directorships, if any, then held with the Company or any of its subsidiaries. 

4. Severance Payments. 
 (a)
Termination for Cause, or Termination Upon Death, Disability or Resignation from the Company Without Good Reason. If Executive’s employment shall terminate as a result of Executive’s death pursuant to
Section 3(a)(i) or Disability pursuant to Section 3(a)(ii), pursuant to Section 3(a)(iii) for Cause, or pursuant to Section 3(a)(vi) for
Executive’s resignation from the Company without Good Reason, then Executive shall not be entitled to any severance payments or benefits, except as provided in Section 3(c). 

(b) Termination without Cause, or Resignation from the Company with Good Reason. Subject to Section 4(c), if
Executive’s employment terminates without Cause pursuant to Section 3(a)(iv), or pursuant to Section 3(a)(v) due to Executive’s resignation with Good Reason, then except as otherwise
provided under Section 4(c) and subject to Executive signing on or before the 21st day following Executive’s Separation from Service (as defined below), and not revoking, a release of claims substantially in the form
attached as Exhibit A to this Agreement (the “Release”) and Executive’s continued compliance with Section 5, Executive shall receive, in addition to payments and benefits set forth in
Section 3(c), the following: 
 (i) an amount in cash equal to 0.75 times the Annual Base Salary,
payable in the form of salary continuation in regular installments over the 9 month period following the date of Executive’s Separation from Service (the “Severance Period”) in accordance with the Company’s normal payroll
practices; 
 (ii) to the extent unpaid as of the Date of Termination, an amount of cash equal to any Annual Bonus earned by
Executive for the Company’s fiscal year prior to the fiscal year in which the Date of Termination occurs, as determined by the Board in its discretion based upon actual performance achieved, which Annual Bonus, if any, shall be paid to
Executive in the fiscal year in which the Date of Termination occurs when bonuses for such prior fiscal year are paid in the ordinary course to actively employed senior executives of the Company; 

(iii) an amount in cash equal to the Target Annual Bonus multiplied by a fraction (A) the numerator of which is the number
of days the Executive was employed by the Company in the Company’s fiscal year in which the Executive’s termination of employment occurs, over (B) 365, payable in a lump sum on the Company’s first ordinary payroll date that occurs
after the Date of Termination; and 

  
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 (iv) if Executive timely elects to receive continued medical, dental or
vision coverage under one or more of the Company’s group medical, dental or vision plans pursuant to the Consolidated Omnibus Budget Reconciliation Act of 1985, as amended (“COBRA”), then the Company shall directly pay, or
reimburse Executive for, the COBRA premiums for Executive and Executive’s covered dependents under such plans, less the amount Executive would have had to pay to receive such coverage as an active employee based on the cost sharing levels in
effect on the Date of Termination, during the period commencing on Executive’s Separation from Service and ending upon the earliest of (A) the last day of the Severance Period, (B) the date that Executive and/or Executive’s
covered dependents become no longer eligible for COBRA or (C) the date Executive becomes eligible to receive medical, dental or vision coverage, as applicable, from a subsequent employer (and Executive agrees to promptly notify the Company of
such eligibility) (the “COBRA Continuation Period”). Notwithstanding the foregoing, if the Company determines it cannot provide the foregoing benefit without potentially violating applicable law (including, without limitation,
Section 2716 of the Public Health Service Act) or incurring an excise tax, the Company shall in lieu thereof provide to Executive a taxable monthly payment in an amount equal to the monthly COBRA premium that Executive would be required to pay
to continue Executive’s and Executive’s covered dependents’ group health coverage in effect on the Date of Termination (which amount shall be based on the premium for the first month of COBRA coverage), less the amount Executive would
have had to pay to receive group health coverage as an active employee for Executive and his or her covered dependents based on the cost sharing levels in effect on the Date of Termination, which payments shall continue for the remainder of the
COBRA Continuation Period. 
 (c) Change in Control. In lieu of the payments and benefits set forth in
Section 4(b), in the event Executive’s employment terminates without Cause pursuant to Section 3(a)(iv), or pursuant to Section 3(a)(v) due to Executive’s
resignation with Good Reason, in either case, during the three (3) month period prior to the date of a Change in Control or on or within eighteen (18) months following the date of a Change in Control, subject to Executive signing on or
before the 21st day following Executive’s Separation from Service, and not revoking, the Release and Executive’s continued compliance with Section 5, Executive shall receive, in addition to the payments and
benefits set forth in Section 3(c), the following: 
 (i) an amount in cash equal to 1.0 times the
Annual Base Salary, payable in equal installments over the 12 month period following the date of Executive’s Separation from Service (the “CIC Severance Period”) in accordance with the Company’s normal payroll practices;

 (ii) the payment set forth in Section 4(b)(ii); 

(iii) the payment set forth in Section 4(b)(iii); 

(iv) the benefits set forth in Section 4(b)(iv), provided that for this purpose, the “Severance
Period” will mean the CIC Severance Period; 
 (v) an amount in cash equal to 1.0 times the Target Annual Bonus, payable
in a lump sum on the Company’s first ordinary payroll date that occurs after the later of the Change in Control or Date of Termination; and 

(vi) all unvested equity or equity-based awards held by Executive under any Company equity compensation plans that vest solely
based on continued employment or service shall immediately become 100% vested (and if the Date of Termination precedes the Change in Control, all such unvested awards shall remain outstanding and eligible to vest in accordance with this
Section 4(c)(vi) if a Change Control occurs within three (3) months after the Date of Termination, provided that in no event will any such award remain outstanding beyond the final expiration date of the award set
forth in the documents governing such award), with any other equity or equity-based awards being governed by the terms of the applicable award agreement. 

  
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 (d) Survival. Notwithstanding anything to the contrary in this Agreement, the
provisions of Sections 5 through 9 will survive the termination of Executive’s employment and the termination of the Term. 
 5.
Restrictive Covenants. As a condition to the effectiveness of this Agreement, Executive will have executed and delivered to the Company no later than contemporaneously herewith the Employee Proprietary Information and Inventions
Assignment Agreement attached as Exhibit B (the “Restrictive Covenant Agreement”). Executive agrees to abide by the terms of the Restrictive Covenant Agreement, which are hereby incorporated by reference into this Agreement.
Executive acknowledges that the provisions of the Restrictive Covenant Agreement will survive the termination of Executive’s employment and the termination of the Term for the periods set forth in the Restrictive Covenant Agreement. 

6. Assignment and Successors. 

The Company may assign its rights and obligations under this Agreement to any of its affiliates or to any successor to all or substantially
all of the business or the assets of the Company (by merger or otherwise), and may assign or encumber this Agreement and its rights hereunder as security for indebtedness of the Company and its affiliates. This Agreement shall be binding upon and
inure to the benefit of the Company, Executive and their respective successors, assigns, personal and legal representatives, executors, administrators, heirs, distributees, devisees, and legatees, as applicable. None of Executive’s rights or
obligations may be assigned or transferred by Executive, other than Executive’s rights to payments hereunder, which may be transferred only by will or operation of law. Notwithstanding the foregoing, Executive shall be entitled, to the extent
permitted under applicable law and applicable Company Arrangements, to select and change a beneficiary or beneficiaries to receive compensation hereunder following Executive’s death by giving written notice thereof to the Company. 

7. Certain Definitions. 
 (a)
Cause. The Company shall have “Cause” to terminate Executive’s employment hereunder upon: 
 (i) The
Chief Executive Officer’s or the Board’s reasonable, good faith determination that Executive has refused to (A) substantially perform the duties associated with Executive’s position with the Company or (B) carry out the
reasonable and lawful instructions of the Chief Executive Officer or the Board concerning duties or actions consistent with the Executive’s position with the Company; 

(ii) Executive’s breach of a material provision of this Agreement that, to the extent capable of cure, has remained
uncured for a period of thirty (30) days following written notice from the Company; 
 (iii) Executive’s
conviction, plea of no contest, plea of nolo contendere, or imposition of unadjudicated probation for any felony or crime involving moral turpitude; 

  
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 (iv) Executive’s unlawful use (including being under the influence) or
possession of illegal drugs on the Company’s (or any of its affiliate’s) premises or while performing Executive’s duties and responsibilities under this Agreement; or 

(v) Executive’s commission of any act of fraud, embezzlement, misappropriation, willful misconduct, or breach of fiduciary
duty against the Company or any of its affiliates. 
 (b) Change in Control. “Change in Control” shall have the meaning set
forth in the SQZ Biotechnologies Company 2020 Incentive Award Plan, as in effect on the Effective Date. 
 (c) Code. “Code”
shall mean the Internal Revenue Code of 1986, as amended, and the regulations and guidance promulgated thereunder. 
 (d) Date of
Termination. “Date of Termination” shall mean (i) if Executive’s employment is terminated by Executive’s death, the date of Executive’s death; or (ii) if Executive’s employment is terminated pursuant to
Section 3(a)(ii) – (vi) either the date indicated in the Notice of Termination or the date specified by the Company pursuant to Section 3(b), whichever is earlier. 

(e) Disability. “Disability” shall mean, at any time the Company or any of its affiliates sponsors a long-term disability
plan for the Company’s employees, “disability” as defined in such long-term disability plan for the purpose of determining a participant’s eligibility for benefits, provided, however, if the long-term disability plan
contains multiple definitions of disability, “Disability” shall refer to that definition of disability which, if Executive qualified for such disability benefits, would provide coverage for the longest period of time. The determination of
whether Executive has a Disability shall be made by the person or persons required to make disability determinations under the long-term disability plan. At any time the Company does not sponsor a long-term disability plan for its employees,
“Disability” shall mean Executive’s inability to perform, with or without reasonable accommodation, the essential functions of Executive’s positions hereunder for a total of three months during any
six-month period as a result of incapacity due to mental or physical illness as determined by a physician selected by the Company or its insurers and acceptable to Executive or Executive’s legal
representative, with such agreement as to acceptability not to be unreasonably withheld or delayed. Any refusal by Executive to submit to a medical examination for the purpose of determining Disability shall be deemed to constitute conclusive
evidence of Executive’s Disability. 
 (f) Good Reason. For the sole purpose of determining Executive’s right to severance
payments and benefits as described above, Executive’s resignation will be with “Good Reason” if Executive resigns within ninety (90) days after any of the following events, unless Executive consents in writing to the applicable
event: (i) a reduction in Executive’s Annual Base Salary or Target Annual Bonus (if any), other than a reduction in Annual Base Salary of less than 10% that is implemented in connection with a contemporaneous reduction in annual base
salaries affecting other senior executives of the Company, (ii) a material decrease in Executive’s authority or areas of responsibility as are commensurate with Executive’s title or position with the Company, including Executive
ceasing to report directly to the chief executive officer of the Company’s ultimate parent company following a Change in Control (or of the Company if there is no such parent entity), (iii) the relocation of Executive’s primary office to a
location more than fifty (50) miles from the Executive’s primary office as of the date of this Agreement or (iv) the Company’s breach of a material provision of this Agreement. Notwithstanding the foregoing, no Good Reason will
have occurred unless and until: (a) Executive has provided the Company, within sixty (60) days of Executive’s knowledge of the occurrence of the facts and circumstances underlying the Good Reason event, written notice stating with
specificity the applicable facts and circumstances underlying such finding of Good Reason; (b) the Company has had an opportunity to cure the same within thirty (30) days after the receipt of such notice; and (c) the Company shall
have failed to so cure within such period. 

  
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 8. Parachute Payments. 

(a) Notwithstanding any other provisions of this Agreement or any Company equity plan or agreement, in the event that any payment or benefit
by the Company or otherwise to or for the benefit of Executive, whether paid or payable or distributed or distributable pursuant to the terms of this Agreement or otherwise (all such payments and benefits, including the payments and benefits under
Section 4 hereof, being hereinafter referred to as the “Total Payments”), would be subject (in whole or in part) to the excise tax imposed by Section 4999 of the Code (the “Excise
Tax”), then the Total Payments shall be reduced (in the order provided in Section 8(b)) to the minimum extent necessary to avoid the imposition of the Excise Tax on the Total Payments, but only if (i) the net
amount of such Total Payments, as so reduced (and after subtracting the net amount of federal, state and local income and employment taxes on such reduced Total Payments and after taking into account the phase out of itemized deductions and personal
exemptions attributable to such reduced Total Payments), is greater than or equal to (ii) the net amount of such Total Payments without such reduction (but after subtracting the net amount of federal, state and local income and employment taxes
on such Total Payments and the amount of the Excise Tax to which Executive would be subject in respect of such unreduced Total Payments and after taking into account the phase out of itemized deductions and personal exemptions attributable to such
unreduced Total Payments). 
 (b) The Total Payments shall be reduced in the following order: (i) reduction on a pro rata basis of any
cash severance payments that are exempt from Section 409A of the Code (“Section 409A”), (ii) reduction on a pro rata basis of any non-cash severance payments or
benefits that are exempt from Section 409A, (iii) reduction on a pro rata basis of any other payments or benefits that are exempt from Section 409A, and (iv) reduction of any payments or benefits otherwise payable to Executive on
a pro rata basis or such other manner that complies with Section 409A; provided, in case of clauses (ii), (iii) and (to the extent permissible under Section 409A) (iv), that reduction of any payments attributable to the acceleration of
vesting of Company equity awards shall be first applied to Company equity awards that would otherwise vest last in time. 
 (c) All
determinations regarding the application of this Section 8 shall be made by an accounting firm or consulting group with experience in performing calculations regarding the applicability of Section 280G of the Code and
the Excise Tax selected by the Company (the “Independent Advisors”). For purposes of determinations, no portion of the Total Payments shall be taken into account which, in the opinion of the Independent Advisors, (i) does not
constitute a “parachute payment” within the meaning of Section 280G(b)(2) of the Code (including by reason of Section 280G(b)(4)(A) of the Code) or (ii) constitutes reasonable compensation for services actually rendered,
within the meaning of Section 280G(b)(4)(B) of the Code, in excess of the “base amount” (as defined in Section 280G(b)(3) of the Code) allocable to such reasonable compensation. The costs of obtaining such determination and all
related fees and expenses (including related fees and expenses incurred in any later audit) shall be borne by the Company. 
 (d) In the
event it is later determined that a greater reduction in the Total Payments should have been made to implement the objective and intent of this Section 8, the excess amount shall be returned promptly by Executive to the
Company. 

  
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 9. Miscellaneous Provisions. 

(a) Governing Law. This Agreement shall be governed, construed, interpreted and enforced in accordance with its express terms, and
otherwise in accordance with the substantive laws of the Commonwealth of Massachusetts without reference to the principles of conflicts of law of the Commonwealth of Massachusetts or any other jurisdiction that would result in the application of the
laws of a jurisdiction other than the Commonwealth of Massachusetts, and where applicable, the laws of the United States. 
 (b)
Validity. The invalidity or unenforceability of any provision or provisions of this Agreement shall not affect the validity or enforceability of any other provision of this Agreement, which shall remain in full force and effect. 

(c) Notices. Any notice, request, claim, demand, document and other communication hereunder to any Party shall be effective upon
receipt (or refusal of receipt) and shall be in writing and delivered personally or sent by facsimile or certified or registered mail, postage prepaid, as follows: 

(i) If to the Company, to the Chief Executive Officer of the Company at the Company’s headquarters, 

(ii) If to Executive, to the last address that the Company has in its personnel records for Executive, or 

(iii) At any other address as any Party shall have specified by notice in writing to the other Party. 

(d) Counterparts. This Agreement may be executed in several counterparts, each of which shall be deemed to be an original, but all of
which together will constitute one and the same Agreement. Signatures delivered by facsimile or PDF shall be deemed effective for all purposes. 

(e) Entire Agreement. The terms of this Agreement, and the Restrictive Covenant Agreement incorporated herein by reference as set forth
in Section 5, are intended by the Parties to be the final expression of their agreement with respect to the subject matter hereof and supersede all prior understandings and agreements, whether written or oral, including any
prior employment offer letter or employment agreement between Executive and the Company. The Parties further intend that this Agreement shall constitute the complete and exclusive statement of their terms and that no extrinsic evidence whatsoever
may be introduced in any judicial, administrative, or other legal proceeding to vary the terms of this Agreement. 
 (f) Amendments;
Waivers. This Agreement may not be modified, amended, or terminated except by an instrument in writing, signed by Executive and a duly authorized officer of Company. By an instrument in writing similarly executed, Executive or a duly authorized
officer of the Company may waive compliance by the other Party with any specifically identified provision of this Agreement that such other Party was or is obligated to comply with or perform; provided, however, that such waiver shall
not operate as a waiver of, or estoppel with respect to, any other or subsequent failure. No failure to exercise and no delay in exercising any right, remedy, or power hereunder will preclude any other or further exercise of any other right, remedy,
or power provided herein or by law or in equity. 

  
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 (g) Construction. This Agreement shall be deemed drafted equally by both the Parties.
Its language shall be construed as a whole and according to its fair meaning. Any presumption or principle that the language is to be construed against any Party shall not apply. The headings in this Agreement are only for convenience and are not
intended to affect construction or interpretation. Any references to paragraphs, subparagraphs, sections or subsections are to those parts of this Agreement, unless the context clearly indicates to the contrary. Also, unless the context clearly
indicates to the contrary, (i) the plural includes the singular and the singular includes the plural; (ii) “and” and “or” are each used both conjunctively and disjunctively; (iii) “any,” “all,”
“each,” or “every” means “any and all,” and “each and every”; (iv) “includes” and “including” are each “without limitation”; (v) “herein,” “hereof,”
“hereunder” and other similar compounds of the word “here” refer to the entire Agreement and not to any particular paragraph, subparagraph, section or subsection; and (vi) all pronouns and any variations thereof shall be
deemed to refer to the masculine, feminine, neuter, singular or plural as the identity of the entities or persons referred to may require. 

(h) Arbitration. Any controversy, claim or dispute arising out of or relating to this Agreement, shall be settled solely and
exclusively by a binding arbitration process administered by JAMS/Endispute in Boston, Massachusetts. Such arbitration shall be conducted in accordance with the then-existing JAMS/Endispute Rules of Practice and Procedure, with the following
exceptions if in conflict: (i) one arbitrator who is a retired judge shall be chosen by JAMS/Endispute; (ii) each Party to the arbitration will pay one-half of the expenses and fees of the
arbitrator, together with other expenses of the arbitration incurred or approved by the arbitrator; and (iii) arbitration may proceed in the absence of any Party if written notice (pursuant to the JAMS/Endispute rules and regulations) of the
proceedings has been given to such Party. Each Party shall bear its own attorney’s fees and expenses; provided that the arbitrator may assess the prevailing Party’s fees and costs against the
non-prevailing Party as part of the arbitrator’s award. The Parties agree to abide by all decisions and awards rendered in such proceedings. Such decisions and awards rendered by the arbitrator shall be
final and conclusive. All such controversies, claims or disputes shall be settled in this manner in lieu of any action at law or equity; provided, however, that nothing in this subsection shall be construed as precluding the bringing of an action
for injunctive relief or specific performance as provided in this Agreement or the Restrictive Covenant Agreement. This dispute resolution process and any arbitration hereunder shall be confidential and neither any Party nor the neutral arbitrator
shall disclose the existence, contents or results of such process without the prior written consent of all Parties, except where necessary or compelled in a court to enforce this arbitration provision or an award from such arbitration or otherwise
in a legal proceeding. If JAMS/Endispute no longer exists or is otherwise unavailable, the Parties agree that the American Arbitration Association (“AAA”) shall administer the arbitration in accordance with its then-existing rules
as modified by this subsection. In such event, all references herein to JAMS/Endispute shall mean AAA. Notwithstanding the foregoing, Executive and the Company each have the right to resolve any issue or dispute over intellectual property rights by
court action instead of arbitration. 
 (i) Enforcement. If any provision of this Agreement is held to be illegal, invalid or
unenforceable under present or future laws effective during the Term, such provision shall be fully severable; this Agreement shall be construed and enforced as if such illegal, invalid or unenforceable provision had never comprised a portion of
this Agreement; and the remaining provisions of this Agreement shall remain in full force and effect and shall not be affected by the illegal, invalid or unenforceable provision or by its severance from this Agreement. Furthermore, in lieu of such
illegal, invalid or unenforceable provision there shall be added automatically as part of this Agreement a provision as similar in terms to such illegal, invalid or unenforceable provision as may be possible and be legal, valid and enforceable. 

  
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 (j) Withholding. The Company shall be entitled to withhold from any amounts payable
under this Agreement any federal, state, local or foreign withholding or other taxes or charges which the Company is required to withhold. The Company shall be entitled to rely on the advice of counsel if any questions as to the amount or
requirement of withholding shall arise. 
 (k) Section 409A. 

(i) General. The intent of the Parties is that the payments and benefits under this Agreement comply with or be exempt
from Section 409A and, accordingly, to the maximum extent permitted, this Agreement shall be interpreted to be in compliance therewith. 

(ii) Separation from Service. Notwithstanding anything in this Agreement to the contrary, any compensation or benefits
payable under this Agreement that is designated under this Agreement as payable upon Executive’s termination of employment shall be payable only upon Executive’s “separation from service” with the Company within the meaning of
Section 409A (a “Separation from Service”) and, except as provided below, any such compensation or benefits described in Section 4 shall not be paid, or, in the case of installments, shall not commence
payment, until the thirtieth (30th) day following Executive’s Separation from Service (the “First Payment Date”). Any installment payments that would have been made to Executive during the thirty (30) day period
immediately following Executive’s Separation from Service but for the preceding sentence shall be paid to Executive on the First Payment Date and the remaining payments shall be made as provided in this Agreement. 

(iii) Specified Employee. Notwithstanding anything in this Agreement to the contrary, if Executive is deemed by the
Company at the time of Executive’s Separation from Service to be a “specified employee” for purposes of Section 409A, to the extent delayed commencement of any portion of the benefits to which Executive is entitled under this
Agreement is required in order to avoid a prohibited distribution under Section 409A, such portion of Executive’s benefits shall not be provided to Executive prior to the earlier of (i) the expiration of the six-month period measured from the date of Executive’s Separation from Service with the Company or (ii) the date of Executive’s death. Upon the first business day following the expiration of the
applicable Section 409A period, all payments deferred pursuant to the preceding sentence shall be paid in a lump sum to Executive (or Executive’s estate or beneficiaries), and any remaining payments due to Executive under this Agreement
shall be paid as otherwise provided herein. 
 (iv) Expense Reimbursements. To the extent that any reimbursements
under this Agreement are subject to Section 409A, (i) any such reimbursements payable to Executive shall be paid to Executive no later than December 31 of the year following the year in which the expense was incurred,
(ii) Executive shall submit Executive’s reimbursement request promptly following the date the expense is incurred, (iii) the amount of expenses reimbursed in one year shall not affect the amount eligible for reimbursement in any
subsequent year, other than medical expenses referred to in Section 105(b) of the Code, and (iv) Executive’s right to reimbursement under this Agreement will not be subject to liquidation or exchange for another benefit. 

(v) Installments. Executive’s right to receive any installment payments under this Agreement, including without
limitation any continuation salary payments that are payable on Company payroll dates, shall be treated as a right to receive a series of separate payments and, accordingly, each such installment payment shall at all times be considered a separate
and distinct payment as permitted under Section 409A. Except as otherwise permitted under Section 409A, no payment hereunder shall be accelerated or deferred unless such acceleration or deferral would not result in additional tax or
interest pursuant to Section 409A. 

  
 11 

 10. Executive Acknowledgement. 

Executive acknowledges that Executive has read and understands this Agreement, is fully aware of its legal effect, has not acted in reliance
upon any representations or promises made by the Company other than those contained in writing herein, and has entered into this Agreement freely based on Executive’s own judgment. 

[Signature Page Follows] 

  
 12 

 IN WITNESS WHEREOF, the Parties have executed this Agreement on the date and year first
above written. 
  

			
	SQZ BIOTECHNOLOGIES COMPANY
		
	By:	 	/s/ Armon Sharei, Ph.D.

 
			
	Name:	 	Armon Sharei, Ph.D.
	Title:	 	President and Chief Executive Officer
	
	EXECUTIVE
	
	 /s/ Lawrence Knopf

	 Lawrence Knopf

 [Signature Page to Employment Agreement] 

 EXHIBIT A 

Separation Agreement and Release 

This Separation Agreement and Release (“Agreement”) is made by and between ________________ (“Executive”)
and SQZ Biotechnologies Company (the “Company”) (collectively referred to as the “Parties” or individually referred to as a “Party”). Capitalized terms used but not defined in this Agreement shall have the
meanings set forth in the Employment Agreement (as defined below). 
 WHEREAS, the Parties have previously entered into that certain
Employment Agreement, dated as of _____, 2020 (the “Employment Agreement”) and that certain Employee Proprietary Information and Inventions Assignment Agreement, dated as of ________, 2020 (the “Restrictive Covenant
Agreement”); and 
 WHEREAS, in connection with Executive’s termination of employment with the Company or a subsidiary or
affiliate of the Company effective ________, 20__, the Parties wish to resolve any and all disputes, claims, complaints, grievances, charges, actions, petitions, and demands that Executive may have against the Company and any of the Releasees as
defined below, including, but not limited to, any and all claims arising out of or in any way related to Executive’s employment with or separation from the Company or its subsidiaries or affiliates but, for the avoidance of doubt, nothing
herein will be deemed to release any rights or remedies in connection with Executive’s ownership of vested equity securities of the Company, vested benefits or Executive’s right to indemnification by the Company or any of its affiliates
pursuant to contract or applicable law (collectively, the “Retained Claims”). 
 NOW, THEREFORE, in consideration of the
severance payments and benefits described in Section 4 of the Employment Agreement, which, pursuant to the Employment Agreement, are conditioned on Executive’s execution and non-revocation of this
Agreement, and in consideration of the mutual promises made herein, the Company and Executive hereby agree as follows: 
 1. Severance
Payments and Benefits; Salary and Benefits. The Company agrees to provide Executive with the severance payments and benefits described in Section [4(b)/4(c)] of the Employment Agreement, payable at the times set forth in, and subject to the
terms and conditions of, the Employment Agreement. In addition, to the extent not already paid, and subject to the terms and conditions of the Employment Agreement, the Company shall pay or provide to Executive all other payments or benefits
described in Section 3(c) of the Employment Agreement, subject to and in accordance with the terms thereof. 
 2. Release of
Claims. Executive agrees that, other than with respect to the Retained Claims, the foregoing consideration represents settlement in full of all outstanding obligations owed to Executive by the Company, any of its direct or indirect subsidiaries
and affiliates, and any of its or their current and former officers, directors, equityholders, managers, employees, agents, investors, attorneys, shareholders, administrators, affiliates, benefit plans, plan administrators, insurers, trustees,
divisions, and subsidiaries and predecessor and successor corporations and assigns (collectively, the “Releasees”). Executive, on Executive’s own behalf and on behalf of any of Executive’s affiliated companies or entities
and any of their respective heirs, family members, executors, agents, and assigns, other than with respect to the Retained Claims, hereby and forever releases the Releasees from, and agrees not to sue concerning, or in any manner to institute,
prosecute, or pursue, any claim, complaint, charge, duty, obligation, or cause of action relating to any matters of any kind, whether presently known or unknown, suspected or unsuspected, that Executive may possess against any of the Releasees
arising from any omissions, acts, facts, or damages that have occurred up until and including the date Executive signs this Agreement, including, without limitation: 

(a) any and all claims relating to or arising from Executive’s employment or service relationship with the Company or any of its direct or
indirect subsidiaries or affiliates and the termination of that relationship; 

 (b) any and all claims relating to, or arising from, Executive’s right to purchase, or
actual purchase of any shares of stock or other equity interests of the Company or any of its affiliates, including, without limitation, any claims for fraud, misrepresentation, breach of fiduciary duty, breach of duty under applicable state law,
and securities fraud under any state or federal law; 
 (c) any and all claims for wrongful discharge of employment; termination in
violation of public policy; discrimination; harassment; retaliation; breach of contract, both express and implied; breach of covenant of good faith and fair dealing, both express and implied; promissory estoppel; negligent or intentional infliction
of emotional distress; fraud; negligent or intentional misrepresentation; negligent or intentional interference with contract or prospective economic advantage; unfair business practices; defamation; libel; slander; negligence; personal injury;
assault; battery; invasion of privacy; false imprisonment; conversion; and disability benefits; 
 (d) any and all claims for violation of
any federal, state, or municipal statute, including, but not limited to, Title VII of the Civil Rights Act of 1964; the Civil Rights Act of 1991; the Rehabilitation Act of 1973; the Americans with Disabilities Act of 1990; the Equal Pay Act; the
Fair Labor Standards Act; the Fair Credit Reporting Act; the Age Discrimination in Employment Act of 1967; the Older Workers Benefit Protection Act; the Employee Retirement Income Security Act of 1974; the Worker Adjustment and Retraining
Notification Act; the Family and Medical Leave Act; and the Sarbanes-Oxley Act of 2002; 
 (e) any and all claims for violation of the
federal or any state constitution; 
 (f) any and all claims arising out of any other laws and regulations relating to employment or
employment discrimination; 
 (g) any claim for any loss, cost, damage, or expense arising out of any dispute over the non-withholding or other tax treatment of any of the proceeds received by Executive as a result of this Agreement; 

(h) any and all claims arising out of the wage and hour and wage payments laws and regulations of the state or states in which Executive has
provided service to the Company or any of its affiliates (including without limitation the Massachusetts Payment of Wages Law); and 
 (i)
any and all claims for attorneys’ fees and costs. 
 Executive agrees that the release set forth in this section shall be and remain in effect in all
respects as a complete general release as to the matters released. This release does not release claims that cannot be released as a matter of law, including, but not limited to, Executive’s right to report possible violations of federal law or
regulation to any governmental agency or entity in accordance with the provisions of and rules promulgated under Section 21F of the Securities Exchange Act of 1934 or Section 806 of the Sarbanes-Oxley Act of 2002, or any other
whistleblower protection provisions of state or federal law or 

  
 A-2 

 
regulation and any right to receive an award for information provided thereunder, Executive’s right to file a charge with or participate in a charge by the Equal Employment Opportunity
Commission, or any other local, state, or federal administrative body or government agency that is authorized to enforce or administer laws related to employment, against the Company for discrimination (with the understanding that Executive’s
release of claims herein bars Executive from recovering such monetary relief from the Company or any Releasee for any alleged discriminatory treatment), claims for unemployment compensation or any state disability insurance benefits pursuant to the
terms of applicable state law, claims to continued participation in certain of the Company’s group benefit plans pursuant to the terms and conditions of COBRA, claims to any benefit entitlements vested as the date of separation of
Executive’s employment, pursuant to written terms of any employee benefit plan of the Company or its affiliates and Executive’s right under applicable law and any Retained Claims. This release further does not release claims for breach of
Section 3(c) or Section 4 of the Employment Agreement. 
 3. Acknowledgment of Waiver of Claims under ADEA. Executive
understands and acknowledges that Executive is waiving and releasing any rights Executive may have under the Age Discrimination in Employment Act of 1967 (“ADEA”), and that this waiver and release is knowing and voluntary. Executive
understands and agrees that this waiver and release does not apply to any rights or claims that may arise under the ADEA after the date Executive signs this Agreement. Executive understands and acknowledges that the consideration given for this
waiver and release is in addition to anything of value to which Executive was already entitled. Executive further understands and acknowledges that Executive has been advised by this writing that: (a) Executive should consult with an attorney
prior to executing this Agreement; (b) Executive has 21 days within which to consider this Agreement, and the Parties agree that such time period to review this Agreement shall not be extended upon any material or immaterial changes to this
Agreement; (c) Executive has seven business days following Executive’s execution of this Agreement to revoke this Agreement pursuant to written notice to the General Counsel of the Company; (d) this Agreement shall not be effective
until after the revocation period has expired; and (e) nothing in this Agreement prevents or precludes Executive from challenging or seeking a determination in good faith of the validity of this waiver under the ADEA, nor does it impose any
condition precedent, penalties, or costs for doing so, unless specifically authorized by federal law. In the event Executive signs this Agreement and returns it to the Company in less than the 21 day period identified above, Executive hereby
acknowledges that Executive has freely and voluntarily chosen to waive the time period allotted for considering this Agreement. 
 4.
Restrictive Covenants. 
 (a) Executive acknowledges and agrees that the restrictive covenants and other post-termination obligations
set forth in the Restrictive Covenant Agreement, including without limitation Executive’s obligations relating to confidentiality, non-use and non-disclosure of
Proprietary Information (as defined in the Restrictive Covenant Agreement), non-solicitation, cooperation, and return of property, are hereby incorporated by reference and shall remain in full force and effect
pursuant to their terms to the maximum extent permitted by applicable law, except that the Parties expressly agree to modify the Restrictive Covenant Agreement by removing Section 6.1, and each subpart thereto, of the Restrictive Covenant
Agreement, which shall be of no further force or effect upon the Effective Date (as defined below). Executive represents and warrants that Executive has complied with all provisions of the Restrictive Covenant Agreement at all times through the
Effective Date. 

  
 A-3 

 (b) In consideration for the severance payments and benefits set forth in Section 1 of
this Agreement, Executive agrees for a period of one year after the Effective Date (the “Non-Competition Restricted Period”) to not, directly or indirectly, on Executive’s own behalf or
for the benefit of any other individual or entity other than the Company: (i) operate, conduct, or engage in, or prepare to operate, conduct, or engage in the Business (as defined below); (ii) own, finance, or invest in (except as the holder of
not more than one percent of the outstanding stock of a publicly held company) any Business; or (iii) participate in, render services to, or assist any person or entity that engages in or is preparing to engage in the Business in any capacity
(whether as an employee, consultant, contractor, partner, officer, director, or otherwise) (x) which involves the same or similar types of services Executive performed for the Company at any time during the last two years of Executive’s
employment with the Company or (y) in which Executive could reasonably be expected to use or disclose Proprietary Information, in each case (i), (ii) or (iii) in the Restricted Territory (as defined below). Without limiting the
Company’s ability to seek other remedies available in law or equity, if Executive violates this Section 4(b), the Non-Competition Restricted Period shall be extended by one day for each day that
Executive is in violation of such provisions, up to a maximum extension equal to the length of the Non-Competition Restricted Period, so as to give the Company the full benefit of the bargained-for length of forbearance. 
 (c) Executive’s continued compliance with the terms of the
Restrictive Covenant Agreement (as modified in Section 4(a) above) and the noncompetition obligations set forth in Section 4(b) above (collectively, the “Restrictive Covenants”) is a material condition to receipt of the
severance payments and benefits set forth in Section 1 of this Agreement. In the event Executive breaches any part of such Restrictive Covenants, then, in addition to any remedies and enforcement mechanisms set forth in the Restrictive Covenant
Agreement, the Employment Agreement and this Agreement, and any other remedies available to the Company (including equitable and injunctive remedies), Executive shall forfeit any additional consideration owing and shall be obligated to promptly
return to the Company (within fifteen (15) business days of any breach) the full gross amount of all severance payments and benefits provided. 

(d) If any provision of the Restrictive Covenants shall be determined to be unenforceable by any court of competent jurisdiction or arbitrator
by reason of its extending for too great a period of time or over too large a geographic area or over too great a range of activities, it shall be interpreted to extend only over the maximum period of time, geographic area or range of activities as
to which it may be enforceable. 
 (e) As used in this Agreement: 

(i) The term “Business” means any business or part thereof that develops, manufactures, markets, licenses, sells or provides
any product or service that competes with any product or service developed, manufactured, marketed, licensed, sold or provided, or planned to be developed, manufactured, marketed, licensed, sold or provided, by the Company, in each case at any time
during Executive’s employment or engagement with the Company. 
 (ii) The term “Restricted Territory” means each
city, county, state, territory and country in which (i) Executive provided services or had a material presence or influence at any time during the last two years of Executive’s employment or engagement with the Company or (ii) the
Company is engaged in or has plans to engage in the Business as of the termination of Executive’s employment or engagement with the Company. 

5. Severability. In the event that any provision or any portion of any provision hereof or any surviving agreement made a part hereof
becomes or is declared by a court of competent jurisdiction or arbitrator to be illegal, unenforceable, or void, this Agreement shall continue in full force and effect without said provision or portion of provision. 

  
 A-4 

 6. No Oral Modification. This Agreement may only be amended in a writing signed by
Executive and a duly authorized officer of the Company. 
 7. Governing Law; Dispute Resolution. This Agreement shall be subject to
the provisions of Sections 9(a), 9(c), and 9(h) of the Employment Agreement. 
 8. Effective Date. Executive has seven business days
after Executive signs this Agreement to revoke it and this Agreement will become effective on the day immediately following the seventh business day after Executive signed this Agreement (the “Effective Date”). For the avoidance of
doubt, if Executive revokes this Agreement as provided herein, the Parties’ modification to the Restrictive Covenant Agreement set forth in Section 4(a) above shall be void and of no effect and, unless the Company has elected or elects in
writing to expressly waive Executive’s noncompetition obligations set forth in Section 6.1(a) of the Restrictive Covenant Agreement as provided in Section 6.6 of the Restrictive Covenant Agreement, the Restrictive Covenant Agreement,
including without limitation Section 6.1 of the Restrictive Covenant Agreement, shall remain in full force and effect. 
 9.
Voluntary Execution of Agreement. Executive understands and agrees that Executive executed this Agreement voluntarily, without any duress or undue influence on the part or behalf of the Company or any third party, with the full intent of
releasing all of Executive’s claims against the Company and any of the other Releasees. Executive acknowledges that: (a) Executive has read this Agreement; (b) Executive has not relied upon any representations or statements made by
the Company that are not specifically set forth in this Agreement; (c) Executive has been represented in the preparation, negotiation, and execution of this Agreement by legal counsel of Executive’s own choice or has elected not to retain
legal counsel; (d) Executive understands the terms and consequences of this Agreement and of the releases it contains; and (e) Executive is fully aware of the legal and binding effect of this Agreement. 

IN WITNESS WHEREOF, the Parties have executed this Agreement on the respective dates set forth below. 

 

									
		 		 		 	EXECUTIVE
				
	 Dated:
	 	 	 		 	 
				
		 		 		 	SQZ BIOTECHNOLOGIES COMPANY

									
					
	 Dated:
	 	 	 		 	By:	 	 
		 		 		 		 	Name:
		 		 		 		 	Title:
		 		 		 		 	

  
 A-5 

 EXHIBIT B 

Restrictive Covenant Agreement 

[attached]EX-10.16

 Exhibit 10.16 

Employment Agreement 

This Employment Agreement (this “Agreement”), dated as of October 29, 2020, is made by and between SQZ Biotechnologies
Company, a Delaware corporation (together with any successor thereto, the “Company”), and Micah Zajic (“Executive”) (collectively referred to herein as the “Parties” or individually referred to as a
“Party”), and will become effective, if at all, upon the date of the Company’s initial public offering of stock (“IPO”) pursuant to an effective registration statement filed under the Securities Act of 1933, as
amended (the “Effective Date”). 
 RECITALS 

 

	A.	 It is the desire of the Company to assure itself of the services of Executive as of the Effective Date and
thereafter by entering into this Agreement. 

  

	B.	 Executive and the Company mutually desire that Executive provide services to the Company on the terms herein
provided. 

 AGREEMENT 

NOW, THEREFORE, in consideration of the foregoing and of the respective covenants and agreements set forth below, the Parties hereto agree as
follows: 
 1. Employment. 
 (a)
General. Effective on the Effective Date, the Company shall employ Executive, and Executive shall be employed by the Company, for the period and in the positions set forth in this Section 1, and subject to the other
terms and conditions herein provided; provided, however, that this Agreement is expressly conditioned upon the IPO closing before March 31, 2021 and will be null and void if this condition is not satisfied. 

(b) At-Will Employment. The Company and Executive acknowledge that Executive’s employment
is and shall continue to be at-will, as defined under applicable law, and that Executive’s employment with the Company may be terminated by either Party at any time for any or no reason (subject to the
notice requirements of Section 3(b)). This “at-will” nature of Executive’s employment shall remain unchanged during Executive’s tenure as an employee and may not
be changed, except in an express writing signed by Executive and a duly authorized officer of the Company. If Executive’s employment terminates for any reason, Executive shall not be entitled to any payments, benefits, damages, award or
compensation other than as provided in this Agreement or otherwise agreed to in writing by the Company or as provided by applicable law. The term of this Agreement (the “Term”) shall commence on the Effective Date and end on the
date this Agreement is terminated under Section 3. 
 (c) Positions and Duties. During the Term, Executive
shall serve as Chief Business Officer of the Company, with such responsibilities, duties and authority normally associated with such position and as may from time to time be assigned to Executive by the Chief Executive Officer of the Company.
Executive shall devote substantially all of Executive’s working time and efforts to the business and affairs of the Company (which shall include service to its affiliates, if applicable) and shall not engage in outside business activities
(including serving on outside boards or committees) without the consent of the Board of Directors of the Company or an authorized committee of the Board (in either case, the “Board”), provided that Executive shall be permitted to
(i) manage Executive’s personal, financial and legal affairs, (ii) participate in trade associations, and (iii) serve on the board of directors of
not-for-profit or tax-

 
exempt charitable organizations, in each case, subject to compliance with this Agreement and provided that such activities do not materially interfere with Executive’s performance of
Executive’s duties and responsibilities hereunder. Executive agrees to observe and comply with the rules and policies of the Company as adopted by the Company from time to time, in each case, as amended from time to time, and as delivered or
made available to Executive (each, a “Policy”). 
 2. Compensation and Related Matters. 

(a) Annual Base Salary. During the Term, Executive shall receive a base salary at a rate of $370,000 per annum, which shall be paid in
accordance with the customary payroll practices of the Company and shall be pro-rated for partial years of employment. Such annual base salary shall be reviewed (and may be adjusted) from time to time by the
Board (such annual base salary, as it may be adjusted from time to time, the “Annual Base Salary”). 
 (b) Annual Cash
Bonus Opportunity. During the Term, Executive will be eligible to participate in an annual incentive program established by the Board. Executive’s annual incentive compensation under such incentive program (the “Annual
Bonus”) shall be targeted at 40% of Executive’s Annual Base Salary (such target, as may be adjusted by the Board from time to time, the “Target Annual Bonus”). The Annual Bonus payable under the incentive program shall
be based on the achievement of performance goals to be determined by the Board and may in the Board’s discretion be calculated in a manner intended to reflect any mid-year changes in Annual Base Salary or
Target Annual Bonus. The payment of any Annual Bonus pursuant to the incentive program shall be subject to Executive’s continued employment with the Company through the date of payment, except as otherwise provided in
Section 4(b). 
 (c) Benefits. During the Term, Executive shall be eligible to participate in employee
benefit plans, programs and arrangements of the Company, subject to the terms and eligibility requirements thereof and as such plans, programs and arrangements may be amended or in effect from time to time. In no event shall Executive be eligible to
participate in any severance plan or program of the Company, except as set forth in Section 4 of this Agreement. 

(d) Vacation. During the Term, Executive shall be entitled to paid personal leave in accordance with the Company’s Policies. Any
vacation shall be taken at the reasonable and mutual convenience of the Company and Executive. 
 (e) Business Expenses. During the
Term, the Company shall reimburse Executive for all reasonable travel and other business expenses incurred by Executive in the performance of Executive’s duties to the Company in accordance with the Company’s expense reimbursement Policy.

 (f) Key Person Insurance. At any time during the Term, the Company shall have the right (but not the obligation) to insure the
life of Executive for the Company’s sole benefit. The Company shall have the right to determine the amount of insurance and the type of policy. Executive shall reasonably cooperate with the Company in obtaining such insurance by submitting to
physical examinations, by supplying all information reasonably required by any insurance carrier, and by executing all necessary documents reasonably required by any insurance carrier, provided that any information provided to an insurance company
or broker shall not be provided to the Company without the prior written authorization of Executive. Executive shall incur no financial obligation by executing any required document, and shall have no interest in any such policy. 

  
 2 

 3. Termination. 

Executive’s employment hereunder and the Term may be terminated by the Company or Executive, as applicable, without any breach of this
Agreement under the following circumstances and the Term will end on the Date of Termination: 
 (a) Circumstances. 

(i) Death. Executive’s employment hereunder shall terminate upon Executive’s death. 

(ii) Disability. If Executive has incurred a Disability, as defined below, the Company may terminate Executive’s
employment. 
 (iii) Termination for Cause. The Company may terminate Executive’s employment for Cause, as
defined below. 
 (iv) Termination without Cause. The Company may terminate Executive’s employment without Cause.

 (v) Resignation from the Company with Good Reason. Executive may resign Executive’s employment with the
Company with Good Reason, as defined below. 
 (vi) Resignation from the Company without Good Reason. Executive may
resign Executive’s employment with the Company for any reason other than Good Reason or for no reason. 
 (b) Notice of
Termination. Any termination of Executive’s employment by the Company or by Executive under this Section 3 (other than termination pursuant to Section 3(a)(i)) shall be communicated by a
written notice to the other Party hereto (i) indicating the specific termination provision in this Agreement relied upon, (ii) setting forth in reasonable detail the facts and circumstances claimed to provide a basis for termination of
Executive’s employment under the provision so indicated, if applicable, and (iii) specifying a Date of Termination which, if submitted by Executive, shall be at least thirty (30) days following the date of such notice (a
“Notice of Termination”); provided, however, that in the event that Executive delivers a Notice of Termination to the Company, the Company may, in its sole discretion, change the Date of Termination to any date that occurs
following the date of the Company’s receipt of such Notice of Termination and is prior to the date specified in such Notice of Termination, but the termination will still be considered a resignation by Executive. A Notice of Termination
submitted by the Company may provide for a Date of Termination on the date Executive receives the Notice of Termination, or any date thereafter elected by the Company. The failure by either Party to set forth in the Notice of Termination any fact or
circumstance which contributes to a showing of Cause or Good Reason shall not waive any right of the Party hereunder or preclude the Party from asserting such fact or circumstance in enforcing the Party’s rights hereunder. 

(c) Company Obligations upon Termination. Upon termination of Executive’s employment pursuant to any of the circumstances listed
in this Section 3, Executive (or Executive’s estate) shall be entitled to receive the sum of: (i) the portion of Executive’s Annual Base Salary earned through the Date of Termination, but not yet paid to
Executive; (ii) any expense reimbursements owed to Executive pursuant to Section 2(e); and (iii) any amount accrued and arising from Executive’s participation in, or benefits accrued under any employee
benefit plans, programs or arrangements, which amounts shall be 

  
 3 

 
payable in accordance with the terms and conditions of such employee benefit plans, programs or arrangements (collectively, the “Company Arrangements”). Except as otherwise
expressly required by law (e.g., COBRA) or applicable plan, program, or arrangement or as specifically provided herein, all of Executive’s rights to salary, severance, benefits, bonuses and other compensatory amounts hereunder (if any)
shall cease upon the termination of Executive’s employment hereunder. In the event that Executive’s employment is terminated by the Company for any reason, Executive’s sole and exclusive remedy shall be to receive the payments and
benefits described in this Section 3(c) or Section 4, as applicable. 
 (d) Deemed
Resignation. Upon termination of Executive’s employment for any reason, Executive shall be deemed to have resigned from all offices and directorships, if any, then held with the Company or any of its subsidiaries. 

4. Severance Payments. 
 (a)
Termination for Cause, or Termination Upon Death, Disability or Resignation from the Company Without Good Reason. If Executive’s employment shall terminate as a result of Executive’s death pursuant to
Section 3(a)(i) or Disability pursuant to Section 3(a)(ii), pursuant to Section 3(a)(iii) for Cause, or pursuant to Section 3(a)(vi) for
Executive’s resignation from the Company without Good Reason, then Executive shall not be entitled to any severance payments or benefits, except as provided in Section 3(c). 

(b) Termination without Cause, or Resignation from the Company with Good Reason. Subject to Section 4(c), if
Executive’s employment terminates without Cause pursuant to Section 3(a)(iv), or pursuant to Section 3(a)(v) due to Executive’s resignation with Good Reason, then except as otherwise
provided under Section 4(c) and subject to Executive signing on or before the 21st day following Executive’s Separation from Service (as defined below), and not revoking, a release of claims substantially in the form
attached as Exhibit A to this Agreement (the “Release”) and Executive’s continued compliance with Section 5, Executive shall receive, in addition to payments and benefits set forth in
Section 3(c), the following: 
 (i) an amount in cash equal to 0.75 times the Annual Base Salary,
payable in the form of salary continuation in regular installments over the 9 month period following the date of Executive’s Separation from Service (the “Severance Period”) in accordance with the Company’s normal payroll
practices; 
 (ii) to the extent unpaid as of the Date of Termination, an amount of cash equal to any Annual Bonus earned by
Executive for the Company’s fiscal year prior to the fiscal year in which the Date of Termination occurs, as determined by the Board in its discretion based upon actual performance achieved, which Annual Bonus, if any, shall be paid to
Executive in the fiscal year in which the Date of Termination occurs when bonuses for such prior fiscal year are paid in the ordinary course to actively employed senior executives of the Company; 

(iii) an amount in cash equal to the Target Annual Bonus multiplied by a fraction (A) the numerator of which is the number
of days the Executive was employed by the Company in the Company’s fiscal year in which the Executive’s termination of employment occurs, over (B) 365, payable in a lump sum on the Company’s first ordinary payroll date that occurs
after the Date of Termination; and 

  
 4 

 (iv) if Executive timely elects to receive continued medical, dental or
vision coverage under one or more of the Company’s group medical, dental or vision plans pursuant to the Consolidated Omnibus Budget Reconciliation Act of 1985, as amended (“COBRA”), then the Company shall directly pay, or
reimburse Executive for, the COBRA premiums for Executive and Executive’s covered dependents under such plans, less the amount Executive would have had to pay to receive such coverage as an active employee based on the cost sharing levels in
effect on the Date of Termination, during the period commencing on Executive’s Separation from Service and ending upon the earliest of (A) the last day of the Severance Period, (B) the date that Executive and/or Executive’s
covered dependents become no longer eligible for COBRA or (C) the date Executive becomes eligible to receive medical, dental or vision coverage, as applicable, from a subsequent employer (and Executive agrees to promptly notify the Company of
such eligibility) (the “COBRA Continuation Period”). Notwithstanding the foregoing, if the Company determines it cannot provide the foregoing benefit without potentially violating applicable law (including, without limitation,
Section 2716 of the Public Health Service Act) or incurring an excise tax, the Company shall in lieu thereof provide to Executive a taxable monthly payment in an amount equal to the monthly COBRA premium that Executive would be required to pay
to continue Executive’s and Executive’s covered dependents’ group health coverage in effect on the Date of Termination (which amount shall be based on the premium for the first month of COBRA coverage), less the amount Executive would
have had to pay to receive group health coverage as an active employee for Executive and his or her covered dependents based on the cost sharing levels in effect on the Date of Termination, which payments shall continue for the remainder of the
COBRA Continuation Period. 
 (c) Change in Control. In lieu of the payments and benefits set forth in
Section 4(b), in the event Executive’s employment terminates without Cause pursuant to Section 3(a)(iv), or pursuant to Section 3(a)(v) due to Executive’s
resignation with Good Reason, in either case, during the three (3) month period prior to the date of a Change in Control or on or within eighteen (18) months following the date of a Change in Control, subject to Executive signing on or
before the 21st day following Executive’s Separation from Service, and not revoking, the Release and Executive’s continued compliance with Section 5, Executive shall receive, in addition to the payments and
benefits set forth in Section 3(c), the following: 
 (i) an amount in cash equal to 1.0 times the
Annual Base Salary, payable in equal installments over the 12 month period following the date of Executive’s Separation from Service (the “CIC Severance Period”) in accordance with the Company’s normal payroll practices;

 (ii) the payment set forth in Section 4(b)(ii); 

(iii) the payment set forth in Section 4(b)(iii); 

(iv) the benefits set forth in Section 4(b)(iv), provided that for this purpose, the “Severance
Period” will mean the CIC Severance Period; 
 (v) an amount in cash equal to 1.0 times the Target Annual Bonus, payable
in a lump sum on the Company’s first ordinary payroll date that occurs after the later of the Change in Control or Date of Termination; and 

(vi) all unvested equity or equity-based awards held by Executive under any Company equity compensation plans that vest solely
based on continued employment or service shall immediately become 100% vested (and if the Date of Termination precedes the Change in Control, all such unvested awards shall remain outstanding and eligible to vest in accordance with this
Section 4(c)(vi) if a Change Control occurs within three (3) months after the Date of Termination, provided that in no event will any such award remain outstanding beyond the final expiration date of the award set
forth in the documents governing such award), with any other equity or equity-based awards being governed by the terms of the applicable award agreement. 

  
 5 

 (d) Survival. Notwithstanding anything to the contrary in this Agreement, the
provisions of Sections 5 through 9 will survive the termination of Executive’s employment and the termination of the Term. 
 5.
Restrictive Covenants. As a condition to the effectiveness of this Agreement, Executive will have executed and delivered to the Company no later than contemporaneously herewith the Employee Proprietary Information and Inventions
Assignment Agreement attached as Exhibit B (the “Restrictive Covenant Agreement”). Executive agrees to abide by the terms of the Restrictive Covenant Agreement, which are hereby incorporated by reference into this Agreement.
Executive acknowledges that the provisions of the Restrictive Covenant Agreement will survive the termination of Executive’s employment and the termination of the Term for the periods set forth in the Restrictive Covenant Agreement. 

6. Assignment and Successors. 

The Company may assign its rights and obligations under this Agreement to any of its affiliates or to any successor to all or substantially
all of the business or the assets of the Company (by merger or otherwise), and may assign or encumber this Agreement and its rights hereunder as security for indebtedness of the Company and its affiliates. This Agreement shall be binding upon and
inure to the benefit of the Company, Executive and their respective successors, assigns, personal and legal representatives, executors, administrators, heirs, distributees, devisees, and legatees, as applicable. None of Executive’s rights or
obligations may be assigned or transferred by Executive, other than Executive’s rights to payments hereunder, which may be transferred only by will or operation of law. Notwithstanding the foregoing, Executive shall be entitled, to the extent
permitted under applicable law and applicable Company Arrangements, to select and change a beneficiary or beneficiaries to receive compensation hereunder following Executive’s death by giving written notice thereof to the Company. 

7. Certain Definitions. 
 (a)
Cause. The Company shall have “Cause” to terminate Executive’s employment hereunder upon: 
 (i) The
Chief Executive Officer’s or the Board’s reasonable, good faith determination that Executive has refused to (A) substantially perform the duties associated with Executive’s position with the Company or (B) carry out the
reasonable and lawful instructions of the Chief Executive Officer or the Board concerning duties or actions consistent with the Executive’s position with the Company; 

(ii) Executive’s breach of a material provision of this Agreement that, to the extent capable of cure, has remained
uncured for a period of thirty (30) days following written notice from the Company; 
 (iii) Executive’s
conviction, plea of no contest, plea of nolo contendere, or imposition of unadjudicated probation for any felony or crime involving moral turpitude; 

(iv) Executive’s unlawful use (including being under the influence) or possession of illegal drugs on the Company’s
(or any of its affiliate’s) premises or while performing Executive’s duties and responsibilities under this Agreement; or 

  
 6 

 (v) Executive’s commission of any act of fraud, embezzlement,
misappropriation, willful misconduct, or breach of fiduciary duty against the Company or any of its affiliates. 
 (b) Change in
Control. “Change in Control” shall have the meaning set forth in the SQZ Biotechnologies Company 2020 Incentive Award Plan, as in effect on the Effective Date. 

(c) Code. “Code” shall mean the Internal Revenue Code of 1986, as amended, and the regulations and guidance promulgated
thereunder. 
 (d) Date of Termination. “Date of Termination” shall mean (i) if Executive’s employment is
terminated by Executive’s death, the date of Executive’s death; or (ii) if Executive’s employment is terminated pursuant to Section 3(a)(ii) – (vi) either the date indicated in the Notice of
Termination or the date specified by the Company pursuant to Section 3(b), whichever is earlier. 
 (e)
Disability. “Disability” shall mean, at any time the Company or any of its affiliates sponsors a long-term disability plan for the Company’s employees, “disability” as defined in such long-term disability plan for the
purpose of determining a participant’s eligibility for benefits, provided, however, if the long-term disability plan contains multiple definitions of disability, “Disability” shall refer to that definition of disability which,
if Executive qualified for such disability benefits, would provide coverage for the longest period of time. The determination of whether Executive has a Disability shall be made by the person or persons required to make disability determinations
under the long-term disability plan. At any time the Company does not sponsor a long-term disability plan for its employees, “Disability” shall mean Executive’s inability to perform, with or without reasonable accommodation, the
essential functions of Executive’s positions hereunder for a total of three months during any six-month period as a result of incapacity due to mental or physical illness as determined by a physician
selected by the Company or its insurers and acceptable to Executive or Executive’s legal representative, with such agreement as to acceptability not to be unreasonably withheld or delayed. Any refusal by Executive to submit to a medical
examination for the purpose of determining Disability shall be deemed to constitute conclusive evidence of Executive’s Disability. 

(f) Good Reason. For the sole purpose of determining Executive’s right to severance payments and benefits as described above,
Executive’s resignation will be with “Good Reason” if Executive resigns within ninety (90) days after any of the following events, unless Executive consents in writing to the applicable event: (i) a reduction in
Executive’s Annual Base Salary or Target Annual Bonus (if any), other than a reduction in Annual Base Salary of less than 10% that is implemented in connection with a contemporaneous reduction in annual base salaries affecting other senior
executives of the Company, (ii) a material decrease in Executive’s authority or areas of responsibility as are commensurate with Executive’s title or position with the Company, including Executive ceasing to report directly to the
chief executive officer of the Company’s ultimate parent company following a Change in Control (or of the Company if there is no such parent entity), (iii) the relocation of Executive’s primary office to a location more than fifty
(50) miles from the Executive’s primary office as of the date of this Agreement or (iv) the Company’s breach of a material provision of this Agreement. Notwithstanding the foregoing, no Good Reason will have occurred unless and
until: (a) Executive has provided the Company, within sixty (60) days of Executive’s knowledge of the occurrence of the facts and circumstances underlying the Good Reason event, written notice stating with specificity the applicable
facts and circumstances underlying such finding of Good Reason; (b) the Company has had an opportunity to cure the same within thirty (30) days after the receipt of such notice; and (c) the Company shall have failed to so cure within
such period. 

  
 7 

 8. Parachute Payments. 

(a) Notwithstanding any other provisions of this Agreement or any Company equity plan or agreement, in the event that any payment or benefit
by the Company or otherwise to or for the benefit of Executive, whether paid or payable or distributed or distributable pursuant to the terms of this Agreement or otherwise (all such payments and benefits, including the payments and benefits under
Section 4 hereof, being hereinafter referred to as the “Total Payments”), would be subject (in whole or in part) to the excise tax imposed by Section 4999 of the Code (the “Excise
Tax”), then the Total Payments shall be reduced (in the order provided in Section 8(b)) to the minimum extent necessary to avoid the imposition of the Excise Tax on the Total Payments, but only if (i) the net
amount of such Total Payments, as so reduced (and after subtracting the net amount of federal, state and local income and employment taxes on such reduced Total Payments and after taking into account the phase out of itemized deductions and personal
exemptions attributable to such reduced Total Payments), is greater than or equal to (ii) the net amount of such Total Payments without such reduction (but after subtracting the net amount of federal, state and local income and employment taxes
on such Total Payments and the amount of the Excise Tax to which Executive would be subject in respect of such unreduced Total Payments and after taking into account the phase out of itemized deductions and personal exemptions attributable to such
unreduced Total Payments). 
 (b) The Total Payments shall be reduced in the following order: (i) reduction on a pro rata basis of any
cash severance payments that are exempt from Section 409A of the Code (“Section 409A”), (ii) reduction on a pro rata basis of any non-cash severance payments or
benefits that are exempt from Section 409A, (iii) reduction on a pro rata basis of any other payments or benefits that are exempt from Section 409A, and (iv) reduction of any payments or benefits otherwise payable to Executive on
a pro rata basis or such other manner that complies with Section 409A; provided, in case of clauses (ii), (iii) and (to the extent permissible under Section 409A) (iv), that reduction of any payments attributable to the acceleration of
vesting of Company equity awards shall be first applied to Company equity awards that would otherwise vest last in time. 
 (c) All
determinations regarding the application of this Section 8 shall be made by an accounting firm or consulting group with experience in performing calculations regarding the applicability of Section 280G of the Code and
the Excise Tax selected by the Company (the “Independent Advisors”). For purposes of determinations, no portion of the Total Payments shall be taken into account which, in the opinion of the Independent Advisors, (i) does not
constitute a “parachute payment” within the meaning of Section 280G(b)(2) of the Code (including by reason of Section 280G(b)(4)(A) of the Code) or (ii) constitutes reasonable compensation for services actually rendered,
within the meaning of Section 280G(b)(4)(B) of the Code, in excess of the “base amount” (as defined in Section 280G(b)(3) of the Code) allocable to such reasonable compensation. The costs of obtaining such determination and all
related fees and expenses (including related fees and expenses incurred in any later audit) shall be borne by the Company. 
 (d) In the
event it is later determined that a greater reduction in the Total Payments should have been made to implement the objective and intent of this Section 8, the excess amount shall be returned promptly by Executive to the
Company. 

  
 8 

 9. Miscellaneous Provisions. 

(a) Governing Law. This Agreement shall be governed, construed, interpreted and enforced in accordance with its express terms, and
otherwise in accordance with the substantive laws of the Commonwealth of Massachusetts without reference to the principles of conflicts of law of the Commonwealth of Massachusetts or any other jurisdiction that would result in the application of the
laws of a jurisdiction other than the Commonwealth of Massachusetts, and where applicable, the laws of the United States. 
 (b)
Validity. The invalidity or unenforceability of any provision or provisions of this Agreement shall not affect the validity or enforceability of any other provision of this Agreement, which shall remain in full force and effect. 

(c) Notices. Any notice, request, claim, demand, document and other communication hereunder to any Party shall be effective upon
receipt (or refusal of receipt) and shall be in writing and delivered personally or sent by facsimile or certified or registered mail, postage prepaid, as follows: 

(i) If to the Company, to the General Counsel of the Company at the Company’s headquarters, 

(ii) If to Executive, to the last address that the Company has in its personnel records for Executive, or 

(iii) At any other address as any Party shall have specified by notice in writing to the other Party. 

(d) Counterparts. This Agreement may be executed in several counterparts, each of which shall be deemed to be an original, but all of
which together will constitute one and the same Agreement. Signatures delivered by facsimile or PDF shall be deemed effective for all purposes. 

(e) Entire Agreement. The terms of this Agreement, and the Restrictive Covenant Agreement incorporated herein by reference as set forth
in Section 5, are intended by the Parties to be the final expression of their agreement with respect to the subject matter hereof and supersede all prior understandings and agreements, whether written or oral, including any
prior employment offer letter or employment agreement between Executive and the Company. The Parties further intend that this Agreement shall constitute the complete and exclusive statement of their terms and that no extrinsic evidence whatsoever
may be introduced in any judicial, administrative, or other legal proceeding to vary the terms of this Agreement. 
 (f) Amendments;
Waivers. This Agreement may not be modified, amended, or terminated except by an instrument in writing, signed by Executive and a duly authorized officer of Company. By an instrument in writing similarly executed, Executive or a duly authorized
officer of the Company may waive compliance by the other Party with any specifically identified provision of this Agreement that such other Party was or is obligated to comply with or perform; provided, however, that such waiver shall
not operate as a waiver of, or estoppel with respect to, any other or subsequent failure. No failure to exercise and no delay in exercising any right, remedy, or power hereunder will preclude any other or further exercise of any other right, remedy,
or power provided herein or by law or in equity. 

  
 9 

 (g) Construction. This Agreement shall be deemed drafted equally by both the Parties.
Its language shall be construed as a whole and according to its fair meaning. Any presumption or principle that the language is to be construed against any Party shall not apply. The headings in this Agreement are only for convenience and are not
intended to affect construction or interpretation. Any references to paragraphs, subparagraphs, sections or subsections are to those parts of this Agreement, unless the context clearly indicates to the contrary. Also, unless the context clearly
indicates to the contrary, (i) the plural includes the singular and the singular includes the plural; (ii) “and” and “or” are each used both conjunctively and disjunctively; (iii) “any,” “all,”
“each,” or “every” means “any and all,” and “each and every”; (iv) “includes” and “including” are each “without limitation”; (v) “herein,” “hereof,”
“hereunder” and other similar compounds of the word “here” refer to the entire Agreement and not to any particular paragraph, subparagraph, section or subsection; and (vi) all pronouns and any variations thereof shall be
deemed to refer to the masculine, feminine, neuter, singular or plural as the identity of the entities or persons referred to may require. 

(h) Arbitration. Any controversy, claim or dispute arising out of or relating to this Agreement, shall be settled solely and
exclusively by a binding arbitration process administered by JAMS/Endispute in Boston, Massachusetts. Such arbitration shall be conducted in accordance with the then-existing JAMS/Endispute Rules of Practice and Procedure, with the following
exceptions if in conflict: (i) one arbitrator who is a retired judge shall be chosen by JAMS/Endispute; (ii) each Party to the arbitration will pay one-half of the expenses and fees of the
arbitrator, together with other expenses of the arbitration incurred or approved by the arbitrator; and (iii) arbitration may proceed in the absence of any Party if written notice (pursuant to the JAMS/Endispute rules and regulations) of the
proceedings has been given to such Party. Each Party shall bear its own attorney’s fees and expenses; provided that the arbitrator may assess the prevailing Party’s fees and costs against the
non-prevailing Party as part of the arbitrator’s award. The Parties agree to abide by all decisions and awards rendered in such proceedings. Such decisions and awards rendered by the arbitrator shall be
final and conclusive. All such controversies, claims or disputes shall be settled in this manner in lieu of any action at law or equity; provided, however, that nothing in this subsection shall be construed as precluding the bringing of an action
for injunctive relief or specific performance as provided in this Agreement or the Restrictive Covenant Agreement. This dispute resolution process and any arbitration hereunder shall be confidential and neither any Party nor the neutral arbitrator
shall disclose the existence, contents or results of such process without the prior written consent of all Parties, except where necessary or compelled in a court to enforce this arbitration provision or an award from such arbitration or otherwise
in a legal proceeding. If JAMS/Endispute no longer exists or is otherwise unavailable, the Parties agree that the American Arbitration Association (“AAA”) shall administer the arbitration in accordance with its then-existing rules
as modified by this subsection. In such event, all references herein to JAMS/Endispute shall mean AAA. Notwithstanding the foregoing, Executive and the Company each have the right to resolve any issue or dispute over intellectual property rights by
court action instead of arbitration. 
 (i) Enforcement. If any provision of this Agreement is held to be illegal, invalid or
unenforceable under present or future laws effective during the Term, such provision shall be fully severable; this Agreement shall be construed and enforced as if such illegal, invalid or unenforceable provision had never comprised a portion of
this Agreement; and the remaining provisions of this Agreement shall remain in full force and effect and shall not be affected by the illegal, invalid or unenforceable provision or by its severance from this Agreement. Furthermore, in lieu of such
illegal, invalid or unenforceable provision there shall be added automatically as part of this Agreement a provision as similar in terms to such illegal, invalid or unenforceable provision as may be possible and be legal, valid and enforceable. 

  
 10 

 (j) Withholding. The Company shall be entitled to withhold from any amounts payable
under this Agreement any federal, state, local or foreign withholding or other taxes or charges which the Company is required to withhold. The Company shall be entitled to rely on the advice of counsel if any questions as to the amount or
requirement of withholding shall arise. 
 (k) Section 409A. 

(i) General. The intent of the Parties is that the payments and benefits under this Agreement comply with or be exempt
from Section 409A and, accordingly, to the maximum extent permitted, this Agreement shall be interpreted to be in compliance therewith. 

(ii) Separation from Service. Notwithstanding anything in this Agreement to the contrary, any compensation or benefits
payable under this Agreement that is designated under this Agreement as payable upon Executive’s termination of employment shall be payable only upon Executive’s “separation from service” with the Company within the meaning of
Section 409A (a “Separation from Service”) and, except as provided below, any such compensation or benefits described in Section 4 shall not be paid, or, in the case of installments, shall not commence
payment, until the thirtieth (30th) day following Executive’s Separation from Service (the “First Payment Date”). Any installment payments that would have been made to Executive during the thirty (30) day period
immediately following Executive’s Separation from Service but for the preceding sentence shall be paid to Executive on the First Payment Date and the remaining payments shall be made as provided in this Agreement. 

(iii) Specified Employee. Notwithstanding anything in this Agreement to the contrary, if Executive is deemed by the
Company at the time of Executive’s Separation from Service to be a “specified employee” for purposes of Section 409A, to the extent delayed commencement of any portion of the benefits to which Executive is entitled under this
Agreement is required in order to avoid a prohibited distribution under Section 409A, such portion of Executive’s benefits shall not be provided to Executive prior to the earlier of (i) the expiration of the six-month period measured from the date of Executive’s Separation from Service with the Company or (ii) the date of Executive’s death. Upon the first business day following the expiration of the
applicable Section 409A period, all payments deferred pursuant to the preceding sentence shall be paid in a lump sum to Executive (or Executive’s estate or beneficiaries), and any remaining payments due to Executive under this Agreement
shall be paid as otherwise provided herein. 
 (iv) Expense Reimbursements. To the extent that any reimbursements
under this Agreement are subject to Section 409A, (i) any such reimbursements payable to Executive shall be paid to Executive no later than December 31 of the year following the year in which the expense was incurred,
(ii) Executive shall submit Executive’s reimbursement request promptly following the date the expense is incurred, (iii) the amount of expenses reimbursed in one year shall not affect the amount eligible for reimbursement in any
subsequent year, other than medical expenses referred to in Section 105(b) of the Code, and (iv) Executive’s right to reimbursement under this Agreement will not be subject to liquidation or exchange for another benefit. 

(v) Installments. Executive’s right to receive any installment payments under this Agreement, including without
limitation any continuation salary payments that are payable on Company payroll dates, shall be treated as a right to receive a series of separate payments and, accordingly, each such installment payment shall at all times be considered a separate
and distinct payment as permitted under Section 409A. Except as otherwise permitted under Section 409A, no payment hereunder shall be accelerated or deferred unless such acceleration or deferral would not result in additional tax or
interest pursuant to Section 409A. 

  
 11 

 10. Executive Acknowledgement. 

Executive acknowledges that Executive has read and understands this Agreement, is fully aware of its legal effect, has not acted in reliance
upon any representations or promises made by the Company other than those contained in writing herein, and has entered into this Agreement freely based on Executive’s own judgment. 

[Signature Page Follows] 

  
 12 

 IN WITNESS WHEREOF, the Parties have executed this Agreement on the date and year first
above written. 
  

			
	SQZ BIOTECHNOLOGIES COMPANY
		
	By:	 	/s/ Armon Sharei, Ph.D.
	Name:	 	Armon Sharei, Ph.D.
	Title:	 	President and Chief Executive Officer

  

			
	EXECUTIVE
		
		 	/s/ Micah Zajic
		 	Micah Zajic

  
 [Signature Page to
Employment Agreement] 

 EXHIBIT A 

Separation Agreement and Release 

This Separation Agreement and Release (“Agreement”) is made by and between ________________ (“Executive”)
and SQZ Biotechnologies Company (the “Company”) (collectively referred to as the “Parties” or individually referred to as a “Party”). Capitalized terms used but not defined in this Agreement shall have the
meanings set forth in the Employment Agreement (as defined below). 
 WHEREAS, the Parties have previously entered into that certain
Employment Agreement, dated as of _____, 2020 (the “Employment Agreement”) and that certain Employee Proprietary Information and Inventions Assignment Agreement, dated as of ________, 2020 (the “Restrictive Covenant
Agreement”); and 
 WHEREAS, in connection with Executive’s termination of employment with the Company or a subsidiary or
affiliate of the Company effective ________, 20__, the Parties wish to resolve any and all disputes, claims, complaints, grievances, charges, actions, petitions, and demands that Executive may have against the Company and any of the Releasees as
defined below, including, but not limited to, any and all claims arising out of or in any way related to Executive’s employment with or separation from the Company or its subsidiaries or affiliates but, for the avoidance of doubt, nothing
herein will be deemed to release any rights or remedies in connection with Executive’s ownership of vested equity securities of the Company, vested benefits or Executive’s right to indemnification by the Company or any of its affiliates
pursuant to contract or applicable law (collectively, the “Retained Claims”). 
 NOW, THEREFORE, in consideration of the
severance payments and benefits described in Section 4 of the Employment Agreement, which, pursuant to the Employment Agreement, are conditioned on Executive’s execution and non-revocation of this
Agreement, and in consideration of the mutual promises made herein, the Company and Executive hereby agree as follows: 
 1. Severance
Payments and Benefits; Salary and Benefits. The Company agrees to provide Executive with the severance payments and benefits described in Section [4(b)/4(c)] of the Employment Agreement, payable at the times set forth in, and subject to the
terms and conditions of, the Employment Agreement. In addition, to the extent not already paid, and subject to the terms and conditions of the Employment Agreement, the Company shall pay or provide to Executive all other payments or benefits
described in Section 3(c) of the Employment Agreement, subject to and in accordance with the terms thereof. 
 2. Release of
Claims. Executive agrees that, other than with respect to the Retained Claims, the foregoing consideration represents settlement in full of all outstanding obligations owed to Executive by the Company, any of its direct or indirect subsidiaries
and affiliates, and any of its or their current and former officers, directors, equityholders, managers, employees, agents, investors, attorneys, shareholders, administrators, affiliates, benefit plans, plan administrators, insurers, trustees,
divisions, and subsidiaries and predecessor and successor corporations and assigns (collectively, the “Releasees”). Executive, on Executive’s own behalf and on behalf of any of Executive’s affiliated companies or entities
and any of their respective heirs, family members, executors, agents, and assigns, other than with respect to the Retained Claims, hereby and forever releases the Releasees from, and agrees not to sue concerning, or in any manner to institute,
prosecute, or pursue, any claim, complaint, charge, duty, obligation, or cause of action relating to any matters of any kind, whether presently known or unknown, suspected or unsuspected, that Executive may possess against any of the Releasees
arising from any omissions, acts, facts, or damages that have occurred up until and including the date Executive signs this Agreement, including, without limitation: 

(a) any and all claims relating to or arising from Executive’s employment or service relationship with the Company or any of its direct or
indirect subsidiaries or affiliates and the termination of that relationship; 

 (b) any and all claims relating to, or arising from, Executive’s right to purchase, or
actual purchase of any shares of stock or other equity interests of the Company or any of its affiliates, including, without limitation, any claims for fraud, misrepresentation, breach of fiduciary duty, breach of duty under applicable state law,
and securities fraud under any state or federal law; 
 (c) any and all claims for wrongful discharge of employment; termination in
violation of public policy; discrimination; harassment; retaliation; breach of contract, both express and implied; breach of covenant of good faith and fair dealing, both express and implied; promissory estoppel; negligent or intentional infliction
of emotional distress; fraud; negligent or intentional misrepresentation; negligent or intentional interference with contract or prospective economic advantage; unfair business practices; defamation; libel; slander; negligence; personal injury;
assault; battery; invasion of privacy; false imprisonment; conversion; and disability benefits; 
 (d) any and all claims for violation of
any federal, state, or municipal statute, including, but not limited to, Title VII of the Civil Rights Act of 1964; the Civil Rights Act of 1991; the Rehabilitation Act of 1973; the Americans with Disabilities Act of 1990; the Equal Pay Act; the
Fair Labor Standards Act; the Fair Credit Reporting Act; the Age Discrimination in Employment Act of 1967; the Older Workers Benefit Protection Act; the Employee Retirement Income Security Act of 1974; the Worker Adjustment and Retraining
Notification Act; the Family and Medical Leave Act; and the Sarbanes-Oxley Act of 2002; 
 (e) any and all claims for violation of the
federal or any state constitution; 
 (f) any and all claims arising out of any other laws and regulations relating to employment or
employment discrimination; 
 (g) any claim for any loss, cost, damage, or expense arising out of any dispute over the non-withholding or other tax treatment of any of the proceeds received by Executive as a result of this Agreement; 

(h) any and all claims arising out of the wage and hour and wage payments laws and regulations of the state or states in which Executive has
provided service to the Company or any of its affiliates (including without limitation the Massachusetts Payment of Wages Law); and 
 (i)
any and all claims for attorneys’ fees and costs. 
 Executive agrees that the release set forth in this section shall be and remain in effect in all
respects as a complete general release as to the matters released. This release does not release claims that cannot be released as a matter of law, including, but not limited to, Executive’s right to report possible violations of federal law or
regulation to any governmental agency or entity in accordance with the provisions of and rules promulgated under Section 21F of the Securities Exchange Act of 1934 or Section 806 of the Sarbanes-Oxley Act of 2002, or any other
whistleblower protection provisions of state or federal law or 

  
 A-2 

 
regulation and any right to receive an award for information provided thereunder, Executive’s right to file a charge with or participate in a charge by the Equal Employment Opportunity
Commission, or any other local, state, or federal administrative body or government agency that is authorized to enforce or administer laws related to employment, against the Company for discrimination (with the understanding that Executive’s
release of claims herein bars Executive from recovering such monetary relief from the Company or any Releasee for any alleged discriminatory treatment), claims for unemployment compensation or any state disability insurance benefits pursuant to the
terms of applicable state law, claims to continued participation in certain of the Company’s group benefit plans pursuant to the terms and conditions of COBRA, claims to any benefit entitlements vested as the date of separation of
Executive’s employment, pursuant to written terms of any employee benefit plan of the Company or its affiliates and Executive’s right under applicable law and any Retained Claims. This release further does not release claims for breach of
Section 3(c) or Section 4 of the Employment Agreement. 
 3. Acknowledgment of Waiver of Claims under ADEA. Executive
understands and acknowledges that Executive is waiving and releasing any rights Executive may have under the Age Discrimination in Employment Act of 1967 (“ADEA”), and that this waiver and release is knowing and voluntary. Executive
understands and agrees that this waiver and release does not apply to any rights or claims that may arise under the ADEA after the date Executive signs this Agreement. Executive understands and acknowledges that the consideration given for this
waiver and release is in addition to anything of value to which Executive was already entitled. Executive further understands and acknowledges that Executive has been advised by this writing that: (a) Executive should consult with an attorney
prior to executing this Agreement; (b) Executive has 21 days within which to consider this Agreement, and the Parties agree that such time period to review this Agreement shall not be extended upon any material or immaterial changes to this
Agreement; (c) Executive has seven business days following Executive’s execution of this Agreement to revoke this Agreement pursuant to written notice to the General Counsel of the Company; (d) this Agreement shall not be effective
until after the revocation period has expired; and (e) nothing in this Agreement prevents or precludes Executive from challenging or seeking a determination in good faith of the validity of this waiver under the ADEA, nor does it impose any
condition precedent, penalties, or costs for doing so, unless specifically authorized by federal law. In the event Executive signs this Agreement and returns it to the Company in less than the 21 day period identified above, Executive hereby
acknowledges that Executive has freely and voluntarily chosen to waive the time period allotted for considering this Agreement. 
 4.
Restrictive Covenants. 
 (a) Executive acknowledges and agrees that the restrictive covenants and other post-termination obligations
set forth in the Restrictive Covenant Agreement, including without limitation Executive’s obligations relating to confidentiality, non-use and non-disclosure of
Proprietary Information (as defined in the Restrictive Covenant Agreement), non-solicitation, cooperation, and return of property, are hereby incorporated by reference and shall remain in full force and effect
pursuant to their terms to the maximum extent permitted by applicable law, except that the Parties expressly agree to modify the Restrictive Covenant Agreement by removing Section 6.1, and each subpart thereto, of the Restrictive Covenant
Agreement, which shall be of no further force or effect upon the Effective Date (as defined below). Executive represents and warrants that Executive has complied with all provisions of the Restrictive Covenant Agreement at all times through the
Effective Date. 

  
 A-3 

 (b) In consideration for the severance payments and benefits set forth in Section 1 of
this Agreement, Executive agrees for a period of one year after the Effective Date (the “Non-Competition Restricted Period”) to not, directly or indirectly, on Executive’s own behalf or
for the benefit of any other individual or entity other than the Company: (i) operate, conduct, or engage in, or prepare to operate, conduct, or engage in the Business (as defined below); (ii) own, finance, or invest in (except as the holder of
not more than one percent of the outstanding stock of a publicly held company) any Business; or (iii) participate in, render services to, or assist any person or entity that engages in or is preparing to engage in the Business in any capacity
(whether as an employee, consultant, contractor, partner, officer, director, or otherwise) (x) which involves the same or similar types of services Executive performed for the Company at any time during the last two years of Executive’s
employment with the Company or (y) in which Executive could reasonably be expected to use or disclose Proprietary Information, in each case (i), (ii) or (iii) in the Restricted Territory (as defined below). Without limiting the
Company’s ability to seek other remedies available in law or equity, if Executive violates this Section 4(b), the Non-Competition Restricted Period shall be extended by one day for each day that
Executive is in violation of such provisions, up to a maximum extension equal to the length of the Non-Competition Restricted Period, so as to give the Company the full benefit of the bargained-for length of forbearance. 
 (c) Executive’s continued compliance with the terms of the
Restrictive Covenant Agreement (as modified in Section 4(a) above) and the noncompetition obligations set forth in Section 4(b) above (collectively, the “Restrictive Covenants”) is a material condition to receipt of the
severance payments and benefits set forth in Section 1 of this Agreement. In the event Executive breaches any part of such Restrictive Covenants, then, in addition to any remedies and enforcement mechanisms set forth in the Restrictive Covenant
Agreement, the Employment Agreement and this Agreement, and any other remedies available to the Company (including equitable and injunctive remedies), Executive shall forfeit any additional consideration owing and shall be obligated to promptly
return to the Company (within fifteen (15) business days of any breach) the full gross amount of all severance payments and benefits provided. 

(d) If any provision of the Restrictive Covenants shall be determined to be unenforceable by any court of competent jurisdiction or arbitrator
by reason of its extending for too great a period of time or over too large a geographic area or over too great a range of activities, it shall be interpreted to extend only over the maximum period of time, geographic area or range of activities as
to which it may be enforceable. 
 (e) As used in this Agreement: 

(i) The term “Business” means any business or part thereof that develops, manufactures, markets, licenses, sells or provides
any product or service that competes with any product or service developed, manufactured, marketed, licensed, sold or provided, or planned to be developed, manufactured, marketed, licensed, sold or provided, by the Company, in each case at any time
during Executive’s employment or engagement with the Company. 
 (ii) The term “Restricted Territory” means each
city, county, state, territory and country in which (i) Executive provided services or had a material presence or influence at any time during the last two years of Executive’s employment or engagement with the Company or (ii) the
Company is engaged in or has plans to engage in the Business as of the termination of Executive’s employment or engagement with the Company. 

5. Severability. In the event that any provision or any portion of any provision hereof or any surviving agreement made a part hereof
becomes or is declared by a court of competent jurisdiction or arbitrator to be illegal, unenforceable, or void, this Agreement shall continue in full force and effect without said provision or portion of provision. 

  
 A-4 

 6. No Oral Modification. This Agreement may only be amended in a writing signed by
Executive and a duly authorized officer of the Company. 
 7. Governing Law; Dispute Resolution. This Agreement shall be subject to
the provisions of Sections 9(a), 9(c), and 9(h) of the Employment Agreement. 
 8. Effective Date. Executive has seven business days
after Executive signs this Agreement to revoke it and this Agreement will become effective on the day immediately following the seventh business day after Executive signed this Agreement (the “Effective Date”). For the avoidance of
doubt, if Executive revokes this Agreement as provided herein, the Parties’ modification to the Restrictive Covenant Agreement set forth in Section 4(a) above shall be void and of no effect and, unless the Company has elected or elects in
writing to expressly waive Executive’s noncompetition obligations set forth in Section 6.1(a) of the Restrictive Covenant Agreement as provided in Section 6.6 of the Restrictive Covenant Agreement, the Restrictive Covenant Agreement,
including without limitation Section 6.1 of the Restrictive Covenant Agreement, shall remain in full force and effect. 
 9.
Voluntary Execution of Agreement. Executive understands and agrees that Executive executed this Agreement voluntarily, without any duress or undue influence on the part or behalf of the Company or any third party, with the full intent of
releasing all of Executive’s claims against the Company and any of the other Releasees. Executive acknowledges that: (a) Executive has read this Agreement; (b) Executive has not relied upon any representations or statements made by
the Company that are not specifically set forth in this Agreement; (c) Executive has been represented in the preparation, negotiation, and execution of this Agreement by legal counsel of Executive’s own choice or has elected not to retain
legal counsel; (d) Executive understands the terms and consequences of this Agreement and of the releases it contains; and (e) Executive is fully aware of the legal and binding effect of this Agreement. 

IN WITNESS WHEREOF, the Parties have executed this Agreement on the respective dates set forth below. 

 

									
		 		 		 	EXECUTIVE
				
	 Dated:
	 	 	 		 	 
				
		 		 		 	SQZ BIOTECHNOLOGIES COMPANY

									
					
	 Dated:
	 	 	 		 	By:	 	 
		 		 		 		 	Name:
		 		 		 		 	Title:
		 		 		 		 	

  
 A-5 

 EXHIBIT B 

Restrictive Covenant Agreement 

[attached]

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