Document:

EX-10.16

 Exhibit 10.16 

SYNLOGIC, INC 
 2017
STOCK INCENTIVE PLAN 
  

	 	1.	DEFINITIONS. 

 Unless otherwise specified or unless the context otherwise requires, the
following terms, as used in this Synlogic, Inc. 2017 Stock Incentive Plan, have the following meanings: 
 Administrator means the
Board of Directors, unless it has delegated power to act on its behalf to the Committee, in which case the Administrator means the Committee. 

Affiliate means a corporation or other entity which, for purposes of Section 424 of the Code, is a parent or subsidiary of the
Company, direct or indirect. 
 Agreement means an agreement between the Company and a Participant delivered pursuant to the Plan and
pertaining to a Stock Right, in such form as the Administrator shall approve. 
 Board of Directors means the Board of Directors of
the Company. 
 Cause means, with respect to a Participant (a) dishonesty with respect to the Company or any Affiliate,
(b) insubordination, substantial malfeasance or non-feasance of duty, (c) unauthorized disclosure of confidential information, (d) breach by the Participant of any provision of any employment,
consulting, advisory, nondisclosure, non-competition or similar agreement between the Participant and the Company or any Affiliate, and (e) conduct substantially prejudicial to the business of the Company or any Affiliate; provided, however,
that any provision in an agreement between the Participant and the Company or an Affiliate, which contains a conflicting definition of Cause for termination and which is in effect at the time of such termination, shall supersede this definition with
respect to that Participant. The determination of the Administrator as to the existence of Cause will be conclusive on the Participant and the Company. 

Code means the United States Internal Revenue Code of 1986, as amended including any successor statute, regulation and guidance thereto.

 Committee means the committee of the Board of Directors to which the Board of Directors has delegated power to act under or
pursuant to the provisions of the Plan. 
 Common Stock means shares of the Company’s common stock, $0.0001 par value per share.

 Company means Synlogic, Inc., a Delaware corporation. 

 Consultant means any natural person who is an advisor or consultant that provides bona
fide services to the Company or its Affiliates, provided that such services are not in connection with the offer or sale of securities in a capital raising transaction, and do not directly or indirectly promote or maintain a market for the
Company’s or its Affiliates’ securities. 
 Disability or Disabled means permanent and total disability as defined in
Section 22(e)(3) of the Code. 
 Employee means any employee of the Company or of an Affiliate (including, without limitation, an
employee who is also serving as an officer or director of the Company or of an Affiliate), designated by the Administrator to be eligible to be granted one or more Stock Rights under the Plan. 

Fair Market Value of a Share of Common Stock means: 

(1) If the Common Stock is listed on a national securities exchange or traded in the over-the-counter market and sales prices
are regularly reported for the Common Stock, the closing or, if not applicable, the last price of the Common Stock on the composite tape or other comparable reporting system for the trading day on the applicable date and if such applicable date is
not a trading day, the last market trading day prior to such date; 
 (2) If the Common Stock is not traded on a national
securities exchange but is traded on the over-the-counter market, if sales prices are not regularly reported for the Common Stock for the trading day referred to in clause (1), and if bid and asked prices for the Common Stock are regularly reported,
the mean between the bid and the asked price for the Common Stock at the close of trading in the over-the-counter market for the most recent trading day on which Common Stock was traded on the applicable date and if such applicable date is not a
trading day, the last market trading day prior to such date; and 
 (3) If the Common Stock is neither listed on a national
securities exchange nor traded in the over-the-counter market, such value as the Administrator, in good faith, shall determine. 
 ISO
means an option intended to qualify as an incentive stock option under Section 422 of the Code. 
 Non-Qualified Option means an
option which is not intended to qualify as an ISO. 
 Option means an ISO or Non-Qualified
Option granted under the Plan. 
 Participant means an Employee, director or Consultant of the Company or an Affiliate to whom one or
more Stock Rights are granted under the Plan. As used herein, “Participant” shall include “Participant’s Survivors” where the context requires. 

  
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 Plan means this Synlogic, Inc. 2017 Stock Incentive Plan. 

Securities Act means the Securities Act of 1933, as amended. 

Shares means shares of the Common Stock as to which Stock Rights have been or may be granted under the Plan or any shares of capital
stock into which the Shares are changed or for which they are exchanged within the provisions of Paragraph 3 of the Plan. The Shares issued under the Plan may be authorized and unissued shares or shares held by the Company in its treasury, or
both. 
 Stock-Based Award means a grant by the Company under the Plan of an equity award or an equity based award which is not an
Option or a Stock Grant. 
 Stock Grant means a grant by the Company of Shares under the Plan. 

Stock Right means a right to Shares or the value of Shares of the Company granted pursuant to the Plan – an ISO, a Non-Qualified
Option, a Stock Grant or a Stock-Based Award. 
 Survivor means a deceased Participant’s legal representatives and/or any person
or persons who acquired the Participant’s rights to a Stock Right by will or by the laws of descent and distribution. 
  

	 	2.	PURPOSES OF THE PLAN. 

 The Plan is intended to encourage ownership of Shares by
Employees and directors of and certain Consultants to the Company and its Affiliates in order to attract and retain such people, to induce them to work for the benefit of the Company or of an Affiliate and to provide additional incentive for them to
promote the success of the Company or of an Affiliate. The Plan provides for the granting of ISOs, Non-Qualified Options, Stock Grants and Stock-Based Awards. 
  

	 	3.	SHARES SUBJECT TO THE PLAN. 

 (a) The number of Shares which may be issued from time to
time pursuant to this Plan shall be 3,214,926 of shares of Common Stock, or the equivalent of such number of Shares after the Administrator, in its sole discretion, has interpreted the effect of any stock split, stock dividend, combination,
recapitalization or similar transaction in accordance with Paragraph 24 of the Plan. 
 (b) If an Option ceases to be
“outstanding”, in whole or in part (other than by exercise), or if the Company shall reacquire at not more than its original issuance price any Shares issued pursuant to a Stock Grant or Stock-Based Award, or if any Stock Right expires or
is forfeited, cancelled, or otherwise terminated or results in any Shares not being issued, the unissued or reacquired Shares which were subject to such Stock Right shall again be available for issuance from time to time pursuant to this Plan.
Notwithstanding the foregoing, if a Stock Right is exercised, in whole or in part, by tender of Shares or if the Company or an Affiliate’s tax 

  
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withholding obligation is satisfied by withholding Shares, the number of Shares deemed to have been issued under the Plan for purposes of the limitation set forth in Paragraph 3(a) above shall be
the number of Shares that were subject to the Stock Right or portion thereof, and not the net number of Shares actually issued. However, in the case of ISOs, the foregoing provisions shall be subject to any limitations under the Code. 

 

	 	4.	ADMINISTRATION OF THE PLAN. 

 The Administrator of the Plan will be the Board of
Directors, except to the extent the Board of Directors delegates its authority to the Committee, in which case the Committee shall be the Administrator. Subject to the provisions of the Plan, the Administrator is authorized to: 

(a) Interpret the provisions of the Plan and all Stock Rights and to make all rules and determinations which it deems necessary or advisable
for the administration of the Plan; 
 (b) Determine which Employees, directors and Consultants shall be granted Stock Rights; 

(c) Determine the number of Shares for which a Stock Right or Stock Rights shall be granted; 

(d) Specify the terms and conditions upon which a Stock Right or Stock Rights may be granted; 

(e) Amend any term or condition of any outstanding Stock Right, including, without limitation, to reduce or increase the exercise price or
purchase price, accelerate the vesting schedule or extend the expiration date, provided that (i) such term or condition as amended is permitted by the Plan; (ii) any such amendment shall not impair the rights of a Participant under any
Stock Right previously granted without such Participant’s consent or in the event of death of the Participant the Participant’s Survivors; and (iii) any such amendment shall be made only after the Administrator determines whether such
amendment would cause any adverse tax consequences to the Participant, including, but not limited to, the annual vesting limitation contained in Section 422(d) of the Code and described in Paragraph 6(b)(iv) below with respect to ISOs and
pursuant to Section 409A of the Code; 
 (f) Buy out for a payment in cash or Shares, a Stock Right previously granted and/or cancel any
such Stock Right and grant in substitution therefor other Stock Rights, covering the same or a different number of Shares and having an exercise price or purchase price per share which may be lower or higher than the exercise price or purchase price
of the cancelled Stock Right, based on such terms and conditions as the Administrator shall establish and the Participant shall accept; and 

(g) Adopt any sub-plans applicable to residents of any specified jurisdiction as it deems necessary or appropriate in order to comply with or
take advantage of any tax or other laws applicable to the Company, any Affiliate or to Participants or to otherwise facilitate the administration of the Plan, which sub-plans may include additional restrictions or conditions applicable to Stock
Rights or Shares issuable pursuant to a Stock Right; 

  
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 provided, however, that all such interpretations, rules, determinations, terms and conditions shall be made and
prescribed in the context of not causing any adverse tax consequences under Section 409A of the Code and preserving the tax status under Section 422 of the Code of those Options which are designated as ISOs. Subject to the foregoing, the
interpretation and construction by the Administrator of any provisions of the Plan or of any Stock Right granted under it shall be final, unless otherwise determined by the Board of Directors, if the Administrator is the Committee. In addition, if
the Administrator is the Committee, the Board of Directors may take any action under the Plan that would otherwise be the responsibility of the Committee. 

To the extent permitted under applicable law, the Board of Directors or the Committee may allocate all or any portion of its responsibilities
and powers to any one or more of its members and may delegate all or any portion of its responsibilities and powers to any other person selected by it. The Board of Directors or the Committee may revoke any such allocation or delegation at any time.

  

	 	5.	ELIGIBILITY FOR PARTICIPATION. 

 The Administrator will, in its sole discretion, name the
Participants in the Plan; provided, however, that each Participant must be an Employee, director or Consultant of the Company or of an Affiliate at the time a Stock Right is granted, or have received a grant of a profits interest from Synlogic, LLC
as an employee of or consultant to Synlogic, LLC and be granted a Stock Right as a former employee of or consultant to Synlogic, LLC pursuant to the terms of the merger of Synlogic, LLC into the Company. Notwithstanding the foregoing, the
Administrator may authorize the grant of a Stock Right to a person not then an Employee, director or Consultant of the Company or of an Affiliate; provided, however, that the actual grant of such Stock Right shall be conditioned upon such person
becoming eligible to become a Participant at or prior to the time of the execution of the Agreement evidencing such Stock Right. ISOs may be granted only to Employees who are deemed to be residents of the United States for tax purposes.
Non-Qualified Options, Stock Grants and Stock-Based Awards may be granted to any Employee, director or Consultant of the Company or an Affiliate. The granting of any Stock Right to any individual shall neither entitle that individual to, nor
disqualify him or her from, participation in any other grant of Stock Rights or any grant under any other benefit plan established by the Company or any Affiliate for Employees, directors or Consultants. 

 

	 	6.	TERMS AND CONDITIONS OF OPTIONS. 

 Each Option shall be set forth in writing in an Option
Agreement, duly executed by the Company and, to the extent required by law or requested by the Company, by the Participant. The Administrator may provide that Options be granted subject to such terms and conditions, consistent with the terms and
conditions specifically required under this Plan, as the Administrator may deem appropriate including, without limitation, subsequent approval by the shareholders of the Company of this Plan or any amendments thereto. The Option Agreements shall be
subject to at least the following terms and conditions: 
 (a) Non-Qualified Options: Each
Option intended to be a Non-Qualified Option shall be subject to the terms and conditions which the Administrator determines to be appropriate and 

  
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in the best interest of the Company, subject to the following minimum standards for any such Non-Qualified Option: 

 

	 	(i)	Exercise Price: Each Option Agreement shall state the exercise price (per share) of the Shares covered by each Option, which exercise price shall be determined by the Administrator and shall be at least equal to
the Fair Market Value per share of the Common Stock on the date of grant of the Option. 

  

	 	(ii)	Number of Shares: Each Option Agreement shall state the number of Shares to which it pertains. 

  

	 	(iii)	Option Periods: Each Option Agreement shall state the date or dates on which it first is exercisable and the date after which it may no longer be exercised, and may provide that the Option rights accrue or become
exercisable in installments over a period of months or years, or upon the occurrence of certain conditions or the attainment of stated goals or events. 

  

	 	(iv)	Option Conditions: Exercise of any Option may be conditioned upon the Participant’s execution of a Share purchase agreement in form satisfactory to the Administrator providing for certain protections for the
Company and its other shareholders, including requirements that: 

  

	 	A.	The Participant’s or the Participant’s Survivors’ right to sell or transfer the Shares may be restricted; and 

  

	 	B.	The Participant or the Participant’s Survivors may be required to execute letters of investment intent and must also acknowledge that the Shares will bear legends noting any applicable restrictions.

  

	 	(v)	Term of Option: Each Option shall terminate not more than ten years from the date of the grant or at such earlier time as the Option Agreement may provide. 

(b) ISOs: Each Option intended to be an ISO shall be issued only to an Employee who is deemed to be a resident of the United States for
tax purposes, and shall be subject to the following terms and conditions, with such additional restrictions or changes as the Administrator determines are appropriate but not in conflict with Section 422 of the Code and relevant regulations and
rulings of the Internal Revenue Service: 
  

	 	(i)	Minimum standards: The ISO shall meet the minimum standards required of Non-Qualified Options, as described in Paragraph 6(a) above, except clause (i) thereunder. 

 

	 	(ii)	Exercise Price: Immediately before the ISO is granted, if the Participant owns, directly or by reason of the applicable attribution rules in Section 424(d) of the Code: 

  
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	 	A.	Ten percent (10%) or less of the total combined voting power of all classes of stock of the Company or an Affiliate, the exercise price per share of the Shares covered by each ISO shall not be less than one
hundred percent (100%) of the Fair Market Value per share of the Common Stock on the date of grant of the Option; or 

  

	 	B.	More than ten percent (10%) of the total combined voting power of all classes of stock of the Company or an Affiliate, the exercise price per share of the Shares covered by each ISO shall not be less than one
hundred ten percent (110%) of the Fair Market Value per share of the Common Stock on the date of grant of the Option. 

  

	 	(iii)	Term of Option: For Participants who own: 

  

	 	A.	Ten percent (10%) or less of the total combined voting power of all classes of stock of the Company or an Affiliate, each ISO shall terminate not more than ten years from the date of the grant or at such
earlier time as the Option Agreement may provide; or 

  

	 	B.	More than ten percent (10%) of the total combined voting power of all classes of stock of the Company or an Affiliate, each ISO shall terminate not more than five (5) years from the date of the grant or at
such earlier time as the Option Agreement may provide. 

  

	 	(iv)	Limitation on Yearly Exercise: The Option Agreements shall restrict the amount of ISOs which may become exercisable in any calendar year (under this or any other ISO plan of the Company or an Affiliate) so that
the aggregate Fair Market Value (determined on the date each ISO is granted) of the stock with respect to which ISOs are exercisable for the first time by the Participant in any calendar year does not exceed one hundred thousand dollars ($100,000).

  

	 	7.	TERMS AND CONDITIONS OF STOCK GRANTS. 

 Each Stock Grant to a Participant shall state the
principal terms in an Agreement duly executed by the Company and, to the extent required by law or requested by the Company, by the Participant. The Agreement shall be in a form approved by the Administrator and shall contain terms and conditions
which the Administrator determines to be appropriate and in the best interest of the Company, subject to the following minimum standards: 

(a) Each Agreement shall state the purchase price per share, if any, of the Shares covered by each Stock Grant, which purchase price shall be
determined by the Administrator but shall not be less than the minimum consideration required by the Delaware General Corporation Law, if any, on the date of the grant of the Stock Grant; 

(b) Each Agreement shall state the number of Shares to which the Stock Grant pertains; and 

  
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 (c) Each Agreement shall include the terms of any right of the Company to restrict or reacquire
the Shares subject to the Stock Grant, including the time and events upon which such rights shall accrue and the purchase price therefor, if any. 
  

	 	8.	[INTENTIONALLY OMITTED] 

  

	 	9.	EXERCISE OF OPTIONS AND ISSUE OF SHARES. 

 An Option (or any part or installment thereof)
shall be exercised by giving written notice to the Company or its designee (in a form acceptable to the Administrator, which may include electronic notice), together with provision for payment of the aggregate exercise price in accordance with this
Paragraph for the Shares as to which the Option is being exercised, and upon compliance with any other condition(s) set forth in the Option Agreement. Such notice shall be signed by the person exercising the Option (which signature may be provided
electronically in a form acceptable to the Administrator), shall state the number of Shares with respect to which the Option is being exercised and shall contain any representation required by the Plan or the Option Agreement. Payment of the
exercise price for the Shares as to which such Option is being exercised shall be made (a) in United States dollars in cash or by check, or (b) at the discretion of the Administrator, through delivery of shares of Common Stock held for at
least six months (if required to avoid negative accounting treatment) having a Fair Market Value equal as of the date of the exercise to the aggregate cash exercise price for the number of Shares as to which the Option is being exercised, or
(c) at the discretion of the Administrator, by having the Company retain from the Shares otherwise issuable upon exercise of the Option, a number of Shares having a Fair Market Value equal as of the date of exercise to the aggregate exercise
price for the number of Shares as to which the Option is being exercised, or (d) at the discretion of the Administrator (after consideration of applicable securities, tax and accounting implications), by delivery of the grantee’s personal
recourse note bearing interest payable not less than annually at no less than one hundred percent (100%) of the applicable Federal rate, as defined in Section 1274(d) of the Code, or (e) at the discretion of the Administrator, in
accordance with a cashless exercise program established with a securities brokerage firm, and approved by the Administrator, or (f) at the discretion of the Administrator, by any combination of (a), (b), (c), (d) and (e) above or
(g) at the discretion of the Administrator, by payment of such other lawful consideration as the Administrator may determine. Notwithstanding the foregoing, the Administrator shall accept only such payment on exercise of an ISO as is permitted
by Section 422 of the Code. 
 The Company shall then reasonably promptly deliver the Shares as to which such Option was exercised to
the Participant (or to the Participant’s Survivors, as the case may be). In determining what constitutes “reasonably promptly,” it is expressly understood that the issuance and delivery of the Shares may be delayed by the Company in
order to comply with any law or regulation (including, without limitation, state securities or “blue sky” laws) which requires the Company to take any action with respect to the Shares prior to their issuance. The Shares shall, upon
delivery, be fully paid, non-assessable Shares. 

  
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	 	10.	PAYMENT IN CONNECTION WITH THE ISSUANCE OF STOCK GRANTS AND STOCK-BASED AWARD AND ISSUE OF SHARES. 

Any Stock Grant or Stock-Based Award requiring payment of a purchase price for the Shares as to which such Stock Grant or Stock-Based Award is
being granted shall be made (a) in United States dollars in cash or by check, or (b) at the discretion of the Administrator, through delivery of shares of Common Stock held for at least six months (if required to avoid negative accounting
treatment) and having a Fair Market Value equal as of the date of payment to the purchase price of the Stock Grant or Stock-Based Award, or (c) at the discretion of the Administrator (after consideration of applicable securities, tax and
accounting implications), by delivery of the grantee’s personal recourse note bearing interest payable not less than annually at no less than one hundred percent (100%) of the applicable Federal rate, as defined in Section 1274(d) of
the Code, or (d) at the discretion of the Administrator, by any combination of (a), (b) and (c) above; or (e) at the discretion of the Administrator, by payment of such other lawful consideration as the Administrator may
determine. 
 The Company shall, when required by the applicable Agreement, reasonably promptly deliver the Shares as to which such Stock
Grant or Stock-Based Award was made to the Participant (or to the Participant’s Survivors, as the case may be), subject to any escrow provision set forth in the applicable Agreement. In determining what constitutes “reasonably
promptly,” it is expressly understood that the issuance and delivery of the Shares may be delayed by the Company in order to comply with any law or regulation (including, without limitation, state securities or “blue sky” laws) which
requires the Company to take any action with respect to the Shares prior to their issuance. 
  

	 	11.	RIGHTS AS A SHAREHOLDER. 

 No Participant to whom a Stock Right has been granted shall
have rights as a shareholder with respect to any Shares covered by such Stock Right except after due exercise of an Option or issuance of Shares as set forth in any Agreement, tender of the aggregate exercise or purchase price, if any, for the
Shares being purchased and registration of the Shares in the Company’s share register in the name of the Participant. 
  

	 	12.	ASSIGNABILITY AND TRANSFERABILITY OF STOCK RIGHTS. 

 By its terms, a Stock Right granted
to a Participant shall not be transferable by the Participant other than (i) by will or by the laws of descent and distribution, or (ii) as approved by the Administrator in its discretion and set forth in the applicable Agreement provided
that no Stock Right may be transferred by a Participant for value. Notwithstanding the foregoing, an ISO transferred except in compliance with clause (i) above shall no longer qualify as an ISO. The designation of a beneficiary of a Stock Right
by a Participant, with the prior approval of the Administrator and in such form as the Administrator shall prescribe, shall not be deemed a transfer prohibited by this Paragraph. Except as provided above during the Participant’s lifetime a
Stock Right shall only be exercisable by or issued to such Participant (or his or her legal representative) and shall not be assigned, pledged or hypothecated in any way (whether by operation of law or otherwise) and shall not be subject to
execution, attachment or similar process. Any attempted transfer, assignment, pledge, hypothecation or other disposition of any Stock Right or of any rights granted thereunder contrary to the provisions of this Plan, or the levy of any attachment or
similar process upon a Stock Right, shall be null and void. 

  
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	 	13.	EFFECT ON OPTIONS OF TERMINATION OF SERVICE OTHER THAN FOR CAUSE OR DEATH OR DISABILITY. 

Except as otherwise provided in a Participant’s Option Agreement, in the event of a termination of service (whether as an Employee,
director or Consultant) with the Company or an Affiliate before the Participant has exercised an Option, the following rules apply: 
 (a) A
Participant who ceases to be an Employee, director or Consultant of the Company or of an Affiliate (for any reason other than termination for Cause, Disability, or death for which events there are special rules in Paragraphs 14, 15, and 16,
respectively), may exercise any Option granted to him or her to the extent that the Option is exercisable on the date of such termination of service, but only within such term as the Administrator has designated in a Participant’s Option
Agreement. 
 (b) Except as provided in Subparagraph (c) below, or Paragraph 15 or 16, in no event may an Option intended to be an ISO
be exercised later than three months after the Participant’s termination of employment. 
 (c) The provisions of this Paragraph, and not
the provisions of Paragraph 15 or 16, shall apply to a Participant who subsequently becomes Disabled or dies after the termination of employment, director status or consultancy; provided, however, in the case of a Participant’s Disability or
death within three months after the termination of employment, director status or consultancy, the Participant or the Participant’s Survivors may exercise the Option within one year after the date of the Participant’s termination of
service, but in no event after the date of expiration of the term of the Option. 
 (d) Notwithstanding anything herein to the contrary, if
subsequent to a Participant’s termination of employment, termination of director status or termination of consultancy, but prior to the exercise of an Option, the Administrator or the Board of Directors determines that, either prior or
subsequent to the Participant’s termination, the Participant engaged in conduct which would constitute Cause, then such Participant shall forthwith cease to have any right to exercise any Option. 

(e) A Participant to whom an Option has been granted under the Plan who is absent from the Company or an Affiliate because of temporary
disability (any disability other than a Disability as defined in Paragraph 1 hereof), or who is on leave of absence for any purpose, shall not, during the period of any such absence, be deemed, by virtue of such absence alone, to have terminated
such Participant’s employment, director status or consultancy with the Company or with an Affiliate, except as the Administrator may otherwise expressly provide; provided, however, that, for ISOs, any leave of absence granted by the
Administrator of greater than ninety days, unless pursuant to a contract or statute that guarantees the right to reemployment, shall cause such ISO to become a Non-Qualified Option on the 181st
day following such leave of absence. 
 (f) Except as required by law or as set forth in a Participant’s Option Agreement, Options
granted under the Plan shall not be affected by any change of a Participant’s status within or among the Company and any Affiliates, so long as the Participant continues to be an Employee, director or Consultant of the Company or any Affiliate.

  
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	 	14.	EFFECT ON OPTIONS OF TERMINATION OF SERVICE FOR CAUSE. 

 Except as otherwise provided in
a Participant’s Option Agreement, the following rules apply if the Participant’s service (whether as an Employee, director or Consultant) with the Company or an Affiliate is terminated for Cause prior to the time that all of his or her
outstanding Options have been exercised: 
 (a) All outstanding and unexercised Options as of the time the Participant is notified his or her
service is terminated for Cause will immediately be terminated. 
 (b) Cause is not limited to events which have occurred prior to a
Participant’s termination of service, nor is it necessary that the Administrator’s finding of Cause occur prior to termination. If the Administrator determines, subsequent to a Participant’s termination of service but prior to the
exercise of an Option, that either prior or subsequent to the Participant’s termination the Participant engaged in conduct which would constitute Cause, then the right to exercise any Option is terminated. 

 

	 	15.	EFFECT ON OPTIONS OF TERMINATION OF SERVICE FOR DISABILITY. 

 Except as otherwise
provided in a Participant’s Option Agreement, 
 (a) A Participant who ceases to be an Employee, director or Consultant of the Company
or of an Affiliate by reason of Disability may exercise any Option granted to such Participant: 
  

	 	(i)	To the extent that the Option has become exercisable but has not been exercised on the date of the Participant’s termination of service due to Disability; and 

 

	 	(ii)	In the event rights to exercise the Option accrue periodically, to the extent of a pro rata portion through the date of the Participant’s termination of service due to Disability of any additional vesting rights
that would have accrued on the next vesting date had the Participant not become Disabled. The proration shall be based upon the number of days accrued in the current vesting period prior to the date of the Participant’s termination of service
due to Disability. 

 (b) A Disabled Participant may exercise the Option only within the period ending one year after the date
of the Participant’s termination of service due to Disability, notwithstanding that the Participant might have been able to exercise the Option as to some or all of the Shares on a later date if the Participant had not been terminated due to
Disability and had continued to be an Employee, director or Consultant or, if earlier, within the originally prescribed term of the Option. 

  
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 (c) The Administrator shall make the determination both of whether Disability has occurred and
the date of its occurrence (unless a procedure for such determination is set forth in another agreement between the Company and such Participant, in which case such procedure shall be used for such determination). If requested, the Participant shall
be examined by a physician selected or approved by the Administrator, the cost of which examination shall be paid for by the Company. 
  

	 	16.	EFFECT ON OPTIONS OF DEATH WHILE AN EMPLOYEE, DIRECTOR OR CONSULTANT. 

 Except as
otherwise provided in a Participant’s Option Agreement, 
 (a) In the event of the death of a Participant while the Participant is an
Employee, director or Consultant of the Company or of an Affiliate, such Option may be exercised by the Participant’s Survivors: 
  

	 	(i)	To the extent that the Option has become exercisable but has not been exercised on the date of death; and 

  

	 	(ii)	In the event rights to exercise the Option accrue periodically, to the extent of a pro rata portion through the date of death of any additional vesting rights that would have accrued on the next vesting date had the
Participant not died. The proration shall be based upon the number of days accrued in the current vesting period prior to the Participant’s date of death. 

(b) If the Participant’s Survivors wish to exercise the Option, they must take all necessary steps to exercise the Option within one year
after the date of death of such Participant, notwithstanding that the decedent might have been able to exercise the Option as to some or all of the Shares on a later date if he or she had not died and had continued to be an Employee, director or
Consultant or, if earlier, within the originally prescribed term of the Option. 
  

	 	17.	EFFECT OF TERMINATION OF SERVICE ON UNACCEPTED STOCK GRANTS AND STOCK-BASED AWARDS. 

 In
the event of a termination of service (whether as an Employee, director or Consultant) with the Company or an Affiliate for any reason before the Participant has accepted a Stock Grant or a Stock-Based Award and paid the purchase price, if required
at the time, such grant shall terminate. 
 For purposes of this Paragraph 17 and Paragraph 18 below, a Participant to whom a Stock Grant or
a Stock-Based Award has been issued under the Plan who is absent from work with the Company or with an Affiliate because of temporary disability (any disability other than a Disability as defined in Paragraph 1 hereof), or who is on leave of absence
for any purpose, shall not, during the period of any such absence, be deemed, by virtue of such absence alone, to have terminated such Participant’s employment, director status or consultancy with the Company or with an Affiliate, except as the
Administrator may otherwise expressly provide. 

  
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 In addition, for purposes of this Paragraph 17 and Paragraph 18 below, any change of employment
or other service within or among the Company and any Affiliates shall not be treated as a termination of employment, director status or consultancy so long as the Participant continues to be an Employee, director or Consultant of the Company or any
Affiliate. 
  

	 	18.	EFFECT ON STOCK GRANTS AND STOCK-BASED AWARDS OF TERMINATION OF SERVICE OTHER THAN FOR CAUSE OR DEATH OR DISABILITY. 

Except as otherwise provided in a Participant’s Stock Grant Agreement, in the event of a termination of service (whether as an Employee,
director or Consultant), other than termination for Cause, Disability, or death for which events there are special rules in Paragraphs 19, 20, and 21, respectively, before all forfeiture provisions or Company rights of repurchase (other than rights
to repurchase at then fair market value following termination of service as an Employee, director or Consultant) shall have lapsed, then the Company shall have the right to cancel or repurchase that number of Shares subject to a Stock Grant as to
which the Company’s forfeiture or repurchase rights have not lapsed. 
  

	 	19.	EFFECT ON STOCK GRANTS AND STOCK-BASED AWARDS OF TERMINATION OF SERVICE FOR CAUSE. 

Except as otherwise provided in a Participant’s Stock Grant Agreement, the following rules apply if the Participant’s service
(whether as an Employee, director or Consultant) with the Company or an Affiliate is terminated for Cause: 
 (a) All Shares subject to any
Stock Grant that remain subject to forfeiture provisions or as to which the Company shall have a repurchase right shall be immediately forfeited to the Company as of the time the Participant is notified his or her service is terminated for Cause.

 (b) Cause is not limited to events which have occurred prior to a Participant’s termination of service, nor is it necessary that the
Administrator’s finding of Cause occur prior to termination. If the Administrator determines, subsequent to a Participant’s termination of service, that either prior or subsequent to the Participant’s termination the Participant
engaged in conduct which would constitute Cause, then all Shares subject to any Stock Grant that remained subject to forfeiture provisions or as to which the Company had a repurchase right on the date of termination shall be immediately forfeited to
the Company. 
  

	 	20.	EFFECT ON STOCK GRANTS AND STOCK-BASED AWARDS OF TERMINATION OF SERVICE FOR DISABILITY. 

Except as otherwise provided in a Participant’s Stock Grant Agreement, the following rules apply if a Participant ceases to be an
Employee, director or Consultant of the Company or of an Affiliate by reason of Disability: to the extent the forfeiture provisions or the Company’s rights of repurchase have not lapsed on the date of Disability, they shall be exercisable;
provided, however, that in the event such forfeiture provisions or rights of repurchase lapse periodically, such provisions or rights shall lapse to the extent of a pro rata portion of the Shares subject to such Stock Grant through the date of
Disability as would have lapsed had the Participant not become Disabled. The proration shall be based upon the number of days accrued prior to the date of Disability. 

  
 13 

 The Administrator shall make the determination both as to whether Disability has occurred and the
date of its occurrence (unless a procedure for such determination is set forth in another agreement between the Company and such Participant, in which case such procedure shall be used for such determination). If requested, the Participant shall be
examined by a physician selected or approved by the Administrator, the cost of which examination shall be paid for by the Company. 
  

	 	21.	EFFECT ON STOCK GRANTS OF DEATH WHILE AN EMPLOYEE, DIRECTOR OR CONSULTANT. 

 Except as
otherwise provided in a Participant’s Stock Grant Agreement, the following rules apply in the event of the death of a Participant while the Participant is an Employee, director or Consultant of the Company or of an Affiliate: to the extent the
forfeiture provisions or the Company’s rights of repurchase have not lapsed on the date of death, they shall be exercisable; provided, however, that in the event such forfeiture provisions or rights of repurchase lapse periodically, such
provisions or rights shall lapse to the extent of a pro rata portion of the Shares subject to such Stock Grant through the date of death as would have lapsed had the Participant not died. The proration shall be based upon the number of days accrued
prior to the Participant’s date of death. 
  

	 	22.	PURCHASE FOR INVESTMENT. 

 Unless the offering and sale of the Shares shall have been
effectively registered under the Securities Act, the Company shall be under no obligation to issue Shares under the Plan unless and until the following conditions have been fulfilled: 

(a) The person who receives a Stock Right shall warrant to the Company, prior to the receipt of Shares, that such person is acquiring such
Shares for his or her own account, for investment, and not with a view to, or for sale in connection with, the distribution of any such Shares, in which event the person acquiring such Shares shall be bound by the provisions of the following legend
(or a legend in substantially similar form) which shall be endorsed upon the certificate evidencing the Shares issued pursuant to such exercise or such grant: 

“The shares represented by this certificate have been taken for investment and they may not be sold or otherwise transferred by any
person, including a pledgee, unless (1) either (a) a Registration Statement with respect to such shares shall be effective under the Securities Act of 1933, as amended, or (b) the Company shall have received an opinion of counsel
satisfactory to it that an exemption from registration under such Act is then available, and (2) there shall have been compliance with all applicable state securities laws.” 

(b) At the discretion of the Administrator, the Company shall have received an opinion of its counsel that the Shares may be issued in
compliance with the Securities Act without registration thereunder. 

  
 14 

	 	23.	DISSOLUTION OR LIQUIDATION OF THE COMPANY. 

 Upon the dissolution or liquidation of the
Company, all Options granted under this Plan which as of such date shall not have been exercised and all Stock Grants and Stock-Based Awards which have not been accepted, to the extent required under the applicable Agreement, will terminate and
become null and void; provided, however, that if the rights of a Participant or a Participant’s Survivors have not otherwise terminated and expired, the Participant or the Participant’s Survivors will have the right immediately prior to
such dissolution or liquidation to exercise or accept any Stock Right to the extent that the Stock Right is exercisable or subject to acceptance as of the date immediately prior to such dissolution or liquidation. Upon the dissolution or liquidation
of the Company, any outstanding Stock-Based Awards shall immediately terminate unless otherwise determined by the Administrator or specifically provided in the applicable Agreement. 

 

	 	24.	ADJUSTMENTS. 

 Upon the occurrence of any of the following events, a Participant’s
rights with respect to any Stock Right granted to him or her hereunder shall be adjusted as hereinafter provided, unless otherwise specifically provided in a Participant’s Agreement: 

(a) Stock Dividends and Stock Splits. If (i) the shares of Common Stock shall be subdivided or combined into a greater or smaller
number of shares or if the Company shall issue any shares of Common Stock as a stock dividend on its outstanding Common Stock, or (ii) additional shares or new or different shares or other securities of the Company or other non-cash assets are
distributed with respect to such shares of Common Stock, each Stock Right and the number of shares of Common Stock deliverable thereunder shall be appropriately increased or decreased proportionately, and appropriate adjustments shall be made
including, in the exercise or purchase price per share, to reflect such events. The number of Shares subject to the limitations in Paragraphs 3(a) and 4(c) shall also be proportionately adjusted upon the occurrence of such events. 

(b) Corporate Transactions. If the Company is to be consolidated with or acquired by another entity in a merger, consolidation, sale of
all or substantially all of the Company’s assets or the acquisition of all of the outstanding voting stock of the Company in a single transaction or a series of related transactions other than a transaction to merely change the state of
incorporation (a “Corporate Transaction”), the Administrator or the board of directors of any entity assuming the obligations of the Company hereunder (the “Successor Board”), shall, as to outstanding Options, either
(i) make appropriate provision for the continuation of such Options by substituting on an equitable basis for the Shares then subject to such Options either the consideration payable with respect to the outstanding shares of Common Stock in
connection with the Corporate Transaction or securities of any successor or acquiring entity; or (ii) upon written notice to the Participants, provide that such Options must be exercised (either (A) to the extent then exercisable or,
(B) at the discretion of the Administrator, any such Options being made partially or fully exercisable for purposes of this Subparagraph), within a specified number of days of the date of such notice, at the end of which period such Options
which have not been exercised shall terminate; or (iii) terminate such Options in exchange for payment of an amount equal to the consideration payable upon consummation of such Corporate Transaction to a holder

  
 15 

 
of the number of shares of Common Stock into which such Option would have been exercisable (either (A) to the extent then exercisable or, (B) at the discretion of the Administrator, any
such Options being made partially or fully exercisable for purposes of this Subparagraph) less the aggregate exercise price thereof. For purposes of determining the payments to be made pursuant to Subclause (iii) above, in the case of a
Corporate Transaction the consideration for which, in whole or in part, is other than cash, the consideration other than cash shall be valued at the fair value thereof as determined in good faith by the Board of Directors. 

With respect to outstanding Stock Grants, the Administrator or the Successor Board, shall make appropriate provision for the continuation of
such Stock Grants on the same terms and conditions by substituting on an equitable basis for the Shares then subject to such Stock Grants either the consideration payable with respect to the outstanding Shares of Common Stock in connection with the
Corporate Transaction or securities of any successor or acquiring entity. In lieu of the foregoing, in connection with any Corporate Transaction, the Administrator may provide that, upon consummation of the Corporate Transaction, each outstanding
Stock Grant shall be terminated in exchange for payment of an amount equal to the consideration payable upon consummation of such Corporate Transaction to a holder of the number of shares of Common Stock comprising such Stock Grant (to the extent
such Stock Grant is no longer subject to any forfeiture or repurchase rights then in effect or, at the discretion of the Administrator, all forfeiture and repurchase rights being waived upon such Corporate Transaction). For purposes of determining
such payments, in the case of a Corporate Transaction the consideration for which, in whole or in part, is other than cash, the consideration other than cash shall be valued at the fair value thereof as determined in good faith by the Board of
Directors. 
 In taking any of the actions permitted under this Paragraph 24(b), the Administrator shall not be obligated by the Plan to
treat all Stock Rights, all Stock Rights held by a Participant, or all Stock Rights of the same type, identically. 
 (c) Recapitalization
or Reorganization. In the event of a recapitalization or reorganization of the Company other than a Corporate Transaction pursuant to which securities of the Company or of another corporation, limited liability company or other entity are issued
with respect to the outstanding shares of Common Stock, a Participant upon exercising an Option or accepting a Stock Grant after the recapitalization or reorganization shall be entitled to receive for the price paid upon such exercise or acceptance
if any, the number of replacement securities which would have been received if such Option had been exercised or Stock Grant accepted prior to such recapitalization or reorganization. 

(d) Adjustments to Stock-Based Awards. Upon the happening of any of the events described in Subparagraphs (a), (b) or
(c) above, any outstanding Stock-Based Award shall be appropriately adjusted to reflect the events described in such Subparagraphs. The Administrator or the Successor board shall determine the specific adjustments to be made under Paragraph 24,
including, but not limited to, the effect of any Corporate Transaction and, subject to Paragraph 4, its determination shall be conclusive. 

(e) Modification of Options. Notwithstanding the foregoing, any adjustments made pursuant to Subparagraph (a), (b) or
(c) above with respect to Options shall be made only after the Administrator determines whether such adjustments would (i) constitute a “modification” of 

  
 16 

 
any ISOs (as that term is defined in Section 424(h) of the Code) or (ii) cause any adverse tax consequences for the holders of Options, including, but not limited to, pursuant to
Section 409A of the Code. If the Administrator determines that such adjustments made with respect to Options would constitute a modification or other adverse tax consequence, it may in its discretion refrain from making such adjustments, unless
the holder of an Option specifically agrees in writing that such adjustment be made and such writing indicates that the holder has full knowledge of the consequences of such “modification” on his or her income tax treatment with respect to
the Option. This paragraph shall not apply to the acceleration of the vesting of any ISO that would cause any portion of the ISO to violate the annual vesting limitation contained in Section 422(d) of the Code, as described in Paragraph
6(b)(iv). 
  

	 	25.	ISSUANCES OF SECURITIES. 

 Except as expressly provided herein, no issuance by the
Company of shares of stock of any class, or securities convertible into shares of stock of any class, shall affect, and no adjustment by reason thereof shall be made with respect to, the number or price of shares subject to Stock Rights. Except as
expressly provided herein, no adjustments shall be made for dividends paid in cash or in property (including without limitation, securities) of the Company prior to any issuance of Shares pursuant to a Stock Right. 

 

	 	26.	FRACTIONAL SHARES. 

 No fractional shares shall be issued under the Plan and the person
exercising a Stock Right shall receive from the Company cash in lieu of such fractional shares equal to the Fair Market Value thereof. 
  

	 	27.	CONVERSION OF ISOs INTO NON-QUALIFIED OPTIONS; TERMINATION OF ISOs. 

 The Administrator,
at the written request of any Participant, may in its discretion take such actions as may be necessary to convert such Participant’s ISOs (or any portions thereof) that have not been exercised on the date of conversion into Non-Qualified Options at any time prior to the expiration of such ISOs, regardless of whether the Participant is an Employee of the Company or an Affiliate at the time of such conversion. At the time of such
conversion, the Administrator (with the consent of the Participant) may impose such conditions on the exercise of the resulting Non-Qualified Options as the Administrator in its discretion may determine,
provided that such conditions shall not be inconsistent with this Plan. Nothing in the Plan shall be deemed to give any Participant the right to have such Participant’s ISOs converted into Non-Qualified
Options, and no such conversion shall occur until and unless the Administrator takes appropriate action. The Administrator, with the consent of the Participant, may also terminate any portion of any ISO that has not been exercised at the time of
such conversion. 
  

	 	28.	WITHHOLDING. 

 In the event that any federal, state, or local income taxes, employment
taxes, Federal Insurance Contributions Act (“F.I.C.A.”) withholdings or other amounts are required by applicable law or governmental regulation to be withheld from the Participant’s salary, wages or other remuneration in connection
with the issuance of a Stock Right or Shares under the Plan or 

  
 17 

 
upon the lapsing of any forfeiture provision or right of repurchase or for any other reason required by law, the Company may withhold from the Participant’s compensation, if any, or may
require that the Participant advance in cash to the Company, or to any Affiliate of the Company which employs or employed the Participant, the statutory minimum amount of such withholdings unless a different withholding arrangement, including the
use of shares of the Company’s Common Stock or a promissory note, is authorized by the Administrator (and permitted by law). For purposes hereof, the fair market value of the shares withheld for purposes of payroll withholding shall be
determined in the manner set forth under the definition of Fair Market Value provided in Paragraph 1 above, as of the most recent practicable date prior to the date of exercise. If the Fair Market Value of the shares withheld is less than the amount
of payroll withholdings required, the Participant may be required to advance the difference in cash to the Company or the Affiliate employer. The Administrator in its discretion may condition the exercise of an Option for less than the then Fair
Market Value on the Participant’s payment of such additional withholding. 
  

	 	29.	NOTICE TO COMPANY OF DISQUALIFYING DISPOSITION. 

 Each Employee who receives an ISO shall
notify the Company in writing immediately after the Employee makes a Disqualifying Disposition of any Shares acquired pursuant to the exercise of an ISO. A Disqualifying Disposition is defined in Section 424(c) of the Code and includes any
disposition (including any sale or gift) of such Shares before the later of (a) two years after the date the Employee was granted the ISO, or (b) one year after the date the Employee acquired Shares by exercising the ISO, except as
otherwise provided in Section 424(c) of the Code. If the Employee has died before such Shares are sold, these holding period requirements do not apply and no Disqualifying Disposition can occur thereafter. 

 

	 	30.	TERMINATION OF THE PLAN. 

 The Plan will terminate on May 15, 2027, the date which
is ten years from the earlier of the date of its adoption by the Board of Directors and the date of its approval by the shareholders of the Company. The Plan may be terminated at an earlier date by vote of the shareholders or the Board of
Directors of the Company; provided, however, that any such earlier termination shall not affect any Agreements executed prior to the effective date of such termination. Termination of the Plan shall not affect any Stock Rights theretofore granted.

  

	 	31.	AMENDMENT OF THE PLAN AND AGREEMENTS. 

 The Plan may be amended by the shareholders of
the Company. The Plan may also be amended by the Administrator, including, without limitation, to the extent necessary to qualify any or all outstanding Stock Rights granted under the Plan or Stock Rights to be granted under the Plan for favorable
federal income tax treatment as may be afforded incentive stock options under Section 422 of the Code (including deferral of taxation upon exercise), and to the extent necessary to qualify the Shares issuable under the Plan for listing on any
national securities exchange or quotation in any national automated quotation system of securities dealers. Any amendment approved by the Administrator which the Administrator determines is of a scope that requires shareholder approval shall be
subject to obtaining such shareholder approval. Any modification or amendment of the Plan shall not, without the consent of a Participant, adversely 

  
 18 

 
affect his or her rights under a Stock Right previously granted to him or her. With the consent of the Participant affected, the Administrator may amend outstanding Agreements in a manner which
may be adverse to the Participant but which is not inconsistent with the Plan. In the discretion of the Administrator, outstanding Agreements may be amended by the Administrator in a manner which is not adverse to the Participant. 

 

	 	32.	EMPLOYMENT OR OTHER RELATIONSHIP. 

 Nothing in this Plan or any Agreement shall be deemed
to prevent the Company or an Affiliate from terminating the employment, consultancy or director status of a Participant, nor to prevent a Participant from terminating his or her own employment, consultancy or director status or to give any
Participant a right to be retained in employment or other service by the Company or any Affiliate for any period of time. 
  

	 	33.	GOVERNING LAW. 

 This Plan shall be construed and enforced in accordance with the law of
the State of Delaware. 

  
 19EX-10.17

 Exhibit 10.17 

Option No.                 

SYNLOGIC, INC. 
 Stock
Option Grant Notice 
 Stock Option Grant under the Company’s 2017 Stock Incentive Plan 

 

					
	1.	    	Name and Address of Participant:	  	      

		    		  	      

		    		  	      

			
	2.	    	Date of Option Grant:	  	      

			
	3.	    	Type of Grant:	  	      

			
	4.	    	 Maximum Number of Shares for
 which this Option
is exercisable:
	  	      

			
	5.	    	Exercise (purchase) price per share:	  	      

			
	6.	    	Option Expiration Date:	  	      

			
	7.	    	Vesting Start Date:	  	      

			
	8.	    	Vesting Schedule:	  	

 [Notwithstanding the foregoing, in the event of a Change of Control (as defined below), while the Participant is an Employee,
director or Consultant of the Company or an Affiliate, [    ]% of the Shares which would have vested in each vesting installment remaining under this Option will be vested and exercisable for purposes of Paragraph 24(b) of the
Plan unless this Option has otherwise expired or been terminated pursuant to its terms or the terms of the Plan. 
 Change of Control
means the occurrence of any of the following events: 
  

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

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

  

	 	(iii)	Change in Board Composition. A change in the composition of the Board of Directors, as a result of which fewer than a majority of the directors are Incumbent Directors. “Incumbent Directors” shall mean
directors who either (A) are directors of the Company as of [            ], 20[    ], or (B) are elected, or nominated for election, to the
Board of Directors with the affirmative votes of at least a majority of the Incumbent Directors at the time of such election or nomination (but shall not include an individual whose election or nomination is in connection with an actual or
threatened proxy contest relating to the election of directors to the Company). 

  

	 	(iv)	“Change of Control” shall be interpreted, if applicable, in a manner, and limited to the extent necessary, so that it will not cause adverse tax consequences under Section 409A of the Code.]

 The vesting is further subject to the other terms and conditions of this Agreement and the Company’s 2017 Stock
Incentive Plan. 
 [Remainder of page intentionally left blank] 

  
 2 

 The Company and the Participant acknowledge receipt of this Stock Option Grant Notice and agree to the terms of
the Stock Option Agreement attached hereto and incorporated by reference herein, the Company’s 2017 Stock Incentive Plan and the terms of this Option Grant as set forth above. 

 

					
	SYNLOGIC, INC.
		
	By:	 	 
		 	Name:	 	 
		 	Title:	 	 
			
		 		 	
	Participant

 SYNLOGIC, INC. 

STOCK OPTION AGREEMENT- INCORPORATED TERMS AND CONDITIONS 

AGREEMENT made as of the date of grant set forth in the Stock Option Grant Notice by and between Synlogic, Inc. (the “Company”), a
Delaware corporation, and the individual whose name appears on the Stock Option Grant Notice (the “Participant”). 
 WHEREAS, the
Company desires to grant to the Participant an Option to purchase shares of its common stock, $0.0001 par value per share (the “Shares”), under and for the purposes set forth in the Company’s 2017 Stock Incentive Plan (the
“Plan”); 
 WHEREAS, the Company and the Participant understand and agree that any terms used and not defined herein have the same
meanings as in the Plan; and 
 WHEREAS, the Company and the Participant each intend that the Option granted herein shall be of the type set
forth in the Stock Option Grant Notice. 
 NOW, THEREFORE, in consideration of the mutual covenants hereinafter set forth and for other good
and valuable consideration, the parties hereto agree as follows: 
  

	 	1.	GRANT OF OPTION. 

 The Company hereby grants to the Participant the right and option to
purchase all or any part of an aggregate of the number of Shares set forth in the Stock Option Grant Notice, on the terms and conditions and subject to all the limitations set forth herein, under United States securities and tax laws, and in the
Plan, which is incorporated herein by reference. The Participant acknowledges receipt of a copy of the Plan. 
  

	 	2.	EXERCISE PRICE. 

 The exercise price of the Shares covered by the Option shall be the
amount per Share set forth in the Stock Option Grant Notice, subject to adjustment, as provided in the Plan, in the event of a stock split, reverse stock split or other events affecting the holders of Shares after the date hereof (the “Exercise
Price”). Payment shall be made in accordance with Paragraph 9 of the Plan. 
  

	 	3.	EXERCISABILITY OF OPTION. 

 Subject to the terms and conditions set forth in this
Agreement and the Plan, the Option granted hereby shall become vested and exercisable as set forth in the Stock Option Grant Notice and is subject to the other terms and conditions of this Agreement and the Plan. 

	 	4.	TERM OF OPTION. 

 This Option shall terminate on the Option Expiration Date as specified
in the Stock Option Grant Notice and, if this Option is designated in the Stock Option Grant Notice as an ISO and the Participant owns as of the date hereof more than 10% of the total combined voting power of all classes of capital stock of the
Company or an Affiliate, such date may not be more than five years from the date of this Agreement, but shall be subject to earlier termination as provided herein or in the Plan. 

If the Participant ceases to be an Employee, director or Consultant of the Company or of an Affiliate for any reason other than the death or
Disability of the Participant, or termination of the Participant for Cause (the “Termination Date”), the Option to the extent then vested and exercisable pursuant to Section 3 hereof as of the Termination Date, and not previously
terminated in accordance with this Agreement, may be exercised within three (3) months after the Termination Date, or on or prior to the Option Expiration Date as specified in the Stock Option Grant Notice, whichever is earlier, but may not be
exercised thereafter except as set forth below. In such event, the unvested portion of the Option shall not be exercisable and shall expire and be cancelled on the Termination Date. 

If this Option is designated in the Stock Option Grant Notice as an ISO and the Participant ceases to be an Employee of the Company or of an
Affiliate but continues after termination of employment to provide service to the Company or an Affiliate as a director or Consultant, this Option shall continue to vest in accordance with Section 3 above as if this Option had not terminated
until the Participant is no longer providing services to the Company. In such case, this Option shall automatically convert and be deemed a Non-Qualified Option as of the date that is three (3) months from termination of the Participant’s
employment and this Option shall continue on the same terms and conditions set forth herein until such Participant is no longer providing service to the Company or an Affiliate. 

Notwithstanding the foregoing, in the event of the Participant’s Disability or death within three (3) months after the Termination
Date, the Participant or the Participant’s Survivors may exercise the Option within one (1) year after the Termination Date, but in no event after the Option Expiration Date as specified in the Stock Option Grant Notice, and this Option
shall thereupon terminate. 
 In the event the Participant’s service is terminated by the Company or an Affiliate for Cause, the
Participant’s right to exercise any unexercised portion of this Option even if vested shall cease immediately as of the time the Participant is notified his or her service is terminated for Cause, and this Option shall thereupon terminate.
Notwithstanding anything herein to the contrary, if subsequent to the Participant’s termination, but prior to the exercise of the Option, the Administrator determines that, either prior or subsequent to the Participant’s termination, the
Participant engaged in conduct which would constitute Cause, then the Participant shall immediately cease to have any right to exercise the Option and this Option shall thereupon terminate. 

  
 2 

 In the event of the Disability of the Participant while an Employee, director or Consultant of
the Company or of an Affiliate, as determined in accordance with the Plan, the Option shall be exercisable within one (1) year after the Participant’s termination of service due to Disability or, if earlier, on or prior to the Option
Expiration Date as specified in the Stock Option Grant Notice. In such event, the Option shall be exercisable: 
  

	 	(a)	to the extent that the Option has become exercisable but has not been exercised as of the date of the Participant’s termination of service due to Disability; and 

 

	 	(b)	in the event rights to exercise the Option accrue periodically, to the extent of a pro rata portion through the date of the Participant’s termination of service due to Disability of any additional vesting rights
that would have accrued on the next vesting date had the Participant not become Disabled. The proration shall be based upon the number of days accrued in the current vesting period prior to the date of the Participant’s termination of service
due to Disability. 

 In the event of the death of the Participant while an Employee, director or Consultant of the Company or
of an Affiliate, the Option shall be exercisable by the Participant’s Survivors within one year after the date of death of the Participant or, if earlier, on or prior to the Option Expiration Date as specified in the Stock Option Grant Notice.
In such event, the Option shall be exercisable: 
  

	 	(x)	to the extent that the Option has become exercisable but has not been exercised as of the date of death; and 

  

	 	(y)	in the event rights to exercise the Option accrue periodically, to the extent of a pro rata portion through the date of death of any additional vesting rights that would have accrued on the next vesting date had the
Participant not died. The proration shall be based upon the number of days accrued in the current vesting period prior to the Participant’s date of death. 

  

	 	5.	METHOD OF EXERCISING OPTION. 

 Subject to the terms and conditions of this Agreement, the
Option may be exercised by written notice to the Company or its designee, in substantially the form of Exhibit A attached hereto (or in such other form acceptable to the Company, which may include electronic notice). Such notice shall
state the number of Shares with respect to which the Option is being exercised and shall be signed by the person exercising the Option (which signature may be provided electronically in a form acceptable to the Company). Payment of the Exercise
Price for such Shares shall be made in accordance with Paragraph 9 of the Plan. The Company shall deliver such Shares as soon as practicable after the notice shall be received, provided, however, that the Company may delay issuance of such Shares
until completion of any action or obtaining of any consent, which the Company deems necessary under any applicable law (including, without limitation, state securities or “blue sky” laws). The Shares as to which the Option shall

  
 3 

 
have been so exercised shall be registered in the Company’s share register in the name of the person so exercising the Option (or, if the Option shall be exercised by the Participant and if
the Participant shall so request in the notice exercising the Option, shall be registered in the Company’s share register in the name of the Participant and another person jointly, with right of survivorship) and shall be delivered as provided
above to or upon the written order of the person exercising the Option. In the event the Option shall be exercised, pursuant to Section 4 hereof, by any person other than the Participant, such notice shall be accompanied by appropriate proof of
the right of such person to exercise the Option. All Shares that shall be purchased upon the exercise of the Option as provided herein shall be fully paid and nonassessable. 
  

	 	6.	PARTIAL EXERCISE. 

 Exercise of this Option to the extent above stated may be made in
part at any time and from time to time within the above limits, except that no fractional share shall be issued pursuant to this Option. 
  

	 	7.	NON-ASSIGNABILITY. 

 The Option shall not be
transferable by the Participant otherwise than by will or by the laws of descent and distribution. If this Option is a Non-Qualified Option then it may also be transferred pursuant to a qualified domestic relations order as defined by the Code or
Title I of the Employee Retirement Income Security Act or the rules thereunder. Except as provided above in this paragraph, the Option shall be exercisable, during the Participant’s lifetime, only by the Participant (or, in the event of legal
incapacity or incompetency, by the Participant’s guardian or representative) and shall not be assigned, pledged or hypothecated in any way (whether by operation of law or otherwise) and shall not be subject to execution, attachment or similar
process. Any attempted transfer, assignment, pledge, hypothecation or other disposition of the Option or of any rights granted hereunder contrary to the provisions of this Section 7, or the levy of any attachment or similar process upon the
Option shall be null and void. 
  

	 	8.	NO RIGHTS AS STOCKHOLDER UNTIL EXERCISE. 

 The Participant shall have no rights as a
stockholder with respect to Shares subject to this Agreement until registration of the Shares in the Company’s share register in the name of the Participant. Except as is expressly provided in the Plan with respect to certain changes in the
capitalization of the Company, no adjustment shall be made for dividends or similar rights for which the record date is prior to the date of such registration. 
  

	 	9.	ADJUSTMENTS. 

 The Plan contains provisions covering the treatment of Options in a number
of contingencies such as stock splits and mergers. Provisions in the Plan for adjustment with respect to stock subject to Options and the related provisions with respect to successors to the business of the Company are hereby made applicable
hereunder and are incorporated herein by reference. 

  
 4 

	 	10.	TAXES. 

 The Participant acknowledges and agrees that (i) any income or other taxes
due from the Participant with respect to this Option or the Shares issuable upon exercise of this Option shall be the Participant’s responsibility; (ii) the Participant was free to use professional advisors of his or her choice in
connection with this Agreement, has received advice from his or her professional advisors in connection with this Agreement, understands its meaning and import, and is entering into this Agreement freely and without coercion or duress;
(iii) the Participant has not received and is not relying upon any advice, representations or assurances made by or on behalf of the Company or any Affiliate or any Employee of or counsel to the Company or any Affiliate regarding any tax or
other effects or implications of the Option, the Shares or other matters contemplated by this Agreement and (iv) neither the Administrator, the Company, its Affiliates, nor any of its officers or directors, shall be held liable for any
applicable costs, taxes, or penalties associated with the Option if, in fact, the Internal Revenue Service were to determine that the Option constitutes deferred compensation under Section 409A of the Code. 

If this Option is designated in the Stock Option Grant Notice as a Non-Qualified Option or if the Option is an ISO and is converted into a
Non-Qualified Option and such Non-Qualified Option is exercised, the Participant agrees that the Company may withhold from the Participant’s remuneration, if any, the minimum statutory amount of federal, state and local withholding taxes
attributable to such amount that is considered compensation includable in such person’s gross income. At the Company’s discretion, the amount required to be withheld may be withheld in cash from such remuneration, or in kind from the
Shares otherwise deliverable to the Participant on exercise of the Option. The Participant further agrees that, if the Company does not withhold an amount from the Participant’s remuneration sufficient to satisfy the Company’s income tax
withholding obligation, the Participant will reimburse the Company on demand, in cash, for the amount under-withheld. 
  

	 	11.	PURCHASE FOR INVESTMENT. 

 Unless the offering and sale of the Shares to be issued upon
the particular exercise of the Option shall have been effectively registered under the Securities Act of 1933, as now in force or hereafter amended (the “1933 Act”), the Company shall be under no obligation to issue the Shares covered by
such exercise unless the Company has determined that such exercise and issuance would be exempt from the registration requirements of the 1933 Act and until the following conditions have been fulfilled: 

 

	 	(a)	The person(s) who exercise the Option shall warrant to the Company, at the time of such exercise, that such person(s) are acquiring such Shares for their own respective accounts, for investment, and not with a view to,
or for sale in connection with, the distribution of any such Shares, in which event the person(s) acquiring such Shares shall be bound by the provisions of the following legend which shall be endorsed upon any certificate(s) evidencing the Shares
issued pursuant to such exercise: 

  
 5 

 “The shares represented by this certificate have been taken for investment and they may not
be sold or otherwise transferred by any person, including a pledgee, unless (1) either (a) a Registration Statement with respect to such shares shall be effective under the Securities Act of 1933, as amended, or (b) the Company shall
have received an opinion of counsel satisfactory to it that an exemption from registration under such Act is then available, and (2) there shall have been compliance with all applicable state securities laws;” and 

 

	 	(b)	If the Company so requires, the Company shall have received an opinion of its counsel that the Shares may be issued upon such particular exercise in compliance with the 1933 Act without registration thereunder. Without
limiting the generality of the foregoing, the Company may delay issuance of the Shares until completion of any action or obtaining of any consent, which the Company deems necessary under any applicable law (including without limitation state
securities or “blue sky” laws). 

  

	 	12.	RESTRICTIONS ON TRANSFER OF SHARES. 

 12.1 The Shares acquired by the Participant
pursuant to the exercise of the Option granted hereby shall not be transferred by the Participant except as permitted herein. 
 12.2
[Intentionally Omitted] 
 12.3 It shall be a condition precedent to the validity of any sale or other transfer of any Shares by the
Participant that the following restrictions be complied with (except as otherwise provided in this Section 12): 
  

	 	(i)	No Shares owned by the Participant may be sold, pledged or otherwise transferred (including by gift or devise) to any person or entity, voluntarily, or by operation of law, except in accordance with the terms and
conditions hereinafter set forth. 

  

	 	(ii)	 Before selling or otherwise transferring all or part of the Shares, the Participant shall give written notice of
such intention to the Company, which notice shall include the name of the proposed transferee, the proposed purchase price per share, the terms of payment of such purchase price and all other matters relating to such sale or transfer and shall be
accompanied by a copy of the binding written agreement of the proposed transferee to purchase the Shares of the Participant. Such notice shall constitute a binding offer by the Participant to sell to the Company such number of the Shares then held
by the Participant as are proposed to be sold in the notice at the monetary price per share designated in such notice, payable on the terms offered to the Participant by the proposed transferee (provided, however, that the Company shall not be
required to meet any non-monetary terms of the proposed transfer, including, without limitation, delivery of other securities in exchange for the Shares proposed to be sold). The Company shall give written
notice to the Participant as to whether such offer has 

  
 6 

	 	
been accepted in whole by the Company within sixty (60) days after its receipt of written notice from the Participant. The Company may only accept such offer in whole and may not accept such
offer in part. Such acceptance notice shall fix a time, location and date for the Closing on such purchase (“Closing Date”) which shall not be less than ten (10) nor more than sixty (60) days after the giving of the acceptance
notice, provided, however, if any of the Shares to be sold pursuant to this Section 12.3 have been held by the Participant for less than six (6) months, then the Closing Date may be extended by the Company until no more than ten
(10) days after such Shares have been held by the Participant for six (6) months if required under applicable accounting rules in effect at the time. The place for such Closing shall be at the Company’s principal office. At such
Closing, the Participant shall accept payment as set forth herein and shall deliver to the Company in exchange therefor certificates for the number of Shares stated in the notice accompanied by duly executed instruments of transfer.

  

	 	(iii)	If the Company shall fail to accept any such offer, the Participant shall be free to sell all, but not less than all, of the Shares set forth in his or her notice to the designated transferee at the price and terms
designated in the Participant’s notice, provided that (i) such sale is consummated within six (6) months after the giving of notice by the Participant to the Company as aforesaid, and (ii) the transferee first agrees in writing
to be bound by the provisions of this Section 12 so that such transferee (and all subsequent transferees) shall thereafter only be permitted to sell or transfer the Shares in accordance with the terms hereof. After the expiration of such six
(6) months, the provisions of this Section 12.3 shall again apply with respect to any proposed voluntary transfer of the Participant’s Shares. 

  

	 	(iv)	The restrictions on transfer contained in this Section 12.3 shall not apply to (a) transfers by the Participant to his or her spouse or children or to a trust for the benefit of his or her spouse or children,
(b) transfers by the Participant to his or her guardian or conservator, and (c) transfers by the Participant, in the event of his or her death, to his or her executor(s) or administrator(s) or to trustee(s) under his or her will
(collectively, “Permitted Transferees”); provided however, that in any such event the Shares so transferred in the hands of each such Permitted Transferee shall remain subject to this Agreement, and each such Permitted Transferee shall so
acknowledge in writing as a condition precedent to the effectiveness of such transfer. 

  

	 	(v)	The provisions of this Section 12.3 may be waived by the Company. Any such waiver may be unconditional or based upon such conditions as the Company may impose. 

12.4 In the event that the Participant or his or her successor in interest fails to deliver the Shares to be repurchased by the Company under
this Agreement, the Company may elect (a) to establish a segregated account in the amount of the repurchase price, such account to be turned over to the Participant or his or her successor in interest upon delivery of such Shares, and
(b) immediately to take such action as is appropriate to transfer record title of such Shares from 

  
 7 

 
the Participant to the Company and to treat the Participant and such Shares in all respects as if delivery of such Shares had been made as required by this Agreement. The Participant hereby
irrevocably grants the Company a power of attorney which shall be coupled with an interest for the purpose of effectuating the preceding sentence. 

12.5 If the Company shall pay a stock dividend or declare a stock split on or with respect to any of its Common Stock, or otherwise distribute
securities of the Company to the holders of its Common Stock, the number of shares of stock or other securities of the Company issued with respect to the shares then subject to the restrictions contained in this Agreement shall be added to the
Shares subject to the Company’s rights to repurchase pursuant to this Agreement. If the Company shall distribute to its stockholders shares of stock of another corporation or equity in another entity, the shares of stock of such other
corporation or equity in such other entity, distributed with respect to the Shares then subject to the restrictions contained in this Agreement, shall be added to the Shares subject to the Company’s rights to repurchase pursuant to this
Agreement. 
 12.6 If the outstanding shares of Common Stock of the Company shall be subdivided into a greater number of shares or combined
into a smaller number of shares, or in the event of a reclassification of the outstanding shares of Common Stock of the Company, or if the Company shall be a party to a merger, consolidation or capital reorganization, there shall be substituted for
the Shares then subject to the restrictions contained in this Agreement such amount and kind of securities as are issued in such subdivision, combination, reclassification, merger, consolidation or capital reorganization in respect of the Shares
subject immediately prior thereto to the Company’s rights to repurchase pursuant to this Agreement. 
 12.7 The Company shall not be
required to transfer any Shares on its books which shall have been sold, assigned or otherwise transferred in violation of this Agreement, or to treat as owner of such Shares, or to accord the right to vote as such owner or to pay dividends to, any
person or organization to which any such Shares shall have been so sold, assigned or otherwise transferred, in violation of this Agreement. 

12.8 The provisions of Sections 12.1 and 12.3 shall terminate upon the effective date of the registration of the Shares pursuant to the
Securities Exchange Act of 1934. 
 12.9 The Participant agrees that in the event the Company proposes to offer for sale to the public any
of its equity securities and such Participant is requested by the Company and any underwriter engaged by the Company in connection with such offering to sign an agreement restricting the sale or other transfer of Shares, then it will promptly sign
such agreement and will not transfer, whether in privately negotiated transactions or to the public in open market transactions or otherwise, any Shares or other securities of the Company held by him or her during such period as is determined by the
Company and the underwriters, not to exceed 180 days following the closing of the offering, plus such additional period of time as may be required to comply with FINRA Rules or similar rules promulgated by another regulatory authority (such period,
the “Lock-Up Period”). Such agreement shall be in writing and in form and substance reasonably satisfactory to the Company and such underwriter and pursuant to customary and prevailing terms and conditions. Notwithstanding whether the
Participant has signed such an agreement, the Company may impose stop-transfer instructions with respect to the Shares or other securities of the Company subject to the foregoing restrictions until the end of the Lock-Up Period. 

  
 8 

 12.10 In the event that the Initiating Holders (as defined below) approve a Sale of the Company
(as defined below) then the Participant hereby agrees with respect to the Shares and any other shares of Common Stock that the Participant holds and any other Company securities over which the Participant otherwise exercises dispositive power (the
“Drag Along”): 
  

	 	(i)	in the event such transaction requires the approval of stockholders, (1) if the matter is to be brought to a vote at a stockholder meeting, after receiving proper notice of any meeting of stockholders of the
Company to vote on the approval of a Sale of the Company, to be present, in person or by proxy, as a holder of Shares, at all such meetings and be counted for the purposes of determining the presence of a quorum at such meetings; and (2) to
vote (in person, by proxy or by action by written consent, as applicable) all Shares in favor of such Sale of the Company and in opposition of any and all other proposals that could reasonably be expected to delay or impair the ability of the
Company to consummate such Sale of the Company; 

  

	 	(ii)	to refrain from exercising any dissenters’ rights or rights of appraisal under applicable law at any time with respect to such Sale of the Company; and 

 

	 	(iii)	to execute and deliver all related documentation and take such other action in support of the Sale of the Company as shall reasonably be requested by the Company. 

As used herein, the following terms shall have the following respective meanings: 

“Initiating Holders” means Persons holding not less than 50.1% of the shares of Common Stock of the Company then
outstanding, determined on an as-converted basis (and including, for this purpose, any and all shares of Common Stock issued or issuable upon conversion of the Company’s convertible preferred stock, but specifically excluding, for this purpose,
any then outstanding options and warrants). 
 “Sale of the Company” means: 

 

	 	(i)	 a merger or consolidation in which (A) the Company is a constituent party or (B) a subsidiary of the
Company is a constituent party and the Company issues shares of its capital stock pursuant to such merger or consolidation, except any such merger or consolidation involving the Company or a subsidiary in which the shares of capital stock of the
Company outstanding immediately prior to such merger or consolidation continue to represent, or are converted into or exchanged for shares of capital stock that represent, immediately following such merger or consolidation, at least a majority, by
voting power, of the capital stock of (1) the 

  
 9 

	 	
surviving or resulting corporation or (2) if the surviving or resulting corporation is a wholly owned subsidiary of another corporation immediately following such merger or consolidation,
the parent corporation of such surviving or resulting corporation (provided that, for the purpose of this clause (i) all shares of Common Stock issuable upon exercise of options or warrants outstanding immediately prior to such merger or
consolidation or upon conversion of convertible securities immediately prior to such merger or consolidation shall be deemed to be outstanding immediately prior to such merger or consolidation and, if applicable, converted or exchanged in such
merger or consolidation on the same terms as the actual outstanding shares of Common Stock are converted or exchanged); 

  

	 	(ii)	any transaction or series of related transactions to which the Company is a party in which in excess of fifty percent (50%) of the Company’s voting power is transferred such that the stockholders of the
Company immediately prior to the transaction or series of related transactions do not own a majority of the voting power of the surviving or acquiring entity following such transaction or series of transactions; other than any transaction or series
of transactions principally for bona fide equity financing purposes in which cash is received by the Company or any successor or indebtedness of the Company is cancelled or converted or a combination thereof; or 

 

	 	(iii)	the sale, lease, transfer, exclusive license (other than an exclusive license that is approved by the Board of Directors), or other disposition, in a single transaction or series of related transactions, by the Company
or any subsidiary of the Company of all or substantially all the assets of the Company and its subsidiaries taken as a whole, or the sale or disposition (whether by merger or otherwise) of one or more subsidiaries of the Company if substantially all
of the assets of the Company and its subsidiaries taken as a whole are held by such subsidiary or subsidiaries, except where such sale, lease, transfer, exclusive license (other than an exclusive license that is approved by the Board of Directors)
or other disposition is to a wholly owned subsidiary of the Company. 

 12.11 The Participant acknowledges and agrees that
neither the Company, its shareholders nor its directors and officers, has any duty or obligation to disclose to the Participant any material information regarding the business of the Company or affecting the value of the Shares before, at the time
of, or following a termination of the service of the Participant by the Company, including, without limitation, any information concerning plans for the Company to make a public offering of its securities or to be acquired by or merged with or into
another firm or entity. 
 12.12 All certificates representing the Shares to be issued to the Participant pursuant to this Agreement shall
have endorsed thereon a legend substantially as follows: “The shares represented by this certificate are subject to restrictions set forth in a Stock Option Agreement dated as of
                          , a copy of which Agreement is available for inspection at the offices of the Company
or will be made available upon request.” 

  
 10 

	 	13.	NO OBLIGATION TO MAINTAIN RELATIONSHIP. 

 The Participant acknowledges that: (i) the
Company is not by the Plan or this Option Agreement obligated to continue the Participant as an Employee, director or Consultant of the Company or an Affiliate; (ii) the Plan is discretionary in nature and may be suspended or terminated by the
Company at any time; (iii) the grant of the Option is a one-time benefit which does not create any contractual or other right to receive future grants of options, or benefits in lieu of options; (iv) all determinations with respect to any
such future grants, including, but not limited to, the times when options shall be granted, the number of shares subject to each option, the option price, and the time or times when each option shall be exercisable, will be at the sole discretion of
the Company; (v) the Participant’s participation in the Plan is voluntary; (vi) the value of the Option is an extraordinary item of compensation which is outside the scope of the Participant’s employment or consulting contract,
if any; and (vii) the Option is not part of normal or expected compensation for purposes of calculating any severance, resignation, redundancy, end of service payments, bonuses, long-service awards, pension or retirement benefits or similar
payments. 
  

	 	14.	IF OPTION IS INTENDED TO BE AN ISO. 

 If this Option is designated in the Stock Option
Grant Notice as an ISO so that the Participant (or the Participant’s Survivors) may qualify for the favorable tax treatment provided to holders of Options that meet the standards of Section 422 of the Code then any provision of this
Agreement or the Plan which conflicts with the Code so that this Option would not be deemed an ISO is null and void and any ambiguities shall be resolved so that the Option qualifies as an ISO. The Participant should consult with the
Participant’s own tax advisors regarding the tax effects of the Option and the requirements necessary to obtain favorable tax treatment under Section 422 of the Code, including, but not limited to, holding period requirements. 

Notwithstanding the foregoing, to the extent that the Option is designated in the Stock Option Grant Notice as an ISO and is not deemed to be
an ISO pursuant to Section 422(d) of the Code because the aggregate Fair Market Value (determined as of the Date of Option Grant) of any of the Shares with respect to which this ISO is granted becomes exercisable for the first time during any
calendar year in excess of $100,000, the portion of the Option representing such excess value shall be treated as a Non-Qualified Option and the Participant shall be deemed to have taxable income measured by the difference between the then Fair
Market Value of the Shares received upon exercise and the price paid for such Shares pursuant to this Agreement. 
 Neither the Company nor
any Affiliate shall have any liability to the Participant, or any other party, if the Option (or any part thereof) that is intended to be an ISO is not an ISO or for any action taken by the Administrator, including without limitation the conversion
of an ISO to a Non-Qualified Option. 
  

	 	15.	NOTICE TO COMPANY OF DISQUALIFYING DISPOSITION OF AN ISO. 

 If this Option is designated
in the Stock Option Grant Notice as an ISO then the Participant agrees to notify the Company in writing immediately after the Participant makes a 

  
 11 

 
Disqualifying Disposition of any of the Shares acquired pursuant to the exercise of the ISO. A Disqualifying Disposition is defined in Section 424(c) of the Code and includes any disposition
(including any sale) of such Shares before the later of (a) two years after the date the Participant was granted the ISO or (b) one year after the date the Participant acquired Shares by exercising the ISO, except as otherwise provided in
Section 424(c) of the Code. If the Participant has died before the Shares are sold, these holding period requirements do not apply and no Disqualifying Disposition can occur thereafter. 

 

	 	16.	NOTICES. 

 Any notices required or permitted by the terms of this Agreement or the Plan
shall be given by recognized courier service, facsimile, registered or certified mail, return receipt requested, or by email addressed as follows: 
 If to
the Company: 
 Synlogic, Inc. 

200 Sidney Street 
 Cambridge, MA
02139 
 Attention: Chief Financial Officer 

If to the Participant at the address set forth on the Stock Option Grant Notice or such address as the Company may then have in its records for the
Participant or to such other address or addresses of which notice in the same manner has previously been given. Any such notice shall be deemed to have been given upon the earlier of receipt, one business day following delivery to a recognized
courier service or three business days following mailing by registered or certified mail. 
  

	 	17.	GOVERNING LAW. 

 This Agreement shall be governed by and construed in accordance with the
laws of the State of Delaware, without giving effect to its internal principles governing the conflict of law. For the purpose of litigating any dispute that arises under this Agreement, the parties hereby consent to exclusive jurisdiction in the
Commonwealth of Massachusetts and agree that such litigation shall be conducted in the state courts of Suffolk County, Massachusetts or the federal courts of the United States for the District of Massachusetts. 

 

	 	18.	BENEFIT OF AGREEMENT. 

 Subject to the provisions of the Plan and the other provisions
hereof, this Agreement shall be for the benefit of and shall be binding upon the heirs, executors, administrators, successors and assigns of the parties hereto. 

  
 12 

	 	19.	ENTIRE AGREEMENT. 

 This Agreement, together with the Plan, embodies the entire agreement
and understanding between the parties hereto with respect to the subject matter hereof and supersedes all prior oral or written agreements and understandings relating to the subject matter hereof. No statement, representation, warranty, covenant or
agreement not expressly set forth in this Agreement shall affect or be used to interpret, change or restrict, the express terms and provisions of this Agreement, provided, however, in any event, this Agreement shall be subject to and governed by the
Plan. 
  

	 	20.	MODIFICATIONS AND AMENDMENTS. 

 The terms and provisions of this Agreement may be
modified or amended as provided in the Plan. 
  

	 	21.	WAIVERS AND CONSENTS. 

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

	 	22.	DATA PRIVACY. 

 By entering into this Agreement, the Participant: (i) authorizes the
Company and each Affiliate, and any agent of the Company or any Affiliate administering the Plan or providing Plan recordkeeping services, to disclose to the Company or any of its Affiliates such information and data as the Company or any such
Affiliate shall request in order to facilitate the grant of options and the administration of the Plan; (ii) to the extent permitted by law waives any data privacy rights he or she may have with respect to such information; and
(iii) authorizes the Company and each Affiliate to store and transmit such information in electronic form for the purposes set forth in this Agreement. 

[REMAINDER OF PAGE INTENTIONALLY LEFT BLANK] 

  
 13 

 Exhibit A 

NOTICE OF EXERCISE OF STOCK OPTION 

[Form for Unregistered Shares] 
 To:
Synlogic, Inc. 
 Ladies and Gentlemen: 
 I
hereby exercise my Stock Option to purchase                  shares (the “Shares”) of the common stock, $0.0001 par value, of Synlogic, Inc. (the
“Company”), at the exercise price of $[            ] per share, pursuant to and subject to the terms of that certain Stock Option Agreement between the undersigned and the Company
dated [            ], 20[    ]. 
 I am aware that the
Shares have not been registered under the Securities Act of 1933, as amended (the “1933 Act”), or any state securities laws. I understand that the reliance by the Company on exemptions under the 1933 Act is predicated in part upon the
truth and accuracy of the statements by me in this Notice of Exercise. 
 I hereby represent and warrant that (1) I have been furnished
with all information which I deem necessary to evaluate the merits and risks of the purchase of the Shares; (2) I have had the opportunity to ask questions concerning the Shares and the Company and all questions posed have been answered to my
satisfaction; (3) I have been given the opportunity to obtain any additional information I deem necessary to verify the accuracy of any information obtained concerning the Shares and the Company; and (4) I have such knowledge and
experience in financial and business matters that I am able to evaluate the merits and risks of purchasing the Shares and to make an informed investment decision relating thereto. 

I hereby represent and warrant that I am purchasing the Shares for my own personal account for investment and not with a view to the sale or
distribution of all or any part of the Shares. 
 I understand that because the Shares have not been registered under the 1933 Act, I must
continue to bear the economic risk of the investment for an indefinite time and the Shares cannot be sold unless the Shares are subsequently registered under applicable federal and state securities laws or an exemption from such registration
requirements is available. 
 I agree that I will in no event sell or distribute or otherwise dispose of all or any part of the Shares
unless (1) there is an effective registration statement under the 1933 Act and applicable state securities laws covering any such transaction involving the Shares or (2) the Company receives an opinion of my legal counsel (concurred in by
legal counsel for the Company) stating that such transaction is exempt from registration or the Company otherwise satisfies itself that such transaction is exempt from registration. 

  
 Exhibit A-1 

 I consent to the placing of a legend on my certificate for the Shares stating that the Shares
have not been registered and setting forth the restrictions on transfer contemplated hereby and to the placing of a stop transfer order on the books of the Company and with any transfer agents against the Shares until the Shares may be legally
resold or distributed without restriction. 
 I understand that at the present time Rule 144 of the Securities and Exchange Commission (the
“SEC”) may not be relied on for the resale or distribution of the Shares by me. I understand that the Company has no obligation to me to register the sale of the Shares with the SEC and has not represented to me that it will register the
sale of the Shares. 
 I understand the terms and restrictions on the right to dispose of the Shares set forth in the 2017 Stock Incentive
Plan and the Stock Option Agreement, both of which I have carefully reviewed. I consent to the placing of a legend on my certificate for the Shares referring to such restriction and the placing of stop transfer orders until the Shares may be
transferred in accordance with the terms of such restrictions. 
 I have considered the Federal, state and local income tax implications of
the exercise of my Option and the purchase and subsequent sale of the Shares. 
 I am paying the option exercise price for the Shares as
follows: 
  
  

Please issue the Shares (check one): 

☐  to me; or 

☐  to me and
                                , as joint tenants with right of survivorship 

and mail the certificate to me at the following address: 
  

 
  

 
  

 

  
 Exhibit A-2 

 My mailing address for shareholder communications, if different from the address listed above is:

  
  

 
  

 
  

 

	
	Very truly yours,
	
	   

	Participant (signature)
	
	   

	Print Name
	
	   

	Date
	
	   

	Social Security Number

  
 Exhibit A-3 

 Exhibit B 

NOTICE OF EXERCISE OF STOCK OPTION 

[Form for Shares Registered in the United States] 

To: Synlogic, Inc. 
 IMPORTANT NOTICE: This form of
Notice of Exercise may only be used at such time as the Company has filed a Registration Statement with the Securities and Exchange Commission under which the issuance of the Shares for which this exercise is being made is registered and such
Registration Statement remains effective. 
 Ladies and Gentlemen: 

I hereby exercise my Stock Option to purchase
                   shares (the “Shares”) of the common stock, $0.0001 par value, of Synlogic, Inc. (the “Company”), at the exercise
price of $                 per share, pursuant to and subject to the terms of that Stock Option Grant Notice dated
                              , 20[    ]. 

I understand the nature of the investment I am making and the financial risks thereof. I am aware that it is my responsibility to have
consulted with competent tax and legal advisors about the relevant national, state and local income tax and securities laws affecting the exercise of the Option and the purchase and subsequent sale of the Shares. 

I am paying the option exercise price for the Shares as follows: 

 
  

Please issue the Shares (check one): 

☐  to me; or 

☐  to me and
                                , as joint tenants with right of survivorship,

 at the following address: 
  

 
  

 
  

 

  
 Exhibit B-1 

 My mailing address for shareholder communications, if different from the address listed above,
is: 
  
  

 
  

 
  

 

	
	Very truly yours,
	
	   

	        Participant (signature)
	
	   

	        Print Name
	
	   

	        Date
	
	   

	        Social Security Number

  
 Exhibit B-2

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