Document:

EX-4.1

 Exhibit 4.1 

AMENDED AND RESTATED INVESTORS’ RIGHTS AGREEMENT 

THIS AMENDED AND RESTATED INVESTORS’ RIGHTS AGREEMENT is made as of the 19th day of December, 2014, by and among Seres Health, Inc., a
Delaware corporation (the “Company”), and each of the investors listed on Schedule A hereto, each of which is referred to in this Agreement as an “Investor.” 

RECITALS 

WHEREAS, certain of the Investors (the “Existing Investors”) possess registration rights, information rights, rights
of first offer, and other rights pursuant to an Amended and Restated Investors’ Rights Agreement dated as of November 24, 2014, between the Company and such Investors (as amended, the “Prior Agreement”); 

WHEREAS, the Existing Investors desire to amend and restate the Prior Agreement in its entirety and to accept the rights created
pursuant to this Agreement in lieu of the rights granted to them under the Prior Agreement; and 
 WHEREAS, one of the Investors is a
party to that certain Series D Preferred Stock Purchase Agreement of even date herewith between the Company and such Investor (the “Purchase Agreement”), under which certain of the Company’s and such Investor’s obligations
are conditioned upon the execution and delivery of this Agreement by the parties hereto; 
 NOW, THEREFORE, the Company and the
Existing Investors hereby agree to amend and restate the Prior Agreement in its entirety as set forth herein, and all of the parties hereto further agree as follows: 

1. Definitions. For purposes of this Agreement: 

1.1 “Affiliate” means, with respect to any specified Person, any other Person who, directly or indirectly, controls, is
controlled by, or is under common control with such Person, including without limitation any general partner, managing member, officer or director of such Person or any venture capital or other investment fund now or hereafter existing that is
controlled by one or more general partners or managing members of, or shares the same management company or investment advisor with, such Person. 

1.2 “Common Stock” means shares of the Company’s common stock, par value $0.001 per share. 

1.3 “Damages” means any loss, damage, or liability (joint or several) to which a party hereto may become subject under the
Securities Act, the Exchange Act, or other federal or state law, insofar as such loss, damage, or liability (or any action in respect thereof) arises out of or is based upon (i) any untrue statement or alleged untrue statement of a material
fact contained in any registration statement of the Company, including any preliminary prospectus or final prospectus contained therein or any amendments or supplements thereto; (ii) an omission or alleged omission to state therein a material
fact required to be stated therein, or necessary to make the statements therein not misleading; or (iii) any violation or alleged violation by the indemnifying party (or any of its agents or Affiliates) of the Securities Act, the Exchange Act,
any state securities law, or any rule or regulation promulgated under the Securities Act, the Exchange Act, or any state securities law. 

 1.4 “Derivative Securities” means any securities or rights convertible into, or
exercisable or exchangeable for (in each case, directly or indirectly), Common Stock, including options and warrants. 
 1.5
“Exchange Act” means the Securities Exchange Act of 1934, as amended, and the rules and regulations promulgated thereunder. 

1.6 “Excluded Registration” means (i) a registration relating to the sale of securities to employees of the Company or a
subsidiary pursuant to a stock option, stock purchase, or similar plan; (ii) a registration relating to an SEC Rule 145 transaction; (iii) a registration on any form that does not include substantially the same information as would be
required to be included in a registration statement covering the sale of the Registrable Securities; or (iv) a registration in which the only Common Stock being registered is Common Stock issuable upon conversion of debt securities that are
also being registered. 
 1.7 “Form S-1” means such form under the Securities Act as in effect on the date hereof or any
successor registration form under the Securities Act subsequently adopted by the SEC. 
 1.8 “Form S-3” means such form
under the Securities Act as in effect on the date hereof or any registration form under the Securities Act subsequently adopted by the SEC that permits incorporation of substantial information by reference to other documents filed by the Company
with the SEC. 
 1.9 “GAAP” means generally accepted accounting principles in the United States. 

1.10 “Holder” means any holder of Registrable Securities who is a party to this Agreement. 

1.11 “Immediate Family Member” means a child, stepchild, grandchild, parent, stepparent, grandparent, spouse, sibling,
mother-in-law, father-in-law, son-in-law, daughter-in-law, brother-in-law, or sister-in-law, including adoptive relationships, of a natural person referred to herein. 

1.12 “Initiating Holders” means, collectively, Holders who properly initiate a registration request under this Agreement.

 1.13 “IPO” means the Company’s first underwritten public offering of its Common Stock under the Securities Act.

 1.14 “Key Employee” means any executive-level employee (including division director and vice president-level positions)
as well as any employee who, either alone or in concert with others, develops, invents, programs, or designs any Company Intellectual Property (as defined in the Purchase Agreement). 

  
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 1.15 “Major Investor” means (i) any Investor that, individually or together
with such Investor’s Affiliates, holds at least 281,000 shares of Registrable Securities (as adjusted for any stock split, stock dividend, combination, or other recapitalization or reclassification effected after the date hereof) and
(ii) any Investor that, individually or together with such Investor’s Affiliates, holds at least 164,430 shares of Series C Preferred Stock (as adjusted for any stock split, stock dividend, combination, or other recapitalization or
reclassification effected after the date hereof). 
 1.16 “New Securities” means, collectively, equity securities of the
Company, whether or not currently authorized, as well as rights, options, or warrants to purchase such equity securities, or securities of any type whatsoever that are, or may become, convertible or exchangeable into or exercisable for such equity
securities. 
 1.17 “Person” means any individual, corporation, partnership, trust, limited liability company, association
or other entity. 
 1.18 “Preferred Director” means the director of the Company that the holders of record of the Series A
Preferred Stock, Series B Preferred Stock and Series C Preferred Stock are entitled to elect pursuant to the Company’s Certificate of Incorporation. 

1.19 “Preferred Stock” means shares of Series A Preferred Stock, Series A-2 Preferred Stock, Series B Preferred Stock, Series
C Preferred Stock and Series D Preferred Stock. 
 1.20 “Registrable Securities” means (i) the Common Stock issuable
or issued upon conversion of the Preferred Stock; (ii) the Common Stock held by Flagship VentureLabs IV LLC as of the date of the Prior Agreement (including without limitation and for the avoidance of doubt the Common Stock acquired by
Nestlé Health Science US Holdings, Inc. (“Nestlé”) pursuant to the Stock Purchase Agreement dated as of December 19, 2014, by and between Flagship VentureLabs IV LLC and Nestlé (the “Common Stock
Purchase Agreement”); (iii) any Common Stock issued as (or issuable upon the conversion or exercise of any warrant, right, or other security that is issued as) a dividend or other distribution with respect to, or in exchange for or in
replacement of, the shares referenced in clause (i) and (ii) above; and (iv) the Common Stock issued or issuable to Comerica Ventures Incorporated, its successors and assigns, upon conversion of shares of any securities
of the Company (including without limitation Series A-2 Preferred Stock) issuable upon exercise of the warrant issued by the Company to Comerica Bank pursuant to that certain Loan and Security Agreement, dated as of September 9, 2013, between
the Company and Comerica Bank, as may be amended and/or restated from time to time; excluding in all cases, however, any Registrable Securities sold by a Person in a transaction in which the applicable rights under this Agreement are not assigned
pursuant to Subsection 6.1, and excluding for purposes of Section 2 any shares for which registration rights have terminated pursuant to Subsection 2.13 of this Agreement. 

1.21 “Registrable Securities then outstanding” means the number of shares determined by adding the number of shares of
outstanding Common Stock that are Registrable Securities and the number of shares of Common Stock issuable (directly or indirectly) pursuant to then exercisable and/or convertible securities that are Registrable Securities. 

  
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 1.22 “Restricted Securities” means the securities of the Company required to
bear the legend set forth in Subsection 2.12(b) hereof. 
 1.23 “SEC” means the Securities and Exchange Commission.

 1.24 “SEC Rule 144” means Rule 144 promulgated by the SEC under the Securities Act. 

1.25 “SEC Rule 145” means Rule 145 promulgated by the SEC under the Securities Act. 

1.26 “Securities Act” means the Securities Act of 1933, as amended, and the rules and regulations promulgated thereunder.

 1.27 “Selling Expenses” means all underwriting discounts, selling commissions, and stock transfer taxes applicable to
the sale of Registrable Securities, and fees and disbursements of counsel for any Holder, except for the fees and disbursements of the Selling Holder Counsel borne and paid by the Company as provided in Subsection 2.6. 

1.28 “Series A Preferred Stock” means shares of the Company’s Series A Preferred Stock, par value $0.001 per share. 

1.29 “Series A-2 Preferred Stock” means shares of the Company’s Series A-2 Preferred Stock, par value $0.001 per share.

 1.30 “Series B Preferred Stock” means shares of the Company’s Series B Preferred Stock, par value $0.001 per share.

 1.31 “Series C Preferred Stock” means shares of the Company’s Series C Preferred Stock, par value $0.001 per share.

 1.32 “Series C Purchase Agreement” means that certain Series C Preferred Stock Purchase Agreement, dated as of
November 24, 2014, by and among the Company and the purchasers named therein. 
 1.33 “Series D Preferred Stock” means
shares of the Company’s Series D Preferred Stock, par value $0.001 per share. 
 1.34 “Series D-1 Preferred Stock”
means shares of the Company’s Series D-1 Preferred Stock, par value $0.001 per share. 
 2. Registration Rights. The Company
covenants and agrees as follows: 
 2.1 Demand Registration. 

(a) Form S-1 Demand. If at any time after the earlier of (i) five (5) years after the date of this Agreement or
(ii) one hundred eighty (180) days after the effective date of the registration statement for the IPO, the Company receives a request from Holders of a 

  
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majority of the Registrable Securities then outstanding that the Company file a Form S-1 registration statement for which the anticipated aggregate offering price would exceed $10,000,000, then
the Company shall (i) within ten (10) days after the date such request is given, give notice thereof (the “Demand Notice”) to all Holders other than the Initiating Holders; and (ii) as soon as practicable, and in any
event within sixty (60) days after the date such request is given by the Initiating Holders, file a Form S-1 registration statement under the Securities Act covering all Registrable Securities that the Initiating Holders requested to be
registered and any additional Registrable Securities requested to be included in such registration by any other Holders, as specified by notice given by each such Holder to the Company within twenty (20) days of the date the Demand Notice is
given, and in each case, subject to the limitations of Subsection 2.1(c) and Subsection 2.3. 
 (b) Form S-3 Demand.
If at any time when it is eligible to use a Form S-3 registration statement, the Company receives a request from Holders of at least thirty percent (30%) of the Registrable Securities then outstanding that the Company file a Form S-3
registration statement with respect to outstanding Registrable Securities of such Holders having an anticipated aggregate offering price of at least $5,000,000, then the Company shall (i) within ten (10) days after the date such request is
given, give a Demand Notice to all Holders other than the Initiating Holders; and (ii) as soon as practicable, and in any event within forty-five (45) days after the date such request is given by the Initiating Holders, file a Form S-3
registration statement under the Securities Act covering all Registrable Securities requested to be included in such registration by any other Holders, as specified by notice given by each such Holder to the Company within twenty (20) days of
the date the Demand Notice is given, and in each case, subject to the limitations of Subsection 2.1(c) and Subsection 2.3. 

(c) Notwithstanding the foregoing obligations, if the Company furnishes to Holders requesting a registration pursuant to this Subsection
2.1 a certificate signed by the Company’s chief executive officer stating that in the good faith judgment of the Company’s Board of Directors it would be materially detrimental to the Company and its stockholders for such registration
statement to either become effective or remain effective for as long as such registration statement otherwise would be required to remain effective, because such action would (i) materially interfere with a significant acquisition, corporate
reorganization, or other similar transaction involving the Company; (ii) require premature disclosure of material information that the Company has a bona fide business purpose for preserving as confidential; or (iii) render the Company
unable to comply with requirements under the Securities Act or Exchange Act, then the Company shall have the right to defer taking action with respect to such filing, and any time periods with respect to filing or effectiveness thereof shall be
tolled correspondingly, for a period of not more than ninety (90) days after the request of the Initiating Holders is given; provided, however, that the Company may not invoke this right more than once in any twelve
(12) month period; and provided further that the Company shall not register any securities for its own account or that of any other stockholder during such ninety (90) day period other than an Excluded Registration. 

(d) The Company shall not be obligated to effect, or to take any action to effect, any registration pursuant to Subsection 2.1(a)
(i) during the period that is sixty (60) days before the Company’s good faith estimate of the date of filing of, and ending on a date that is one hundred eighty (180) days after the effective date of, a Company-initiated
registration, 

  
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provided, that the Company is actively employing in good faith commercially reasonable efforts to cause such registration statement to become effective; (ii) after the Company has
effected two registrations pursuant to Subsection 2.1(a); or (iii) if the Initiating Holders propose to dispose of shares of Registrable Securities that may be immediately registered on Form S-3 pursuant to a request made pursuant to
Subsection 2.1(b). The Company shall not be obligated to effect, or to take any action to effect, any registration pursuant to Subsection 2.1(b) (i) during the period that is thirty (30) days before the Company’s good
faith estimate of the date of filing of, and ending on a date that is ninety (90) days after the effective date of, a Company-initiated registration, provided, that the Company is actively employing in good faith commercially reasonable efforts
to cause such registration statement to become effective; or (ii) if the Company has effected two registrations pursuant to Subsection 2.1(b) within the twelve (12) month period immediately preceding the date of such request. A
registration shall not be counted as “effected” for purposes of this Subsection 2.1(d) until such time as the applicable registration statement has been declared effective by the SEC, unless the Initiating Holders withdraw their
request for such registration, elect not to pay the registration expenses therefor, and forfeit their right to one demand registration statement pursuant to Subsection 2.6, in which case such withdrawn registration statement shall be counted
as “effected” for purposes of this Subsection 2.1(d). 
 2.2 Company Registration. If the Company proposes to
register (including, for this purpose, a registration effected by the Company for stockholders other than the Holders) any of its securities under the Securities Act in connection with the public offering of such securities solely for cash (other
than in an Excluded Registration or the IPO), the Company shall, at such time, promptly give each Holder notice of such registration. Upon the request of each Holder given within twenty (20) days after such notice is given by the Company, the
Company shall, subject to the provisions of Subsection 2.3, cause to be registered all of the Registrable Securities that each such Holder has requested to be included in such registration. The Company shall have the right to terminate or
withdraw any registration initiated by it under this Subsection 2.2 before the effective date of such registration, whether or not any Holder has elected to include Registrable Securities in such registration. The expenses (other than Selling
Expenses) of such withdrawn registration shall be borne by the Company in accordance with Subsection 2.6. 
 2.3 Underwriting
Requirements. 
 (a) If, pursuant to Subsection 2.1, the Initiating Holders intend to distribute the Registrable Securities
covered by their request by means of an underwriting, they shall so advise the Company as a part of their request made pursuant to Subsection 2.1, and the Company shall include such information in the Demand Notice. The underwriter(s) will be
selected by a majority in interest of the Initiating Holders, subject only to the reasonable approval of the Company. In such event, the right of any Holder to include such Holder’s Registrable Securities in such registration shall be
conditioned upon such Holder’s participation in such underwriting and the inclusion of such Holder’s Registrable Securities in the underwriting to the extent provided herein. All Holders proposing to distribute their securities through
such underwriting shall (together with the Company as provided in Subsection 2.4(e)) enter into an underwriting agreement in customary form with the underwriter(s) selected for such underwriting. Notwithstanding any other provision of this
Subsection 2.3, if the managing underwriter(s) advise(s) the Initiating Holders in writing that marketing factors require a limitation on the number of shares to be underwritten, then the Initiating Holders shall so advise all Holders of
Registrable Securities that otherwise would be underwritten pursuant 

  
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hereto, and the number of Registrable Securities that may be included in the underwriting shall be allocated among such Holders of Registrable Securities, including the Initiating Holders, in
proportion (as nearly as practicable) to the number of Registrable Securities owned by each Holder or in such other proportion as shall mutually be agreed to by all such selling Holders; provided, however, that the number of
Registrable Securities held by the Holders to be included in such underwriting shall not be reduced unless all other securities are first entirely excluded from the underwriting. To facilitate the allocation of shares in accordance with the above
provisions, the Company or the underwriters may round the number of shares allocated to any Holder to the nearest 100 shares. 
 (b) In
connection with any offering involving an underwriting of shares of the Company’s capital stock pursuant to Subsection 2.2, the Company shall not be required to include any of the Holders’ Registrable Securities in such underwriting
unless the Holders accept the terms of the underwriting as agreed upon between the Company and its underwriters, and then only in such quantity as the underwriters in their sole discretion determine will not jeopardize the success of the offering by
the Company. If the total number of securities, including Registrable Securities, requested by stockholders to be included in such offering exceeds the number of securities to be sold (other than by the Company) that the underwriters in their
reasonable discretion determine is compatible with the success of the offering, then the Company shall be required to include in the offering only that number of such securities, including Registrable Securities, which the underwriters and the
Company in their sole discretion determine will not jeopardize the success of the offering. If the underwriters determine that less than all of the Registrable Securities requested to be registered can be included in such offering, then the
Registrable Securities that are included in such offering shall be allocated among the selling Holders in proportion (as nearly as practicable to) the number of Registrable Securities owned by each selling Holder or in such other proportions as
shall mutually be agreed to by all such selling Holders. To facilitate the allocation of shares in accordance with the above provisions, the Company or the underwriters may round the number of shares allocated to any Holder to the nearest 100
shares. Notwithstanding the foregoing, in no event shall (i) the number of Registrable Securities included in the offering be reduced unless all other securities (other than securities to be sold by the Company) are first entirely excluded from
the offering, and (ii) the number of Registrable Securities included in the offering be reduced below thirty percent (30%) of the total number of securities included in such offering. For purposes of the provision in this Subsection
2.3(b) concerning apportionment, for any selling Holder that is a partnership, limited liability company, or corporation, the partners, members, retired partners, retired members, stockholders, and Affiliates of such Holder, or the estates and
Immediate Family Members of any such partners, retired partners, members, and retired members and any trusts for the benefit of any of the foregoing Persons, shall be deemed to be a single “selling Holder,” and any pro rata reduction with
respect to such “selling Holder” shall be based upon the aggregate number of Registrable Securities owned by all Persons included in such “selling Holder,” as defined in this sentence. 

(c) For purposes of Subsection 2.1, a registration shall not be counted as “effected” if, as a result of an exercise of the
underwriter’s cutback provisions in Subsection 2.3(a), fewer than fifty percent (50%) of the total number of Registrable Securities that Holders have requested to be included in such registration statement are actually included.

  
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 2.4 Obligations of the Company. Whenever required under this Section 2 to
effect the registration of any Registrable Securities, the Company shall, as expeditiously as reasonably possible: 
 (a) prepare and file
with the SEC a registration statement with respect to such Registrable Securities and use its commercially reasonable efforts to cause such registration statement to become effective and, upon the request of the Holders of a majority of the
Registrable Securities registered thereunder, keep such registration statement effective for a period of up to one hundred twenty (120) days or, if earlier, until the distribution contemplated in the registration statement has been completed;
provided, however, that (i) such one hundred twenty (120) day period shall be extended for a period of time equal to the period the Holder refrains, at the request of an underwriter of Common Stock (or other securities) of
the Company, from selling any securities included in such registration, and (ii) in the case of any registration of Registrable Securities on Form S-3 that are intended to be offered on a continuous or delayed basis, subject to compliance with
applicable SEC rules, such one hundred twenty (120) day period shall be extended, if necessary, to keep the registration statement effective until all such Registrable Securities are sold; 

(b) prepare and file with the SEC such amendments and supplements to such registration statement, and the prospectus used in connection with
such registration statement, as may be necessary to comply with the Securities Act in order to enable the disposition of all securities covered by such registration statement; 

(c) furnish to the selling Holders such numbers of copies of a prospectus, including a preliminary prospectus, as required by the Securities
Act, and such other documents as the Holders may reasonably request in order to facilitate their disposition of their Registrable Securities; 

(d) use its commercially reasonable efforts to register and qualify the securities covered by such registration statement under such other
securities or blue-sky laws of such jurisdictions as shall be reasonably requested by the selling Holders; provided that the Company shall not be required to qualify to do business or to file a general consent to service of process in any such
states or jurisdictions, unless the Company is already subject to service in such jurisdiction and except as may be required by the Securities Act; 

(e) in the event of any underwritten public offering, enter into and perform its obligations under an underwriting agreement, in usual and
customary form, with the underwriter(s) of such offering; 
 (f) use its commercially reasonable efforts to cause all such Registrable
Securities covered by such registration statement to be listed on a national securities exchange or trading system and each securities exchange and trading system (if any) on which similar securities issued by the Company are then listed; 

(g) provide a transfer agent and registrar for all Registrable Securities registered pursuant to this Agreement and provide a CUSIP number
for all such Registrable Securities, in each case not later than the effective date of such registration; 

  
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 (h) promptly make available for inspection by the selling Holders, any managing underwriter(s)
participating in any disposition pursuant to such registration statement, and any attorney or accountant or other agent retained by any such underwriter or selected by the selling Holders, all financial and other records, pertinent corporate
documents, and properties of the Company, and cause the Company’s officers, directors, employees, and independent accountants to supply all information reasonably requested by any such seller, underwriter, attorney, accountant, or agent, in
each case, as necessary or advisable to verify the accuracy of the information in such registration statement and to conduct appropriate due diligence in connection therewith; 

(i) notify each selling Holder, promptly after the Company receives notice thereof, of the time when such registration statement has been
declared effective or a supplement to any prospectus forming a part of such registration statement has been filed; and 
 (j) after such
registration statement becomes effective, notify each selling Holder of any request by the SEC that the Company amend or supplement such registration statement or prospectus. 

In addition, the Company shall ensure that, at all times after any registration statement covering a public offering of securities of the
Company under the Securities Act shall have become effective, its insider trading policy shall provide that the Company’s directors may implement a trading program under Rule 10b5-1 of the Exchange Act. 

2.5 Furnish Information. It shall be a condition precedent to the obligations of the Company to take any action pursuant to this
Section 2 with respect to the Registrable Securities of any selling Holder that such Holder shall furnish to the Company such information regarding itself, the Registrable Securities held by it, and the intended method of disposition of
such securities as is reasonably required to effect the registration of such Holder’s Registrable Securities. 
 2.6 Expenses of
Registration. All expenses (other than Selling Expenses) incurred in connection with registrations, filings, or qualifications pursuant to Section 2, including all registration, filing, and qualification fees; printers’ and
accounting fees; fees and disbursements of counsel for the Company; and the reasonable fees and disbursements of one counsel for the selling Holders selected by the Holders of a majority of the Registrable Securities to be registered
(“Selling Holder Counsel”), shall be borne and paid by the Company; provided, however, that the Company shall not be required to pay for any expenses of any registration proceeding begun pursuant to Subsection
2.1 if the registration request is subsequently withdrawn at the request of the Holders of a majority of the Registrable Securities to be registered (in which case all selling Holders shall bear such expenses pro rata based upon the number of
Registrable Securities that were to be included in the withdrawn registration), unless the Holders of a majority of the Registrable Securities agree to forfeit their right to one registration pursuant to Subsection 2.1(a) or Subsection
2.1(b), as the case may be; provided further that if, at the time of such withdrawal, the Holders shall have learned of a material adverse change in the condition, business, or prospects of the Company from that known to the
Holders at the time of their request and have withdrawn the request with reasonable promptness after learning of such information then the Holders shall not be required to pay any of such 

  
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expenses and shall not forfeit their right to one registration pursuant to Subsection 2.1(a) or Subsection 2.1(b). All Selling Expenses relating to Registrable Securities registered
pursuant to this Section 2 shall be borne and paid by the Holders pro rata on the basis of the number of Registrable Securities registered on their behalf. 

2.7 Delay of Registration. No Holder shall have any right to obtain or seek an injunction restraining or otherwise delaying any
registration pursuant to this Agreement as the result of any controversy that might arise with respect to the interpretation or implementation of this Section 2. 

2.8 Indemnification. If any Registrable Securities are included in a registration statement under this Section 2: 

(a) To the extent permitted by law, the Company will indemnify and hold harmless each selling Holder, and the partners, members, officers,
directors, and stockholders of each such Holder; legal counsel, accountants and investment advisors for each such Holder; any underwriter (as defined in the Securities Act) for each such Holder; and each Person, if any, who controls such Holder or
underwriter within the meaning of the Securities Act or the Exchange Act, against any Damages, and the Company will pay to each such Holder, underwriter, controlling Person, or other aforementioned Person any legal or other expenses reasonably
incurred thereby in connection with investigating or defending any claim or proceeding from which Damages may result, as such expenses are incurred; provided, however, that the indemnity agreement contained in this Subsection
2.8(a) shall not apply to amounts paid in settlement of any such claim or proceeding if such settlement is effected without the consent of the Company, which consent shall not be unreasonably withheld, nor shall the Company be liable for any
Damages to the extent that they arise out of or are based upon actions or omissions made in reliance upon and in conformity with written information furnished by or on behalf of any such Holder, underwriter, controlling Person, or other
aforementioned Person expressly for use in connection with such registration. 
 (b) To the extent permitted by law, each selling Holder,
severally and not jointly, will indemnify and hold harmless the Company, and each of its directors, each of its officers who has signed the registration statement, each Person (if any), who controls the Company within the meaning of the Securities
Act, legal counsel and accountants for the Company, any underwriter (as defined in the Securities Act), any other Holder selling securities in such registration statement, and any controlling Person of any such underwriter or other Holder, against
any Damages, in each case only to the extent that such Damages arise out of or are based upon actions or omissions made in reliance upon and in conformity with written information furnished by or on behalf of such selling Holder expressly for use in
connection with such registration; and each such selling Holder will pay to the Company and each other aforementioned Person any legal or other expenses reasonably incurred thereby in connection with investigating or defending any claim or
proceeding from which Damages may result, as such expenses are incurred; provided, however, that the indemnity agreement contained in this Subsection 2.8(b) shall not apply to amounts paid in settlement of any such claim or
proceeding if such settlement is effected without the consent of the Holder, which consent shall not be unreasonably withheld; and provided further that in no event shall the aggregate amounts payable by any Holder by way of indemnity
or contribution under Subsections 2.8(b) and 2.8(d) exceed the proceeds from the offering received by such Holder (net of any Selling Expenses paid by such Holder), except in the case of fraud or willful misconduct by such Holder. 

  
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 (c) Promptly after receipt by an indemnified party under this Subsection 2.8 of notice of
the commencement of any action (including any governmental action) for which a party may be entitled to indemnification hereunder, such indemnified party will, if a claim in respect thereof is to be made against any indemnifying party under this
Subsection 2.8, give the indemnifying party notice of the commencement thereof. The indemnifying party shall have the right to participate in such action and, to the extent the indemnifying party so desires, participate jointly with any other
indemnifying party to which notice has been given, and to assume the defense thereof with counsel mutually satisfactory to the parties; provided, however, that an indemnified party (together with all other indemnified parties that may
be represented without conflict by one counsel) shall have the right to retain one separate counsel, with the fees and expenses to be paid by the indemnifying party, if representation of such indemnified party by the counsel retained by the
indemnifying party would be inappropriate due to actual or potential differing interests between such indemnified party and any other party represented by such counsel in such action. The failure to give notice to the indemnifying party within a
reasonable time of the commencement of any such action shall relieve such indemnifying party of any liability to the indemnified party under this Subsection 2.8, to the extent that such failure materially prejudices the indemnifying
party’s ability to defend such action. The failure to give notice to the indemnifying party will not relieve it of any liability that it may have to any indemnified party otherwise than under this Subsection 2.8. 

(d) To provide for just and equitable contribution to joint liability under the Securities Act in any case in which either (i) any party
otherwise entitled to indemnification hereunder makes a claim for indemnification pursuant to this Subsection 2.8 but it is judicially determined (by the entry of a final judgment or decree by a court of competent jurisdiction and the
expiration of time to appeal or the denial of the last right of appeal) that such indemnification may not be enforced in such case, notwithstanding the fact that this Subsection 2.8 provides for indemnification in such case, or
(ii) contribution under the Securities Act may be required on the part of any party hereto for which indemnification is provided under this Subsection 2.8, then, and in each such case, such parties will contribute to the aggregate
losses, claims, damages, liabilities, or expenses to which they may be subject (after contribution from others) in such proportion as is appropriate to reflect the relative fault of each of the indemnifying party and the indemnified party in
connection with the statements, omissions, or other actions that resulted in such loss, claim, damage, liability, or expense, as well as to reflect any other relevant equitable considerations. The relative fault of the indemnifying party and of the
indemnified party shall be determined by reference to, among other things, whether the untrue or allegedly untrue statement of a material fact, or the omission or alleged omission of a material fact, relates to information supplied by the
indemnifying party or by the indemnified party and the parties’ relative intent, knowledge, access to information, and opportunity to correct or prevent such statement or omission; provided, however, that, in any such case,
(x) no Holder will be required to contribute any amount in excess of the public offering price of all such Registrable Securities offered and sold by such Holder pursuant to such registration statement, and (y) no Person guilty of
fraudulent misrepresentation (within the meaning of Section 11(f) of the Securities Act) will be entitled to contribution from any Person who was not guilty of such 

  
 11 

 
fraudulent misrepresentation; and provided further that in no event shall a Holder’s liability pursuant to this Subsection 2.8(d), when combined with the amounts paid or
payable by such Holder pursuant to Subsection 2.8(b), exceed the proceeds from the offering received by such Holder (net of any Selling Expenses paid by such Holder), except in the case of willful misconduct or fraud by such Holder. 

(e) Notwithstanding the foregoing, to the extent that the provisions on indemnification and contribution contained in the underwriting
agreement entered into in connection with the underwritten public offering are in conflict with the foregoing provisions, the provisions in the underwriting agreement shall control. 

(f) Unless otherwise superseded by an underwriting agreement entered into in connection with the underwritten public offering, the
obligations of the Company and Holders under this Subsection 2.8 shall survive the completion of any offering of Registrable Securities in a registration under this Section 2, and otherwise shall survive the termination of this
Agreement. 
 2.9 Reports Under Exchange Act. With a view to making available to the Holders the benefits of SEC Rule 144 and any
other rule or regulation of the SEC that may at any time permit a Holder to sell securities of the Company to the public without registration or pursuant to a registration on Form S-3, the Company shall: 

(a) make and keep available adequate current public information, as those terms are understood and defined in SEC Rule 144, at all times
after the effective date of the registration statement filed by the Company for the IPO; 
 (b) use commercially reasonable efforts to file
with the SEC in a timely manner all reports and other documents required of the Company under the Securities Act and the Exchange Act (at any time after the Company has become subject to such reporting requirements); and 

(c) furnish to any Holder, so long as the Holder owns any Registrable Securities, forthwith upon request (i) to the extent accurate, a
written statement by the Company that it has complied with the reporting requirements of SEC Rule 144 (at any time after ninety (90) days after the effective date of the registration statement filed by the Company for the IPO), the Securities
Act, and the Exchange Act (at any time after the Company has become subject to such reporting requirements), or that it qualifies as a registrant whose securities may be resold pursuant to Form S 3 (at any time after the Company so qualifies);
(ii) a copy of the most recent annual or quarterly report of the Company and such other reports and documents so filed by the Company; and (iii) such other information as may be reasonably requested in availing any Holder of any rule or
regulation of the SEC that permits the selling of any such securities without registration (at any time after the Company has become subject to the reporting requirements under the Exchange Act) or pursuant to Form S-3 (at any time after the Company
so qualifies to use such form). 
 2.10 Limitations on Subsequent Registration Rights. From and after the date of this Agreement, the
Company shall not, without the prior written consent of the Holders of a 

  
 12 

 
majority of the Registrable Securities then outstanding, enter into any agreement with any holder or prospective holder of any securities of the Company that (i) would provide to such holder
the right to include securities in any registration on other than a subordinate basis after all Holders have had the opportunity to include in the registration and offering all shares of Registrable Securities that they wish to so include or
(ii) allow such holder or prospective holder to initiate a demand for registration of any securities held by such holder or prospective holder. 

2.11 “Market Stand off” Agreement. Each Holder hereby agrees that it will not, without the prior written consent of the
managing underwriter, during the period commencing on the date of the final prospectus relating to the IPO and ending on the date specified by the Company and the managing underwriter (such period not to exceed one hundred eighty (180) days),
(i) lend; offer; pledge; sell; contract to sell; sell any option or contract to purchase; purchase any option or contract to sell; grant any option, right, or warrant to purchase; or otherwise transfer or dispose of, directly or indirectly, any
shares of Common Stock or any securities convertible into or exercisable or exchangeable (directly or indirectly) for Common Stock held immediately before the effective date of the registration statement for such offering or (ii) enter into any
swap or other arrangement that transfers to another, in whole or in part, any of the economic consequences of ownership of such securities, whether any such transaction described in clause (i) or (ii) above is to be settled by delivery of
Common Stock or other securities, in cash, or otherwise. The foregoing provisions of this Subsection 2.11 shall apply only to the IPO, shall not apply to the sale of any shares to an underwriter pursuant to an underwriting agreement for such
IPO, and shall be applicable to the Holders only if all officers and directors of the Company and holders of at least one percent (1%) of the outstanding Common Stock (after giving effect to conversion into Common Stock of all outstanding
shares of Preferred Stock) are subject to the same restrictions. The underwriters in connection with such registration are intended third party beneficiaries of this Subsection 2.11 and shall have the right, power, and authority to enforce
the provisions hereof as though they were a party hereto. Each Holder further agrees to execute such agreements as may be reasonably requested by the underwriters in connection with such registration that are consistent with this Subsection
2.11 or that are necessary to give further effect thereto. 
 2.12 Restrictions on Transfer. 

(a) The Preferred Stock and the Registrable Securities shall not be sold, pledged, or otherwise transferred in violation of this Agreement,
and the Company shall not recognize and shall issue stop-transfer instructions to its transfer agent with respect to any such sale, pledge, or transfer, except upon the conditions specified in this Agreement, which conditions are intended to ensure
compliance with the provisions of the Securities Act. A transferring Holder will cause any proposed purchaser, pledgee, or transferee of the Preferred Stock and the Registrable Securities held by such Holder to agree to take and hold such securities
subject to the provisions and upon the conditions specified in this Agreement. Notwithstanding the foregoing, the Company shall not require any transferee of Registrable Securities pursuant to an effective registration statement under the Securities
Act or, following the IPO, SEC Rule 144 to be bound by the terms of this Subsection 2.12 if the transferred securities do not remain Registrable Securities hereunder following such transfer. 

(b) Each certificate or instrument representing (i) the Preferred Stock, (ii) the Registrable Securities, and (iii) any other
securities issued in respect of the securities referenced in clauses (i) and (ii), upon any stock split, stock dividend, recapitalization, merger, consolidation, or similar event, shall (unless otherwise permitted by the provisions of
Subsection 2.12(c)) be stamped or otherwise imprinted with a legend substantially in the following form: 

  
 13 

 THE SECURITIES REPRESENTED HEREBY HAVE BEEN ACQUIRED FOR INVESTMENT AND HAVE NOT
BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933. SUCH SHARES MAY NOT BE SOLD, PLEDGED, OR TRANSFERRED IN THE ABSENCE OF SUCH REGISTRATION OR A VALID EXEMPTION FROM THE REGISTRATION AND PROSPECTUS DELIVERY REQUIREMENTS OF SAID ACT. 

THE SECURITIES REPRESENTED HEREBY MAY BE TRANSFERRED ONLY IN ACCORDANCE WITH THE TERMS OF AN AGREEMENT BETWEEN THE COMPANY AND
THE STOCKHOLDER, A COPY OF WHICH IS ON FILE WITH THE SECRETARY OF THE COMPANY. 
 The Holders consent to the Company making a notation in
its records and giving instructions to any transfer agent of the Restricted Securities in order to implement the restrictions on transfer set forth in this Subsection 2.12. 

(c) The holder of each certificate representing Restricted Securities, by acceptance thereof, agrees to comply in all respects with the
provisions of this Section 2. Before any proposed sale, pledge, or transfer of any Restricted Securities, unless there is in effect a registration statement under the Securities Act covering the proposed transaction or, following the
IPO, the transfer is made pursuant to SEC Rule 144, the Holder thereof shall give notice to the Company of such Holder’s intention to effect such sale, pledge, or transfer. Each such notice shall describe the manner and circumstances of the
proposed sale, pledge, or transfer in sufficient detail and, if reasonably requested by the Company, shall be accompanied at such Holder’s expense by either (i) a written opinion of legal counsel who shall, and whose legal opinion shall,
be reasonably satisfactory to the Company, addressed to the Company, to the effect that the proposed transaction may be effected without registration under the Securities Act; (ii) a “no action” letter from the SEC to the effect that
the proposed sale, pledge, or transfer of such Restricted Securities without registration will not result in a recommendation by the staff of the SEC that action be taken with respect thereto; or (iii) any other evidence reasonably satisfactory
to counsel to the Company to the effect that the proposed sale, pledge, or transfer of the Restricted Securities may be effected without registration under the Securities Act, whereupon the Holder of such Restricted Securities shall be entitled to
sell, pledge, or transfer such Restricted Securities in accordance with the terms of the notice given by the Holder to the Company. The Company will not require such a legal opinion or “no action” letter (x) in any transaction in
compliance with SEC Rule 144 or (y) in any transaction in which such Holder distributes Restricted Securities to an Affiliate of such Holder for no consideration; provided that, with respect to transfers following the IPO under the foregoing
clause (y), each transferee agrees in writing to be subject to the terms of this Subsection 2.12. Each certificate or instrument evidencing the Restricted Securities transferred as above provided shall bear, except if such transfer is made
pursuant to SEC Rule 144 or pursuant to an effective registration statement under the Securities Act, the appropriate restrictive legend set forth in Subsection 2.12(b), except that such certificate shall not bear such restrictive legend if,
in the opinion of counsel for such Holder and the Company, such legend is not required in order to establish compliance with any provisions of the Securities Act. 

  
 14 

 2.13 Termination of Registration Rights. The right of any Holder to request registration
or inclusion of Registrable Securities in any registration pursuant to Subsection 2.1 or Subsection 2.2 shall terminate upon the earliest to occur of: 

(a) the closing of a Deemed Liquidation Event, as such term is defined in the Company’s Certificate of Incorporation; 

(b) such time after the IPO as SEC Rule 144 or another similar exemption under the Securities Act is available for the sale of all of such
Holder’s shares without limitation during a three-month period without registration; and 
 (c) the fifth (5th) anniversary of the IPO. 
 3. Information Rights. 

3.1 Delivery of Financial Statements. The Company shall deliver to each Major Investor and each Investor owning shares of Series C
Preferred Stock purchased from the Company pursuant to the Series C Purchase Agreement, provided that the Board of Directors has not reasonably determined that such Major Investor or Investor, as the case may be, is a competitor of the
Company: 
 (a) as soon as practicable, but in any event within one hundred twenty (120) days after the end of each fiscal year of the
Company, (i) a balance sheet as of the end of such year, (ii) statements of income and of cash flows for such year and (iii) a statement of stockholders’ equity as of the end of such year, all such financial statements audited
and certified by independent public accountants selected by the Company and approved by the Board of Directors, including the Preferred Director; 

(b) as soon as practicable, but in any event within forty-five (45) days after the end of each of the first three (3) quarters of
each fiscal year of the Company, unaudited statements of income and of cash flows for such fiscal quarter, and an unaudited balance sheet and a statement of stockholders’ equity as of the end of such fiscal quarter, all prepared in accordance
with GAAP (except that such financial statements may (i) be subject to normal year-end audit adjustments and (ii) not contain all notes thereto that may be required in accordance with GAAP); 

(c) as soon as practicable, but in any event within forty-five (45) days after the end of each of the first three (3) quarters of
each fiscal year of the Company, a statement showing the number of shares of each class and series of capital stock and securities convertible into or exercisable for shares of capital stock outstanding at the end of the period, the Common Stock
issuable upon conversion or exercise of any outstanding securities convertible or exercisable for Common Stock and the exchange ratio or exercise price applicable thereto, and the number of shares of issued stock options and stock options not yet
issued but reserved for issuance, if any, all in sufficient detail as to permit any Major Investor to calculate its percentage equity ownership in the Company, and certified by the chief financial officer or chief executive officer of the Company as
being true, complete, and correct; and 

  
 15 

 (d) such other information relating to the financial condition, business, prospects, or
corporate affairs of the Company as any Major Investor may from time to time reasonably request; provided, however, that the Company shall not be obligated under this Subsection 3.1 to provide information (i) that the
Company reasonably determines in good faith to be confidential information (unless covered by an enforceable confidentiality agreement, in form acceptable to the Company) or a trade secret or (ii) the disclosure of which would adversely affect
the attorney-client privilege between the Company and its counsel. 
 If, for any period, the Company has any subsidiary whose accounts are
consolidated with those of the Company, then in respect of such period the financial statements delivered pursuant to the foregoing sections shall be the consolidated and consolidating financial statements of the Company and all such consolidated
subsidiaries. 
 Notwithstanding anything else in this Subsection 3.1 to the contrary, the Company may cease providing the
information set forth in this Subsection 3.1 during the period starting with the date sixty (60) days before the Company’s good-faith estimate of the date of filing of a registration statement if it reasonably concludes it must do
so to comply with the SEC rules applicable to such registration statement and related offering; provided that the Company’s covenants under this Subsection 3.1 shall be reinstated at such time as the Company is no longer actively
employing its commercially reasonable efforts to cause such registration statement to become effective. 
 Notwithstanding anything else in
this Subsection 3.1 to the contrary, (x) the Company shall not be obligated to provide any information under Subsection 3.1(d) to the Major Investor that purchased Series D Preferred Stock from the Company pursuant to the Purchase
Agreement, or any of its permitted transferees, and (y) the Company shall not be obligated to provide any information under Subsection 3.1 to the Major Investor that purchased Series D Preferred Stock from the Company pursuant to the
Purchase Agreement, or any of its permitted transferees, unless such Major Investor continues to own shares representing at least fifty percent (50%) of the combined aggregate voting power of (1) the shares of Series D Preferred Stock and
Series D-1 Preferred Stock purchased by such Major Investor pursuant to the Purchase Agreement and (2) the shares of Common Stock purchased by such Major Investor pursuant to the Stock Purchase Agreement, dated as of December 19, 2014, by
and between the Flagship VentureLabs IV LLC and such Major Investor. 
 3.2 Inspection. The Company shall permit each Major Investor
(provided that the Board of Directors has not reasonably determined that such Major Investor is a competitor of the Company), at such Major Investor’s expense, to visit and inspect the Company’s properties; examine its books of account and
records; and discuss the Company’s affairs, finances, and accounts with its officers, during normal business hours of the Company as may be reasonably requested by the Major Investor; provided, however, that the Company shall not
be obligated pursuant to this Subsection 3.2 to provide access to any information that it reasonably and in good faith considers to be confidential information (unless covered by an enforceable confidentiality agreement, in form acceptable to
the Company) or a trade secret or the disclosure of which would adversely affect the attorney-client privilege between the Company and its counsel. 

  
 16 

 3.3 Termination of Information Rights. The covenants set forth in Subsection 3.1
and Subsection 3.2 shall terminate and be of no further force or effect (i) immediately before the consummation of the IPO, (ii) when the Company first becomes subject to the periodic reporting requirements of Section 12(g) or
15(d) of the Exchange Act, or (iii) upon a Deemed Liquidation Event, as such term is defined in the Company’s Certificate of Incorporation, unless the consideration received by the Investors is in the form of securities that are privately
held, whichever event occurs first. 
 3.4 Confidentiality. Each Investor agrees that such Investor will keep confidential and will
not disclose, divulge, or use for any purpose (other than to monitor its investment in the Company) any confidential information obtained from the Company pursuant to the terms of this Agreement (including notice of the Company’s intention to
file a registration statement), unless such confidential information (a) is known or becomes known to the public in general (other than as a result of a breach of this Subsection 3.4 by such Investor), (b) is or has been
independently developed or conceived by any Investor without use of the Company’s confidential information, or (c) is or has been made known or disclosed to any Investor by a third party without a breach of any obligation of
confidentiality such third party may have to the Company; provided, however, that an Investor may disclose confidential information: (i) to its attorneys, accountants, consultants, and other professionals to the extent necessary
to obtain their services in connection with monitoring its investment in the Company; (ii) to any prospective purchaser of any Registrable Securities from such Investor, if such prospective purchaser agrees to be bound by the provisions of this
Subsection 3.4; (iii) to any existing or prospective Affiliate, partner, member, stockholder, or wholly owned subsidiary of such Investor in the ordinary course of business, provided that such Investor informs such Person
that such information is confidential and directs such Person to maintain the confidentiality of such information; or (iv) as may otherwise be required by law, provided that such Investor promptly notifies the Company of such
disclosure and takes reasonable steps to minimize the extent of any such required disclosure. 
 4. Rights to Future Stock Issuances.

 4.1 Right of First Offer. Subject to the terms and conditions of this Subsection 4.1 and applicable securities laws, if the
Company proposes to offer or sell any New Securities, the Company shall first offer such New Securities to each Major Investor. A Major Investor shall be entitled to apportion the right of first offer hereby granted to it among itself and its
Affiliates in such proportions as it deems appropriate. 
 (a) The Company shall give notice (the “Offer Notice”) to each
Major Investor, stating (i) its bona fide intention to offer such New Securities, (ii) the number of such New Securities to be offered, and (iii) the price and terms, if any, upon which it proposes to offer such New Securities. 

(b) By notification to the Company within twenty (20) days after the Offer Notice is given, each Major Investor may elect to purchase or
otherwise acquire, at the 

  
 17 

 
price and on the terms specified in the Offer Notice, up to that portion of such New Securities which equals the proportion that the Common Stock issued and held, or issuable (directly or
indirectly) upon conversion and/or exercise, as applicable, of the Preferred Stock and any other Derivative Securities then held, by such Major Investor bears to the total Common Stock of the Company then outstanding (assuming full conversion and/or
exercise, as applicable, of all Preferred Stock and other Derivative Securities). At the expiration of such twenty (20) day period, the Company shall promptly notify each Major Investor that elects to purchase or acquire all the shares
available to it (each, a “Fully Exercising Investor”) of any other Major Investor’s failure to do likewise. During the ten (10) day period commencing after the Company has given such notice, each Fully Exercising Investor
may, by giving notice to the Company, elect to purchase or acquire, in addition to the number of shares specified above, up to that portion of the New Securities for which Major Investors were entitled to subscribe but that were not subscribed for
by the Major Investors which is equal to the proportion that the Common Stock issued and held, or issuable (directly or indirectly) upon conversion and/or exercise, as applicable, of Preferred Stock and any other Derivative Securities then held, by
such Fully Exercising Investor bears to the Common Stock issued and held, or issuable (directly or indirectly) upon conversion and/or exercise, as applicable, of the Preferred Stock and any other Derivative Securities then held, by all Fully
Exercising Investors who wish to purchase such unsubscribed shares. The closing of any sale pursuant to this Subsection 4.1(b) shall occur within the later of ninety (90) days of the date that the Offer Notice is given and the date of
initial sale of New Securities pursuant to Subsection 4.1(c). 
 (c) If all New Securities referred to in the Offer Notice are not
elected to be purchased or acquired as provided in Subsection 4.1(b), the Company may, during the ninety (90) day period following the expiration of the periods provided in Subsection 4.1(b), offer and sell the remaining
unsubscribed portion of such New Securities to any Person or Persons at a price not less than, and upon terms no more favorable to the offeree than, those specified in the Offer Notice. If the Company does not enter into an agreement for the sale of
the New Securities within such period, or if such agreement is not consummated within thirty (30) days of the execution thereof, the right provided hereunder shall be deemed to be revived and such New Securities shall not be offered unless
first reoffered to the Major Investors in accordance with this Subsection 4.1. 
 (d) The right of first offer in this Subsection
4.1 shall not be applicable to (i) Exempted Securities (as defined in the Company’s Certificate of Incorporation); or (ii) shares of Common Stock issued in the IPO. 

4.2 Termination. The covenants set forth in Subsection 4.1 shall terminate and be of no further force or effect
(i) immediately before the consummation of the IPO, (ii) when the Company first becomes subject to the periodic reporting requirements of Section 12(g) or 15(d) of the Exchange Act, or (iii) upon a Deemed Liquidation Event, as
such term is defined in the Company’s Certificate of Incorporation, whichever event occurs first. 
 5. Additional Covenants.

 5.1 Insurance. The Company shall use its commercially reasonable efforts to (i) maintain Directors and Officers liability
insurance and (ii) upon the request of the Board of 

  
 18 

 
Directors or the holders of a majority of the Registrable Securities then outstanding, term “key person” insurance on the Chief Executive Officer of the Company, in each case from
financially sound and reputable insurers and in an amount and on terms and conditions satisfactory to the Board of Directors. The Company will use commercially reasonable efforts to cause such insurance policies to be maintained until such time as
the Board of Directors determines that such insurance should be discontinued. The “key person” policy shall name the Company as loss payee and neither policy shall be cancelable by the Company without prior approval by the Board of
Directors, including the Preferred Director. 
 5.2 Employee Agreements. The Company will cause (i) each person now or hereafter
employed by it or by any subsidiary (or engaged by the Company or any subsidiary as a consultant/independent contractor) with access to confidential information and/or trade secrets to enter into a nondisclosure and proprietary rights assignment
agreement and (ii) each Key Employee to enter into a one (1) year noncompetition and nonsolicitation agreement, each in a form acceptable to the Investors. In addition, the Company shall not amend, modify, terminate, waive, or otherwise
alter, in whole or in part, any of the above-referenced agreements or any restricted stock agreement between the Company and any employee, without the consent of the Preferred Director. 

5.3 Employee Stock. Unless otherwise approved by the Board of Directors, including the approval of the Preferred Director, all future
employees and consultants of the Company who purchase, receive options to purchase, or receive awards of shares of the Company’s capital stock after the date hereof shall be required to execute restricted stock or option agreements, as
applicable, providing for (i) vesting of shares over a four (4) year period, with the first twenty-five percent (25%) of such shares vesting following twelve (12) months of continued employment or service, and the remaining
shares vesting in equal quarterly installments over the following thirty-six (36) months, and (ii) a market stand-off provision substantially similar to that in Subsection 2.11. In addition, unless otherwise approved by the Board of
Directors, including the Preferred Director, the Company shall retain a “right of first refusal” on employee transfers until the Company’s IPO and shall have the right to repurchase unvested shares at cost upon termination of
employment of a holder of restricted stock. 
 5.4 Qualified Small Business Stock. The Company shall use commercially reasonable
efforts to cause the shares of Preferred Stock issued pursuant to the Series C Purchase Agreement, as well as any shares into which such shares are converted, within the meaning of Section 1202(f) of the United States Internal Revenue Code of
1986 (as amended, the “Code”), to constitute “qualified small business stock” as defined in Section 1202(c) of the Code; provided, however, that such requirement shall not be applicable if the Board of
Directors of the Company determines, in its good-faith business judgment, that such qualification is inconsistent with the best interests of the Company. The Company shall submit to its stockholders (including the Investors) and to the Internal
Revenue Service any reports that may be required under Section 1202(d)(1)(C) of the Code and the regulations promulgated thereunder. In addition, within twenty (20) business days after any Investor’s written request therefor, the
Company shall, at its option, either (i) deliver to such Investor a written statement indicating whether (and what portion of) such Investor’s interest in the Company constitutes “qualified small business stock” as defined in
Section 1202(c) of the Code or (ii) deliver to such Investor such factual information in the Company’s possession as is reasonably necessary to enable such Investor to determine whether (and what portion of) such Investor’s
interest in the Company constitutes “qualified small business stock” as defined in Section 1202(c) of the Code. 

  
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 5.5 Matters Requiring Investor Director Approval. So long as the holders of Series A
Preferred Stock, Series B Preferred Stock and Series C Preferred Stock are entitled to elect a Preferred Director, the Company hereby covenants and agrees with the Investors holding shares of Series A Preferred Stock, Series B Preferred Stock and
Series C Preferred Stock that it shall not, nor shall it permit any subsidiary to, without approval of the Board of Directors, which approval must include the affirmative vote of the Preferred Director: 

(a) make any loan or advance to, or own any stock or other securities of, any subsidiary or other corporation, partnership, or other entity
unless it is wholly owned by the Company; 
 (b) make any loan or advance to any Person, including, without limitation, any employee or
director of the Company or any subsidiary, except advances and similar expenditures in the ordinary course of business or under the terms of an employee stock or option plan approved by the Board of Directors, including the Preferred Director; 

(c) guarantee, directly or indirectly, any indebtedness except for trade accounts of the Company or any subsidiary arising in the ordinary
course of business; 
 (d) make any investment inconsistent with any investment policy approved by the Board of Directors; 

(e) incur any aggregate indebtedness in excess of $250,000 that is not already included in a budget approved by the Board of Directors, other
than trade credit incurred in the ordinary course of business; 
 (f) otherwise enter into or be a party to any transaction with any
director, officer, or employee of the Company or any “associate” (as defined in Rule 12b-2 promulgated under the Exchange Act) of any such Person, except for transactions contemplated by this Agreement and the Purchase Agreement;
transactions resulting in payments to or by the Company in an aggregate amount less than $100,000 per year; or transactions made in the ordinary course of business and pursuant to reasonable requirements of the Company’s business and upon fair
and reasonable terms that are approved by a majority of the Board of Directors; 
 (g) hire, terminate, or change the compensation of the
executive officers, including approving any option grants or stock awards to executive officers; 
 (h) change the principal business of the
Company, enter new lines of business, or exit the current line of business; 
 (i) sell, assign, license, pledge, or encumber material
technology or intellectual property, other than licenses granted in the ordinary course of business; 
 (j) increase the shares of Common
Stock reserved for issuance under the Company’s 2012 Stock Incentive Plan or adopt any other equity incentive plan; or 

  
 20 

 (k) enter into any corporate strategic relationship involving the payment, contribution, or
assignment by the Company or to the Company of money or assets greater than $250,000. 
 5.6 Board Matters. Unless otherwise
determined by the vote of a majority of the directors then in office, the Board of Directors shall meet at least quarterly in accordance with an agreed-upon schedule, unless agreed by a majority of the Board of Directors, including the Preferred
Director. The Company shall reimburse the nonemployee directors for all reasonable out-of-pocket travel expenses incurred (consistent with the Company’s travel policy) in connection with attending meetings of the Board of Directors. The Company
shall cause to be established, as soon as practicable after such request, and will maintain, an audit and compensation committee, each of which shall consist solely of non-management directors. Each non-employee director shall be entitled in such
person’s discretion to be a member of any Board committee. Each committee of the Board shall include the Preferred Director. 
 5.7
Successor Indemnification. If the Company or any of its successors or assignees consolidates with or merges into any other Person and is not the continuing or surviving corporation or entity of such consolidation or merger, then to the extent
necessary, proper provision shall be made so that the successors and assignees of the Company assume the obligations of the Company with respect to indemnification of members of the Board of Directors as in effect immediately before such
transaction, whether such obligations are contained in the Company’s Bylaws, its Certificate of Incorporation, or elsewhere, as the case may be. 

5.8 Termination of Covenants. The covenants set forth in this Section 5, except for Subsection 5.7, shall terminate
and be of no further force or effect (i) immediately before the consummation of the IPO, (ii) when the Company first becomes subject to the periodic reporting requirements of Section 12(g) or 15(d) of the Exchange Act, or
(iii) upon a Deemed Liquidation Event, as such term is defined in the Company’s Certificate of Incorporation, whichever event occurs first. 

6. Miscellaneous. 
 6.1
Successors and Assigns. The rights under this Agreement may be assigned (but only with all related obligations) by a Holder to a transferee of Registrable Securities that (i) is an Affiliate of a Holder; (ii) is a Holder’s
Immediate Family Member or trust for the benefit of an individual Holder or one or more of such Holder’s Immediate Family Members; or (iii) after such transfer, holds at least 100,000 shares of Registrable Securities (subject to
appropriate adjustment for stock splits, stock dividends, combinations, and other recapitalizations); provided, however, that (x) the Company is, within a reasonable time after such transfer, furnished with written notice of the name and
address of such transferee and the Registrable Securities with respect to which such rights are being transferred; and (y) such transferee agrees in a written instrument delivered to the Company to be bound by and subject to the terms and
conditions of this Agreement, including the provisions of Subsection 2.11. For the purposes of determining the number of shares of Registrable Securities held by a transferee, the holdings of a transferee (1) that is an Affiliate or
stockholder of a Holder; (2) who is a Holder’s Immediate Family Member; or (3) that is a trust for the benefit of an individual Holder or such 

  
 21 

 
Holder’s Immediate Family Member shall be aggregated together and with those of the transferring Holder; provided further that all transferees who would not qualify individually for
assignment of rights shall have a single attorney-in-fact for the purpose of exercising any rights, receiving notices, or taking any action under this Agreement. The terms and conditions of this Agreement inure to the benefit of and are binding upon
the respective successors and permitted assignees of the parties. Nothing in this Agreement, express or implied, is intended to confer upon any party other than the parties hereto or their respective successors and permitted assignees any rights,
remedies, obligations or liabilities under or by reason of this Agreement, except as expressly provided herein. Notwithstanding anything to the contrary in this Subsection 6.1, Comerica Ventures, and its successors and assigns, may transfer
and assign its rights under the Agreement (together with all related obligations): (a) to any transferee irrespective of the minimum share requirement set forth in clause (iii) of this Subsection 6.1; and (b) to any of its
Affiliates, partners or stockholders without compliance with the notice and delivery requirements set forth in clauses (x) and (y) in the proviso at the end of the first sentence of this Subsection 6.1 of the Agreement (but only to
the extent such transferee remains bound by the restrictions and obligations of the transferor under the Agreement). 
 6.2 Governing
Law. This Agreement and any controversy arising out of or relating to this Agreement shall be governed by and construed in accordance with the internal laws of the Commonwealth of Massachusetts, without regard to conflict of law principles that
would result in the application of any law other than the law of the Commonwealth of Massachusetts. 
 6.3 Counterparts. This
Agreement may be executed in two or more counterparts, each of which shall be deemed an original, but all of which together shall constitute one and the same instrument. Counterparts may be delivered via facsimile, electronic mail (including pdf) or
other transmission method and any counterpart so delivered shall be deemed to have been duly and validly delivered and be valid and effective for all purposes. 

6.4 Titles and Subtitles. The titles and subtitles used in this Agreement are for convenience only and are not to be considered in
construing or interpreting this Agreement. 
 6.5 Notices. All notices and other communications given or made pursuant to this
Agreement shall be in writing and shall be deemed effectively given upon the earlier of actual receipt or: (i) personal delivery to the party to be notified; (ii) when sent, if sent by electronic mail or facsimile during the
recipient’s normal business hours, and if not sent during normal business hours, then on the recipient’s next business day; (iii) five (5) days after having been sent by registered or certified mail, return receipt requested,
postage prepaid; or (iv) one (1) business day after the business day of deposit with a nationally recognized overnight courier, freight prepaid, specifying next-day delivery, with written verification of receipt. All communications shall
be sent to the respective parties at their addresses as set forth on Schedule A hereto, or to the principal office of the Company at 161 First Street, Suite 2C, Cambridge, MA 02142, Attention: Chief Executive Officer, in the case of the
Company, or to such email address, facsimile number, or address as subsequently modified by written notice given in accordance with this Subsection 6.5. If notice is given to the Company, a copy shall also be given to Latham &
Watkins LLP, John Hancock Tower, 27th Floor, 200 Clarendon Street, Boston, MA 02116, Attention Peter N. Handrinos, Esq. 

  
 22 

 6.6 Amendments and Waivers. Any term of this Agreement may be amended and the observance
of any term of this Agreement may be waived (either generally or in a particular instance, and either retroactively or prospectively) only with the written consent of the Company and the holders of a majority of the Registrable Securities then
outstanding; provided that the Company may in its sole discretion waive compliance with Subsection 2.12(c) (and the Company’s failure to object promptly in writing after notification of a proposed assignment allegedly in
violation of Subsection 2.12(c) shall be deemed to be a waiver); provided further that any provision hereof may be waived by any waiving party on such party’s own behalf, without the consent of any other party.
Notwithstanding the foregoing, this Agreement may not be amended or terminated and the observance of any term hereof may not be waived with respect to any Investor without the written consent of such Investor, unless such amendment, termination, or
waiver applies to all Investors in the same fashion (it being agreed that a waiver of the provisions of Section 4 with respect to a particular transaction shall be deemed to apply to all Investors in the same fashion if such waiver does
so by its terms, notwithstanding the fact that certain Investors may nonetheless, by agreement with the Company, purchase securities in such transaction). The Company shall give prompt notice of any amendment or termination hereof or waiver
hereunder to any party hereto that did not consent in writing to such amendment, termination, or waiver. Any amendment, termination, or waiver effected in accordance with this Subsection 6.6 shall be binding on all parties hereto, regardless
of whether any such party has consented thereto; provided, however, that no such amendment shall be binding on Nestlé or any of its Affiliates if such amendment (1) is not entered into or approved in writing by
Nestlé or such Affiliate (provided that, for the avoidance of doubt, any such entry into or approval in writing that occurs through the exercise of any right or the enforcement of any obligation arising under Section 4 of the
Common Stock Purchase Agreement shall not be deemed for any purpose to constitute an entry into or an approval in writing by Nestlé or such Affiliate for this purpose) and (2)(i) imposes an obligation on Nestlé or such Affiliate
that is unrelated to (x) the subject matter of this Agreement or the Purchase Agreement, or the transactions contemplated hereby or thereby, (y) Nestlé’s investment in the Company or (z) Nestlé’s ownership of
securities of the Company or (ii) imposes any restriction on the conduct by Nestlé or any of its Affiliates of its business. No waivers of or exceptions to any term, condition, or provision of this Agreement, in any one or more
instances, shall be deemed to be or construed as a further or continuing waiver of any such term, condition, or provision. 
 6.7
Severability. In case any one or more of the provisions contained in this Agreement is for any reason held to be invalid, illegal or unenforceable in any respect, such invalidity, illegality, or unenforceability shall not affect any other
provision of this Agreement, and such invalid, illegal, or unenforceable provision shall be reformed and construed so that it will be valid, legal, and enforceable to the maximum extent permitted by law. 

6.8 Aggregation of Stock. All shares of Registrable Securities held or acquired by Affiliates shall be aggregated together for the
purpose of determining the availability of any rights under this Agreement and such Affiliated persons may apportion such rights as among themselves in any manner they deem appropriate. 

6.9 Entire Agreement. This Agreement (including any Schedules hereto) constitutes the full and entire understanding and agreement among
the parties with respect to the subject matter hereof, and any other written or oral agreement relating to the subject matter hereof existing between the parties is expressly canceled. 

  
 23 

 6.10 Dispute Resolution. The parties (a) hereby irrevocably and unconditionally
submit to the jurisdiction of the state courts of the Commonwealth of Massachusetts and to the jurisdiction of the United States District Court for the District of Massachusetts for the purpose of any suit, action or other proceeding arising out of
or based upon this Agreement, (b) agree not to commence any suit, action or other proceeding arising out of or based upon this Agreement except in the state courts of the Commonwealth of Massachusetts or the United States District Court for the
District of Massachusetts, and (c) hereby waive, and agree not to assert, by way of motion, as a defense, or otherwise, in any such suit, action or proceeding, any claim that it is not subject personally to the jurisdiction of the above-named
courts, that its property is exempt or immune from attachment or execution, that the suit, action or proceeding is brought in an inconvenient forum, that the venue of the suit, action or proceeding is improper or that this Agreement or the subject
matter hereof may not be enforced in or by such court. 
 WAIVER OF JURY TRIAL: EACH PARTY HEREBY WAIVES ITS RIGHTS TO A JURY TRIAL OF ANY
CLAIM OR CAUSE OF ACTION BASED UPON OR ARISING OUT OF THIS AGREEMENT, THE OTHER TRANSACTION DOCUMENTS, THE SECURITIES OR THE SUBJECT MATTER HEREOF OR THEREOF. THE SCOPE OF THIS WAIVER IS INTENDED TO BE ALL-ENCOMPASSING OF ANY AND ALL DISPUTES THAT
MAY BE FILED IN ANY COURT AND THAT RELATE TO THE SUBJECT MATTER OF THIS TRANSACTION, INCLUDING, WITHOUT LIMITATION, CONTRACT CLAIMS, TORT CLAIMS (INCLUDING NEGLIGENCE), BREACH OF DUTY CLAIMS, AND ALL OTHER COMMON LAW AND STATUTORY CLAIMS. THIS
SECTION HAS BEEN FULLY DISCUSSED BY EACH OF THE PARTIES HERETO AND THESE PROVISIONS WILL NOT BE SUBJECT TO ANY EXCEPTIONS. EACH PARTY HERETO HEREBY FURTHER WARRANTS AND REPRESENTS THAT SUCH PARTY HAS REVIEWED THIS WAIVER WITH ITS LEGAL COUNSEL, AND
THAT SUCH PARTY KNOWINGLY AND VOLUNTARILY WAIVES ITS JURY TRIAL RIGHTS FOLLOWING CONSULTATION WITH LEGAL COUNSEL. 
 6.11 Delays or
Omissions. No delay or omission to exercise any right, power, or remedy accruing to any party under this Agreement, upon any breach or default of any other party under this Agreement, shall impair any such right, power, or remedy of such
nonbreaching or nondefaulting party, nor shall it be construed to be a waiver of or acquiescence to any such breach or default, or to any similar breach or default thereafter occurring, nor shall any waiver of any single breach or default be deemed
a waiver of any other breach or default theretofore or thereafter occurring. All remedies, whether under this Agreement or by law or otherwise afforded to any party, shall be cumulative and not alternative. 

6.12 Further Assurances. At any time or from time to time after the date hereof, the parties agree to cooperate with each other, and at
the request of any other party, to execute and deliver any further instruments or documents and to take all such further action as the other party may reasonably request in order to evidence or effectuate the consummation of the transactions
contemplated hereby and to otherwise carry out the intent of the parties hereunder. 

  
 24 

 6.13 Acknowledgment. The Company acknowledges that each Investor is in the business of
venture capital investing and therefore review the business plans and related proprietary information of many enterprises, including enterprises which may have products or services which compete directly or indirectly with those of the Company.
Nothing in this Agreement shall preclude or in any way restrict any Investor from investing or participating in any particular enterprise whether or not such enterprise has products or services which compete with those of the Company. 

6.14 Massachusetts Business Trust. A copy of the Agreement and Declaration of Trust of each Investor affiliated with Fidelity
Management & Research Company is on file with the Secretary of State of the Commonwealth of Massachusetts and notice is hereby given that this Agreement is executed on behalf of the trustees of such Investor or any affiliate thereof as
trustees and not individually and that the obligations of this Agreement are not binding on any of the trustees, officers or stockholders of such Investor or any affiliate thereof individually but are binding only upon such Investor or any affiliate
thereof and its assets and property. 
 6.15 Series D-1 Preferred Stock. For all purposes of this Agreement, all outstanding shares
of Series D-1 Preferred Stock shall be deemed to have been converted into Series D Preferred Stock and each reference herein to “Preferred Stock” shall be deemed to refer to and include to such shares. 

[Remainder of Page Intentionally Left Blank] 

  
 25 

 IN WITNESS WHEREOF, the parties have executed this Amended and Restated Investors’ Rights
Agreement as of the date first written above. 
  

			
	SERES HEALTH, INC.
		
	By:	 	 /s/ Roger J. Pomerantz

	Name:	 	Roger J. Pomerantz, M.D.
	Title:	 	 President and Chief Executive Officer

 
			
	INVESTORS:
	
	NESTLÉ HEALTH SCIENCE US HOLDINGS, INC.
		
	By:	 	 /s/ Andrew Glass

	Name:	 	Andrew Glass
	Title:	 	Asst Sec

 
			
	INVESTORS:
	
	FIDELITY SELECT PORTFOLIOS: BIOTECHNOLOGY PORTFOLIO
		
	By:	 	 /s/ Joseph Zambello

	Name:	 	Joseph Zambello
	Title:	 	Deputy Treasurer

 
			
	INVESTORS:
	
	FIDELITY ADVISOR SERIES VII: FIDELITY ADVISOR BIOTECHNOLOGY FUND
		
	By:	 	 /s/ Joseph Zambello

	Name:	 	Joseph Zambello
	Title:	 	Deputy Treasurer

 
			
	INVESTORS:
	
	FIDELITY GROWTH COMPANY COMMINGLED POOL
		
	By:	 	 /s/ Kenneth B. Robins

	Name:	 	Kenneth B. Robins
	Title:	 	 Treasurer

 
			
	INVESTORS:
	
	FIDELITY MT. VERNON STREET TRUST: FIDELITY SERIES GROWTH COMPANY FUND
		
	By:	 	 /s/ Joseph Zambello

	Name:	 	Joseph Zambello
	Title:	 	Deputy Treasurer

 
			
	INVESTORS:
	
	FIDELITY MT. VERNON STREET TRUST: FIDELITY GROWTH COMPANY FUND
		
	By:	 	 /s/ Joseph Zambello

	Name:	 	Joseph Zambello
	Title:	 	Deputy Treasurer

 
			
	INVESTORS:
	
	ROCK SPRINGS CAPITAL MASTER FUND LP
		
	By:	 	Rock Springs GP LLC
	Its:	 	General Partner

  

			
	By:	 	 /s/ Graham McPhail

	Name:	 	Graham McPhail
	Title:	 	 Managing Director
 Rock Springs Capital

650 S. Exeter St., Suite 1070
 Baltimore, MD 21202

 
			
	INVESTORS:
	
	BLACKROCK HEALTH SCIENCES TRUST
		
	By:	 	BlackRock Advisors, LLC
	Its:	 	Investment Adviser

  

			
	By:	 	 /s/ Hongying Xie

	Name:	 	Hongying Erin Xie
	Title:	 	Managing Director

 
			
	INVESTORS:
	
	BLACKROCK HEALTH SCIENCES OPPORTUNITIES PORTFOLIO, A SERIES OF BLACKROCK FUNDS
		
	By:	 	BlackRock Advisors, LLC
	Its:	 	Investment Adviser

 
			
		
	By:	 	 /s/ Hongying Xie

	Name:	 	Hongying Erin Xie
	Title:	 	Managing Director

 
			
	INVESTORS:
	
	BLACKROCK HEALTH SCIENCES MASTER UNIT TRUST
		
	By:	 	BlackRock Capital Management, Inc.
	Its:	 	Investment Adviser

 
			
		
	By:	 	 /s/ Hongying Xie

	Name:	 	Hongying Erin Xie
	Title:	 	Managing Director

 
			
	INVESTORS:
	
	LEERINK HOLDINGS LLC
		
	By:	 	 /s/ Timothy R. G.
Gerhold            

	Name:	 	Timothy R. G. Gerhold, General Counsel
	Title:	 	Authorized Person

 
			
	INVESTORS:
	
	LEERINK SWANN CO-INVESTMENT FUND, LLC
		
	By:	 	 /s/ Joseph R. Gentile

	Name:	 	Joseph R. Gentile
	Title:	 	Manager

 
			
	INVESTORS:
	
	SOFINNOVA VENTURE PARTNERS IX, L.P.
		
	By:	 	Sofinnova Management IX, L.L.C.
		 	its General Partner

 
			
		
	By:	 	 /s/ Srinivas Akkaraju

	Name:	 	Srinivas Akkaraju
	Title:	 	Managing Member

 
			
	INVESTORS:
	
	 T. Rowe Price Health Sciences Fund, Inc.

TD Mutual Funds – TD Health Sciences Fund
 Valic
Company I – Health Sciences Fund
 T. Rowe Price Health Sciences Portfolio

John Hancock Variable Insurance Trust – Health Sciences Trust

John Hancock Funds II – Health Sciences Fund,

Each fund, severally and not jointly

		
	By:	 	T. ROWE PRICE ASSOCIATES, INC.,
		 	Investment Adviser or Subadviser

 
			
		
	By:	 	 /s/ Adam Poussard

	Name:	 	Adam Poussard
	Title:	 	Vice President

 
			
	INVESTORS:
	
	RA CAPITAL HEALTHCARE FUND, LP
		
	By:	 	 /s/ Peter
Klochinsky            

	Name:	 	Peter Kolchinsky
	Title:	 	Manager

 
			
	INVESTORS:
	
	ORBIMED PRIVATE INVESTMENTS V, LP
		
	By:	 	OrbiMed Capital GP V LLC, its General Partner
		
	By:	 	OrbiMed Advisors LLC, is Managing Member
		
	By:	 	  

	Name:	 	
	Title:	 	

			
	INVESTORS:
	
	FLAGSHIP VENTURES FUND IV, L.P.
	
	 By its General Partner

Flagship Ventures Fund IV General Partner LLC

		
	By:	 	 /s/ Noubar Afeyan

		 	Manager
	
	FLAGSHIP VENTURES FUND IV-Rx, L.P.
	
	 By its General Partner

Flagship Ventures Fund IV General Partner LLC

		
	By:	 	 /s/ Noubar Afeyan

		 	Manager
	
	FLAGSHIP VENTURES FUND 2007, L.P.
	
	 By its General Partner

Flagship Ventures Fund 2007 General Partner LLC

		
	By:	 	 /s/ Noubar Afeyan

		 	Manager
	
	FLAGSHIP VENTURELABS IV LLC
		
	By:	 	 FLAGSHIP VENTURES FUND IV, L.P.
 its
Authorized Member

		
	By:	 	 FLAGSHIP VENTURES FUND IV GENERAL PARTNER LLC

its General Partner

		
	By:	 	 /s/ Noubar Afeyan

	Name:	 	Noubar Afeyan
	Title:	 	Manager

 
			
	INVESTORS:
	
	ENSO VENTURES 2 LIMITED BY INTERLOCK DIRECTOR LTD., DIRECTOR
	
	  

	 AUTHORIZED SIGNATORY

	
	  

	 AUTHORIZED SIGNATORY

 
			
	INVESTORS:
	
	MAYO CLINIC
		
	By:	 	 /s/ Harry N. Hoffman, III

	Name:	 	Harry N. Hoffman, III
	Title:	 	Treasurer and Chief Investment Officer

 
			
	INVESTORS:
	
	ALEXANDRIA EQUITIES, LLC,
	a Delaware limited liability company
		
	By:	 	ALEXANDRIA REAL ESTATE EQUITIES, INC., a Maryland corporation, managing member
		
	By:	 	 /s/ Dean A. Shigenaga

	Name:	 	Dean A. Shigenaga
	Title:	 	Executive Vice President
		 	Chief Financial Officer

			
	INVESTORS:
	
	 /s/ Roger J. Pomerantz

	Roger J. Pomerantz, M.D.

			
	INVESTORS:
	
	FAVREAU 2008 TRUST, DTD 4-10-2008
		
	By:	 	  

	Name:	 	Jon Favreau
	Title:	 	Trustee
		
	By:	 	  

	Name:	 	Joya Favreau
	Title:	 	Trustee

			
	INVESTORS:
	
	 /s/ John Aunins

	John Aunins

			
	INVESTORS:
	
	 /s/ David Cook

	David Cook

			
	INVESTORS:
	
	 /s/ Matthew Henn

	Matthew Henn

 SCHEDULE A 

INVESTORS 
 Name and
Address 
  
  

			
	 Nestlé Health Science US Holdings, Inc.

900 Long Ridge Road, Building 2
 Stamford, CT 06902

Attention: Andrew Glass, Esq.
 Email:
andrew.glass@us.nestle.com
 F: (480) 379-5510
  

With a copy (which shall not constitute notice) to:
  

Nestlé Health Science S.A.
 Avenue Nestlé, 55

1800 Vevey
 Switzerland

Attention: Claudio Kuoni, Esq.
 Email:
Claudio.Kuoni@nestle.com
 F: 41.21.924.2875
	 	 OrbiMed Private Investments V, LP
 c/o OrbiMed
Advisors LLC
 Attention: Evan Sotiriou
 601 Lexington Ave.

54th Floor
 New York, NY 10022

		
	 Fidelity Select Portfolios: Biotechnology Portfolio

Brown Brothers Harriman & Co.
 525 Washington Blvd

Jersey City NJ 07310
 Attn: Michael Lerman 15th Floor

Corporate Actions
 Email: michael.lerman@bbh.com

F: (617) 772-2418
	 	 Leerink Swann Co-Investment Fund, LLC
 1 Federal
Street
 Boston, MA 02110
 Attention: General Counsel

F: (646) 499-7130

		
	 Fidelity Advisor Series VII: Fidelity Advisor

Biotechnology Fund
 State Street Bank & Trust

PO Box 5756
 Boston, Massachusetts 02206

Attn: Bangle & Co fbo Fidelity Advisor Series VII:

Fidelity Advisor Biotechnology Fund
 Email:
SSBCORPACTIONS@StateStreet.com
 F: (617) 988-9110
	 	 Leerink Holdings LLC
 1 Federal Street

Boston, MA 02110
 Attention: General Counsel

F: (646) 499-7130

		
	 Fidelity Growth Company Commingled Pool
 Brown
Brothers Harriman & Co.
 525 Washington Blvd
 Jersey
City NJ 07310
 Attn: Michael Lerman 15th Floor
 Corporate
Actions
 Email: michael.lerman@bbh.com
 F:
(617) 772-2418
	 	 T. Rowe Price Health Sciences Fund, Inc.
 T.
Rowe Price Associates, Inc.
 100 East Pratt Street
 Baltimore,
MD 21202
 Attn: Andrew Baek, Vice President and Senior Legal Counsel

Phone: 410-345-2090
 E-mail:
andrew_baek@troweprice.com

			
		
	 Fidelity Mt. Vernon Street Trust: Fidelity Series Growth

Company Fund
 State Street Bank & Trust

PO Box 5756
 Boston, Massachusetts 02206

Attn: WAVELENGTH + CO Fidelity Mt. Vernon
 Street Trust: Fidelity
Series Growth Company Fund
 Email: SSBCORPACTIONS@StateStreet.com

F: (617) 988-9110
	 	 VALIC Company I – Health Sciences Fund
 T.
Rowe Price Associates, Inc.
 100 East Pratt Street
 Baltimore,
MD 21202
 Attn: Andrew Baek, Vice President and Senior Legal Counsel

Phone: 410-345-2090
 E-mail:
andrew_baek@troweprice.com

		
	 Fidelity Mt. Vernon Street Trust: Fidelity Growth

Company Fund
 Ball & Co

C/o Citibank N.A/Custody
 IC&D Lock Box

P.O Box 7247-7057
 Philadelphia, P.A 19170-7057

Account #: 206681
 Email: fidelity.tpacd@citi.com

F: 813-604-1415
	 	 TD Mutual Funds – TD Health Sciences Fund

T. Rowe Price Associates, Inc.
 100 East Pratt Street

Baltimore, MD 21202
 Attn: Andrew Baek, Vice President and Senior
Legal Counsel
 Phone: 410-345-2090
 E-mail:
andrew_baek@troweprice.com

		
	 BlackRock Health Sciences Master Unit Trust
 c/o
BlackRock Advisors, LLC
 Fundamental Equity – Global Opportunities Health

& Sciences Team
 60 State Street, 19th/20th Floors

Boston, MA 02109
 Attn: Erin Xie, Chian Jiang

Email: erin.xie@blackrock.com, chian.jiang@blackrock.com
  

With a copy (which shall not constitute notice) to:
  

c/o BlackRock, Inc.
 Office of the General Counsel

40 East 52nd Street
 New York, NY 10022

Attn: David Maryles and Vincent Taurassi
 Email:
legaltransactions@blackrock.com
	 	 T. Rowe Price Health Sciences Portfolio
 T. Rowe
Price Associates, Inc.
 100 East Pratt Street
 Baltimore, MD
21202
 Attn: Andrew Baek, Vice President and Senior Legal Counsel

Phone: 410-345-2090
 E-mail:
andrew_baek@troweprice.com

		
	 BlackRock Health Sciences Trust
 c/o BlackRock
Advisors, LLC
 Fundamental Equity – Global Opportunities Health

& Sciences Team
 60 State Street, 19th/20th Floors

Boston, MA 02109
 Attn: Erin Xie, Chian Jiang

Email: erin.xie@blackrock.com, chian.jiang@blackrock.com
	 	 John Hancock Variable Insurance Trust – Health Sciences Trust

T. Rowe Price Associates, Inc.
 100 East Pratt Street

Baltimore, MD 21202
 Attn: Andrew Baek, Vice President and Senior
Legal Counsel
 Phone: 410-345-2090
 E-mail:
andrew_baek@troweprice.com

			
		
	 With a copy (which shall not constitute notice) to:
  

c/o BlackRock, Inc.
 Office of the General Counsel

40 East 52nd Street
 New York, NY 10022

Attn: David Maryles and Vincent Taurassi
 Email:
legaltransactions@blackrock.com
	 	
		
	 BlackRock Health Sciences Master Unit Trust
 c/o
BlackRock Advisors, LLC
 Fundamental Equity – Global Opportunities Health

& Sciences Team
 60 State Street, 19th/20th Floors

Boston, MA 02109
 Attn: Erin Xie, Chian Jiang

Email: erin.xie@blackrock.com,
 chian.jiang@blackrock.com

 
 With a copy (which shall not constitute notice) to:

 
 c/o BlackRock, Inc.

Office of the General Counsel
 40 East 52nd Street

New York, NY 10022
 Attn: David Maryles and Vincent Taurassi

Email: legaltransactions@blackrock.com
	 	 John Hancock Funds II – Health Sciences Fund

T. Rowe Price Associates, Inc.
 100 East Pratt Street

Baltimore, MD 21202
 Attn: Andrew Baek, Vice President and Senior
Legal Counsel
 Phone: 410-345-2090
 E-mail:
andrew_baek@troweprice.com

		
	 Sofinnova Venture Partners IX, L.P.
 c/o
Sofinnova Ventures, Inc.
 Attention: Hooman Shahlavi
 3000 Sand
Hill Road, Bldg 4, Suite 250
 Menlo Park, CA 94025
	 	 RA Capital Healthcare Fund, LP
 c/o RA Capital
Management, LLC,
 Attention: Amanda Daniels
 20 Park Plaza,
Suite 1200
 Boston, MA 02116
 F: (617) 778-2510

		
	 Flagship Ventures Fund IV, L.P.
 c/o Flagship
Ventures
 One Memorial Drive
 Cambridge, MA 02142

F: (617) 868 -1115
	 	 Rock Springs Capital Master Fund LP
 Attention:
Evans Apeadu
 650 South Exeter Street, Suite 1070
 Baltimore,
MD 21202
 Email: evans@rockspringscapital.com

		
	 Flagship Ventures Fund IV-Rx, L.P.
 c/o Flagship
Ventures
 One Memorial Drive
 Cambridge, MA 02142

F: (617) 868 -1115
	 	 Roger J. Pomerantz, M.D.
 XXXXXXXXXXXXXX

XXXXXXXXXXXXXX

		
	 Flagship Ventures Fund 2007, L.P.
 c/o Flagship
Ventures
 One Memorial Drive
 Cambridge, MA 02142

F: (617) 868 -1115
	 	 Favreau 2008 Trust, dtd 4-10-2008

XXXXXXXXXXXXXX
 XXXXXXXXXXXXXX

F: (310) 858-3947

			
		
	 Flagship VentureLabs IV LLC
 c/o Flagship
Ventures
 One Memorial Drive
 Cambridge, MA 02142

F: (617) 868 -1115
	 	 David Cook
 XXXXXXXXXXXXXX

XXXXXXXXXXXXXX
 F: (617) 945-0268

		
	 Enso Ventures 2 Limited
 Suite C1

Hirzel Court
 Hirzel Street

St Peter Port
 Guernsey

Channel Islands
 GY1 2NH F: +44 (0) 1481 755859
	 	 Matthew Henn
 XXXXXXXXXXXXXX

XXXXXXXXXXXXXX
 F: (617) 945-0268

		
	 Mayo Clinic
 200 First Street SW

Rochester, MN 55905
 F: (507) 538-7802
	 	 John Aunins
 XXXXXXXXXXXXXX

XXXXXXXXXXXXXX
 F: (617) 945-0268

		
	 Alexandria Equities, LLC
 385 E. Colorado Blvd.
Suite 299
 Pasadena, CA 91101
 F: (626) 578-0770
	 	
		
	 For purposes of Section 2.1(b), Section 2.2 through Section 2.12, and Section 6 only:

 
 Comerica Ventures Incorporated

1717 Main St.
 5th Floor, MC 6406

Dallas, TX 75201EX-10.10

 Exhibit 10.10 
  

 
 December 23, 2014 

Dr. Michele Trucksis 
 12 Forest Hill Road 

Wayland, MA 01778 
 Dear Dr. Trucksis, 

Seres Health, Inc. (the “Company”) is pleased to confirm its offer to employ you as a regular, full-time employee on the following terms:

 1. Position; start date. You will serve as the Company’s Chief Medical Officer and Executive Vice President. In this capacity
you will be reporting to Roger Pomerantz, Chief Executive Officer. Your effective date of hire will be no later than January 15th, 2015. This letter is subject to, and will become effective only upon, your commencing employment with the Company
(the date you actually commence employment, the “Effective Date”). 
 2. Base salary; work location. Your base
salary for this position will be at the rate of $320,000 per year. Your base salary will be paid semi-monthly in equal installments and in accordance with the Company’s payroll practices and procedures. Your normal place of work will be 161
First Street, Suite 2C, Cambridge, Massachusetts 02142; however, it is understood that the Company may change your normal place of work according to the Company’s future needs. 

3. Annual bonus. Beginning with the 2015 fiscal year, you will be eligible to receive an annual bonus with a target amount equal to 30%
of your annual base salary, with the actual amount of any such bonus determined at the sole discretion of the Company’s Board of Directors or an authorized committee thereof (the “Board”) based upon both the Company’s
performance and your individual performance and subject to proration for any partial year of service. Bonuses are intended to retain valuable Company employees, and a bonus is not payable unless you are an employee of the Company on the date that
such bonus is paid. 
 4. Signing bonus. The Company will pay you a one-time signing bonus in the amount of $40,000 (the
“Signing Bonus”), payable on the Company’s first ordinary payroll date following your start date and provided you remain continuously employed with the Company through the payment date. In the event that you voluntarily
terminate your employment with the Company (other than for Good Reason, as defined below) prior to the first anniversary of the Effective Date, you agree to repay to the Company a pro-rata portion of the Signing Bonus, which pro-rata amount will be
determined by multiplying the Signing Bonus by a fraction, the numerator of which is the number of days between your termination date and the first anniversary of the Effective Date, and the denominator of which is 365. 

 5. Benefits. You will be eligible to participate in the Company’s standard benefit
programs, which currently include holidays, 15 days of vacation, 5 days sick leave, medical insurance, dental insurance, 401(k) plan and life insurance, subject to the terms of such programs as in effect from time to time. 

6. Equity award. Subject to the approval of the Board, the Company will grant to you an option (the “Option”),
intended to qualify to the maximum extent permissible as an “incentive stock option” under Section 422 of the Internal Revenue Code of 1986, as amended (the “Code”), for the purchase of 339,124 shares of the
Company’s common stock with an exercise price per share equal to the per share fair market value, as determined by the Board, of the common stock on the date of grant. In all respects, the Option will be governed by the Seres Health, Inc. 2012
Stock Incentive Plan, as amended from time to time, and a stock option agreement to be entered into between you and the Company. 
 7.
Proprietary Information Agreement; Company policies. As a condition of this offer and your employment, you must sign and abide by the Company’s standard Employee Non-Competition, Non-Solicitation, Confidentiality and Assignment Agreement
(the “Proprietary Information Agreement”), a copy of which is enclosed and incorporated herein by reference. As a Company employee, you will be expected to abide by Company policies and procedures as may be in effect from time to
time. 
 8. At-will employment. It is understood that you are an “at-will” employee. You are not being offered employment
for a definite period of time, and either you or the Company may terminate the employment relationship at any time and for any reason without prior notice and without additional compensation to you, except as otherwise specifically provided in this
letter. 
 9. Termination benefits. In the event of the termination of your employment for any reason, the Company will pay you your
base salary plus any accrued but unused vacation through your last day of employment (the “Date of Termination”), and the amount of any documented, reimbursable expenses properly incurred by you on behalf of the Company prior to any
such termination and not yet reimbursed (collectively, the “Accrued Obligations”). In addition, if during the six (6) month period that immediately follows a Sale Event, the Company either (i) terminates your employment
without Cause or (ii) you resign from your employment for Good Reason (all as defined below) and provided you enter into within 52 days of the Date of Termination, do not revoke and comply with the terms of a separation agreement in a form
provided by the Company, which will include a general release of claims against the Company and related persons and entities, the Company will provide you with the following “Termination Benefits”: (a) continuation of your base
salary for the six (6) month period that immediately follows the Date of Termination (the “Salary Continuation Payments”); and (b) if elected, continuation of group health plan benefits to the extent authorized by and
consistent with COBRA, with the cost of the regular premium for such benefits shared in the same relative proportion by the Company and you as in effect on the Date Termination, until the earlier of (i) the date that is six (6) months
after the Date of Termination; and (ii) the date you become eligible for health benefits through another employer (and you agree to promptly notify the Company of such eligibility) or otherwise become ineligible for COBRA; and (c) any then
unvested portion of the Option shall become 

  
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fully vested upon the Date of Termination. The Salary Continuation Payments will commence within 60 days after the Date of Termination and shall be made on the Company’s regular payroll
dates; provided, however, that if the 60-day period begins in one calendar year and ends in a second calendar year, the Salary Continuation Payments shall begin to be paid in the second calendar year. In the event you miss a regular payroll period
between the Date of Termination and first Salary Continuation Payment date, the first Salary Continuation Payment will include a “catch up” payment. Solely for purposes of Section 409A of the Code, each Salary Continuation Payment is
considered a separate payment. For the avoidance of doubt, in the event your employment is terminated for any reason prior to a Sale Event, you will be entitled to the Accrued Obligations but you will not be entitled to Termination Benefits. 

10. Definitions. For the purposes of this letter: 

(a) “Cause” means: (i) conduct by you in connection with your service to the Company that is fraudulent, unlawful or
grossly negligent; (ii) your material breach of your material responsibilities to the Company or your willful failure to comply with lawful directives of the Board or written policies of the Company; (iii) breach by you of your
representations, warranties, covenants and/or obligations under this letter (including the Proprietary Information Agreement); and/or (iv) material misconduct by you which seriously discredits or damages the Company or any of its affiliates.

 (b) “Good Reason” means that you have complied with the “Good Reason Process” (hereinafter defined) following
the occurrence of any of the following actions undertaken by the Company without your express prior written consent: (i) the material diminution in your responsibilities, authority and function; or (ii) a material reduction in your base
salary; or (iii) a requirement by the Company that you relocate your principal location of employment to a location that is more than fifty (50) miles outside of the greater Boston metropolitan area. “Good Reason Process”
means that (i) you have reasonably determined in good faith that a Good Reason condition has occurred; (ii) you have notified the Company in writing of the first occurrence of the Good Reason condition within thirty (30) days of the
first occurrence of such condition; (iii) you have cooperated in good faith with the Company’s efforts, for a period not less than thirty (30) days following such notice (the “Cure Period”), to remedy the condition;
(iv) notwithstanding such efforts, the Good Reason condition continues to exist; and (v) you terminate your employment within thirty (30) days after the end of the Cure Period. If the Company cures the Good Reason condition during the
Cure Period, Good Reason shall be deemed not to have occurred. 
 (c) “Sale Event” means the consummation of (i) the
sale of all or substantially all of the assets of the Company on a consolidated basis to an unrelated person or entity, (ii) a merger, reorganization or consolidation involving the Company in which the shares of voting stock of the Company
outstanding immediately prior to such transaction represent or are converted into or exchanged for securities of the surviving or resulting entity immediately upon completion of such transaction which represent less than 50 percent of the
outstanding voting power of such surviving or resulting entity, (iii) the acquisition of all or a majority of the outstanding voting stock of the Company in a single transaction or a series of related transactions by a person, entity or group
of persons or entities, or (iv) any other 

  
 3 

 
acquisition of the business of the Company, as determined by the Board; provided, however, that an initial public offering of the Company’s equity securities, any subsequent public offering
or another capital raising event, or a merger effected solely to change the Company’s domicile shall not constitute a “Sale Event.” 

11. Taxes; Section 409A. All forms of compensation referred to in this offer letter are subject to reduction to reflect applicable
withholding and payroll taxes and other deductions required by law. You hereby acknowledge that the Company does not have a duty to design its compensation policies in a manner that minimizes your tax liabilities, and you will not make any claim
against the Company or the Board related to tax liabilities arising from your compensation. Anything in this letter to the contrary notwithstanding, if at the time of your separation from service within the meaning of Section 409A of the Code,
the Company determines that you are a “specified employee” within the meaning of Section 409A(a)(2)(B)(i) of the Code, then to the extent any payment or benefit that you become entitled to under this letter on account of your
separation from service would be considered deferred compensation subject to the 20 percent additional tax imposed pursuant to Section 409A(a) of the Code as a result of the application of Section 409A(a)(2)(B)(i) of the Code, such payment
shall not be payable and such benefit shall not be provided until the date that is the earlier of (A) six months and one day after your separation from service, or (B) your death. If any such delayed cash payment is otherwise payable on an
installment basis, the first payment shall include a catch-up payment covering amounts that would otherwise have been paid during the six-month period but for the application of this provision, and the balance of the installments shall be payable in
accordance with their original schedule. To the extent that any payment or benefit described in this letter constitutes “non-qualified deferred compensation” under Section 409A of the Code, and to the extent that such payment or
benefit is payable upon your termination of employment, then such payments or benefits shall be payable only upon your separation from service. The determination of whether and when a separation from service has occurred shall be made in accordance
with the presumptions set forth in Treasury Regulation Section 1.409A-1(h). The Company and you intend that this letter will be administered in accordance with Section 409A of the Code. To the extent
that any provision of this letter is ambiguous as to its compliance with Section 409A of the Code, the provision shall be read in such a manner so that all payments hereunder comply with or are exempt from Section 409A of the Code. The
Company makes no representation or warranty and shall have no liability to you or any other person if any provisions of this letter are determined to constitute deferred compensation subject to Section 409A of the Code but do not satisfy an
exemption from, or the conditions of, such Section. 
 12. Entire agreement; governing law. This letter, along with the Proprietary
Information Agreement, sets forth the complete and exclusive agreement between you and the Company with regard to your employment with the Company, and supersedes any prior representations or agreements about this matter, whether written or verbal.
The terms of this letter and the resolution of any disputes as to the meaning, effect, performance or validity of this letter or arising out of, related to, or in any way connected with this letter, your employment with the Company or any other
relationship between you and the Company (the “Disputes”) will be governed by Massachusetts law, excluding laws relating to 

  
 4 

 
conflicts or choice of law that would result in the application of law other than Massachusetts law. You and the Company submit to the exclusive personal jurisdiction of the federal and state
courts located in the Commonwealth of Massachusetts in connection with any Dispute or any claim related to any Dispute. 
 13.
Assignment. Neither you nor the Company may make any assignment of this letter or any interest in it, by operation of law or otherwise, without the prior written consent of the other; provided, however, that the Company may assign its rights
and obligations under this letter (including the Proprietary Information Agreement) without your consent to any affiliate or to any person or entity with whom the Company shall hereafter effect a reorganization, consolidate with, or merge into or to
whom it transfers all or substantially all of its properties or assets. This letter shall inure to the benefit of and be binding upon you and the Company, and each of your and its respective successors, executors, administrators, heirs and permitted
assigns. 
 14. Miscellaneous. This letter may not be modified or amended, and no breach shall be deemed to be waived, except by a
written agreement signed by you and an authorized officer of the Company. The headings and captions in this letter are for convenience only and in no way define or describe the scope or content of any provision of this letter. This letter may be
executed in two or more counterparts, each of which shall be an original and all of which together shall constitute one and the same instrument. 

15. Other terms. This offer is subject to background and reference checks that are satisfactory to the Company. In making this offer,
the Company understands, and in accepting it you represent that you are not under any obligation to any former employer or any person, firm, or corporation which would prevent, limit, or impair in any way the performance by you of your duties as an
employee of the Company. The Immigration Reform and Control Act requires employers to verify the employment eligibility and identity of new employees. Enclosed is a copy of the Form I-9 that you will be
required to complete. Please bring the appropriate documents listed on that form with you when you report for work. We will not be able to employ you if you fail to comply with this requirement. 

Please indicate your acceptance of this offer by returning signed and dated copies of this letter and the Proprietary Information Agreement to Eric Shaff at
eshaff@sereshealth.com no later than Tuesday, December 23, 2014, after which date this offer will expire. 
 We look forward to your joining the
Company and are very pleased that you will be working with us. 
  

	
	Very truly yours,
	
	 /s/ Roger Pomerantz

	
	 Roger Pomerantz
 President and CEO

SERES HEALTH, INC.

  
 5 

 Accepted and Agreed: 
  

	
	 /s/ Michele Trucksis

	Michele Trucksis
	
	 12/23/2014

	Date:

  
 6

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