UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A INFORMATION

Proxy Statement Pursuant to Section 14(a) of the

Securities Exchange Act of 1934

(Amendment No. )

Filed by the Registrant ☒ Filed by a Party other than the Registrant ☐

Check the appropriate box:

SERES THERAPEUTICS, INC.

(Name of Registrant as Specified In Its Charter)

(Name of Person(s) Filing Proxy Statement, if Other Than the Registrant)

Payment of Filing Fee (Check all boxes that apply)

SERES THERAPEUTICS, INC.

200 SIDNEY STREET – 4TH FLOOR

CAMBRIDGE, MASSACHUSETTS 02139

April 25, 2023

To Our Stockholders:

You are cordially invited to attend the 2023 Annual Meeting of Stockholders of Seres Therapeutics, Inc. at 8:00 a.m. Eastern time, on Thursday, June 22, 2023 (the “Annual Meeting”). As part of our effort to maintain a safe and healthy environment for our directors, members of management and stockholders who wish to attend the Annual Meeting, the Annual Meeting will be held entirely online again this year. You will be able to attend the Annual Meeting online and submit your questions during the meeting by visiting www.virtualshareholdermeeting.com/MCRB2023.

The Notice of Meeting and Proxy Statement on the following pages describe the matters to be presented at the Annual Meeting. Please see the section called “Who Can Attend the 2023 Annual Meeting of Stockholders?” on page 3 of the proxy statement for more information about how to attend the meeting online.

Whether or not you attend the Annual Meeting webcast, it is important that your shares be represented and voted at the Annual Meeting. Therefore, I urge you to promptly vote and submit your proxy via the Internet, or, if you received paper copies of these materials, by signing, dating and returning the enclosed proxy card in the enclosed envelope, which requires no postage if mailed in the United States. If you have previously received our Notice of Internet Availability of Proxy Materials, then instructions regarding how you can vote are contained in that notice. If you have received a proxy card, then instructions regarding how you can vote are contained on the proxy card. You may also vote online during the Annual Meeting. Instructions on how to vote during the meeting will be available at www.virtualshareholdermeeting.com/MCRB2023.

Thank you for your support.

Sincerely,

Eric D. Shaff

President and Chief Executive Officer

Notice of Annual Meeting of Stockholders

To Be Held Thursday, June 22, 2023

SERES THERAPEUTICS, INC.

200 SIDNEY STREET – 4TH FLOOR

CAMBRIDGE, MASSACHUSETTS 02139

The Annual Meeting of Stockholders (the “Annual Meeting”) of Seres Therapeutics, Inc., a Delaware corporation (the “Company”), will be held at 8:00 a.m. Eastern time on Thursday, June 22, 2023. The Annual Meeting will be a completely virtual meeting, which will be conducted via live webcast. You will be able to attend the Annual Meeting online and submit your questions during the meeting by visiting www.virtualshareholdermeeting.com/MCRB2023 and entering your 16-digit control number included on your Notice of Internet Availability of Proxy Materials (“Internet Notice”), your proxy card or on the instructions that accompanied your proxy materials. The Annual Meeting will be held for the following purposes:

Holders of record of our Common Stock as of the close of business on April 24, 2023 are entitled to notice of and to vote at the Annual Meeting, or any continuation, postponement or adjournment of the Annual Meeting. To participate in the Annual Meeting, including to vote via the Internet, you will need the 16-digit control number included on your Internet Notice, your proxy card or on the instructions that accompanied your proxy materials. A complete list of stockholders entitled to vote at the Annual Meeting will be open to the examination of any stockholder for a purpose germane to the meeting by sending an email to info@serestherapeutics.com, stating the purpose of the request and providing proof of ownership of our Common Stock for a period of ten days prior to the Annual Meeting and will also be available on the bottom of your screen during the Annual Meeting after entering your 16-digit control number. The Annual Meeting may be continued or adjourned from time to time without notice other than by announcement at the Annual Meeting.

It is important that your shares be represented regardless of the number of shares you may hold. Whether or not you plan to attend the Annual Meeting webcast, we urge you to vote your shares via the Internet, as described in the enclosed materials. If you received a copy of the proxy card by mail, you may sign, date and mail the proxy card in the enclosed return envelope. Promptly voting your shares will ensure the presence of a quorum at the Annual Meeting and will save us the expense of further solicitation. Submitting your proxy now will not prevent you from voting your shares at the Annual Meeting if you desire to do so, as your proxy is revocable at your option.

By Order of the Board of Directors

Thomas J. DesRosier

Secretary

Cambridge, Massachusetts

April 25, 2023

Proxy Statement

SERES THERAPEUTICS, INC.

200 SIDNEY STREET – 4TH FLOOR

CAMBRIDGE, MASSACHUSETTS 02139

This proxy statement is furnished in connection with the solicitation by the Board of Directors of Seres Therapeutics, Inc. of proxies to be voted at our Annual Meeting of Stockholders to be held on Thursday, June 22, 2023 (the “Annual Meeting”), at 8:00 a.m. Eastern time, and at any continuation, postponement, or adjournment of the Annual Meeting. The Annual Meeting will be a completely virtual meeting, which will be conducted via live webcast. You will be able to attend the Annual Meeting online and submit your questions during the meeting by visiting www.virtualshareholdermeeting.com/ MCRB2023 and entering your 16-digit control number included on your Notice of Internet Availability of Proxy Materials (the “Internet Notice”), on your proxy card or on the instructions that accompanied your proxy materials. Holders of record of shares of our common stock (our “Common Stock”), as of the close of business on April 24, 2023 (the “Record Date”), will be entitled to notice of and to vote at the Annual Meeting and any continuation, postponement, or adjournment of the Annual Meeting. As of the Record Date, there were 127,828,891
shares of Common Stock outstanding and entitled to vote at the Annual Meeting. Each share of Common Stock is entitled to one vote on any matter presented to stockholders at the Annual Meeting.

This proxy statement and our Annual Report to Stockholders for the year ended December 31, 2022 (the “2022 Annual Report”) will be released on or about April 25, 2023 to our stockholders on the Record Date.

In this proxy statement, “Seres”, “Company”, “we”, “us”, and “our” refer to Seres Therapeutics, Inc.

IMPORTANT NOTICE REGARDING THE AVAILABILITY OF PROXY MATERIALS FOR THE STOCKHOLDER MEETING TO BE HELD ON THURSDAY, JUNE 22, 2023

This Proxy Statement and our 2022 Annual Report to Stockholders are available at http://www.proxyvote.com/.

PROPOSALS

At the Annual Meeting, our stockholders will be asked:

Stockholders at an annual meeting will only be able to consider proposals or nominations specified in the Notice of Annual Meeting or brought before the meeting by or at the direction of our Board of Directors or by a stockholder of record on the Record Date for the meeting who is entitled to vote at the meeting and who has delivered timely written notice in proper form to our Corporate Secretary of the stockholder’s intention to bring such business before the meeting. As of the date of this proxy statement, we know of no other business that will be presented at the Annual Meeting. If any other matter properly comes before the stockholders for a vote at the Annual Meeting, however, the proxy holders named on the Company’s proxy card will vote your shares in accordance with their best judgment.

RECOMMENDATIONS OF THE BOARD

Our Board of Directors (the “Board of Directors” or the “Board”) recommends that you vote your shares of Common Stock as indicated below. If you return a properly completed proxy card, or vote your shares by Internet, your shares will be

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voted on your behalf as you direct. If not otherwise specified, shares of Common Stock represented by proxies will be voted, and the Board of Directors recommends that you vote:

If any other matter properly comes before the stockholders for a vote at the Annual Meeting, the proxy holders named on the Company’s proxy card will vote your shares in accordance with their best judgment.

INFORMATION ABOUT THIS PROXY STATEMENT

Why you Received this Proxy Statement. You are viewing or have received these proxy materials because our Board is soliciting your proxy to vote your shares of Common Stock at the Annual Meeting. This proxy statement includes information that we are required to provide to you under the rules of the Securities and Exchange Commission (“SEC”) and that is designed to assist you in voting your shares.

Notice of Internet Availability of Proxy Materials. As permitted by SEC rules, we are making this proxy statement and our 2022 Annual Report available to our stockholders electronically via the Internet. On or about April 25, 2023, we intend to commence mailing to our stockholders an Internet Notice containing instructions on how to access this proxy statement and our 2022 Annual Report and vote online. If you received an Internet Notice by mail, you will not receive a printed copy of the proxy materials unless you specifically request them. Instead, the Internet Notice instructs you on how to access and review all of the important information contained in the proxy statement and 2022 Annual Report. The Internet Notice also instructs you on how you may submit your proxy over the Internet. If you received an Internet Notice by mail and would like to receive a printed copy of our proxy materials, you should follow the instructions for requesting such materials contained on the Internet Notice.

Printed Copies of Our Proxy Materials. If you received printed copies of our proxy materials, then instructions regarding how you can vote are contained on the proxy card included in the materials.

Householding. The SEC’s rules permit us and banks, brokers, or other agents to deliver a single set of proxy materials to one address shared by two or more of our stockholders. This delivery method is referred to as “householding” and can result in significant cost savings. To take advantage of this opportunity, we and certain banks, brokers, or other agents have delivered only one set of proxy materials to multiple stockholders who share an address, unless we received contrary instructions from the impacted stockholders prior to the mailing date. We agree to deliver promptly, upon written or oral request, a separate copy of the proxy materials, as requested, to any stockholder at the shared address to which a single copy of those documents was delivered. If you prefer to receive separate copies of the proxy materials, contact Broadridge Financial Solutions, Inc. at 1-866-540-7095 or in writing at Broadridge, Householding Department, 51 Mercedes Way, Edgewood, New York 11717.

If you are currently a stockholder sharing an address with another stockholder and wish to receive only one copy of future proxy materials for your household, please contact Broadridge at the above phone number or address.

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Questions and Answers about the 2023 Annual Meeting of Stockholders

Who is entitled to vote at the Annual Meeting?

The Record Date for the Annual Meeting is April 24, 2023. You are entitled to vote at the Annual Meeting only if you were a stockholder of record at the close of business on that date, or if you hold a valid proxy for the Annual Meeting. Each outstanding share of Common Stock is entitled to one vote for all matters before the Annual Meeting. At the close of business on the Record Date, there were 127,828,891 shares of Common Stock outstanding and entitled to vote at the Annual Meeting.

What is the difference between being a "Record Holder" and holding shares in "Street Name"?

A record holder holds shares in his or her name. Shares held in “street name” means shares that are held in the name of a bank or broker on a person’s behalf.

Am I entitled to vote if my shares are held in "Street Name"?

Yes. If your shares are held by a bank or a brokerage firm, you are considered the “beneficial owner” of those shares held in “street name.” If your shares are held in street name, these proxy materials are being provided to you by your bank or brokerage firm, along with a voting instruction card if you received printed copies of our proxy materials. As the beneficial owner, you have the right to direct your bank or brokerage firm how to vote your shares, and the bank or brokerage firm is required to vote your shares in accordance with your instructions. If your shares are held in “street name” and you would like to vote your shares online at the Annual Meeting, you should contact your bank or broker to obtain your 16-digit control number or otherwise vote through the bank or broker.

How many shares must be present to hold the Annual Meeting?

A quorum must be present at the Annual Meeting for any business to be conducted. The presence at the Annual Meeting, in person, or by remote communication, or represented by proxy, of the holders of a majority in voting power of the Common Stock issued and outstanding and entitled to vote on the Record Date will constitute a quorum.

Who can attend the 2023 Annual Meeting of Stockholders?

You may attend the Annual Meeting online only if you are a Seres stockholder who is entitled to vote at the Annual Meeting, or if you hold a valid proxy for the Annual Meeting. You may attend and participate in the Annual Meeting by visiting the following website: www.virtualshareholdermeeting.com/ MCRB2023.

The meeting webcast will begin promptly at 8:00 a.m. Eastern Time. We encourage you to access the meeting prior to the start time. Online check-in will begin at 7:55 a.m. Eastern Time, and you should allow sufficient time for the check-in procedures.

To attend and participate in the Annual Meeting, you will need the 16-digit control number included on your Internet Notice, on your proxy card or on the instructions that accompanied your proxy materials. If your bank or broker holds your shares in street name, you should contact your bank or broker to obtain your 16-digit control number or otherwise vote through the bank or broker. If you lose your 16-digit control number, you may join the Annual Meeting as a “Guest” but you will not be able to vote, ask questions or access the list of stockholders as of the Record Date.

What if during the check-in time or during the Annual Meeting I have technical difficulties or trouble accessing the virtual meeting website?

We will have technicians ready to assist you with any technical difficulties you may have accessing the virtual meeting website. If you encounter any difficulties accessing the virtual meeting website during the check-in or meeting time, please call the technical support number that will be posted on the Annual Meeting login page.

Why hold a virtual meeting?

We believe that hosting a virtual meeting is in the best interest of the Company and its stockholders and enables increased stockholder attendance and participation because stockholders can participate from any location around the world. Stockholders will have the same rights and opportunities to participate as they would have at an in-person meeting.

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What if a quorum is not present at the Annual Meeting?

If a quorum is not present at the scheduled time of the Annual Meeting, (i) the Chairperson of the Annual Meeting or (ii) a majority in voting power of the stockholders present in person, or by remote communication, or represented by proxy, may adjourn the Annual Meeting until a quorum is present or represented.

What does it mean if I receive more than one internet notice or more than one set of proxy materials?

It means that your shares are held in more than one account at the transfer agent and/or with banks or brokers. Please vote all of your shares. To ensure that all of your shares are voted, for each Internet Notice or set of proxy materials, please submit your proxy via the Internet, or, if you received printed copies of the proxy materials, by signing, dating and returning each enclosed proxy card in the enclosed envelope.

How do I vote?

Whether or not you expect to attend the Annual Meeting online, we urge you to vote your shares as promptly as possible to ensure your representation and the presence of a quorum at the Annual Meeting. If you submit your proxy, you may still decide to attend the Annual Meeting and vote your shares electronically. Your most recent proxy card or Internet proxy is the one that is counted.

Stockholders of Record. If you are a stockholder of record, you may vote:

Internet voting facilities for stockholders of record will be available 24 hours a day and will close at 11:59 p.m. Eastern Time on June 21, 2023 (other than the voting that occurs during the Annual Meeting). To participate in the Annual Meeting, including to vote via the Internet, you will need the 16-digit control number included on your Internet Notice, on your proxy card or on the instructions that accompanied your proxy materials.

Beneficial Owners of Shares Held in “Street Name.” If your shares are held in street name through a bank or broker, you will receive instructions on how to vote from the bank or broker. You must follow their instructions in order for your shares to be voted. Internet voting also may be offered to stockholders owning shares through certain banks and brokers. If your shares are not registered in your own name and you would like to vote your shares online at the Annual Meeting, you should contact your bank or broker to obtain your 16-digit control number or otherwise vote through the bank or broker.

If you lose your 16-digit control number, you may join the Annual Meeting as a “Guest” but you will not be able to vote, ask questions or access the list of stockholders as of the Record Date. You will need to obtain your own Internet access if you choose to attend the Annual Meeting online and/or vote over the Internet.

Can I change my vote after I submit my proxy?

Yes.

If you are a registered stockholder, you may revoke your proxy and change your vote:

Your most recent proxy card or Internet proxy is the one that is counted. Your attendance at the Annual Meeting by itself will not revoke your proxy unless you give written notice of revocation to the Secretary before your proxy is voted or you vote online during the Annual Meeting.

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If your shares are held in street name, you may change or revoke your voting instructions by following the specific directions provided to you by your bank or broker, or you may vote online during the Annual Meeting by obtaining your 16-digit control number or otherwise voting through the bank or broker.

Will there be a question and answer session during the Annual Meeting?

As part of the Annual Meeting, we will hold a live Q&A session, during which we intend to answer appropriate questions submitted by stockholders during the meeting that are pertinent to the Company and the meeting matters. The Company will endeavor to answer as many questions submitted by stockholders as time permits. Only stockholders that have accessed the Annual Meeting as a stockholder (rather than a “Guest”) by following the procedures outlined above in “Who Can Attend the 2023 Annual Meeting of Stockholders?” will be permitted to submit questions during the Annual Meeting. Each stockholder is limited to no more than two questions. Questions should be succinct and only cover a single topic. We will not address questions that are, among other things:

Additional information regarding the Q&A session will be available in the “Rules of Conduct” available on the Annual Meeting webpage for stockholders that have accessed the Annual Meeting as a stockholder (rather than a “Guest”) by following the procedures outlined above in “Who Can Attend the 2023 Annual Meeting of Stockholders?”.

Who will count the votes?

A representative of Broadridge Financial Solutions, Inc., our inspector of election, will tabulate and certify the votes.

What if I do not specify how my shares are to be voted?

If you submit a proxy but do not indicate any voting instructions, the persons named as proxies will vote in accordance with the recommendations of our Board of Directors. Our Board of Directors’ recommendations are indicated on page 1 of this proxy statement, as well as with the description of each proposal in this proxy statement.

Will any other business be conducted at the Annual Meeting?

We know of no other business that will be presented at the Annual Meeting. If any other matter properly comes before the stockholders for a vote at the Annual Meeting, however, the proxy holders named on the Company’s proxy card will vote your shares in accordance with their best judgment.

How many votes are required for the approval of the proposals to be voted upon and how will abstentions and broker non-votes be treated?

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What is an abstention and how will votes withheld and abstentions be treated?

A “vote withheld,” in the case of the proposal regarding the election of directors, or an “abstention,” with respect to the other proposals, represents a stockholder’s affirmative choice to decline to vote on a proposal. Votes withheld and abstentions are counted as present and entitled to vote for purposes of determining a quorum. Votes withheld have no effect on the election of directors (Proposal 1), abstentions will have the same effect as a vote against the approval of an amendment to our Restated Certificate of Incorporation to increase the number of authorized shares of Common Stock (Proposal 4), and abstentions have no effect on the other proposals (Proposals 2, 3, and 5).

What are broker non-votes and do they count for determining a quorum?

Generally, broker non-votes occur when shares held by a broker in “street name” for a beneficial owner are not voted with respect to a particular proposal because the broker (1) has not received voting instructions from the beneficial owner and (2) lacks discretionary voting power to vote those shares. A broker is entitled to vote shares held for a beneficial owner on routine matters, such as the ratification of the appointment of PricewaterhouseCoopers LLP as our independent registered public accounting firm (Proposal 2), the approval of an amendment to our Restated Certificate of Incorporation to increase the number of authorized shares of Common Stock (Proposal 4), and the approval of an adjournment of the Annual Meeting, if necessary, to solicit additional proxies if there are not sufficient votes at the time of the Annual Meeting to approve Proposal 4 (Proposal 5) without instructions from the beneficial owner of those shares. On the other hand, absent instructions from the beneficial owner of such shares, a broker is not entitled to vote shares held for a beneficial owner on non-routine matters, such as the election of directors (Proposal 1) and the approval on an advisory (non-binding) basis of the compensation of our named executive officers (Proposal 3). Those items for which your broker cannot vote result in broker non-votes if you do not provide your broker with voting instructions on such items. Broker non-votes count for purposes of determining whether a quorum is present.

Where can I find the voting results of the 2023 Annual Meeting of Stockholders?

We plan to announce preliminary voting results at the Annual Meeting and we will report the final results in a Current Report on Form 8-K, which we intend to file with the SEC after the Annual Meeting.

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Proposals to be Voted On

PROPOSAL 1

Election of Directors

At the Annual Meeting, three (3) Class II Directors are to be elected to hold office until the Annual Meeting of Stockholders to be held in 2026 and until such director’s successor is elected and qualified.

We currently have ten (10) directors on our Board, including four (4) current Class II Directors. Our current Class II Directors are Stephen A. Berenson, who has served on our Board since December 2019, Richard N. Kender, who has served on our Board since October 2014, Claire M. Fraser, Ph.D., who has served on our Board since January 2023, and Meryl S. Zausner, who has served on our Board since August 2018. The Board has nominated each of Stephen A. Berenson, Richard N. Kender, and Claire M. Fraser, Ph.D., for election as Class II Directors at the Annual Meeting. Meryl S. Zausner is not standing for re-election at the Annual Meeting. Proxies cannot be voted for a greater number of persons than the number of nominees named in this proposal. Our Board has approved a reduction in its size from ten to nine directors, effective upon the completion of the Annual Meeting.

The proposal regarding the election of directors requires the approval of a plurality of the votes cast. This means that the three nominees receiving the highest number of affirmative “FOR” votes will be elected as Class II Directors. Votes withheld and broker non-votes are not considered to be votes cast and, accordingly, will have no effect on the outcome of the vote on this proposal.

As set forth in our Restated Certificate of Incorporation, the Board of Directors is currently divided into three classes with staggered, three-year terms. At each annual meeting of stockholders, the successors to directors whose terms then expire will be elected to serve from the time of election and qualification until the third annual meeting following election. The members of the classes are divided as follows:

Our Restated Certificate of Incorporation and Amended and Restated Bylaws provide that the authorized number of directors may be changed only by resolution of our Board of Directors. Any additional directorships resulting from an increase in the number of directors will be distributed among the three classes so that, as nearly as possible, each class will consist of one-third of the directors. The division of our Board of Directors into three classes with staggered three-year terms may delay or prevent a change of our management or a change in control of our Company. Our directors may be removed only for cause by the affirmative vote of the holders of at least two-thirds of our outstanding voting stock entitled to vote in the election of directors. There are no family relationships among any of our executive officers or directors.

If you submit a proxy but do not indicate any voting instructions, the persons named as proxies will vote the shares of Common Stock represented thereby for the election as Class II Directors of the persons whose names and biographies appear below. All of the persons whose names and biographies appear below are currently serving as our directors. In the event any of the nominees should become unable to serve, or for good cause will not serve, as a director, it is intended that votes will be cast for a substitute nominee designated by our Board of Directors or our Board of Directors may elect to reduce its size. The Board of Directors has no reason to believe that the nominees named below will be unable to serve if elected. Each of the nominees has consented to being named in this proxy statement and to serve if elected.

VOTE REQUIRED

The proposal regarding the election of directors requires the approval of a plurality of the votes cast. This means that the three nominees receiving the highest number of affirmative “FOR” votes will be elected as Class II Directors. Votes withheld and broker non-votes are not considered to be votes cast and, accordingly, will have no effect on the outcome of the vote on this proposal.

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RECOMMENDATION OF THE BOARD OF DIRECTORS

The Board of Directors unanimously recommends a vote “FOR” the election of the below Class II Director nominees.

DIRECTOR NOMINEES AND CONTINUING DIRECTORS

The principal occupations and business experience, for at least the past five years, of each Director (including the Class II Director nominees) are as follows:

Stephen A. Berenson has served as Chairman of our Board of Directors since December 2019 and as a member of our Board of Directors since August 2019. Mr. Berenson has been a Managing Partner at Flagship Pioneering, a life sciences innovation firm which conceives, creates, resources and develops first-in-category bioplatform companies, since June 2017. Prior to Flagship, Mr. Berenson spent 33 years in various roles as an investment banker at J.P. Morgan, most recently serving in the role of Vice Chairman of Investment Banking from 2005 to April 2017, where he focused on providing high-touch strategic advice and complex transaction execution to leading companies across all industries globally. He was co-founder of J.P. Morgan’s Global Strategic Advisory Council and co-founder of the firm’s Board Initiative. Mr. Berenson has served as chairman of the board of directors of Cellarity, a privately held company, since July 2021, and has served on the boards of directors of Moderna, Inc. since October 2017 and Repertoire Immune Medicines, a privately held company, since May 2021. Mr. Berenson received an S.B. in Mathematics from the Massachusetts Institute of Technology. We believe that Mr. Berenson is qualified to serve on our Board of Directors because of his extensive experience working with rapidly-growing companies across various industries.

Richard N. Kender has served as a member of our Board of Directors since October 2014. From October 1978 to September 2013, Mr. Kender held positions in a variety of corporate areas at Merck & Co., Inc., or Merck, a pharmaceutical company, most recently serving as Senior Vice President of Business Development and Corporate Licensing. Mr. Kender has served on the boards of directors of Poxel S.A. since March 2015 and Bicycle Therapeutics PLC since July 2019. He previously served on the boards of directors of INC Research Holdings, Inc. between December 2014 and August 2017, Abide Therapeutics, Inc., a privately held company, between December 2015 and May 2019, and ReViral Ltd., a privately held company, from November 2019 to June 2022. Mr. Kender received a B.S. in Accounting from Villanova University and an M.B.A. from Fairleigh Dickinson University. We believe Mr. Kender is qualified to serve on our Board of Directors because of his finance experience and knowledge of the biotechnology industry.

Claire M. Fraser, Ph.D., has served as a member of our Board of Directors since January 2023. Since 2007, Dr. Fraser has been the director of the Institute for Genome Sciences and a Professor of Medicine and Microbiology and Immunology at the University of Maryland School of Medicine in Baltimore, Maryland. From 1998 to 2007, she served as president and director of The Institute for Genomic Research, a not-for-profit research organization engaged in human

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and microbial genomics studies. Dr. Fraser has served on the board of directors of Becton, Dickinson, and Company since 2006, and previously served as the Chair of the Board and a director of the American Association for the Advancement of Science. Dr. Fraser received her bachelor’s degree in Biology from Rensselaer Polytechnic Institute and her Ph.D. in Pharmacology from State University of New York-Buffalo. We believe Dr. Fraser is qualified to serve on our Board of Directors due to her extensive academic experience and her knowledge of the microbiome industry.

Dennis A. Ausiello, M.D., has served as a member of our Board of Directors since April 2015. Dr. Ausiello has served as the Jackson Distinguished Professor of Clinical Medicine at Harvard Medical School and Director, Emeritus of Harvard Medical School’s M.D./Ph.D. Program since 1996, Chair of Medicine, Emeritus, and Director of the Center for Assessment Technology and Continuous Health (CATCH) at Massachusetts General Hospital, which he co-founded, since 2012, and Physician-in-Chief Emeritus at Massachusetts General Hospital since 2013. From 1996 to April 2013, Dr. Ausiello served as the Chief of Medicine at Massachusetts General Hospital. Dr. Ausiello is a member of the Institute of Medicine of the National Academy of Sciences and a fellow of the American Academy of Arts and Sciences. Dr. Ausiello has served on the board of directors of Alnylam Pharmaceuticals since April 2012 and previously served on the board of directors of Pfizer Inc. from 2006 to 2020, where he currently serves on the advisory board since 2019. Dr. Ausiello also serves on the boards of directors of numerous privately held companies. Dr. Ausiello received a B.A. in Biochemistry from Harvard College and an M.D. from the University of Pennsylvania. We believe that Dr. Ausiello is qualified to serve on our Board of Directors because of his extensive experience as a physician and as a director of pharmaceutical companies.

Willard H. Dere, M.D., has served as a member our Board of Directors since July 2017. Dr. Dere has been Professor Emeritus, Department of Internal Medicine, at the University of Utah School of Medicine since July 2022. Prior to retirement, and beginning in November 2014, Dr. Dere held multiple roles at the University of Utah Health Sciences Center, including Associate Vice President for Research, Co-Director of the Utah Clinical and Translational Science Institute, and Co-Director of the Center for Genomic Medicine. Prior to his professorship, from 2003 until 2014, Dr. Dere worked at Amgen, where he was Senior Vice President and head of Global Development, and led development programs in multiple therapeutic areas. From 1989 to 2014, he worked at Eli Lilly and led multiple development programs, and also worked in clinical pharmacology, regulatory affairs and safety. Dr. Dere has served on the boards of directors of BioMarin Pharmaceutical, Inc. since 2016 and Mersana Therapeutics, Inc. since 2018, and previously served on the boards of directors of Ocera Therapeutics and Radius Health. Dr. Dere received his B.A. in History and Zoology and M.D. from the University of California, Davis, completed his internal medicine residency training at the University of Utah, and his postdoctoral training in endocrinology and metabolism at the University of California, San Francisco. We believe Dr. Dere is qualified to serve on our Board of Directors due to his extensive academic experience and his knowledge of the biotechnology industry.

Eric D. Shaff has served as our President and Chief Executive Officer and a member of our Board of Directors since January 2019. Previously, he served as our Chief Operating and Financial Officer and Executive Vice President from January 2018 until January 2019 and as our Chief Financial Officer from November 2014 until January 2019. From January 2012 to November 2014, Mr. Shaff was Vice President of Corporate Finance for Momenta Pharmaceuticals, or Momenta, a biotechnology company, where he helped manage Momenta’s accounting, finance, planning, and procurement functions, as well as contributing to Momenta’s investor relations efforts. Prior to Momenta, Mr. Shaff held a number of corporate development and finance positions with Genzyme Corporation, a biotechnology company, most recently as Vice President of Finance/Controller for the Personalized Genetic Health division. Mr. Shaff has served on the board of directors of Sigilon Therapeutics, Inc. since November 2017. Mr. Shaff received his B.A. from the University of Pennsylvania and his M.B.A. from Cornell University. We believe Mr. Shaff is qualified to serve on our Board of Directors because of his extensive business and finance experience and his knowledge of the biotechnology industry.

Grégory Behar has served as a member of our Board of Directors since December 2014. Mr. Behar has served as Chief Executive Officer of Nestlé Health Science, a business unit of Société des Produits Nestlé S.A., a health sciences company, since July 2014. From August 2011 to May 2014, Mr. Behar was President and Chief Executive Officer of

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Boehringer Ingelheim Pharmaceuticals Inc. (USA), a pharmaceutical company. From 2010 to July 2011, Mr. Behar was Corporate Vice President Region NECAR (North European Union, Canada and Australasia) for Boehringer-Ingelheim GmbH, a pharmaceutical company. Mr. Behar has served on the boards of directors of Nestlé Health Science since July 2014, Axcella Health, Inc. since February 2016 and Sonova AG since April 2021 and previously served on the board of directors of Aimmune Therapeutics, Inc. from November 2016 until its acquisition in October 2020. Mr. Behar received his B.S. in Mechanical Engineering from the University of California, Los Angeles, an M.S. in Mechanical Engineering and Manufacturing from EPFL in Switzerland and an M.B.A. from INSEAD in France. We believe that Mr. Behar is qualified to serve on our Board of Directors because of his extensive business experience in the health sciences and pharmaceutical industries.

Paul R. Biondi has served as a member of our Board of Directors since March 2020. Mr. Biondi is an Executive Partner and President of Pioneering Medicines at Flagship Pioneering, a life sciences innovation firm which conceives, creates, resources and develops first-in-category bioplatform companies, roles he has held since November 2019. Mr. Biondi joined Flagship Pioneering following a seventeen-year tenure at Bristol-Myers Squibb, or BMS, a pharmaceutical company, where he was most recently the Senior Vice President of Strategy and Business Development from October 2015 to November 2019. Prior to serving in the role of Senior Vice President of Strategy, from 2002 to 2015, Mr. Biondi held a series of other leadership roles within BMS’ Research and Development organization overseeing strategy, portfolio, and project management, as well as clinical and business operations. Mr. Biondi holds a bachelor’s degree from Dartmouth College and an M.B.A. from the J.L. Kellogg School of Management at Northwestern University. We believe that Mr. Biondi is qualified to serve on our Board of Directors because of his extensive experience in biopharmaceutical strategy and corporate development.

Kurt C. Graves has served as a member of our Board of Directors since November 2015. Mr. Graves has served as the Executive Chairman of i20 Therapeutics, Inc., a biotechnology company, since August 2021. Mr. Graves was previously the Chairman, President and Chief Executive Officer of Intarcia Therapeutics, Inc., a biotechnology company, from September 2010 to December 2020 and on its board of directors from August 2010 to December 2020. Previously, he served as Executive Vice President, Chief Commercial Officer and Head of Strategic Development at Vertex Pharmaceuticals Inc., or Vertex, from July 2007 to October 2009. Prior to joining Vertex, Mr. Graves held various leadership positions at Novartis Pharmaceuticals Corporation, or Novartis Corp., from 1999 to June 2007, including the Global General Medicines Business Unit Head and Chief Marketing Officer for the pharmaceuticals division of Novartis Corp. from September 2003 to June 2007. He served on the boards of directors of Radius Health, Inc. from May 2011 to March 2020, and Achillion Pharmaceuticals, Inc. from June 2012 to January 2020. Mr. Graves received a B.S. in Biology from Hillsdale College. We believe Mr. Graves is qualified to serve as a member of our Board of Directors because of his extensive experience in the life sciences industry, membership on various boards of directors and his leadership and management experience.

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PROPOSAL 2

Ratification of Appointment of Independent Registered Public Accounting Firm

The Audit Committee of the Board of Directors (the “Audit Committee”) has appointed PricewaterhouseCoopers LLP as our independent registered public accounting firm for the fiscal year ending December 31, 2023. Our Board of Directors has directed that this appointment be submitted to our stockholders for ratification. Although ratification of our appointment of PricewaterhouseCoopers LLP is not required, we value the opinions of our stockholders and believe that stockholder ratification of our appointment is a good corporate governance practice.

PricewaterhouseCoopers LLP also served as our independent registered public accounting firm for the fiscal year ended December 31, 2022. Neither the accounting firm nor any of its members has any direct or indirect financial interest in or any connection with us in any capacity other than as our auditors, providing audit and non-audit related services. A representative of PricewaterhouseCoopers LLP is expected to attend the Annual Meeting and to have an opportunity to make a statement and be available to respond to appropriate questions from stockholders.

In the event that the appointment of PricewaterhouseCoopers LLP is not ratified by the stockholders, the Audit Committee will consider this fact when it appoints the independent auditors for the fiscal year ending December 31, 2024. Even if the appointment of PricewaterhouseCoopers LLP is ratified, the Audit Committee retains the discretion to appoint a different independent auditor at any time if it determines that such a change is in the interest of our Company.

VOTE REQUIRED

This proposal requires the affirmative vote of the holders of a majority in voting power of the votes cast affirmatively or negatively. Abstentions are not considered to be votes cast and, accordingly, will have no effect on the outcome of the vote on this proposal. Because brokers have discretionary authority to vote on the ratification of the appointment of PricewaterhouseCoopers LLP, we do not expect any broker non-votes in connection with this proposal.

RECOMMENDATION OF THE BOARD OF DIRECTORS

The Board of Directors unanimously recommends a vote “FOR” the Ratification of the Appointment of PricewaterhouseCoopers LLP as our Independent Registered Public Accounting Firm.

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PROPOSAL 3

Approval, on an Advisory (Non-Binding) Basis, of the Compensation of Our Named Executive Officers

In accordance with the Dodd-Frank Wall Street Reform and Consumer Protection Act of 2010 (the “Dodd-Frank Act”) and Rule 14a-21 under the Exchange Act, we request that our stockholders cast a non-binding, advisory vote to approve the compensation of our named executive officers identified in the section titled “Executive and Director Compensation” set forth below in this proxy statement. This proposal, commonly known as a “say-on-pay” proposal, gives our stockholders the opportunity to express their views on our named executive officers’ compensation. This vote is not intended to address any specific item of compensation, but rather the overall compensation of our named executive officers and the philosophy, policies and practices described in this proxy statement.

Accordingly, we ask our stockholders to vote “FOR” the following resolution at the Annual Meeting:

“RESOLVED, that the Company’s stockholders approve, by a non-binding advisory vote, the compensation of the named executive officers, as disclosed in the Company’s Proxy Statement for the 2023 Annual Meeting of Stockholders pursuant to the compensation disclosure rules of the Securities and Exchange Commission, including the compensation tables and narrative discussion.”

We believe that our compensation programs and policies for the year ended December 31, 2022 were an effective incentive for the achievement of our goals, aligned with stockholders’ interest and worthy of stockholder support. Additional details concerning how we structure our compensation programs to meet the objectives of our compensation program are provided in the section titled “Executive Compensation” set forth below in this proxy statement. In particular, we discuss how we design performance-based compensation programs and set compensation targets and other objectives to maintain a close correlation between Company and individual achievement.

This vote is merely advisory and will not be binding upon us, our Board of Directors or our Compensation and Talent Committee, nor will it create or imply any change in the duties of us, our Board of Directors or our Compensation and Talent Committee. The Compensation and Talent Committee will, however, take into account the outcome of the vote when considering future executive compensation decisions. At our 2022 Annual Meeting of Stockholders, approximately 98.5% of the votes cast on the “say-on-pay” proposal were voted “FOR” the proposal. The Board of Directors values constructive dialogue on executive compensation and other significant governance topics with our stockholders and encourages all stockholders to vote their shares on this important matter.

At our 2021 Annual Meeting of Stockholders held on June 16, 2021, our stockholders recommended, on an advisory basis, that the stockholder vote on the compensation of our named executive officers occur every year. In light of the foregoing recommendation, our board of directors determined to hold a “say-on-pay” advisory vote every year. Accordingly, our next advisory say-on-pay vote (following the non-binding advisory vote at this Annual Meeting) is expected to occur at the 2024 Annual Meeting of Stockholders.

VOTE REQUIRED

The approval, on an advisory (non-binding) basis, of the compensation of our named executive officers will require the affirmative vote of the holders of a majority in voting power of the votes cast affirmatively or negatively. Abstentions and broker non-votes are not considered to be votes cast and, accordingly, will have no effect on the outcome of the vote on this proposal.

RECOMMENDATION OF THE BOARD OF DIRECTORS

The Board of Directors unanimously recommends a vote “FOR” the approval, on an advisory (non-binding) basis, of the compensation of our named executive officers.

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PROPOSAL 4

Approval of an Amendment to Our Restated Certificate of Incorporation to Increase the Number of Authorized Shares of Common Stock

Our Restated Certificate of Incorporation currently authorizes the issuance of 200,000,000 shares of Common Stock, par value $0.001 per share. On March 29, 2023, our Board adopted a resolution to amend the Restated Certificate of Incorporation, subject to stockholder approval, by increasing the number of authorized shares of our Common Stock to 240,000,000 shares (the “Share Increase Amendment”). The additional 40,000,000 shares of Common Stock authorized for issuance pursuant to the proposed Share Increase Amendment would be part of the existing class of Common Stock and, if and when issued, would have the same rights and privileges as the shares of Common Stock presently issued and outstanding. The holders of Common Stock are not entitled to preemptive rights or cumulative voting.

The Share Increase Amendment will not affect the number of authorized shares of preferred stock of the Company, par value $0.001 per share, which is 10,000,000 shares. Currently, there are no shares of preferred stock issued and outstanding.

If our stockholders approve this proposal, then the first sentence of Article FOURTH of our Restated Certificate of Incorporation will be deleted and replaced in its entirety to read as follows:

“The total number of shares of all classes of stock that the Corporation shall have authority to issue is 250,000,000 shares, consisting of (a) 240,000,000 shares of Common Stock, $0.001 par value per share (“Common Stock”), and (b) 10,000,000 shares of Preferred Stock, $0.001 par value per share (“Preferred Stock”).”

Purpose of Share Increase Amendment

Our Board believes it is in the best interests of the Company and our stockholders to increase our authorized shares of Common Stock in order to have additional shares available for use as our Board deems appropriate or necessary. As such, the primary purpose of the Share Increase Amendment is to provide the Company with greater flexibility with respect to managing its Common Stock in connection with such corporate purposes as may, from time to time, be considered advisable by our Board. These corporate purposes could include, without limitation, financing activities, public or private offerings of Common Stock, stock dividends or splits, conversions of convertible securities, issuance of options and other equity awards pursuant to our incentive plans, establishing a strategic relationship with a corporate collaborator and acquisition transactions. Having an increased number of authorized but unissued shares of Common Stock would allow us to take prompt action with respect to corporate opportunities that develop, without the delay and expense of convening a special meeting of stockholders for the purpose of approving an increase in our capitalization. Our Board will determine whether, when and on what terms the issuance of shares of Common Stock may be warranted in connection with any of the foregoing purposes.

Effect of Approval of Proposed Amendment

The following table illustrates the effect the proposed Share Increase Amendment would have on the number of shares of Common stock available for issuance, if approved by our stockholders:

(1) Includes shares of Common Stock, if any, that may be issued under the “at the market" equity offering program.

Other than shares that will be reserved for issuance under our existing incentive plans, employee stock purchase plan, and "at the market" equity offering program, we do not currently have any arrangements, agreements or understandings that would require the issuance of additional shares of Common Stock . Because our directors and executive officers have outstanding equity awards under our incentive plans, and may be granted additional equity awards under these plans, they may be deemed to have an indirect interest in the Share Increase Amendment because, absent the amendment, the Company may not have sufficient authorized shares to make future awards.

The Share Increase Amendment will not have any immediate effect on the rights of existing stockholders. However, our Board will have the authority to issue authorized Common Stock without requiring future stockholder approval of such

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issuances, except as may be required by applicable law or rules of the Nasdaq Stock Market. Future issuances of Common Stock or securities convertible into or exchangeable for Common Stock could have a dilutive effect on our earnings per share, book value per share and the voting power and interest of current stockholders.

If the Share Increase Amendment is approved by stockholders, all other sections of the Restated Certificate of Incorporation would be maintained in their current form. The Share Increase Amendment would become effective upon the filing of a Certificate of Amendment to our Restated Certificate of Incorporation with the Secretary of State of the State of Delaware, which the Company intends to do promptly after the Annual Meeting if this Proposal is approved by stockholders. In the event that the Share Increase Amendment is not approved by our stockholders at the Annual Meeting, the current Restated Certificate of Incorporation would remain in effect in its entirety. Our Board reserves the right, notwithstanding stockholder approval of the Share Increase Amendment and without further action by our stockholders, not to proceed with the Share Increase Amendment at any time before it becomes effective.

Potential Anti-Takeover Effect

Our Board has not proposed the Share Increase Amendment with the intention of discouraging tender offers or takeover attempts of the Company. However, the availability of additional authorized shares for issuance could, under certain circumstances, discourage or make more difficult efforts to obtain control of our company. This proposal is not being presented with the intent that it be used to prevent or discourage any acquisition attempt, but nothing would prevent our Board from taking any appropriate actions not inconsistent with its fiduciary duties. We do not have a poison pill plan and have not made any non- shareholder approved repricings of our equity awards.

Dissenters’ Rights of Appraisal

Under Delaware law, stockholders are not entitled to appraisal rights with respect to the Share Increase Amendment, and we will not independently provide our stockholders with any such right.

VOTE REQUIRED

The approval of the Share Increase Amendment will require the affirmative vote of the holders of a majority of the stock of the Company entitled to vote at the Annual Meeting. Abstentions will have the same effect as votes against this Proposal. Because brokers have discretionary authority to vote on this Proposal, we do not expect any broker non-votes in connection with this Proposal.

RECOMMENDATION OF THE BOARD OF DIRECTORS

The Board of Directors unanimously recommends a vote “FOR” the approval of an amendment to our Restated Certificate of Incorporation to increase the number of authorized shares of common stock.

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PROPOSAL 5

Approval of an Adjournment of the Annual Meeting

Our stockholders are being asked to approve an adjournment of the Annual Meeting, if necessary, to solicit additional proxies if there are not sufficient votes at the time of the Annual Meeting to approve Proposal 4.

VOTE REQUIRED

The approval of an adjournment of the Annual Meeting, if necessary, to solicit additional proxies if there are not sufficient votes at the time of the Annual Meeting to approve Proposal 4 will require the affirmative vote of the holders of a majority of voting power of the votes cast affirmatively or negatively. Abstentions will have no effect on this Proposal. Because brokers have discretionary authority to vote on this Proposal, we do not expect any broker non-votes in connection with this Proposal.

RECOMMENDATION OF THE BOARD OF DIRECTORS

The Board of Directors unanimously recommends a vote “FOR” the approval of an adjournment of the Annual Meeting, if necessary, to solicit additional proxies if there are not sufficient votes at the time of the Annual Meeting to approve Proposal 4.

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Report of the Audit Committee of the Board of Directors

The Audit Committee has reviewed the audited consolidated financial statements of the Company for the fiscal year ended December 31, 2022 and has discussed these financial statements with management and the Company’s independent registered public accounting firm. The Audit Committee has also received from, and discussed with, the Company’s independent registered public accounting firm the matters that they are required to provide to the Audit Committee, including the matters required to be discussed by the Public Company Accounting Oversight Board (“PCAOB”) and the SEC.

The Company’s independent registered public accounting firm also provided the Audit Committee with a formal written statement required by PCAOB Rule 3526 (Communications with Audit Committees Concerning Independence) describing all relationships between the independent registered public accounting firm and the Company, including the disclosures required by the applicable requirements of the PCAOB regarding the independent registered public accounting firm’s communications with the Audit Committee concerning independence. In addition, the Audit Committee discussed with the independent registered public accounting firm its independence from the Company.

Based on its discussions with management and the independent registered public accounting firm, and its review of the representations and information provided by management and the independent registered public accounting firm, the Audit Committee recommended to the Board of Directors that the audited consolidated financial statements be included in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2022.

Richard N. Kender (Chair)

Claire M. Fraser, Ph.D.

Meryl S. Zausner

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Independent Registered Public Accounting Firm Fees and Other Matters

The following table summarizes the fees of PricewaterhouseCoopers LLP, our independent registered public accounting firm, billed to us for each of the last two fiscal years for audit services and billed to us in each of the last two fiscal years for other services:

Audit Fees

Audit fees in 2022 and 2021 consist of fees billed for the audit of our annual consolidated financial statements, the review of the interim consolidated financial statements, and related services that are normally provided in connection with registration statements, and services performed in connection with our at the market common stock offering and registered direct offering.

Audit-Related Fees

Audit-related fees in 2022 and 2021 consist of fees in connection with an audit of our grant from CARB-X.

Tax Fees

There were no such fees incurred in 2022 or 2021.

All Other Fees

All other fees in 2022 and 2021 represent non-audit fees in connection with access to the PricewaterhouseCoopers LLP on-line accounting research and disclosures database.

Audit Committee Pre-Approval Policy and Procedures

The Audit Committee has adopted a policy (the “Pre-Approval Policy”) which sets forth the procedures and conditions pursuant to which audit and non-audit services proposed to be performed by the independent auditor may be pre-approved. The Pre-Approval Policy generally provides that we will not engage PricewaterhouseCoopers LLP to render any audit, audit-related, tax or permissible non-audit service unless the service is either (i) explicitly approved by the Audit Committee (“specific pre-approval”) or (ii) entered into pursuant to the pre-approval policies and procedures described in the Pre-Approval Policy (“general pre-approval”). Unless a type of service to be provided by PricewaterhouseCoopers LLP has received general pre-approval under the Pre-Approval Policy, it requires specific pre-approval by the Audit Committee or by a designated member of the Audit Committee to whom the committee has delegated the authority to grant pre-approvals. Any proposed services exceeding pre-approved cost levels or budgeted amounts will also require specific pre-approval. For both types of pre-approval, the Audit Committee will consider whether such services are consistent with the SEC’s rules on auditor independence. The Audit Committee will also consider whether the independent auditor is best positioned to provide the most effective and efficient service, for reasons such as its familiarity with our business, people, culture, accounting systems, risk profile and other factors, and whether the service might enhance our ability to manage or control risk or improve audit quality. All such factors will be considered as a whole, and no one factor should necessarily be determinative. On an annual basis, the Audit Committee reviews and generally pre-approves the services (and related fee levels or budgeted amounts) that may be provided by PricewaterhouseCoopers LLP without first obtaining specific pre-approval from the Audit Committee. The Audit Committee may revise the list of general pre-approved services from time to time, based on subsequent determinations.

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Executive Officers

The following table identifies our current executive officers:

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Corporate Governance

GENERAL

Our Board of Directors has adopted Corporate Governance Guidelines, an Insider Trading Compliance Policy, a Code of Business Conduct and Ethics and charters for the Nominating and Corporate Governance Committee of the Board of Directors (the “Nominating and Corporate Governance Committee”), the Audit Committee, the Compensation and Talent Committee of the Board of Directors (the “Compensation and Talent Committee”), and the Science and Clinical Development Committee of the Board of Directors (the "Science and Clinical Development Committee") to assist the Board in the exercise of its responsibilities and to serve as a framework for the effective governance of our Company. You can access our current committee charters, our Corporate Governance Guidelines, Insider Trading Compliance Policy, and our Code of Business Conduct and Ethics in the “Corporate Governance” section of the “Investors and News” page of our website located at www.serestherapeutics.com, or by writing to our Secretary at our offices at 200 Sidney Street, 4th Floor, Cambridge, MA 02139.

BOARD COMPOSITION

Our Board of Directors currently consists of ten members: Eric D. Shaff, Dennis A. Ausiello, M.D., Grégory Behar, Stephen A. Berenson, Paul R. Biondi, Willard H. Dere, M.D., Claire M. Fraser, Ph.D., Richard N. Kender, Kurt C. Graves and Meryl S. Zausner. As set forth in our Restated Certificate of Incorporation, the Board of Directors is currently divided into three classes with staggered, three-year terms. At each annual meeting of stockholders, the successors to directors whose terms then expire will be elected to serve from the time of election and qualification until the third annual meeting following election. Our Restated Certificate of Incorporation and Amended and Restated Bylaws provide that the authorized number of directors may be changed only by resolution of the Board of Directors. Any additional directorships resulting from an increase in the number of directors will be distributed among the three classes so that, as nearly as possible, each class will consist of one-third of the directors. The division of our Board of Directors into three classes with staggered three-year terms may delay or prevent a change of our management or a change in control of our Company. Our directors may be removed only for cause by the affirmative vote of the holders of at least two-thirds in voting power of the outstanding shares of our capital stock entitled to vote in the election of directors.

DIRECTOR INDEPENDENCE

All of our directors, other than Eric D. Shaff, qualify as “independent” in accordance with the listing requirements of The Nasdaq Global Select Market (“Nasdaq”). The Nasdaq independence definition includes a series of objective tests, including that the director is not, and has not been for at least three years, one of our employees and that neither the director nor any of his family members has engaged in various types of business dealings with us. In addition, as required by Nasdaq rules, our Board of Directors has made a subjective determination as to each independent director that no relationships exist, which, in the opinion of our Board of Directors, would interfere with the exercise of independent judgment in carrying out the responsibilities of a director. In making these determinations, our Board of Directors reviewed and discussed information provided by the directors and us with regard to each director’s business and personal activities and relationships as they may relate to us and our management, including, as to each of Mr. Berenson and Mr. Biondi, his relationship to, and our transactions with, Flagship Pioneering and its affiliates, and as to Mr. Behar, his relationship to, and our transactions with, Nestlé S.A. and its affiliates. Mr. Shaff is not independent because he is the President and Chief Executive Officer of our Company. There are no family relationships among any of our directors or executive officers.

DIRECTOR CANDIDATES

The Nominating and Corporate Governance Committee is primarily responsible for searching for qualified director candidates for election to the Board and filling vacancies on the Board. To facilitate the search process, the Nominating and Corporate Governance Committee may solicit current directors and executives of the Company for the names of potentially qualified candidates or ask directors and executives to pursue their own business contacts for the names of potentially qualified candidates. The Nominating and Corporate Governance Committee may also consult with outside advisors or retain search firms to assist in the search for qualified candidates, or consider director candidates recommended by our stockholders. Once potential candidates are identified, the Nominating and Corporate Governance Committee reviews the backgrounds of those candidates, evaluates candidates’ independence from the Company and potential conflicts of interest and determines if candidates meet the qualifications desired by the Nominating and Corporate Governance Committee for candidates for election as a director.

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In evaluating the suitability of individual candidates (both new candidates and current Board members), the Nominating and Corporate Governance Committee, in recommending candidates for election, and the Board, in approving (and, in the case of vacancies, appointing) such candidates, may take into account many factors, including: personal and professional integrity, ethics and values; experience in corporate management, such as serving as an officer or former officer of a publicly held company; strong finance experience; experience relevant to the Company’s industry; experience as a board member or executive officer of another publicly held company; relevant academic expertise or other proficiency in an area of the Company’s operations; diversity of expertise and experience in substantive matters pertaining to the Company’s business relative to other board members; diversity of background and perspective, including, but not limited to, with respect to age, gender, race, place of residence and specialized experience; practical and mature business judgment, including, but not limited to, the ability to make independent analytical inquiries; and any other relevant qualifications, attributes or skills. The Board evaluates each individual in the context of the Board as a whole, with the objective of assembling a group that can best perpetuate the success of the business and represent stockholder interests through the exercise of sound judgment using its diversity of experience in these various areas. In determining whether to recommend a director for re-election, the Nominating and Corporate Governance Committee may also consider the director’s past attendance at meetings and participation in and contributions to the activities of the Board. Claire M. Fraser, Ph.D., a Class II Director nominee appointed to the Board in 2023, was identified as a potential candidate to serve on our Board of Directors by an outside consultant hired by the Board, and was recommended by the Nominating and Corporate Governance Committee.

Stockholders may recommend individuals to the Nominating and Corporate Governance Committee for consideration as potential director candidates by submitting the names of the recommended individuals, together with appropriate biographical information and background materials, to the Nominating and Corporate Governance Committee, c/o Secretary, Seres Therapeutics, Inc., 200 Sidney Street, 4th Floor, Cambridge, MA 02139. In the event there is a vacancy, and assuming that appropriate biographical and background material has been provided on a timely basis, the Committee will evaluate stockholder-recommended candidates by following substantially the same process, and applying substantially the same criteria, as it follows for candidates submitted by others.

COMMUNICATIONS FROM STOCKHOLDERS

The Board will give appropriate attention to written communications that are submitted by stockholders, and will respond if and as appropriate. Our Secretary is primarily responsible for monitoring communications from stockholders and for providing copies or summaries to the directors as he considers appropriate.

Communications are forwarded to all directors if they relate to important substantive matters and include suggestions or comments that our Secretary and Chairman of the Board consider to be important for the directors to know. In general, communications relating to corporate governance and long-term corporate strategy are more likely to be forwarded than communications relating to ordinary business affairs, personal grievances and matters as to which we tend to receive repetitive or duplicative communications. Stockholders who wish to send communications on any topic to an individual director or to the Board should address such communications to such director or to the Board of Directors in writing: c/o Secretary, Seres Therapeutics, Inc., 200 Sidney Street, 4th Floor, Cambridge, MA 02139.

BOARD LEADERSHIP STRUCTURE AND ROLE IN RISK OVERSIGHT

Our Amended and Restated Bylaws and Corporate Governance Guidelines provide our Board of Directors with flexibility to combine or separate the positions of Chairman of the Board and Chief Executive Officer in accordance with its determination that utilizing one or the other structure would be in the best interests of our Company based on the circumstances at that time. We recognize that different board leadership structures may be appropriate for companies in different situations.

Based on the Company’s present circumstances, the Board believes that the Company and its stockholders are best served by having Mr. Berenson serve as its Chairman of the Board and Mr. Shaff serve as its Chief Executive Officer. Our current leadership structure permits Mr. Shaff to focus his attention on managing our Company and permits Mr. Berenson to manage the Board. We believe that this governance structure best reinforces the independence of the Board from management. In addition, we believe the Chairman is well-positioned to act as a bridge between management and the Board, facilitating the regular flow of information. Among other duties, the Chairman of the Board may represent the Board in communications with stockholders and other stakeholders and provide input on the structure and composition of the Board. Accordingly, we believe our current leadership structure is the optimal structure for us at this time.

However, our Board of Directors will continue to periodically review our leadership structure and may make such changes in the future as it deems appropriate. During its routine review of the Board’s leadership structure, the Board and the

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Company regularly consider the circumstances under which the roles of Chairman and Chief Executive Officer could most effectively serve the Company’s and its stockholders’ interests if combined. From time to time, the Company proactively engages with stockholders throughout the year to learn their perspectives on significant issues, and intends to continue to do so, including with respect to gathering stockholder perspectives on Board leadership structure. If, in the future, the Chairman of the Board is a member of management or does not otherwise qualify as independent, our Corporate Governance Guidelines provide for the appointment by the independent directors of a Lead Director. If appointed, the Lead Director’s responsibilities would include, but would not be limited to, presiding over all meetings of the Board of Directors at which the Chairman of the Board is not present, including any executive sessions of the independent directors, approving the Board’s meeting schedules and agendas, and acting as liaison between the independent directors of the Board and the Chief Executive Officer and the Chairman of the Board.

Risk assessment and oversight are an integral part of our governance and management processes. Our Board of Directors encourages management to promote a culture that incorporates risk management into our corporate strategy and day-to-day business operations. Management’s involvement in day-to-day risk management enables the Company’s disclosure committee, which consists of members of management, to oversee our Chief Executive Officer and Chief Financial Officer in the effective design, establishment, maintenance, review, and evaluation of the Company’s disclosure controls and procedures. The Company’s management, led by our Chief Executive Officer and executive team, implements and supervises day‑to‑day risk management processes. Additionally, management discusses strategic and operational risks at regular management meetings and conducts specific strategic planning and review sessions during the year that include a focused discussion and analysis of the risks facing us. Throughout the year, senior management reviews these risks with the Board of Directors at regular Board meetings as part of management presentations that focus on particular business functions, operations or strategies, and presents the steps taken by management to mitigate or eliminate such risks.

Our Board of Directors does not have a standing risk management committee, but rather administers this oversight function directly through the Board of Directors as a whole, as well as through various standing committees of the Board of Directors that address risks inherent in their respective areas of oversight. In particular, our Board of Directors is responsible for monitoring and assessing strategic risk exposure, including business continuity risks, and our Audit Committee is responsible for overseeing our major financial risk exposures and the steps our management has taken to monitor and control these exposures. In addition, our Audit Committee has the responsibility to consider the adequacy and effectiveness of our information security policies and practices, including those concerning data privacy and cybersecurity. The Audit Committee also monitors compliance with legal and regulatory requirements and considers and approves or disapproves any related person transactions. Our Nominating and Corporate Governance Committee oversees risks associated with our corporate governance framework and monitors the effectiveness of our environmental, social and corporate governance (“ESG”) strategy and the Corporate Governance Guidelines. Our Compensation and Talent Committee assesses and monitors whether any of our compensation policies and programs has the potential to encourage excessive risk-taking. The allocation of risk oversight among the Board and its committees is consistent with the Board’s leadership structure.

environmental, social and corporate governance ACTIVITIES

We are committed to policies and practices focused on ESG matters, which are shaped by our core values and aim to make a positive impact in the communities where we work and live. We have a history and culture of community service and continue to be involved in, and supportive of, Life Science Cares and Special Olympics Massachusetts. We are also proud to continue a student education outreach program, Seres Scholars, which is a partnership with the Cambridge Rindge & Latin School to promote equity in education by providing career mentorship, guidance, and opportunities for underserved students from our community. The program values and celebrates diversity, equity, inclusion, and belonging ("DEIB"), and awards high school seniors with a Seres scholarship after a year and a half of participation. Additionally, we encourage employee volunteerism in all Seres locations.

We also believe that our long-term success and ability to deliver innovative, safe, and effective medicines to patients requires a diverse and inclusive workforce. We value diversity at all levels of the organization and continue to focus on extending our DEIB initiatives across our entire workforce. In 2022, a dedicated DEIB workstream was mobilized to define ways to attract, develop, and retain diverse talent from all backgrounds, increase awareness within our company of unconscious biases, and help foster a stronger sense of belonging for all employees. In addition, we strive to engender an open culture of mutual respect, and one that values employees’ health and well-being. We support employee development in a variety of ways including leadership training to build people manager capabilities, ongoing performance and development conversations, conference attendance, and tuition reimbursement. Our management conducts annual employee engagement surveys and reports to our board of directors on human capital management topics, including as relevant: corporate culture, DEIB, employee development and retention, and compensation and benefits.

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ANNUAL BOARD EVALUATION

Our Corporate Governance Guidelines require the Nominating and Corporate Governance Committee to oversee an annual assessment of the Board and its committees. Our outside counsel, Latham & Watkins, LLP (“Latham”), conducted interviews with each Board member regarding the performance of the Board and its committees. Latham summarized the results of these interviews and presented them to the Nominating and Corporate Governance Committee for review and discussion.

CODE OF ETHICS

We have a written Code of Business Conduct and Ethics that applies to our directors, officers and employees, including our principal executive officer, principal financial officer, principal accounting officer, and controller, or persons performing similar functions. We have posted a current copy of the code on our website, www.serestherapeutics.com. In addition, we intend to post on our website all disclosures that are required by law or the rules of Nasdaq concerning any amendments to, or waivers from, any provision of the code.

ANTI-HEDGING AND ANTI-PLEDGING POLICY

Our Board of Directors has adopted an Insider Trading Compliance Policy, which applies to all of our directors, officers and employees. The policy prohibits our directors, officers and employees and any entities they control from purchasing financial instruments such as zero-cost collars and forward sale contracts, or otherwise engaging in transactions that hedge or offset, or are designed to hedge or offset, any decrease in the market value of the Company’s equity securities, or that may cause an officer, director, or employee to no longer have the same objectives as the Company’s other stockholders. In addition, individuals subject to this policy are prohibited from pledging the Company’s securities as collateral to secure loans.

ATTENDANCE BY MEMBERS OF THE BOARD OF DIRECTORS AT MEETINGS

There were six meetings of the Board of Directors during the fiscal year ended December 31, 2022. During the fiscal year ended December 31, 2022, each director attended at least 75% of the aggregate of all meetings of the Board of Directors and meetings of the committees on which the Director served during the period in which he or she served as a director.

Currently, we do not maintain a formal policy regarding director attendance at the Annual Meeting; however, it is expected that directors will attend absent compelling circumstances. All of our then-incumbent directors attended our annual meeting of stockholders held in 2022.

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Committees of the Board

Our Board has established four standing committees—Audit, Compensation and Talent, Nominating and Corporate Governance, and Science and Clinical Development—each of which operates under a written charter that has been approved by our Board. All of the members of each of the Board’s three standing committees are independent as defined under the Nasdaq rules. Our Board of Directors has determined that Richard N. Kender, Willard H. Dere, M.D., Claire M. Fraser, Ph.D., and Meryl S. Zausner meet the independence requirements of Rule 10A-3 under the Securities Exchange Act of 1934, as amended (the “Exchange Act”). All members of the Compensation and Talent Committee meet the heightened standard for independence specific to members of a compensation committee under the Nasdaq rules and each qualifies as a “non-employee director” as defined in Rule 16b-3 of the Exchange Act. All members of the Nominating and Corporate Governance Committee are independent under the Nasdaq rules.

The members of each of the Board committees and committee Chairs are set forth in the following chart.

* Ms. Zausner is not a nominee for re-election at the Annual Meeting.

AUDIT COMMITTEE

Our Audit Committee’s responsibilities include:

The members of the Audit Committee are Dr. Fraser, Mr. Kender and Ms. Zausner. Mr. Kender serves as the Chairperson of the committee. Dr. Dere served as a member of the Audit Committee until Dr. Fraser's appointment in January 2023. The members of our Audit Committee meet the requirements for financial literacy under the applicable rules of Nasdaq. Our Board of Directors has determined that each of Dr. Fraser, Mr. Kender and Ms. Zausner is an “audit committee financial expert” as defined by Item 407(d)(5)(ii) of Regulation S-K.

The Audit Committee met seven times in 2022.

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COMPENSATION AND TALENT COMMITTEE

Our Compensation and Talent Committee is responsible for assisting the Board in the discharge of its responsibilities relating to the compensation of our executive officers, as well as the evaluation, talent development and succession planning for our executive officers and other senior executives. In fulfilling its purpose, our Compensation and Talent Committee has the following principal duties:

The Compensation and Talent Committee has the authority to retain or obtain the advice of compensation consultants, legal counsel and other advisors to assist in carrying out its responsibilities. For information regarding the role of our compensation consultants in determining our executive compensation, please refer to the section entitled “Executive and Director Compensation— Compensation Setting Process.”

The Compensation and Talent Committee may delegate its authority under its charter to one or more subcommittees as it deems appropriate from time to time as further described in its charter, which is available on our website at www.serestherapeutics.com. The Compensation and Talent Committee may also delegate to an officer the authority to grant equity awards to certain employees, as further described in its charter and subject to the terms of our equity plans.

The members of our Compensation and Talent Committee are Messrs. Biondi, Graves and Kender and Ms. Zausner. Mr. Graves serves as the Chairperson of the Compensation and Talent Committee.

The Compensation and Talent Committee met five times in 2022.

NOMINATING AND CORPORATE GOVERNANCE COMMITTEE

Our Nominating and Corporate Governance Committee’s responsibilities include:

The members of our Nominating and Corporate Governance Committee are Dr. Ausiello and Messrs. Berenson and Behar. Mr. Berenson serves as the Chairperson of the Nominating and Corporate Governance Committee.

The Nominating and Corporate Governance Committee met three times in 2022.

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SCIENCE AND CLINICAL DEVELOPMENT COMMITTEE

Our Science and Clinical Development Committee’s responsibilities include:

The members of our Science and Clinical Development Committee are Drs. Ausiello, Dere and Fraser. Dr. Ausiello serves as the Chairperson of the Science and Clinical Development Committee.

The Science and Clinical Development Committee was formed in February 2023.

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Executive Compensation

Compensation Discussion and Analysis

GENERAL

In the Compensation Discussion and Analysis (“CD&A”) set forth below, we provide an overview and analysis of the compensation awarded to or earned by our named executive officers (“NEOs”) identified in the Summary Compensation Table below during fiscal 2022, including the elements of our compensation program for NEOs, material compensation decisions made under that program for fiscal 2022 and the material factors considered in making those decisions. For the year ended December 31, 2022, our NEOs, which consisted of our principal executive officer, our principal financial officer and our three most other highly compensated executive officers for fiscal year 2022, were:

Stockholder Advisory Vote on Executive Compensation
 

At our 2022 Annual Meeting of Stockholders, our stockholders voted in a non-binding, advisory vote to approve the compensation of our NEOs. The Compensation and Talent Committee reviewed the result of this vote, and, in light of the approval by a substantial majority of our stockholders of the compensation programs described in our 2022 proxy statement (representing approximately 98.5% of the votes cast), did not implement any significant changes to our executive compensation program as a result of the vote.

EXECUTIVE SUMMARY

Compensation Highlights:

Details of Our Compensation Program

Compensation Philosophy

Our executive compensation program has been designed to motivate, reward, attract and retain high caliber management deemed essential to ensure our success. The program seeks to align executive compensation with our short-and long-term objectives, business strategy and financial performance.

We intend that the total compensation of our NEOs reflect a “pay for performance” compensation philosophy. As detailed in the next section, we generally target total compensation relative to the 50th percentile of our peer group, but the Compensation and Talent Committee retains discretion to adjust compensation reflecting individual factors or performance. Our executive compensation program consists of three primary components: base salary, annual performance-based cash incentive awards and periodic equity-based incentives, which, in 2022, consisted of grants of stock options.

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Compensation Setting Process

Role of Board of Directors, Compensation and Talent Committee and Executive Officers

The Compensation and Talent Committee evaluates and recommends the compensation for our President and Chief Executive Officer to the Board and makes compensation decisions regarding all of our other NEOs. Our President and Chief Executive Officer reviews the performance of our other executive officers and then makes recommendations to the Compensation and Talent Committee to assist it in determining their compensation levels. While the Compensation and Talent Committee utilizes this information and values management’s observations with regard to compensation, the ultimate decisions regarding executive compensation are made by the Compensation and Talent Committee, except the compensation for our President and Chief Executive Officer, which is made by the Board.

Role of Compensation Consultant

Our Compensation and Talent Committee has the authority under its charter to engage the services of a consulting firm or other outside advisor to assist it in designing our compensation programs and in making executive compensation decisions. Our Compensation and Talent Committee engages compensation consultants to assess and make recommendations with respect to the amount and types of compensation to provide our executives and directors. Aon plc, or Aon, advised our Compensation and Talent Committee through September 2022, and Alpine Rewards, LLC, or Alpine, has advised our Compensation and Talent Committee since October 2022. When making executive compensation decisions in 2022, our Compensation and Talent Committee considered advice and data provided by Aon and Alpine. Our Compensation and Talent Committee also met with Aon and Alpine to discuss compensation of our executive officers, including our President and Chief Executive Officer. Aon and Alpine reported directly to the Compensation and Talent Committee; however, our President and Chief Executive Officer consulted with Aon and Alpine with respect to his assessments of the compensation of executive officers other than himself. Aon provided the Compensation and Talent Committee with peer group and market information, and Aon and Alpine reviewed this data with the Compensation and Talent Committee when the Compensation and Talent Committee determined whether our executive compensation is competitive, commensurate with the executive officers’ responsibilities and consistent with market trends in executive compensation practices for comparable companies.

Aon also provided additional services to us that were unrelated to executive and director compensation. The fees for these additional services were less than $120,000 during 2022. Alpine provided no additional services to us other than in its role of advising our Compensation and Talent Committee. The Compensation and Talent Committee has considered the adviser independence factors required under SEC rules and Nasdaq listing standards as they relate to Aon and Alpine and does not believe Aon's or Alpine's work in 2022 raised a conflict of interest.

The Compensation and Talent Committee recognizes the very competitive market for executive talent in our industry, and the importance of attracting and retaining strong talent as our business continues to evolve. Our positioning on compensation is intended to keep the Company competitive while strongly incentivizing performance and appropriately controlling executive compensation cost.

2022 Peer Group

In connection with the Compensation and Talent Committee’s review of our executive compensation programs in late 2021, Aon provided market data and analysis relative to a peer group selected by the Compensation and Talent Committee in consultation with Aon. Peer group companies were selected based on the following parameters:

Compared to the prior year, the criteria used to review and select peers was adjusted as follows: the market capitalization range was decreased (as the range was previously $500 million to $4 billion); and the headcount range was broadened (as the range was previously 50 to 500 employees).

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Given these changes in peer company profiles, Aon recommended and, in September 2021, the Compensation and Talent Committee approved, the removal of two companies and the addition of two new peer companies that better aligned with the Company’s profile to form the following 2022 compensation peer group:

2023 Peer Group

In connection with the Compensation and Talent Committee’s review of our executive compensation programs in late 2022, Aon provided market data and analysis relative to a peer group selected by the Compensation and Talent Committee in consultation with Aon. Peer group companies were selected based on the following parameters:

Compared to the prior year, the criteria used to review and select peers was adjusted as follows: the stage of development was updated to include only companies that have recently submitted a NDA or BLA; the market capitalization range was decreased (as the range was previously $200 million to $2 billion); the headcount range was increased (as the range was previously 100 to 1,000 employees); and the revenue was increased (as the range was previously under $250 million).

Given these changes in peer company profiles, Aon recommended and, in September 2022, the Compensation and Talent Committee approved, the removal of nine companies (two of which were acquired) and the addition of eight new peer companies that better aligned with the Company’s profile to form the following 2023 go-forward compensation peer group:

The Compensation and Talent Committee believes the constituent companies in the peer group are similar to us based on development stage, revenue, industry, executive role considerations and market capitalization and are representative of our competitors for talent and capital. Aon and Alpine provided the Compensation and Talent Committee with a competitive assessment of our compensation program for executive officers against the peer group with respect to pay philosophies, pay mix, cash and equity-linked compensation. The Compensation and Talent Committee utilizes the peer group in making compensation decisions to help ensure our compensation program for executive officers adheres to our compensation philosophy of maintaining executive pay that rewards performance while remaining competitive, commensurate with the executive officers’ responsibilities and consistent with market trends in executive compensation practices for comparable companies.

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Elements of Our Executive Compensation Program

Historically, and for fiscal 2022, our executive compensation program consisted of the following elements, each established as part of our program in order to achieve the compensation objective specified below:

We do not currently have, and we do not expect to have, formal policies relating to the allocation of total compensation among the various elements of our compensation program.

Base Salary

The base salaries of our NEOs are an important part of their total compensation package, and are intended to reflect their respective positions, duties and responsibilities. Our NEOs receive base salary to compensate them for the satisfactory performance of duties to our Company. The base salary payable to each NEO is intended to provide a visible and stable fixed component of compensation reflecting the executive’s skill set, experience, role and responsibilities. Base salaries provide our NEOs with a reasonable degree of financial certainty and stability.

Our Compensation and Talent Committee periodically reviews NEO base salaries in consultation with management and the committee's compensation consultant to determine whether any adjustments are necessary or appropriate. We elected to increase 2022 base salaries of our NEOs by an average of 4.5% to better align salaries to the 50th percentile of our peer group while considering individual performance, experience, and level of contribution. We elected to increase 2023 base salaries of our NEOs by an average of 4.2% to ensure salaries continue to be aligned with our targeted pay philosophy. The following table shows the annual base salaries of our NEOs for 2021, 2022 and 2023. Except as otherwise noted, all annual base salary increases were effective January 1 of the given year.

Cash-Based Incentive Compensation

Our NEOs generally have the opportunity to earn annual performance bonuses based on the achievement of short-term performance goals. The NEOs’ 2022 target annual cash bonuses, expressed as a percentage of base salary, were: 60% for Mr. Shaff and 40% for the other NEOs.

Our Compensation and Talent Committee generally determines annual bonuses for our NEOs by multiplying (a) base salary, by (b) target cash bonus percentage, by (c) the level of achievement of corporate and/or individual performance objectives. In addition, the Compensation and Talent Committee retains discretion to adjust annual bonuses as it determines to be appropriate to reflect company performance, individual performance or other factors that the committee believes to be appropriate. For our NEOs, except Mr. Shaff, the achievement of 2022 corporate objectives was weighted 80% and the achievement of individual objectives was weighted at 20%. Mr. Shaff’s 2022 bonus was weighted 100% on corporate objectives.

The table below provides additional details about the Compensation and Talent Committee’s assessment of our actual performance against our 2022 corporate objectives. Individual objectives are analyzed based on the business judgement

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of the Compensation and Talent Committee's subjective analysis of individual goals achieved in support of each of our corporate goals and are not based on specified performance measures.

In February 2023, in consultation with management and based on guidance from Alpine, the Compensation and Talent Committee determined to award our NEOs 2022 performance bonuses of 100% of the corporate objective portion of their target bonus levels, and Mr. Arkowitz and Ms. Cloghessy received 105%, Dr. Henn received 115%, and Dr. von Moltke received 130% of the individual performance portion of their target bonus level. Ms. Cloghessy’s 2022 bonus was pro-rated for her partial year of employment. The actual amounts paid to our NEOs under our 2022 annual cash bonus program are set forth in the 2022 Summary Compensation Table below.

Our Compensation and Talent Committee periodically reviews NEO target bonus amounts in consultation with management and the committee's compensation consultant to determine whether any adjustments are necessary or appropriate. The NEOs’ 2023 target annual cash bonus opportunity, expressed as a percentage of base salary, is: 60% for Mr. Shaff and 40% for our other NEOs, which percentages are unchanged from 2022.

Equity-Based Compensation

We maintain the 2015 Incentive Award Plan (as amended and restated, the “2015 Plan”), under which we may grant equity incentive awards to directors, employees and consultants of our Company and our affiliates, to enable us to attract and retain services, skills and experience of these individuals, which we believe are essential to our long-term success. We do not currently have any formal policy for determining the number or types of equity-based awards to grant to NEOs.

We typically grant equity incentive awards to employees when they commence employment with us and annually in conjunction with our review of individual performance. We may grant additional awards in the discretion of our Board of Directors or Compensation and Talent Committee. Our stock options allow employees to purchase shares of our Common Stock at a price equal to the fair market value of our Common Stock on the grant date and may be intended to qualify as “incentive stock options” under the Internal Revenue Code of 1986, as amended (the “Code”). We believe stock options directly align the interests of our NEOs with those of our shareholders while ensuring the retention of our executive team. Our restricted stock units represent the right to receive one share of our Common Stock or its cash value equivalent upon vesting. In 2023, we granted restricted stock units and performance-based restricted stock units to our NEOs in connection with their annual award for the first time, in order to ensure market competitiveness of our compensation program.

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Our stock options typically vest as to 25% of the shares subject to the option on the first anniversary of the grant date (or service commencement date for initial grants) and in 12 quarterly installments during the three-year period thereafter, subject to the holder’s continued service with us. From time to time, our Board of Directors or Compensation and Talent Committee may also construct alternate vesting schedules as it determines are appropriate to motivate particular employees. Stock options and restricted stock units granted to our employees may be subject to accelerated vesting in certain circumstances, as described in the section titled “Employment Agreements.”

In the first quarter of each calendar year, we generally grant equity incentive awards based on competitive market practices, the retention value that NEOs have from past equity awards, as well as the Compensation and Talent Committee's subjective analysis of the NEO's previous year's performance. In February 2022, we granted stock options to our NEOs in the following amounts and with the vesting schedule indicated below.

Additionally, in connection with Ms. Cloghessy’s commencement of employment on February 7, 2022, we granted her an option to purchase 190,000 shares with our standard vesting schedule described above.

In February 2023, we granted stock options, time-based restricted stock units and performance-based restricted stock units to our NEOs in the following amounts and with the vesting schedule indicated in the table below. In setting award levels for each type of award, the Compensation and Talent Committee considered the value and type of awards granted by our peers. The Compensation and Talent Committee selected receiving FDA approval of the BLA for SER-109 as the performance goal applicable to the performance-based restricted stock units to reflect the direct influence of our NEOs on achieving our highest corporate priority of preparing SER-109 for commercialization and included a further time-based vesting requirement following achievement to encourage retention.

Severance and Change in Control Arrangements

We are party to employment agreements with each of our NEOs, which generally provide for severance benefits and payments upon a termination without cause or for good reason and enhanced severance benefits and payments if such termination is within 60 days prior to or 12 months following a change in control. Our Compensation and Talent Committee believes that these types of arrangements are necessary to attract and retain executive talent and are a customary component of executive compensation. Particularly, such arrangements can mitigate a potential disincentive for our NEOs when they are evaluating a potential acquisition of the Company and can encourage retention through the conclusion of the transaction. The payments and benefits provided under our severance and change in control arrangements are designed to be competitive with market practices. A description of these arrangements, as well as information on the estimated payments and benefits that our NEOs would have been eligible to receive as of December

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31, 2022, are set forth in “Employment Agreements and —Potential Payments Upon Termination or Change in Control” below.

Retirement, Health, Welfare and Additional Benefits

Our NEOs are eligible to participate in our employee benefit plans and programs, including medical and dental benefits, life insurance, short-term disability and long-term disability to the same extent as our other full-time employees, subject to the terms and eligibility requirements of those plans. We believe these benefits are necessary and appropriate to provide a competitive compensation package to our NEOs.

We also sponsor a 401(k) defined contribution plan in which our NEOs may participate, subject to limits imposed by the Code, to the same extent as all of our other full-time employees. During 2022, we made discretionary employer matching contributions equal to 50% of elective contributions made by participants in the 401(k) plan, up to 6% of a participant’s eligible compensation. These matching contributions are fully vested as of the date on which the contribution is made. We believe that providing a vehicle for tax-deferred retirement savings through our 401(k) plan adds to the overall desirability of our employee compensation package and further incentivizes our employees, including our NEOs, in accordance with our compensation policies. We did not provide perquisites or special personal benefits to our NEOs for 2022.

Tax Considerations
 

As a general matter, the Compensation and Talent Committee reviews and considers the various tax and accounting implications of the compensation programs we utilize.

Compensation Committee Report

The Compensation and Talent Committee has reviewed and discussed with management the Compensation Discussion and Analysis set forth in this proxy statement. Based on such review and discussions, the Compensation and Talent Committee has recommended to the Board that the Compensation Discussion and Analysis be included in this proxy statement.

Kurt C. Graves (Chair)

Paul R. Biondi

Richard N. Kender

Meryl S. Zausner

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Executive Compensation Tables

2022 Summary Compensation Table

Grants of Plan-Based Awards in Fiscal 2022

The following table provides supplemental information relating to grants of plan-based awards made during fiscal 2022 to help explain information provided above in our Summary Compensation Table. All awards are granted under the 2015 Plan. This table presents information regarding all grants of plan-based awards occurring during fiscal 2022.

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Outstanding Equity Awards at 2022 Fiscal Year End