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.

101 CAMBRIDGEPARK DRIVE

CAMBRIDGE, MASSACHUSETTS 02140

March 13, 2025

To Our Stockholders:

You are cordially invited to attend the 2025 Annual Meeting of Stockholders of Seres Therapeutics, Inc. at 8:00 a.m. Eastern time, on Thursday, April 10, 2025 (the “Annual Meeting”). The Annual Meeting will be held online. You will be able to attend the Annual Meeting online and submit your questions during the meeting by visiting www.virtualshareholdermeeting.com/MCRB2025.

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 2025 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 by signing, dating and returning the enclosed proxy card in the enclosed envelope, which requires no postage if mailed in the United States. 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/MCRB2025.

Thank you for your support.

Sincerely,

Eric D. Shaff

President and Chief Executive Officer

Notice of Annual Meeting of Stockholders

To Be Held Thursday, April 10, 2025

SERES THERAPEUTICS, INC.

101 CAMBRIDGEPARK DRIVE

CAMBRIDGE, MASSACHUSETTS 02140

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, April 10, 2025. 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/MCRB2025 and entering your 16-digit control number included on 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 February 13, 2025 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 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 ending on the day before the Annual Meeting. 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 have received a printed copy of your proxy card by mail, you may alternatively 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

March 13, 2025

Proxy Statement

SERES THERAPEUTICS, INC.

101 CAMBRIDGEPARK DRIVE

CAMBRIDGE, MASSACHUSETTS 02140

This proxy statement is furnished in connection with the solicitation by the Board of Directors of Seres Therapeutics, Inc., a Delaware corporation (the "Company") of proxies to be voted at our Annual Meeting of Stockholders to be held on Thursday, April 10, 2025 (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/MCRB2025 and entering the 16-digit control number included 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 February 13, 2025 (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 174,107,525 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, 2024 (the “2024 Annual Report”) will be released on or about March 13, 2025 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, APRIL 10, 2025

This Proxy Statement and our 2024 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 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. Instructions regarding how you can vote are contained on the proxy card included in the proxy 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.

Questions and Answers about the 2025 Annual Meeting of Stockholders

Who is entitled to vote at the Annual Meeting?

The Record Date for the Annual Meeting is February 13, 2025. 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 174,107,525 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 2025 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/MCRB2025.

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 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 or ask questions.

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.

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 a person designated by the Chairperson of the Annual Meeting or (ii) a majority in voting power of the stockholders entitled

to vote thereon, present in person, or by remote communication, if applicable, 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 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 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 April 9, 2025 (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 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 or ask questions. 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.

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 2025 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 2025 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 2 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?

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 amendments to our Certificate of Incorporation to clarify voting requirements to amend the number of authorized shares of Common Stock and preferred stock (Proposal 6) and the approval of amendments to our Certificate of Incorporation to eliminate supermajority voting requirements (Proposal 7). Abstentions have no effect on the other proposals (Proposals 2, 3, 4, 5, and 8).

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.

Broker non-votes count for purposes of determining whether a quorum is present.

A broker is entitled to vote shares held for a beneficial owner on routine matters without instructions from the beneficial owner of those shares. We believe that Proposals 2, 5, 6 and 8 are routine matters. 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. We believe that Proposals 1, 3, 4, and 7 are non-routine matters. 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.

Where can I find the voting results of the 2025 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.

Proposals to be Voted On

PROPOSAL 1

Election of Directors

At the Annual Meeting, three (3) Class I Directors are to be elected to hold office until the Annual Meeting of Stockholders to be held in 2028 and until such director’s successor is elected and qualified.

We currently have nine (9) directors on our Board, including three (3) current Class I Directors. Our current Class I Directors are Dennis A. Ausiello, M.D., who has served on our Board since April 2015, Willard H. Dere, M.D., who has served on our Board since July 2017, and Eric D. Shaff, who has served on our Board since January 2019. The Board has nominated each of Dennis A. Ausiello, M.D., Willard H. Dere, M.D., and Eric D. Shaff for election as Class I Directors at the Annual Meeting.

As set forth in our 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 Certificate of Incorporation and Amended and Restated Bylaws ("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. Currently, 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. In Proposal 7, we are requesting stockholders to vote on the elimination of this supermajority voting requirement.

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 I 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

This Proposal 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 I 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.

RECOMMENDATION OF THE BOARD OF DIRECTORS

The Board of Directors unanimously recommends a vote “FOR” the election of the below Class I 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 I Director nominees) are as follows:

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 as Vice Chairman of the board of directors of Spexis AG, a clinical-stage biopharmaceutical company, since December 2021, 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 served as Chief Advisor to the Chief Executive Officer and Chief Medical Officer of Angita Bio, a biotechnology company, since July 2022. Dr. Dere has also been Professor Emeritus, Department of Internal Medicine, at the University of Utah School of Medicine since July 2022. From November 2014 until June 2022, 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, Mersana Therapeutics, Inc. since 2018, and Metagenomi, Inc. since August 2021, 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 previously served on the board of directors of Sigilon Therapeutics, Inc. from 2017 to August 2023. 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.

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 pharmaceutical company, since July 2021, as chairman of SAIL Biomedicines, a privately held pharmaceutical company, since August 2024, and as a director of Inari, a privately held agricultural company, since January 2024. He previously served on the board of directors of Moderna, Inc., a pharmaceutical and biotechnology company, from October 2017 to August 2024. 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.

Claire M. Fraser, Ph.D., has served as a member of our Board of Directors since January 2023. Dr. Fraser has been a faculty member at the University of Maryland School of Medicine in Baltimore, Maryland for the past 18 years and is the Founding Director of the Institute for Genome Sciences and Professor Emerita of Medicine and Microbiology and Immunology. 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 and microbial genomics studies. Dr. Fraser has served on the Board of Directors of Becton, Dickinson, and Company, a medical technology 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, her Ph.D. in Pharmacology from State University of New York-Buffalo and is an elected member of both the National Academy of Sciences and the National Academy of Medicine. 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.

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, Bicycle Therapeutics PLC since July 2019, Longeveron Inc. since May 2024 and Omega Therapeutics since June 2024. He previously served on the boards of directors of INC Research Holdings, Inc. (now known as Syneos Health) 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.

Paul R. Biondi has served as a member of our Board of Directors since March 2020. Mr. Biondi is a Managing 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 Chairman, President and Chief Executive Officer of i20 Therapeutics, Inc., a biotechnology company, since August 2023, and as a director since August 2021. He previously served as the Executive Chairman of i20 Therapeutics’ board of directors from August 2021 to August 2023. 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 senior leadership positions at Novartis Pharmaceuticals Corporation, or Novartis Corp., from 1999 to June 2007, including the Global General Medicines Business Unit Head and Global Chief Marketing Officer for the pharmaceuticals division of Novartis Corp. from September 2003 to June 2007. Prior to Novartis Corp., Mr. Graves held senior leadership positions at Merck and Astra-Merck where he led the U.S. Business Unit responsible for Prilosec, Nexium and Prilosec OTC over a 10-year period. He served as Chairman on the board of directors of Radius Health, Inc. from May 2011 to March 2020, and as a director on Achillion Pharmaceuticals, Inc., or Achillion, from June 2012 to January 2020, when Achillion was acquired. 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.

Hans-Juergen Woerle, M.D., has served as a member of our Board of Directors since February 2025. Dr. Woerle has served as Chief Medical Officer and Chief Scientific Officer at Nestlé Health Science S.A. since November 2018, where he is responsible for global research and development strategy. Dr. Woerle served on the board of directors of Cerecin Inc., a clinical-stage biotechnology company, from June 2020 to September 2024. He currently serves on the board of directors of Enterome, SA, a clinical-stage biopharmaceutical company, since June 2020. Dr. Woerle is a board-certified physician and a specialist in internal medicine and endocrinology, holding an adjunct professorship at University of Ulm. Dr. Woerle earned his bachelors degree, masters degree and medical degree from Ludwig Maximilian University. We believe Dr. Woerle is qualified to serve on our Board of Directors because of his extensive experience as a physician and in clinical research and development.

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, 2025. 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, 2024. 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, 2026. 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 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. 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.

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 2025 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, 2024 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 2024 Annual Meeting of Stockholders, approximately 65% 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 2026 Annual Meeting of Stockholders.

VOTE REQUIRED

This Proposal requires the affirmative vote of the holders of a majority 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.

PROPOSAL 4

Approval of the Amendment and Restatement of the Seres Therapeutics, Inc. 2015 Incentive Award Plan, which is scheduled to expire in 2025

In this Proposal 4, we are requesting stockholders approve the Seres Therapeutics, Inc. 2025 Incentive Award Plan, or the 2025 Plan. The Board approved the 2025 Plan on March 3, 2025, subject to and effective upon stockholder approval of the 2025 Plan at the annual meeting. The 2025 Plan is an amendment and restatement of the Seres Therapeutics, Inc. 2015 Incentive Award Plan, or the 2015 Plan, which is scheduled to expire in 2025.

If approved by our stockholders, the 2025 Plan would, among other things, authorize the issuance of 44,604,870 shares of our common stock for awards under the 2025 Plan, which includes 35,009,870 shares previously authorized for issuance under the 2015 Plan plus an increase of 9,595,000 shares, and extend the term of the 2025 Plan to March 3, 2035, the tenth anniversary of the approval of the 2025 Plan by the Board.

The 2025 Plan is described in more detail below. If this Proposal is not approved by our stockholders, the 2025 Plan will not become effective, the 2015 Plan will continue as in effect immediately prior to the date the 2025 Plan was approved by the Board and we will continue to make grants under the 2015 Plan until the expiration of the 2015 Plan on June 25, 2025, after which we will not be able to continue making equity grants to our employees, directors and consultants.

We believe that the effective use of incentive compensation has been integral to our success in the past and is vital to our ability to achieve strong performance in the future. We also believe that grants of equity awards will help create long-term participation in the Company and, thereby, assist us in attracting, retaining, motivating and rewarding employees, directors and consultants. The use of long-term equity grants allows the administrator of the 2025 Plan to align the incentives of our employees, directors and consultants with the interests of our stockholders, linking compensation to our performance. The use of equity awards as compensation also allows us to conserve cash resources for other important purposes. Accordingly, the Board believes that approval of the 2025 Plan is in the best interests of the Company and the Board recommends that stockholders vote for approval of the 2025 Plan.

Material Amendments Included in the 2025 Plan

Increase in Share Reserve

The 2025 Plan will authorize the issuance of 44,604,870 shares of our common stock for awards under the 2025 Plan, which includes 35,009,870 shares previously authorized for issuance under the 2015 Plan, plus an increase of 9,595,000 shares. The increase to the share reserve also includes a corresponding increase in the number of shares that may be issued upon exercise of incentive stock options, within the meaning of Section 422 of the Internal Revenue Code of 1986, as amended, or the “Code.”

Remove Liberal Share Recycling Provisions

Shares tendered by a participant or withheld by the Company to satisfy the exercise price of an option or stock appreciation right or to satisfy tax withholding obligations, shares subject to a stock appreciation right that are not issued in connection with the stock settlement of the stock appreciation right and shares repurchased by the Company using proceeds from the exercise of an option will not be “added back” to the shares available for issuance under the 2025 Plan.

Increase Director Compensation Limit

The sum of any cash or other compensation and the value (determined as of the grant date in accordance with ASC 718, or any successor thereto), of awards granted to any non-employee director for services as a director pursuant to the 2025 Plan during any fiscal year may not exceed $750,000, or $1,000,000 in the first year an individual becomes a non-employee director, except in extraordinary circumstances.

Removal of Evergreen Provision

The 2025 Plan does not include the “evergreen” feature pursuant to which the shares available for issuance under the 2015 Plan were automatically replenished annually. Instead, the 2025 Plan authorizes a fixed number of shares so that, other than to reflect certain corporate transactions as provided in the 2025 Plan, stockholder approval is required for any increase to the number of shares that may be issued under the 2025 Plan.

No Repricing of Awards without Stockholder Approval

We may not reduce the exercise price of an option or stock appreciation right or cancel an option or stock appreciation right in exchange for cash, another award under the 2025 Plan or an option or stock appreciation right with an exercise price that is less than the exercise price of the original option or stock appreciation right, unless such action is approved by the stockholders or taken in connection with certain corporate transactions.

Extension of Expiration Date

Unless terminated earlier pursuant to its terms, the 2025 Plan will expire on March 3, 2035. After termination, the 2025 Plan will continue to govern outstanding awards.

Other Amendments Included in the 2025 Plan

Dividend Payments

The 2025 Plan clarifies our existing practice that no dividend or dividend equivalent will be paid to a holder of an outstanding award under the 2025 Plan unless and until the award to which such dividend or dividend equivalent relates vests.

Substitute Awards

The 2025 Plan implements the NASDAQ rule permitting shares available under certain plans acquired in acquisitions and mergers to be used for certain post-transaction grants without further stockholder approval.

Delegation of Authority

The Board may delegate any or all if its powers under the 2025 Plan to a committee of the Board or to Company officers, to the extent permitted by applicable law and subject to such restrictions set by the Board.

2025 Plan Contains Equity Compensation Best Practices

In addition to the amendments described above, the 2025 Plan contains a number of provisions that we believe reflect a broad range of compensation and governance best practices. These include:

Determination of Additional Shares under the 2025 Plan

The total number of shares reserved for issuance under the 2015 Plan equals the sum of (i) 2,200,000 shares, (ii) any shares that as of the effective date of the 2015 Plan were subject to awards under our 2012 Stock Incentive Plan (the “2012 Plan”), which are forfeited or lapse unexercised and which are not issued under the 2012 Plan; and (iii) an annual increase on the first day of each calendar year beginning January 1, 2016 and ending on and including January 1, 2025, equal to the lesser of (A) 4% of the aggregate number of shares outstanding on the final day of the immediately preceding calendar year and (B) such smaller number of shares as is determined by the Board.

Set forth below is the number of shares available for issuance pursuant to outstanding and future equity awards under the 2015 Plan and under all of our equity incentive plans (other than our 2015 Employee Stock Purchase Plan (the “2015 ESPP”)) on an aggregate basis, in each case, as of February 13, 2025. The closing price of our common stock on the Nasdaq Global Select Market on that date was $0.84 per share.

2015 Plan

Combined Plans (3)

(1) As of February 13, 2025, options outstanding under the 2015 Plan had a weighted average per share exercise price of $4.36 and a weighted average remaining term of 7.98 years.

(2) As of February 13, 2025, the weighted average remaining vesting term for RSUs under the 2015 Plan was 0.9 years.

(3) Includes the 2015 Plan, the 20212 Plan and the Seres Therapeutics, Inc. 2022 Employment Inducement Award Plan (the “2022 Inducement Award Plan”). Pursuant to Rule Nasdaq Listing Rule 5635(c)(4), awards under the 2022 Inducement Award Plan generally may only be granted to an individual who is commencing employment with the Company or who is being rehired following a bona fide interruption of employment by the Company as an inducement material to the individual’s entering into employment with the Company.

(4) As of February 13, 2025, options outstanding under the 2015 Plan, the 2012 Plan and the 2022 Inducement Award Plan had a combined weighted average per share exercise price of $4.27 and a weighted average remaining term of 8.01 years.

(5) As of February 13, 2025, the combined weighted average remaining vesting term for RSUs under 2015 Plan, the 2012 Plan and the 2022 Inducement Award Plan was 2.01 years.

If this Proposal 4 is approved, the 2025 Plan will authorize the issuance of 44,604,870 shares of our common stock for awards under the 2025 Plan, which includes 35,009,870 shares previously authorized for issuance under the 2015 Plan, plus an increase of 9,595,000 shares.

In determining to adopt the 2025 Plan, the Board reviewed an analysis prepared by Alpine-Rewards, an independent compensation consultant. Specifically, the Board considered that:

The Board also considered our broader equity grant objectives and practices and believes that the 2025 Plan is necessary to permit the Company to continue using equity incentive awards to achieve the Company’s general performance, retention and incentive goals. Equity awards are intended to motivate high levels of performance and align the interests of our directors, employees and consultants with those of our stockholders by giving directors, employees and consultants the perspective of an owner with an equity stake in the Company and providing a means of recognizing their contributions to the success of the Company. Specifically, the Board considered, among other things, that the market for high caliber,

experienced talent in our industry and in our geographic location is extremely competitive. Our ability to grant equity awards is critical to our ability to be competitive and to attract, retain and motivate the talent we need to best position our Company for success.

In consideration of these factors, and our belief that the ability to continue granting equity compensation is vital to our attracting and retaining employees and facilitating long-term stockholder value creation, including by retaining and incentivizing our executives and other employees, we believe that the 2025 Plan and the size of the share reserve under the 2025 Plan are reasonable, appropriate and in the best interests of the Company at this time.

Summary of the 2025 Plan

This section summarizes certain principal features of the 2025 Plan. The summary is qualified in its entirety by reference to the complete text of the 2025 Plan, which is attached to this proxy statement as Appendix A.

Eligibility and Administration

Our employees, consultants and directors, and employees and consultants of our subsidiaries, are eligible to receive awards under the 2025 Plan. As of February 13, 2025, approximately 103 employees and 8 non-employee directors were eligible to receive awards under the 2025 Plan. The 2025 Plan is administered by our Compensation and Talent Committee, although the Board may exercise any powers and responsibilities assigned to the Compensation and Talent Committee at any time. The Board may also delegate its duties and responsibilities to one or more other committees of our directors and/or to officers of the Company, subject to the limitations imposed under the 2025 Plan, Section 16 of the Exchange Act, stock exchange rules and other applicable laws. The actual administrator of the 2025 Plan is referred to as the “plan administrator” in this Proposal. The plan administrator has the authority to take all actions and make all determinations under the 2025 Plan, to interpret the 2025 Plan and award agreements and to adopt, amend and repeal rules for the administration of the 2025 Plan as it deems advisable. The plan administrator also has the authority to determine which eligible service providers receive awards, grant awards and set the terms and conditions of all awards under the 2025 Plan, including any vesting and vesting acceleration provisions, subject to the conditions and limitations in the 2025 Plan.

Shares Available for Awards

If the 2025 Plan is approved, the number of shares reserved for issuance under the 2025 Plan will be equal to the sum of (i) 44,604,870 shares; and (ii) any shares that are subject to awards under the 2012 Plan which are forfeited or lapse unexercised and which are not issued under the 2012 Plan. As of February 13, 2025, there were 5,400 shares subject to awards outstanding under the 2012 Plan. No more than 44,610,270 shares may be issued under the 2025 Plan upon the exercise of incentive stock options. Shares issued under the 2025 Plan may be authorized but unissued shares, shares purchased on the open market or treasury shares.

If an award under the 2025 Plan or the 2012 Plan, expires, lapses or is terminated, exchanged for cash, surrendered, repurchased, canceled without having been fully exercised or forfeited, any unused shares subject to the award will, as applicable, become or again be available for new grants under the 2025 Plan. However, the 2025 Plan does not allow the share pool to be replenished with shares that (i) are used to satisfy the exercise or purchase price of an award; (ii) are used to satisfy tax withholding obligations arising from an award; (iii) are subject to a stock appreciation right but are not issued in connection with the stock settlement of the stock appreciation right; or (iv) the Company purchases on the open market with cash proceeds from the exercise of options.

Director Compensation Limit

The sum of any cash or other compensation and the value (determined as of the grant date in accordance with ASC 718, or any successor thereto), of awards granted to any non-employee director for services as a director pursuant to the 2025 Plan during any fiscal year may not exceed $750,000, increased to $1,000,000 in the first year an individual becomes a non-employee director. The plan administrator may, however, make exceptions to such limit on director compensation in extraordinary circumstances, subject to the limitations in our 2025 Plan.

Awards

The 2025 Plan provides for the grant of options, including incentive stock options, or ISOs, and nonqualified options, or NSOs, stock appreciation rights, or SARs, restricted stock, dividend equivalents, restricted stock units, or RSUs, and other

stock or cash based awards. Certain awards under the 2025 Plan may constitute or provide for payment of “nonqualified deferred compensation” under Section 409A of the Code. All awards under the 2025 Plan are set forth in award agreements, which detail the terms and conditions of awards, including any applicable vesting and payment terms and post-termination exercise limitations. A brief description of each award type follows

Performance Criteria

The plan administrator may select performance criteria for an award to establish performance goals for a performance period. Performance criteria under the 2025 Plan may include, but are not limited to, the following: net earnings or losses (either before or after one or more of interest, taxes, depreciation, amortization, and non-cash equity-based compensation expense); gross or net sales or revenue or sales or revenue growth; net income (either before or after taxes) or adjusted net income; profits (including but not limited to gross profits, net profits, profit growth, net operation profit or economic profit), profit return ratios or operating margin; budget or operating earnings (either before or after taxes or before or after allocation of corporate overhead and bonus); cash flow (including operating cash flow and free cash flow or cash flow return on capital); return on assets; return on capital or invested capital; cost of capital; return on stockholders’ equity; total stockholder return; return on sales; costs, reductions in costs and cost control measures; expenses; working capital; earnings or loss per share; adjusted earnings or loss per share; price per share or dividends per share (or appreciation in or maintenance of such price or dividends); regulatory achievements or compliance; implementation, completion or attainment of objectives relating to research, development, regulatory, commercial, or strategic milestones or developments; market share; economic value or economic value added models; division, group or corporate financial goals; customer satisfaction/growth; customer service; employee satisfaction; recruitment and maintenance of personnel; human resources management; supervision of litigation and other legal matters; strategic partnerships and transactions; financial ratios (including those measuring liquidity, activity, profitability or leverage); debt levels or reductions; sales-related goals; financing and other capital raising transactions; cash on hand; acquisition activity; investment sourcing activity; and marketing initiatives, any of which may be measured in absolute terms or as compared to any incremental increase or decrease, peer group results, or market performance indicators or indices.

Certain Transactions

In connection with certain corporate transactions and events affecting our common stock, including a change in control, or change in any applicable laws or accounting principles, the plan administrator has broad discretion to take action under the 2025 Plan to prevent the dilution or enlargement of intended benefits, facilitate the transaction or event or give effect

to the change in applicable laws or accounting principles. This includes canceling awards for cash or property, accelerating the vesting of awards, providing for the assumption or substitution of awards by a successor entity, adjusting the number and type of shares subject to outstanding awards and/or with respect to which awards may be granted under the 2025 Plan and replacing or terminating awards under the 2025 Plan. Notwithstanding the foregoing, in the event awards are not assumed or substituted in connection with a change in control, such awards (other than awards that are regularly scheduled to vest based on performance-based vesting conditions) will become fully vested, exercisable and/or payable, as applicable, immediately prior to the consummation of the transaction and all forfeiture, repurchase and other restrictions will lapse. In addition, in the event of certain non-reciprocal transactions with our stockholders, the plan administrator will make equitable adjustments to the 2025 Plan and outstanding awards as it deems appropriate to reflect the transaction.

All share and per share amounts referenced in this Proposal are stated without giving effect to, and will be adjusted for, the reverse stock split proposed in Proposal 5 of this proxy statement, if this Proposal is approved.

Plan Amendment and Termination

Our Board may amend or terminate the 2025 Plan at any time; however, no amendment, other than an amendment that increases the number of shares available under the 2025 Plan, may materially and adversely affect an award outstanding under the 2025 Plan without the consent of the affected participant and stockholder approval will be obtained for any amendment to the extent necessary to comply with applicable laws. The 2025 Plan will remain in effect until March 3, 2035, the tenth anniversary of the date the Board approved the 2025 Plan, unless earlier terminated by the Board. No awards may be granted under the 2025 Plan after its termination.

No Repricings without Stockholder Approval

The plan administrator cannot, without the approval of our stockholders, reduce the exercise price of outstanding options or SARs, or cancel outstanding options or SARs, in exchange for cash, other awards under the 2025 Plan or options or SARs with an exercise price per share that is less than the exercise price per share of the original options or SARs.

Foreign Participants, Claw-Back Provisions, Transferability and Participant Payments

The plan administrator may modify awards granted to participants who are foreign nationals or employed outside the United States or establish subplans or procedures to address differences in laws, rules, regulations or customs of such foreign jurisdictions. All awards will be subject to the Company’s Policy for Recovery of Erroneously Awarded Compensation and any other clawback, recoupment, forfeiture or similar policies or provisions of the Company. Except as the plan administrator may determine or provide in an award agreement, awards under the 2025 Plan are generally non-transferrable, except by will or the laws of descent and distribution, or, subject to the plan administrator’s consent, pursuant to a domestic relations order, and are generally exercisable only by the participant. With regard to tax withholding obligations arising in connection with awards under the 2025 Plan, and exercise price obligations arising in connection with the exercise of options under the 2025 Plan, the plan administrator may, in its discretion, accept cash, wire transfer or check, shares of our common stock that meet specified conditions, a promissory note, a “market sell order,” such other consideration as the plan administrator deems suitable or any combination of the foregoing.

Interests of Certain Persons in the 2025 Plan

In considering the recommendation of the Board with respect to the approval of the 2025 Plan, stockholders should be aware that, as discussed above, non-employee directors and executive officers are eligible to receive awards under the 2025 Plan. The Board recognizes that approval of this Proposal may benefit our non-employee directors and executive officers and their successors.

Federal Income Tax Consequences

The following is a general summary as of this date of the federal income tax consequences to us and to U.S. participants for awards granted under the 2025 Plan. The federal tax laws may change and the tax consequences for any participant will depend upon his or her individual circumstances. Tax consequences for any particular individual may be different. This summary does not purport to be complete, and does not discuss state, local or non-U.S. tax consequences.

Non-Qualified Options. The grant of a non-qualified option under the 2025 Plan is not expected to result in any federal income tax consequences to the participant or to the Company. Generally, upon exercise of a non-qualified option,

the participant will realize ordinary income, and the Company will be entitled to a tax deduction, in an amount equal to the difference between the option exercise price and the fair market value of the shares at the time of exercise.

Incentive Stock Options. The grant or exercise of an ISO under the 2025 Plan is not expected to result in any federal income tax consequences to the participant or to the Company. However, the amount by which the fair market value of the shares at the time of exercise exceeds the option price will be an “item of adjustment” for participants for purposes of the alternative minimum tax, unless the shares are sold or otherwise disposed of in the same year the ISO is exercised. Gain realized by participants on the sale of shares underlying an ISO is taxable at capital gains rates, and no tax deduction is available to the Company, unless the participant disposes of the shares within (i) two years after the date of grant of the option or (ii) within one year of the date the shares were transferred to the participant. If the shares are sold or otherwise disposed of before the end of the one-year and two-year periods specified above, the difference between the option exercise price and the fair market value of the shares on the date of the option’s exercise (or the date of sale, if less) will be taxed at ordinary income rates, and the Company will be entitled to a deduction to the extent that the participant recognizes ordinary income.

Stock Appreciation Rights. The grant of a SAR under the 2025 Plan is not expected to result in any federal income tax consequences to either the participant or the Company. Generally, upon exercise of the SAR, the fair market value of the shares received, determined on the date of exercise of the SAR, or the amount of cash received in lieu of shares, will be treated as compensation taxable as ordinary income to the participant in the year of such exercise. The Company will be entitled to a deduction for compensation paid in the same amount which the participant realized as ordinary income.

Restricted Stock. A participant generally will not have taxable income on the grant of restricted stock under the 2025 Plan, nor will the Company then be entitled to a deduction, unless the participant makes a valid election under Section 83(b) of the Code. However, when restrictions on shares of restricted stock lapse, such that the shares are no longer subject to a substantial risk of forfeiture, the participant generally will recognize ordinary income, and the Company will be entitled to a corresponding deduction, for an amount equal to the difference between the fair market value of the shares on the date such restrictions lapse over the purchase price for the restricted stock.

Restricted Stock Units. A participant generally will not realize taxable income at the time of the grant of RSUs under the 2025 Plan, and the Company will not be entitled to a deduction at that time. When RSUs are settled, whether in cash or shares, the participant will have ordinary income, and the Company will be entitled to a corresponding deduction.

Stock Awards. If a participant receives a stock award under the 2025 Plan in lieu of a cash payment that would otherwise have been made, the participant generally will be taxed as if the cash payment has been received, and the Company will have a deduction in the same amount.

Dividend Equivalents. A participant generally will not realize taxable income at the time of the grant of dividend equivalents under the 2025 Plan, and the Company will not be entitled to a deduction at that time. When a dividend equivalent is paid, the participant will recognize ordinary income, and the Company will be entitled to a corresponding deduction.

Application of Section 409A of the Code. Section 409A of the Code imposes an additional 20% tax and interest on an individual receiving non-qualified deferred compensation under a plan that fails to satisfy certain requirements. For purposes of Section 409A, “non-qualified deferred compensation” includes equity-based incentive programs, including some options, SARs and RSU programs. Generally speaking, Section 409A does not apply to ISOs, non-discounted non-qualified options and SARs if no deferral is provided beyond exercise, or restricted stock.

The awards made pursuant to the 2025 Plan are expected to be designed in a manner intended to comply with the requirements of Section 409A to the extent the awards granted under the 2025 Plan are not exempt from Section 409A. However, if the 2025 Plan fails to comply with Section 409A in operation, a participant could be subject to the additional taxes and interest.

Limitations on the Company's Compensation Deduction. Section 162(m) of the Code limits the deduction certain employers may take for otherwise deductible compensation payable to certain current and former executive officers of the Company to the extent the compensation paid to such an officer for the year exceeds $1 million. Compensation deductions may also be limited by Section 280G of the Code.

New Plan Benefits

Other than with respect to awards that will be made automatically under our non-employee director compensation program as described in the footnote to the New Plan Benefits Table below, the benefits or amounts that may be received or allocated to participants under the 2025 Plan are subject to the discretion of the Compensation and Talent Committee or the Board and are not currently determinable. The following table sets forth the awards to be granted under our non-employee director compensation program irrespective of whether the 2025 Plan is approved by the stockholders.

Additional Prior Award Information

The following table sets forth, with respect to the individuals and groups identified therein, the number of shares subject to options, RSUs and PSUs that have been granted to such individuals and groups under the 2015 Plan through February 13, 2025:

VOTE REQUIRED

This Proposal requires the affirmative vote of the holders of a majority of the votes cast affirmatively or negatively. Abstentions and broker non-votes will have no effect on this Proposal.

RECOMMENDATION OF THE BOARD OF DIRECTORS

The Board of Directors unanimously recommends a vote “FOR” the approval of the Seres Therapeutics, Inc. 2025 Incentive Award Plan.

PROPOSAL 5

Approval of Amendments to our Certificate of Incorporation to Effect a Reverse Stock Split

General

Our Board has adopted and is recommending that our stockholders approve amendments to our Certificate of Incorporation, to effect a reverse stock split of our common stock at a ratio ranging from any whole number between 1‑for‑5 and 1‑for‑50, with the exact ratio within such range to be determined by the Board in its discretion (the “Reverse Stock Split”), subject to the Board’s authority to determine when to file the amendment and to abandon the other amendments notwithstanding prior stockholder approval of such amendments. Pursuant to the law of the State of Delaware, our state of incorporation, the Board must adopt any amendment to our Certificate of Incorporation and submit the amendment to stockholders for their approval. The form of the proposed amendments to our Certificate of Incorporation, one of which would be filed with the Secretary of State of the State of Delaware, are attached to this proxy statement as Appendix B.

By approving this Proposal, stockholders will approve alternative amendments to our Certificate of Incorporation pursuant to which a whole number of outstanding shares of our common stock between 5 and 50, inclusive, would be combined into one share of our common stock. Upon receiving stockholder approval, the Board will have the authority, in its sole discretion, but not the obligation, to elect, without further action on the part of the stockholders, whether to effect the Reverse Stock Split and, if so, to determine the Reverse Stock Split ratio from among the approved range described above and to effect the Reverse Stock Split by filing a Certificate of Amendment with the Secretary of State of the State of Delaware. In this case, all other amendments will be abandoned. The Board may also elect not to effect any Reverse Stock Split.

The Board’s decision as to whether and when to effect the Reverse Stock Split will be based on a number of factors, including market conditions, the historical, then‑existing and expected trading price of our common stock, the anticipated impact of the Reverse Stock Split on the trading price of our common stock and on the number of holders of our common stock, and the continued listing requirements of The Nasdaq Global Select Market. Although our stockholders may approve the Reverse Stock Split, we will not effect the Reverse Stock Split if the Board does not deem it to be in the best interests of the Company and its stockholders.

Because the Reverse Stock Split will decrease the number of outstanding shares of our common stock by a ratio in the range of 1‑for‑5 to 1‑for‑50 but would not effect a decrease to the number of shares of common stock that the Company will be authorized to issue, the proposed amendments to the Certificate of Incorporation to effect the Reverse Stock Split (the “Reverse Stock Split amendments”) would result in a relative increase in the number of authorized and unissued shares of our common stock. For more information on the relative increase in the number of authorized shares of our common stock, see “Principal Effects of the Reverse Stock Split‑Relative Increase in Number of Authorized Shares of Common Stock for Issuance” below.

Purpose and Background of the Reverse Stock Split

On March 3, 2025, the Board approved the proposed amendments to our Certificate of Incorporation to effect the Reverse Stock Split for the following reasons:

Nasdaq Requirements for Continued Listing

Our common stock is quoted on The Nasdaq Global Select Market under the symbol “MCRB.” One of the requirements for continued listing on The Nasdaq Global Select Market pursuant to Nasdaq Listing Rule 5450(a)(1) is maintenance of a minimum closing bid price of $1.00 per share. On February 28, 2025, the closing market price per share of our common stock was $0.759, as reported by The Nasdaq Global Select Market.

On November 7, 2024, we received a written notification from The Nasdaq Stock Market LLC (“Nasdaq”) notifying us that we had failed to comply with the minimum bid price requirement because the bid price for our common stock over a period of 30 consecutive business days prior to such date had closed below the minimum $1.00 per share requirement (the “Bid Price Requirement”). In accordance with Nasdaq Listing Rule 5810(c)(3)(A), we have been provided an initial period of 180 calendar days, or until May 6, 2025, to regain compliance with the minimum Bid Price Requirement of $1.00 per share. However, if it appears to the Nasdaq staff that we will not be able to cure the deficiency, or if we are otherwise not eligible, Nasdaq would notify us that our securities would be subject to delisting (a “Staff Delisting Determination”). In addition, if we have a closing bid price of $0.10 or less for a period of ten consecutive business days, Nasdaq would also issue a Staff Delisting Determination letter. In the event of either such notification, we may appeal the Nasdaq staff’s determination to delist its securities.

If we do not regain compliance within the applicable compliance period, we expect that Nasdaq will issue us a Staff Delisting Determination. At that time, we may appeal the delisting determination to a Nasdaq Listing Qualifications Panel.

There can be no assurance that we will be able to regain compliance with the Bid Price Requirement, will otherwise be in compliance with other applicable Nasdaq listing rules within the applicable compliance period, will be able to successfully implement a reverse stock split, or, if we receive a Staff Delisting Determination and decide to appeal it, that such appeal would be successful.

If our common stock is delisted from The Nasdaq Global Select Market, we cannot assure you that our common stock would be listed on another national securities exchange, a national quotation service, the over‑the‑counter markets or the pink sheets. Delisting from The Nasdaq Global Select Market, or even the issuance of a notice of potential delisting, would also result in negative publicity, make it more difficult for us to raise additional capital, adversely affect the market liquidity of our securities, decrease securities analysts’ coverage of us or diminish investor, supplier and employee confidence.

Facilitation of Future Capital Raising

The Board believes it is critically important for the Company to maintain its flexibility in accessing the equity capital markets. As of the date of our filing of our Quarterly Report on Form 10-Q for the quarter ended September 30, 2024, there was substantial doubt regarding our ability to continue as a going concern. As noted therein, the Company’s ability to continue as a going concern was dependent upon its ability to obtain the necessary financing to meet its obligations and repay its liabilities arising from normal business operations when they come due, and to generate profitable operations in the future.

We intend to explore different potential financing strategies to help support the Company’s capital requirements, including equity or debt financing, such as a private investment in common stock or preferred equity securities, convertible debt securities or other debt financing, at-the-market offerings of our common stock, rights offering or other public offering of equity or debt securities, research funding, collaborations, contract and grant revenue, or other sources, in each case, as a standalone transaction or as part of a larger financing transaction. The availability of financing will depend on potential collaborators’ interest in our business, potential investors’ willingness to participate in any future financings, as well as market conditions. There can be no assurance that such financing will be available in amounts or on terms acceptable to us, if at all, or that we will be able to raise capital to fund our operations and to continue as a going concern.

The sale of additional equity, however, would result in significant dilution to our stockholders. Additionally, the incurrence of debt financing would result in debt service obligations and could provide for restrictive operating and financial covenants, security interests on our assets, and other terms that could be adverse to our current stakeholders. Nonetheless, we believe that failure to raise additional capital through equity or debt financing could have a material adverse effect on our ability to meet our short- and long-term liquidity needs and achieve our business objectives.

The Board believes that the Reverse Stock Split would facilitate the Company’s ability to raise additional equity capital in particular, including due to the expected resulting increase in the per share price of our common stock, as described under “Potential Increased Investor Interest” below. The Board believes that an increased price per share of common stock following a Reverse Stock Split would enhance the Company’s ability to raise capital to fund its current operations, and to otherwise take advantage of favorable opportunities as they arise.

Potential Increased Investor Interest

In approving the proposed Reverse Stock Split amendments, the Board considered that the Reverse Stock Split and the expected resulting increase in the per share price of our common stock could encourage increased investor interest in our common stock and promote greater liquidity for our stockholders.

In the event that our common stock were to be delisted from The Nasdaq Global Select Market, our common stock would likely trade in the over‑the‑counter market. If our common stock were to trade on the over‑the‑counter market, selling our common stock could be more difficult because smaller quantities of shares would likely be bought and sold, and transactions could be delayed. In addition, many brokerage houses and institutional investors have internal policies and practices that prohibit them from investing in low‑priced stocks or tend to discourage individual brokers from recommending low‑priced stocks to their customers, further limiting the liquidity of our common stock. These factors could result in lower prices and larger spreads in the bid and ask prices for our common stock. Additionally, investors may be dissuaded from purchasing lower priced stocks because the brokerage commissions, as a percentage of the total transaction, tend to be higher for such stocks. Moreover, the analysts at many brokerage firms do not monitor the trading activity or otherwise provide coverage of lower priced stocks. A greater price per share of our common stock could allow a broader range of institutions to invest in our common stock. For all of these reasons, we believe the Reverse Stock Split could potentially increase marketability, trading volume, and liquidity of our common stock.

Employee Retention

The Board believes that the Company’s employees and directors who are compensated in the form of our equity‑based securities may be less incentivized and invested in the Company if we are no longer listed on Nasdaq. Accordingly, the Board believes that maintaining Nasdaq listing qualifications for our common stock can help attract, retain, and motivate employees and members of our Board.

In light of the factors mentioned above, our Board unanimously approved the proposed amendments to our Certificate of Incorporation to effect the Reverse Stock Split as a potential means of increasing and maintaining the price of our common stock to above $1.00 per share in compliance with Nasdaq requirements.

Board Discretion to Implement the Reverse Stock Split

The Board believes that stockholder approval of a range of ratios (as opposed to a single Reverse Stock Split ratio) is in the best interests of our Company and stockholders because it is not possible to predict market conditions at the time that the Reverse Stock Split would be effected. We believe that a range of Reverse Stock Split ratios provides us with the most flexibility to achieve the desired results of the Reverse Stock Split. The Reverse Stock Split ratio to be selected by our Board will be a whole number in a range of 1‑for‑5 to 1‑for‑50. Even though this Proposal seeks stockholder approval to grant the Board the authority to set any whole number ratio for the Reverse Stock Split within this range, the Board can only authorize the filing of one Reverse Stock Split amendment and all other Reverse Stock Split amendments will be abandoned. The Board also has the authority to abandon all Reverse Stock Split amendments.

In determining the Reverse Stock Split ratio and whether and when to effect the Reverse Stock Split following the receipt of stockholder approval, the Board will consider a number of factors, including, without limitation:

We believe that granting the Board the authority to set the ratio for the Reverse Stock Split is essential because it allows us to take these factors into consideration and to react to changing market conditions. If our Board chooses to implement the Reverse Stock Split, we will make a public announcement regarding the determination of the Reverse Stock Split ratio.

Risks Associated with the Reverse Stock Split

There are risks associated with the Reverse Stock Split, including that the Reverse Stock Split may not result in a sustained increase in the per share price of our common stock. There is no assurance that:

Stockholders should note that the effect of the Reverse Stock Split, if any, upon the market price of our common stock cannot be accurately predicted. In particular, we cannot assure you that the price for a share of our common stock after the Reverse Stock Split will increase in proportion to the reduction in the number of shares of our common stock outstanding immediately prior to the Reverse Stock Split. Furthermore, even if the market price of our common stock does rise following the Reverse Stock Split, we cannot assure you that the market price of our common stock immediately after the Reverse Stock Split will be maintained for any period of time. Even if an increased per‑share price can be maintained, the Reverse Stock Split may not achieve the desired results that have been outlined above.

Moreover, because some investors may view the Reverse Stock Split negatively, we cannot assure you that the Reverse Stock Split will not adversely impact the market price of our common stock.

While we aim that the Reverse Stock Split will be sufficient to satisfy the Minimum Bid Requirement, it is possible that, even if the Reverse Stock Split results in a bid price for our common stock that exceeds $1.00 per share, we may not be able to continue to satisfy Nasdaq’s additional criteria for continued listing of our common stock on The Nasdaq Global Select Market.

We believe that the Reverse Stock Split may result in greater liquidity for our stockholders. However, it is also possible that such liquidity could be adversely affected by the reduced number of shares outstanding after the Reverse Stock Split, particularly if the price of our common stock does not increase as a result of the Reverse Stock Split.

Principal Effects of the Reverse Stock Split

Issued and Outstanding Shares of Common Stock

If the Reverse Stock Split is approved and effected, each holder of our common stock outstanding immediately prior to the effectiveness of the Reverse Stock Split will own a reduced number of shares of our common stock upon effectiveness of the Reverse Stock Split. The Reverse Stock Split will be effected simultaneously for all issued and outstanding shares of common stock and the Reverse Stock Split ratio will be the same for all issued and outstanding shares of common stock. The Reverse Stock Split will affect all of our stockholders uniformly and will not affect any stockholder’s percentage ownership interests in the Company, except to the extent that the Reverse Stock Split results in any of our stockholders owning a fractional share. After the Reverse Stock Split, the shares of our common stock will have the same voting rights and rights to dividends and distributions and will be identical in all other respects to our common stock now authorized. Common stock issued pursuant to the Reverse Stock Split will remain fully paid and non‑assessable. The Reverse Stock Split will not affect the Company continuing to be subject to the periodic reporting requirements of the Securities Exchange Act of 1934, as amended (the “Exchange Act”).

The Reverse Stock Split may result in some stockholders owning “odd‑lots” of less than 100 shares of our common stock. Brokerage commissions and other costs of transactions in odd‑lots are generally higher than the costs of transactions in “round‑lots” of even multiples of 100 shares.

Relative Increase in Number of Authorized Shares of Common Stock for Issuance

The Reverse Stock Split will not affect the number of authorized shares or the par value of our capital stock, which will remain at 360,000,000 shares of common stock, par value $0.001 per share, and 10,000,000 shares of preferred stock, par value $0.001 per share (“Preferred Stock,” and together with our common stock, our “Capital Stock”).

Although the number of authorized shares of our Capital Stock will not change as a result of the Reverse Stock Split, the number of shares of our common stock issued and outstanding will be reduced in proportion to the ratio selected by the Board. Thus, the Reverse Stock Split will effectively increase the number of authorized and unissued shares of our common stock available for future issuance by the amount of the reduction effected by the Reverse Stock Split.

If the proposed Reverse Stock Split amendments are approved, all or any of the authorized and unissued shares of our common stock may be issued in the future for such corporate purposes and such consideration as the Board deems advisable from time to time, without further action by the stockholders of our Company and without first offering such shares to our stockholders. When and if additional shares of our common stock are issued, these new shares would have the same voting and other rights and privileges as the currently issued and outstanding shares of common stock, including the right to cast one vote per share.

Because our stockholders have no preemptive rights to purchase or subscribe for any of our unissued shares of common stock, the future issuance of additional shares of common stock will reduce our current stockholders’ percentage ownership interest in the total outstanding shares of common stock. In the absence of a proportionate increase in our future earnings and book value, an increase in the number of our outstanding shares of common stock would dilute our projected future earnings per share, if any, and book value per share of all our outstanding shares of common stock. If these factors were reflected in the price per share of our common stock, the potential realizable value of a stockholder’s investment could be adversely affected. An issuance of additional shares could therefore have an adverse effect on the potential realizable value of a stockholder’s investment.

Effect on Outstanding Equity Incentive Plans and Warrants

The Company maintains the 2015 Plan (which will be amended and restated as the 2025 Plan if Proposal 4 is approved by our stockholders), the 2015 ESPP, the 2012 Plan and the 2022 Inducement Award Plan (collectively, the “Plans”), which are designed primarily to provide stock‑based incentives to employees and directors of the Company. As of February 13, 2025, options to purchase 26,551,776 shares of our common stock (which does not include outstanding purchase rights under our 2015 ESPP) and 1,628,579 restricted stock units were outstanding under the Plans. In the event of a reverse stock split, our Board generally has the discretion to determine the appropriate adjustment to awards granted and share‑based limits under the Plans. Accordingly, if the Reverse Stock Split is approved by our stockholders and our Board decides to implement the Reverse Stock Split, as of the Effective Time (as defined below) the number of shares of common stock issuable upon exercise, vesting or settlement of outstanding awards, the exercise price of all outstanding options and any stock price vesting goals with respect to any outstanding awards under the Plans will be proportionately adjusted (and rounded down to the nearest whole share in the case of shares and up to the nearest whole cent in the case of exercise prices, as applicable) based on the Reverse Stock Split ratio selected by our Board, subject to the terms of such Plans, options, and restricted stock units, as applicable. In addition, the number of shares available for future issuance and any share‑based award limits under the Plans will be proportionately reduced based on the Reverse Stock Split ratio selected by our Board.

In addition, we have issued to third party investors and others warrants to purchase shares of our common stock. As of February 13, 2025, we had issued and outstanding warrants to purchase up to 647,589 shares of our common stock. If the Reverse Stock Split is approved by our stockholders and our Board decides to implement the Reverse Stock Split, as of the Effective Time, the number of shares issuable upon exercise will be reduced proportionally and the exercise price of the Company’s outstanding warrants will be increased proportionately based on the Reverse Stock Split ratio selected by our Board.

Our Board has also authorized the Company to effect any other changes necessary, desirable or appropriate to give effect to the Reverse Stock Split, including any applicable technical, conforming changes.

Effects of the Amendment on our Common Stock

After the Effective Time, each stockholder will own fewer shares of our common stock as a result of the Reverse Stock Split. Because the Reverse Stock Split will decrease the number of outstanding shares of our common stock, the proposed amendments will result in a relative increase in the number of authorized and unissued shares of our common stock. All outstanding options to purchase shares of our common stock, including any held by our officers and directors,

would be adjusted as a result of the Reverse Stock Split. In particular, the number of shares issuable upon the exercise of each instrument would be reduced, and the exercise price per share, if applicable, would be increased, in accordance with the terms of each instrument and based on the ratio of the Reverse Stock Split.

The chart below outlines the capital structure as described in this Proposal and prior to and immediately following a possible Reverse Stock Split if the Reverse Stock Split is effected at a ratio of 1‑for‑5, 1‑for‑20, 1‑for‑35, or 1‑for‑50 based on share information as of the close of business on February 13, 2025, but does not give effect to any other changes, including any issuance of securities after February 13, 2025.

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

Procedure for Effecting Reverse Stock Split and Exchange of Stock Certificates, if Applicable

If the proposed amendments to our Certificate of Incorporation are approved by the Company’s stockholders and the Board determines to effect the Reverse Stock Split, the Reverse Stock Split will become effective at 5:00 p.m. Eastern time on the date the certificate of amendment is filed with the Secretary of State of the State of Delaware (the “Effective Time”). At the Effective Time, shares of common stock issued and outstanding immediately prior thereto will be combined, automatically and without any action on the part of the stockholders, into new shares of common stock in accordance with the Reverse Stock Split ratio contained in the certificate of amendment.

As soon as practicable after the Effective Time, stockholders will be notified by our transfer agent that the Reverse Stock Split has been effected. If you hold shares of common stock in book‑entry form, you will not need to take any action to receive post‑Reverse Stock Split shares of our common stock. As soon as practicable after the Effective Time, the Company’s transfer agent will send to your registered address a transmittal letter along with a statement of ownership indicating the number of post‑Reverse Stock Split shares of common stock you hold. If applicable, a check representing a cash payment in lieu of fractional shares will also be mailed to your registered address as soon as practicable after the Effective Time (see “Fractional Shares” below).

Some stockholders may hold their shares of common stock in certificate form. Our transfer agent will act as exchange agent for purposes of implementing the exchange of stock certificates, if applicable. If you are a stockholder holding pre‑Reverse Stock Split shares in certificate form, you will receive a transmittal letter from the Company’s transfer agent as soon as practicable after the Effective Time. The transmittal letter will be accompanied by instructions specifying how you can exchange your certificate or certificates representing the pre‑Reverse Stock Split shares of our common stock for a statement of ownership. When you submit your certificate or certificates representing the pre‑Reverse Stock Split shares of our common stock, your post‑Reverse Stock Split shares of our common stock will be held electronically in book‑entry form in the Direct Registration System. This means that, instead of receiving a new stock certificate representing the aggregate number of post‑Reverse Stock Split shares you own, you will receive a statement indicating the number of post‑Reverse Stock Split shares you own in book‑entry form. We will no longer issue physical stock certificates.

STOCKHOLDERS SHOULD NOT DESTROY ANY STOCK CERTIFICATE(S) AND SHOULD NOT SUBMIT ANY CERTIFICATE(S) UNTIL REQUESTED TO DO SO.

Beginning at the Effective Time, each certificate representing pre‑Reverse Stock Split shares will be deemed for all corporate purposes to evidence ownership of post‑Reverse Stock Split shares.

Fractional Shares

No scrip or fractional shares would be issued if, as a result of the Reverse Stock Split, a stockholder would otherwise become entitled to a fractional share because the number of shares of common stock they hold before the Reverse Stock Split is not evenly divisible by the split ratio ultimately determined by the Board. Instead, each stockholder will be entitled to receive a cash payment in lieu of such fractional share. The cash payment to be paid will be equal to the fraction of a share to which such stockholder would otherwise be entitled multiplied by the closing price per share as reported by The Nasdaq Global Select Market, as adjusted to give effect to the Reverse Stock Split, on the date of the Effective Time. The Company will not assess any transaction costs to stockholders for the cash payment. Stockholders would not be entitled to receive interest for their fractional shares for the period of time between the Effective Time and the date payment is received.

After the Reverse Stock Split, then‑current stockholders would have no further interest in our Company with respect to their fractional shares. A person entitled to only a fractional share would not have any voting, dividend or other rights in respect of their fractional share except to receive the cash payment as described above. Such cash payments would reduce the number of post‑Reverse Stock Split stockholders to the extent that there are stockholders holding fewer than that number of pre‑Reverse Stock Split shares within the Reverse Stock Split ratio that is determined by the Board as described above. Reducing the number of post‑Reverse Stock Split stockholders, however, is not the purpose of this Proposal.

Stockholders should be aware that, under the escheat laws of the various jurisdictions where stockholders reside, where we are domiciled and where the funds for fractional shares would be deposited, sums due to stockholders in payment for fractional shares that are not timely claimed after the Effective Time may be required to be paid to the designated agent for each such jurisdiction. Thereafter, stockholders otherwise entitled to receive such funds may have to seek to obtain them directly from the state to which they were paid.

No Appraisal Rights

Under the Delaware General Corporation Law, the Company’s stockholders will not be entitled to appraisal rights with respect to the Reverse Stock Split, and we do not intend to independently provide stockholders with any such right.

No Going Private Transaction

Notwithstanding the decrease in the number of outstanding shares following the Reverse Stock Split, the Board does not intend for this transaction to be the first step in a series of plans or proposals of a “going private transaction” within the meaning of Rule 13e‑3 of the Exchange Act.

Interests of Certain Persons in the Proposal

Certain of our officers and directors have an interest in this Proposal 5 as a result of their ownership of shares of our common stock, as set forth in the section entitled “Security Ownership of Certain Beneficial Owners and Management” below. However, we do not believe that our officers or directors have interests in this Proposal 5 that are different from or greater than those of any of our other stockholders.

Anti‑takeover Effects of Proposed Amendments

Release No. 34‑15230 of the staff of the SEC requires disclosure and discussion of the effects of any action, including the proposed amendments to our Certificate of Incorporation discussed herein, that may be used as an anti‑takeover mechanism. An additional effect of the Reverse Stock Split would be to increase the relative amount of authorized but unissued shares of our common stock, which may, under certain circumstances, be construed as having an anti‑takeover effect. Although not intended for such purposes, the effect of the increased available shares could be to render more difficult or discourage an attempt to take over or otherwise obtain control of the Company (for example, by permitting issuances that would dilute the stock ownership of a person or entity seeking to effect a change in the composition of the Board or contemplating a tender offer or other change in control transaction). In addition, our Certificate of Incorporation and our Bylaws include provisions that may have an anti‑takeover effect. These provisions, among things, permit the Board to issue preferred stock with rights senior to those of the common stock without any further vote or action by the stockholders and do not provide for cumulative voting rights, which could make it more difficult for stockholders to effect certain corporate actions and may delay or discourage a change in control.

Our Board is not presently aware of any attempt to acquire control of the Company, and the Reverse Stock Split proposal is not part of any plan by our Board to recommend or implement a series of anti‑takeover measures.

Accounting Treatment of the Reverse Stock Split

If the Reverse Stock Split is effected, the par value per share of our common stock will remain unchanged at $0.001. Accordingly, at the Effective Time, the stated capital on the Company’s consolidated balance sheets attributable to our common stock will be reduced in proportion to the size of the Reverse Stock Split ratio, and the additional paid‑in‑capital account will be increased by the amount by which the stated capital is reduced. Our stockholders’ equity, in the aggregate, will remain unchanged as a result of the Reverse Stock Split. Per share net income or loss will be increased because there will be fewer shares of common stock outstanding. The Company does not anticipate that any other accounting consequences, including changes to the amount of stock‑based compensation expense to be recognized in any period, will arise as a result of the Reverse Stock Split.

Material U.S. Federal Income Tax Consequences of the Reverse Stock Split

The following discussion is a summary of material U.S. federal income tax consequences of the Reverse Stock Split to U.S. Holders (as defined below) of our common stock, but does not purport to be a complete analysis of all potential tax effects. The effects of other U.S. federal tax laws, such as estate and gift tax laws, and any applicable state, local, or non-U.S. tax laws are not discussed. This summary is based upon the provisions of the U.S. Internal Revenue Code of 1986, as amended, or the Code, Treasury regulations promulgated thereunder, published rulings and administrative pronouncements of the U.S. Internal Revenue Service, or the IRS, and judicial decisions, all as in effect as of the date hereof, and all of which are subject to change and differing interpretations, possibly with retroactive effect. Changes in these authorities or their interpretation may result in the U.S. federal income tax consequences of the Reverse Stock Split differing substantially from the consequences summarized below. We have not sought, and will not seek, an opinion of counsel or a ruling from the IRS regarding the U.S. federal income tax consequences of the Reverse Stock Split, and there can be no assurance that the IRS will not challenge the statements and conclusions set forth below or that a court would not sustain any such challenge.

This discussion is limited to U.S. Holders that hold our common Stock as a “capital asset” within the meaning of Section 1221 of the Code (generally, property held for investment). This discussion is for general information purposes only and does not address all aspects of U.S. federal income taxation that may be relevant to a U.S. Holder’s particular circumstances, including the impact of the Medicare contribution tax on net investment income and the alternative minimum tax. In addition, it does not address consequences relevant to U.S. Holders subject to special tax rules, including, without limitation:

If a partnership (including any entity or arrangement treated as a partnership for U.S. federal income tax purposes) holds shares of our common stock, the tax treatment of a partner in the partnership generally will depend upon the status of the partner, the activities of the partnership, and certain determinations made at the partner level. Partnerships holding our

common stock and the partners in such partnerships should consult their tax advisors regarding the tax consequences to them of the Reverse Stock Split.

THIS DISCUSSION IS FOR INFORMATION PURPOSES AND IS NOT TAX ADVICE. EACH HOLDER OF COMMON STOCK SHOULD CONSULT ITS TAX ADVISORS WITH RESPECT TO THE PARTICULAR TAX CONSEQUENCES OF THE REVERSE STOCK SPLIT TO SUCH HOLDER, AS WELL AS ANY TAX CONSEQUENCES OF THE REVERSE STOCK SPLIT ARISING UNDER OTHER U.S. FEDERAL TAX LAWS (INCLUDING ESTATE AND GIFT TAX LAWS), OR UNDER THE LAWS OF ANY STATE, LOCAL, OR NON-U.S. TAXING JURISDICTION.

This summary addresses only stockholders that are U.S. Holders. For purposes of this discussion, a “U.S. Holder” is any beneficial owner of our common stock that, for U.S. federal income tax purposes, is or is treated as any of the following:

The Reverse Stock Split should constitute a “recapitalization” for U.S. federal income tax purposes. As a result, U.S. Holders generally should not recognize gain or loss as a result of the Reverse Stock Split, except as described below with respect to cash received in lieu of fractional shares. A U.S. Holder’s aggregate tax basis in the shares of the common stock received pursuant to the Reverse Stock Split should equal the U.S. Holder’s aggregate tax basis in the shares of the common stock surrendered (excluding any portion of such basis that is allocated to any fractional share of our common stock), and such U.S. Holder’s holding period for the shares of the common stock received should include the holding period for the shares of the common stock surrendered.

Treasury regulations promulgated under the Code provide detailed rules for allocating the tax basis and holding period of shares of common stock surrendered pursuant to the Reverse Stock Split to shares of common stock received pursuant to the Reverse Stock Split. U.S. Holders holding shares of common stock that were acquired on different dates and at different prices should consult their tax advisors regarding the allocation of the tax basis and holding period of such shares.

A U.S. Holder that receives cash in lieu of a fractional share of common stock should be treated as first receiving such fractional share and then receiving cash in redemption of such fractional share. A U.S. Holder that receives cash in lieu of a fractional share in the Reverse Stock Split should recognize capital gain or loss equal to the difference between the amount of the cash received in lieu of the fractional share and the portion of the U.S. Holder’s adjusted tax basis allocable to the fractional share. Such capital gain or loss should be long-term capital gain or loss if the U.S. Holder’s holding period for the common stock surrendered exceeded one year at the Effective Time. The deductibility of capital losses is subject to limitations. U.S. Holders should consult their tax advisors regarding the tax effects to them of receiving cash in lieu of fractional shares based on their particular circumstances.

U.S. Holders (other than corporations and certain other exempt recipients) may be subject to information reporting with respect to any cash received in lieu of a fractional share of common stock in the Reverse Stock Split. U.S. Holders that are subject to information reporting and do not provide a correct taxpayer identification number and other required information (such as by submitting a properly completed IRS Form W‑9) may also be subject to backup withholding at the applicable rate. Any amount withheld under such rules is not an additional tax and may be refunded or credited against the U.S. Holder’s U.S. federal income tax liability, provided that the required information is properly furnished in a timely manner to the IRS. U.S. Holders should consult their tax advisors regarding their qualification for an exemption from backup withholding and the procedures for obtaining such an exemption.

VOTE REQUIRED

This Proposal requires the affirmative vote of the holders of a majority of the votes cast for and against. Abstentions and broker non-votes 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 the amendments to our Certificate of Incorporation to effect the Reverse Stock Split.

Introduction to Proposals 6 and 7

At our 2024 annual meeting of stockholders, our stockholders voted on a stockholder-sponsored proposal requesting that the Board take the steps necessary to eliminate each stockholder voting requirement in our Certificate of Incorporation and Bylaws that calls for a greater than simple majority vote and to replace it with a requirement for a majority of the votes cast for and against applicable proposals, or a simple majority in compliance with applicable laws (the “2024 Simple Majority Proposal”). The 2024 Simple Majority Proposal passed with the support of the holders of a majority of the votes cast affirmatively or negatively.

The Board and the Nominating and Corporate Governance Committee of the Board of Directors (the “Nominating and Corporate Governance Committee”) have carefully considered the advantages and disadvantages of maintaining the supermajority voting provisions in our Certificate of Incorporation and our Bylaws. While the higher voting requirements are intended to ensure that certain fundamental matters are supported by a broad consensus of the Company’s stockholders, our Board and our Nominating and Corporate Governance Committee recognize that there are different perspectives on this matter. After weighing these considerations, our Board and our Nominating and Corporate Governance Committee have determined that it is in the best interests of the Company and its stockholders to amend our Certificate of Incorporation to eliminate the supermajority voting requirements. As a result, the Nominating and Corporate Governance Committee recommended and the Board has unanimously approved, and recommends that our stockholders approve, the amendments to the Certificate of Incorporation described in Proposals 6 and 7.

The Company is submitting each of the amendments described in Proposals 6 and 7 to stockholders as separate and independent Proposals because the vote required to approve the amendments contained in Proposal 6 is different than the vote required to approve the amendments contained in Proposal 7. Neither of Proposals 6 nor 7 is conditioned on the approval of the other.

Each of the proposed amendments set forth in Proposals 6 and 7 that are approved by the Company’s stockholders at the Annual Meeting will be reflected in a related certificate of amendment to the Certificate of Incorporation and will become effective upon the filing of such certificate of amendment with the Secretary of State of the State of Delaware, which the Company intends to file as soon as reasonably practicable following the Annual Meeting. The Board also has the authority to abandon all proposed amendments to the Certificate of Incorporation, notwithstanding prior stockholder approval of such amendments.

If the stockholders approve Proposal 7, the Board intends to approve conforming amendments to the Bylaws to update the corresponding voting thresholds in the Bylaws.

Proposal 6

Approval of Amendments to our Certificate of Incorporation to Clarify Voting Requirements to Amend the Number of Shares of Authorized Common Stock and Preferred Stock

Our Certificate of Incorporation includes provisions providing that the affirmative vote of the holders of a majority of the stock of the Company entitled to vote may amend the number of authorized shares of common stock and the number of authorized shares of preferred stock (the number of shares of authorized common stock and authorized preferred stock together, the “Authorized Stock”), irrespective of the provisions of Section 242(b)(2) of the General Corporation Law of the State of Delaware (the “DGCL”).

Effective as of August 1, 2023, Section 242 of the DGCL was amended to add Section 242(d), which modified the voting standard for stockholders of a Delaware corporation to approve an amendment to the corporation’s certificate of incorporation to increase or decrease the corporation’s authorized shares, among other things. Prior to the amendment of Section 242, Delaware corporations were required to obtain the affirmative vote of a majority of the outstanding shares entitled to vote on such a proposal and, to the extent applicable, the affirmative vote of a majority of the outstanding shares of each class of stock entitled to vote on the proposal as a separate class. Pursuant to Section 242(d)(2) of the DGCL (“Section 242(d)(2)”), unless otherwise required by a corporation’s certificate of incorporation, an amendment to increase or decrease the authorized number of shares of a class of capital stock may be approved by the affirmative vote of a majority of the votes cast for and against by the stockholders entitled to vote on the proposal, voting as a single class, so long as (a) the applicable class of shares is listed on a national securities exchange immediately before the charter amendment becomes effective and (b) the corporation will meet exchange listing requirements concerning minimum number of stockholders immediately after the amendment becomes effective, among other potential requirements.

Because our Certificate of Incorporation currently provides that the affirmative vote of the holders of a majority of the stock of the Company entitled to vote may increase or decrease the number of Authorized Stock, irrespective of the provisions of Section 242(b)(2), there is currently uncertainty as to whether we may take advantage of the simple majority of the votes cast voting standard provided for by Section 242(d)(2) for amendments to increase the number of Authorized Stock. By removing from our Certificate of Incorporation the recitation of the voting standard found in Section 242(b)(2), this Proposal is intended to clarify that the voting standard found in Section 242(d)(2) would apply to any amendment to increase the number of Authorized Stock when the requirements of Section 242(d)(2) are satisfied. This Proposal is therefore responsive to the 2024 Simple Majority Proposal, which requested that a majority of the votes cast for and against standard be adopted when permitted by applicable law.

If this Proposal 6 is approved by stockholders, Article FOURTH section A. 2. of the Certificate of Incorporation and Article FOURTH section B. of the Certificate of Incorporation will be amended to remove the recitation of the voting standard found in Section 242(b)(2) and make ancillary changes. The general description of the proposed changes to the Certificate of Incorporation in this Proposal 6 is qualified in its entirety by reference to the full text of the proposed changes. A copy of the amendments contemplated by this Proposal 6 is attached hereto as Appendix C-1, and a copy of the amendments contemplated by this Proposal 6, marked to show changes against our current Certificate of Incorporation, is attached hereto as Appendix C-2.

If this Proposal 6 is not approved, no changes will be made to Article FOURTH of the Certificate of Incorporation.

VOTE REQUIRED

This Proposal requires the affirmative vote of the holders of a majority of the outstanding stock of the Company entitled to vote on the Proposal. Abstentions and broker non-votes 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” Proposal 6.

Proposal 7

Approval of Amendments to our Certificate of Incorporation to Eliminate Supermajority Voting Requirements

Our Certificate of Incorporation includes provisions requiring the affirmative vote of the holders of at least two-thirds of the voting power of the shares outstanding and entitled to vote thereon (or, in the case of the removal of directors, at an election of directors) for:

This Proposal 7 is intended to eliminate the foregoing supermajority voting requirements (the “Supermajority Elimination Amendment”).

If this Proposal 7 is approved by stockholders, Articles SIXTH, EIGHTH section 10, NINTH, TENTH and ELEVENTH of the Certificate of Incorporation will be amended such that each of the applicable voting standards described above will be amended to require the affirmative vote of the holders of a majority of the voting power of the shares outstanding and entitled to vote thereon, which is consistent with the voting standard required by Section 242(b) for amendments to a corporation’s certificate of incorporation. In addition, the voting standard to remove our directors for cause in Article EIGHTH Section 7 would be amended to require the affirmative vote of the holders of a majority in voting power of the shares entitled to vote at an election of directors, which is consistent with the voting standard required by Section 141(k) of the DGCL for removal of directors. The general description of the proposed changes to the Certificate of Incorporation in this Proposal 7 is qualified in its entirety by reference to the full text of the proposed changes. A copy of the Supermajority Elimination Amendment contemplated by this Proposal 7 is attached hereto as Appendix D-1, and a copy of the amendments contemplated by Proposal 7, marked to show changes against our current Certificate of Incorporation, is attached hereto as Appendix D-2.

If this Proposal 7 is not approved, no changes will be made to Articles SIXTH, EIGHTH section 7, EIGHTH section 10, NINTH, TENTH or ELEVENTH of the Certificate of Incorporation.

VOTE REQUIRED

This Proposal requires the affirmative vote of the holders of at least two-thirds in voting power of the outstanding shares of capital stock of the Company entitled to vote on the Proposal. Abstentions and broker non-votes will have the same effect as a vote against this Proposal.

RECOMMENDATION OF THE BOARD OF DIRECTORS

The Board of Directors unanimously recommends a vote “FOR” the Supermajority Elimination Amendment.

Proposal 8
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 Proposals 5, 6, or 7.

VOTE REQUIRED

This Proposal requires the affirmative vote of the holders of a majority of the votes cast affirmatively or negatively. Abstentions and broker non-votes 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 Proposals 5, 6, or 7.

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, 2024 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, 2024.

Richard N. Kender (Chair)

Claire M. Fraser, Ph.D.

Willard H. Dere, M.D.

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 2024 and 2023 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.

Audit-Related Fees

Audit-related fees in 2024 consist of fees in connection with our sale of the VOWST Business. There were no such fees incurred in 2023.

Tax Fees

There were no such fees incurred in 2024 or 2023.

All Other Fees

All other fees in 2024 and 2023 represent non-audit fees in connection with access to the PricewaterhouseCoopers LLP on-line accounting research and disclosures database and other advisory and consulting services.

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.

Executive Officers

The following table identifies our current executive officers:

Corporate Governance

GENERAL

Our Board of Directors has adopted Corporate Governance Guidelines, an Insider Trading Compliance Policy, a Code of Business Conduct and Ethics, a Clawback Policy (as defined below) and charters for each of 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, our 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 101 Cambridgepark Drive, Cambridge, MA 02140.

BOARD COMPOSITION

Our Board of Directors currently consists of nine members: Eric D. Shaff, Dennis A. Ausiello, M.D., Stephen A. Berenson, Paul R. Biondi, Willard H. Dere, M.D., Claire M. Fraser, Ph.D., Richard N. Kender, Kurt C. Graves, and Hans-Juergen Woerle, M.D., Ph.D. As set forth in our 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 Certificate of Incorporation and 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. In Proposal 7, we are requesting stockholders to vote on the elimination of this supermajority voting requirement. Based on voluntary self-identification by our directors, our Board consists of one female and eight male directors. Seven of our directors identify as white, two directors identify as Asian, and one director identifies as belonging to one or more races or ethnicities.

In addition, pursuant to Section 7.1 of the Securities Purchase Agreement (the “Securities Purchase Agreement”), dated as of September 30, 2024, by and between the Company and Société des Produits Nestlé S.A. (“SPN”), for so long as SPN (together with its Affiliates, as defined in the Securities Purchase Agreement) beneficially owns at least ten percent of the Company’s outstanding shares of common stock, SPN has the right to designate one director for election to the Board, and SPN has designated Dr. Woerle.

DIRECTOR INDEPENDENCE

All of our current 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 Dr. Woerle, his relationship to, and our transactions with, Nestlé 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.

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; 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.

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., 101 Cambridgepark Drive, Cambridge, MA 02140. In the event there is a vacancy, and assuming that appropriate biographical and background material has been provided on a timely basis, the Nominating and Corporate Governance 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., 101 Cambridgepark Drive, Cambridge, MA 02140.

BOARD LEADERSHIP STRUCTURE AND ROLE IN RISK OVERSIGHT

Our 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 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 receives quarterly reports from our Chief Information Officer, or CIO, on our cybersecurity risks, and our CIO updates the Audit Committee, as necessary, regarding any material cybersecurity incidents, as well as any incidents with lesser impact potential. 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 seeks to include students from all backgrounds, 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 by planning activities through our Seres Community Ambassadors program and offering eight hours of paid volunteer time annually for employees to support charitable organizations.

We also believe that our long-term success and ability to deliver innovative, safe, and effective medicines to patients requires an inclusive workforce, which we advance through legally compliant methods. We strive to identify ways to attract, develop, and retain talent from all backgrounds and help foster a stronger sense of belonging for all employees. 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, and tuition reimbursement. Our management reports to our board of directors on human capital management topics, including as relevant: corporate culture, employee development and retention, and compensation and benefits.

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 will present them to the Nominating and Corporate Governance Committee for review and discussion at the first Nominating and Corporate Governance Committee in 2025.

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.

INSIDER TRADING COMPLIANCE POLICY

Our Board of Directors has adopted an Insider Trading Compliance Policy governing the purchase, sale and other dispositions of our securities that applies to all Company personnel, including directors, officers, employees, and other covered persons. We believe our insider trading policy is reasonably designed to promote compliance with insider trading laws, rules and regulations, and listing standards applicable to the Company. A copy of our Insider Trading Compliance Policy is filed with our Annual Report on Form 10-K for the year ended December 31, 2024.

ANTI-HEDGING AND ANTI-PLEDGING POLICY

Our Insider Trading Compliance Policy prohibits our directors, officers and employees and any entities they control from purchasing financial instruments such as prepaid variable forward contracts, equity swaps, collars, and exchange funds, 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.

CLAWBACK POLICY

Our Board of Directors has adopted a Policy for Recovery of Erroneously Awarded Compensation (the "Clawback Policy"), in accordance with the Nasdaq listing standards and Rule 10D-1 under the Exchange Act, which applies to our current and former executive officers. Under the Clawback Policy, we are required to recoup the amount of any erroneously awarded compensation (as defined in the Clawback Policy) on a pre-tax basis within a specified lookback period in the event of any accounting Restatement (as defined in the Clawback Policy), subject to limited impracticability exceptions. Covered restatements include both a restatement to correct an error that is material to previously issued financial statements or that would result in a material misstatement if the error were corrected in the current period or left uncorrected in the current period. The amount required to be recovered is the excess of the amount of incentive-based compensation received over the amount that otherwise would have been received had it been determined based on the restated financial measure. The Clawback Policy is overseen and administered by the Compensation and Talent Committee. The full text of the Clawback Policy was included as Exhibit 97.1 to our Annual Report on Form 10-K for the fiscal year ended December 31, 2023, filed with the SEC on March 5, 2024.

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, 2024. During the fiscal year ended December 31, 2024, 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 2024.

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 and is available on our website at www.serestherapeutics.com. All of the members of each of the Board’s four 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., and Claire M. Fraser, Ph.D., 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.

AUDIT COMMITTEE

Our Audit Committee’s responsibilities include:

The members of the Audit Committee are Dr. Dere, Dr. Fraser, and Mr. Kender. Mr. Kender serves as the Chairperson of the committee. 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. Dere, Dr. Fraser, and Mr. Kender is an “audit committee financial expert” as defined by Item 407(d)(5)(ii) of Regulation S-K.

The Audit Committee met six times in 2024.

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 various principal duties, including:

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. 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. Mr. Graves serves as the Chairperson of the Compensation and Talent Committee.

The Compensation and Talent Committee met six times in 2024.

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 Mr. Berenson. Mr. Berenson serves as the Chairperson of the Nominating and Corporate Governance Committee.

The Nominating and Corporate Governance Committee met one time in 2024.

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, Fraser and Woerle. Dr. Ausiello serves as the Chairperson of the Science and Clinical Development Committee.

The Science and Clinical Development Committee met four times in 2024.

Executive Compensation

As a smaller reporting company, we are eligible to follow the reduced disclosure obligations regarding executive compensation that apply to smaller reporting companies. However, in this section, we have voluntarily elected to include executive compensation disclosure under certain sections of Item 402 of Regulation S-K that are not required of a smaller reporting company.

GENERAL

In the discussion 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 2024, including the elements of our compensation program for NEOs, material compensation decisions made under that program for fiscal 2024 and the material factors considered in making those decisions. For the year ended December 31, 2024, our NEOs, which consisted of our principal executive officer and our two most other highly compensated executive officers for fiscal year 2024, were:

*On February 22, 2025, Dr. von Moltke notified us of her resignation as Executive Vice President and Chief Medical Officer, effective as of March 14, 2025.

Stockholder Advisory Vote on Executive Compensation and Stockholder Engagement

At our 2024 Annual Meeting of Stockholders, approximately 65% of the votes cast approved, on an advisory basis, the compensation of our NEOs for fiscal year 2023. Following our 2024 Annual Meeting of Stockholders, we contacted stockholders collectively holding approximately 43% of our shares outstanding for feedback on certain elements of our compensation program, and we met with stockholders collectively holding approximately 27% of our shares outstanding. At the time of outreach, a significant portion of our shares outstanding were held by retail holders, which prevented us from replicating the outreach efforts typically seen by larger reporting companies.

Our efforts supplemented ongoing communications between our management and stockholders regarding our financial performance, business strategy and results and expanded upon the outreach to stockholders prior to and in connection with our 2025 Annual Meeting. Our objectives were to gain a better understanding of stockholders' views on our executive compensation practices and policies and related governance topics. Our stockholders expressed that they were generally comfortable with the fundamental aspects of our executive compensation practices and programs. However, in light of the stockholder advisory vote, and in conjunction with a number of other factors in making decisions about our executive compensation program, including input from the Compensation and Talent Committee's independent outside consultant, our Compensation and Talent Committee refined executive compensation in 2024.

For example, in 2024, we introduced performance-based options to our executive compensation program. Consistent with a pay for performance philosophy, these options vest only upon the attainment of certain share price thresholds and, as such, align executive interests with those of our stockholders by further linking our executive compensation opportunities to the creation of stockholder value. Specifically, the options vest as to the first 50% of shares subject to the options upon achievement of a 30-day trailing average public market closing price per share of common stock greater than or equal to $3.00, which at the time of grant, represented a ~200% increase in share price. The options vest as to the remaining 50% of shares subject to the options upon achievement of a 30-day trailing average public market closing price per share of common stock greater than or equal to $5.00, which at the time of grant, represented a ~400% increase in share price. The options were subject to the further limit that no vesting could occur prior to first anniversary of the date of grant, even if the share price performance goals were earlier attained. As of March 3, 2025, all such performance options remained unvested.

In addition, in keeping with our pay for performance compensation philosophy and to recognize our share price underperformance for the year, the Compensation and Talent Committee elected to award the corporate objective portion of our NEO's 2024 bonus based on 100% despite 112% corporate achievement.

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 2024, consisted of grants of stock options and restricted stock units.

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. Alpine Rewards, LLC, or Alpine, has advised our Compensation and Talent Committee since October 2022. When making executive compensation decisions in 2024, our Compensation and Talent Committee considered advice and data provided by Alpine and met with Alpine to discuss compensation of our executive officers, including our President and Chief Executive Officer. Alpine reported directly to the Compensation and Talent Committee; however, our President and Chief Executive Officer consulted with Alpine with respect to his assessments of the compensation of executive officers other than himself.

Alpine provided the Compensation and Talent Committee with peer group and market information that the Compensation and Talent Committee used when determining whether our executive compensation is competitive, commensurate with the executive officers’ responsibilities and consistent with market trends in executive compensation practices for comparable companies. 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 Alpine and does not believe Alpine's work in 2024 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.

2024 Peer Group

In connection with the Compensation and Talent Committee’s review of our executive compensation programs in late 2023, Alpine provided market data and analysis relative to a peer group selected by the Compensation and Talent Committee. 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 late-stage pre-commercial and recently commercial companies (as the stage was previously only companies that recently submitted a NDA or BLA); the market capitalization range was increased (as the range was previously $150 million to $1.5 billion); the headcount range was decreased (as the range was previously 150 to 1,500 employees); and revenue was removed (as the range was previously under $500 million).

Given these changes in peer company profiles, Alpine recommended and, in August 2023, the Compensation and Talent Committee approved, the removal of three companies and the addition of five new peer companies that better aligned with the Company’s profile to form the following compensation peer group:

The Compensation and Talent Committee believes the constituent companies in the peer group are similar to us based on development stage, industry, executive role considerations and market capitalization and are representative of our competitors for talent and capital. 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.

Elements of Our Executive Compensation Program

Historically, and for fiscal 2024, 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. After making no adjustments to base salaries for 2024, we elected to increase the 2025 base salary of Mr. Shaff by 2% and our other NEOs by 3% to remain aligned with the competitive range while considering individual performance, experience, and level of contribution. The following table shows the annual base salaries of our NEOs for 2023, 2024 and 2025. 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’ 2024 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 2024 corporate objectives was weighted 80% and the achievement of individual objectives was weighted at 20%. Mr. Shaff’s 2024 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 2024 corporate objectives. Individual objectives are analyzed based on the business judgement 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 2025, the Compensation and Talent Committee determined our 2024 corporate objectives were achieved at the 112% level. However, in consultation with management and based on guidance from Alpine, the Compensation and Talent Committee elected to award the corporate objective portion of our NEO's 2024 bonus based on 100% corporate achievement. These adjustments were made primarily to recognize our share price performance for the year and in keeping with our pay for performance compensation philosophy. The individual performance component of the 2024 NEO bonuses was achieved at 100% for each of Dr. von Moltke and Mr. DesRosier. The actual amounts paid to our NEOs under our 2024 annual cash bonus program are set forth in the 2024 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’ 2025 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 2024.

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, as determined under the applicable equity incentive plan, 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.

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. Our restricted stock units typically vest as to 25% of the restricted stock units on the first 15th day of the calendar month that immediately follows the first anniversary of the grant date, and as to 6.25% of the restricted stock units upon completion of each three consecutive months of service 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. In 2024, we also granted performance-based options that vest if the 30-day trailing average public market closing price of our Common Stock achieves certain price thresholds. 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 and the retention value that NEOs have from past equity awards.

In February 2024, we granted time-based stock options, performance-based stock options and time-based restricted stock units to our NEOs in the following amounts and with the vesting schedule indicated in the table below.

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 31, 2024, 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 2024, 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 2024.

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.

Executive Compensation Tables

2024 Summary Compensation Table

Grants of Plan-Based Awards in Fiscal 2024

The following table provides supplemental information relating to grants of plan-based awards made during fiscal 2024 to help explain information provided above in our Summary Compensation Table. All awards are granted under the 2015 Plan.