SEC Form PRE 14A filed by Sutro Biopharma Inc.

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

SCHEDULE 14A

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:

☒ Preliminary Proxy Statement

☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2))

☐ Definitive Proxy Statement

☐ Definitive Additional Materials

☐ Soliciting Material Pursuant to §240.14a-12

SUTRO BIOPHARMA, INC.

(Name of Registrant as Specified In Its Charter)

N/A

(Name of Person(s) Filing Proxy Statement, if other than the Registrant)

Payment of Filing Fee (Check the appropriate box):

☒ No fee required.

☐ Fee paid previously with preliminary materials.

☐ Fee computed on table in exhibit required by Item 25(b) per Exchange Act Rules 14a-6(i)(1) and 0-11.

SUTRO BIOPHARMA, INC.

111 Oyster Point Boulevard

South San Francisco, California, 94080

NOTICE OF ANNUAL MEETING OF STOCKHOLDERS

To Be Held June 6, 2025

To Our Stockholders:

NOTICE IS HEREBY GIVEN that the 2025 Annual Meeting of Stockholders of Sutro Biopharma, Inc. will be held via a virtual meeting. You will be able to participate in the 2025 Annual Meeting and vote during the 2025 Annual Meeting via live webcast by visiting www.virtualshareholdermeeting.com/STRO2025 on Friday, June 6, 2025 at 3:00 PM Pacific Time. We believe that a virtual stockholder meeting provides greater access to those who may want to attend, and therefore we have chosen this over an in-person meeting. It is important that you retain a copy of the control number found on the proxy card or voting instruction form, or included in the e-mail to you if you received the proxy materials by e-mail, as such number will be required in order for stockholders to gain access to the virtual meeting.

We are holding the meeting for the following purposes, which are more fully described in the accompanying proxy statement:

In addition, stockholders may be asked to consider and vote upon such other business as may properly come before the meeting or any adjournment or postponement thereof.

Only stockholders of record at the close of business on April 10, 2025 are entitled to receive notice of, and to vote at, the meeting and any adjournments thereof. This Notice of Internet Availability of Proxy Materials (“Notice of Internet Availability”) and the accompanying proxy statement are being mailed out to stockholders as of the record date beginning on or about April , 2025.

For ten days prior to the meeting, a complete list of the stockholders entitled to vote at the meeting will be available upon request by any stockholder for any purpose relating to the meeting. Stockholders can request the list of stockholders through our investor relations website at https://ir.sutrobio.com/contact-ir .

Your vote as a Sutro Biopharma, Inc. stockholder is very important. Each share of common stock that you own represents one vote.

For questions regarding your stock ownership, you may contact our Investor Relations group at [email protected] or, if you are a registered holder, our transfer agent, Equiniti Trust Company, LLC by email through their website at https://www.equiniti.com/us or by phone at (800) 937-5449. Whether or not you expect to attend the meeting, we encourage you to read the proxy statement and vote through the internet or by telephone, or to request, sign and return your proxy card as soon as possible, so that your shares may be represented at the meeting. For specific instructions on how to vote your shares, please refer to the section entitled “General Proxy Information” in the proxy statement.

South San Francisco, California

April , 2025

Important Notice Regarding the Availability of Proxy Materials for the virtual Annual Meeting of Stockholders to be held on June 6, 2025: the Proxy Statement and our 2024 Annual Report on Form 10-K are available at http://ir.sutrobio.com. You will need the control number included on your proxy card or voting instruction form, or included in the e-mail to you if you received the proxy materials by e-mail, as such number will be required in order for stockholders to gain access to the virtual meeting.

SUTRO BIOPHARMA, INC.

PROXY STATEMENT FOR 2025 ANNUAL MEETING OF STOCKHOLDERS

TABLE OF CONTENTS

SUTRO BIOPHARMA, INC.

111 Oyster Point Boulevard

South San Francisco, California, 94080

PROXY STATEMENT FOR THE 2025 ANNUAL MEETING OF STOCKHOLDERS

April , 2025

INFORMATION ABOUT SOLICITATION AND VOTING

The accompanying proxy is solicited on behalf of the Board of Directors of Sutro Biopharma, Inc. (Sutro Biopharma or the Company) for use at Sutro Biopharma’s 2025 Annual Meeting of Stockholders (Annual Meeting) to be held via a virtual meeting. You will be able to participate in the Annual Meeting and vote during the Annual Meeting via live webcast by visiting www.virtualshareholdermeeting.com/STRO2025 on Friday, June 6, 2025 at 3:00 PM Pacific Time and any adjournment or postponement thereof. We believe that a virtual stockholder meeting provides greater access to those who may want to attend, and therefore we have chosen this format over an in-person meeting. This approach also lowers costs and aligns with our broader sustainability goals. You will need the control number included on your proxy card or voting instruction form, or included in the e-mail to you if you received the proxy materials by e-mail, as such number will be required in order for stockholders to gain access to the virtual meeting. We are making this proxy statement, the accompanying form of proxy and our Annual Report on Form 10‑K for the year ended December 31, 2024 first available to stockholders on or about April , 2025. An electronic copy of this proxy statement and Annual Report on Form 10‑K are available at http://ir.sutrobio.com.

INTERNET AVAILABILITY OF PROXY MATERIALS

Under rules adopted by the Securities and Exchange Commission (the “SEC”), we are furnishing proxy materials to our stockholders primarily via the Internet, instead of mailing printed copies to each stockholder. On or about April , 2025, we expect to send to our stockholders a Notice of Internet Availability containing instructions on how to access our proxy materials, including our proxy statement and our Annual Report on Form 10-K. The Notice of Internet Availability also provides instructions on how to vote and includes instructions on how to receive paper copies of the proxy materials by mail, or an electronic copy of the proxy materials by email.

This process is designed to reduce our environmental impact and lower the costs of printing and distributing our proxy materials while providing our stockholders timely access to this important information. If you would prefer to receive printed proxy materials, please follow the instructions included in the Notice of Internet Availability.

GENERAL INFORMATION ABOUT THE MEETING

Purpose of the Meeting

At the meeting, stockholders will act upon the proposals described in this proxy statement. In addition, we will consider any other matters that are properly presented for a vote at the meeting. We are not aware of any other matters to be submitted for consideration at the meeting. If any other matters are properly presented for a vote at the meeting, the persons named in the proxy, who are officers of the company, have the authority in their discretion to vote the shares represented by the proxy.

Record Date; Quorum

Only holders of record of common stock at the close of business on April 10, 2025, the record date, will be entitled to vote at the meeting. At the close of business on April 10, 2025, 84,363,322 shares of common stock were outstanding and entitled to vote.

The holders of a majority of the voting power of the shares of stock entitled to vote at the meeting as of the record date must be present or represented by proxy at the meeting in order to hold the meeting and conduct business. This presence is called a quorum. Your shares are counted as present at the meeting if you are present and vote online at the virtual meeting or if you have properly submitted a proxy.

GENERAL PROXY INFORMATION

Voting Rights; Required Vote

Each holder of shares of common stock is entitled to one vote for each share of common stock held as of the close of business on April 10, 2025, the record date. You may vote all shares owned by you at such date, including (1) shares held directly in your name as the stockholder of record and (2) shares held for you as the beneficial owner in street name through a broker, bank, trustee or other nominee. Dissenters’ rights are not applicable to any of the matters being voted on.

Stockholder of Record: Shares Registered in Your Name. If on April 10, 2025, your shares were registered directly in your name with our transfer agent, Equiniti Trust Company LLC, then you are considered the stockholder of record with respect to those shares. As a stockholder of record, you may vote at the meeting, or vote in advance through the internet or by telephone, or if you request to receive paper proxy materials by mail, by filling out and returning the proxy card.

Beneficial Owner: Shares Registered in the Name of a Broker or Nominee. If on April 10, 2025, your shares were held in an account with a brokerage firm, bank or other nominee, then you are the beneficial owner of the shares held in street name. As a beneficial owner, you have the right to direct your broker on how to vote the shares held in your account, and your broker has enclosed or provided voting instructions for you to use in directing it on how to vote your shares. Because the brokerage firm, bank or other nominee that holds your shares is the stockholder of record, if you wish to attend the meeting and vote your shares, you must obtain a valid proxy from the firm that holds your shares giving you the right to vote the shares at the meeting.

Each director will be elected by a plurality of the votes cast by the holders of the shares present in person or represented by proxy at the meeting and entitled to vote on the election of directors. This means that the three individuals nominated for election to the Board of Directors at the meeting receiving the highest number of “FOR” votes will be elected. You may either vote “FOR” one, two or all three of the nominees or “WITHHOLD” your vote with respect to one, two or all three of the nominees. You may not cumulate votes in the election of directors. Approval of the ratification of the appointment of our independent registered public accounting firm requires the affirmative vote of the holders of a majority of the voting power of the shares of stock entitled to vote on such matter that are present in person or represented by proxy at the meeting and are voted for or against the matter. Approval, on a non-binding advisory basis, of the compensation of our named executive officers requires the affirmative vote of the holders of a majority of the voting power of the shares of stock entitled to vote on such matter that are present in person or represented by proxy at the meeting and are voted for or against the matter. Approval of the amendment to our Restated Certificate of Incorporation (the “Certificate of Incorporation”) to effect a reverse stock split will be obtained if the holders of a majority of the voting power of the shares of stock entitled to vote on such matter that are present in person or represented by proxy at the meeting and are voted for or against the matter.

A proxy submitted by a stockholder may indicate that the shares represented by the proxy are not being voted (stockholder withholding) with respect to a particular matter or the stockholder may abstain from voting on the matter (abstention). In addition, a broker may not be permitted to vote on shares held in street name on a particular matter in the absence of instructions from the beneficial owner of the stock (broker non-vote). The shares subject to a proxy which are not being voted on a particular matter because of either stockholder withholding or broker non-votes will count for purposes of determining the presence of a quorum, but are not treated as votes cast and, therefore, will have no effect on the outcome of any of the proposals. Additionally, abstentions will count for purposes of determining the presence of a quorum, but are voted neither “for” nor “against” a matter, and, therefore, will have no effect on the outcome of any of the proposals.

Recommendations of the Board of Directors on Each of the Proposals Scheduled to be Voted on at the Meeting

The Board of Directors recommends that you vote FOR the election of each of the Class I directors named in this proxy statement (Proposal 1); FOR the ratification of the appointment of Ernst & Young LLP as our independent registered public accounting firm for the fiscal year ending December 31, 2025 (Proposal 2); FOR the approval, on a non-binding advisory basis, of the compensation of our named executive officers, as disclosed in this Proxy Statement (Proposal 3); and FOR the amendment to our Certificate of Incorporation to effect a reverse stock split (Proposal 4).

None of the directors or executive officers has any substantial interest in any matter to be acted upon, other than elections to office with respect to the directors nominated in Proposal 1.

Voting Instructions; Voting of Proxies

If you are a stockholder of record, you may:

Votes submitted through the internet or by telephone must be received by 11:59 p.m., Eastern Time, on June 5, 2025. Submitting your proxy, whether by telephone, through the internet or by mail if you requested or received a paper proxy card, will not affect your right to vote online should you decide to attend the virtual meeting. If you are not the stockholder of record, please refer to the voting instructions provided by your nominee to direct how to vote your shares. For Proposal 1, you may either vote “FOR” all of the nominees to the Board of Directors, or you may withhold your vote from any nominee you specify. For Proposal 2, you may vote “FOR” or “AGAINST” or “ABSTAIN” from voting. For Proposal 3, you may vote “FOR” or “AGAINST” or “ABSTAIN” from voting. For Proposal 4, you may vote “FOR” or “AGAINST” or “ABSTAIN” from voting. Your vote is important. Whether or not you plan to attend the meeting, we urge you to vote by proxy to ensure that your vote is counted.

All proxies will be voted in accordance with the instructions specified on the proxy card. If you sign a physical proxy card and return it without instructions as to how your shares should be voted on a particular proposal at the meeting, your shares will be voted in accordance with the recommendations of our Board of Directors stated above.

If your shares are held in an account with a brokerage firm, bank or other nominee, then you are deemed to be the beneficial owner of your shares and the broker that actually holds the shares for you is the record holder and is required to vote the shares it holds on your behalf according to your instructions. The proxy materials, as well as voting and revocation instructions, should have been forwarded to you by the bank, broker or other nominee that holds your shares. In order to vote your shares, you will need to follow the instructions that your bank, broker or other nominee provides you. The voting deadlines and availability of telephone and Internet voting for beneficial owners of shares held in street name will depend on the voting processes of the bank, broker or other nominee that holds your shares. Therefore, we urge you to carefully review and follow the voting instruction card and any other materials that you receive from that organization.

If you received a Notice of Internet Availability, please follow the instructions included on the notice on how to access and vote your proxy card. If you do not vote and you hold your shares in street name, and your broker does not have discretionary power to vote your shares, your shares may constitute “broker non-votes” (as described above) and will not be counted in determining the number of shares necessary for approval of the proposals. However, shares that constitute broker non-votes will be counted for the purpose of establishing a quorum for the meeting.

If you receive more than one proxy card or Notice of Internet Availability, your shares are registered in more than one name or are registered in different accounts. To make certain all of your shares are voted, please follow the instructions included on the Notice of Internet Availability on how to access and vote each proxy card. If you requested or received paper proxy materials by mail, please complete, sign, date and return each proxy card to ensure that all of your shares are voted.

Expenses of Soliciting Proxies

We will pay the expenses associated with soliciting proxies. Following the original distribution and mailing of the solicitation materials, we or our agents may solicit proxies by mail, email, telephone, facsimile, by other similar means, or in person. Our directors, officers and other employees, without additional compensation, may solicit proxies personally or in writing, by telephone, email or otherwise. Following the original distribution and mailing of the solicitation materials, we will request brokers, custodians, nominees and other record holders to forward copies of those materials to persons for whom they hold shares and to request authority for the exercise of proxies. In such cases, we, upon the request of the record holders, will reimburse such holders for their reasonable expenses. If you choose to access the proxy materials and/or vote through the internet, you are responsible for any internet access charges you may incur.

Revocability of Proxies

A stockholder of record who has given a proxy may revoke it at any time before the closing of the polls by the inspector of elections at the meeting by:

Please note, however, that if your shares are held of record by a brokerage firm, bank or other nominee, and you wish to revoke a proxy, you must contact that firm to revoke or change any prior voting instructions.

Electronic Access to the Proxy Materials

The Notice of Internet Availability will provide you with instructions regarding how to:

Choosing to receive your future proxy materials by email will reduce the impact of our annual meetings of stockholders on the environment and lower the costs of printing and distributing our proxy materials. If you choose to receive future proxy materials by email, you will receive an email next year with instructions containing a link to those materials and a link to the proxy voting site. Your election to receive proxy materials by email will remain in effect until you terminate it.

Voting Results

Voting results will be tabulated and certified by the inspector of elections appointed for the meeting. The final results will be tallied by the inspector of elections and filed with the SEC in a Current Report on Form 8-K within four business days of the meeting.

CORPORATE GOVERNANCE STANDARDS AND DIRECTOR INDEPENDENCE

We are committed to good corporate governance practices. These practices provide an important framework within which our Board of Directors and management pursue our strategic objectives for the benefit of our stockholders.

Corporate Governance Guidelines

Our Board of Directors has adopted Corporate Governance Guidelines that set forth expectations for directors, director independence standards, Board Committee structure and functions, and other policies for the governance of the company. Our Corporate Governance Guidelines are available without charge on the investor relations section of our website at https://ir.sutrobio.com/corporate-governance/governance-overview.

Board Composition and Leadership Structure

Our Nominating and Governance Committee periodically considers the leadership structure of our Board of Directors and makes such recommendations to our Board of Directors as our Nominating and Governance Committee deems appropriate. The positions of Chief Executive Officer and Chair of our Board of Directors are currently held by two different individuals (Jane Chung and Connie Matsui, respectively). This structure allows our Chief Executive Officer to focus on our day-to-day business while our Chair leads our Board of Directors in its fundamental role of providing advice to, and independent oversight of, management. Ms. Chung’s significant managerial experience working with and serving in various executive positions in life sciences companies makes her well-suited for this day-to-day operational role, while Ms. Matsui’s extensive experience advising life sciences companies with respect to corporate strategy, product development, sales and marketing and operations allows her to perform an oversight function separate from management. Our Board of Directors believes such separation is appropriate, as it enhances the accountability of the Chief Executive Officer to the Board of Directors and strengthens the independence of the Board of Directors from management. Any changes to the leadership structure of our Board of Directors, if made, will be promptly disclosed on the investor relations section of our website and in our proxy materials. Our Board of Directors, in its sole discretion, may seek input from our stockholders on the leadership structure of the Board of Directors.

Board’s Role in Risk Oversight

Our Board of Directors believes that open communication between management and the Board of Directors is essential for effective risk management and oversight. Our Board of Directors meets with our Chief Executive Officer and other members of the senior management team at regular quarterly Board of Director meetings, and at ad hoc meetings when deemed appropriate, where, among other topics, they discuss strategy and risks in the context of reports from the management team and evaluate the risks inherent in significant transactions. While our Board of Directors is ultimately responsible for risk oversight, our Board Committees assist the Board of Directors in fulfilling its oversight responsibilities in certain areas of risk. The Audit Committee assists our Board of Directors in fulfilling its oversight responsibilities with respect to risk management in the areas of internal controls over financial reporting, disclosure controls and procedures, and information security. The Compensation Committee assists our Board of Directors in assessing risks created by the incentives inherent in our compensation policies. The Nominating and Governance Committee assists our Board of Directors in fulfilling its oversight responsibilities with respect to the management of corporate, legal and regulatory risk and environmental, social and governance, or ESG, concerns. The Science and Technology Committee assists our Board of Directors in fulfilling its oversight responsibilities with respect to our research and development and platform programs.

Cybersecurity Risk Oversight

Our Board of Directors recognizes the critical importance of maintaining the trust and confidence of our patients, business partners and employees. Our Board of Directors is actively involved in oversight of our risk management program, and cybersecurity represents an important component of our overall approach to enterprise risk management (“ERM”). Through our ERM program, risks are identified, assessed and managed at the organization level, mission and business process level, and information system level. Our cybersecurity program, policies and procedures are fully integrated into our ERM program and are maintained in accordance with industry good standards. Our Board of Directors’ oversight of cybersecurity risk management is supported by our Audit Committee, which regularly interacts with our executive leadership, including our Chief Executive Officer, Chief Financial Officer and our General Counsel and other key officers.

We have implemented a comprehensive, cross-functional approach to identifying, preventing and mitigating cybersecurity threats and incidents, while also implementing controls and procedures that provide for the prompt escalation of certain cybersecurity incidents so that decisions regarding the public disclosure and reporting of such incidents can be made by management in a timely manner. We also maintain a comprehensive, risk-based approach to identifying and overseeing cybersecurity risks presented by third parties,

including vendors, service providers and other external users of our systems, as well as the systems of third parties that could adversely impact our business in the event of a cybersecurity incident affecting those third-party systems. Further information relating to cybersecurity and information security is contained in the section titled “Cybersecurity” in our Annual Report on Form 10-K for the year ended December 31, 2024.

Director Independence

Our common stock is listed on the Nasdaq Global Market. Under the rules of the Nasdaq Stock Market, independent directors must constitute a majority of a listed company’s Board of Directors. In addition, the rules of the Nasdaq Stock Market require that, subject to specified exceptions, each member of a listed company’s Audit, Compensation and Nominating and Governance Committees must be an “independent director”. Under the rules of the Nasdaq Stock Market, a director will only qualify as an “independent director” if, in the opinion of that company’s Board of Directors, that person does not have a relationship that would interfere with the exercise of independent judgment in carrying out the responsibilities of a director. Additionally, Compensation Committee members must not have a relationship with the listed company that is material to the director’s ability to be independent from management in connection with the duties of a Compensation Committee member.

Audit Committee members must also satisfy the independence criteria set forth in Rule 10A-3 under the Securities Exchange Act of 1934, as amended (Exchange Act). In order to be considered independent for purposes of Rule 10A-3, a member of an Audit Committee of a listed company may not, other than in his or her capacity as a member of the Audit Committee, the Board of Directors or any other Board Committee: (i) accept, directly or indirectly, any consulting, advisory or other compensatory fee from the listed company or any of its subsidiaries or (ii) be an affiliated person of the listed company or any of its subsidiaries.

Our Board of Directors has undertaken a review of the independence of each director and considered whether each director has a material relationship with us that could compromise his or her ability to exercise independent judgment in carrying out his or her responsibilities. As a result of this review, our Board of Directors determined that Connie Matsui, Michael Dybbs, John Freund, Sukhi Jagpal, Heidi Hunter, Joseph Lobacki, James Panek, Daniel Petree, and Jon Wigginton, representing nine of our ten incumbent directors, are “independent directors” as defined under the applicable rules and regulations of the SEC and the listing requirements and rules of the Nasdaq Stock Market. In making these determinations, our Board of Directors reviewed and discussed information provided by the directors and us with regard to each directors’ business and personal activities and relationships as they may relate to us and our management, including the beneficial ownership of our capital stock by each non-employee director and any affiliates.

Board of Directors and Committee Self-Evaluations

Our Board of Directors is committed to a robust self-evaluation process designed for continuous improvement. To achieve this, our Board of Directors conducts an annual self-evaluation for itself and its committees. As part of this process, each member of the Board of Directors completes a survey to provide feedback on the processes, structure, composition and effectiveness of the Board of the Directors. The survey is a detailed written questionnaire designed to help the Board of Directors assess the performance of the Board of Directors and its committees, their own individual performance and the individual performances of fellow directors. The feedback received is shared first with the Nominating and Governance Committee, and then made available to the individual directors and the full Board of Directors.

Committees of Our Board of Directors

Our Board of Directors has established an Audit Committee, a Compensation Committee, a Nominating and Governance Committee and a Science and Technology Committee, each of which has the composition and responsibilities described below. Members serve on these Committees until their resignation or until otherwise determined by our Board of Directors. Each of these Committees has a written charter, copies of which are available without charge on the investor relations section of our website at https://ir.sutrobio.com/corporate-governance/governance-overview under the heading “Governance.” The Board of Directors also establishes ad hoc committees to manage particular strategic priorities from time to time, including committees to manage Business Development, Financing and Pricing, and Corporate Strategy, as appropriate.

Audit Committee

Our Audit Committee is currently composed of Mr. Jagpal, Ms. Hunter, Dr. Freund, and Mr. Lobacki and following the Annual Meeting, our Audit Committee will be composed of Mr. Jagpal, Ms. Hunter and Mr. Lobacki. Mr. Jagpal is the Chair of our Audit Committee. The composition of our Audit Committee meets the requirements for independence under the current Nasdaq Stock Market and SEC rules and regulations. Each member of our Audit Committee is financially literate. In addition, our Board of Directors has determined that each of Mr. Jagpal and Ms. Hunter is an “Audit Committee financial expert” as defined in Item

407(d)(5)(ii) of Regulation S-K promulgated under the Securities Act. Our Audit Committee is directly responsible for, among other things:

Compensation Committee

Our Compensation Committee is composed of Mr. Lobacki, Mr. Petree, and Dr. Wigginton. Mr. Lobacki is the Chair of our Compensation Committee. The composition of our Compensation Committee meets the requirements for independence under the current Nasdaq Stock Market and SEC rules and regulations. Our Compensation Committee is responsible for, among other things:

The Compensation Committee has the sole authority and responsibility, subject to any approval by the Board of Directors which the Compensation Committee or legal counsel determines to be desirable or required by applicable law or the Nasdaq rules, to determine all aspects of executive compensation packages for the Chief Executive Officer and other executive officers. The Compensation Committee also makes recommendations to our Board of Directors regarding the form and amount of compensation of non-employee directors. The Compensation Committee may take into account the recommendations of the Chief Executive Officer with respect to compensation of the other executive officers, and the recommendations of the Board of Directors or any member of the Board of Directors with respect to compensation of the Chief Executive Officer and other executive officers.

The Compensation Committee engaged an independent executive compensation consulting firm, Frederic W. Cook & Co., Inc., or FW Cook, to evaluate our executive compensation and Board of Directors compensation program and practices and to provide advice and ongoing assistance on these matters for the fiscal year ended December 31, 2024. Specifically, FW Cook was engaged to:

Representatives of FW Cook met informally with the Chair of the Compensation Committee and attended the regular meetings of the Compensation Committee, including executive sessions from time to time without any members of management present. During the fiscal year ended December 31, 2024, FW Cook worked with the Compensation Committee to assist the Committee in satisfying its responsibilities and undertook no projects for management without the Committee’s prior approval. The Compensation Committee has determined that none of the work performed by FW Cook during the fiscal year ended December 31, 2024 raised any conflict of interest.

Nominating and Governance Committee

Our Nominating and Governance Committee is composed of Mr. Panek, Ms. Matsui and Mr. Petree. Mr. Panek is the Chair of our Nominating and Governance Committee. Our Nominating and Governance Committee is responsible for, among other things:

Science and Technology Committee

Our Science and Technology Committee is composed of Dr. Wigginton, Dr. Dybbs, Ms. Hunter and Mr. Panek. Dr. Wigginton is the Chair of our Science and Technology Committee. Our Science and Technology Committee is responsible for, among other things:

Code of Business Conduct and Ethics

Our Board of Directors has adopted a code of business conduct and ethics that applies to all of our employees, officers and directors, including our Chief Executive Officer, Chief Financial Officer and other executive and senior financial officers. We intend to disclose future amendments to certain provisions of our code of business conduct, or waivers of these provisions, on our website or in public filings. The full text of our code of business conduct is posted on the investor relations section of our website at https://ir.sutrobio.com/corporate-governance/governance-overview.

Corporate Social Responsibility

We believe that corporate social responsibility (“CSR”) initiatives are important to our business and to creating sustainable value for our stockholders and wider stakeholder group. Our Board of Directors and management are committed to these initiatives and believe these efforts will benefit our employees, partners, and the communities in which we operate.

Insider Trading Policy and Anti-hedging

We have adopted an Insider Trading Policy that governs the purchase, sale and/or other dispositions of our securities by directors, officers and employees. Our Insider Trading Policy also provides that we will not transact in any of our own securities unless in compliance with U.S. securities laws and also provides that our General Counsel will serve as the Compliance Officer who administers, interprets and enforces our Insider Trading Policy. In addition, our Insider Trading Policy prohibits our directors, officers and employees from purchasing financial instruments, or otherwise engaging in transactions, that hedge or offset, or are designed to hedge or offset, any decrease in market value of our common stock, such as prepaid variable forward contracts, equity swaps, collars, forward sale contracts and exchange funds. We believe that our Insider Trading Policy is reasonably designed to promote compliance with insider trading laws, rules and regulations, and the Nasdaq listing standards applicable to us. A copy of our Insider Trading Policy is filed as Exhibit 19.1 to our 2024 Annual Report on Form 10-K.

Compensation Committee Interlocks and Insider Participation

During 2024, Mr. Lobacki, Mr. Petree, and Dr. Wigginton served on our Compensation Committee. None of our current executive officers has served as a member of the Board of Directors, or as a member of the Compensation or similar Committee, of any entity that has one or more executive officers who served on our Board of Directors or Compensation Committee during the fiscal year ended December 31, 2024.

Board and Committee Meetings and Attendance

The Board of Directors and its Committees meet regularly throughout the year and also hold special meetings and act by written consent from time to time. During 2024, the Board of Directors held seven meetings including video conference meetings; the Audit Committee held four meetings; the Compensation Committee held six meetings; the Science and Technology Committee held five

meetings; and the Nominating and Governance Committee held four meetings. During 2024, none of the directors attended fewer than 75% of the aggregate of the total number of meetings held by the Board of Directors during his or her tenure and the total number of meetings held by all Committees of the Board of Directors on which such director served during his or her tenure. The independent members of the Board of Directors also meet separately without management directors on a regular basis to discuss such matters as the independent directors consider appropriate.

Board Attendance at Annual Stockholders’ Meeting

We invite and encourage each member of our Board of Directors to attend our annual meetings of stockholders. All of our directors attended our 2024 annual meeting of stockholders, which was held virtually. We do not have a formal policy requiring attendance of our annual meetings of stockholders by the members of our Board of Directors.

Communication with Directors

Stockholders and interested parties who wish to communicate with our Board of Directors, non-management members of our Board of Directors as a group, a Committee of the Board of Directors or a specific member of our Board of Directors (including our Chair) may do so by letters addressed to:

Sutro Biopharma, Inc.

c/o Corporate Secretary

111 Oyster Point Boulevard

South San Francisco, California, 94080

All communications by letter addressed to the attention of our Corporate Secretary will be reviewed by the Corporate Secretary and provided to the members of the Board of Directors unless such communications are unsolicited items, sales materials and other routine items and items unrelated to the duties and responsibilities of the Board of Directors.

Considerations in Evaluating Director Nominees

The Nominating and Governance Committee is responsible for identifying, considering and recommending candidates to the Board of Directors for Board membership. A variety of methods are used to identify and evaluate director nominees, with the goal of maintaining and further developing a diverse, experienced and highly qualified Board of Directors. Candidates may come to our attention through current members of our Board of Directors, professional search firms, stockholders or other persons.

The Nominating and Governance Committee will recommend to the Board of Directors for selection all nominees to be proposed by the Board of Directors for election by the stockholders, including approval or recommendation of a slate of director nominees to be proposed by the Board of Directors for election at each annual meeting of stockholders, and will recommend all director nominees to be appointed by the Board of Directors to fill interim director vacancies.

Our Board of Directors encourages selection of directors who will contribute to the company’s overall corporate goals. The Nominating and Governance Committee may from time to time review and recommend to the Board of Directors the desired qualifications, expertise and characteristics of director candidates, including such factors as business experience, diversity and personal skills in life sciences and biotechnology, finance, marketing, financial reporting and other areas that are expected to contribute to an effective Board of Directors. Exceptional candidates who do not meet all of these criteria may still be considered. In evaluating potential candidates for the Board of Directors, the Nominating and Governance Committee considers these factors in the light of the specific needs of the Board of Directors at that time.

In addition, under our Corporate Governance Guidelines, a director is expected to spend the time and effort necessary to properly discharge such director’s responsibilities. Accordingly, a director is expected to regularly attend meetings of the Board of Directors and Committees on which such director sits, and to review prior to meetings material distributed in advance for such meetings. Thus, the number of other public company boards and other boards (or comparable governing bodies) on which a prospective nominee is a member, as well as his or her other professional responsibilities, will be considered. Also, under our Corporate Governance Guidelines, there are no limits on the number of three-year terms that may be served by a director. However, in connection with evaluating recommendations for nomination for reelection, the Nominating and Governance Committee considers director tenure. We value diversity on a company-wide basis but have not yet adopted a specific policy regarding Board diversity, though we plan to comply with any applicable legal and listing requirements for director diversity.

Stockholder Recommendations for Nominations to the Board of Directors

The Nominating and Governance Committee will consider properly submitted stockholder recommendations for candidates for our Board of Directors who meet the minimum qualifications as described above. The Nominating and Governance Committee does not intend to alter the manner in which it evaluates candidates, including the minimum criteria set forth above, based on whether or not the candidate was recommended by a stockholder. A stockholder of record can nominate a candidate for election to the Board of Directors by complying with the procedures in Article I, Section 1.12 of our Amended and Restated Bylaws. Any eligible stockholder who wishes to submit a nomination should review the requirements in the Amended and Restated Bylaws on nominations by stockholders.

Any nomination should be sent in writing to our Corporate Secretary, Sutro Biopharma, Inc., 111 Oyster Point Boulevard, South San Francisco, California, 94080. Submissions must include the full name of the proposed nominee, complete biographical information, a description of the proposed nominee’s qualifications as a director, other information regarding the nominee and proposing stockholder as specified in our Amended and Restated Bylaws, and certain representations regarding the nomination. Any such submission must be accompanied by the written consent of the proposed nominee to be named as a nominee and to serve as a director if elected. These candidates are evaluated at meetings of the Nominating and Governance Committee and may be considered at any point during the year. If any materials are provided by a stockholder in connection with the recommendation of a director candidate, such materials are forwarded to the Nominating and Governance Committee.

Additional information regarding the process for properly submitting stockholder nominations for candidates for membership on our Board of Directors is set forth below under “Stockholder Proposals to Be Presented at Next Annual Meeting.” In addition to satisfying the foregoing requirements under our Amended and Restated Bylaws, to comply with the universal proxy rules, stockholders who intend to solicit proxies in support of director nominees other than the Company’s nominees for the 2026 Annual Meeting of Stockholders must provide notice that sets forth the information required by Rule 14a-19 under the Exchange Act.

PROPOSAL NO. 1

ELECTION OF CLASS I DIRECTORS

Our Board of Directors is divided into three classes. Each class serves for three years, with the terms of office of the respective classes expiring in successive years. Directors and director nominees in Class I will stand for election at this meeting. The terms of office of directors in Class II and Class III do not expire until the annual meetings of stockholders to be held in 2026 and 2027, respectively. Our Nominating and Governance Committee recommended to our Board of Directors, and our Board of Directors nominated Dr. Wigginton,Ms. Hunter and Dr. Dybbs, each an incumbent Class I director, for election as Class I directors at the Annual Meeting. At the recommendation of our Nominating and Governance Committee, our Board of Directors proposes that each of the Class I nominees be elected as a Class I director for a three-year term expiring at the annual meeting of stockholders to be held in 2028 and until such director’s successor is duly elected and qualified or until such director’s earlier resignation or removal.

John Freund, M.D., who has served on our Board since 2014, has decided not to stand for re-election. Dr. Freund’s term will expire at the conclusion of our 2025 Annual Meeting. The Board is grateful to Dr. Freund for his dedication, many years of service, and contributions as a director of Sutro. Dr. Freund will continue to advise our management team as a consultant.

Each director will be elected by a plurality by the holders of the shares present in person or represented by proxy at the meeting and entitled to vote on the election of directors. This means that the three individuals nominated for election to the Board of Directors at the Annual Meeting receiving the highest number of “FOR” votes will be elected. You may either vote “FOR” one, two, or all of the nominees or “WITHHOLD” your vote with respect to one, two, or all of the nominees. A “WITHHOLD” vote will have the same effect as an abstention. Shares represented by proxies will be voted “FOR” the election of each of the Class I nominees, unless the proxy is marked to withhold authority to so vote. You may not cumulate votes in the election of directors. If any nominee for any reason is unable to serve, the proxies may be voted for such substitute nominee as the proxy holders, who are officers of our company, might determine. Each nominee has consented to being named in this proxy statement and to serve if elected. Proxies may not be voted for more than two directors.

Nominees to the Board of Directors

The nominees and their ages as of March 31, 2025 are provided in the table below. Additional biographical information for each nominee is set forth in the text below the table.

(1) Member of our Audit Committee

(2) Member of our Science and Technology Committee

(3) Member of our Compensation Committee

Heidi Hunter has served as a member of our Board of Directors since November 2021. Ms. Hunter is the former President of Cardinal Health Specialty Solutions, a specialty healthcare business. Prior to Cardinal Health, Ms. Hunter served as Senior Vice President for UCB (Union Chimique Belge), a multinational biopharmaceutical company with a primary focus on neurology and immunology disorders from September 2015 to September 2020. Ms. Hunter also served as Senior Vice President and General Manager of Boehringer lngelheim, a pharmaceutical company, from 2011 to 2015. Prior to Boehringer lngelheim, Ms. Hunter held similar roles in sales and marketing at Ciba-Geigy (today part of Novartis) and Wyeth Pharmaceuticals LLC (today part of Pfizer) where she led their oncology business. Ms. Hunter also serves on the Board of Directors of Vicore Pharma Holding AB, Bavarian Nordic and IO Biotech. Ms. Hunter received a B.A in Economics from University of Michigan and a M.B.A. from University of Chicago - Booth School of Business. We believe that Ms. Hunter is qualified to serve on our Board of Directors because of her extensive experience in building and developing talent and high-performance teams in the pharmaceutical sector with the skills, motivation, and culture to achieve sustainable results. Ms. Hunter’s experience in various senior management positions, including as the former President of Cardinal Health Specialty Solutions, a portfolio of specialty healthcare businesses, strengthens our Board of Directors’ ability to oversee the important human capital management element of our company.

Jon Wigginton, M.D., has served as a member of our Board of Directors since November 2020. Dr. Wigginton is a physician and scientist with expertise in cancer immunotherapy drug development. He has over 25 years of experience in clinical oncology, with leadership experience in both academia and industry. Dr. Wigginton currently serves as President, Research and Development at

Bright Peak Therapeutics. Most recently, he was Senior Advisor and Chairman of the SAB at Cullinan Oncology, Inc., having served previously as the Chief Medical Officer focused on developing oncology therapeutics, and as an advisor for MPM Capital, a healthcare investment firm from 2020 to 2021. From August 2013 to March 2020, Dr. Wigginton served as Senior Vice President, Clinical Development and Chief Medical Officer for MacroGenics, Inc., a clinical-stage biopharmaceutical company focused on discovering and developing innovative monoclonal antibody-based therapeutics. From 2008 to 2013, Dr. Wigginton served as the Therapeutic Area Head, Immuno-Oncology, Early Clinical Research and Executive Director, Discovery Medicine-Clinical Oncology at Bristol-Myers. From 2006 to 2008, Dr. Wigginton served as the Director of Clinical Oncology at Merck Research Laboratories. During his academic career, Dr. Wigginton has held several positions at the National Cancer Institute Center for Cancer Research, including Head of Investigational Biologics Section, Pediatric Oncology Branch. Dr. Wigginton also served as a member of the Board of Directors of Checkmate Pharmaceuticals from January 2022 through May 2022, when the company was acquired by Regeneron. Dr. Wigginton previously served as President and as a member of the Board of directors of the Society for Immunotherapy of Cancer (non-profit). Dr. Wigginton received an M.D. and B.S. in Biology from the University of Michigan. We believe that Dr. Wigginton is qualified to serve on our Board of Directors because of his years of experience in clinical oncology and immunotherapy drug development. Dr. Wigginton’s significant experience in developing strategies that ultimately resulted in FDA approval of new treatment options offers a valuable perspective to our Board of Directors’ discussions regarding clinical development of new oncology therapeutics.

Michael Dybbs, Ph.D., has served as a member of our Board of Directors since July 2018. Dr. Dybbs is currently a partner at Samsara BioCapital, where he has worked since March 2017. Prior to joining Samsara, Dr. Dybbs was a partner at New Leaf Venture Partners, where he worked from May 2009 until September 2016. Before joining New Leaf Venture Partners, L.L.C., Dr. Dybbs was a principal at the Boston Consulting Group. Dr. Dybbs currently serves on the boards of directors of Nkarta Therapeutics (NKTX) and several private companies. Dr. Dybbs previously served on the boards of directors of Versartis, Inc. and Dimension Therapeutics, Inc. Dr. Dybbs received an A.B. in biochemical sciences from Harvard College and a Ph.D. in molecular biology from University of California, Berkeley, where he was awarded a Howard Hughes Medical Institute fellowship. We believe that Dr. Dybbs is qualified to serve on our Board of Directors because of his financial and strategic expertise as well as his deep understanding of the life sciences sector developed over years of investing and advising companies of all sizes. Our Board of Directors particularly values Dr. Dybbs’s experience in evaluation of and development of messaging strategies for clinical data.

Continuing Directors

The directors who are serving for terms that end following the Annual Meeting and their ages as of March 31, 2025 are provided in the table below. Additional biographical information for each nominee is set forth in the text below the table.

(1) Member of our Science and Technology Committee

(2) Member of our Audit Committee

(3) Member of our Compensation Committee

(4) Member of our Nominating and Governance Committee

Connie Matsui has served as a member, and Chair, of our Board of Directors since June 2019 and brings over 18 years of general management experience in the biotechnology industry. From 2004 to 2009, Ms. Matsui served in various leadership positions at Biogen Idec, Inc., including as Executive Vice President, Knowledge and Innovation Networks and Executive Committee member. Prior to that, Ms. Matsui served in various leadership positions at IDEC Pharmaceuticals, a predecessor of Biogen Idec, including Senior Vice President; Collaboration Chair for the late-stage development and commercialization of rituximab (tradenames: Rituxan® and MabThera®) in partnership with Roche and Genentech; and Project Leader for Zevalin®, the first radioimmunotherapy approved by the U.S. FDA. Prior to entering the biotechnology industry, Ms. Matsui worked for Wells Fargo Bank in general management, marketing and human resources. Ms. Matsui currently serves on the boards of directors of Halozyme Therapeutics, Inc. and Artelo Biosciences, Inc., and has served on not-for-profit boards at the local, national and global level. Ms. Matsui received a B.A. and an M.B.A. from Stanford University. We believe that Ms. Matsui is qualified to serve on our Board of Directors because of her wealth of operational and managerial experience, including her extensive knowledge of the biotechnology industry, her service in other public

company management teams and boards and her expertise in organizational and operational development. Her operational development experience includes serving as a Collaboration Chair for the late-stage development and commercialization of rituximab in the three-way IDEC Pharmaceuticals, Roche and Genentech collaboration. Her knowledge in these and other areas provide critical insights to our business, particularly as our Board of Directors considers our collaboration strategies through our proprietary XpressCF® and XpressCF+® platforms.

Jane Chung, R.Ph., has served as our Chief Executive Officer and a member of our Board of Directors since March 2025. From May 2015 to August 2021, Ms. Chung served in several leadership roles at AstraZeneca, including as President and General Manager of AstraZeneca Canada, Vice President of Sales and Marketing of U.S. lmmuno-Oncology, and Senior Commercial Business Director. Prior to that, from May 2013 to May 2015, Ms. Chung served as a Regional Sales Director and Director of Sales Productivity and Effectiveness for Onyx Pharmaceuticals Inc. From October 2003 to May 2013, she served in various commercial roles for Genentech, Inc., including as Commercial Operations Manager, Division Manager and Senior Marketing Manager. Ms. Chung served on the Board of Directors of Viracta Therapeutics, Inc. from 2022 to 2024 and serves on non-profit boards in the science, education, and community development arenas. Ms. Chung received a B.S. in Pharmacy from St. John's University and a B.A. in Psychology from Columbia University. We believe that Ms. Chung is qualified to serve on our Board of Directors because of her role as our Chief Executive Officer as well as her prior experience at various roles within Sutro Biopharma and her broad experience in the biotechnology industry.

James Panek has served as a member of our Board of Directors since January 2020. Since 2011, Mr. Panek has served as an Independent Consultant for various biopharmaceutical companies, and currently serves as Acting COO and Director for CHO Plus, a privately owned biotechnology company. From 2010 to 2011, Mr. Panek served as interim President, Chief Executive Officer and Principal Financial Officer at DiaDexus, Inc. From 2007 to 2010, Mr. Panek served as President, Chief Executive Officer and Principal Financial Officer for VaxGen, Inc., now a subsidiary of DiaDexus, Inc. From 2002 to 2006, Mr. Panek served as Senior and Executive Vice President of VaxGen, Inc., and Co-Chief Executive Officer and Chairman of the Board for Celltrion Inc., then a VaxGen manufacturing joint venture in Inchon, Korea. In his role with Celltrion, Mr. Panek was responsible for the development and FDA licensure of the first large scale biopharmaceutical manufacturing facility in Asia. From 1982 to 2001, Mr. Panek served in various capacities with Genentech, Inc., including Senior Vice President, Product Operations, and Vice President, Manufacturing, Engineering and Facilities, where he led the development of the world’s largest biotechnology manufacturing facility and was responsible for all operations involved in supplying products for preclinical, clinical, and commercial use. Prior to joining Genentech, Mr. Panek spent six years with Eli Lilly in a variety of engineering and development positions. Mr. Panek previously served on the boards of directors of DiaDexus, Inc., VaxGen, Inc. and Celltrion Inc. We believe that Mr. Panek is qualified to serve on our Board of Directors because of his 30 years of leadership experience in the biopharmaceutical industry. In particular, Mr. Panek has broad and deep extensive manufacturing and process development experience in our industry, including leading the construction, qualification and operation of Genentech’s pioneering large scale commercial manufacturing facility and his deep experience in managing supply chains and ensuring supply of preclinical, clinical and commercial products.

Joseph M. Lobacki has served as a member of our Board of Directors since February 2017. From January 2020 to January 2024, Mr. Lobacki served as president and CEO of Artax, a private biopharmaceutical company developing treatments for autoimmune and inflammatory diseases focused on modulating the T-Cell Receptor response to antigen stimulation. Since January 2024, Mr. Lobacki has served in an advisory role at Artax, and as an independent consultant to Biotech companies. Previously, Mr. Lobacki served as Executive Vice President and Chief Commercial Officer for Verastem, Inc., a biopharmaceutical company focused on the development and commercialization of therapies for the treatment of hematologic malignancies. From November 2016 to December 2017, Mr. Lobacki served as Chief Operating Officer for Crestovo, a clinical-stage biopharmaceutical company focused on microbiome therapies. From 2014 to 2016, Mr. Lobacki served as Chief Commercial Officer at Medivation, Inc., a biopharmaceutical company focused on development of novel therapies for the treatment of serious diseases. From 2012 to 2014, Mr. Lobacki also served as General Manager of Oncology and an independent biotechnology consultant at Idera Pharmaceuticals, Inc., a biopharmaceutical company focused on therapies for cancer and rare diseases. Previously, Mr. Lobacki served as Senior Vice-President and Chief Commercial Officer at Micromet, Inc., Senior Vice-President and General Manager of US Transplant and Oncology at Genzyme Corporation and in various other positions at SangStat Medical Corporation, Cell Pathways, Inc., Rhone-Poulenc Rorer and Lederle Laboratories. Mr. Lobacki previously served on the Board of Directors of Celator Pharmaceuticals Inc. Mr. Lobacki received a B.S. in Biology from Boston College and a B.S. in Pharmacy from the Massachusetts College of Pharmacy. We believe that Mr. Lobacki is qualified to serve on our Board of Directors because of his extensive biopharmaceutical managerial and commercial experience, including his positions of Chief Commercial Officer, Chief Operating Officer, Executive Vice President and Chief Executive Officer of biopharma companies. His broad understanding of medical affairs and commercial development due to his experiences contributes an important perspective to our Board of Directors’ discussions regarding commercial strategy, business development and human capital management matters.

Daniel H. Petree, has served as a member of our Board of Directors since August 2009. In April 2012, Mr. Petree co-founded Four Oaks Partners Consulting, LLC, which provided transaction advisory services to small and medium-sized life science companies until 2021 and in 2000, Mr. Petree co-founded P2 Partners, LLC, Four Oaks' predecessor in the same business which operated until 2012. Before co-founding P2 Partners, Mr. Petree served as President and Chief Operating Officer of Axys Pharmaceuticals, Inc., Executive Vice President and Chief Financial Officer of Arris Pharmaceuticals, Incorporated and Vice President of Business Development at TSI Corporation and was a corporate and securities lawyer. Mr. Petree previously served on the boards of directors of Lpath, Inc., Biocept, Inc. and Cypress Bioscience, Inc. along with a number of privately held biotechnology companies. Mr. Petree received an A.B. in History and Political Science from Stanford University and a J.D. from the University of Michigan Law School. We believe that Mr. Petree is qualified to serve on our Board of Directors because of his deep knowledge and expertise in structuring and negotiating pharmaceutical partnering arrangements and strategic transactions. His significant business development and financing expertise, and in particular his experience with asset monetization, provides our Board of Directors with valuable insight into financing and growth strategies for us.

Sukhi Jagpal has served as a member of our Board of Directors since August 2024. Mr. Jagpal brings over twenty years of experience across the biotechnology industry. He previously served as the Chief Financial Officer of Sierra Oncology, guiding the company from its initial public offering in 2015 through to the completion of its $1.9 billion acquisition by GSK in 2022. Previously, Mr. Jagpal served as the Chief Financial Officer of QLT Inc., a public biotechnology company focused primarily on ophthalmology in addition to oncology and dermatology, from 2012 to 2015, where he also served as the Senior Director, Finance and Corporate Controller. Prior to joining QLT in 2003, Mr. Jagpal held senior finance positions with Pivotal Corporation, 360networks Inc, and KPMG LLP. Mr. Jagpal is a Chartered Professional Accountant, a Chartered Business Valuator, and holds an M.B.A. from the S.C. Johnson Graduate School of Management, Cornell University. We believe that Mr. Jagpal is qualified to serve on our Board of Directors because his financial and accounting experience in guiding biotechnology companies, and in particular his prior leadership positions in the biotechnology industry, provides valuable insight.

Family Relationships

There are no familial relationships among any of our directors and executive officers.

Non-Employee Director Compensation

Our compensation arrangements for non-employee directors are reviewed periodically by our Compensation Committee and our Board of Directors. In addition, at the Compensation Committee’s direction, FW Cook, the Compensation Committee’s independent compensation consultant, provided a competitive analysis of director compensation levels, practices and design features as compared to the general market as well as to our compensation peer group. We last evaluated and adjusted compensation for our non-employee directors in 2024 and plan to do so again in 2026. The adjustments made in 2024 are noted below.

Our non-employee directors receive the following compensation pursuant to a program adopted by our Board of Directors:

Non-employee directors are also reimbursed for reasonable expenses incurred in serving as a director, including travel expenses for attending meetings of our Board of Directors.

The following table sets forth the compensation earned by or paid to the non-employee directors who served during 2024 for services provided during the year ended December 31, 2024. Mr. Newell, our former Chief Executive Officer, received no compensation for his service as a director during 2024.

The following table sets forth the number of outstanding equity awards held by the non-employee directors who served during 2024 as of December 31, 2024:

OUR BOARD OF DIRECTORS RECOMMENDS A VOTE “FOR” THE ELECTION OF EACH OF THE NOMINATED CLASS I DIRECTORS.

PROPOSAL NO. 2

RATIFICATION OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

Our Audit Committee has selected Ernst & Young LLP as our principal independent registered public accounting firm to perform the audit of our financial statements for the fiscal year ending December 31, 2025. Ernst & Young LLP audited our financial statements for the fiscal years ended December 31, 2024 and 2023. We expect that representatives of Ernst & Young LLP will be present at the Annual Meeting, will be able to make a statement if they so desire and will be available to respond to appropriate questions.

At the Annual Meeting, the stockholders are being asked to ratify the appointment of Ernst & Young LLP as our independent registered public accounting firm for the fiscal year ending December 31, 2025. Although ratification by stockholders is not required by law, our Audit Committee is submitting the selection of Ernst & Young LLP to our stockholders because we value our stockholders’ views on our independent registered public accounting firm and as a matter of good corporate governance. If this proposal does not receive the affirmative approval of a majority of the votes cast on the proposal, the Audit Committee would reconsider the appointment. Notwithstanding its selection and even if our stockholders ratify the selection, our Audit Committee, in its discretion, may appoint another independent registered public accounting firm at any time during the year if the Audit Committee believes that such a change would be in our best interests and the interests of our stockholders.

The following table presents fees for professional audit services rendered by Ernst & Young LLP for the audit of our annual financial statements for the years ended December 31, 2024 and 2023.

Principal Accountant Fees and Services

Policy on Audit Committee Pre-Approval of Audit and Permissible Non-Audit Services of Independent Registered Public Accounting Firm

Our Audit Committee generally pre-approves all audit and permissible non-audit services provided by the independent registered public accounting firm. These services may include audit services, audit-related services, tax services and other services. Pre-approval is detailed as to the particular service or category of services and is generally subject to a specific budget. The independent registered public accounting firm and management are required to periodically report to the Audit Committee regarding the extent of services provided by the independent registered public accounting firm in accordance with this pre-approval, and the fees for the services performed to date. Our Audit Committee may also pre-approve particular services on a case-by-case basis. All of the services relating to the fees described in the table above were approved by our Audit Committee.

OUR BOARD OF DIRECTORS RECOMMENDS A VOTE “FOR” APPROVAL OF PROPOSAL NO. 2.

REPORT OF THE AUDIT COMMITTEE

The information contained in the following report of the Audit Committee is not considered to be “soliciting material,” “filed” or incorporated by reference in any past or future filing by us under the Securities Exchange Act of 1934, as amended, or the Securities Act of 1933, as amended, unless and only to the extent that we specifically incorporate it by reference.

The Audit Committee has reviewed and discussed with our management and Ernst & Young LLP our audited financial statements as of and for the year ended December 31, 2024. The Audit Committee has also discussed with Ernst & Young LLP the matters required to be discussed by the applicable requirements of the Public Company Accounting Oversight Board (United States) and the U.S. Securities and Exchange Commission.

The Audit Committee has received and reviewed the written disclosures and the letter from Ernst & Young LLP required by applicable requirements of the Public Company Accounting Oversight Board regarding the independent accountant’s communications with the Audit Committee concerning independence and has discussed with Ernst & Young LLP its independence.

Based on the review and discussions referred to above, the Audit Committee recommended to our Board of Directors that the audited financial statements as of and for the year ended December 31, 2024 be included in our Annual Report on Form 10-K for the year ended December 31, 2024 for filing with the U.S. Securities and Exchange Commission.

Submitted by the Audit Committee

Sukhi Jagpal, Chair

Heidi Hunter

John Freund

Joseph Lobacki

SECURITY OWNERSHIP OF CERTAIN BENEFICIAL OWNERS AND MANAGEMENT

The following table sets forth certain information with respect to the beneficial ownership of our common stock as of March 31, 2025, by:

• each stockholder known by us to be the beneficial owner of more than 5% of our common stock;

• each of our directors or director nominees;

• each of our named executive officers; and

• all of our directors and executive officers as a group.

Percentage ownership of our common stock is based on 84,331,145 shares of our common stock outstanding on March 31, 2025. We have determined beneficial ownership in accordance with the rules of the SEC, and thus it represents sole or shared voting or investment power with respect to our securities, and the information is not necessarily indicative of beneficial ownership for any other purpose. Unless otherwise indicated below, to our knowledge, the persons and entities named in the table have sole voting and sole investment power with respect to all shares that they beneficially owned, subject to community property laws where applicable. We have deemed all shares of common stock subject to options or other convertible securities held by that person or entity that are currently exercisable or that will become exercisable within 60 days of March 31, 2025 to be outstanding and to be beneficially owned by the person or entity holding the option for the purpose of computing the percentage ownership of that person or entity but have not treated them as outstanding for the purpose of computing the percentage ownership of any other person or entity. Unless otherwise indicated, the address of each beneficial owner listed in the table below is c/o Sutro Biopharma, Inc., 111 Oyster Point Boulevard, South San Francisco, California 94080.

* Represents beneficial ownership of less than one percent.

EXECUTIVE OFFICERS

The following table provides information regarding our executive officers as of March 31, 2025:

Jane Chung, RPh has served as our Chief Executive Officer and a member of our Board of Directors since March 2025. Ms. Chung’s biographical information is set forth above under the heading “Proposal No. 1 Election of Class I Directors – Continuing Directors.”

Edward Albini has served as our Chief Financial Officer since January 2013 and will be transitioning from his current position effective May 15, 2025. During 2012, Mr. Albini served as a consulting Chief Financial Officer for Carbylan Biosurgery, a company focused on the development and commercialization of advanced biomaterial-based joint therapies. From 2011 to 2016, Mr. Albini also served as Chief Financial Officer and Secretary for Itero Holdings, LLC, a successor entity to Itero Biopharmaceuticals, Inc., a company focused on the development and commercialization of protein therapeutics, at which Mr. Albini served as Chief Financial Officer and Senior Vice President from 2009 to 2011. Previously, Mr. Albini served as Chief Financial Officer of Novacea, Inc. and Lynx Therapeutics, Inc., both biopharmaceutical companies. Mr. Albini received a B.S.C. in Accounting from Santa Clara University and an M.B.A. from the Walter A. Haas School of Business at the University of California, Berkeley. Mr. Albini is also a certified public accountant (inactive status) in California.

Hans-Peter Gerber, Ph.D. has served as our Chief Scientific Officer since September 2023. From April 2022 to August 2023, Dr. Gerber served as Chief Scientific Officer and Co-founder of Codeable Therapeutics, an ADC startup company. From April 2018 to March 2022, Dr. Gerber served as Chief Scientific Officer and Senior Vice President of 3T Biosciences, Inc. From November 2016 to March 2018, Dr. Gerber served as President and Chief Scientific Officer of Maverick Therapeutics, Inc., which was acquired by Takeda Pharmaceutical Company in 2021. Prior to his service at Maverick, Dr. Gerber held leadership positions at several top biopharmaceutical companies, including Genentech, Seattle Genetics, and Pfizer, where he led the R&D group as Chief Scientific Officer. Dr. Gerber earned his M.S. in Biochemistry and his Ph.D in Molecular Biology from the University of Zurich, Switzerland.

Venkatesh Srinivasan, Ph.D. has served as our Chief Technical Officer since May 2023. From April 2022 to May 2023, Dr. Srinivasan served as our Senior Vice President, Process, Analytical and Formulation Development. Prior to that, from March 2011 to March 2022, Dr. Srinivasan worked at Bayer AG, where he was most recently the Vice President of Global Manufacturing Sciences and Technology. Dr. Srinivasan also co-founded GlycoRx Partners, LLC, a company focused on developing novel, half-life extended pharmaceutical proteins and peptides based on a unique glycoengineering platform, where he was a partner from 2009 to 2011. Prior to that, Dr. Srinivasan worked for Phyton Biotech, LLC where he served as Senior Director, Bioprocess Development and Director, Business Development. Dr. Srinivasan received his B.S. in Chemical Engineering from Indian Institute of Technology, Chennai, and his Ph.D. in Chemical Engineering from the State University of New York. He also held post-doctoral appointments at the School of Engineering, Cornell University, and at the Antibody Engineering Laboratory, University of California, Davis.

Barbara Leyman, Ph.D. has served as our Chief Business Development Officer since July of 2024. Prior to joining the Company, from May 2022 to June 2024, she worked at GenEdit, where she oversaw business development, alliance management and corporate strategy functions as the Senior Vice President, Corporate Development. Prior to that role, from September 2018 to April 2022, she held positions of increasing responsibility in business development and corporate strategy at Lyell Immunopharma and Calico Life

Sciences, where she led licensing, R&D collaborations and co-development transactions through due diligence, negotiation and execution. Prior to these positions, from May 2014 to July 2017, Dr. Leyman headed the life sciences team at LRM, a venture capital fund, where she managed investment transactions in biotech companies and served as a director on the boards of three private biotech companies. Dr. Leyman earned her Ph.D. in Molecular Biology from Imperial College at Wye, London University, UK and a Master’s degree in Chemistry and Biotechnology from Ghent University, Belgium.

Anne Borgman, M.D., has served as our Chief Medical Officer since February 2023 and will be transitioning from her current position effective May 1, 2025. Dr. Borgman previously served as Principal, AEB Hematology Oncology Development Consulting from November 2021 to February 2023. From July 2019 to November 2021, Dr. Borgman served as Vice President and Global Therapeutic Area Lead, Hematology-Oncology, at Jazz Pharmaceuticals, Inc. From November 2012 to July 2019, Dr. Borgman served as Vice President, Clinical Research & Development at Exelixis, Inc. Prior to that, Dr. Borgman was Chief Medical Officer and Vice President of Hana Biosciences (now Talon Therapeutics, Inc.), Associate Chief Medical Officer at KaloBios Pharmaceuticals, Inc., and Global Project Head, oncology, at Abbott Laboratories. From 2012 to 2019, Dr. Borgman was a Consulting Associate Professor at Stanford University School of Medicine’s Stem Cell Transplant & Cell Biology program, and from 2001 to 2010, a Clinical Associate at University of Chicago’s Department of Pediatrics, Division of Oncology and Stem Cell Research. Dr. Borgman currently serves on the Board of Directors at Curis, Inc., NextCure, Inc., and NiKang Therapeutics, Inc. Dr. Borgman earned her B.S. in Biochemistry from University of Illinois and her M.D. from Loyola University of Chicago’s Stritch School of Medicine, before completing her residency in Pediatrics at Texas Children’s Hospital and Baylor College of Medicine, and her fellowship in Pediatric Hematology-Oncology at UCLA School of Medicine.

Linda Fitzpatrick has served as our Chief People and Communications Officer since August 2018 and will be transitioning from her current position effective May 1, 2025. From January 2008 to August 2018, Ms. Fitzpatrick served as our VP of Human Resources and Communications in the capacity of Senior Advisor. In addition to her strategic consulting practice, she co-founded Parallax Venture Partners, an early stage health care venture fund in April 2002. From October 1992 to March 2002, Ms. Fitzpatrick served as Vice President of Human Resources, Corporate Communications and Operations for Gilead Sciences, Inc. and from February 1985 to September 1992 she served as Director of Investor Relations and Director of Compensation, Benefits and Systems for Genentech, Inc. in addition to heading the human resources and corporate communications strategy for a variety of publicly held biotechnology companies. Ms. Fitzpatrick also serves on a variety of non-profit boards, including board chair roles, in the science, education and community development arenas. Ms. Fitzpatrick received a B.A. in Psychology and Sociology from San Francisco State University.

EXECUTIVE COMPENSATION

Overview and Narrative

This overview and narrative (“Compensation Disclosure”) describes the key elements of our executive compensation program and compensation decisions for our named executive officers, or NEOs, for 2024. This Compensation Disclosure is intended to be read in conjunction with the tables that immediately follow this section, which provide additional compensation information for our named executive officers. We are a “smaller reporting company” as defined under Rule 405 of the Securities Act of 1933, as amended, and, as such, we are not required to provide the additional disclosures included in this Compensation Disclosure. However, we believe the additional narrative disclosure with respect to our executive compensation program will provide our stockholders with further information regarding our company and our executive compensation program and practices and therefore will assist in their consideration of Proposal No. 3, the non-binding vote with respect to named executive officer compensation.

Our executive compensation programs are designed to attract, motivate and retain qualified and talented executives, incentivize them to achieve our business objectives, and reward them for superior short- and long-term performance and results. The Compensation Committee of the Board of Directors, with input from its independent compensation consultant, oversees these programs and determines compensation for our NEOs.

Our 2024 NEOs were:

Executive Summary

We are an oncology company developing site-specific and novel-format antibody drug conjugates, or ADCs, enabled by our proprietary integrated cell-free protein synthesis platform, XpressCF®, and our site-specific conjugation platform, XpressCF+®. We aim to design and develop therapeutics using the most relevant and potent modalities, including ADCs, bispecific ADCs, immunostimulatory ADCs, or iADCs, and dual conjugate ADCs, or ADC2s. Our molecules are directed primarily against clinically validated targets where the current standard of care is suboptimal. We believe that our platform allows us to accelerate the discovery and development of potential first-in-class and/or best-in-class molecules by enabling the rapid and systematic evaluation of protein structure-activity relationships to create optimized homogeneous product candidates. Our mission is to transform the lives of patients by creating medicines with improved therapeutic profiles for areas of unmet need.

Our NEO compensation program in 2024 was designed to be aligned with industry practices and align executive compensation with our performance, with an emphasis on long-term equity compensation in the form of stock options and restricted stock units, or RSUs.

Business Highlights

Since 2009, our leadership team has built the Company focusing on our pipeline and platform, delivering on key milestones, furthering our capabilities with strong partner relationships, building the organization, and ensuring the financial strength of the Company.

We have a broad pipeline with multiple assets deployed across multiple oncology indications. Based on our proprietary XpressCF® and XpressCF+® platforms, we have also entered into multi-target, product-focused collaborations with leaders in the field of oncology. In 2024, we advanced multiple ongoing global trials for our lead product candidate, continued to support the development of partnered product candidates in clinical trials and advanced additional potential product candidates towards the clinic.

Key 2024 achievements reflected significant scientific, clinical, and business performance, which we believe have the opportunity to create long-term value for our stockholders. Among our 2024 results were the following achievements:

Stockholder Advisory Vote

At our annual meeting of stockholders on June 6, 2025, we will again conduct a non-binding stockholder advisory vote on the compensation of our named executive officers (commonly known as a “Say-on-Pay” vote). We conducted a Say-on-Pay vote in 2024, in which the stockholders approved on an advisory basis the compensation of our named executive officers with a 98.8% support rate. We value the opinions of our stockholders, and the Compensation Committee and the Board of Directors considered the outcome of the advisory vote, and will continue to do so in the future, including the vote which will take place at the 2025 annual meeting, when making compensation decisions for the NEOs.

Compensation Philosophy, Objectives and Development

Our 2024 compensation strategy emphasizes pay for performance by using both performance-based annual cash incentives and long-term equity awards in the form of stock options and RSUs. Stock options are utilized because they only provide value if the stock price increases. RSUs are also used to retain talent, align with long-term value (both increases and reductions), and because RSUs are less dilutive than stock options. Our stock options generally vest monthly over four years; with a one-year cliff vesting associated with a new hire grant, and our RSUs generally vest annually over four years (with 25% vesting annually), to align with long-term value creation as well as our clinical development and commercialization timeline.

Consistent with our pay-for-performance philosophy, and the long product development life cycles in the biopharmaceuticals industry, the Compensation Committee links the compensation of our executive officers to performance by emphasizing equity compensation opportunities for long-term performance and cash incentives for near-term goal alignment. Thus, the total compensation provided to our executive officers will vary from year to year and will vary between executive officers based on corporate performance, including performance against annual goals that are pre-established by the Compensation Committee, as well as individual performance. The Compensation Committee’s 2024 compensation decisions reflected, among other things, the level of goal achievement related to the potential for long-term value creation from our platform and clinical, manufacturing and business achievements. The Compensation

Committee will continue to consider scientific and business achievements and market capitalization, among the many factors considered, when making compensation decisions.

Our NEOs are also provided market-competitive health and welfare benefits, and as described below, they may be entitled to receive additional benefits if certain criteria are met at termination of employment.

We will continue to refine the design of our compensation program and implement one that is appropriate for our company given our business, industry, growth, and other factors.

Program Development and Role of Compensation Committee, Compensation Consultant and Management

Role of Compensation Committee. Our Compensation Committee is responsible for overseeing the total compensation of our executive officers, including the underlying philosophy and related policies. As such, the Compensation Committee designs, implements, reviews and approves all compensation for our CEO and our other executive officers. From time to time, and in conjunction with our Compensation Committee, the independent members of our Board of Directors, including our Chairperson, may also be involved in setting the compensation of our CEO and other executive officers and determining the corporate objectives upon which our short-term incentives are based and assessed. Our Compensation Committee’s decisions and recommendations regarding executive compensation are based on the Compensation Committee’s assessment of the performance of our company and each individual executive officer, as well as other factors, such as prevailing industry trends, retention, and the competitive market for executive talent.

The Compensation Committee consults with its independent compensation consultant, legal counsel and other advisors in designing our compensation program, including in evaluating the competitiveness of individual compensation and in relation to our performance goals. The Compensation Committee also considers peer company data and factors such as the past, current and expected contributions of each NEO, our corporate performance and strategic focus, global economic conditions, the mix of compensation that would be most appropriate for each NEO, and such officer’s particular responsibilities, experience, level of accountability and decision authority.

Role of CEO and Management. As part of the process for setting the compensation of our NEOs, our Chief Executive Officer provides the Compensation Committee with his performance assessments of the company and of the individual NEOs and recommends to the Compensation Committee base salaries, target annual cash incentives (as a percentage of base salary), annual cash incentive payouts (actual incentive paid based on performance against goals), and stock-based compensation for our NEOs (other than for himself). The Compensation Committee considers our Chief Executive Officer’s input and can accept, reject or modify these recommendations in its discretion.

The Compensation Committee meets in executive session without management. Various members of management may attend Committee meetings, and they and other employees, as well as outside advisors or consultants, may be invited by the Compensation Committee to make presentations, provide financial, competitive market, or other background information or advice. None of our NEOs were present during the Compensation Committee’s determinations regarding his or her own compensation.

Role of Independent Compensation Consultant & Market Data. The Compensation Committee has retained FW Cook as its compensation consultant. FW Cook reports directly to the Compensation Committee and takes its direction from the Chair of the Compensation Committee, working with management on select issues under the Compensation Committee’s oversight. The Compensation Committee retained FW Cook in 2024 to provide data, context, and advice regarding executive officer compensation and our peer group, and to assist with compensation risk assessments.

Peer Groups Used in Program Development and Compensation Decisions

Our Compensation Committee considers peer data as one factor in its overall compensation analysis and for purposes of assessing the competitiveness of the executive compensation program. An individual NEO may earn more or less than the peer group median depending on factors described below under the heading “2024 Compensation Decisions,” including the individual’s experience, role, and past and expected future performance.

Fiscal 2024 Peer Group

In the third quarter of 2023, the Compensation Committee reviewed and updated our peer group to include the group of companies set forth below based on, among other considerations, objective size criteria, including industry, market capitalization, headcount, pipeline, location, scope of operations and commercial stage. We refer to this peer group of 19 companies as the “2024 Peer Group.” When this peer group was approved by the Compensation Committee to inform 2024 compensation, these companies had July 17, 2023 market capitalizations of between $116 million and $5.0 billion, and our $294 million market capitalization on this date was within the peer range.

Two companies were removed from the 2024 Peer Group following acquisition of those organizations: ChemoCentryx and Clovis Oncology. Two companies that fit the Compensation Committee’s desired criteria and had market capitalization on July 17, 2023 ranging from $475 million to $597 million were added to the 2024 Peer Group: IGM biosciences and Nurix Therapeutics.

Compensation Consultant Conflict of Interest Analysis

The Compensation Committee has determined that the work of FW Cook and the individual compensation advisors employed by FW Cook does not create any conflict of interest. In making that determination, the Compensation Committee took into consideration the following factors: (i) the provision of other services to us by FW Cook; (ii) the amount of fees we paid FW Cook as a percentage of FW Cook’s total revenue; (iii) FW Cook’s policies and procedures that are designed to prevent conflicts of interest; (iv) any business or personal relationship of FW Cook or the individual compensation advisors employed by FW Cook with a Sutro executive officer; (v) any business or personal relationship of the individual compensation advisors with any member of the Compensation Committee; and (vi) any Sutro stock owned by FW Cook or the individual compensation advisors employed by the consultant. During 2024, we paid FW Cook fees that constituted less than 1% of FW Cook’s total revenue.

2024 Compensation Decisions

Summary

Most 2024 compensation decisions were made in the first quarter of 2024 and were significantly influenced by our scientific and business achievements together with the competitive market for experienced talent. Our 2024 compensation decisions were based on a review of individual performance and potential; achievement of the Company’s corporate goals, including advancing our research and clinical pipelines and financial performance; and a market analysis of competitive compensation based on our 2024 peer group.

Following are highlights of the 2024 compensation decisions:

Base Salary

The purpose of base salary is to provide fixed compensation to attract, retain and motivate executives with the qualifications desired for the individual position. The base salary we provide each of our NEOs is influenced by a number of factors, including the individual’s position, scope of responsibilities, breadth and depth of experience, performance to date, expected future contribution, and their overall mix of base salary, performance-based cash incentives and equity compensation.

The 2024 base salaries for our NEOs were as follows:

Performance-Based Cash Incentives

During 2024, all of our NEOs were eligible for annual performance-based cash incentive bonuses, which were designed to reward achievement of certain annual corporate goals that the Company believes will ultimately drive stockholder value. Each performance-based cash incentive bonus opportunity is expressed as a target percentage of annual base salary. Mr. Newell’s target performance-based cash bonus was 60% of his annual base salary, Ms. Chung’s target was 50% of her annual base salary and Mr. Albini’s target was 40% of his annual base salary. The incentive target as a % of salary for each of our NEOs remained the same in 2024 as in 2023.

No amount of incentive award was guaranteed. Each NEO’s incentive award payout was based on the level of achievement of the corporate goals that were established by the Compensation Committee in early 2024, and for NEOs other than our CEO, the participant’s role in such goal achievement and the weighting of the goals, with the Compensation Committee retaining discretion to adjust or modify actual awards. The Compensation Committee did not exercise this discretion.

The corporate performance goals for the fiscal year 2024 cash incentive bonus program were determined by the Compensation Committee and included certain developmental, research, financial, and operational milestones, as discussed below. These milestones were selected to drive appreciation of value in the Company, including maintaining timelines for development of the Company’s and the Company’s partners’ clinical and preclinical product candidates, successful conclusion of licensing and/or collaboration transactions, particularly for the Company’s most advanced clinical candidate, expansion and development of the Company’s manufacturing activities, including through third-party contract development and manufacturing organizations, maintenance of an appropriate cash position and runway, and maintaining Company culture and employee morale. Each of these goals pertain to confidential company development and business plans, the disclosure of which in any additional granularity would result in competitive harm to the company. The Compensation Committee believed that each of these goals would be challenging to achieve.

In early 2025, the Compensation Committee assessed our performance against the 2024 corporate goals, using both quantitative measurement and qualitative evaluation. The Compensation Committee determined that the Company had achieved its corporate goals at an overall level of 65% of target. While the Compensation Committee assigned full achievement with respect to non-luvelta proprietary and partnered pipeline progression goals, manufacturing readiness goals and cultural execution goals, the Compensation Committee only granted partial achievement with respect to luvelta development and partnering goals, other business development and dealmaking goals, and financial performance goals. The 2024 corporate goals, the weighting of such goals, and the facts the Compensation Committee considered in determining the achievement of such goals are set forth below.

In assessing the 2024 corporate goals, the Compensation Committee considered achievement in the following categories with the target weightings as noted:

The Compensation Committee determined that the Company partially achieved its goals with respect to Luvelta Development and Partnering, which assessed the Company’s progress in advancing luvelta through clinical development and execution of an outlicense or development and commercialization collaboration agreement with a partner in connection with luvelta. In particular, the Company completed Part 1 of a registrational Phase 2/3 study of luvelta for treatment of platinum resistant ovarian cancer in the first half of 2024, selected a go forward dose for Part 2 of the study following a meeting with the FDA, and made substantial progress in enrolling

Part 2 of the study. In addition, the Company initiated a registrational Phase 2/3 study to assess luvelta in treatment of refractory/relapsed CBF/GLIS AML in a pediatric patient population and initiated a Phase 2 study for the treatment of non-small cell lung cancer with luvelta. Despite this progress, the Company did not achieve its goal of executing an outlicensing or development and commercialization collaboration agreement in connection with luvelta.

The Compensation Committee determined that the Company fully achieved its goals with respect to proprietary pipeline progression, focusing on the progress made to bring STRO-004 to the clinic and to advance the Company’s additional preclinical programs. STRO-004 (as an antibody-drug conjugate with a drug:antibody ratio of 8:1) was nominated as a development candidate in 2024 and is on track to begin clinical studies in 2025 as projected, meeting this part of the goal.

With respect to the goal relating to partnered program progression, the Compensation Committee determined that the Company fully achieved its goals. Our agreements with our collaboration partners do not permit us to disclose the milestones achieved in these relationships because of applicable confidentiality obligations.

The Compensation Committee further determined that the Company partially achieved its goals with respect to new dealmaking, noting that while the Company successfully executed an outlicense of STRO-003 to Ipsen Pharma SAS, it did not execute a new research collaboration agreement.

The Compensation Committee determined that the Company fully achieved its goals in connection with placing manufacturing on track for the next stage. Achievement in this area resulted from substantial completion of the technology transfer of the XtractCF® and other reagents manufacturing processes to our third-party contract development and manufacturing organizations, or CDMOs. The Company also successfully transferred the process for manufacturing antibody intermediates used to make the Company’s clinical products at commercial scale to our CDMO.

With regard to the Company’s financial performance, the Compensation Committee determined that the Company did not achieve its goals. In particular, the Company did not end the year with a cash and investments balance sufficient to fund activities through the end of 2026, while delivering upon short and long-term strategic objectives in accordance with the Company’s goals.

The Compensation Committee determined that the Company fully achieved its goals with respect to its commitment to execution, culture, talent and team. In particular, the Company hired and integrated a significant number of new employees, while maintaining a turnover rate lower than industry standard. The Company further enhanced the maturity of its compliance program, its company-wide learning and development programs, continued to build upon a comprehensive internship program (focusing on individuals who are first in their family to pursue higher education), and leveraged its Diversity, Equity, Inclusion and Belonging Council to support both internal and external development initiatives. In recognition of its efforts in this area, the Company was awarded first place in BioSpace’s list of best places to work for employers with fewer than 1,000 employees.

In summary, based on full achievement in four goals, and partial achievement in two goals, the Compensation Committee determined an overall goal achievement for the Company in 2024 of 65%.

The Compensation Committee awarded Mr. Newell a bonus equal to our corporate performance for the year because it determined that his performance as CEO aligned directly with our corporate performance. The Compensation Committee determined that the bonus achievement for each of the other NEOs is based on both our corporate performance and its assessment of each NEO’s individual contributions towards our corporate performance. The amount of each NEO’s earned cash incentive award at 65% achievement, and their target award, are reflected below:

Equity Compensation

General. We believe that equity grants provide our NEOs with the opportunity to share in increases, if any, in the value of our common stock, reinforce a long-term interest in our corporate performance, and directly motivate our NEOs to maximize long-term stockholder value. The potential realized value of certain grants depends on our stock performance and all of our equity grants utilize vesting to encourage our NEOs to continue working for us for the long term.

The Compensation Committee determines the size and type of equity awards after evaluating various factors applicable at the time of each such grant in their totality, which has included, among other things: the particular NEO’s role and responsibilities and the Compensation Committee’s view of the officer’s individual performance; the prior equity awards granted to such individual; retentive value of prior awards; our corporate performance; the value of equity grants; comparative peer data provided by its compensation consultant; and dilution to our stockholders.

All grants to executive officers require the approval of the Compensation Committee.

2024 Equity Grants. The Compensation Committee granted our NEOs equity compensation in the first quarter of 2024 in the form of stock options and RSUs, consistent with our compensation philosophy that our NEOs should have a significant proportion of their total compensation tied to our performance, to encourage retention, and to align their long-term compensation with the interests of our stockholders. The Compensation Committee felt that providing equity opportunities for our NEOs with an equity mix that included RSUs would balance alignment of executives with stockholder growth and support retention during a multi-year product development and commercial cycle. Our Compensation Committee strives to maintain a compensation program that is tied to performance and is competitive with market practices.

The Compensation Committee determined the size of the equity grants based on several factors, including:

The stock option and RSU grants to each of our NEOs are reflected in the table below. The grant values were meaningfully lower than the median of grant value benchmarks from the 2024 Peer Group that were reviewed by the Compensation Committee in late 2023 and early 2024.

2024 Stock Options. The stock options granted to our NEOs in 2024 vest equally in monthly installments over four years.

2024 Restricted Stock Units. The RSUs granted to our NEOs in 2024 vest equally in annual installments over four years.

Benefits Programs

Our employee benefit programs, including our 401(k) plan, employee stock purchase plan, and health and welfare programs, including health savings accounts and flexible spending arrangements, are designed to provide a competitive level of benefits to our employees generally, including our executive officers, and their families. We adjust our employee benefit programs as needed, based upon regular monitoring of applicable laws and practices and the competitive market. Our executive officers are eligible to participate in the same employee benefit plans and programs, and on the same terms and conditions, as all other U.S. full-time employees.

Perquisites and Other Personal Benefits

Currently, we do not view perquisites or other personal benefits as a significant component of our executive compensation program. Accordingly, we do not generally provide perquisites to our executive team. In 2023 and 2024 we did provide housing and relocation allowance to Ms. Chung in connection with her offer of employment and to induce her to relocate to the San Francisco bay area. In the future, we may provide additional or different perquisites or other personal benefits in limited circumstances, such as where we believe it is appropriate to assist an individual executive in the performance of his or her duties, to make our executive team more

efficient and effective and for recruitment, motivation or retention purposes. All future practices with respect to perquisites or other personal benefits will be subject to review and approval by the Compensation Committee.

Employment Agreements and Severance and Change in Control Benefits

We entered into written employment agreements with each of our NEOs that set forth the terms of their employment, including initial base salaries and eligibility to earn a bonus, as well as standard confidentiality and invention assignment agreements. Each of our named executive officers is, or in the case of each of Mr. Newell and Mr. Albini was, employed “at will”. These arrangements are further described under the section below titled “Executive Compensation Tables.”

Our NEOs are entitled to certain severance and change in control benefits under the terms of our executive severance and change in control plan, or Severance Plan. Below is a summary of potential post-termination compensation for our NEOs. We provide these benefits because the Compensation Committee determined that it was appropriate to provide our NEOs with severance compensation if their employment is terminated under certain circumstances. The Compensation Committee believes that the severance benefits are an important element of the NEOs’ competitive pay packages, that they serve important retention and motivation purposes and that such severance benefits, including generally requiring a release of claims against us as a condition to receiving any severance benefits, are best market practice and are in the best interest of the Company and its stockholders.

Severance Benefits

On March 17, 2021, we adopted an executive severance and change in control plan, or Severance Plan, for each of our executives with the title of vice president (or equivalent) or above, including all of our NEOs. Under the Severance Plan, if we terminate an executive other than for cause or if the executive resigns for good reason, each as defined in the Severance Plan, the executive will receive: (i) cash severance payments payable in monthly installments equal to 18 months of his or her annual base salary for our Chief Executive Officer, 15 months for our other chief executives (including the non-CEO NEOs and those chief executives with an additional title) and 9 months for our senior vice presidents and vice presidents; (ii) a pro rata portion of his or her bonus based on actual achievement of applicable metrics for the year and payable at the same time as bonuses are paid generally; (iii) payment of COBRA premiums for continued medical coverage for up to 18 months for our Chief Executive Officer, 15 months for our other chief executives and 9 months for our senior vice presidents and vice presidents; and (iv) accelerated vesting on outstanding time-based stock options and restricted stock units that vest within 18 months for our Chief Executive Officer, 15 months for our other chief executives and 9 months for our senior vice presidents and vice presidents (any performance-based equity awards will only be accelerated according to the terms of such awards).

In the event an executive’s employment terminates without cause or the executive resigns for good reason and such termination occurs on or within 18 months following a change in control, as defined in the Severance Plan, the executive will receive: (i) cash severance payments equal to 18 months of his or her annual base salary for our Chief Executive Officer, 15 months for our other chief executives and 9 months for our senior vice presidents and vice presidents, payable in a lump sum; (ii) a pro rata portion of his or her target bonus for the year, payable in a lump sum; (iii) cash severance payments equal to his or her target bonus for the year multiplied by 1.5 for our Chief Executive Officer, 1.25 for our other chief executives and 0.75 for our senior vice presidents and vice presidents, payable in a lump sum; (iv) payment of COBRA premiums for continued medical coverage for up to 18 months for our Chief Executive Officer, 15 months for our other chief executives and 9 months for our senior vice presidents and vice presidents; and (v) full accelerated vesting on all outstanding stock options and restricted stock units (any performance-based equity awards will only be accelerated according to the terms of such awards).

As a condition to receiving these severance benefits, the executive is required to execute a release of claims agreement in favor of us. The Severance Plan continues in effect for three years and shall automatically renew for successive three-year periods thereafter, unless we give notice of non-renewal prior to such renewal date. Although we have the right to amend or terminate the Severance Plan, we may not do so in any manner that diminishes any benefits being paid to an executive at the time of such amendment or termination.

Tax & Accounting Considerations

We take into account the tax effects of various forms of compensation and the potential for excise taxes to be imposed on our executive officers. There are various provisions of the Code that we consider in determining compensation, including the following:

Section 162(m). Section 162(m) of the Internal Revenue Code generally disallows a tax deduction for compensation in excess of $1 million paid to “covered employees,” which include our current NEOs. As a result, we expect that compensation awarded to our NEOs will not be deductible to the extent it is in excess of the $1 million threshold. In determining the form and amount of compensation for our NEOs, the compensation committee will continue to consider all elements of the cost of such compensation, including Section 162(m). While the compensation committee considers the deductibility of awards as one factor in determining executive compensation, the compensation committee also looks at other factors in making its decisions and retains the flexibility to

award compensation that it determines to be consistent with the goals of our executive compensation program even if the awards are not deductible by us for tax purposes.

Sections 280G and 4999. Any payment or benefit provided to executive officers in connection with a change-in-control transaction may be subject to an excise tax under Section 4999 of the Code. These payments also may not be eligible for a company tax deduction pursuant to Section 280G of the Code. If any of these payments or benefits are subject to the excise tax, they may be reduced to provide the individual with the best after-tax result. The individual will receive a reduced amount so that the excise tax is not triggered, or the individual will receive the full amount of the payments and benefits and then be liable for any excise tax. We have not agreed and are not otherwise obligated to provide any named executive officer with such a “gross-up” or other reimbursement.

We account for stock compensation in accordance with the authoritative guidance set forth in FASB ASC Topic 718, which requires companies to measure and recognize the compensation expense for all share-based awards made to employees and directors over the period during which the award recipient is required to perform services in exchange for the award. We determine both the grant date fair value and the service period based on applicable accounting standards. This calculation is performed for accounting purposes and reported in the compensation tables included in this proxy statement as applicable.

Additional Executive Compensation Practices, Policies and Procedures

Prohibition of Hedging and Pledging. We prohibit our NEOs (and other employees) and non-employee directors from engaging in hedging or monetization transactions involving our securities or contributing our securities to exchange funds that could be interpreted as having the effect of hedging in Company securities.

Compensation Recovery Policy

On November 12, 2023, our Board of Directors adopted a compensation recovery policy (the “Compensation Recovery Policy”) intended to comply with applicable SEC rules and Nasdaq listing standards. The Compensation Recovery Policy is administered by our Compensation Committee (in such capacity, the “Administrator”) and enables us to recover from current and former officers, and such additional employees as may be identified by the Administrator from time to time, incentive-based compensation, as defined in the Compensation Recovery Policy, in the event of an accounting restatement resulting from material noncompliance with any financial reporting requirements under federal securities laws. For more information, see the full text of our Compensation Recovery Policy, which is filed as an exhibit to our Annual Report.

Compensation Policies and Practices as they relate to Risk Management

The Compensation Committee has reviewed our executive and employee compensation programs and does not believe that our compensation policies and practices encourage undue or inappropriate risk taking or create risks that are reasonably likely to have a material adverse effect on us. The reasons for the Compensation Committee’s determination include the following:

Policies and Practices Related to the Grant of Certain Equity Awards

EXECUTIVE COMPENSATION TABLES

Summary Compensation Table

The following table presents summary information regarding the total compensation for services rendered in all capacities that was earned by our named executive officers during the years ended December 31, 2024 and 2023, as applicable.

Offer Letters with NEOs

We have entered into written employment agreements with each of our NEOs that set forth the terms of their employment, including initial base salaries and eligibility to earn a bonus, as well as standard confidentiality and invention assignment agreements. Each of our named executive officers is employed “at will.” The offer letters for Mr. Newell also included certain severance protections, which severance protections have been superseded by the Severance Plan described above in the section entitled “—Employment Agreement and Severance and Change in Control Benefits –Severance Benefits.”

Mr. Newell’s Employment Offer Letter and Separation and Transition Agreement

Mr. Newell was party to an offer letter with us dated December 29, 2008, pursuant to which he served as our Chief Executive Officer. The terms and conditions of his offer letter provided for an annual base salary, and eligibility for an annual bonus, health insurance and other benefits, all subject to adjustment from time to time. Mr. Newell was an at-will employee and in 2024 he participated in the Severance Plan described above in the section entitled “—Employment Agreement and Severance and Change in Control Benefits –Severance Benefits.”

On March 13, 2025, we and Mr. Newell entered into a Separation Agreement (the “Newell Separation and Transition Agreement”) following the mutual agreement between us and Mr. Newell regarding transition of leadership of the Company and his departure from his then-current positions with the Company. Pursuant to the Newell Separation and Transition Agreement, Mr. Newell ceased his role as the Company’s President and CEO and resigned as a director of the Board, effective March 13, 2025 (the “Newell Separation Date”). In addition, pursuant to the Newell Separation and Transition Agreement, Mr. Newell will continue to provide services to the Company, including reasonable transition services or such other services as we may request, through and until May 1, 2025.

In connection with Mr. Newell’s execution of a general release and waiver of claims and the terms of the Newell Separation and Transition Agreement, Mr. Newell is entitled to receive the following benefits: (i) two cash payments totaling the gross amount of $1,066,500.00, equal to 150% of his annual salary, with the first payment paid in 2025 and the second payment paid on January 15, 2026; (ii) eighteen months of accelerated vesting on all equity awards under our 2018 Equity Incentive Plan (the “Plan”), (iii) a lump sum payment reflecting Mr. Newell’s bonus opportunity for the 2025 fiscal year on a pro-rated basis, based on our actual percentage achievement of against our 2025 corporate goals; (iv) and coverage under the Consolidated Omnibus Budget Reconciliation Act of 1985, as amended (“Cobra”) paid for by us for up to 18 months beginning June 1, 2025.

Ms. Chung’s Employment Offer Letter and Amended Offer Letter

Ms. Chung was party to an offer letter with us dated May 23, 2021 pursuant to which she served as our Chief Commercial Offier and subsequently as our President and Chief Operating Officer. The terms and conditions of her offer letter provided for an annual base salary, and eligibility for an annual bonus, health insurance and other benefits, including a four-year monthly housing and relocation allowance equal to $8,500 a month for her first two years of service and $6,500 for her third and fourth year of service, all subject to adjustment from time to time. Ms. Chung is an at-will employee. Ms. Chung participates in the Severance Plan described above in the section entitled “—Employment Agreement and Severance and Change in Control Benefits –Severance Benefits.”

Effective as of the Newell Separation Date, the Board appointed Ms. Chung to succeed Mr. Newell as Chief Executive Officer. In connection with Ms. Chung’s appointment as Chief Executive Officer, we entered into an amended offer letter with Ms. Chung (the “Amended Chung Offer Letter”). Pursuant to the Amended Chung Offer Letter, Ms. Chung will (i) receive a base salary of $675,000, (ii) be eligible to earn a target bonus of 60% of her base salary and (iii) be granted an award of 620,000 stock options and an award of 310,000 restricted stock units, both awards to be granted at the time of our annual 2025 refresh equity grants. Ms. Chung will continue to be a participant in the Severance Plan, now as a Tier 1 Participant as defined in the Severance Plan.

Mr. Albini’s Employment Offer Letter and Separation and Transition Agreement

Mr. Alibini was a party to an offer letter with us dated December 11, 2012 pursuant to which he served as our Chief Financial Officer. The terms and conditions of his offer letter provided for an annual base salary, and eligibility for an annual bonus, health insurance and other benefits, all subject to adjustment from time to time. Mr. Albini is an at-will employee. The offer letters for Mr. Albini also included certain severance protections, which severance protections were superseded by the Severance Plan described above in the section entitled “—Employment Agreement and Severance and Change in Control Benefits –Severance Benefits.”

On March 13, 2025, we and Mr. Albini entered into a Separation and Transition Services Agreement (the “Albini Separation and Transition Services Agreement”) following the mutual agreement between the Board and Mr. Albini regarding his transition from his current position with the Company, effective as of May 15, 2025 (the “Albini Transition Date”).

In connection with Mr. Albini’s execution of a general release and waiver of claims and the terms of the Albini Separation and Transition Services Agreement, Mr. Albini is entitled to receive the following benefits: (i) two cash payments totaling the gross amount of $629,375.40, equal to 125% of his annual salary, with the first payment paid in 2025 and the second payment paid on

January 15, 2026; (ii) fifteen months of accelerated vesting on all equity awards under the Plan, (iii) a lump sum payment reflecting Mr. Albini’s bonus opportunity for the 2025 fiscal year on a pro-rated basis, based on our actual percentage achievement against our 2025 corporate goals and (iv) and coverage under Cobra paid for by us for up to 15 months beginning June 1, 2025.

2024 Outstanding Equity Awards at Fiscal Year-End Table

The following table presents, for each of our named executive officers, information regarding outstanding stock options and restricted stock units held as of December 31, 2024.