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:

Harpoon Therapeutics, Inc.

(Name of Registrant as Specified In Its Charter)

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

Payment of Filing Fee (Check the appropriate box)all boxes that apply):

March 24, 2021April 27, 2023

Dear Stockholder:

You are cordially invited to attend the 20212023 Annual Meeting of Stockholders (the “Annual Meeting”) of Harpoon Therapeutics, Inc., a Delaware corporation (“Harpoon”). The meeting will be held virtually via a live audio webcast at www.virtualshareholdermeeting.com/HARP2021HARP2023 on Tuesday, May 4, 2021Thursday, June 22, 2023 at 9:008:30 a.m. Pacific Time.

Details regarding admission to the Annual Meeting and the business to be conducted at the Annual Meeting are described in the accompanying Notice of 20212023 Annual Meeting of Stockholders and proxy statement.Proxy Statement.

We have elected to provide access to our proxy materials over the Internet under the U.S. Securities and Exchange Commission’s “notice and access” rules. As a result, we are mailing to our stockholders a notice instead of paper copies of this proxy statementProxy Statement and our 20202022 Annual Report on Form 10-K. The notice contains instructions on how to access those documents over the Internet. The notice also contains instructions on how stockholders can receive a paper copy of our proxy materials, including this proxy statement,Proxy Statement, our 20202022 Annual Report on Form 10-K and a form of proxy card or voting instruction form. We believe that providing our proxy materials over the Internet increases the ability of our stockholders to connect with the information they need, while reducing the environmental impact and cost of our Annual Meeting.

Your vote is important. Whether or not you plan to attend the Annual Meeting online, we hope you will vote as soon as possible. You may vote over the Internet, by telephone or, if you receive a paper proxy card by mail, by completing and returning the proxy card or voting instruction form mailed to you. Please carefully review the instructions on each of your voting options described in this proxy statement,Proxy Statement, as well as in the notice you received in the mail.

On behalf of the Board of Directors and the employees of Harpoon, we thank you for your continued support.

Sincerely,

/s/ Gerald McMahonJulie Eastland

Gerald McMahonJulie Eastland

President, Chief Executive Officer, Secretary and Director

HARPOON THERAPEUTICS, INC.

131 Oyster Point Boulevard, Suite 300

South San Francisco, California 94080

(650) 443-7400

NOTICE OF 20212023 ANNUAL MEETING OF STOCKHOLDERS

By order of the Board of Directors,

/s/ Christopher WhitmoreJulie Eastland

Christopher WhitmoreJulie Eastland

Vice President, FinanceChief Executive Officer, Secretary and SecretaryDirector

South San Francisco, California

March 24, 2021April 27, 2023

TABLE OF CONTENTS

i

HARPOON THERAPEUTICS, INC.

131 Oyster Point Boulevard, Suite 300

South San Francisco, California 94080

(650) 443-7400

PROXY STATEMENT

FOR THE 20212023 ANNUAL MEETING OF STOCKHOLDERS

TO BE HELD ON MAY 4, 2021JUNE 22, 2023

AT 9:008:30 A.M. PACIFIC TIME

QUESTIONS AND ANSWERS ABOUT THESE PROXY MATERIALS AND VOTING

We are providing you with these Proxy Materials (as defined below) because the Board of Directors of Harpoon Therapeutics, Inc. (the “Board”) is soliciting your proxy to vote at the 20212023 Annual Meeting of Stockholders (the “Annual Meeting” or the “2023 Annual Meeting”) of Harpoon Therapeutics, Inc., including at any adjournments or postponements thereof, to be held virtually via a live audio webcast at www.virtualshareholdermeeting.com/HARP2021HARP2023 on Tuesday, May 4, 2021Thursday, June 22, 2023 at 9:008:30 a.m. Pacific Time. You are invited to attend the Annual Meeting to vote on the proposals described in this Proxy Statement. However, you do not need to attend the Annual Meeting to vote your shares. You may vote by proxy over the Internet, telephone or by mail, and your vote will be cast on your behalf at the Annual Meeting. To submit your proxy, simply follow the instructions in this Proxy Statement. The Proxy Materials, including this Proxy Statement and our Annual Report on Form 10-K for the year ended December 31, 2020,2022, are being made available on the Internet on or about March 24, 2021.April 27, 2023. As used in this Proxy Statement, references to “we,” “us,” “our” and the “Company” refer to Harpoon Therapeutics, Inc.

Why did I receive a Notice of Internet Availability of Proxy Materials on the internetInternet instead of a full set of Proxy Materials?

Pursuant to rules adopted by the Securities and Exchange Commission (the “SEC”), we have elected to provide access to our Proxy Materials over the Internet. Accordingly, on or about March 24, 2021,April 27, 2023, we have sent you a Notice of Internet Availability of Proxy Materials (the “Notice of Internet Availability”) because the Board is soliciting your proxy to vote at the Annual Meeting, including at any adjournments or postponements of the Annual Meeting. The Notice of 20212023 Annual Meeting of Stockholders (“Notice of Annual Meeting”), this proxy statement,Proxy Statement, the proxy card or voting instruction form, and the Annual Report on Form 10-K for the year ended December 31, 20202022 (collectively, the “Proxy Materials”) are available to stockholders on the Internet.

The Notice of Internet Availability will provide instructions as to how stockholders may access and review the Proxy Materials on the website referred to in the Notice of Internet Availability or, alternatively, how to request that a copy of the Proxy Materials, including a proxy card, be sent to them by mail or email. The Notice of Internet Availability will also provide voting instructions. Please note that, while our Proxy Materials are available at the website referenced in the Notice of Internet Availability, and our Notice of Annual Meeting, proxy statementProxy Statement and Annual Report on Form 10-K are available on our website, no other information contained on either website is incorporated by reference in or considered to be a part of this document.

We intend to mail the Notice of Internet Availability on or about March 24, 2021April 27, 2023 to all stockholders of record entitled to vote at the Annual Meeting. The Proxy Materials will be made available to stockholders on the Internet on the same date.

Will I receive any other Proxy Materials by mail?

You will not receive any additional Proxy Materials via mail unless (1) you request a printed copy of the Proxy Materials in accordance with the instructions set forth in the Notice or (2) we elect, in our discretion, to send you a proxy card and a second Notice of Internet Availability, which we may send on or after April 3, 2021.27, 2023.

When and where is the 20212023 Annual Meeting?

The meeting will be held virtually via a live audio webcast at www.virtualshareholdermeeting.com/HARP2021HARP2023 on Tuesday, May 4, 2021Thursday, June 22, 2023 at 9:008:30 a.m. Pacific Time. You will not be able to attend the 20212023 Annual Meeting in person. Any stockholder can listen to and participate in the Annual Meeting live via the Internet at www.virtualshareholdermeeting.com/HARP2021. Our Board annually considers the appropriate format of our annual meeting and this year has decided to hold a virtual annual meeting due to the COVID-19 global pandemic. In addition, weHARP2023. We intend the virtual meeting format to provide stockholders a similar level of transparency to the traditional in-person meeting format and will take steps to ensurefacilitate such an experience. Our stockholders will be afforded the same rights and opportunities to participate at the virtual 20212023 Annual Meeting as they would at an in-person annual meeting of stockholders, including the ability to vote shares electronically during the meeting and ask questions in accordance with the rules of conduct for the meeting. At the end of the meeting, we will spend up to 15 minutes answering stockholder questions that comply with the meeting rules of conduct, which will be posted on the virtual meeting web portal. If we receive substantially similar questions, we will group such questions together and provide a single response to avoid repetition.

If you attend the virtual meeting as described above, you will be deemed to be attending in person, as provided by Delaware law.

The 20212023 Annual Meeting webcast will begin promptly at 9:008:30 a.m. Pacific Time. We encourage you to access the meeting webcast prior to the start time. Online check-in will begin, and stockholders may begin submitting written questions, at 8:4515 a.m., Pacific Time, and you should allow ample time for the check-in procedures.

How do I attend the 20212023 Annual Meeting?

You will need the 16-digit control number included on your Notice of Internet Availability or your proxy card or voting instruction form (if you received a printed copy of the proxy materials)Proxy Materials) or included in the email to you if you received the proxy materialsProxy Materials by email in order to be able to vote your shares or submit questions during the 20212023 Annual Meeting. Beneficial owners who do not have a control number may gain access to the meeting by logging into their broker, brokerage firm, bank, or other nominee’s website and selecting the shareholder communications mailbox to link through to the annual meeting; instructions should also be provided on the voting instruction cardform provided by your broker, bank, or other nominee. Instructions on how to connect to the Annual Meeting and participate via the Internet, including how to demonstrate proof of stock ownership, are posted at www.virtualshareholdermeeting.com/HARP2021.HARP2023. If you do not have your 16-digit control number, you will be able to access and listen to the 20212023 Annual Meeting but you will not be able to vote your shares or submit questions during the Annual Meeting.

We will have technicians ready to assist you with any technical difficulties you may have accessing the virtual meeting or submitting questions. If you encounter any difficulties accessing the virtual meeting during the check-in or meeting time, please call the technical support number that will be posted on the virtual meeting web portal.

When is the record date for the Annual Meeting?

The Board has fixed the record date for the Annual Meeting as of the close of business on March 10, 2021.April 25, 2023.

Who can vote at the Annual Meeting?

Only stockholders of record at the close of business on March 10, 2021April 25, 2023 will be entitled to vote at the Annual Meeting. On this record date, there were of 32,410,78937,595,787 shares of common stock outstanding and entitled to vote.

Stockholder of Record: Shares Registered in Your Name

If on March 10, 2021,April 25, 2023, your shares were registered directly in your name with our transfer agent, Computershare Trust Company, N.A., then you are a stockholder of record. As a stockholder of record, you may vote online at the meeting, vote by proxy over the telephone or through the internet,Internet, or vote by proxy using a proxy card that you may request or that we may elect to deliver at a later time. Whether or not you plan to attend the meeting,Annual Meeting, we urge you to vote by proxy to ensure your vote is counted.

Beneficial Owner: Shares Registered in the Name of a Broker, Bank or Similar Organization

If on March 10, 2021,April 25, 2023, your shares were held, not in your name but rather in an account at a brokerage firm, bank, dealer or other similar organization, then you are the beneficial owner of shares held in “street name” and the Notice of Internet Availability is being forwarded to you by that organization. The organization holding your account is considered to be the stockholder of record for purposes of voting at the Annual Meeting. As a beneficial owner, you have the right to direct your broker or other agent regarding how to vote the shares in your account. You are also invited to attend the Annual Meeting.

What am I voting on?

At the 20212023 Annual Meeting, there are twothree matters scheduled for a vote:

In addition, you will also be asked to transact such other business, if any, as may properly come before the 20212023 Annual Meeting or any adjournment or postponement thereof.

What if another matter is properly brought before the meeting?

The Board knows of no other matters that will be presented for consideration at the Annual Meeting. If any other matters are properly brought before the meeting, the proxies will vote as recommended by the Board or, if no recommendation is given, will vote on those matters in accordance with their best judgment.

How do I vote?

For the election of directors (Proposal 1), you may either vote “For” all nominees to the Board or you may “Withhold” your vote for any nominee you specify. For the reverse stock split (Proposal 2) and the ratification of the selection of our independent registered public accounting firm (Proposal 2)3), you may vote “For” or “Against” or abstain from voting.

ShareholdersStockholders of Record: Shares Registered in Your Name

If you are a stockholder of record and your shares are registered directly in your name, you may vote:

Before the Meeting. To vote through the internetInternet before the meeting, go to www.proxyvote.com to complete an electronic proxy card. You will be asked to provide the company number and control number from the Notice of Internet Availability. Your vote must be received by 11:59 p.m., Eastern time on May 3, 2021June 21, 2023 to be counted.

During the Annual Meeting. Attend the 20212023 Annual Meeting by visiting www.virtualshareholdermeeting.com/HARP2021HARP2023 and follow the instructions posted there. Please have your control number from the Notice of Internet Availability to join the 20212023 Annual Meeting.

If your shares of common stock are held in street name (i.e., held for your account by a broker, bank or other nominee), you should have received a notice containing voting instructions from that organization rather than from us. You should follow the instructions in the notice to ensure your vote is counted. To vote at the 20212023 Annual Meeting, attend the 20212023 Annual Meeting by visiting www.virtualshareholdermeeting.com/HARP2021HARP2023 and follow the instructions posted there. Please have your 16-digit control number to join the 20212023 Annual Meeting.

How many votes do I have?

On each matter to be voted upon, you have one vote for each share of common stock you own as of March 10, 2021.April 25, 2023.

What are the Board’s recommendations on how to vote my shares?

The Board recommends a vote:

Who pays the cost for soliciting proxies?

We will pay the entire cost of soliciting proxies. In addition to these Proxy Materials, our directors and employees may also solicit proxies in person, by telephone, or by other means of communication. Directors and employees will not be paid any additional compensation for soliciting proxies. We will also reimburse brokers, banks, custodians, other nominees and fiduciaries for forwarding these materials to their principals to obtain the authorization for the execution of proxies.

If I am a stockholder of record and I do not vote, or if I return a proxy card or otherwise vote without giving specific voting instructions, what happens?

If you are a stockholder of record and do not vote by completing your proxy card, by telephone, through the Internet or by attending the Annual Meeting online, your shares will not be voted. If you return a signed and

Your last vote, whether prior to or at the Annual Meeting, is the vote that we will count.

Beneficial Owner: Shares Registered in the Name of a Broker, Bank or Similar Organization

If your shares are held in street name, you must contact your broker or nominee for instructions as to how to change your vote.

What if I return a proxy card but do not make specific choices?

If you return a signed and dated proxy card without marking any voting selections, your shares will be voted “For” the election of each nominee for director, “For” the reverse stock split, and “For” the ratification of the selection of Ernst & Young LLP as our independent registered public accounting firm for the year ending December 31, 2021.2023.

How can I find out the results of the voting at the Annual Meeting?

We will announce preliminary voting results at our Annual Meeting. We will publish final voting results in a Current Report on Form 8-K that we expect to file no later than May 10, 2021.within four business days after the Annual Meeting. If final voting results are not available by May 10, 2021,to us in time to file a Form 8-K within four business days after the Annual Meeting, we will disclose the preliminary results in the Current Report on Form 8-K and, within four business days after the final voting results are known to us, file an amended Current Report on Form 8-K to disclose the final voting results.

When are stockholder proposals due for the 20222024 Annual Meeting of Stockholders?

If you wish to submit proposals for inclusion in our proxy statementProxy Statement for the 20222024 Annual Meeting of Stockholders (the “2022“2024 Annual Meeting”), we must receive them on or before November 24, 2021.December 30, 2023. Nothing in

PROPOSAL 1: ELECTION OF DIRECTORS

General

Our amended and restated certificateCertificate of incorporationIncorporation provides for a classified Board consisting of three classes of directors. Class II and Class III each consist of three directors and Class I consists of four directors. Each class serves for a three-year term. Vacancies on our Board may be filled only by persons elected by a majority of the remaining directors. A director elected by our Board to fill a vacancy in a class, including vacancies created by an increase in the number of directors, shall serve for the remainder of the full term of that class and until the director’s successor is duly elected and qualified.

Our Board is currently composed of ten directors. Theredirectors, and there are threefour directors whose term of office expires in 2021. Upon the recommendation of the Nominating2023: Mark Chin, Andrew Robbins, Alan Colowick and Corporate Governance Committee, our Board hasJoanne Viney. Drs. Colowick and Viney have not been nominated the three individuals listed in the table below for election as directors atreelection and, accordingly, their terms will expire immediately prior to the Annual Meeting. Dr. Drachman and Mr. Hunt were eachEffective as of the date of the Annual Meeting, the size of the Board will be reduced to eight directors. Each of the nominees listed below is currently a director who was previously elected to our Board by our stockholders. Dr. Bailes was appointed to our Board in March 2020 by our directors to fill a newly created vacancy. Dr. Bailes was not selected by the Board to serve as a director pursuant to any arrangement or understanding with any person.stockholders at our annual meeting of stockholders in 2020. If the nominees listed below are elected, they will each hold office until the annual meeting of stockholders in 20232026 and until each of their successors has been duly elected and qualified or, if sooner, until the director’s death, resignation or removal. All nominees are currently serving on our Board and have consented to being named in this proxy statementProxy Statement and to serve if elected. It is our policy to encourage directors and nominees for director to attend the Annual Meeting.

The brief biographies below include information, as of the date of this proxy statement,Proxy Statement, regarding the specific and particular experience, qualifications, attributes or skills that led the Nominating and Corporate Governance Committee to believe that each director or nominee should serve on the Board. There are no family relationships among any of our executive officers or directors.

Class III Directors—Nominees for Election at the Annual Meeting

Jonathan Drachman, M.D.Mark Chin has served as a member of our Board since September 2018. SinceMay 2017. Mr. Chin has served as a managing director at Arix Bioscience, a biotech-focused venture capital firm, since July 2021 and was previously an investment director there from July 2016 to April 2020. Prior to Arix Bioscience, he was a principal at Longitude Capital, a healthcare venture capital firm, from January 2019, Dr. Drachman has been CEO2012 to August 2018, where he focused on investments in both private and President of Neoleukin Therapeutics, Inc.,public biotechnology and medical technology companies. Prior to Longitude Capital, Mr. Chin was a consultant at the Boston Consulting Group, a global management consulting firm, from January 2011 to January 2012, where he managed strategy and corporate development projects for pharmaceutical and biotechnology companies, and prior to Boston Consulting Group, he worked in corporate development at Gilead Sciences, a biotechnology company, that uses computational algorithms to design de novo proteins for the treatment of cancer, inflammation and autoimmune diseases. Previously, Dr. Drachman served as the Chief Medical Officer and Executive Vice President, Research and Development of Seattle Genetics,in market planning at Genentech, a biotechnology company. Mr. Chin currently serves as a member of the boards of directors of public pharmaceutical companies Disc Medicine, Inc. (Nasdaq: IRON), Imara Inc. (Nasdaq: IMRA) and Iterum Therapeutics (Nasdaq: ITRM). He served on the board of directors of Pyxis Oncology (Nasdaq: PYSX), a public pharmaceutical company, from October 2013 until May 2018, after serving as their Senior Vice President, ResearchJuly 2021 to April 2022. Mr. Chin holds a B.S. in Management Science from the University of California at San Diego, an M.S. in Biotechnology from the University of Pennsylvania and Translational Medicine and various other positions of increasing authority since November 2004. Prior to Seattle Genetics, Dr. Drachman was Associate Professor in the Hematology Division, Department of Medicinean M.B.A. from The Wharton School at the University of Washington in Seattle, where he remains a Clinical Professor of Medicine. He also served as Senior Investigator in the Division of Research and Education and Medical Director of the Umbilical Cord Blood Program at the Puget Sound Blood Center. Dr. Drachman currently serves on the boards of two additional public companies: Calithera Biosciences, Inc. (Nasdaq: CALA) and Neoleukin Therapeutics, Inc. (Nasdaq: NLTX). Dr. Drachman holds a B.A. in Biochemistry from Harvard University and an M.D. from Harvard Medical School. He completed his residency in Internal Medicine and fellowship in Medical Oncology at the University of Washington School of Medicine.Pennsylvania. Our Board believes that Dr. Drachman’s scientificMr. Chin’s expertise and professional expertiseexperience in the life sciences industry, experience as a director of other public companies in our industry and his educational background provide him with the qualifications and skills to serve on our Board.

Andrew Robbins has served as a member of our Board since March 2020. Since October 2020, Mr. Robbins has served as CEO and President, and as a member of the board of directors of, Cogent Biosciences, Inc. (Nasdaq: COGT), a biotechnology company. Mr. Robbins served as Chief Operating Officer at Array BioPharma Inc., a pharmaceutical company, from March 2015 through its acquisition by Pfizer Inc., a pharmaceutical company, in July 2019, after serving as its Senior Vice President, Commercial Operations from July 2012 to March 2015. From January 2007 to July 2012, Mr. Robbins held management positions at Hospira, Inc., a pharmaceutical and medical device company, including General Manager and Vice President of the U.S. Alternate Site business unit and Vice President of Corporate Development. Prior to Hospira, Mr. Robbins held commercial and leadership positions within Pfizer’s oncology unit. Mr. Robbins previously served on the board of directors of Turmeric Acquisition Corp. (Nasdaq: TMPM), a special purpose acquisition company, from October 2020 until December 2022. Mr. Robbins holds a B.A. from Swarthmore College and an M.B.A. from the Kellogg School of Management at Northwestern University. Our Board believes that Mr. Robbins’ expertise and experience in the life sciences industry provide him with the qualifications and skills to serve on our Board.

Vote Required

Directors are elected by a plurality of the votes of the holders of shares present or represented by proxy and entitled to vote at the Annual Meeting on the election of directors. Accordingly, the two nominees receiving the highest number of affirmative votes will be elected. You may not vote your shares cumulatively for the election of directors. Shares represented by executed proxies will be voted, if authority to do so is not withheld, for the election of the two nominees named above. If any nominee becomes unavailable for election as a result of an unexpected occurrence, your shares will be voted for the election of a substitute nominee proposed by our Board. The Board has no reason to believe that any of the nominees would prove unable to serve if elected. There are no arrangements or understandings between us and any director, or nominee for directorship, pursuant to which such person was selected as a director or nominee.

Our Recommendation

THE BOARD UNANIMOUSLY RECOMMENDS A VOTE FOR EACH OF THE NAMED DIRECTOR NOMINEES.

Information About Our Continuing Directors

Set forth below are the names, ages and length of service of the remaining members of our Board whose terms continue beyond the Annual Meeting.

The principal occupation, business experience and education of each continuing director are set forth below.

Class II Directors—Continuing in Office until the 2024 Annual Meeting of Stockholders

Joseph Bailes, M.D. has served as a member of our Board since March 2020. Dr. Bailes is a medical oncologist with experience in clinical practice, legislation, public policy and advocacy and has served as an

industry consultant for the past decade, including as Senior Advisor to the American Society of Clinical Oncology (ASCO) Government Relations Council since 2010. In addition, Dr. Bailes previously served in various executive leadership roles at the American Society of Clinical Oncology (ASCO)ASCO until 2010, including as President, Interim Executive Vice President, Chief Executive Officer, Chair of the Clinical Research Committee and Chair of the Government Relations Council. Industry companies with which Dr. Bailes has consulted include Kite Pharma, Inc. (a subsidiary of Gilead Sciences, Inc.), Eli Lilly and Company (NYSE: LLY), G1 Therapeutics, Inc. (Nasdaq: GTHX), and Telik, Inc. In addition, Dr. Bailes has many years of oncology practice experience in the private sector as a former partner at Texas Oncology, P.A., an oncology practice group, and as a founding member of, and the President of Research overseeing clinical trials and drug development activities at Physician Reliance Network, LLC, a health care company and corporate predecessor of US Oncology, Inc., where he then served as Executive Vice President of Clinical Affairs. Dr. Bailes holds a B.A. from the University of Texas at Austin and an M.D. from the University of Texas Southwestern Medical School, Dallas. Dr. Bailes completed his internship and residency at the Parkland Memorial Hospital in Dallas and his Medical Oncology/Hematology Fellowship at the University of Texas Health Science Center in San Antonio, where he also served as a Clinical Assistant Professor. Our Board believes that Dr. Bailes’ medical expertise and experience in the biopharmaceutical industry provide him with the qualifications and skills to serve on our Board.

RonJonathan Drachman, M.D. has served as a member of our Board since September 2018. From January 2019 through March 2023, Dr. Drachman served as Chief Executive Officer and President of Neoleukin Therapeutics, Inc. (Nasdaq: NLTX), a biotechnology company that uses computational algorithms to design de novo proteins for the treatment of cancer, inflammation and autoimmune diseases. He was also on Neoleukin’s board of directors from August 2019 through March 2023. Previously, Dr. Drachman served as the Chief Medical Officer and Executive Vice President, Research and Development of Seattle Genetics (Nasdaq: SGEN), a biotechnology company, from October 2013 until May 2018, after serving as their Senior Vice President, Research and Translational Medicine and various other positions of increasing authority since November 2004. Prior to Seattle Genetics, Dr. Drachman was Associate Professor in the Hematology Division, Department of Medicine at the University of Washington in Seattle, where he remains a Clinical Professor of Medicine. He also served as Senior Investigator in the Division of Research and Education and Medical Director of the Umbilical Cord Blood Program at the Puget Sound Blood Center. Dr. Drachman was on the board of directors of Calithera Biosciences, Inc. (Nasdaq: CALA) from December 2013 to June 2022. Dr. Drachman holds a B.A. in Biochemistry from Harvard University and an M.D. from Harvard Medical School. He completed his residency in Internal Medicine and fellowship in Medical Oncology at the University of Washington School of Medicine. Our Board believes that Dr. Drachman’s scientific and professional expertise and his educational background provide him with the qualifications and skills to serve on our Board.

Ronald Hunt has served as a member of our Board since May 2017 and aswas the Chair of our Chair sinceBoard from April 2020. 2020 to October 2021. Mr. Hunt co-founded and has served as a Managing Director of New Leaf Venture Partners, a venture capital fund focused on biopharmaceuticals and other healthcare technologies, since 2005. From 1998 to 2005, Mr. Hunt was a partner at the Sprout Group, an institutional venture capital firm. Prior to Sprout, Mr. Hunt was a consultant within the pharmaceutical industry practice at Coopers & Lybrand Consulting, a consulting firm, and a consultant withat The Health Care Group (a division of the Interpublic Group), a strategy consulting firm and a consultant.firm. Prior to the Health Care Group, Mr. Hunt held a number of roles in the sales and marketing divisions of Johnson & Johnson (NYSE: JNJ) and SmithKline Beecham Pharmaceuticals, both pharmaceutical companies. Mr. Hunt currently serves on the boardboards of directors of public companycompanies Iterum Therapeutics plc (Nasdaq: ITRM) and Rallybio Corporation (Nasdaq: RLYB), and has previously served as a director for Neuronetics, Inc. (Nasdaq: STIM) and Durata Therapeutics, Inc. (Nasdaq: DRTX). Mr. Hunt holds a B.S. from Cornell University and an M.B.A. from The Wharton School at the University of Pennsylvania. Our Board believes that Mr. Hunt’s expertise and experience in the venture capital and pharmaceutical industry, and his educational background provide him with the qualifications and skills to serve on our Board.

Vote Required

Directors are elected by a plurality of the votes of the holders of shares present or represented by proxy and entitled to vote at the Annual Meeting on the election of directors. Accordingly, the three nominees receiving the highest number of affirmative votes will be elected. You may not vote your shares cumulatively for the election of directors. Shares represented by executed proxies will be voted, if authority to do so is not withheld, for the election of the three nominees named above. If any nominee becomes unavailable for election as a result of an unexpected occurrence, your shares will be voted for the election of a substitute nominee proposed by our Board. The Board has no reason to believe that any of the nominees would prove unable to serve if elected. There are no arrangements or understandings between us and any director, or nominee for directorship, pursuant to which such person was selected as a director or nominee.

Our Recommendation

THE BOARD UNANIMOUSLY RECOMMENDS A VOTE FOR EACH OF THE NAMED DIRECTOR NOMINEES.

Information About Our Continuing Directors

Set forth below are the names, ages and length of service of the remaining members of our Board whose terms continue beyond the Annual Meeting.

The principal occupation, business experience and education of each continuing director are set forth below. Unless otherwise indicated, principal occupations shown for each director have extended for five or more years.

Class III Directors—Continuing in Office until the 20222025 Annual Meeting of Stockholders

Gerald McMahon, Ph.D.Julie Eastlandhas served as our President, Chief Executive Officer and a member of our Board since December 2016. From May 2012 to its acquisition by Celldex Therapeutics, Inc. in November 2016, Dr. McMahon was the President and Chief Executive Officer of Kolltan Pharmaceuticals, Inc., an oncology biologics company where he played a key role in the development of the business. From October 2010 to May 2012, he served as Senior Vice President of Oncology at MedImmune LLC, a subsidiary of AstraZeneca. Prior to MedImmune, he served as the Chairman and Chief Executive Officer of NeoRx Corporation, a pharmaceutical company, and as a venture partner at Bay City Capital, a venture capital firm, and in executive leadership roles at Poniard Pharmaceuticals and SUGEN (acquired by Pfizer), both biopharmaceutical companies, where he was a key player in the development and commercialization of innovative oncology drugs. Dr. McMahon earned a B.S. in Biology and a Ph.D. in Biochemistry from the Rensselaer Polytechnic Institute. He held an academic appointment at the Yale Comprehensive Cancer Center at Yale University, and previously held post-graduate appointments at Tufts University School of Medicine, department of hematology and oncology at the New England Medical Center, and the Massachusetts Institute of Technology. Our Board believes that Dr. McMahon’s expertise and experience as our President and Chief Executive Officer his depthsince November 2021 and expertise in the life sciences industry, his experience in leadership, scientific innovation and creative deal-making and financings and his educational background provide him with the qualifications and skills to serve on our Board.

Julie Eastland has served as a member of our Board since October 2018. SinceBetween October 2020 and November 2021, Ms. Eastland has served as the Chief Operating Officer and Chief Financial Officer of ReCode Therapeutics, Inc., a biopharmaceutical company. Prior to ReCode Therapeutics, Ms. Eastland has served as the Chief Financial and Business Officer of Rainier Therapeutics, Inc., a biotechnology company, from August 2018 to January 2020. Prior to Rainier Therapeutics, Ms. Eastland served as Chief Business Officer and Chief Financial Officer for Cascadian Therapeutics, Inc., a biotechnology company, from September 2010 through its acquisition by Seattle Genetics in March 2018. Prior to Cascadian, Ms. Eastland served as the Chief Financial Officer and Vice President of Finance and Administration for VLST Corporation, a biotechnology company, from January 2006 to September 2010. Prior to VLST Corporation, Ms. Eastland was the Vice President of Strategic Planning at Dendreon Corporation, a biotechnology company, from October 2000 to October 2005. Prior to Dendreon, Ms. Eastland was the Controller at Amgen, a biopharmaceutical company,

Class I Directors—Continuing in Office until the 2023 Annual Meeting of Stockholders

Mark ChinLauren P. Silvernail has served as a member of our Boardboard since May 2017. From July 2016 to April 2020, Mr. ChinSeptember 2022. She previously served as an investment director at Arix Bioscience, a biotechnology-focused venture capital firm. Prior to Arix Bioscience, he was a principal at Longitude Capital, a healthcare venture capital firm, from January 2012 to August 2018, where he focused on investments in both privateChief Financial Officer and public biotechnology and medical technology companies. Prior to Longitude Capital, Mr. Chin was a consultant at the Boston Consulting Group, a global management consulting firm, from January 2011 to January 2012, where he managed strategy and corporate development projects for pharmaceutical and biotechnology companies, and prior to Boston Consulting Group, he worked in corporate development at Gilead Sciences, a biotechnology company, and in market planning at Genentech, a biotechnology company. Mr. Chin currently serves as a member of the Board of Directors of public pharmaceutical companies Imara Inc. (Nasdaq: IMRA) and Iterum Therapeutics (Nasdaq: ITRM). Mr. Chin holds a B.S. in Management Science from the University of California at San Diego, an M.S. in Biotechnology from the University of Pennsylvania and an M.B.A. from The Wharton School at the University of Pennsylvania. Our Board believes that Mr. Chin’s expertise and experience in the life sciences industry, experience as a director of other companies in our industry and his educational background provide him with the qualifications and skills to serve on our Board.     

Alan Colowick, M.D. has served as a member of our Board since March 2021. From May 2017 to January 2021, Dr. Colowick served as a Partner at Sofinnova Investment, Inc., a clinical stage life sciences venture capital firm. From February 2010 to April 2017, Dr. Colowick held various positions, including Executive Vice President, at Celgene Corporation, a pharmaceutical company. From February 2008Corporate Development of Evolus, Inc. from May 2018 through May 2022. Prior to January 2010, Dr. Colowickthat time, Ms. Silvernail served as the Chief ExecutiveFinancial Officer and Chief Business Officer of Gloucester PharmaceuticalsRevance Therapeutics, Inc., an early stage cancer pharmaceutical company, until its acquisition by Celgene Corporation in January 2010. From October 2006 to February 2008, Dr. Colowick served as President, Oncology at Geron Corporation, a pharmaceutical company.

INFORMATION REGARDING THE BOARD AND CORPORATE GOVERNANCE

Board Independence

As required under The Nasdaq Stock Market (“Nasdaq”) listing standards, a majority of the members of a listed company’s Board must qualify as “independent,” as affirmatively determined by the Board. The Board consults with the Company’sour counsel to ensure that the Board’s determinations are consistent with relevant securities and other laws and regulations regarding the definition of “independent,” including those set forth in pertinent listing standards of Nasdaq, as in effect from time to time.

Consistent with these considerations, after review of all relevant identified transactions or relationships between each director, or any of his or her family members, and the Company, itsour company, our senior management and itsour independent registered public accounting firm, our Board has affirmatively determined that all of our directors, except Dr. McMahon,Ms. Eastland, by virtue of hisher position as President and Chief Executive Officer, are independent directors within the meaning of the applicable Nasdaq listing standards. In making these determinations, our Board has determined, upon the recommendation of our Nominating and Corporate Governance Committee and considered certain relationships and transactions that occurred between the Company and entities with which some of our directors are affiliated, including the affiliation of Mr. Hunt with New Leaf Biopharma Opportunities II, L.P. (“BPO-II”), as a managing director of New Leaf BPO Management II, L.L.C. (“BPO Management-II”), and Mr. Chin with Arix Bioscience Holdings Limited, as a managing director of Arix Bioscience Plc. Both BPO-II and Arix Bioscience Holdings Limited were purchasers in our private placement offering of our Series A redeemable preferred stock and warrants to purchase shares of our common stock. The sole general partner of BPO-II is New Leaf BPO Associates II, L.P. (“NLBA-II”). The sole general partner of NLBA-II is BPO Management-II. Our Board has determined that none of these directors or nominees for director had a material or other disqualifying relationship with the Company. The Board also determined that each member of our Audit, Compensation and Nominating and Corporate Governance Committees satisfies the independence standards for such committees established by the SEC and the Nasdaq listing standards, as applicable.

Leadership Structure and Risk Oversight

The Board has an independent chair (the “Board Chair”), Mr. Hunt,Myers, who has authority, among other things, to call and preside over Board meetings, including meetings of the independent directors, to set meeting agendas and to determine materials to be distributed to the Board. Accordingly, theThe Board Chair has substantial ability to shape the work of the Board. The Company believesWe believe that separation of the positions of Board Chair and Chief Executive Officer reinforces the independence of the Board in its oversight of the business and affairs of the Company. In addition, the Company believeswe believe that having an independent Board Chair creates an environment that is more conducive to objective evaluation and oversight of management’s performance, increasing management accountability and improving the ability of the Board to monitor whether management’s actions are in the best interests of the Companyus and itsour stockholders. As a result, the Company believeswe believe that having an independent Board Chair can enhance the effectiveness of the Board as a whole.

One of the Board’s key functions is informed oversight of our risk management process. The Board does not have a standing risk management committee, but rather administers this oversight function directly through the Board as a whole, as well as through various Board standing committees that address risks inherent in their respective areas of oversight. In particular, our Board is responsible for monitoring and assessing strategic risk exposure, including a determination of the nature and level of risk appropriate for the Company. Our Audit Committee has the responsibility to consider and discuss with management and the independent registered public accounting firm, as appropriate, the Company’sour guidelines and policies with respect to financial risk management and financial risk assessment, including the Company’sour major financial risk exposures and the steps taken by management to monitor and control these exposures. In addition, the Audit Committee considers management risks relating to data privacy, technology and information security, including cyber security, and back-up of information systems and the steps the Company haswe have taken to monitor and control such exposures as well as overseeing the performance of our internal audit function, as applicable.exposures. Our Compensation Committee assesses and monitors whether any of our compensation policies and programs has the potential to encourage excessive risk-taking, including risks related to executive compensation and overall compensation and benefit strategies, plans, arrangements, practices and policies. Our Nominating and Corporate Governance Committee monitors the

effectiveness of our corporate governance guidelines, including whether they are successful in preventing illegal or improper liability-creating conduct. The Nominating and Corporate Governance Committee also oversees and reviews with management the Company’sour major legal compliance risk exposures and the steps management has

Below is a description of each committeethe committees of the Board. Each of the committeesAudit, Compensation, and Nominating and Corporate Governance Committees has authority to engage legal counsel or other experts or consultants, as it deems appropriate to carry out its responsibilities. The Board has determined that each member of each committee meets the applicable Nasdaq rules and regulations regarding “independence” and each member is free of any relationship that would impair his or her individual exercise of independent judgment with regard to the Company. Each of the committeesAudit, Compensation, and Nominating and Corporate Governance Committees operates pursuant to a written charter and each committee reviews and assesses the adequacy of its charter and submits its charter to the Board for approval. The charters are all available in the “Investors/News–Corporate“Corporate Governance” section of our website, www.harpoontx.com. The inclusion of our website address here and elsewhere in this proxy statementProxy Statement does not include or incorporate by reference the information on our website into this proxy statement.Proxy Statement.

Audit Committee

The Audit Committee of the Board was established by the Board in accordance with Section 3(a)(58)(A) of the Exchange Act to oversee our corporate accounting and financial reporting processes and audits of its financial statements. For this purpose, the Audit Committee performs several functions, including, among other things:

Compensation Committee

The primary purpose of our Compensation Committee is to discharge the responsibilities of our Board in overseeing our compensation policies, plans and programs and to review and determine the compensation to be

During the past fiscal year, after taking into consideration the six factors prescribed by the SEC and Nasdaq, the Compensation Committee engaged Compensia, Inc. (the “Consultant”), a compensation consulting firm, as a compensation consultant. The Compensation Committee has assessed the Consultant’s independence and determined that the Consultant had no conflicts of interest in connection with its provisions of services to the Compensation Committee. Specifically, the Compensation Committee engaged the Consultant to provide market data, peer group analysis and conduct an executive compensation assessment analyzing the current cash and equity compensation of our executive officers and directors against compensation for similarly situated executives at our peer group. Our management did not have the ability to direct the Consultant’s work.

Historically, our Compensation Committee has made most of the significant adjustments to annual compensation, determined bonus and equity awards and established new performance objectives at one or more meetings held during the first quarter of the year. However, our Compensation Committee also considers matters related to individual compensation, such as compensation for new executive hires, as well as high-level strategic issues, such as the efficacy of our compensation strategy, potential modifications to that strategy and new trends, plans or approaches to compensation, at various meetings throughout the year. Generally, the Compensation Committee’s process comprises two related elements: the determination of compensation levels and the establishment of performance objectives for the current year. For executives other than the Chief Executive Officer, our Compensation Committee solicits and considers evaluations and recommendations submitted to the Compensation Committee by the Chief Executive Officer. In the case of the Chief Executive Officer, the evaluation of his or her performance is conducted by the Compensation Committee, which determines any adjustments to his or her compensation as well as awards to be granted. For all executives and directors as part of its deliberations, the Compensation Committee may review and consider, as appropriate, materials such as executive and director stock ownership information, company stock performance data, analyses of historical executive compensation levels and current Company-wide compensation levels, including analyses of executive and director compensation paid at a peer group of other companies approved by our Compensation Committee.

Nominating and Corporate Governance Committee

Specific responsibilities of our Nominating and Corporate Governance Committee include:

During 2022, Mr. Myers and Drs. Bailes and Drachman and Ms. Eastland serveserved as the current members of the Nominating and Corporate Governance Committee, with Mr. Myers serving as Chair of the Committee. Mr. Chin served as a member of the Nominating and Corporate Governance Committee until April 2020, at which point he wasOur Board has

replaced by Dr. Bailes. Our Board has determined that each member of our Nominating and Corporate Governance committeeCommittee is independent under the applicable listing standards of Nasdaq. The Nominating and Corporate Governance Committee met fivethree times during the fiscal year ended December 31, 2020.2022.

The Nominating and Corporate Governance Committee believes that candidates for director should have certain minimum qualifications, including the ability to read and understand basic financial statements, understand the Company’s industry and having the highest personal integrity and ethics. The Nominating and Corporate Governance Committee also intends to consider such factors as possessing relevant expertise upon which to be able to offer advice and guidance to management, having sufficient time to devote to the affairs of the Company, demonstrated excellence in his or her field, having the ability to exercise sound business judgment and having the commitment to rigorously represent the long-term interests of our stockholders. However, the Nominating and Corporate Governance Committee retains the right to modify these qualifications from time to time, subject to Board approval. Candidates for director nominees are reviewed in the context of the current composition of the Board, the operating requirements of the Company and the long-term interests of stockholders. In conducting this assessment, the Nominating and Corporate Governance Committee typically considers diversity, age, skills and such other factors as it deems appropriate, given the current needs of the Board and the Company, to maintain a balance of knowledge, experience and capability.

In the case of incumbent directors whose terms of office are set to expire, the Nominating and Corporate Governance Committee reviews these directors’ overall service to the Company during their terms, including the number of meetings attended, level of participation, quality of performance and any other relationships, and transactions that might impair the directors’ independence.independence, and overall size of the Board given the current needs of the Company. The Committee will take into account the results of the Board’s self-evaluation, conducted annually on a group and individual basis. In the case of new director candidates, the Nominating and Corporate Governance Committee also determines whether the nominee is independent for Nasdaq purposes, which determination is based upon applicable Nasdaq listing standards, applicable SEC rules and regulations and the advice of counsel, if necessary. Generally, our Nominating and Corporate Governance Committee identifies candidates for director nominees in consultation with management, using search firms or other advisors, through the recommendations submitted by stockholders or through such other methods as the Nominating and Corporate Governance Committee deems to be helpful to identify candidates. The Nominating and Corporate Governance Committee conducts any appropriate and necessary inquiries into the backgrounds and qualifications of possible candidates after considering the function and needs of the Board. The Nominating and Corporate Governance Committee meets to discuss and consider the candidates’ qualifications and then selects a nominee for recommendation to the Board by majority vote. The Nominating and Corporate Governance Committee may gather information about the candidates through interviews, questionnaires, background checks or any other means that the Nominating and Corporate Governance Committee deems to be appropriate in the evaluation process. We have no formal policy regarding board diversity. Our Nominating and Corporate Governance Committee’s priority in selecting board members is identification of persons who will further the interests of our company through his or her established record of professional accomplishment, the ability to contribute positively to the collaborative culture among board members, and professional and personal experiences and expertise relevant to our growth strategy.

The Nominating and Corporate Governance Committee will consider director candidates recommended by stockholders. The Nominating and Corporate 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. Stockholders who wish to recommend individuals for consideration by the Nominating and Corporate Governance Committee to become nominees for election to the Board may do so by providing timely notice in writing to our Corporate Secretary at c/o Harpoon Therapeutics, Inc., 131 Oyster Point Boulevard, Suite 300, South San Francisco, California 94080. Stockholders who intend to solicit proxies in support of director nominees other than our nominees must also comply with the additional requirements of Rule 14a-19(b). To be timely, we must receive the notice not less than 90 days nor more than 120 days prior to the anniversary of the prior year’s annual meeting of stockholders; provided, however, that in

the event that no annual meetings whatmeeting was held during the preceding year or the date of the annual meeting is more than 30 days before or more than 30 days after such anniversary date, we must receive the stockholder’s notice (i) no earlier than the close of business on the 120th day prior to

The information provided under this Hedging Policy section shall not be deemed incorporated by reference into any filing under the Securities Act or the Exchange Act, except to the extent that the Company specifically incorporates this information by reference.

PROPOSAL 2: APPROVAL OF AMENDMENT TO OUR CERTIFICATE OF INCORPORATION TO EFFECT A

REVERSE STOCK SPLIT OF THE ISSUED AND OUTSTANDING COMMON STOCK

Our Board has approved, and is recommending that our stockholders approve, a proposed amendment to our Certificate of Incorporation, to effect a reverse split of the issued and outstanding shares of the common stock at a ratio of between 1-for-2 and 1-for-10, with such ratio to be determined at the sole discretion of our Board (the “Reverse Stock Split”). The form of proposed amendment to our Certificate of Incorporation to effect the Reverse Stock Split is attached as Appendix A to this proxy statement. The text of the proposed amendment is subject to revision to include such changes as may be required by the Secretary of State of the State of Delaware and as our Board deems necessary or advisable to effect the proposed amendment of the Certificate of Incorporation. If a certificate of amendment is filed with the Secretary of State of the State of Delaware, the certificate of amendment to the Certificate of Incorporation will effect the Reverse Stock Split by reducing the outstanding number of shares of the common stock by the ratio to be determined by the Board, but will not increase the par value of the common stock and will not change the number of authorized shares of the common stock. If the Board does not implement an approved Reverse Stock Split prior to the one-year anniversary of this meeting, the Board will seek stockholder approval before implementing any Reverse Stock Split after that time.

By approving Proposal 2 and the Reverse Stock Split, stockholders will approve the amendment to our Certificate of Incorporation pursuant to which any whole number of outstanding shares, between and including two and ten, would be combined into one share of common stock and authorize our Board to file certificate of amendment, as determined by our Board in the manner described herein. If approved, our Board may also elect not to effect any Reverse Stock Split and consequently not file any certificate of amendment to the Certificate of Incorporation.

Nasdaq Listing Compliance

Our common stock is listed on the Nasdaq Global Select Market under the symbol “HARP.” To maintain a listing on the Nasdaq Global Select Market, we must satisfy various listing maintenance standards established by The Nasdaq Stock Market LLC (“Nasdaq”). If we are unable to meet the Nasdaq Global Select Market requirements, our common stock will be subject to delisting.

Among other things, we are required to comply with the continued listing requirements of the Nasdaq Global Select Market, including that the common stock maintain a minimum bid price of $1.00 on the Nasdaq Global Select Market (the “Nasdaq Minimum Bid Requirement”). We do not currently satisfy this Nasdaq Minimum Bid Requirement. Assuming our stockholders approve this proposal, our Board will determine whether to effect a Reverse Stock Split in the range of between 1-for-2 and 1-for-10, inclusive, at the ratio determined by our Board to be most likely sufficient to allow us to maintain the $1.00 minimum bid price requirement.

Reasons for the Reverse Stock Split

On March 29, 2023, Nasdaq notified us that the bid price of our common stock had closed below the required $1.00 per share for 30 consecutive trading days, and, accordingly, that we did not comply with the Nasdaq Minimum Bid Requirement. We have been provided 180 calendar days by Nasdaq to regain compliance with this requirement (the “Compliance Period”), subject to a potential 180 calendar day extension, as described below. To regain compliance, the closing bid price of our common stock must be at least $1.00 per share for a minimum of ten consecutive business days within the Compliance Period.

If we do not achieve compliance with the Nasdaq Minimum Bid Requirement by September 25, 2023, the end of the Compliance Period, we may be eligible for an additional 180 calendar day period to regain compliance. To qualify, we would be required to meet the continued listing requirement for the market value of

our publicly held shares and all other Nasdaq initial listing standards, with the exception of the Nasdaq Minimum Bid Requirement, and would need to provide written notice of our intention to cure the deficiency during the second compliance period. However, if it appears to the Nasdaq staff that we will not be able to cure the deficiency, or if we do not meet the other listing standards, Nasdaq could provide notice that our common stock will be subject to delisting. In the event we receive notice that our common stock is being delisted, we would be entitled to appeal the determination to a Nasdaq Listing Qualifications Panel and request a hearing.

In addition, on March 30, 2023, we received a written notice (the “Stockholders’ Equity Notice”) from Nasdaq notifying us that our stockholders’ equity as reported in our Annual Report on Form 10-K for the year ended December 31, 2022, did not satisfy the continued listing requirement under Nasdaq Listing Rule 5450(b)(1)(A) for the Nasdaq Global Select Market, which requires that a listed company’s stockholders’ equity be at least $10.0 million. In accordance with such Stockholders’ Equity Notice, we have 45 calendar days from the date of the Stockholders’ Equity Notice to submit a plan to regain compliance with Nasdaq Listing Rule 5450(b)(1)(A), or we may choose to transfer the listing of our common stock to The Nasdaq Capital Market, if we are eligible to do so. We are in the process of reviewing potential actions and responses regarding the non-compliance set forth in the Stockholders’ Equity Notice and currently anticipate timely submitting such a plan to Nasdaq. If our plan is accepted, Nasdaq may grant an extension of up to 180 calendar days from March 30, 2023 for us to provide evidence of compliance. If the plan is not accepted or if we are not granted an extension, we will then consider actions appropriate under the circumstances, which may include applicable appeals to a Nasdaq Listing Qualifications Panel.

Our Board has considered the potential harm to us of a delisting of the common stock and has determined that, if the common stock continues to trade below $1.00 per share, the consummation of the Reverse Stock Split is the best way to maintain liquidity by achieving compliance with the Nasdaq Minimum Bid Requirement. Our Board also believes that the current low per share market price of the common stock has a negative effect on the marketability of our existing shares. Our Board believes there are several reasons for this effect. First, certain institutional investors have internal policies preventing the purchase of low-priced stocks. Second, a variety of policies and practices of broker-dealers discourage individual brokers within those firms from dealing in low-priced stocks. Third, because the brokers’ commissions on low-priced stocks generally represent a higher percentage of the stock price than commissions on higher priced stocks, the current share price of the common stock can result in individual stockholders paying transaction costs (commissions, markups or markdowns) that are a higher percentage of their total share value than would be the case if the share price of the common stock were substantially higher. This factor is also believed to limit the willingness of some institutions to purchase our common stock. Our Board anticipates that a Reverse Stock Split will result in a higher bid price for our common stock, which may help to alleviate some of these problems.

If this Proposal 2 is approved by the holders of the common stock voting together as a single class and our Board decides to implement the Reverse Stock Split, our Board will determine the ratio of the Reverse Stock Split, in the range of between 1-for-2 and 1-for-10, inclusive, as determined in the judgment of our Board to be most likely sufficient to allow us to achieve and maintain compliance with the minimum $1.00 per share requirement for listing on the Nasdaq Global Select Market for the longest period of time while retaining a sufficient number of outstanding, tradeable shares to facilitate an adequate market.

We believe that maintaining listing on the Nasdaq Stock Market (either the Nasdaq Global Select Market or Nasdaq Capital Market) will provide us with a market for the common stock that is more accessible than if the common stock were traded on the OTC Bulletin Board or in the “pink sheets” maintained by the OTC Markets Group, Inc. Such alternative markets are generally considered to be less efficient than, and not as broad as, the Nasdaq Stock Market. Among other factors, trading on the Nasdaq Stock Market increases liquidity and may potentially minimize the spread between the “bid” and “asked” prices quoted by Market Makers (as defined in Nasdaq Rule 5005). Further, a Nasdaq Stock Market listing may enhance our access to capital, increase our flexibility in responding to anticipated capital requirements and facilitate the use of our common stock in any strategic or financing transactions that we may undertake. We believe that prospective investors will view an

investment in us more favorably if our shares qualify for listing on the Nasdaq Stock Market as compared with the OTC markets.

Effects of the Reverse Stock Split

The Reverse Stock Split will be effected simultaneously for all issued and outstanding shares of common stock and the Reverse Stock Split ratio will be the same for all issued and outstanding shares of common stock. The Reverse Stock Split will affect all of our stockholders uniformly and will not affect any stockholder’s percentage ownership interests in the Company, except that stockholders who would have otherwise received fractional shares will receive cash in lieu of such fractional shares. After the Reverse Stock Split, each share of our common stock will have the same voting rights and rights to dividends and distributions and will be identical in all other respects to the common stock now authorized and common stock issued pursuant to the Reverse Stock Split will remain fully paid and non-assessable. The Reverse Stock Split is not intended as, and will not have the effect of, a “going private transaction” covered by Rule 13e-3 under the Exchange Act. We will continue to be subject to the periodic reporting requirements of the Exchange Act.

The following table sets forth the number of shares of the common stock that would be outstanding immediately after the Reverse Stock Split at various exchange ratios, based on the 37,595,787 shares of common stock outstanding as of April 25, 2023. The table does not account for fractional shares that will be paid in cash.

If a stockholder owns 10,000 shares of common stock prior to the Reverse Stock Split, after the Reverse Stock Split that same stockholder would own:

The Reverse Stock Split will not change the number of authorized shares of common stock or preferred stock or the relative voting power of such holders of our outstanding common stock and preferred stock.

Therefore, the number of authorized but unissued shares of our common stock will effectively increase and will be available for reissuance by the Company. Given the Company’s current financial position and liquidity needs within the next year to advance its pipeline, the Board has determined that maintaining the Company’s current number of authorized shares is warranted and in the best interest of the Company and its stockholders. Failure to successfully receive additional financing will require the Company to delay, scale back or otherwise modify its business and its research and development activities and other operations. These factors raise substantial doubt about the Company’s ability to continue as a going concern, and therefore maintaining the Company’s ability to raise additional financing through an issuance of its authorized shares is important to the Company’s continued operations.

After the effective date of the Reverse Stock Split that our Board elects to implement, our common stock would have a new committee on uniform securities identification procedures number (“CUSIP number”), a number used to identify our common stock. Our common stock is currently registered under Section 12(b) of the Exchange Act and we are subject to the periodic reporting and other requirements of the Exchange Act.

Accounting Matters

The Reverse Stock Split will not affect the par value of the common stock. As a result, upon the effectiveness of the Reverse Stock Split, the stated capital on our balance sheet attributable to the common stock will be reduced proportionately based on the exchange ratio selected by our Board for the Reverse Stock Split, and the additional paid-in capital account will be credited with the amount by which the stated capital is reduced. The per share net income or loss and net book value of the common stock will be decreased because there will be fewer shares of common stock outstanding. In addition, proportionate adjustments will be made to the per share exercise price and the number of shares issuable upon the exercise or settlement of all outstanding options, restricted stock units and warrants to purchase or acquire, as applicable, shares of common stock, and the number of shares reserved for issuance pursuant to our existing equity incentive, stock option and employee stock purchase plans will be reduced proportionately based on the exchange ratio selected by the Board for the Reverse Stock Split.

No Fractional Shares

No fractional shares of common stock will be issued as a result of the Reverse Stock Split. Instead, stockholders who otherwise would be entitled to receive fractional shares will be entitled to receive cash in an amount equal to the product obtained by multiplying (i) the closing sales price of the common stock as reported on the Nasdaq Global Select Market on the effective date of the certificate of amendment to the Certificate of Incorporation by (ii) the number of shares of common stock held by such stockholder before the Reverse Stock Split that would otherwise have been exchanged for such fractional share interest. Holders of as many as 9 shares (if we were to implement a 1-for-10 Reverse Stock Split) of common stock would be eliminated as a result of the cash payment in lieu of any issuance of fractional shares or interests in connection with the Reverse Stock Split. The exact number by which the number of holders of the common stock would be reduced will depend on the Reverse Stock Split ratio adopted and the number of stockholders that hold less than the Reverse Stock Split ratio as of the effective date of the Reverse Stock Split. As of the record date, there were approximately 14 holders of record of the common stock, none of which held fewer than 10 shares of common stock.

Certain Risks Associated with the Reverse Stock Split

Before voting on this Proposal 2, stockholders should consider the following risks associated with effecting a Reverse Stock Split:

Potential Anti-Takeover Effect of the Reverse Stock Split

Upon effectiveness of the Reverse Stock Split, the number of authorized shares of common stock that are not issued or outstanding will increase relative to the number of shares of common stock that are issued and outstanding prior to the Reverse Stock Split. While this increase could, under certain circumstances, have an anti-takeover effect (for example, by permitting issuances that would dilute the stock ownership of a person seeking to effect a change in the composition of the Board or contemplating a tender offer or other transaction for the combination of the Company with another company), Proposal 2 is not being proposed in response to any effort of which we are aware to accumulate shares of the common stock or to obtain control of the Company.

Effective Date

If our stockholders approve the Reverse Stock Split, the Reverse Stock Split would become effective at such time as it is deemed by our Board to be in the best interests of the Company and our stockholders and we file the amendment to our Certificate of Incorporation. Even if the Reverse Stock Split is approved by our stockholders, our Board has discretion not to carry out or to delay in carrying out the Reverse Stock Split. Upon the filing of the amendment, all of the pre-Reverse Stock Split shares will be converted into new common stock as set forth in the amendment.

Exchange of Stock Certificates

Some stockholders hold their shares of common stock in certificate form or a combination of certificate and book-entry form. Our transfer agent will act as the “exchange agent” for purposes of implementing the exchange of stock certificates. Stockholders holding pre-split shares that are certificated will be asked to surrender to the exchange agent certificates representing pre-split shares in exchange for certificates representing post-split shares in accordance with the procedures to be set forth in a letter of transmittal to be sent by the exchange agent. No new certificates will be issued to a stockholder until such stockholder has surrendered the stockholder’s outstanding certificate(s) together with the properly completed and executed letter of transmittal to the exchange agent.

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

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

The following is a summary of certain material U.S. federal income tax consequences of the Reverse Stock Split that generally are expected to be applicable to U.S. Holders (as defined below) of the common stock, but does not purport to be a complete discussion of all of the potential tax considerations relating thereto. This summary is based on the provisions of the U.S. federal income tax law (including the Internal Revenue Code of 1986, as amended, or the Code, applicable Treasury Regulations promulgated thereunder, judicial authorities and current administrative rulings and practices as in effect on the date of this proxy statement). Changes to these laws could alter the tax consequences described below, possibly with retroactive effect, which may result in the U.S. federal income tax consequences of the Reverse Stock Split differing substantially from the consequences summarized below. We have not sought and will not seek an opinion of counsel or a ruling from the Internal Revenue Service regarding the U.S. federal income tax consequences of the Reverse Stock Split, and there can be no assurance that the Internal Revenue Service or the courts will accept the positions expressed below. This summary assumes that the common stock will be, both before and after the Reverse Stock Split, held as a “capital asset,” as defined in the Code (i.e., generally, property held for investment). Further, it does not discuss the tax consequences of the Reverse Stock Split under state, local or foreign laws or under gift, excise or other non-income tax laws, or the application of the alternative minimum tax rules, the Medicare contribution tax on net investment income or the special tax accounting rules under Section 451(b) of the Code. This summary does not address the tax consequences of transactions effectuated prior or subsequent to, or concurrently with, the Reverse Stock Split (whether or not any such transactions are consummated in connection with the Reverse Stock Split), or the tax consequences to holders of options, warrants or similar rights to acquire common stock. In addition, this summary does not address the tax consequences applicable to a holder’s particular circumstances or to holders that are subject to special tax rules, including without limitation banks, financial institutions, insurance companies, regulated investment companies, mutual funds, real estate investment trusts, personal holding companies, foreign entities, nonresident alien individuals, broker-dealers, traders, tax-exempt entities, persons who hold common stock as a position in a hedging transaction, “straddle,” “conversion transaction” or other integrated or risk reduction transaction, persons whose common stock constitutes qualified small business stock within the meaning of Section 1202 of the Code, holders who hold their common stock through individual retirement or other tax-deferred accounts, holders of common stock that are not U.S. Holders (as defined below), holders of common stock that have a functional currency for U.S. federal income tax purposes other than the U.S. dollar, holders who acquired their common stock in a transaction subject to the gain rollover provisions of Section 1045 of the Code, holders who acquired their common stock pursuant to the exercise of employee stock options or otherwise as compensation, or holders of common stock that are partnerships, limited liability companies that are not treated as corporations for U.S. federal income tax purposes, S corporations, or other pass-through entities or investors in such pass-through entities.

For purposes of this discussion, a U.S. Holder means a beneficial owner of our common stock that is: (i) an individual who is a citizen or resident of the United States; (ii) a corporation (or other entity taxable as a corporation for U.S. federal income tax purposes) created or organized in the United States or under the laws of the United States or any subdivision thereof, or the District of Columbia; (iii) an estate the income of which is includible in gross income for U.S. federal income tax purposes regardless of its source; or (iv) a trust (other than a grantor trust) if (A) a court within the United States is able to exercise primary supervision over the administration of the trust and one or more United States “persons” (within the meaning of Section 7701(a)(30) of the Code) have the authority to control all substantial decisions of the trust or (B) it has a valid election in effect under applicable U.S. Treasury regulations to be treated as a United States person for U.S. federal income tax purposes.

THIS SUMMARY OF CERTAIN MATERIAL U.S. FEDERAL INCOME TAX CONSEQUENCES OF THE REVERSE STOCK SPLIT IS FOR GENERAL INFORMATION ONLY AND IS NOT TAX ADVICE.

EACH STOCKHOLDER IS URGED TO CONSULT WITH SUCH STOCKHOLDER’S OWN TAX ADVISOR WITH RESPECT TO THE TAX CONSEQUENCES OF THE REVERSE STOCK SPLIT.

Tax Consequences of the Reverse Stock Split

The Reverse Stock Split should constitute a “recapitalization” for U.S. federal income tax purposes. A U.S. Holder that receives solely a reduced number of shares of common stock generally will not recognize gain or loss in the Reverse Stock Split. A U.S. Holder’s aggregate tax basis in the reduced number of shares of common stock should equal the U.S. Holder’s aggregate tax basis in its pre-Reverse Stock Split shares of common stock, and such U.S. Holder’s holding period in the reduced number of shares of common stock should include the holding period in its pre-Reverse Stock Split shares of common stock exchanged. Treasury Regulations provide detailed rules for allocating the tax basis and holding period of the shares of common stock surrendered to the shares of common stock received in a recapitalization pursuant to the Reverse Stock Split. U.S. Holders should consult their tax advisors as to application of the foregoing rules where shares of common stock were acquired at different times or at different prices.

No gain or loss will be recognized by the Company as a result of the proposed Reverse Stock Split.

Cash in Lieu of Fractional Shares

A U.S. Holder that receives cash in lieu of fractional share interests as a result of the Reverse Stock Split will be treated as having received the fractional shares pursuant to the Reverse Stock Split and then as having exchanged the fractional shares for cash in a redemption by the Company, and generally should recognize gain or loss equal to the difference, if any, between the amount of cash received in lieu of a fractional share and its adjusted basis allocable to the fractional share interests. Such gain or loss will be long-term capital gain or loss if the pre-Reverse Stock Split shares were held for more than one year. Long-term capital gains of individuals are generally subject to tax at reduced rates. There are limitations on the deductibility of capital losses under the Code. A U.S. Holder’s aggregate tax basis in the reduced number of shares of common stock, if any, should equal the U.S. Holder’s aggregate tax basis in its pre-Reverse Stock Split shares of common stock decreased by the basis allocated to the fractional share for which such U.S. Holder is entitled to receive cash, and the holding period of the reduced number of shares of common stock received, if any, should include the holding period of the pre-Reverse Stock Split shares of common stock exchanged.

Information Reporting and Backup Withholding

A holder of common stock may be subject to information reporting and backup withholding on cash paid in lieu of fractional shares in connection with the Reverse Stock Split. To avoid backup withholding, each holder of common stock that does not otherwise establish an exemption should provide its taxpayer identification number and comply with the applicable certification procedures. Backup withholding is not an additional tax. Any amounts withheld under the backup withholding rules generally will be allowed as a refund or credit against a U.S. Holder’s U.S. federal income tax liability, provided the required information is timely and properly furnished to the Internal Revenue Service. Holders of common stock should consult their tax advisors regarding their qualification for an exemption from backup withholding and the procedures for obtaining such an exemption, as well as the procedures for obtaining a credit or refund if backup withholding is imposed.

THE PRECEDING DISCUSSION IS INTENDED ONLY AS A SUMMARY OF CERTAIN MATERIAL U.S. FEDERAL INCOME TAX CONSEQUENCES OF THE REVERSE STOCK SPLIT TO U.S. HOLDERS. IT IS NOT A COMPLETE ANALYSIS OR DISCUSSION OF ALL POTENTIAL TAX EFFECTS THAT MAY BE IMPORTANT TO A PARTICULAR HOLDER. ALL HOLDERS OF OUR COMMON STOCK SHOULD CONSULT THEIR OWN TAX ADVISORS AS TO THE SPECIFIC TAX CONSEQUENCES OF THE REVERSE STOCK SPLIT TO THEM, INCLUDING RECORD RETENTION AND TAX-REPORTING REQUIREMENTS, AND THE APPLICABILITY AND EFFECT OF ANY U.S. FEDERAL, STATE, LOCAL AND NON-U.S. TAX LAWS.

No Dissenters’ Rights

Under applicable Delaware law, our stockholders are not entitled to dissenters’ or appraisal rights with respect to our proposed amendment to the certificate of incorporation to effect the Reverse Stock Split. We will not independently provide our stockholders with any such right.

Vote Required

The affirmative vote of the holders of a majority of all outstanding shares of the common stock on the record date is required for approval of the proposed amendment to our Certificate of Incorporation to effect a Reverse Stock Split set forth in this Proposal 2. Because we believe Proposal 2 is considered “routine,” we do not expect any broker non-votes for this proposal.

THE BOARD RECOMMENDS

A VOTEIN FAVOROF PROPOSAL NO. 2.

PROPOSAL 3: RATIFICATION OF THE SELECTION OF THE INDEPENDENT REGISTERED

PUBLIC ACCOUNTING FIRM

The Audit Committee of the Board has selected Ernst & Young LLP as our independent registered public accounting firm for the fiscal year ending December 31, 20212023 and has further directed that management submit the selection of its independent registered public accounting firm for ratification by the stockholders at the Annual Meeting. Ernst & Young LLP has audited the Company’s financial statements since 2017. Representatives of Ernst & Young LLP are expected to be present at the Annual Meeting with the opportunity to make a statement if they desire and to respond to appropriate questions.

Our organizational documents do not require that the stockholders ratify the selection of Ernst & Young LLP as our independent registered public accounting firm. However, the Audit Committee of the Board is submitting the selection of Ernst & Young LLP to the stockholders for ratification as a matter of good corporate practice. If the stockholders fail to ratify the selection, the Audit Committee of the Board will reconsider whether to retain that firm. Even if the selection is ratified, the Audit Committee of the Board in its discretion may direct the appointment of a different independent registered public accounting firm at any time during the year if they determine that such a change would be in the best interests of the Company and its stockholders.

Vote Required

The affirmative vote of the holders of a majority of the shares present or represented by proxy and entitled to vote on the matter at the Annual Meeting will be required to ratify the selection of Ernst & Young LLP.

Independent Registered Public Accounting Firm Fees

The following is a summary and description of fees incurred by Ernst & Young LLP for the fiscal years ended December 31, 20202022 and 2019,2021 by Ernst & Young LLP, our independent registered public accounting firm. All fees described below were pre-approved by the Audit Committee.

Pre-Approval Policies and Procedures

Consistent with requirements of the SEC and the Public Company Accounting Oversight Board regarding independent registered public accounting firm independence, our Audit Committee is responsible for the appointment, compensation and oversight of the work of our independent registered public accounting firm. In recognition of this responsibility, our Audit Committee pre-approves all audit and permissible non-audit services provided by our independent registered public accounting firm. These services may include audit services, audit-related services, tax services and other services.

ThePursuant to our pre-approval policy and procedures, our Audit Committee elected to delegate pre-approvalhas delegated authority to the chairChair of theour Audit Committee to approve any one or more individual permitted non-audit services for whichservice that has estimated fees do not exceedof up to $75,000 as well asand any adjustments to any estimated pre-approval fee thresholds up to $50,000 for any individual service. Any services that would exceed such limits shouldmust be pre-approved by theour full Audit Committee. The chair shall reportChair of the Audit Committee reports any pre-approval granted at the next scheduled meeting of the Audit Committee.

Our RecommendationTHE BOARD RECOMMENDS

THE BOARD UNANIMOUSLY RECOMMENDS A VOTE VOTEIN FAVOR FAVOROF PROPOSAL 2. PROPOSAL NO. 3.

INFORMATION ABOUT OUR EXECUTIVE OFFICERS

The following table sets forth information regarding our executive officers as of March 24, 2021:April 27, 2023:

Gerald McMahon, Ph.D.Julie Eastland. Biographical information for Dr. McMahonMs. Eastland is included above with the director biographies under the caption “Information About Our Continuing Directors.section titled “Proposal 1: Election of Directors.”

Georgia Erbez has served as our Chief Financial Officer since October 2018. From September 2016 to May 2018, Ms. Erbez served as the Chief Business Officer and Chief Financial Officer at Zosano Pharma Corp., a pharmaceutical company, after serving as its Interim Chief Financial Officer from June 2016 to September 2016. Ms. Erbez also served as the Senior Vice President and Chief Financial Officer at Revolution Medicines, a biotechnology company, from May 2016 to September 2016, the Executive Vice President and Chief Financial Officer at Asterias Biotherapeutics, a biotechnology company, from November 2015 to March 2016, and the Chief Financial Officer at Raptor Pharmaceuticals, a pharmaceutical company, from September 2012 to November 2014. From November 2014 to October 2018, Ms. Erbez was also a Managing Director at Axiom Financial Partners, a life sciences consulting firm. Ms. Erbez currently serves as a member of the Board of Directors of Altibio, Inc. Ms. Erbez holds a B.A. in International Relations, with an emphasis in Economics, from the University of California, Davis.

Natalie Sacks,Luke Walker, M.D. has served as our Chief Medical Officer since October 2018. From September 2016 to September 2018,2022. Dr. Sacks was the Chief Medical Officer at Aduro Biotech, Inc., an immunotherapy company. Prior to Aduro, she was Vice President of Clinical Development at Onyx Pharmaceuticals (acquired by Amgen Inc.), a biopharmaceutical company, from April 2011 to February 2014, where she played a key role in the development and approval of Kyprolis, an FDA-approved therapy for the treatment of relapsed or refractory multiple myeloma, and in business development strategy. From September 2009 to March 2011, sheWalker previously served as Vice President, ofClinical Development and Group Lead, Early-Stage Clinical Development for Seagen, Inc. from March 2018 to September 2022. He was Senior Vice President, Clinical Development for Cascadian Therapeutics Inc., and held other positions, including Vice President, Clinical Development, Senior Director, Clinical Research, for Exelixis, Inc., a genomics pharmaceutical company. From November 2002and Director, Clinical Research from 2011 to April 2009,2018. Prior to that, Dr. SacksWalker served as Vice President of Clinical Developmenta medical oncologist and hematologist at Cell Genesys, Inc., an immuno-oncology company. Dr. Sacks currently serves asProvidence Regional Medical Center, Everett from 2007 to 2011 and at The Everett Clinic, Center for Cancer Care from 2005 to 2007. He is a membercurrent Diplomate of the boardsAmerican Board of directors of the public company Zymeworks, Inc. (NYSE: ZYME)Internal Medicine in Medical Oncology, with prior board certifications in Hematology and Caribou Biosciences, Inc.Internal Medicine. Dr. Sacks has servedWalker completed fellowships in a variety of researchbone marrow and analytical rolesstem cell transplantation and hematology and medical oncology at academic institutionsOregon Health Sciences University and companies, including Massachusetts General Hospital, Medical College of Pennsylvania, and ICI-Stuart Pharmaceuticals. From 2004 to 2016, Dr. Sacks has served ashe received an assistant clinical professor of medicine in the Division of Hematology/Oncology at theM.D. from University of California, San Francisco. She holdsOklahoma Health Sciences Center. He also received a B.A.Doctor of Medicine from University of Oklahoma Health Sciences Center. Dr. Walker also has a Bachelor of Arts in Mathematics from Bryn Mawr College, an M.S. in Biostatistics from Harvard University School of Public Healthletters and an M.D.French from the University of PennsylvaniaOklahoma and completed the Stanford Graduate School of Medicine.

Holger Wesche, Ph.D. has served as our Chief Scientific Officer since October 2018. From January 2017 to October 2018, he served as our Senior Vice President of Research, and from April 2015 to January 2017, he served as our Vice President of Research. From March 2013 to April 2015, Dr. Wesche was a Scientific Director at Amgen Inc., a biopharmaceutical company, where he was responsible for cross-functional organization and coordination of the next generation BiTE^™ platform, a T cell engaging antibody platform. Dr. Wesche’s experience has focused on target validation, drug discovery and drug development as well as multi-site project management in the fields of oncology and inflammation, and he has led several drug discovery projects through pre-clinical development. Dr. Wesche is also the co-author of numerous publications and several U.S. patents. Dr. Wesche holds an M.S. equivalent in Biochemistry, Biophysical Chemistry and Immunology and earned a Ph.D. equivalent for his work on the IL-1 receptor complex, each from the University of Hannover in Germany.Business Executive Leadership Program.

EXECUTIVE OFFICER AND DIRECTOR COMPENSATION

Executive Officer Compensation

Summary Compensation Table

The following table sets forth information for each of the last two completed fiscal years regarding compensation awarded to or earned by all individuals that served as our principal executive officer, and the two other most highly compensated executive officers other than the principal executive officer during the fiscal years indicated and the two additional individuals for whom disclosure would have been provided but for the fact that such individual was not serving as an executive officer at the end of the last fiscal year (collectively, the “named executive officers”) during the fiscal years indicated::

Outstanding Equity Awards at Fiscal Year-End

The following table provides information regarding equity awards held by the named executive officers that were outstanding as of December 31, 2020,2022 under the 2015 Plan (as defined below) and, the 2019 Plan (as defined below) and, in the case of Dr. Walker, the Inducement Plan (as defined below):

Narrative to Summary Compensation Table and Outstanding Equity Awards at 20202022 Fiscal Year End

Employment Agreements and Potential Payments and Benefits Upon Termination or Change in Control

Below are descriptions of our employment agreements and arrangements with our named executive officers. The agreements generally provide for at-will employment without any specific term and set forth the named executive officer’s initial base salary, annual target bonus and severance benefits upon a qualifying termination of employment or change in control of our company. Each named executive officer is also eligible to participate in all employee benefit plans that are generally available to our employees.employees during his or her employment. Furthermore, each of our named executive officers has executed our standard form of proprietary information and inventions assignment agreement. The key terms of the employment agreements with our named executive officers, including potential payments upon termination or change in control with regard to our named executive officers who were serving as of December 31, 2022, are described below.

Committee. Dr. Walker is eligible for an annual performance bonus as determined by our Compensation Committee. Effective January 1, 2023, Dr. Walker’s target bonus was set as 40% of his annual base salary.

If within 60 days prior to or within 24 months after a “change in control” (as defined in his employment agreement), Dr. Walker’s employment is terminated by us without “cause” or by Dr. Walker for “good reason” (each as defined in the employment agreement), then he would receive (i) full vesting of his outstanding equity awards, (ii) a lump sum severance payment equivalent to 12 months of his then-current base salary plus an amount equal to his target bonus for the year in which his separation occurs and (iii) up to 12 months of reimbursement of COBRA premiums, except such reimbursements will not exceed the amount we then pay for health insurance coverage for our active employees, in each case subject to the execution of an effective release. Upon a termination of Dr. Walker’ employment without cause or for good reason at any other time, Dr. Walker would receive (i) a lump sum severance payment equal to 9 months of his then-current base salary and (ii) up to 9 months of reimbursement of COBRA premiums, except such reimbursements will not exceed the amount we then pay for health insurance coverage for our active employees, in each case subject to the execution of an effective release.

Georgia Erbez

Pursuant to our employment agreement with Ms. Erbez, we agreed to an initial annual base salary, which could be increased from time to time based on the review of our Compensation Committee. Ms. Erbez’s annual base salary was $415,000 in 2021 and was set as $430,000 for 2022. During her employment, Ms. Erbez was eligible for an annual performance bonus as determined by our Compensation Committee. Ms. Erbez’s annual target bonus was set as 40% of her annual base salary in 2021 and 40% of her annual base salary in 2022.

Natalie Sacks, M.D.

Pursuant to our employment agreement with Dr. Sacks, we agreed to an initial annual base salary, which could be increased from time to time based on the review of our Compensation Committee. Dr. Sacks’s annual base salary was $465,000 in 2021 and set as $477,000 for 2022. During her employment, Dr. Sacks was eligible for an annual performance bonus as determined by our Compensation Committee. Dr. Sacks’s annual target bonus was set as 40% of her annual base salary in 2021 and 40% of her annual base salary in 2022.

Holger Wesche, Ph.D.

Pursuant to our employment agreement with Dr. Wesche, we agreed to an initial annual base salary, which could be increased from time to time based on the review of our Compensation Committee. Dr. Wesche’s annual base salary was $400,000 in 2021 and $430,000 in 2022. During his employment, Dr. Wesche was eligible for an annual performance bonus as determined by our Compensation Committee. Dr. Wesche’s annual target bonus was set as 40% of his annual base salary in 2021 and 40% of his annual base salary in 2022.

In January 2023, Dr. Wesche entered into a separation agreement with us, pursuant to which he received (i) severance pay equivalent to 9 months of his base salary in effect as of the date of his termination, (ii) a bonus payment of $172,000 and (iii) up to 9 months of reimbursement of COBRA premiums. Under the terms of the separation agreement, Dr. Wesche will serve as a consultant until October 15, 2023 and, after the expiration of the consulting period, he will have until April 30, 2025 to exercise any vested options.

Bonus and Non-Equity Plan Compensation

Cash bonuses are intended to motivate and reward our executive officers for attaining rigorous annual corporate performance goals that relate to our key business objectives. The Compensation Committee reviews annually the target bonus amounts. The Compensation Committee determines actual bonus amounts earned after the end of the year based on the Company’s overall performance and each individual’s achievement and contributions.

Our annual corporate performance goals are typically established around the beginning of each year. Management prepares a set of goals covering corporate, development and financial objectives and key activities, which is then reviewed and, following any modification the Compensation Committee deems appropriate, approved by our Compensation Committee.

The Compensation Committee does not use a formula to calculate the Company’s or any individual’s performance. Rather, it qualitatively evaluates the totality of the Company’s progress and performance, contribution towards the creation of long-term stockholder value, and achievements relative to the goals.

In January 2021,2023, the compensation committeeCompensation Committee completed an evaluation of our overall performance for 2020,2022, and the named executive officers’ respective contributions in achieving this performance. The compensation committee’sCompensation Committee’s review was based on company performance against high impact company goals, including clinical, preclinical, technology platforms and overall general administrative matters including financing, human resourcing and other administrative achievements. Following such review, the compensation committee exercised its discretion in awardingCompensation Committee awarded Ms. Eastland and Dr. McMahon, Dr. Sacks and Ms. ErbezWalker cash bonuses of $274,500, $184,800$217,525 and $156,000,$49,400 (target bonus of $200,000, prorated), respectively. Ms. Eastland was also awarded an additional discretionary cash bonus in the amount of $62,150 in recognition of her work fulfilling chief financial officer and business development functions following the Company’s staff changes in 2022. Dr. Wesche did not receive bonus and non-equity plan compensation for 2022 because he was no longer with the Company at the time bonuses were paid.

Equity, Benefit and Retirement Plans

We believe that our ability to grant equity-based awards is a valuable and necessary compensation tool that aligns the long-term financial interests of our employees, consultants, and directors with the financial interests of our stockholders. In addition, we believe that our ability to grant stock options and other equity-based awards helps us to attract, retain, and motivate employees, consultants, and directors and encourages them to devote their best efforts to our business and financial success. The principal features of our equity incentive plans and our 401(k) plan are summarized below. These summaries are qualified in their entirety by reference to the actual text of the plans.

2019 Equity Incentive Plan

Our Board adopted and our stockholders approved our 2019 Equity Incentive Plan (the “2019 Plan”) in January 2019 for the purpose of attracting, retaining and incentivizing our executive officers, employees, non-employee directors and other service providers. Our 2019 Plan provides for the grant of incentive stock options (within the meaning of Section 422 of the Code), nonstatutory stock options, stock appreciation rights, (“SARs”), restricted stock awards, restricted stock unit awards, performance-based stock awards and other forms of equity compensation, which are collectively referred to as stock awards. Our 2019 Plan also provides for the grant of performance cash awards.

Share Reserve

The aggregate number of shares of our common stock that may be issued pursuant to stock awards under our 2019 Plan was 2,284,5252,254,423 as of December 31, 2020.2022. Additionally, the number of shares of our common stock reserved for issuance under our 2019 Plan will automatically increase on January 1 of each year, beginning on January 1, 2020 and continuing through and including January 1, 2029, by 5% of the total number of shares of our capital stock outstanding on December 31 of the preceding calendar year, or a lesser number of shares determined by our Board. On January 1, 2021,2023, the total number of shares available for issuance under the 2019 Plan was increased by 1,278,7041,789,337 shares pursuant to this provision. The number of shares reserved for issuance under the 2019 Plan will also be increased by the number of shares subject to stock options or other stock awards

Corporate Transactions

In the event of certain specified significant corporate transactions, the plan administrator has the discretion to take any of the following actions with respect to stock awards:

Our plan administrator is not obligated to treat all stock awards, even those that are of the same type, in the same manner.

Under our 2019 Plan, a significant corporate transaction is generally the consummation of (1) a sale or other disposition of all or substantially all of our assets, (2) a sale or other disposition of at least 50% of our outstanding securities, (3) a merger, consolidation or similar transaction following which we are not the surviving corporation or (4) a merger, consolidation or similar transaction following which we are the surviving corporation but the shares of our common stock outstanding immediately prior to such transaction are converted or exchanged into other property by virtue of the transaction.

Change in Control

The plan administrator may provide, in an individual award agreement or in any other written agreement between a participant and us that the stock award will be subject to additional acceleration of vesting and exercisability or settlement in the event of a change in control. Under our 2019 Plan, a change in control is generally (1) the acquisition by a person or entity of more than 50% of our combined voting power other than by merger, consolidation or similar transaction, (2) a consummated merger, consolidation or similar transaction immediately after which our stockholders cease to own more than 50% of the combined voting power of the surviving entity or (3) a consummated sale, lease or exclusive license or other disposition of all or substantially all of our assets.

2015 Equity Incentive Plan

In April 2015, our Board and our stockholders adopted our 2015 Equity Incentive Plan (the “2015 Plan”), which was subsequently amended most recently in December 2018. Our 2015 Plan provided for the grant of incentive stock options within the meaning of Section 422 of the Code to our employees and our parent and subsidiary corporations’ employees, and for the grant of nonstatutory options, restricted stock awards, restricted stock unit awards and stock appreciation rights our employees, consultants and directors.

Corporate Transactions

Our 2015 Plan provides that in the event of a merger of our company into another corporation or entity, or a change in control (as defined in our 2015 Plan), the administrator will determine how to treat each outstanding stock award. The administrator may:

If awards are not assumed or substituted, they will vest and become exercisable in full. The administrator is not obliged to treat all stock awards or portions of stock awards, even those that are of the same type, in the same manner.

2019 Employee Stock Purchase Plan

Our Board adopted and our stockholders approved our 2019 Employee Stock Purchase Plan (“2019 ESPP”) in January 2019, and the 2019 ESPP became effective in connection with our initial public offering in February 2019. The purpose of the 2019 ESPP is to secure the services of new employees, to retain the services of existing employees and to provide incentives for such individuals to exert maximum efforts toward our success and that of our affiliates. Our employees, including executive officers, and the employees of any of our designated affiliates are eligible to participate in our 2019 ESPP, provided they may have to satisfy one or more of the following service requirements before participating in our 2019 ESPP, as determined by the administrator: (1) customary employment with us or one of our affiliates for more than 20 hours per week and five or more months per calendar year or (2) continuous employment with us or one of our affiliates for a minimum period of time, not to exceed two years, prior to the first date of an offering. An employee may not be granted rights to purchase stock under our 2019 ESPP (a) if such employee immediately after the grant would own stock possessing 5% or more of the total combined voting power or value of all classes of our common stock or (b) to the extent that such rights would accrue at a rate that exceeds $25,000 worth of our stock for each calendar year that the rights remain outstanding.

Share Reserve

The maximum number of shares of our common stock that may be issued under our 2019 ESPP was 438,163717,106 shares as of December 31, 2020.2022. Additionally, the number of shares of our common stock reserved for issuance under our 2019 ESPP will automatically increase on January 1 of each year, beginning on January 1, 2020 and continuing through and including January 1, 2029, by the lesser of (1) 1% of the total number of shares of our common stock outstanding on December 31 of the preceding calendar year, (2) 750,000 shares of our common stock or (3) such lesser number of shares of our common stock as determined by our Board. On January 1, 2021,2023, the total number of shares available for issuance under the 2019 ESPP was increased by 255,740

Nasdaq Listing Rule 5635(c)(4). The Inducement Plan provides for the grant of equity-based awards, including nonstatutory stock options, restricted stock units, and other stock-based awards, and its terms are substantially similar to the stockholder-approved 2019 Plan. In accordance with relevant Nasdaq listing rules, awards under the Inducement Plan may only be made to individuals who were not previously employees or non-employee directors of ours (or following such individuals’ bona fide period of non-employment with us), as an inducement material to the individual’s entry into employment with us. In addition, awards must be approved by either a majority of the Company’s “independent directors” (as such term is defined in Nasdaq Listing Rule 5605(a)(2)) or the Compensation Committee, provided such committee is comprised solely of independent directors.

The maximum number of shares of our common stock that may be issued under our Inducement Plan is 1,000,000 shares. Shares subject to stock awards granted under our Inducement Plan that expire or terminate without being exercised in full, or that are paid out in cash rather than in shares, do not reduce the number of shares available for issuance under our Inducement Plan. We have granted nonstatutory stock option awards to purchase an aggregate of 305,000 shares of common stock to new hires who joined during 2022 as material inducements to their acceptance of employment with us in accordance with Nasdaq Listing Rule 5635(c)(4), all of which remain outstanding and were granted pursuant to a form of nonstatutory stock option grant notice and option agreement previously approved by our Board.

Health and Welfare Benefits

All of our named executive officers are eligible to participate in our employee benefit plans, including our medical, dental, vision and visionlife insurance plans, in each case on the same basis as all of our other full-time employees.

401(k) Plan

We maintain a 401(k) plan pursuant to which our employees (subject to certain exceptions) are eligible to participate. Our named executive officers are eligible to participate in the 401(k) plan. Participants mayFor 2022, participants could defer up to 100% of their salary, however, their contributions would stop atup to the IRS dollar amount limits which is $19,500, andwas $20,500, with an additional $6,500 in catchup for participants ages 50 and up. We also fundfunded a 3% profit sharing contribution for the 20202022 401(k) plan.

No Tax Gross-Ups

We do not make gross-up payments to cover our named executive officers’ personal income taxes that may pertain to any of the compensation or perquisites paid or provided by us.

Director Compensation

Non-Employee Director Compensation Policy

Our Board adopted a Non-Employee Director Compensation Policy, referred to herein as the policy, effective as of February 7, 2019, and amended the policy, referred to herein as the amended policy, inmost recently on March 2021.9, 2023 (the “policy”). Under the policy, each of our non-employee directors are eligible to receive compensation for service on our Board and committees of our Board. Non-employee directors also receive reimbursement for out-of-pocket expenses incurred in connection with attendance at meetings of the Board.

The policy provides our non-employee directors with the following cash compensation for their services:

The cash compensation above is payable to our eligible non-employee directors in equal quarterly installments, prorated for any partial quarter of service.

EachFor the calendar year 2023, each non-employee director may elect to receive all (but not less than all) of his or hertheir annual cash compensation under the policy in the form of a fully vested restricted stock unit award (“election RSU”). The election must be made according to procedures and timing set forth in the relevant election form. Each election RSU is granted on the day following the final day of each quarter (each such date, an “RSU Grant Date”) in lieu of the cash compensation they would otherwise have received for that quarter (such compensation, the “Quarterly Compensation”), subject to the non-employee director’s continuous service through such date. The number of shares of common stock subject to such non-employee director’s restricted stock unit award will be equal to the director’s Quarterly Compensation divided by the average stock price of our common stock in the five trading days immediately preceding the RSU Grant Date, rounded down to the nearest whole share.

For the calendar year 2022 and calendar years 2024 and later, each non-employee director may elect to receive all (but not less than all) of their annual cash compensation under the policy in the form of a stock option referred to herein as an (“election option.option”). Each such

Each option granted under the policy will be a nonstatutory stock option and will have an exercise price per share equal to the fair market value of a share of our common stock on the date of grant. Each stock option will have a term of ten years from the date of grant, subject to earlier termination in connection with a termination of the eligible director’s continuous service with us.

Non-Employee Director Compensation

The following table sets forth information regarding the compensation earned for service on the Board by our non-employee directors during the year ended December 31, 2020. The2022. Ms. Eastland’s compensation for Dr. McMahon as an executive officer is set forth above under “—Summary“Summary Compensation Table.” In March 2021, our Board of Directors appointed Dr. Colowick to our Board, and therefore Dr. Colowick is not included in the table below. Pursuant to the policy, Dr. Colowick will receive an annual cash retainer of $35,000 for service on the Board and $5,000 for service on the Compensation Committee (each amount pro-rated for 2021). In addition, we granted Dr. Colowick on the date of his appointment options to purchase 20,335 shares of our common stock at an exercise price per share of the closing price of our common stock on the Nasdaq Stock Market on the date of grant. The stock options will vest in a series of three equal annual installments measured from the date of grant,

Indemnification

Our amended and restated certificateCertificate of incorporationIncorporation authorizes us to indemnify our directors, officers, employees, and other agents to the fullest extent permitted by Delaware law. Our amended and restated bylaws provide that we are required to indemnify our directors and officers to the fullest extent permitted by Delaware

EQUITY COMPENSATION PLAN INFORMATION

The following table provides certain information with respect to all of our equity compensation plans in effect as of December 31, 2020.2022.

TRANSACTIONS WITH RELATED PERSONS

Certain Related-Party Transactions

In addition to the compensation arrangements with our directors and executive officers already described in this proxy statementProxy Statement under the headings “Non-Employee Director Compensation” and “Executive Officer and Director Compensation,” the following is a summary of transactions since January 1, 20192021 to which we have been a participant, in which:

We believe the terms obtained or consideration that we paid or received, as applicable, in connection with the transactions described below were comparable to terms available or the amounts that would be paid or received, as applicable in arm’s length transactions.

Participation in Our Initial Public Offering

In February 2019, we issued and sold an aggregate of 5,769,201 shares of our common stock for $14.00 per share, for aggregate cash proceeds of approximately $70.7 million, net of underwriting discounts and commissions and offering costs, which includes the partial exercise by the underwriters of their option to purchase additional shares. The table below sets forth the number of shares of our common stock issued to any of our directors, executive officers or stockholders who held more than 5% of any class of our voting securities and their affiliates: