UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of the

the Securities Exchange Act of 1934 (Amendment No.     )

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

Check the appropriate box:

LOGICBIO THERAPEUTICS, INC.

(Name of Registrant as Specified In Its Charter)

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

Payment of Filing Fee (Check the appropriate box):

(1) Amount Previously Paid:

LogicBio Therapeutics, Inc.

65 Hayden Avenue, Floor 2

Lexington, MA 02421

NOTICE OF 20202021 ANNUAL MEETING OF STOCKHOLDERS

The 20202021 Annual Meeting of Stockholders (the “Annual Meeting”) of LogicBio Therapeutics, Inc. (the “Company” or “LogicBio”) will be held on June 19, 2020,11, 2021, at 9:00 a.m. E.T., in a virtual meeting format at Ropes & Gray LLP, 800 Boylston St., Boston, Massachusetts,www.meetingcenter.io/252372261, for the purpose of considering and voting on the following two company-sponsored proposals:

We will also consider and act upon any other matters that properly come before the Annual Meeting or any adjournment or postponement thereof.

These proposals are more fully described in the Proxy Statement accompanying this Notice. This notice, the proxy statement and our Annual Report onForm 10-K for the year ended December 31, 20192020 (the “Annual Report”) can be accessed at the following website: www.envisionreports.com/LOGC.

Our Board of Directors recommends that you vote “for” each nominee for Class IIIII director (proposal no. 1) and “for” ratification of the proposed independent registered public accounting firm (proposal no. 2).

April 22, 20202021 has been fixed as the record date for the determination of the stockholders entitled to notice of and to vote at the Annual Meeting or any adjournments thereof. A list of stockholders as of the record date will be available for stockholder inspection at the headquarters of the Company, 65 Hayden Avenue, Floor 2, Lexington, MA 02421, during ordinary business hours, from June 9, 20201, 2021 to the date of the Annual Meeting. The list will also be available for inspection during the Annual Meeting.

Due to the ongoing COVID-19 pandemic and in the best interest of public health and the health and safety of our Board of Directors, employees and stockholders, we are holding a virtual-only meeting. Stockholders can attend the meeting via the Internet at www.meetingcenter.io/252372261 and submit questions related to the business of the Annual Meeting and to vote shares electronically at the Annual Meeting.

You will need your 15-digit control number, which appears in the Important Notice Regarding the Availability of Proxy Materials or your proxy card (printed in the shaded bar), or within the body of the email sending the proxy statement, to fully participate in the Annual Meeting virtually via the internet. If you hold shares beneficially through a bank, broker or other nominee (that is, in “street name”), you must register in advance to gain access to the Annual Meeting, submit questions and to vote shares during the meeting. To register, you will need to obtain a legal proxy from your bank, broker or other nominee. Once you have received a legal proxy from them, you must submit a copy of this legal proxy, along with your name and email address, to Computershare at legalproxy@computershare.com. Alternatively, you may mail your legal proxy to the following address: Computershare, LogicBio Therapeutics, Inc. Legal Proxy, P.O. Box 43001, Providence, RI 02940-3001. Requests for registration must be labeled as “Legal Proxy” and received no later than 5 p.m. Eastern Time on June 8, 2021. You will receive an email from Computershare confirming your registration and providing your control number. You will need your control number to access the Annual Meeting, submit questions and vote your shares electronically. The password for the meeting is LOGC2021.

Your vote is important. Whether or not you expect to attend the virtual-only Annual Meeting, we urge you to vote your shares by following the instructions in the Important Notice Regarding the Availability of Proxy Materials that you previously received and submit your proxy by the Internet or telephone or by signing, dating and returning the proxy card included in these materials in order to ensure that your vote is recorded. If you choose to attend the virtual-only Annual Meeting, you may

still vote your shares in person,during the Annual Meeting, even if you have previously voted or returned your proxy by any of the methods described in our proxy statement. If your shares are held in a bank or brokerage account, please refer to the materials provided by your bank or broker for voting instructions. If you need assistance voting your shares, please call Bryan Yoon, Esq., Corporate Secretary of the Company, at (617)245-0399.

All stockholders are extended a cordial invitation to attend the virtual-only Annual Meeting. Thank you for your ongoing support of and interest in LogicBio Therapeutics, Inc.

TABLE OF CONTENTS

i-i-

LogicBio Therapeutics, Inc.

65 Hayden Avenue, Floor 2

Lexington, MA 02421

PROXY STATEMENT FOR 20202021 ANNUAL MEETING OF STOCKHOLDERS

To Be Held on Friday, June 19, 202011, 2021 at 9:00 a.m. ET

This proxy statement, along with the accompanying Notice of 20202021 Annual Meeting of Stockholders, contains information about the 20202021 Annual Meeting of Stockholders of LogicBio Therapeutics, Inc., including any adjournments or postponements of the meeting, which we refer to as the Annual Meeting. We are holding the Annual Meeting at 9:00 a.m. ET via the Internet at Ropes & Gray LLP, 800 Boylston St., Boston, Massachusetts.www.meetingcenter.io/252372261.

In this proxy statement, we refer to LogicBio Therapeutics, Inc. as “LogicBio,” “the Company,” “we” and “us.”

This proxy statement relates to the solicitation of proxies by our Board of Directors for use at the Annual Meeting.

On or about April 29, 2020,27, 2021, we made available this proxy statement and the attached Notice of 2020 Annual Meeting of Stockholders to all stockholders entitled to vote at the Annual Meeting, and we began sending the Important Notice Regarding the Availability of Proxy Materials to all stockholders entitled to vote at the Annual Meeting. Although not part of this proxy statement, we have also made available with this proxy statement our Annual Report on Form10-K for the fiscal year ended December 31, 2019,2020, containing our financial statements for the fiscal year ended December 31, 2019.2020.

-1-

IMPORTANT NOTICE REGARDING THE AVAILABILITY OF PROXY MATERIALS

FOR THE STOCKHOLDER MEETING TO BE HELD ON JUNE 19, 202011, 2021

This proxy statement and our Annual Report on Form10-K are available for viewing, printing and downloading at www.envisionreports.com/LOGC. To view these materials, please have your15-digit control number(s) available that appears on the Availability of Proxy Materials or your proxy card.card (printed in the shaded bar), or within the body of the email sending the proxy statement.

Additionally, you can find a copy of our Annual Report on Form10-K on the website of the Securities and Exchange Commission, or the SEC, at www.sec.gov, or in the “SEC Filings” tab of the “Investors” section of our website at www.logicbio.com. You may also obtain a printed copy of our Annual Report, free of charge, by sending a written request to: LogicBio Therapeutics, Inc., 65 Hayden Avenue, Floor 2, Lexington, MA 02421, Attention: Corporate Secretary.Chief Financial Officer. Exhibits, if any, will be provided upon written request and payment of an appropriate processing fee.

EXPLANATORY NOTE

We are an “emerging growth company,” as defined in the Jumpstart Our Business Startups Act of 2012, or the JOBS Act, and therefore we are permitted and intend to rely on exemptions from certain disclosure requirements that are applicable to other public companies that are not emerging growth companies. These exemptions include reduced disclosure obligations regarding executive compensation. In addition, as an emerging growth company, we are not required to conduct votes seeking approval, on an advisory basis, of the compensation of our named executive officers or the frequency with which such votes must be conducted.

We could be an emerging growth company through 2023, although circumstances could cause us to lose that status earlier, including if the market value of our common stock held bynon-affiliates exceeds $700.0 million as of any June 30 before that time or if we have total annual gross revenue of $1.07 billion or more during any fiscal year before that time, in which cases we would no longer be an emerging growth company as of the following December 31 or, if we issue more than $1.00 billion innon-convertible debt during any three-year period before that time, we would cease to be an emerging growth company immediately.

IMPORTANT INFORMATION ABOUT THE ANNUAL MEETING AND VOTING

Why is the Company Soliciting My Proxy?

The Board of Directors of LogicBio Therapeutics, Inc. is soliciting your proxy to vote at the 20202021 Annual Meeting of Stockholders to be held at 9:00 a.m. ET on June 19, 2020,via a live webcast at Ropes & Gray LLP, 800 Boylston St., Boston, Massachusetts,www.meetingcenter.io/252372261 including any adjournments or postponements of the meeting, which we refer to as the Annual Meeting. This proxy statement along with the accompanying Notice of 20202021 Annual Meeting of Stockholders summarizes the purposes of the meeting and the information you need to know to vote at the Annual Meeting.

We have made available to you on the Internet the Notice of 20202021 Annual Meeting of Stockholders, the proxy card and a copy of our Annual Report on Form10-K for the fiscal year ended December 31, 20192020 because you owned shares of LogicBio common stock on the record date.

We intend to hold our Annual Meeting in person. However, we are actively monitoring thecoronavirus (COVID-19) situation and are sensitive to the public health and travel concerns our stockholders may have and the protocols that federal, state, and local governments may impose. In the event it is not possible or advisable to hold our Annual Meeting in person, we will announce alternative arrangements for the meeting as promptly as practicable, which may include holding the meeting solely by means of remote communication. If we take this step, we will announce the alternative arrangements via press release, which will be filed as Definitive Additional Materials with the SEC, and details on how to participate will be available at www.envisionreports.com/LOGC.

When were this proxy statement and the accompanying materials sent to stockholders?

On or about April 29, 2020,27, 2021, we began sending the Important Notice Regarding the Availability of Proxy Materials to all stockholders entitled to vote at the Annual Meeting.

be able to attend the Annual Meeting online and submit questions by visiting www.meetingcenter.io/252372261.Stockholders will also be able to submit questions related to the business of the Annual Meeting and to vote their shares electronically during the Annual Meeting.

How do I attend the Annual Meeting?

Our Annual Meeting will begin promptly at 9:00 a.m. ET in a virtual meeting format at www.meetingcenter.io/252372261. To participate in the Annual Meeting, you will need the 15-digit control number included in your Important Notice Regarding the Availability of Proxy Materials, your proxy card or on the instructions that accompanied your proxy materials. The meeting webcast will begin promptly at 9:00 a.m. ET. We encourage you to access the meeting prior to the start time. Online check-in will start 15 minutes before the meeting, and you should allow ample time for the check-in procedures.

If you hold shares beneficially through a bank, broker or other nominee (that is, in “street name”), you must register to advance to gain access to the Annual Meeting, submit questions and to vote shares during the meeting. To register, you will need to obtain a legal proxy from your bank, broker or other nominee. Once you have received a legal proxy from them, you must submit a copy of this legal proxy, along with your name and email address, to Computershare at legalproxy@computershare.com. Alternatively, you may mail your legal proxy to the following address: Computershare, LogicBio Therapeutics, Inc. Legal Proxy, P.O. Box 43001, Providence, RI 02940-3001. Requests for registration must be labeled as “Legal Proxy” and received no later than 5 p.m. Eastern Time on June 8, 2021. You will receive an email from Computershare confirming your registration and providing your control number. You will need your control number to access the Annual Meeting, submit questions and vote your shares electronically. The password for the meeting is LOGC2021.

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

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

How many votes can be cast by all stockholders?

A total of 23,323,33632,160,459 shares of common stock of the Company were outstanding on April 22, 20202021 and are entitled to be voted at the meeting. Each share of common stock is entitled to one vote on each matter.

What is the difference between being a stockholder of record and a beneficial owner?

Many of our stockholders hold their shares through stockbrokers, banks, or other nominees, rather than directly in their own names. As summarized below, there are some differences between being a stockholder of record and a beneficial owner.

Stockholder of record: If your shares are registered directly in your name with our transfer agent, Computershare Trust Company, N.A., you are the stockholder of record, and these proxy materials are being sent directly to you. As the stockholder of record, you have the right to grant your voting proxy directly to the individuals named on the proxy card and to vote at the Annual Meeting.

Beneficial owner: If your shares are held in a stock brokerage account or by a bank or other nominee, you are the beneficial owner of shares held in “street name,” and these proxy materials are being forwarded to you by your broker or other nominee, who is considered to be the stockholder of record. As the beneficial owner, you have the right to tell your nominee how to vote, and you are also invited to attend the Annual Meeting. However, since you are not the stockholder of record, you may not vote your shares at the Annual Meeting unless you obtain a legal proxy from your nominee authorizing you to do so. Your nominee has sent you instructions on how to direct the nominee’s vote. You may vote by following those instructions and the instructions on the Notice.

How do I vote?

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

-3-

If your shares of common stock are held in street name (that is, held for your account by a broker, bank or other nominee):

How is a quorum reached?

The presence, in persononline or by proxy, of holders of at least a majority of the total number of outstanding shares entitled to vote is necessary to constitute a quorum for the transaction of business at the Annual Meeting. Abstentions and “brokernon-votes” (i.e., shares represented at the meeting held by brokers, bankers or other nominees as to which instructions have not been received from the beneficial owners or persons entitled to vote such shares and, with respect to one or more but not all proposals, such brokers or nominees do not have discretionary voting power to vote such shares), if any, will be counted for purposes of determining whether a quorum is present for the transaction of business at the meeting.

What vote is required to approve each item?

Electronic Delivery of Company Stockholder Communications

Most stockholders can elect to view future proxy materials and annual reports over the Internet instead of receiving paper copies in the mail. You can choose this option and save LogicBio the cost of producing and mailing these documents by following the instructions provided when you vote over the Internet.

-6-

SECURITY OWNERSHIP OF CERTAIN BENEFICIAL OWNERS AND MANAGEMENT

The following table sets forth certain information as of April 10, 20207, 2021 (unless otherwise specified), with respect to the beneficial ownership of our common stock by each person who is known to own beneficially more than 5% of the outstanding shares of common stock, each person currently serving as a director, each nominee for director, each named executive officer (as set forth in the Summary Compensation Table below) and all directors and executive officers as a group. The number of shares beneficially owned by each entity or person is determined in accordance with the rules of the SEC, and the information is not necessarily indicative of beneficial ownership for any other purpose. Under such rules, beneficial ownership includes any shares over which the individual has sole or shared voting power or investment power as well as any shares that the individual has the right to acquire within 60 days of April 10, 20207, 2021 through the exercise of any stock options, warrants or other rights. Except as otherwise indicated, and subject to applicable common property laws, the persons in the table have sole voting and investment power with respect to all shares of common stock held by that person.

Shares of common stock subject to options, warrants or other rights that are now exercisable or are exercisable within 60 days after April 10, 20207, 2021 are considered outstanding for purposes of computing the percentage ownership of the persons holding these options, warrants or other rights but are not to be considered outstanding for the purpose of computing the percentage ownership of any other person. As of April 10, 2020,7, 2021, there were 23,302,66932,082,766 shares of common stock outstanding. Unless otherwise indicated, the address for each beneficial owner is c/o LogicBio Therapeutics, Inc., 65 Hayden Avenue, Floor 2, Lexington, MA 02421.

-7-

MANAGEMENT AND CORPORATE GOVERNANCE

BOARD COMPOSITION AND STRUCTURE

Our amended and restated certificate of incorporation, or our certificate of incorporation, states that the Board of Directors shall consist of not fewer than three and not more than fifteen members, and the precise number of directors shall be fixed by a resolution of the Board of Directors. Each director holds office until his or her successor is duly elected and qualified or until his or her death, resignation or removal. Our certificate of incorporation provides that our directors may be removed only for cause by the affirmative vote of the holders of at least seventy-five percent (75%) of the voting power of the outstanding shares of capital stock of the Company entitled to vote generally in the election of directors, voting together as a single class, at a meeting of the stockholders called for that purpose. Any vacancy in the Board of Directors, including a vacancy that results from an increase in the number of directors, may be filled by a vote of the majority of the directors then in office.

Our certificate of incorporation provides that the Board of Directors is divided into three classes of directors, with the classes as nearly equal in number as possible. Each of our directors identified below serves in the class indicated. Subject to any earlier resignation or removal in accordance with the terms of our certificate of incorporation and amended and restated bylaws, or bylaws, our Class IIIII directors, if elected at the Annual Meeting, will serve until the 20232024 annual meeting of stockholders, our Class III directors will serve until the 2021 annual meeting of stockholders and our Class I directors will serve until the 2022 annual meeting of stockholders and our Class II will serve until the 2023 annual meeting of stockholders. Any additional directorships resulting from an increase in the number of directors will be apportioned by the Board of Directors among the three classes.

The Board of Directors is currently comprised of eight members. Below is a list of the names, ages as of March 31, 20202021 and classification of the individuals who currently serve as our directors.

DIRECTOR BIOGRAPHIES

Information concerning our directors is set forth below. The biographical description of each director includes the specific experience, qualifications, attributes and skills that led to the Board of Directors’ conclusion at the time of filing of this proxy statement that each person listed below should serve as a director.

DIRECTOR NOMINEES (CLASS II DIRECTORS)

Leon Chen, Ph.D. has served as a member of our board of directors since January 2016. Dr. Chen is a partner at The Column Group, a healthcare investment firm, where he has been employed since October 2019. Prior to joining The Column Group, Dr. Chen was a venture partner at OriMed Advisors, a healthcare investment firm, where he had been employed since June 2013. Dr. Chen currently serves on the boards of several privately held life sciences companies. He has a B.A. in biochemistry from U.C. Berkeley, a Ph.D. in molecular pharmacology from Stanford and an M.B.A. from the Stanford Graduate School of Business. We believe that Dr. Chen’s venture capital experience, especially his experience investing in life sciences companies, provides him with the qualifications and skills to serve as a director.

Daniel O’Connell, M.D., Ph.D. has served as a member of our board of directors since June 2017. Since April 2020, Dr. O’Connell has been the executive director, corporate development at Bristol-Myers Squibb Company. From October 2016 until July 2019, Dr. O’Connell served as an investment director of Arix Bioscience, a healthcare and life science company. Previously, from March 2012 to August 2016, Dr. O’Connell served as an associate at OrbiMed Advisors, a healthcare investment firm. He formerly served as a director of PreciThera, Inc., a privately held company, from July 2017 until July 2019.

Richard Moscicki, M.D. has served as a member of our board of directors since October 2018.2018 and as Chair since June 2020. Dr. Moscicki is currently the Executive Vice President for Science and Regulatory Advocacy and the Chief Medical Officer at Pharmaceutical Research and Manufacturers of America, a position he has held since October 2017. Previously, from March 2013 to October 2017, he served as Deputy Center Director for Science Operations for the U.S. Food and Drug Administration’s Center for Drug Evaluation and Research. Since June 2018, Dr. Moscicki has served as a director of Akcea Therapeutics, Inc. (Nasdaq: AKCA), where he is also a member of the nominating and governance committee and the compensation committee. He has also served as a director of KSQ Therapeutics, Inc. since September 2018. He received a B.S. and an M.D. from Northwestern University. We believe Dr. Moscicki is qualified to serve as a member of our board based on his extensive clinical and regulatory experience in the pharmaceutical industry.

Michael Wyzga has served as a member of our board of directors since September 2018. Mr. Wyzga is currently the President of MSW Consulting, Inc., a private company focused on strategic biotechnology consulting, a position he has held since November 2013. Prior to that, Mr. Wyzga served as President and Chief Executive Officer and a member of the Board of Directors of Radius Health, Inc., a publicly traded biopharmaceutical company, from 2011 until November 2013. Prior to that, Mr. Wyzga served in various senior management positions at Genzyme Corporation. Mr. Wyzga joined Genzyme in February 1998 and most recently served as Executive Vice President, Finance from 2003 until 2011 and as chief financial officer from 1999 until 2011. Mr. Wyzga has served as anon-executive director and a member of the audit committee of Mereo BioPharma Group plc (Nasdaq: MREO) since April 2019 and served as a director of OncoMed Pharmaceuticals, Inc. from February 2013 until its merger with Mereo in April 2019. Since February 2015, Mr. Wyzga has also served as a director of Exact Sciences Corporation (Nasdaq: EXAS), where he is also a member of the audit and compensation committees. Mr. Wyzga has served as the chairman of the board of X4 Pharmaceuticals, Inc. (Nasdaq: XFOR) since 2018 and has served as the chairman of the board of GenSight Biologics, a biotechnology company listed in Euronext Paris, since 2017. Mr. Wyzga also previously served as a director of Akebia Therapeutics, Inc. (Nasdaq: AKBA), a publicly traded biotechnology company, from February 2014 until December 2018, Idenix Pharmaceuticals, Inc., a publicly traded biotechnology company that was acquired by Merck (NYSE: MRK) in August 2014, where he also served as the chair of the audit committee and a member of the compensation committee, and as a member of the Supervisory Board of Prosensa Holding B.V., a publicly traded biopharmaceutical company, from June 2014 until its acquisition by BioMarin Falcon B.V. (Nasdaq: BMRN) in December 2014. He received an M.B.A. from Providence College and a B.S. from Suffolk University. We believe Mr. Wyzga’s extensive experience in the biotechnology space, and his financial experience, provide him with the qualifications and skills to serve as a director.

DIRECTORS WITH TERMS EXPIRING IN 2022 (CLASS I DIRECTORS)

Erez Chimovits has served as a member of our board of directors since January 2016. Mr. Chimovits is a senior managing director with OrbiMed, a healthcare investment firm, where he has been employed since 2010. He has more than fourteen years of operational experience, including ten years of senior managerial experience in public companies. Prior to joining OrbiMed, he was the Chief Executive Officer of NasVax Ltd. Previously, Mr. Chimovits spent more than seven years with

Vaccinex, Inc. (Nasdaq: VCNX). Mr. Goater received a B.A. in Biology, an M.S. in Pathology, an M.S. in Microbiology and Immunology and an M.B.A., all from the University of Rochester. We believe that Mr. Goater is qualified to serve on our board of directors due to his executive experience and experience in the life sciences industry.

Mark Kay, M.D., Ph.D., has served as a member of our board of directors since January 2016. Dr. Kay is the Dennis Farrey Family Professor in Pediatrics, and a professor of genetics at Stanford University School of Medicine, where he heads the division of human gene therapy. Dr. Kay moved from the University of Washington to Stanford in 1998, where he has been on the faculty since that time. A founder of the American Society of Gene and Cell Therapy, Dr. Kay served as the society’s president from 2005 to 2006. Dr. Kay also serves as a member of the board of directors of Genevant Sciences. He holds a B.S. in physical science from Michigan State University and an M.D. and Ph.D. from Case Western Reserve University. We believe Dr. Kay is qualified to serve on our board of directors due to his significant expertise regarding our technology platform and his long-standing reputation in the field of gene therapy.

DIRECTORS WITH TERMS EXPIRING IN 2023 (CLASS II DIRECTORS)

Leon Chen, Ph.D., has served as a member of our board of directors since January 2016. Dr. Chen is a partner at The Column Group, a healthcare investment firm, where he has been employed since October 2019. Prior to joining The Column Group, Dr. Chen was a venture partner at OriMed Advisors, a healthcare investment firm, where he had been employed since June 2013. Dr. Chen currently serves on the board of directors of Nurix Therapeutics, Inc. (Nasdaq: NRIX), as well as the boards of several privately held life sciences companies. He has a B.A. in biochemistry from U.C. Berkeley, a Ph.D. in molecular pharmacology from Stanford and an M.B.A. from the Stanford Graduate School of Business. We believe that Dr. Chen’s venture capital experience, especially his experience investing in life sciences companies, provides him with the qualifications and skills to serve as a director.

Daphne Karydas has served as a member of our board of directors since December 2020. Ms. Karydas has served as the Chief Financial Officer of Syndax Pharmaceuticals, Inc., a clinical-stage, biopharmaceutical company, since July 2020. Ms. Karydas previously served as Senior Vice President of Corporate Financial Planning & Analysis and Strategy at Allergan plc, a pharmaceutical company, where she oversaw the company’s long-term financial and business strategy, until its recent acquisition by AbbVie in May 2020. She joined Allergan in April 2017 as Senior Vice President of Global Investor Relations and Strategy, leading engagement with the investment community and business strategy development. Prior to joining Allergan, she served as Executive Director and Senior Healthcare Analyst at J.P. Morgan Asset Management from January 2015 to April 2017. Previously, she was a Portfolio Manager and Senior Healthcare Analyst at The Boston Company Asset Management, a BNY Mellon company. Earlier, Ms. Karydas was a Vice President at Goldman Sachs Asset Management focused on healthcare, as well as a member of Goldman Sachs’ healthcare investment banking team. Before joining Goldman Sachs, she was a Project Chemical Engineer at Merck & Co. where she focused on process development for novel vaccines. Ms. Karydas currently serves on the board of Eucrates Biomedical Acquisition Corp. (Nasdaq: EUCR), as well as on the board of a privately held company. Ms. Karydas received a B.A. and M.S. in chemical engineering from the Massachusetts Institute of Technology and an M.B.A. from Harvard Business School. We believe that Ms. Karydas is qualified to serve on our board of directors due to her financial executive experience and experience in the life sciences industry.

Director Independence

Under Nasdaq Rule 5605, a majority of a listed company’s board of directors must be comprised of independent directors. In addition, Nasdaq rules require that, subject to specified exceptions andphase-in provisions, each member of a listed company’s audit committee, compensation committee and nominating and corporate governance committee be independent and, in the case of the audit committee and compensation committee, satisfy additional independence criteria set forth in Rules10A-3 and10C-1, respectively, under the Securities Exchange Act of 1934, as amended, or the Exchange Act.

Based upon information requested from and provided by each director concerning his or her background, employment and affiliations, including family relationships, our Board of Directors has determined that each of Messrs. Chimovits, Enyedy and Wyzga and Drs. Chen, Kay, Moscicki and O’Connell, representing seven of our eight directors, other than Mr. Chereau, our Chief Executive Officer, is “independent” as that term is defined under Nasdaq Rule 5605(a)(2). Our Board of Directors also determined that each of the current members of our Audit Committee, Compensation Committee and Nominating and Corporate Governance Committee satisfies the independence standards for such committee established by the SEC and Nasdaq rules, as applicable. In making such determination, our Board of Directors considered the relationships that each suchnon-employee director has with the Company and all other facts and circumstances deemed relevant in determining their independence.

-12-

Board Membership Criteria

Our Nominating and Corporate Governance Committee is responsible for developing and recommending to our Board of Directors criteria for Board membership and, consistent with those criteria, recommending to the Board of Directors director candidates and nominees for the next annual meeting of stockholders. As reflected in our Corporate Governance Guidelines, it is the policy of the Board of Directors that all directors should possess the highest personal and professional ethics, integrity and values, and be committed to representing the long-term interests of the Company’s stockholders. The Board of Directors believes that each director should possess the requisite ability, judgment and experience to oversee the Company’s business, and should contribute to the overall diversity of the Board of Directors. The Board of Directors considers the qualifications of directors and director candidates individually and in the broader context of its overall composition and the Company’s current and anticipated future needs. In particular, the Board of Directors considers diversity of background and experience, as well as ethnicity, gender and other forms of diversity. Stockholders may also nominate persons to be elected as directors in accordance with our bylaws and applicable law, as described under “General Matters—Stockholder Proposals and Nominations.” The Nominating

the Audit Committee discusses LogicBio’s major financial risk exposures and steps that management has taken to monitor and control such exposures. In addition, the Audit Committee has established procedures for the receipt, retention and treatment of complaints received by the Company regarding accounting, internal accounting controls or auditing matters, and the confidential, anonymous submissions by employees of concerns regarding questionable accounting or accounting matters. See “Risks Related to Compensation Practices and Policy” below for information related to the Compensation Committee’s oversight of compensation-related risks.

Because of the role of the Board of Directors and its committees in risk oversight, the Board of Directors believes that any leadership structure that it adopts must allow it to effectively oversee the management of the risks relating to LogicBio’s operations. The Board of Directors acknowledges that there are different leadership structures that could allow it to effectively oversee the management of the risks relating to the Company’s operations, but it believes its current leadership structure enables it to effectively provide oversight with respect to such risks.

During the year ended December 31, 2019,2020, the Audit Committee met five times. The report of the Audit Committee is included in this proxy statement under “Audit Committee Report.”

While members of ourThe Nominating and Corporate Governance Committee informally consulted with our chief executive officer on matters related to the committee’s responsibilities, such as the review of new potential director candidates, and took certain actions by unanimous written consent, it did not formally meetmet once during the year ended December 31, 2019.2020.

In determining to engage Arnosti Consulting, the Compensation Committee considered its independence, taking into consideration relevant factors, including the absence of other services provided to the Company, the amount of fees the Company paid to Arnosti Consulting as a percentage of its respective total revenue, Arnosti Consulting’s policies and procedures that are designed to prevent conflicts of interest, any business or personal relationship any individual compensation advisor has with an executive officer of the Company, any business or personal relationship any individual compensation advisor has with any member of the Compensation Committee and any stock of the Company owned by Arnosti Consulting or its individual compensation advisors. The Compensation Committee determined, based on its analysis in light of all relevant factors, including the factors listed above, that the work of Arnosti Consulting and its individual

Code of Business Conduct and Ethics and Corporate Governance Guidelines

We have adopted a Code of Business Conduct and Ethics that applies to all of our employees, officers and directors, including those officers responsible for financial reporting. A copy of our Code of Business Conduct and Ethics may be accessed free of charge by visiting our website at www.logicbio.com and going to the “Corporate Governance” tab under the “Investors” section, or by requesting a copy in writing from our Corporate Secretary at our Lexington, Massachusetts office. We intend to

EXECUTIVE COMPENSATION

Introduction

This section provides an overview of our compensation arrangements with our principal executive officer and our next two most highly compensated executive officers and, as required by SEC rules, one of our former executive officers, in all cases, in respect of their service to us in 2019.2020. These individuals, who we refer to as our “named executive officers,” are:

Summary Compensation Table

The following table sets forth the compensation awarded to, earned by, or paid to our named executive officers in respect of their service to us during 20192020 and, if applicable, 2018.2019.

-20-

Dr. Chiang’s death or disability or if Dr. HuttnerChiang resigns for good reason, he will be entitled to receive base salary continuation for six months, an amount equal to .50.5 times his target annual bonus, payable in installments over six months, and reimbursement of COBRA premiums for up to three months. If his employment terminates under such circumstances within 24 months following a change of control, Dr. HuttnerChiang will be entitled to receive a lump sum payment equal to one times the sum of his annualnine months’ base salary and target annual bonus, an amount equal to the monthly COBRA premium he would be required to pay to continue group health coverage for ninesix months, and accelerated vesting of all of his then outstanding and unvested equity and equity-based awards (with any performance-vesting awards vesting at target). All of the foregoing severance benefits are conditioned upon Dr. Huttner’sChiang’s execution of a separation agreement and an effective release of claims and his compliance with the restrictive covenants described below.

Equity Compensation

On February 11, 2020, Mr. Chereau, Dr. Chiang and Mr. Yoon were granted options to purchase 222,000, 28,921 and 95,000 shares of our common stock, respectively. These options vest as to 25% of the shares on January 1, 2021, and in monthly installments over thirty-six months thereafter, generally subject to the named executive officer’s continued service through the applicable vesting date. Mr. Yoon’s 2020 stock option grant was forfeited upon his termination of employment in November 2020.

As an additional retention incentive in light of the temporary salary reductions described above, on April 15, 2020, Mr. Chereau, Dr. Chiang and Mr. Yoon were granted restricted stock units (“RSUs”) with respect to 23,414, 9,360 and 17,445 shares of our common stock, respectively. Mr. Chereau’s and Dr. Chiang’s RSUs vested in full on April 15, 2021, based on the named executive officer’s continued service through the vesting date. Mr. Yoon’s RSUs were forfeited upon his termination of employment in November 2020.

In connection with hisher commencement of employment with us on December 11, 2019, Mr. YoonNovember 30, 2020, Dr. Nacht was granted an option to purchase 110,0000200,000 shares of our common stock. In connection with his commencement of employment with us,promotion to Chief Operating Officer on February 20, 2019,November 2, 2020, Dr. HuttnerChiang was granted an option to purchase 50,81885,000 shares of our common stock. These options vest as to 25% of the shares on the first anniversary of the option’s vesting commencement date and in monthly installments overthirty-six 36 months thereafter, generally subject to the named executive officer’s continuing service through the applicable vesting date. Mr. Chereau was not granted any equity awards in 2019.

On February 11, 2020, Messrs. Chereau and Yoon and Dr. Huttner were granted options to purchase 222,000, 95,000 and 50,000 shares of our common stock, respectively. These options vest as to 25% of the shares on January 1, 2021 and in monthly installments overthirty-six months thereafter, generally subject to the named executive officer’s continuingcontinued service through the applicable vesting date.

As an additional retention incentive, on April 15, 2020, Messrs. Chereau and Yoon and Dr. Huttner were granted restricted stock units (“RSUs”) with respect to 23,414, 17,445 and 5,000 shares of our common stock, respectively. These RSUs will vest in full on April 15, 2021, subject to the named executive officer’s continuing service through the vesting date; except that if such named executive officer’s employment is terminated by us without “cause” or by the named executive officer for “good reason” prior to April 15, 2021, such named executive officer’s RSUs will vest in full on the date of such termination.

Severance and Change of Control Payments and Benefits

Messrs.Mr. Chereau and YoonDrs. Nacht and Dr. HuttnerChiang are each entitled to severance payments and benefits under histheir respective employment agreementagreements upon a termination of employment in certain circumstances, including in connection with a change of control. These severance payments and benefits are described under “Agreements with our Named Executive Officers” above and “Outstanding Equity Awards at Fiscal-Year End Table” below. Each of their employment agreements provideprovides that if any payment or benefit provided under such agreement constitutes a “parachute payment” within the meaning of Section 280G of the Code, the named executive officer will be entitled to receive (i) the amount of such payments or benefits reduced so that

-24-

-25-

DIRECTOR COMPENSATION

UnderIn connection with our initial public offering in 2018, our Board of Directors adopted a non-employee director compensation policy. Following our initial public offering, our compensation committee, in consultation with our independent compensation consultant, reviewed our non-employee director compensation program. Following this review, our compensation committee recommended, and our Board of Directors approved, a change to our non-employee director compensation policy, effective for 2020, to provide for a fixed number of shares, rather than a fixed grant date value, to be used for initial and annual director equity awards. No changes were made to cash compensation in connection with this review. The following summary describes the material terms of our non-employee director compensation policy in effect during 2019, which2020.

Under our Board of Directors adoptednon-employee director compensation policy, as in connection with our initial public offering,effect during 2020, eachnon-employee director received an annual cash retainer for service to our Board of Directors and an additional annual cash retainer for service on any committee of our Board of Directors or for serving as the chair of our Board of Directors or any of its committees, in each case, prorated for partial years of service, as follows:

Our BoardIn April 2020, in light of Directors electedthe COVID-19 pandemic, our non-employee directors agreed to maintaintemporarily forego their cash compensation. Cash compensation was restored in October 2020, but our non-employee directors were not repaid the annualforegone cash retainer at the same levels for 2020.compensation.

OurFor 2020, our non-employee director compensation policy in effect during 2019 provided that anynon-employee director who is first elected to our Board of Directors will be granted an option to purchase shares of our common stock having a grant date fair value of $175,000. For 2020, ournon-employee director compensation policy provides that anynon-employee director first elected to our Board of Directors will bewas granted an option to purchase 20,000 shares of our common stock. Option granted to astock and that each non-employee director who is first elected to our Board of Directors will vest in equal annual installments over three years or upon an earlier change in control, subject to thenon-employee director’s continued service through the applicable vesting date.

Thenon-employee director compensation policy in 2019 also provides that eachnon-employee director who has served on our Board of Directors for more than six months at the time of the first meeting of our Board of Directors following the annual meeting of our stockholders will bewas granted at such board meeting an option to purchase shares of our common stock having a grant date fair value of $87,500. For 2020, anynon-employee director who has served on our Board of Directors for more than six months at the time of the annual meeting of stockholders will be granted an option to purchase 10,000 shares of our common stock onstock. The initial option grants vest in equal annual installments over three years and the date our annual meeting of stockholders is held. Any such option granted to anon-employee director willgrants vest in full on the earlier of the first anniversary of the date of grant or the date of the following annual meeting of our stockholders with prorated accelerated vesting(or, in either case, upon aan earlier change in control prior to such date, in each case,(on a prorated basis for the annual option grant)), subject to thenon-employee director’s continued service through the applicable vesting date. On December 19, 2019,In addition, in order to compensate them for the forgone cash compensation described above, in April 2020 each of ournon-employee directors receivedwas granted an option to purchase 10,869 shares of our common stock atRSU award with a price per share of $12.65. These options vest 100% on the earlier of July 15, 2020 or the 2020 Annual Meeting of Stockholders, or upon an earlier change in control, subject to thenon-employee director’s continued service through the applicable vesting date.

All options granted to ournon-employee directors have a per share exercise price at leastgrant date value approximately equal to the fair market value of a share of our common stockforegone cash compensation, which RSU awards vested in full on the date of grant and expire not later than ten years after the date of grant. January 1, 2021.

All cash retainers are paid quarterly, in arrears, or upon the earlier resignation or removal of thenon-employee director. For the calendar quarter during which anon-employee director is newly elected or appointed to our board, all cash retainers are prorated based on the number of calendar days served by suchnon-employee director following his or her election or appointment.

Eachnon-employee director is also entitled to reimbursement for reasonable travel and other expenses incurred in connection with attending meetings of our board of directors and any committee on which he or she serves.

-26-

The following table sets forth a summary of the compensation we paid to ournon-employee directors during 2019.2020. Mr. Chereau, our President and Chief Executive Officer, receives no compensation for his services as a director and, as a result, is not included in the table below. The compensation received by Mr. Chereau in 20192020 for his services as an employee is described in the “Summary Compensation Table” above and the accompanying narrative description.

-27-

Consulting Agreement with Dr. Kay

We entered into a consulting agreement with Dr. Kay on April 1, 2018, pursuant to which he agreed to continue to provide consulting services to us on anas-requested basis. Under this agreement, Dr. Kay is entitled to receive $67,500 per year in consulting fees and an additional $5,000 for every Scientific Advisory Board meeting that he attends in person. Dr. Kay also agreed to certain covenants regarding confidential information and invention assignment, as well as a covenant not to solicit our employees during the term of the agreement and for one year thereafter.

-28-

AUDIT COMMITTEE REPORT

The Audit Committee has reviewed the audited consolidated financial statements of LogicBio for the year ended December 31, 2019,2020, and has discussed these statements with management and Deloitte & Touche LLP, or Deloitte, the Company’s independent registered public accounting firm. LogicBio management is responsible for preparing the Company’s financial statements and for maintaining an adequate system of disclosure controls and procedures and internal control over financial reporting for that purpose. The independent registered public accounting firm audits the annual consolidated financial statements prepared by management, expresses an opinion as to whether those consolidated financial statements present fairly the consolidated financial position, results of operations and cash flows of LogicBio in conformity with U.S. generally accepted accounting principles and discusses any issues it believes should be raised with us. The Audit Committee is responsible for providing independent, objective oversight of the Company’s accounting functions and internal controls. The Audit Committee also reviewed management’s report on its assessment of the effectiveness of the Company’s internal control over financial reporting as of December 31, 2019.2020.

The Audit Committee also received from, and discussed with, Deloitte the written disclosures and other communications that the Company’s independent registered public accounting firm is required to provide to the Audit Committee, including the matters required to be discussed by the applicable requirements of the Public Company Accounting Oversight Board, or PCAOB, and the Securities and Exchange Commission.

Deloitte also provided the Audit Committee with the written disclosures and the letter required by Rule 3526 of the PCAOB. PCAOB Rule 3526 requires independent registered public accounting firms annually to disclose in writing all relationships that in their professional opinion may reasonably be thought to bear on independence, to confirm their perceived independence and engage in a discussion of independence. The Audit Committee has reviewed this disclosure and has discussed with Deloitte its independence from LogicBio.

Based on its discussions with management and Deloitte, and its review of the representations and information provided by management and Deloitte, the Audit Committee recommended to the Board of Directors that the audited consolidated financial statements be included in the LogicBio Annual Report on Form10-K for the year ended December 31, 2019,2020, for filing with the Securities and Exchange Commission.

The Audit Committee of LogicBio Therapeutics, Inc.

Michael Wyzga, Chair

Leon Chen

Mark Enyedy

Audit Fees. Consist of aggregate fees for professional services provided in connection with the annual audit of our consolidated financial statements, the review of our quarterly condensed consolidated financial statements, consultations on accounting matters directly related to the audit, and comfort letters, consents and assistance with and review of documents filed with the SEC.

Audit-Related Fees. Refer to aggregate fees for accounting consultations and other services that were reasonably related to the performance of audits or reviews of our consolidated financial statements and were not reported above under “Audit Fees.”

Tax Fees. Consist of aggregate fees for tax compliance, tax advice and tax planning services including the review and preparation of our federal and state income tax returns.

All Other Fees. Consist of aggregate fees billed for products and services provided by the independent registered public accounting firm other than those disclosed above.

The Audit Committeepre-approved all services performed since thepre-approval policy was adopted.

Policy on Audit CommitteePre-Approval of Audit and PermissibleNon-Audit Services of Independent Registered Public Accounting Firm

The Audit Committeepre-approves all auditing services, internal control related services and permittednon-audit services (including the fees and terms thereof) to be performed by Deloitte, subject to thede minimis exception fornon-audit services that are approved by the Audit Committee prior to the completion of an audit. The Audit Committee may delegatepre-approval authority to one or more members of the Audit Committee consistent with applicable law and listing standards, provided that the decisions of such Audit Committee member or members must be communicated to the Audit Committee at its next scheduled meeting.

-30-

DELINQUENT SECTION 16(A) REPORTS

Section 16(a) of the Exchange Act requires the Company’s directors and executive officers and persons who beneficially own more than 10% of the Company’s common stock to file with the SEC reports showing ownership of and changes in ownership of the Company’s common stock and other equity securities. On the basis of information submitted by the Company’s directors and executive officers, the Company believes that its directors, executive officers and persons who beneficially own more than 10% of the Company’s common stock timely filed all required Section 16(a) filings for fiscal year 2020, except that (i) Arix Bioscience plc filed a late Form 4 on October 5, 2020 in connection with sales of common stock made in July, August and September 2020 and (ii) Mr. Chiang filed one late Form 4 on November 12, 2020 in connection with a grant of an option to purchase shares of common stock on November 2, 2020.

CERTAIN RELATIONSHIPS AND RELATED PARTY TRANSACTIONS

Except as described below, there have been no transactions since January 1, 2019 in which we were a party, the amount involved exceeded or will exceed $120,000 or one percent of the average of the Company’s total assets at year end for the last two completed fiscal years, and in which any related person had a direct or indirect material interest.

Indemnification Agreements and Directors’ and Officers’ Liability Insurance

We have entered into indemnification agreements with each of our directors and executive officers. We also maintain a general liability insurance policy, which covers certain liabilities of directors and officers of the Company arising out of claims based on acts or omissions in their capacities as directors or officers.

Related Person Transactions Policy

We have adopted a related person transactions policy that governs the review and approval of related person transactions. Pursuant to this policy, if we want to enter into a transaction with any of our executive officers, directors, director nominees, beneficial owners of more than 5% of our common stock or immediate family members of any of the foregoing, the Audit Committee will review all of the material facts of the proposed transaction and either approve or disapprove of such transaction. If advance approval by the Audit Committee of such a transaction is not feasible, such matter will be reviewed and, if the Audit Committee determines it to be appropriate, ratified at the next regularly scheduled meeting of the Audit Committee. In determining whether to approve or ratify a related person transaction, the Audit Committee will take into account, among other factors it deems appropriate, whether such transaction is on terms no less favorable than terms generally available to an unaffiliated third party under the same or similar circumstances and the extent of the related person’s interest in the transaction.

-31-

PROPOSAL NO. 1—ELECTION OF DIRECTORS

In accordance with the Company’s certificate of incorporation and bylaws, the Board of Directors is divided into three classes. The members of each class are elected to serve a three-year term with the term of office of each class ending in successive years. Leon ChenFrederic Chereau, Richard Moscicki and Daniel O’ConnellMichael Wyzga are the Class IIIII directors whose terms expire at the 20202021 Annual Meeting of Stockholders. Drs. ChenMessrs. Chereau, Moscicki and O’ConnellWyzga have each been nominated for and have agreed to stand for election to the Board of Directors to serve as a Class IIIII director of the Company for three years and until his successor is duly elected and qualified or until his earlier death, resignation or removal.

Our bylaws provide for a majority voting standard for the election of directors in an uncontested election. Accordingly, a director nominee will be elected at the Annual Meeting only if the votes properly cast FOR his election exceed the votes properly cast AGAINST his election.

It is intended that, unless you give contrary instructions, shares represented by proxies will be voted FOR the election of the nominees listed. LogicBio has no reason to believe that the nominees will be unable to serve. In the event that the nominees are unexpectedly not available to serve, proxies may be voted for another person nominated as a substitute by the Board of Directors, or the Board of Directors may determine that no directors are to be elected at the Annual Meeting. Information relating to the nominees for election as directors and for each continuing director, including his period of service as a director of LogicBio, principal occupation and other biographical material is shown earlier in this proxy statement.

THE BOARD OF DIRECTORS UNANIMOUSLY RECOMMENDS THAT YOU VOTE “FOR” THE NOMINEES FOR CLASS IIIII DIRECTORS.

-32-

PROPOSAL NO. 2—RATIFICATION OF SELECTION OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

We are asking our stockholders to ratify the Audit Committee’s selection of Deloitte & Touche LLP, or Deloitte, as our independent registered public accounting firm for the fiscal year ending December 31, 2020.2021. Deloitte has served as our independent registered public accounting firm since 2019.2018.

The Audit Committee annually reviews the independent registered public accounting firm’s independence, including reviewing all relationships between the independent registered public accounting firm and us and any disclosed relationships or services that may impact the objectivity and independence of the independent registered public accounting firm, and the independent registered public accounting firm’s performance. Although ratification is not required by our bylaws or otherwise, the Board of Directors is submitting the selection of Deloitte to our stockholders for ratification as a matter of good corporate practice. If the selection is not ratified, the Audit Committee will consider whether it is appropriate to select another independent registered public accounting firm. Even if the selection is ratified, the Audit Committee in its discretion may select a different registered public accounting firm at any time during the year if the committee determines that such a change would be in the best interests of the Company and our stockholders.

We expect that a representative of Deloitte will attend the Annual Meeting and the representative will have an opportunity to make a statement if he or she so chooses. The representative will also be available to respond to appropriate questions from stockholders.

THE BOARD OF DIRECTORS UNANIMOUSLY RECOMMENDS THAT YOU VOTE “FOR” THE RATIFICATION OF THE SELECTION OF DELOITTE & TOUCHE LLP AS THE COMPANY’S INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM FOR THE FISCAL YEAR ENDING DECEMBER 31, 2020.2021.

-33-

GENERAL MATTERS

Availability of Certain Documents

A copy of our 20192020 Annual Report on Form10-K has been posted on the Company’s website (www.logicbio.com) along with this proxy statement. Upon written request, we will mail, without charge, a copy of our 20192020 Annual Report on Form10-K, excluding exhibits. Please send a written request to our Corporate SecretaryChief Financial Officer at:

LogicBio Therapeutics, Inc.

65 Hayden Avenue, Floor 2

Lexington, MA 02421

Attention: Corporate SecretaryChief Financial Officer

Phone: (617)245-0399

SEC rules concerning the delivery of annual disclosure documents allow us or your broker to send a single notice or, if applicable, a single set of our proxy materials to any household at which two or more of our stockholders reside, if we or your broker believe that the stockholders are members of the same family, unless we have received contrary instructions from one or more of the stockholders. This practice, referred to as “householding,” benefits both you and us. It reduces the volume of duplicate information received at your household and helps to reduce our expenses. The rule applies to our notices, annual reports, proxy statements and information statements.

We will undertake to deliver promptly, upon written or oral request, a separate copy to a stockholder at a shared address to which a single copy of the notice or proxy materials was delivered. You may make a written or oral request by sending a notification to our Corporate Secretary at the address or telephone number above, providing your name, your shared address, and the address to which we should direct the additional copy of the notice or proxy materials. Multiple stockholders sharing an address who have received one copy of a mailing and would prefer us to mail each stockholder a separate copy of future mailings should contact us at our principal executive offices. Additionally, if current stockholders with a shared address received multiple copies of a mailing and would prefer us to mail one copy of future mailings to stockholders at the shared address, notification of that request may also be made through our principal executive offices. Stockholders who participate in householding will continue to have access to and utilize separate proxy voting instructions.

Stockholder Proposals and Nominations

Requirements for Stockholder Proposals to be Considered for Inclusion in our Proxy Materials. To be considered for inclusion in next year’s proxy statement, stockholder proposals pursuant to Rule14a-8 under the Exchange Act must be received by our Corporate SecretaryChief Financial Officer at our principal executive offices no later than the close of business on December 30, 2020,28, 2021, which is 120 days prior to the date that is one year from April 29, 2020,27, 2021, the date this year’s proxy statement was released to shareholders.

Requirements for Stockholder Proposals or Director Nominations to be Brought Before an Annual Meeting. Our bylaws provide that, for stockholder nominations to the Board of Directors or other proposals to be considered at an annual meeting, the stockholder must have given timely notice thereof in writing to the Corporate Secretary at LogicBio Therapeutics, Inc., 65 Hayden Avenue, Floor 2, Lexington, MA 02421. To be timely for the 20212022 annual meeting, although not included in the proxy statement, the stockholder’s notice must be delivered to or mailed and received by us not earlier than the close of business on the 120th day nor later than the close of business on the 90th day prior to the anniversary date of the prior year’s annual meeting, except that if the annual meeting is set for a date that is not within 30 days before or after such anniversary date, we must receive the notice not later than the close of business on the tenth day following the day on which we first provide notice or public disclosure of the date of the meeting. Assuming the date of our 20202021 annual meeting is not so advanced or delayed, stockholders who wish to make a proposal at the 20212022 annual meeting must notify us no earlier than February 19, 202111, 2022 and no later than March 21, 2021.13, 2022. Such notice must provide the information required by our bylaws with respect to each matter the stockholder proposes to bring before the 2021 annual meeting.

-34-

Contacting the Board of Directors

Stockholders wishing to communicate with the Board of Directors may do so by writing to the Board or to thenon-employee members of the Board as a group, at:

LogicBio Therapeutics, Inc.

65 Hayden Avenue, Floor 2

Lexington, MA 02421

Attention: Corporate SecretaryChief Financial Officer

The communication must prominently display the legend “BOARD COMMUNICATION” in order to indicate to the Corporate SecretaryChief Financial Officer that it is a communication for the Board. Upon receiving such a communication, the Corporate SecretaryChief Financial Officer will promptly forward the communication to the relevant individual or group to which it is addressed. Certain items that are unrelated to the Board’s duties and responsibilities may be excluded. The Corporate SecretaryChief Financial Officer will not forward any communication determined in his good faith belief to be frivolous, unduly hostile, threatening, illegal or similarly unsuitable.

Other Matters

As of the date of this proxy statement, the Board of Directors does not intend to present any matters other than those described herein at the Annual Meeting and is unaware of any matters to be presented by other parties. If other matters are properly brought before the meeting for action by the stockholders, proxies will be voted in accordance with the recommendation of the Board or, in the absence of such a recommendation, in accordance with the judgment of the proxy holder.

-35-

01 Leon Chen 02 Daniel O’Connell For Against Abstain For Against AbstainENDORSEMENT LINE
SACKPACK
MR A SAMPLE
DESIGNATION (IF ANY)
ADD 1
ADD 2 1 B M
ADD 3
ADD 4
ADD 5
ADD 6
Your vote matters – here’s how to vote!
You may vote online or by phone instead of mailing this card.
Online
Go to www.envisionreports.com/LOGC or scan the QR code — login details are located in the shaded bar below.
Phone
Call toll free 1-800-652-VOTE (8683) within the USA, US territories and Canada
Save paper, time and money! Sign up for electronic delivery at www.envisionreports.com/LOGC
Using a black ink pen, mark your votes with an X as shown in this example. Please do not write outside the designated areas. 039AOB
2021 Annual Meeting Proxy Card 1234 5678 9012 345
qIF VOTING BY MAIL, SIGN, DETACH AND RETURN THE BOTTOM PORTION IN THE ENCLOSED ENVELOPE. q
A Proposals — The Board of Directors recommend a vote FOR all the nominees listed in A Proposal 1 and FOR Proposal 2.
1. Election of Class III Directors for a three-year term:
For Against Abstain For Against Abstain For Against Abstain
01 - Frederic Chereau 02 - Richard Moscicki 03 - Michael Wyzga
For Against Abstain
2. To ratify the selection of Deloitte & Touche LLP as the independent registered public accounting firm for the Company for the fiscal year ending December 31, 2020. 1. Election of Class II Directors2021.
B Authorized Signatures — This section must be completed for a three-year term: For Against Abstain your vote to count. Please date and sign below.
Please sign exactly as name(s) appears hereon. Joint owners should each sign. When signing as attorney, executor, administrator, corporate officer, trustee, guardian, or custodian, please give full title.
Date (mm/dd/yyyy) — Please print date below. Signature 1 — Please keep signature within the box. Signature 2 — Please keep signature within the box. B Authorized Signatures This section
C 1234567890 J N T MR A SAMPLE (THIS AREA IS SET UP TO ACCOMMODATE
140 CHARACTERS) MR A SAMPLE AND MR A SAMPLE AND
MR A SAMPLE AND MR A SAMPLE AND MR A SAMPLE AND
31BM 502193 MR A SAMPLE AND MR A SAMPLE AND MR A SAMPLE AND
03GBOB

The 2021 Annual Meeting of Stockholders of LogicBio Therapeutics, Inc. will be held on Friday, June 11, 2021, at 9:00 a.m. E.T., virtually via the internet at www.meetingcenter.io/252372261.
To access the virtual meeting, you must be completedhave the information that is printed in the shaded bar located on the reverse side of this form.
The password for your votethis meeting is — LOGC2021.
Important notice regarding the Internet availability of proxy materials for the Annual Meeting of Stockholders. The material is available at: www.envisionreports.com/LOGC
Small steps make an impact.
Help the environment by consenting to count. Please date andreceive electronic delivery, sign below. Q up at www.envisionreports.com/LOGC
IF VOTING BY MAIL, SIGN, DETACH AND RETURN THE BOTTOM PORTION IN THE ENCLOSED ENVELOPE. Q 2020 Annual Meeting
Proxy Card 000004 MR A SAMPLE DESIGNATION (IF ANY) ADD 1 ADD 2 ADD 3 ADD 4 ADD 5 ADD 6 ENDORSEMENT LINE SACKPACK 1234 5678 9012 345 MMMMMMMMM MMMMMMMMMMMMMMM 4 6 0 8 6 8 MR A SAMPLE (THIS AREA IS SET UP TO ACCOMMODATE 140 CHARACTERS) MR A SAMPLE AND MR A SAMPLE AND MR A SAMPLE AND MR A SAMPLE AND MR A SAMPLE AND MR A SAMPLE AND MR A SAMPLE AND MR A SAMPLE AND C 1234567890 J N T C123456789 MMMMMMMMMMMM MMMMaMMM 000000000.000000 ext 000000000.000000 ext 000000000.000000 ext 000000000.000000 ext 000000000.000000 ext 000000000.000000 ext If no electronic voting, delete QR code and control You may vote online or by phone instead of mailing this card. Online Go to www.envisionreports.com/LOGC or scan the QR code login details are located in the shaded bar below. Save paper, time and money Sign up for electronic delivery at www.envisionreports.com/LOGC Phone Call toll free 1-800-652-VOTE (8683) within the USA, US territories and Canada Votes submitted electronically must be received by 11:59 p.m., Eastern Time, on June 18, 2020. Your vote matters here’s how to vote