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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.    )

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Check the appropriate box:

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GENERATION BIO CO.

(Name of Registrant as Specified In Its Charter)

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

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Payment of Filing Fee (Check the appropriate box):

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GENERATION BIO CO.

301 Binney Street

Cambridge, MA 02142

NOTICE OF 2023 ANNUAL MEETING OF STOCKHOLDERS

To be held June 8, 2023

You are cordially invited to attend the 2023 Annual Meeting of Stockholders, or the Annual Meeting, of Generation Bio Co., which is scheduled to be held on Thursday, June 8, 2023 at 9:00 a.m. Eastern time. We have determined that the Annual Meeting will be held in a virtual meeting format only, via the Internet, with no physical in-person meeting. At our virtual Annual Meeting, stockholders will be able to attend, vote and submit questions by visiting www.virtualshareholdermeeting.com/GBIO2023. Further information about how to attend the Annual Meeting online, vote your shares during the meeting and submit questions during the meeting is included in the accompanying proxy statement.

Only stockholders who owned common stock at the close of business on April 12, 2023 can vote at the Annual Meeting or any adjournment or postponement that may take place. At the Annual Meeting, the stockholders will consider and vote on the following matters:

1.Election of four Class III directors to our board of directors, each to serve until the 2026 annual meeting of stockholders;

2.Ratification of the appointment of Ernst & Young LLP as our independent registered public accounting firm for the fiscal year ending December 31, 2023;

3.Approval of an amendment to our restated certificate of incorporation to reflect new Delaware law provisions regarding officer exculpation;

4.Approval, on an advisory (non-binding) basis, of the compensation of our named executive officers; and

5.Transaction of any other business properly brought before the Annual Meeting or any adjournment or postponement of the Annual Meeting.

You can find more information, including the nominees for directors, in the attached proxy statement. The board of directors recommends that you vote in favor of each of proposals one through four as outlined in the attached proxy statement.

Instead of mailing a printed copy of our proxy materials to all of our stockholders, we are providing access to these materials via the Internet. This reduces the amount of paper necessary to produce these materials as well as the costs associated with mailing these materials to all stockholders. Accordingly, on or about April 26, 2023, we will begin mailing a Notice of Internet Availability of Proxy Materials, or Notice, to all stockholders of record on our books at the close of business on April 12, 2023, the record date for the Annual Meeting, and we will post our proxy materials on the websites referenced in the Notice. As more fully described in the Notice, stockholders may choose to access our proxy materials on the websites referenced in the Notice or may request to receive a printed set of our proxy materials. The Notice and websites provide information regarding how you may request to receive proxy materials in printed form by mail, or electronically by email, for the Annual Meeting and on an ongoing basis.

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If you are a stockholder of record, you may vote in one of the following ways:

If your shares are held in “street name,” that is, held for your account by a bank, broker or other nominee or custodian, you should receive instructions from the bank, broker or nominee or custodian that you must follow for your shares to be voted.

Beginning on May 26, 2023, a complete list of stockholders of record will be made available for examination by stockholders of record at our corporate headquarters at 301 Binney Street, Cambridge, MA 02142 and at www.virtualshareholdermeeting.com/GBIO2023.

Whether or not you plan to attend the Annual Meeting online, we urge you to take the time to vote your shares.

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Cambridge, MA

April 26, 2023

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Generation Bio Co.

Proxy Statement

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GENERATION BIO CO.

301 Binney Street

Cambridge, MA 02142

(617) 655-7500

PROXY STATEMENT

FOR THE 2023 ANNUAL MEETING OF STOCKHOLDERS

to be held June 8, 2023

This proxy statement and the proxy card contain information about the Annual Meeting of Stockholders of Generation Bio Co., or the Annual Meeting, to be held on Thursday, June 8, 2023 at 9:00 a.m. Eastern time. We have determined that the Annual Meeting will be held in a virtual meeting format only, via the Internet, with no physical in-person meeting. At our virtual Annual Meeting, stockholders will be able to attend, vote and submit questions by visiting www.virtualshareholdermeeting.com/GBIO2023. Further information about how to attend the Annual Meeting online, vote your shares during the meeting and submit questions during the meeting is included in this proxy statement.

The board of directors of Generation Bio Co. is using this proxy statement to solicit proxies for use at the Annual Meeting. In this proxy statement, unless expressly stated otherwise or the context otherwise requires, the use of “Generation Bio,” “the company”, “our,” “we” or “us” refers to Generation Bio Co. and its wholly owned subsidiary. References to our website are inactive textual references only and the contents of our website are not incorporated by reference into this proxy statement.

Important Notice Regarding the Availability of Proxy Materials for

the Annual Meeting of Stockholders to be Held on June 8, 2023:

This proxy statement and our 2022 Annual Report to Stockholders are

available for viewing, printing and downloading at http://www.proxyvote.com.

You may also access this proxy statement and our 2022 Annual Report to Stockholders on the

“Investor Center” section on our website, which is located at http://www.generationbio.com

or on the SEC’s website at http://www.sec.gov.

A copy of our Annual Report on Form 10-K for the fiscal year ended December 31, 2022, or 2022 Annual Report, as filed with the Securities and Exchange Commission, or SEC, except for exhibits, will be furnished without charge to any stockholder upon written request to Generation Bio Co., 301 Binney Street, Cambridge, MA 02142. The 2022 Annual Report is also available on the SEC’s website at http://www.sec.gov.

On or about April 26, 2023, we will begin mailing a Notice of Internet Availability of Proxy Materials, or Notice, to all stockholders of record (other than those who previously requested electronic or paper delivery of proxy materials), directing stockholders to a website where they can access our proxy materials, including this proxy statement, a proxy card and our 2022 Annual Report to Stockholders, and view instructions on how to vote online or by telephone. If you would prefer to receive a paper copy of our proxy materials, please follow the instructions included in the Notice. If you have previously elected to receive our proxy materials electronically, you will continue to receive access to those materials via e-mail unless you elect otherwise.

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IMPORTANT INFORMATION ABOUT THE ANNUAL MEETING AND VOTING

Purpose of the Annual Meeting

At the Annual Meeting, our stockholders will consider and vote on the following matters:

As of the date of this proxy statement, we are not aware of any business to come before the Annual Meeting other than the first four items noted above.

Board of Directors Recommendations

Our board of directors unanimously recommends that you vote:

FOR the election of the four nominees to serve as Class III directors on our board of directors for a three-year term;

FOR the ratification of the appointment of Ernst & Young LLP as our independent registered public accounting firm for the fiscal year ending December 31, 2023;

FOR the approval of an amendment to our restated certificate of incorporation to reflect new Delaware law provisions regarding officer exculpation; and

FOR the approval, on an advisory (non-binding) basis, of the compensation of our named executive officers.

Availability of Proxy Materials

The Notice regarding our proxy materials, which include this proxy statement and our 2022 Annual Report to Stockholders, is being mailed to stockholders beginning on or about April 26, 2023. Our proxy materials are also available for viewing, printing and downloading on the Internet at http://www.proxyvote.com or on the SEC’s website at http://www.sec.gov.

Who Can Vote at the Annual Meeting

Only holders of our common stock as of the close of business on the record date of April 12, 2023, or the Record Date, are entitled to receive notice of the Annual Meeting and to vote the shares of our common stock that they held on that date. As of the Record Date, there were 65,542,256 shares of common stock outstanding. Each share of common stock is entitled to one vote on each matter properly brought before the Annual Meeting.

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Difference between a “stockholder of record” and a beneficial owner of shares held in “street name”

Stockholder of Record. If your shares are registered directly in your name with our transfer agent, Computershare, then you are considered a “stockholder of record” of those shares. In this case, the Notice has been sent to you directly by us. You may vote your shares by proxy prior to the Annual Meeting by following the instructions contained in this proxy statement or in the Notice.

Beneficial Owners of Shares Held in Street Name. If your shares are held in a brokerage account or by a bank, broker or other nominee or custodian, then you are considered the beneficial owner of those shares, which are held in “street name.” In this case, the Notice and voting instructions should have been forwarded to you by that organization. The organization holding your account is considered the stockholder of record for purposes of voting at the Annual Meeting. As the beneficial owner, you have the right to instruct that organization as to how to vote the shares held in your account by following the instructions contained on the voting instruction card provided to you by that organization.

How to Vote

If you are a stockholder of record, you can vote your shares in one of two ways: either by proxy or live online at the Annual Meeting. If you choose to vote by proxy, you may do so by telephone, via the Internet or by mail. Each of these methods is explained below. If you are a beneficial owner of shares held in “street name,” you can vote your shares by following the instructions contained on the voting instruction card provided to you by the bank, broker or other nominee or custodian that holds your shares. If you hold your shares of our common stock in multiple accounts, you should vote your shares as described in each set of proxy materials you receive.

Telephone and Internet voting for stockholders of record voting by proxy will be available up until 11:59 p.m. Eastern time on June 7, 2023 and mailed proxy cards must be received by June 7, 2023 in order to be counted at the Annual Meeting. If the Annual Meeting is adjourned or postponed, these deadlines may be extended. The voting deadlines and availability of telephone and Internet voting for beneficial owners of shares held in “street name” will depend on the voting processes of the organization that holds your shares. Therefore, we urge you to carefully review and follow the voting instruction card and any other materials that you receive from that organization.

Can I Vote My Shares by Filling Out and Returning the Notice of Internet Availability of Proxy Materials?

No. The Notice contains instructions on how to vote via the Internet, by telephone, by requesting and returning a paper proxy card, or by voting online during the Annual Meeting.

How Do I Ask Questions at the Annual Meeting?

Stockholders of the company as of the Record Date may submit questions during the Annual Meeting. If you wish to submit a question, you may do so by logging into the virtual meeting platform, typing your question into the “Ask a

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Question” field, and clicking “Submit.” Our Annual Meeting will be governed by our Rules of Conduct which will be posted at www.virtualshareholdermeeting.com/GBIO2023 in advance of the meeting and which will include rules on permissible topics for stockholder questions and rules for how questions and comments will be recognized.

What if I Experience Technical Difficulties during the Annual Meeting?

If you encounter any difficulties accessing the Annual Meeting during the check-in or meeting, please call the technical support number that will be posted on www.virtualshareholdermeeting.com/GBIO2023 for assistance.

Shares Held in “Street Name” and Broker Non-Votes

If your shares are held in “street name,” your bank, broker or other nominee or custodian may under certain circumstances vote your shares even if you do not return voting instructions. Stock exchange rules permit brokers to vote customers’ shares on certain proposals for which they have received no voting instructions. Stock exchange rules, however, prohibit brokers from voting uninstructed shares in the case of election of directors, executive compensation matters and certain other matters. Of the matters to be voted on at the Annual Meeting, we expect the only proposal on which brokers will have discretionary voting authority is the ratification of the appointment of Ernst & Young LLP as our independent registered public accounting firm for 2023 (Proposal No. 2).

Broker non-votes occur with respect to a matter when your broker submits a proxy for your shares but does not indicate a vote for a particular proposal because the broker either does not have the discretionary authority to vote on that proposal and has not received voting instructions from you.

Quorum

A quorum of stockholders is necessary to hold a valid meeting. Our amended and restated bylaws provide that a quorum will exist if stockholders holding a majority of the shares of stock issued and outstanding and entitled to vote are present at the meeting in person or by proxy. If a quorum is not present, the meeting may be adjourned until a quorum is obtained.

For purposes of determining whether a quorum exists, we will count as present any shares that are voted over the Internet, by telephone, by completing and submitting a proxy card by mail or that are represented in person at the Annual Meeting. Shares present virtually during the Annual Meeting will be considered shares represented in person at the meeting. Further, for purposes of establishing a quorum, we will count as present shares that a stockholder holds even if the stockholder votes to abstain or only votes on one of the proposals. In addition, we will count as present shares that are broker non-votes.

Votes Required

Proposal 1 – Election of Directors

To be elected, a director must receive a plurality of the votes cast by stockholders entitled to vote at the meeting. This means that the four nominees receiving the highest number of “FOR” votes will be elected as Class III directors. Shares held in street name by a bank, broker or other nominee or custodian who indicate on their proxies that they do not have authority to vote the shares on Proposal 1 will not be counted as votes FOR or WITHHELD from any director nominee and will be treated as broker non-votes. Broker non-votes will have no effect on the voting on Proposal 1. Votes that are withheld will not be included in the vote tally for the election of directors and will not affect the vote results.

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You may:

Proposal 2 – Ratification of the appointment of Ernst & Young LLP as our independent registered public accounting firm for the fiscal year ending December 31, 2023

To approve Proposal 2, stockholders holding a majority of the votes cast on the matter must vote FOR the proposal. If your shares are held by a bank, broker or other nominee or custodian in “street name” and you do not timely provide voting instructions with respect to your shares, we expect that your bank, broker or other nominee or custodian will have the discretionary authority to vote your shares on Proposal 2. If you ABSTAIN from voting on Proposal 2, your shares will not be voted FOR or AGAINST the proposal and will not be counted as votes cast or shares voting on Proposal 2. As a result, voting to ABSTAIN will have no effect on the voting on Proposal 2.

Proposal 3 - Approval of an amendment to our restated certificate of incorporation to reflect new Delaware law provisions regarding officer exculpation

To approve Proposal 3, stockholders holding a majority of the outstanding shares of our common stock entitled to vote thereon must vote FOR the proposal. Shares held in street name by a bank, broker or other nominee or custodian who indicate on their proxies that they do not have authority to vote the shares on Proposal 3 will not be counted as votes FOR or AGAINST Proposal 3 and will be treated as broker non-votes. If you vote to ABSTAIN on Proposal 3, your shares will not be voted FOR or AGAINST the proposal and will not be counted as votes cast or shares voting on Proposal 3. Because Proposal 3 requires the affirmative vote of the holders of a majority of the outstanding shares of our common stock entitled to vote thereon, broker non-votes and voting to ABSTAIN will have the same effect as a vote AGAINST Proposal 3.

Proposal 4 - Approval, on an advisory (non-binding) basis, of the compensation of our named executive officers

To approve Proposal 4, stockholders holding a majority of the votes cast on the matter must vote FOR the proposal. Shares held in street name by a bank, broker or other nominee or custodian who indicate on their proxies that they do not have authority to vote the shares on Proposal 4 will not be counted as votes FOR or AGAINST Proposal 4 and will be treated as broker non-votes. If you vote to ABSTAIN on Proposal 4, your shares will not be voted FOR or AGAINST the proposal and will also not be counted as votes cast or shares voting on Proposal 4. As a result, broker non-votes and voting to ABSTAIN will have no effect on the voting on Proposal 4.

Method of Counting Votes

Each holder of common stock is entitled to one vote at the Annual Meeting on each matter to come before the Annual Meeting, including the election of directors, for each share held by such stockholder as of the Record Date. Votes cast online during the Annual Meeting or by proxy by mail, via the Internet or by telephone will be tabulated by the inspector of election appointed for the Annual Meeting, who will also determine whether a quorum is present.

Revoking a Proxy; Changing Your Vote

If you are a stockholder of record, you may revoke your proxy before the vote is taken at the meeting:

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If your shares are held in “street name,” you may submit new voting instructions by contacting your bank, broker or other nominee or custodian holding your account. You may also vote online during the Annual Meeting, which will have the effect of revoking any previously submitted voting instructions, by following the instructions provided to you by the bank, broker or other nominee or custodian that holds your shares.

Your attendance at the Annual Meeting will not automatically revoke your proxy.

Costs of Proxy Solicitation

We will bear the costs of soliciting proxies. In addition to solicitations by mail, our directors, officers and regular employees, without additional remuneration, may solicit proxies by telephone, facsimile, email, personal interviews and other means.

Voting Results

We plan to announce preliminary voting results at the Annual Meeting and will publish final results in a Current Report on Form 8-K to be filed with the SEC within four business days following the Annual Meeting.

Householding

Some banks, brokers and other nominee or custodian record holders may be participating in the practice of “householding” proxy statements, annual reports, and notices of Internet availability of proxy materials. This means that only one copy of our documents, including the Notice, may have been sent to multiple stockholders in your household. We will promptly deliver a separate copy of any such document to you upon written or oral request prior to May 25, 2023 to Broadridge Financial Solutions, Inc. at (1) www.proxyvote.com, (2) 1-800-579-1639 or (3) sendmaterial@proxyvote.com. If you want to receive separate copies of our proxy statements, annual reports, or notices of Internet availability of proxy materials in the future, or if you are receiving multiple copies and would like to receive only one copy per household, you should contact your bank, broker or other nominee or custodian record holder, or you may contact us at the above address and phone number.

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PROPOSAL NO. 1—ELECTION OF FOUR CLASS III DIRECTORS

Our board of directors currently consists of ten members. In accordance with the terms of our restated certificate of incorporation and our amended and restated bylaws, our board of directors is divided into three classes (Class I, Class II and Class III), with members of each class serving staggered three-year terms. The members of the classes are divided as follows:

Upon the expiration of the term of a class of directors, directors in that class will be eligible to be elected for a new three-year term at the annual meeting of stockholders in the year in which their term expires.

Our restated certificate of incorporation and our amended and restated bylaws provide that the authorized number of directors may be changed only by resolution of our board of directors. Our restated certificate of incorporation and amended and restated bylaws also provide that our directors may be removed only for cause by the affirmative vote of the holders of at least 75% of the votes that all our stockholders would be entitled to cast in an annual election of directors, and that any vacancy on our board of directors, including a vacancy resulting from an enlargement of our board of directors, may be filled only by vote of a majority of our directors then in office.

Our board of directors has nominated Dannielle Appelhans; Gustav Christensen, Charles Rowland, and Catherine Stehman-Breen for election as Class III directors at the Annual Meeting. Each of the nominees is presently a director, and each has indicated a willingness to continue to serve as director, if elected. If a nominee becomes unable or unwilling to serve, however, the proxies may be voted for substitute nominees selected by our board of directors.

We have no formal policy regarding board diversity, but our corporate governance guidelines provide that the background and qualifications of the members of our board of directors considered as a group should provide a significant breadth of experience, knowledge, and abilities to assist our board of directors in fulfilling its responsibilities. Our priority in selection of board members is identification of members who will serve the best interests of the company and our stockholders through their reputation for integrity, honesty and adherence to high ethical standards; their demonstrated business acumen, experience, and ability to exercise sound judgment; their commitment to understanding the company and our industry; and their background, including prior experience and knowledge of the life sciences industry. Certain individual qualifications and skills of our directors that contribute to our board of directors’ effectiveness as a whole are described in the following paragraphs.

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Nominees for Election as Class III Directors

Biographical information, including principal occupation and business experience during the last five years, for our nominees for election as Class III directors at our Annual Meeting is set forth below.

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The board of directors recommends voting “FOR” the election of Dannielle Appelhans, Gustav Christensen, Charles Rowland, and Catherine Stehman-Breen, M.D. as Class III directors for a three-year term ending at the annual meeting of stockholders to be held in 2026.

Any properly submitted proxy will be voted in favor of the nominees unless a contrary specification is made in the proxy.

Directors Continuing in Office

Biographical information, including principal occupation and business experience during the last five years, for our directors continuing in office after the Annual Meeting is set forth below.

Class I Directors (Term Expires at 2024 Annual Meeting)

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Class II Directors (Term Expires at 2025 Annual Meeting)

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There are no family relationships between or among any of our directors or executive officers. The principal occupation and employment during the past five years of each of our directors was carried on, in each case except as specifically identified above, with a corporation or organization that is not a parent, subsidiary or other affiliate of us. There is no arrangement or understanding between any of our directors and any other person or persons pursuant to which he or she is to be selected as a director.

There are no material legal proceedings to which any of our directors or executive officers is a party adverse to us or our subsidiary or in which any such person has a material interest adverse to us or our subsidiary.

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Executive Officers Who Are Not Directors

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

Our stockholders are being asked to ratify the appointment by the audit committee of the board of directors of Ernst & Young LLP as our independent registered public accounting firm for the fiscal year ending December 31, 2023.

The audit committee is solely responsible for selecting our independent registered public accounting firm for the fiscal year ending December 31, 2023. Stockholder approval is not required to appoint Ernst & Young LLP as our independent registered public accounting firm. However, our board of directors believes that submitting the appointment of Ernst & Young LLP to the stockholders for ratification is good corporate governance. If the stockholders do not ratify this appointment, the audit committee will reconsider whether to retain Ernst & Young LLP. If the selection of Ernst & Young LLP is ratified, the audit committee, in its discretion, may direct the appointment of a different independent registered public accounting firm at any time it decides that such a change would be in the best interest of our company and our stockholders.

A representative of Ernst & Young LLP is expected to attend the Annual Meeting and will have an opportunity to make a statement if he or she desires to do so and to respond to appropriate questions from our stockholders.

We incurred the following fees from Ernst & Young LLP for the audit of the consolidated financial statements and for other services provided during the years ended December 31, 2022 and 2021.

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(1)Audit fees consist of fees for the audit of our annual financial statements, the review of interim financial statements included in our quarterly reports on Form 10-Q, and other professional services provided in connection with any registration statements filed with the SEC. Included in the 2022 and 2021 audit fees are fees billed in connection with our “at-the-market” offerings.

(2)Tax fees consist of fees for procedures completed in connection with an ownership change study.

(3)Consist of fees in connection with access to the Ernst & Young LLP online accounting research and disclosures database.

The aggregate fees included in audit fees, tax fees and all other fees are those fees billed for the fiscal year.

Audit Committee Pre-Approval Policy and Procedures

The audit committee of our board of directors has adopted policies and procedures for the pre-approval of audit and non-audit services for the purpose of maintaining the independence of our independent auditor. We may not engage our independent auditor to render any audit or non-audit service unless either the service is approved in advance by the audit committee, or the engagement to render the service is entered into pursuant to the audit committee’s pre-approval policies and procedures.

From time to time, our audit committee may pre-approve services that are expected to be provided to us by the independent auditor during the following 12 months. At the time such pre-approval is granted, the audit committee must identify the particular pre-approved services in a sufficient level of detail so that our management will not be called upon to make a judgment as to whether a proposed service fits within the pre-approved services and, at each regularly scheduled meeting of the audit committee following such approval, management or the independent auditor shall report to the audit committee regarding each service actually provided to us pursuant to such pre-approval.

During our 2022 and 2021 fiscal years, no services were provided to us by Ernst & Young LLP other than in accordance with the pre-approval policies and procedures described above.

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The board of directors recommends voting “FOR” Proposal No. 2 to ratify the appointment of Ernst & Young LLP as our independent registered public accounting firm for the fiscal year ending December 31, 2023.

Any properly submitted proxy will be voted in favor of the ratification of the appointment of Ernst & Young LLP as our independent registered public accounting firm for the fiscal year ending December 31, 2023 unless a contrary specification is made in the proxy.

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REPORT OF THE AUDIT COMMITTEE

The primary purpose of our audit committee is to assist our board of directors’ oversight of our accounting and financial reporting processes and the audits of our consolidated financial statements, as is more fully described in the audit committee charter. In the performance of its oversight function, our audit committee has reviewed our audited financial statements for the year ended December 31, 2022 and discussed them with our management and our independent registered public accounting firm, Ernst & Young LLP.

Our audit committee has also received from, and discussed with, Ernst & Young LLP various communications that Ernst & Young LLP is required to provide to our audit committee, including the matters required to be discussed by the applicable requirements of the Public Company Accounting Oversight Board and the SEC.

In addition, Ernst & Young LLP provided our audit committee with the written disclosures and the letter required by applicable requirements of the Public Company Accounting Oversight Board regarding the independent registered public accounting firm’s communications with the audit committee concerning independence, and the audit committee has discussed with the company’s independent registered public accounting firm their independence.

Based on the review and discussions referred to above, our audit committee recommended to our board of directors that our consolidated financial statements audited by Ernst & Young LLP be included in our Annual Report on Form 10-K for the year ended December 31, 2022.

By the audit committee of the board of directors of Generation Bio Co.

Charles Rowland, Chairman

Gustav Christensen

Anthony Quinn, M.B. Ch.B., Ph.D.

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CORPORATE GOVERNANCE

Director Nomination Process

Our nominating and corporate governance committee is responsible for identifying individuals qualified to serve as directors, consistent with criteria approved by our board, and recommending the persons to be nominated for election as directors, except where we are legally required by contract, law or otherwise to provide third parties with the right to nominate.

The process followed by our nominating and corporate governance committee to identify and evaluate director candidates includes requests to board members and others for recommendations, meetings from time to time to evaluate biographical information and background material relating to potential candidates and interviews of selected candidates by members of our management team, the committee and our board. The qualifications, qualities and skills that our nominating and corporate governance committee believes must be met by a committee-recommended nominee for a position on our board of directors are as follows:

The nominating and corporate governance committee has used, and may use, a third-party search firm in situations where particular qualifications are required or where existing contacts are not sufficient to identify an appropriate candidate.

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Stockholders may recommend individuals to the nominating and corporate governance committee for consideration as potential director candidates. Any such proposals should be submitted to our corporate secretary at our principal executive offices and should include appropriate biographical and background material to allow the nominating and corporate governance committee to properly evaluate the potential director candidate and the number of shares of our stock beneficially owned by the stockholder proposing the candidate. The specific requirements for the information that is required to be provided for such recommendations to be considered are specified in our amended and restated bylaws and must be received by us no later than the date referenced below under the heading “Stockholder Proposals.” Assuming that biographical and background material has been provided on a timely basis, any recommendations received from stockholders will be evaluated in the same manner as potential nominees proposed by the nominating and corporate governance committee. If our board of directors determines to nominate a stockholder-recommended candidate and recommends his or her election, then his or her name will be included on our proxy card for the next annual meeting.

Director Independence

Rule 5605 of the Nasdaq Listing Rules requires a majority of a listed company’s board of directors to be comprised of independent directors within one year of listing. In addition, the Nasdaq Listing Rules require that, subject to specified exceptions, each member of a listed company’s audit, compensation and nominating and corporate governance committees be independent under the Securities Exchange Act of 1934, as amended, or the Exchange Act. Audit committee members must also satisfy independence criteria set forth in Rule 10A-3 under the Exchange Act, and compensation committee members must also satisfy the independence criteria set forth in Rule 10C-1 under the Exchange Act. Under Rule 5605(a)(2), a director will only qualify as an “independent director” if, in the opinion of our board of directors, that person does not have a relationship that would interfere with the exercise of independent judgment in carrying out the responsibilities of a director. In order to be considered independent for purposes of Rule 10A-3, a member of an audit committee of a listed company may not, other than in his or her capacity as a member of the audit committee, the board of directors, or any other board committee, accept, directly or indirectly, any consulting, advisory, or other compensatory fee from the listed company or any of its subsidiaries or otherwise be an affiliated person of the listed company or any of its subsidiaries. In order to be considered independent for purposes of Rule 10C-1, the board must consider, for each member of a compensation committee of a listed company, all factors specifically relevant to determining whether a director has a relationship to such company which is material to that director’s ability to be independent from management in connection with the duties of a compensation committee member, including, but not limited to: the source of compensation of the director, including any consulting, advisory or other compensatory fee paid by such company to the director; and whether the director is affiliated with the company or any of its subsidiaries or affiliates. In March 2023, our board of directors undertook a review of the independence of each director. 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 our directors, with the exception of Dr. McDonough, is an “independent director” as defined under Nasdaq Listing Rules. Dr. McDonough is not an independent director under these rules because he is our president and chief executive officer. In making such determination, our board of directors considered the relationships that each such non-employee director has with our company and all other facts and circumstances our board of directors deemed relevant in determining independence, including the beneficial ownership of our capital stock by each non-employee director.

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Board Diversity Matrix

Our board of directors has voluntarily provided the self-identified information below.

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Board Committees

Our board of directors has established an audit committee, a talent committee, and a nominating and corporate governance committee. The talent committee serves as the compensation committee of our board. Each of the audit committee, talent committee, and nominating and corporate governance committee operates under a charter, and each such committee reviews its respective charter at least annually. A current copy of the charter for each of the audit committee, talent committee, and the nominating and corporate governance committee is posted under the heading of “Governance” in the “Investor Center” section on our website, which is located at http://www.generationbio.com.

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The following table provides membership information for the current composition of our audit committee, talent committee and nominating and corporate governance committee:

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* Jason Rhodes served as chair of our nominating and corporate governance committee until July 2022.

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Audit Committee

The members of our audit committee are Charles Rowland, Gustav Christensen and Anthony Quinn, and Charles Rowland is the chair of the audit committee. Our board of directors has determined that each of Mr. Rowland, Mr. Christensen and Dr. Quinn is independent within the meaning of Rule 10A-3 under the Exchange Act. Our board of directors has determined that Mr. Rowland is an “audit committee financial expert” as defined in applicable SEC rules. Our board of directors believes that the composition of our audit committee meets the requirements for independence under current Nasdaq and SEC rules and regulations. Our audit committee assists our board of directors in its oversight of our accounting

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and financial reporting process and the audits of our consolidated financial statements. The audit committee met six times during the year ended December 31, 2022, including telephonic meetings. Our audit committee’s responsibilities include:

All audit services to be provided to us and all non-audit services, other than de minimis non-audit services, to be provided to us by our registered public accounting firm must be approved in advance by our audit committee.

Talent Committee

The members of our talent committee are Jason Rhodes, Donald Nicholson and Catherine Stehman-Breen, and Jason Rhodes is the chair of the talent committee. Our board of directors has determined that each of Mr. Rhodes, Dr. Nicholson and Dr. Stehman-Breen is independent within the meaning of Rule 10C-1 under the Exchange Act. Our talent committee assists our board of directors in the discharge of its responsibilities relating to the talent and compensation practices of the company, including compensation of our executive officers. The talent committee met five times during the year ended December 31, 2022, including telephonic meetings. Our talent committee’s responsibilities include:

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The talent committee meets regularly in executive session. However, from time to time, various members of management and other employees, as well as outside advisors or consultants, may be invited by the talent committee to make presentations, to provide financial or other background information or advice, or to otherwise participate in talent committee meetings. No officer may participate in, or be present during, any deliberations or determinations of the talent committee regarding the compensation for such officer or any immediate family member of such officer. The charter of the talent committee grants the talent committee full access to all of our books, records, facilities, and personnel, as well as authority to obtain, at our expense, advice and assistance from internal and external legal, accounting, or other advisors and consultants, and other external resources that the talent committee considers necessary or appropriate in the performance of its duties. In particular, the talent committee may, in its sole discretion, retain compensation consultants to assist in its evaluation of executive and director compensation, including the authority to approve the consultant’s reasonable fees and other retention terms.

Aon’s Human Capital Solutions practice, a division of Aon plc (formerly known as Radford), acted as our talent committee’s compensation consultant until April 2022. With the advice of Aon, our talent committee completed its compensation benchmarking and review for the beginning of 2022. In April 2022, the talent committee engaged Compensia, Inc. as its compensation consultant for the remainder of 2022. Our talent committee evaluated Aon and Compensia’s relationships with the company, the members of our board of directors and our executive officers consistent with Nasdaq listing standards and based on the committee’s evaluation, the talent committee has determined that no conflicts of interest existed or exist between the company and either of Aon and Compensia.

Our talent committee reviews all compensation components including base salary, annual cash incentives, long-term incentive awards and other perquisites, as well as severance arrangements, change-in-control benefits and other forms of executive officer compensation. In addition, the talent committee 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. The talent committee also makes recommendations to our board of directors regarding the compensation of non-employee directors and has the authority to administer our equity-based plans.

Under its charter, the talent committee may form, and delegate authority to, subcommittees, consisting of independent directors, as it deems appropriate. As permitted by our 2020 Stock Incentive Plan, or the 2020 Plan, the talent committee has delegated to our Chief Executive Officer and our Chief Financial Officer the authority to approve grants of equity awards to new hire employees who are not members of the company’s leadership team and in connection with promotions or recognition grants for existing employees who are not members of the company’s leadership team, subject to certain limitations for each level of employment and an annual aggregate maximum amount of awards that can be granted pursuant to such delegated authority.

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Talent Committee Interlocks and Insider Participation

During 2022, the members of our talent committee were Jason Rhodes, Donald Nicholson and Catherine Stehman-Breen and none of them was an officer or employee of our company. None of our executive officers has served as a director or member of the talent committee (or other committee serving an equivalent function) of any other entity whose executive officers served as one of our directors or a member of the compensation committee. Except as set forth under “Transactions with Related Persons”, none of the members of the talent committee (or his or her immediate family members) has a direct or indirect material interest in a transaction with the company involving more than $120,000.

Nominating and Corporate Governance Committee

The members of our nominating and corporate governance committee are Ron Cooper, Dannielle Appelhans and Jeffrey Jonas, and Ron Cooper is the chair of the nominating and corporate governance committee. Jason Rhodes served as the chair of the nominating and corporate governance committee until July 2022, at which time Mr. Cooper became chair of, and Ms. Appelhans joined, the nominating and corporate governance committee. The nominating and corporate governance committee met three times during the year ended December 31, 2022, including telephonic meetings. Our nominating and corporate governance committee’s responsibilities include:

Board and Committee Meetings Attendance

The full board of directors met four times during the year ended December 31, 2022, including telephonic meetings. During 2022, each member of the board of directors attended in person or participated in 75% or more of the aggregate of (i) the total number of meetings of the board of directors (held during the period for which such person has been a director) and (ii) the total number of meetings held by all committees of the board of directors on which such person served (during the periods that such person served).

Director Attendance at Annual Meeting of Stockholders

Although we do not have a formal policy regarding attendance by members of our board of directors at our annual meeting of stockholders, we encourage all of our directors to attend. All members of our board of directors attended the 2022 annual meeting of stockholders.

Code of Business Conduct and Ethics

We have adopted a written code of business conduct and ethics that applies to our directors, officers and employees, including our principal executive officer, principal financial officer, principal accounting officer or controller, or persons performing similar functions. A copy of the code is posted under the heading “Governance” on the Investor Center section of our website, which is located at http://www.generationbio.com. If we make any substantive amendments to, or grant any waivers from, the code of business conduct and ethics for any officer or director, we will disclose the nature of such amendment or waiver on our website or in a current report on Form 8-K.

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Corporate Governance Guidelines

Our board of directors has adopted corporate governance guidelines to assist in the exercise of its duties and responsibilities and to serve the best interests of our company and our stockholders. The guidelines provide that:

A copy of the corporate governance guidelines is posted under the heading “Governance” on the Investor Center section of our website, which is located at http://www.generationbio.com.

Board Leadership Structure and Board’s Role in Risk Oversight

Our corporate governance guidelines provide that the roles of chairman of the board and chief executive officer may be separated or combined. Our board of directors has considered its leadership structure and determined that, at this time, the roles of chairman of the board of directors and chief executive officer should be separate. Separating the chairman and the chief executive officer positions allows our chief executive officer, Dr. McDonough, to focus on running the business, while allowing our chairman of the board of directors, Mr. Rhodes, to lead our board in its fundamental role of providing advice to and oversight of management. As our board of directors has determined that each of our directors other than Dr. McDonough is independent, our board of directors believes that the independent directors provide effective oversight of management. Our board of directors believes that its leadership structure is appropriate because it strikes an effective balance between strategic development and independent leadership and management oversight in the board process. However, our board of directors will continue to periodically review our leadership structure and may make such changes in the future as it deems appropriate.

Risk is inherent with every business and how well a business manages risk can ultimately determine its success. We face a number of risks, including those described under “Risk Factors” in our 2022 Annual Report. Our board of directors is actively involved in oversight of risks that could affect us. This oversight is conducted primarily by our full board of directors, which has responsibility for general oversight of risks. Our board of directors oversees our risk management processes directly and through its committees. Our risk management processes are intended to identify, manage and control risks so that they are appropriate considering our scope, operations and business objectives. Our management is responsible for risk management on a day-to-day basis and our board and its committees oversee the risk management activities of management. Our board of directors encourages management to promote a culture that incorporates risk management into our corporate strategy and day-to-day business operations. Management discusses strategic and operational risks at regular management meetings and conducts specific strategic planning and review sessions during the year that include a focused discussion and analysis of the risks facing us. Our board of directors satisfies its risk oversight responsibility through full reports by each committee chair regarding the committee’s considerations and actions, as well as through regular reports directly from officers responsible for oversight of particular risks within our company. Generally, every quarter, management reviews and updates detailed assessments of our enterprise risks, as well as the steps being taken or proposed to be taken in order to mitigate such risks, and such information is presented to our board of directors annually or more frequently if warranted. This enables our board of directors to coordinate risk oversight, particularly with respect to interrelated or cumulative risks that may involve multiple areas for which more than one committee may have responsibility.

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Our audit committee oversees risk management activities related to financial reporting, accounting controls, internal audit functions, our independent accounting firm, related-party transactions, whistleblower reporting and information technology controls and legal and compliance risks, as well as cybersecurity risks. Our talent committee oversees risk management activities relating to our compensation policies and practices, executive performance, non-employee director compensation and management succession planning. Our nominating and corporate governance committee oversees risk management activities relating to board composition and effectiveness, and corporate governance policies and practices. In addition, members of our senior management team attend our quarterly board meetings and are available to address any questions or concerns raised by the board on risk management and any other matters. Our board of directors believes that full and open communication between management and the board of directors is essential for effective risk management and oversight.

Corporate Social Responsibility (CSR)

We believe that we have a corporate social responsibility to foster a diverse, equitable, inclusive and just workplace environment and to have a positive impact on our employees and the communities in which we work and live. We believe our success largely depends on our ability to attract, motivate, engage, and retain highly skilled employees. We believe programs that cultivate our diverse, equitable, inclusive and just culture encourage leadership growth and development, and foster robust relationships among employees and management, which, combined with providing competitive compensation and benefits, may create a workplace that results in more creative thinking, more rapid discovery and better decision making.

Justice, Equity and Belonging

We have created a framework that embodies our holistic commitment to justice, equity and belonging to empower everyone at our company to practice and embed this commitment. As we continue to grow as an organization, we remain dedicated to cultivating a culture that respects the worth, dignity, and equality of every individual in our organization. We strive to ensure that our policies, processes, and programs are impartial, fair, and support equality for every individual at our company. We believe belonging requires diversity and inclusion, as well as actively enabling everyone to be visible, heard and engaged in our community.

We believe that a core strength of our company is the diverse mosaic of employees who bring their mix of backgrounds, skillsets, experiences, and ideas together in an open and supportive atmosphere, which fosters collaboration. We are committed to having a diverse slate of potential employees and we seek to increase representation from historically marginalized communities, particularly in leadership roles. As of March 31, 2023, approximately 61.5% of our leadership team is female and across our workforce, our employee population consists of 46.1% women, 53.2% men, and 0.7% undeclared. Additionally, we celebrate and educate about our diversity through virtual and in-person employee events, awareness campaigns and other programs. We also promote opportunities for all employees to join our acting for justice and women’s forums, which support and promote certain mutual objectives of both our company and our employees, including inclusion and diversity.

Growth and Development

We believe it is important to invest in our employees’ personal and career growth. Our leadership model provides a framework for employees and managers to reflect upon and support developing their capabilities and competencies. As part of our people practices, employees and their managers hold quarterly dialogues and development conversations to define development goals and corresponding action plans. We aim to provide employees with access to a wide range of development opportunities. For example, managers participate in a comprehensive, longitudinal, cohort learning experience to further build their capabilities and effectiveness as managers. We also offer internal leadership development sessions as well as provide our employees with reimbursement for external training programs that are related to their current work or career development. Our goal is to ensure that our employees have the skills necessary to meet their current responsibilities optimally, as well as develop new skills that they may need in the future.

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Compensation and Benefits

We offer a comprehensive compensation and benefits package, which includes a competitive salary, medical, dental, and vision insurance, medical and dependent flexible spending accounts, life and disability insurance, and a 401(k) match. In addition, employees receive equity in the company upon the start of their employment and on an annual basis, and can also participate in our employee stock purchase plan. To ensure that our employees are paid competitively and at a rate consistent with an employee’s position, knowledge and skills, we perform a formal compensation benchmark analysis of our employees’ base salary, annual cash incentive potential, and long-term incentive awards twice per year and link annual cash incentives to overall company performance. Additionally, we perform a gender pay gap analysis designed to ensure that women are paid equally to their male counterparts.

We also have a tuition reimbursement program, offer tutor assistance, and provide programs that focus on our employee’s engagement and well-being, including access to our employee assistance program and company-sponsored, employee-led clubs and teams.

Our Community

We take our responsibility as a member of our local community seriously. Our outreach team guides our strategy and approach for community engagement and partnering with various non-profit organizations. For example, we are involved with several non-profit organizations, such as Project Onramp, Biomedical Science Careers, and Life Science Cares, that seek to increase the representation of underrepresented minority and disadvantaged individuals in the scientific and medical community. Our involvement includes providing company donations, providing internship and mentorship opportunities, and encouraging our employees to volunteer at various events and activities. We also participate in Northeastern University’s cooperative education program to provide full-time work to students so they may gain valuable industry skills and broaden their perspectives.

Communication with Our Directors

Any interested party with concerns about our company may report such concerns to the board of directors or otherwise the chairman of the nominating and corporate governance committee, by submitting a written communication to the attention of such director at the following address:

c/o Generation Bio Co.

301 Binney Street

Cambridge, MA 02142

United States

You may submit your concern anonymously or confidentially by postal mail. You may also indicate whether you are a stockholder, customer, supplier, or other interested party.

A copy of any such written communication may also be forwarded to our legal counsel and a copy of such communication may be retained for a reasonable period of time. The director may discuss the matter with our legal counsel, with independent advisors, with non-management directors, or with our management, or may take other action or no action as the director determines in good faith, using reasonable judgment, and discretion. Communications are forwarded to all directors if they relate to important substantive matters and include suggestions or comments that the chairman of the board (if one is appointed and is an independent director), the lead director (if one is appointed) or otherwise the chairman of the nominating and corporate governance committee, subject to the advice and assistance of counsel, consider to be important for the directors to know. In general, communications relating to corporate governance and corporate strategy are more likely to be forwarded than communications relating to ordinary business affairs, personal grievances and matters as to which we receive repetitive or duplicative communications.

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DIRECTOR COMPENSATION

The table below shows all compensation to our non-employee directors during the year ended December 31, 2022.

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During 2022, we did not provide any compensation to Geoff McDonough, our President and Chief Executive Officer, for his service as a director. Dr. McDonough’s compensation is set forth under “Executive Compensation—Summary Compensation Table.”

Non-Employee Director Compensation Program

Our non-employee directors receive annual equity grants pursuant to our director compensation program on or around the date of our Annual Meeting. In April 2022, our board of directors amended our director compensation program, effective April 18, 2022, to increase the equity compensation our directors receive. Under the 2022 amended program, each newly-elected non-employee director received, upon his or her initial election or appointment to our board of directors, an option to purchase 38,400 shares of our common stock under the 2020 Plan, which vests with respect to 1/36 of the shares at the end of each successive month following the grant date until the third anniversary of the grant date. Further, on the date of each annual meeting of stockholders, each non-employee director that served on our board of directors for at least six months received, under the 2020 Plan, an option to purchase 19,200 shares of our common stock under the 2020 Plan, which vests with respect to 100% of the shares on the earlier of the first anniversary of the grant date and the date of the

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annual meeting of stockholders in the year immediately following the year in which the option was granted. All options issued to our non-employee directors under our amended director compensation program will be issued at exercise prices equal to the fair market value of our common stock on the date of grant and will have a term of ten years.

In March 2023, our board of directors further amended our director compensation program, effective as of April 1, 2023, to increase the number of options granted as initial or annual grants. Pursuant to this amended program, each newly-elected non-employee director will receive an option to purchase 50,000 shares of our common stock under the 2020 Plan and, on the date of each annual meeting of stockholders, each non-employee director that has served on our board of directors for at least six months will receive an option to purchase 25,000 shares of our common stock under the 2020 Plan. No change was made to the annual cash retainers.

The fees paid to non-employee directors for service on the board of directors and for service on each committee of the board of directors on which the director is a member are as follows:

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The fees paid to non-employee directors are paid in arrears and are prorated for the number of days in which our non-employee directors serve on our board of directors or any committee of our board of directors. We also reimburse our non-employee directors for reasonable travel and other expenses incurred in connection with attending meetings of our board of directors and any committee of our board of directors on which he or she serves.

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EXECUTIVE COMPENSATION

Compensation Discussion and Analysis

Overview

Our talent committee is responsible for reviewing and approving, or recommending for approval by the board of directors, the compensation of our executive officers, including our named executive officers, or NEOs, including salary, annual cash incentives and long-term incentive awards, severance arrangements, change in control benefits and other forms of compensation. At our 2022 annual meeting of stockholders, our stockholders approved an advisory (non-binding) vote on executive compensation by a significant majority. This section discusses the philosophy, programs, processes, decisions, and other relevant information with respect to the compensation of our NEOs.

Our NEOs for the year ended December 31, 2022 were:

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Company Background

We are innovating genetic medicines to provide durable, redosable treatments for potentially hundreds of millions of patients living with rare and prevalent diseases. Our non-viral genetic medicine platform incorporates our high-capacity DNA construct called closed-ended DNA, or ceDNA; our cell-targeted lipid nanoparticle delivery system, or ctLNP; and our highly scalable capsid-free manufacturing process that uses our proprietary cell-free rapid enzymatic synthesis, or RES, to produce ceDNA. Using our approach, we are developing novel genetic medicines to provide targeted delivery of genetic payloads that include large and multiple genes to a range of cell types across a broad array of diseases. We are also engineering our genetic medicines to be redosable, which may enable individualized patient titration to reach the desired level of therapeutic expression and to maintain efficacy throughout a patient’s life.

Business Environment and Performance

As a preclinical stage biotechnology company headquartered in Cambridge, Massachusetts, we operate in a highly competitive environment for talent. We recognize that, to be successful, we need to recruit, motivate and retain executives that have excellent scientific, business and functional expertise, broad experience in the biotechnology industry, and the capability to produce desired strategic and operational results. Accordingly, our executive officers’ compensation accounts for the individual’s expertise and experience, the company achieving its objectives for the year, and the need to incentivize long-term company success. This approach to executive compensation is aligned with the interests of our stockholders because it is designed to ensure that we attract, motivate and retain key leaders while incentivizing each individual to deliver optimal results for the company.

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Compensation Philosophy and Process

The goals of our compensation programs are to pay for performance and ensure that the interests of our employees, including our NEOs, are aligned with the interests of our stockholders and our business goals, and that the total compensation paid to each of our NEOs is fair, reasonable, and competitive. Within this overarching principle, there are a number of key objectives that the compensation program is designed to achieve.

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To attract, motivate, and retain qualified executives, we seek to pay our NEOs compensation that is competitive within our industry. To understand the competitive market for NEO compensation in our industry, the talent committee engages  an independent compensation consultant to perform market assessment exercises and benchmarking biannually. We aim to target the 50th percentile of our peer group for each compensation element for our NEOs. In addition, the talent committee also considers other criteria when assessing NEO compensation, such as his or her experience, contributions, role, and potential.

Role of the Talent Committee. The talent committee is responsible for establishing and overseeing our executive compensation program. Our talent committee typically reviews and discusses with management, including our Chief Executive Officer (other than with respect to his compensation), proposed compensation for all NEOs and then, after further consideration of the information regarding market practices and trends provided by our compensation consultant, the talent committee may make a recommendation to our board of directors about the compensation of each NEO or approve such compensation as a committee.

Role of our Chief Executive Officer. Our Chief Executive Officer evaluates and reviews with the talent committee the individual performance and contributions of each of the other NEOs and makes recommendations to the talent committee regarding base salary, annual cash incentives and long-term incentive awards for each of the other NEOs. The talent committee reviews and considers such recommendations, but ultimately retains full discretion and authority over the final compensation decisions for the NEOs. Our Chief Executive Officer, in consultation with other members of our management team, also recommends the corporate performance objectives that are reviewed and approved by the talent committee and the board of directors and used to determine annual cash incentive amounts.

Role of our Independent Compensation Consultant. Pursuant to its charter, the talent committee has the sole authority to retain compensation consultants to assist in its evaluation of executive and director compensation. Our talent committee assessed our directors’ and executives’ compensation relative to comparable companies to determine base salaries and target bonus percentages for 2022 based on advice and information provided by Aon, who acted as the talent committee’s independent compensation consultant until April 2022. Starting in April 2022, our talent committee terminated its engagement with Aon and engaged Compensia as its independent compensation consultant to take over this role and provide our talent committee with additional information regarding market compensation practices and trends. Our executive compensation benchmarking also included survey data provided by Aon, representing publicly-traded life science companies with  market capitalization similar to us and that are in a stage of development comparable to ours.  

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Factors in Setting Compensation. The talent committee reviews NEO compensation biannually. As part of its biannual reviews, the talent committee evaluates our compensation program and arrangements for our NEOs based on a number of factors, including:

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An important external factor in making compensation decisions is our compensation peer group, which is determined annually. The talent committee considers a select number of key inputs, summarized below, to determine the companies to be included in the peer group. The compensation data from the peer group provide a benchmark for market-competitive base salaries, short- and long-term incentive targets, and estimated total direct compensation.

The talent committee, with the advice of Aon , used the following screening criteria to determine the group of companies to be in the peer group that was used in setting 2022 compensation:

Based on these criteria, in August 2021, the talent committee approved a peer group of 17 companies that was used in benchmarking compensation for the remainder of 2021 and until August 2022, as listed below.

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In conducting our annual review of our peer group, in August 2022, the talent committee, with the advice of Compensia, reviewed the companies included in the above-mentioned peer group for continued appropriateness using the criteria described above. Following the talent committee’s review, Compensia identified nine additional companies that more closely aligned with our criteria and suggested removing nine companies (Allogene Therapeutics, Inc., CRISPR Therapeutics AG, Homology Medicines, Inc., AVROBIO, Inc., Intellia Therapeutics, Inc., Beam Therapeutics Inc., Magenta Therapeutics, Inc., Rubius Therapeutics, Inc. and Stoke Therapeutics, Inc.) that no longer met our prescribed criteria due to acquisition or changes in their stages of development, business models and/or market capitalization. The talent committee approved a peer group of 17 companies to be used in benchmarking compensation for the remainder of 2022, as listed below.

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* New company for the peer group.

Our revised peer group was used in setting compensation for our employees, including our NEOs, for 2023.

We believe that the compensation practices of our peer groups provided us with appropriate compensation data for evaluating the competitiveness of the compensation of our NEOs during 2022. After approval of the peer group by the talent committee, management presented recommendations to the talent committee regarding proposed adjustments to NEO compensation, including compensation data from the peer group and Aon’s survey data, which the talent committee further reviewed and considered. Our talent committee generally targets both short- and long-term incentive compensation for our executive officers at approximately the 50th percentile of our peer group, while considering other criteria, including market factors, the experience level of the executive or NEO and the executive’s or NEO’s performance against established company goals, in determining variations from this general target range.

Compensation Elements and Decisions

The primary elements of our executive compensation program are:

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Annual Base Salary

Base salaries are used to attract, motivate and retain top talent, recognizing the experience, skills, knowledge and responsibilities required of our NEOs. Base salaries for our NEOs are established at the time the NEO is hired, taking into account the position for which the NEO is being considered and the relevant market data (where available), as well as the NEO’s qualifications and prior experience. None of our NEOs is currently party to an employment agreement that provides for automatic or scheduled increases in base salary. However, on a biannual basis, our talent committee reviews and evaluates, with input from our Chief Executive Officer (other than with respect to himself), the need for adjustment of the base salaries of our NEOs based on changes and expected changes in the scope of a NEO’s responsibilities, including promotions, the individual contributions made by and performance of the NEO during the prior year, overall labor market conditions, the relative ease or difficulty of replacing the executive with a well-qualified person, our overall growth and development as a company and general salary trends in our industry and among our peer group and where the NEO’s salary falls in the salary range presented by relevant market data. In making decisions regarding salary increases, our talent committee may also draw upon the experience of members of the talent committee and of our full board of directors with other companies. No formulaic base salary increases are provided to our NEOs. After considering the preceding factors, in January 2022, the talent committee approved a four percent increase to each NEOs’ base salary. There was no adjustment to NEO compensation following the talent committee’s review in July 2022.

The following table presents the base salaries for each of our NEOs for the years 2021 and 2022, as approved by our talent committee. 2021 base salaries became effective on January 16, 2021, except as noted with respect to Dr. Zimmerman’s 2021 base salary, which reflects a mid-year salary increase, and 2022 base salaries became effective on January 16, 2022.

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Short-term Incentives

Our annual cash incentive program is designed to motivate and reward our NEOs for achievements relative to our corporate objectives and expectations for each fiscal year. Under our annual cash incentive program, each NEO has a target annual cash incentive opportunity, defined as a percentage of his or her base salary. The general design of our annual cash incentive program is as follows:

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Corporate Goals and Objectives

At the end of each year, our board of directors, after reviewing management’s proposal, establishes the annual corporate performance goals and objectives that it believes will be the most significant drivers of our short-term and long-term success. The corporate performance goals and objectives may include target achievement dates based on calendar quarters. Each executive, including each NEO, is eligible to receive an annual cash incentive based on achievement of corporate performance goals and objectives, as opposed to individual performance goals and objectives, as assessed by our talent committee and board of directors. Each executive officer, including each NEO, has a target annual cash incentive amount, expressed as a percentage of each NEO’s annualized salary then in effect. After the fiscal year is completed, our board of directors reviews the company’s performance and objectives against the stated goals and determines what it believes to be the appropriate level of cash incentive, if any, for our company.

In December 2021, our board of directors approved our 2022 corporate goals and objectives, which were to:

Specific achievements that our talent committee and board of directors reviewed to support the 2022 annual cash incentive awards to our NEOs, as set forth below in “Final Calculation”, included:

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Final Calculations

In January 2023, our board of directors reviewed the performance of our NEOs against the 2022 annual cash incentive goals and determined that the corporate goals and objectives had been achieved at 100% of target level. The final calculations used to arrive at the 2022 annual cash incentive awards are as follows:

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Long-term Incentives

Although we do not have a formal policy with respect to the grant of long-term incentive awards to our executive officers, or any formal equity ownership guidelines applicable to them, we believe that equity grants provide our executive officers with a strong link to our long-term performance, create an ownership culture and help to align the interests of our executive officers and our stockholders. In addition, we believe that equity grants with a time-based vesting feature promote executive retention because this feature incentivizes our executive officers to remain in our employment during the vesting period. Accordingly, our talent committee periodically reviews the long-term incentive compensation of our executive officers, including our NEOs, and from time to time may grant long-term incentive awards to them in the form of stock options or restricted stock units. Prior to our initial public offering, or IPO, our executive officers were eligible to participate in our 2017 Stock Incentive Plan, as amended, or the 2017 Plan. All stock options granted before our IPO were granted pursuant to the 2017 Plan. Since our IPO, our executive officers have been eligible to receive stock options and other equity awards pursuant to our 2020 Plan.

We have used stock options and, since January 2022, restricted stock units, or RSUs, to compensate our executive officers in the form of initial grants in connection with the commencement of employment, promotion grants in connection with a promotion, and annual grants. In January 2022, after a review of the value of our employees’ stock options, due to the volatility of our stock prices and in consideration of our goal of providing competitive compensation, we issued a one-time grant of RSUs to all employees, including our NEOs. For our 2022 annual grants, employees, including our NEOs, were given the option to elect whether to receive options or options and RSUs at a two-to-one ratio. Since January 2023, our annual grants and new hire grants include both stock options and RSUs.

In determining long-term incentive grants for new hires, the board of directors and/or talent committee evaluate (where available):

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In determining annual long-term incentive grants for existing NEOs, the talent committee evaluates:

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All stock options granted by us, including those made to our NEOs, have exercise prices equal to the closing market price on the Nasdaq Global Select Market of our common stock on the date of grant, so that the recipient will not recognize any value from his or her stock options unless our share price increases above the exercise price. Accordingly, this portion of our executive officers’ compensation is at risk and thus our approach emphasizes the pay-for-performance link, and is directly aligned with stockholder value creation. In addition, stock options granted to our executive officers, including our NEOs, generally have a ten-year term and vest over four years, with 25% of the shares vesting on the first anniversary of the grant or vesting commencement date, and the remainder vesting in equal quarterly installments thereafter, subject to continuous service. Prior to the exercise of a stock option, the holder has no rights as a stockholder with respect to the shares subject to such option, including no voting rights and no right to receive dividends or dividend equivalents.

Generally, RSUs granted by us, including those made to our NEOs, vest over four years, with 25% of the shares vesting on the fifteenth day of month of the first anniversary of the grant date, and the remainder vesting in equal quarterly installments thereafter, subject to continuous service. In January 2022, we made a one-time grant of RSUs to all employees that vest over two years, with 25% of the shares vesting on July 15, 2022, and the remainder vesting in equal quarterly installments thereafter, subject to continuous service. Prior to the vesting of an RSU, the holder has no rights as a stockholder with respect to the shares subject to such award, including no voting rights and no right to receive dividends or dividend equivalents.

The following table sets forth the number of shares of common stock issuable upon exercise of the stock options and RSUs granted to our NEOs in 2022 as part of our annual grants and the January 2022 one-time RSU grants:

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Potential Payments Upon Termination or Change in Control

Certain employees, including our NEOs, are entitled to severance and change in control benefits pursuant to their employment arrangements and under the terms of our severance plan benefits agreements, which benefits are in addition to the benefits generally available to salaried employees and are summarized below under the heading “Employment, Severance and Change in Control Arrangements.” Upon certain terminations of employment in connection with a change of control, vesting of the stock options and/or restricted stock that we have granted to our NEOs is fully accelerated; upon other involuntary terminations, 25% of the unvested portion of each grant will vest as of the date of the termination. Our goal in providing severance and change in control benefits is to offer sufficient cash continuity protection such that our employees will focus their full time and attention on the requirements of the business rather than the potential implications for their respective position. We prefer to have certainty regarding the potential severance amounts payable to the NEOs, rather than negotiating severance at the time that an NEOs’ employment terminates.

Benefits

We evaluate the competitiveness of our arrangements periodically and have found that our NEO benefits are competitive with our peers. For more information on our employment arrangements, please see “Employment, Severance and Change in Control Arrangements.” We believe that these are typical benefits offered by comparable companies.

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We maintain a defined contribution employee retirement plan for our employees, including our NEOs. The plan is intended to qualify as a tax-qualified 401(k) plan so that contributions to the 401(k) plan, and income earned on such contributions, are not taxable to participants until withdrawn or distributed from the 401(k) plan (except in the case of contributions under the 401(k) plan designated as Roth contributions). Our talent committee has approved a matching program of up to 4% of an employee’s annual salary, subject to maximums established under the Code, beginning in the year ending December 31, 2021. Under the 401(k) plan, each employee is fully vested in his or her deferred salary contributions and our employer match. Employee contributions are held and invested by the plan’s trustee as directed by participants.

Our NEOs are eligible to participate in all of our employee benefit plans, including our medical, dental, vision, long-term disability and term life insurance plans, flexible spending accounts, fitness benefits, employee stock purchase plan, and 401(k) matching contributions, in each case on the same basis as other employees. We typically do not provide additional perquisites or personal benefits to our NEOs, although on a case-by-case basis we may periodically do so, subject to any required approvals. We do not sponsor any qualified or non-qualified defined benefit plans for any of our employees, including NEOs.

Anti-Hedging Policy

Our board of directors has adopted an Insider Trading Policy, which applies to all of our directors and employees and certain of their family members and any entities any of them control. The policy prohibits the following transactions in our securities:

Our Insider Trading Policy also generally prohibits purchasing our securities on margin, borrowing against our securities held in a margin account, or pledging our securities as collateral for a loan.

No Tax Gross-Ups

We do not provide for any tax gross-up payments to our NEOs.

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Tax and Accounting Considerations

Under Section 162(m) of the U.S. Internal Revenue Code of 1986, as amended, or the Code, a company will generally not be entitled to a tax deduction for individual compensation over $1 million that is paid to certain executive officers. As in effect prior to its recent amendment by the Tax Cuts and Jobs Act of 2017, Section 162(m) provided an exception to the deductibility limitations for performance-based compensation that met certain requirements. While considering the impact of Section 162(m) and awarding certain elements of compensation that, at the time, were intended to qualify as performance-based compensation, the talent committee did not adopt a policy requiring all compensation to be fully deductible under Section 162(m). As Section 162(m) has been amended, effective for taxable years beginning after December 31, 2017, the “performance-based” compensation exception was eliminated from Section 162(m), except for certain grandfathered arrangements under the transition rules. In light of this amendment, the talent committee and board of directors will continue to consider the potential impact of the application of Section 162(m) on compensation for our executive officers and reserves the right to provide compensation to executive officers that may not be tax-deductible, as well as the right to modify compensation that was initially intended to qualify as “performance-based” compensation if it believes that taking any such action is in the best interests of our company and our stockholders.

Compensation Risk Assessment

Our management and the talent committee review our compensation practices and policies with regard to risk management. We have reviewed our programs and we believe that there are no practices or policies that are likely to lead to excessive risk-taking or have a material adverse effect on us. Further, we identified the following practices that we believe serve to mitigate risk:

Talent Committee Report

The talent committee has reviewed and discussed the Compensation Discussion and Analysis required by Item 402(b) of Regulation S-K with our management. Based on this review and discussion, the talent committee recommended to the board of directors that the Compensation Discussion and Analysis be included in this proxy statement and in our Annual Report for the fiscal year ended December 31, 2022.

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By the talent committee of the board of directors of Generation Bio Co.

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Jason Rhodes, Chairman

Donald Nicholson, Ph.D.

Catherine Stehman-Breen, M.D.

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Summary Compensation Table

The following table sets forth information regarding compensation awarded to, earned by or paid to our NEOs during the fiscal years ended December 31, 2022, 2021 and 2020.

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Grants of Plan-Based Awards Table

The following table sets forth information concerning each grant of an award made to our NEOs during the fiscal year ended December 31, 2022 under any plan, contract, authorization or arrangement pursuant to which cash, securities, similar instruments or other property may be received:

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Outstanding Equity Awards at Fiscal Year-End

The following table sets forth information regarding all outstanding equity awards for each of our NEOs as of December 31, 2022:

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