FIXX Homology Medicines Inc

Notice of Annual Meeting of Stockholders

To Be Held Thursday, June 17, 2021

HOMOLOGY MEDICINES, INC.

ONE PATRIOTS PARK

BEDFORD, MASSACHUSETTS 01730

The Annual Meeting of Stockholders (the “Annual Meeting”) of Homology Medicines, Inc., a Delaware corporation (the “Company”), will be held at 9:00 a.m. Eastern time on Thursday, June 17, 2021, online at www.virtualshareholdermeeting.com/FIXX2021, for the following purposes:

Holders of record of our Common Stock as of the close of business on April 23, 2021 are entitled to notice of and to vote at the Annual Meeting, or any continuation, postponement or adjournment of the Annual Meeting. A complete list of such stockholders will be open to the examination of any stockholder for a period of ten days prior to the Annual Meeting for a purpose germane to the meeting by sending an email to IR@homologymedicines.com, stating the purpose of the request and providing proof of ownership of Company stock. The list of these stockholders will also be available on the bottom of your screen during the Annual Meeting after entering the 16-digit control number included on your Notice of Internet Availability of Proxy Materials, on your proxy card or on the instructions that accompanied your proxy materials. The Annual Meeting may be continued or adjourned from time to time without notice other than by announcement at the Annual Meeting.

It is important that your shares be represented regardless of the number of shares you may hold. Whether or not you plan to participate in the Annual Meeting, we urge you to vote your shares via the toll-free telephone number or over the Internet, as described in the enclosed materials. If you received a copy of the proxy card by mail, you may sign, date and mail the proxy card in the enclosed return envelope. Promptly voting your shares will ensure the presence of a quorum at the Annual Meeting and will save us the expense of further solicitation. Submitting your proxy now will not prevent you from voting your shares at the Annual Meeting if you desire to do so, as your proxy is revocable at your option.

By Order of the Board of Directors

W. Bradford Smith

Chief Financial Officer and Treasurer

Bedford, Massachusetts

April 29, 2021

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PROXY STATEMENT

HOMOLOGY MEDICINES, INC.

ONE PATRIOTS PARK

BEDFORD, MASSACHUSETTS 01730

This proxy statement is furnished in connection with the solicitation by the Board of Directors of Homology Medicines, Inc. (the “Board” or the “Board of Directors”) of proxies to be voted at our Annual Meeting of Stockholders to be held on Thursday, June 17, 2021 (the “Annual Meeting”), at 9:00 a.m. Eastern time, and at any continuation, postponement, or adjournment of the Annual Meeting. The Annual Meeting will be a completely virtual meeting, which will be conducted via live webcast. You will be able to attend the Annual Meeting online and submit your questions during the meeting by visiting www.virtualshareholdermeeting.com/FIXX2021 and entering your 16-digit control number included on your Notice of Internet Availability of Proxy Materials (the “Internet Notice”), on your proxy card or on the instructions that accompanied your proxy materials. Holders of record of shares of our common stock, $0.0001 par value per share, as of the close of business on April 23, 2021 (the “Record Date”), will be entitled to notice of and to vote at the Annual Meeting and any continuation, postponement, or adjournment of the Annual Meeting. As of the Record Date, there were 57,083,955 shares of common stock outstanding and entitled to vote at the Annual Meeting. Each share of common stock is entitled to one vote on any matter presented to stockholders at the Annual Meeting.

This proxy statement and the Company’s Annual Report to Stockholders for the year ended December 31, 2020 (the “2020 Annual Report”) will be released on or about April 29, 2021 to our stockholders on the Record Date.

In this proxy statement, “Homology”, “Company”, “we”, “us”, and “our” refer to Homology Medicines, Inc.

IMPORTANT NOTICE REGARDING THE AVAILABILITY OF PROXY MATERIALS FOR THE STOCKHOLDER MEETING TO BE HELD ON THURSDAY, JUNE 17, 2021

This Proxy Statement and our 2020 Annual Report to Stockholders are available at http://www.proxyvote.com/Proposals

At the Annual Meeting, our stockholders will be asked:

We know of no other business that will be presented at the Annual Meeting. If any other matter properly comes before the stockholders for a vote at the Annual Meeting, however, the proxy holders named on the Company’s proxy card will vote your shares in accordance with their best judgment.

Recommendations of the Board

The Board of Directors recommends that you vote your shares as indicated below. If you return a properly completed proxy card, or vote your shares by telephone or Internet, your shares of common stock will be voted on your behalf as you direct. If not otherwise specified, the shares of common stock represented by the proxies will be voted, and the Board of Directors recommends that you vote:

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If any other matter properly comes before the stockholders for a vote at the Annual Meeting, the proxy holders named on the Company’s proxy card will vote your shares in accordance with their best judgment.

Information About This Proxy Statement

Why you Received this Proxy Statement. You are viewing or have received these proxy materials because Homology’s Board of Directors is soliciting your proxy to vote your shares at the Annual Meeting. This proxy statement includes information that we are required to provide to you under the rules of the Securities and Exchange Commission (“SEC”) and that is designed to assist you in voting your shares.

Notice of Internet Availability of Proxy Materials. As permitted by SEC rules, Homology is making this proxy statement and its 2020 Annual Report available to its stockholders electronically via the Internet. On or about April 29, 2021, we mailed to our stockholders an Internet Notice containing instructions on how to access this proxy statement and our 2020 Annual Report and vote online. If you received an Internet Notice by mail, you will not receive a printed copy of the proxy materials in the mail unless you specifically request them. Instead, the Internet Notice instructs you on how to access and review all of the important information contained in the proxy statement and 2020 Annual Report. The Internet Notice also instructs you on how you may submit your proxy over the Internet. If you received an Internet Notice by mail and would like to receive a printed copy of our proxy materials, you should follow the instructions for requesting such materials contained on the Internet Notice.

Printed Copies of Our Proxy Materials. If you received printed copies of our proxy materials, then instructions regarding how you can vote are contained on the proxy card included in the materials.

Householding. The SEC’s rules permit us to deliver a single set of proxy materials to one address shared by two or more of our stockholders. This delivery method is referred to as “householding” and can result in significant cost savings. To take advantage of this opportunity, we have delivered only one set of proxy materials to multiple stockholders who share an address, unless we received contrary instructions from the impacted stockholders prior to the mailing date. We agree to deliver promptly, upon written or oral request, a separate copy of the proxy materials, as requested, to any stockholder at the shared address to which a single copy of those documents was delivered. If you prefer to receive separate copies of the proxy materials, contact Broadridge Financial Solutions, Inc. at 1-866-540-7095 or in writing at Broadridge, Householding Department, 51 Mercedes Way, Edgewood, New York 11717.

If you are currently a stockholder sharing an address with another stockholder and wish to receive only one copy of future proxy materials for your household, please contact Broadridge at the above phone number or address.

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QUESTIONS AND ANSWERS ABOUT THE 2021 ANNUAL MEETING OF STOCKHOLDERS

Who is entitled to vote at the Annual Meeting?

The Record Date for the Annual Meeting is April 23, 2021. You are entitled to vote at the Annual Meeting only if you were a stockholder of record at the close of business on that date, or if you hold a valid proxy for the Annual Meeting. Each outstanding share of common stock is entitled to one vote for all matters before the Annual Meeting. At the close of business on the Record Date, there were 57,083,955 shares of common stock outstanding and entitled to vote at the Annual Meeting.

What is the difference between being a “record holder” and holding shares in “street name”?

A record holder holds shares in his or her name. Shares held in “street name” means shares that are held in the name of a bank or broker on a person’s behalf.

Am I entitled to vote if my shares are held in “street name”?

Yes. If your shares are held by a bank or a brokerage firm, you are considered the “beneficial owner” of those shares held in “street name.” If your shares are held in street name, these proxy materials are being provided to you by your bank or brokerage firm, along with a voting instruction card if you received printed copies of our proxy materials. As the beneficial owner, you have the right to direct your bank or brokerage firm how to vote your shares, and the bank or brokerage firm is required to vote your shares in accordance with your instructions. If your shares are held in street name, please refer to the information provided by your bank, broker or other nominee on how to submit your voting instructions.

Who can attend the Annual Meeting?

You may attend the Annual Meeting online only if you are a Homology stockholder who is entitled to vote at the Annual Meeting, or if you hold a valid proxy for the Annual Meeting. There will not be a physical meeting location and you will not be able to attend in person. You may attend and participate in the Annual Meeting by visiting the following website: www.virtualshareholdermeeting.com/FIXX2021. To attend and participate in the Annual Meeting, you will need the 16-digit control number included in your Internet Notice, on your proxy card or on the instructions that accompanied your proxy materials. If your shares are held in “street name,” you should contact your bank or broker to obtain your 16-digit control number or otherwise vote through the bank or broker. If you lose your 16-digit control number, you may join the Annual Meeting as a “Guest” but you will not be able to vote, ask questions or access the list of stockholders as of the Record Date. The meeting webcast will begin promptly at 9:00 a.m. Eastern time. We encourage you to access the meeting prior to the start time to allow ample time for check-in procedures.

Why hold a virtual meeting?

In light of the ongoing COVID-19 pandemic, and as part of our effort to maintain a safe and healthy environment for our directors, members of management and stockholders who wish to attend the Annual Meeting, we believe that hosting a virtual meeting this year is in the best interest of the Company and its stockholders. A virtual meeting also enables increased stockholder attendance and participation because stockholders can participate from any location around the world. There will not be a physical meeting location and you will not be able to attend the meeting in person. You will be able to attend the Annual Meeting online and submit your questions by visiting www.virtualshareholdermeeting.com/FIXX2021. You also will be able to vote your shares electronically at the Annual Meeting by following the instructions above.

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

We will have technicians ready to assist you with any technical difficulties you may have accessing the virtual meeting website. If you encounter any technical difficulties with the virtual meeting platform on the meeting day, please call the following applicable number for technical support: 800-586-1548 (United States); 303-562-9288 (International).

Will there be a question and answer session during the Annual Meeting?

As part of the Annual Meeting, we will hold a live Q&A session, during which we intend to answer questions submitted during the meeting that are pertinent to the Company and the meeting matters, as time permits. Only stockholders that have accessed the Annual Meeting as a stockholder (rather than a “Guest”) by following the procedures outlined above in “Who can attend the Annual Meeting?”

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will be permitted to submit questions during the Annual Meeting. Each stockholder is limited to no more than two questions. Questions should be succinct and only cover a single topic. We will not address questions that are, among other things:

Additional information regarding the Q&A session will be available in the “Rules of Conduct” available on the Annual Meeting webpage for stockholders that have accessed the Annual Meeting as a stockholder (rather than a “Guest”) by following the procedures outlined above in “Who can attend the Annual Meeting?”.

How many shares must be present to hold the Annual Meeting?

A quorum must be present at the Annual Meeting for any business to be conducted. The presence at the Annual Meeting, online or by proxy, of the holders of a majority in voting power of the common stock issued and outstanding and entitled to vote on the Record Date will constitute a quorum.

What if a quorum is not present at the Annual Meeting?

If a quorum is not present at the scheduled time of the Annual Meeting, the Chairperson of the Annual Meeting is authorized by our Amended and Restated Bylaws to adjourn the meeting, without the vote of stockholders.

What does it mean if I receive more than one Internet Notice or more than one set of proxy materials?

It means that your shares are held in more than one account at the transfer agent and/or with banks or brokers. Please vote all of your shares. To ensure that all of your shares are voted, for each Internet Notice or set of proxy materials, please submit your proxy by phone, via the Internet, or, if you received printed copies of the proxy materials, by signing, dating and returning the enclosed proxy card in the enclosed envelope.

How do I vote?

Stockholders of Record. If you are a stockholder of record, you may vote:

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Internet and telephone voting facilities for stockholders of record will be available 24 hours a day and will close at 11:59 p.m., Eastern time, on June 16, 2021. To participate in the Annual Meeting, including to vote via the Internet or telephone, you will need the 16-digit control number included on your Internet Notice, on your proxy card or on the instructions that accompanied your proxy materials.

Whether or not you expect to attend the Annual Meeting online, we urge you to vote your shares as promptly as possible to ensure your representation and the presence of a quorum at the Annual Meeting. If you submit your proxy, you may still decide to attend the Annual Meeting and vote your shares electronically.

Beneficial Owners of Shares Held in “Street Name.” If your shares are held in street name through a bank or broker, you will receive instructions on how to vote from the bank or broker. You must follow their instructions in order for your shares to be voted. Internet and telephone voting also may be offered to stockholders owning shares through certain banks and brokers. If your shares are not registered in your own name and you would like to vote your shares electronically at the Annual Meeting, you should contact your bank or broker to obtain your 16-digit control number or otherwise vote through the bank or broker. If you lose your 16-digit control number, you may join the Annual Meeting as a “Guest” but you will not be able to vote, ask questions or access the list of stockholders as of the Record Date. You will need to obtain your own Internet access if you choose to attend the Annual Meeting online and/or vote over the Internet.

Can I change my vote after I submit my proxy?

Yes.

If you are a registered stockholder, you may revoke your proxy and change your vote:

Your most recent proxy card or Internet or telephone proxy is the one that is counted. Your attendance at the Annual Meeting by itself will not revoke your proxy unless you give written notice of revocation to the Secretary before your proxy is voted or you vote electronically at the Annual Meeting.

If your shares are held in street name, you may change or revoke your voting instructions by following the specific directions provided to you by your bank or broker, or you may vote electronically at the Annual Meeting by obtaining a legal proxy from your bank or broker.

Who will count the votes?

A representative of Broadridge Financial Solutions, Inc., our inspector of election, will tabulate and certify the votes.

What if I do not specify how my shares are to be voted?

If you submit a proxy but do not indicate any voting instructions, the persons named as proxies will vote in accordance with the recommendations of the Board of Directors. The Board of Directors’ recommendations are indicated on page 1 of this proxy statement, as well as with the description of each proposal in this proxy statement.

Will any other business be conducted at the Annual Meeting?

We know of no other business that will be presented at the Annual Meeting. If any other matter properly comes before the stockholders for a vote at the Annual Meeting, however, the proxy holders named on the Company’s proxy card will vote your shares in accordance with their best judgment.

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How many votes are required for the approval of the proposals to be voted upon and how will abstentions and broker non-votes be treated?

What is a “vote withheld” and an “abstention” and how will votes withheld and abstentions be treated?

A “vote withheld,” in the case of the proposal regarding the election of directors, or an “abstention,” in the case of the proposal regarding the ratification of the appointment of Deloitte & Touche LLP as our independent registered public accounting firm, represents a stockholder’s affirmative choice to decline to vote on a proposal. Votes withheld and abstentions are counted as present and entitled to vote for purposes of determining a quorum. Votes withheld have no effect on the election of directors. Abstentions have no effect on the ratification of the appointment of Deloitte & Touche LLP.

What are broker non-votes and do they count for determining a quorum?

Generally, broker non-votes occur when shares held by a broker in “street name” for a beneficial owner are not voted with respect to a particular proposal because the broker (1) has not received voting instructions from the beneficial owner and (2) lacks discretionary voting power to vote those shares. A broker is entitled to vote shares held for a beneficial owner on routine matters, such as the ratification of the appointment of Deloitte & Touche LLP as our independent registered public accounting firm, without instructions from the beneficial owner of those shares. On the other hand, absent instructions from the beneficial owner of such shares, a broker is not entitled to vote shares held for a beneficial owner on non-routine matters, such as the election of directors. Broker non-votes count for purposes of determining whether a quorum is present.

Where can I find the voting results of the Annual Meeting?

We plan to announce preliminary voting results at the Annual Meeting and we will report the final results in a Current Report on Form 8-K, which we intend to file with the SEC after the Annual Meeting.

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PROPOSALS TO BE VOTED ON

Proposal 1: Election of Directors

As set forth in our Restated Certificate of Incorporation, the Board of Directors is currently divided into three classes with staggered, three-year terms. At each annual meeting of stockholders, the successors to directors whose terms then expire will be elected to serve from the time of election and qualification until the third annual meeting following election. The current class structure is as follows: Class I, whose term will expire at the 2022 Annual Meeting of Stockholders; Class II, whose term will expire at the 2023 Annual Meeting of Stockholders; and Class III, whose current term will expire at the 2021 Annual Meeting of Stockholders and, if elected at the Annual Meeting, whose subsequent term will expire at the 2024 Annual Meeting of Stockholders. We currently have eight (8) directors on our Board. The current Class I Directors are Jeffrey V. Poulton and Alise S. Reicin, M.D.; the current Class II Directors are Steven Gillis, Ph.D., Richard J. Gregory, Ph.D., and Kush M. Parmar, M.D., Ph.D.; and the current Class III Directors are Matthew R. Patterson, Mary Thistle and Arthur O. Tzianabos, Ph.D.

Our Restated Certificate of Incorporation and Amended and Restated Bylaws provide that the authorized number of directors may be changed only by resolution of the Board of Directors. Any additional directorships resulting from an increase in the number of directors will be distributed among the three classes so that, as nearly as possible, each class will consist of one-third of the directors. The division of our Board of Directors into three classes with staggered three-year terms may delay or prevent a change of our management or a change in control of our Company. Our directors may be removed only for cause by the affirmative vote of the holders of at least two-thirds of our outstanding voting stock entitled to vote in the election of directors.

Nominees for Election as Directors

At the Annual Meeting, three (3) Class III Directors are to be elected to hold office until the Annual Meeting of Stockholders to be held in 2024 and until each director’s successor is elected and qualified or until each director’s earlier death, resignation or removal. We currently have three (3) Class III Directors: Matthew R. Patterson and Mary Thistle, both of whom have served on our Board since 2018, and Arthur O. Tzianabos, Ph.D. who has served on our Board since 2016. The Board has nominated all three director candidates for election as Class III Directors at the Annual Meeting.

If you submit a proxy but do not indicate any voting instructions, the persons named as proxies will vote the shares of common stock represented thereby for the election as Class III Directors of the persons whose names and biographies appear below. In the event that any of Mr. Patterson, Ms. Thistle or Dr. Tzianabos should become unable to serve, or for good cause will not serve, as a director, it is intended that votes will be cast for a substitute nominee designated by our Board or the Board may elect to reduce its size. The Board of Directors has no reason to believe that any of Mr. Patterson, Ms. Thistle or Dr. Tzianabos will be unable to serve if elected. Each of Mr. Patterson, Ms. Thistle and Dr. Tzianabos has consented to being named in this proxy statement and to serve if elected.

Vote required

The proposal regarding the election of directors requires the approval of a plurality of the votes cast. This means that the three nominees receiving the highest number of affirmative “FOR” votes will be elected as Class III Directors. Votes withheld and broker non-votes are not considered to be votes cast and, accordingly, will have no effect on the outcome of the vote on this proposal.

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Recommendation of the Board of Directors

The principal occupations and business experience, for at least the past five years, of each Class III Director nominee for election at the Annual Meeting are as follows:

Matthew R. Patterson

Matthew R. Patterson has served as a member of our Board of Directors since 2018. Mr. Patterson has served as Executive Chairman of the board of directors at Remix Therapeutics, a biotechnology company, since April 2021. Mr. Patterson is the co-founder of Audentes Therapeutics, Inc., a biotechnology company, and served in the role of Strategic Advisor from January 2020 to April 2021. Previously, he served as its Chief Executive Officer from November 2012 until Audentes’ acquisition by Astellas Pharma Inc. in January 2020. Mr. Patterson also served as Audentes’ Chairman of the board of directors and formerly served as President until May 2018. Prior to that, Mr. Patterson was the Entrepreneur-In-Residence at OrbiMed Advisors LLC. Prior to OrbiMed, Mr. Patterson served in roles at Amicus Therapeutics, Inc., BioMarin Pharmaceutical Inc. and Genzyme Corporation. Mr. Patterson serves as a director of Vor Biopharma, Inc. and 5:01 Acquisition Corp., and also serves as a director of several private companies. Mr. Patterson holds a B.A. from Bowdoin College. We believe that Mr. Patterson’s experience in the biotechnology and biopharmaceutical industries, as well as his service on the board of directors of a public company provide him with the qualifications to serve as a director of our company.

Mary Thistle

Mary Thistle has served as a member of our Board of Directors since 2018. Ms. Thistle has served as Special Advisor to the Bill & Melinda Gates Medical Research Institute, a non-profit biotech organization, since the fall of 2020, and previously served as the organization’s Chief of Staff from January 2018 until she assumed her current role. Prior to that, she held senior leadership positions at Dimension Therapeutics, Inc., a gene therapy company, including Chief Operating Officer from 2016 to 2017 and Chief Business Officer from 2015 to 2016. Prior to joining Dimension Therapeutics, Inc., she spent six years at Cubist Pharmaceuticals, Inc., a biopharmaceutical company, where she held various leadership positions, including Senior Vice President, Business Development from 2014 to 2015, Vice President, Business Development from 2012 to 2013 and Senior Director, Business Development from 2009 to 2012. Prior to that, she held various positions at ViaCell, Inc. and PerkinElmer Inc. Ms. Thistle currently serves on the board of directors of Ziopharm Oncology, Inc., as well as the boards of several private companies. Ms. Thistle holds a B.S. in Accounting from the University of Massachusetts, Boston. We believe that Ms. Thistle is qualified to serve on our Board of Directors due to her finance background and industry experience.

Arthur O. Tzianabos, Ph.D.

Arthur O. Tzianabos, Ph.D. has served as our President, Chief Executive Officer and member of our Board of Directors since April 2016. Dr. Tzianabos joined Homology from OvaScience, Inc., a biotechnology company (which has since merged with and into Millendo Therapeutics, Inc.), where he served as President and Chief Scientific Officer from September 2013 to March 2016. Prior to OvaScience, Dr. Tzianabos spent eight years at Shire plc, a biotechnology company, where he served in positions of increasing responsibility, including Senior Director, Discovery Research, Vice President, Program Management and Senior Vice President and Head, Research and Early Development. From 1992 to 2005, Dr. Tzianabos was a faculty member at Harvard Medical School and maintained laboratories at the Channing Laboratory, Brigham and Women’s Hospital and the Department of Microbiology and Molecular Genetics at Harvard Medical School. Dr. Tzianabos currently serves as a director of Stoke Therapeutics, Inc. and is Chairman of the board of directors of Akouos, Inc. Dr. Tzianabos previously served as a director of BIND Therapeutics, Inc. Dr. Tzianabos holds a B.S. in Biology from Boston College and a Ph.D. in Microbiology from the University of New Hampshire. We

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believe Dr. Tzianabos’ extensive academic and clinical experience, as well as his knowledge of the industry, qualifies him to serve on our Board of Directors.

The principal occupations and business experience, for at least the past five years, of our Class I Directors are as follows:

Jeffrey V. Poulton

Jeffrey V. Poulton has served as a member of our Board of Directors since July 2020. Mr. Poulton has served as Executive Vice President and Chief Financial Officer at Alnylam Pharmaceuticals, Inc., a biopharmaceutical company, since August 2019. Prior to joining Alnylam, Mr. Poulton served as Chief Financial Officer of Indigo Agriculture, a plant microbiome company, from January 2018 to April 2019, where he supported the initial commercial scale-up of the business, including expansion outside the U.S. Between 2003 and December 2017, Mr. Poulton held various roles of increasing responsibility at Shire plc, most recently as Chief Financial Officer and a member of Shire’s executive committee and board of directors from January 2015 to December 2017. During his tenure at Shire, Mr. Poulton also led Shire’s rare disease U.S., LATAM and Asia Pacific commercial operations, as well as Shire’s global rare disease business unit. Prior to Shire, Mr. Poulton led corporate finance and business development initiatives in both the gas and electric utilities industry and the materials manufacturing sector, serving in financial leadership positions at Cinergy Corp. and PPG Industries. Mr. Poulton also served in the United States Navy as a Commissioned Officer. Mr. Poulton holds a B.A. in Economics from Duke University and an M.B.A. from Indiana University. We believe that Mr. Poulton is qualified to serve on our Board of Directors due to his finance background and industry experience.

Alise Reicin, M.D.

Alise Reicin, M.D. has served as a member of our Board of Directors since July 2019. Dr. Reicin has served as Chief Executive Officer of Tectonic Therapeutic, Inc., a biotechnology company, since August 2020. Prior to Tectonic, Dr. Reicin served as President, Global Clinical Development at Celgene Corporation, a pharmaceutical company, from November 2018 to December 2019. Prior to Celgene, she served as Head of Global Clinical Development at EMD Serono, a pharmaceutical company, from May 2015 through October 2018. Prior to EMD Serono, Dr. Reicin served as VP, Program Leadership Oncology at Merck and Co., a pharmaceutical company. She holds a B.A. in Biochemistry from Barnard College of Columbia University and an M.D. from Harvard Medical School. We believe that Dr. Reicin’s clinical expertise and leadership roles in the biotechnology and biopharmaceutical industries provide her with the qualifications to serve as a director of our company.

The principal occupations and business experience, for at least the past five years, of our Class II Directors are as follows:

Steven Gillis, Ph.D.

Steven Gillis, Ph.D. has served as a member of our Board of Directors since 2016. Since 2005, Dr. Gillis has been a managing director at ARCH Venture Partners, a venture capital firm. From 1994 to 2005, Dr. Gillis served as Chief Executive Officer and chairman of the board of directors of Corixa Corporation, which he co-founded in October 1994. Previously, Dr. Gillis served as Director, Head of Research and Development, Chief Scientific Officer and acting Chief Executive Officer of Immunex Corporation, which he co-founded, from 1981 until his departure in 1994. As a former director and chairman of Trubion Pharmaceuticals, Inc., Dr. Gillis led its acquisition by Emergent BioSolutions in the fall 2010. Dr. Gillis currently serves as a director of Takeda Pharmaceutical Company

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Limited (and as director of Shire plc prior to its acquisition by Takeda), and serves as a director and chairman of VBI Vaccines Inc. Dr. Gillis also currently serves as a director of several private companies. Dr. Gillis previously served as a director at Pulmatrix, Inc. from 2008 to 2020, at PhaseRx, Inc. from 2008 to 2018 and at bluebird bio, Inc. from 2011 to 2015. Dr. Gillis received his B.A. in Biology and English from Williams College and his Ph.D. in Biological Science from Dartmouth College. We believe that Dr. Gillis’s knowledge of immunology and experience in the venture capital industry, particularly with biotechnology and pharmaceutical companies, qualifies him to serve as a member of our Board of Directors.

Richard J. Gregory, Ph.D.

Richard J. Gregory, Ph.D. has served as a member of our Board of Directors since 2015. Prior to his retirement, Dr. Gregory served as Executive Vice President and Chief Scientific Officer of ImmunoGen, Inc., a biotechnology company, from 2015 until August 2019. Prior to joining ImmunoGen, Inc., he spent 25 years at Genzyme Corporation, a biotechnology company, in roles of increasing responsibility, including Senior Vice President and Head of Research from 2003 until Genzyme Corporation’s acquisition by Sanofi in 2011, and Head of Research and Development for Genzyme from 2011 through 2014. Dr. Gregory serves as a director of ProMIS Neurosciences, Inc. Dr. Gregory received his B.A. in Science from Virginia Tech and holds a Ph.D. from the University of Massachusetts, Amherst, and completed his post-doctoral work at the Worcester Foundation for Experimental Biology. We believe that Dr. Gregory’s experience in the biotechnology and biopharmaceutical industries and his knowledge of immunology qualifies him to serve as a member of our Board of Directors.

Kush M. Parmar, M.D., Ph.D.

Kush M. Parmar, M.D., Ph.D. has served as a member of our Board of Directors since 2015 and as Chairman of the Board since March 2018. Dr. Parmar is a Managing Partner at 5AM Venture Management LLC, an early stage venture capital firm focused on the life sciences, where he has been since 2010. Before joining 5AM, from 2002 to 2010, he was at Harvard Medical School, where he was an NIH-sponsored M.D./Ph.D. physician scientist fellow in the joint Harvard-MIT Health Sciences and Technology Program. Dr. Parmar currently serves on the boards of 5:01 Acquisition Corp. and Akouos, Inc., as well as the boards of numerous private companies. He previously served as a board member or observer for Arvinas, Inc., Achaogen, Inc., Audentes Therapeutics, Inc. (acquired by Astellas Pharma Inc.), Pulmatrix, Inc. and scPharmaceuticals Inc. He is a member of the scientific advisory boards of Penn Medicine, Princeton University’s Department of Molecular Biology, and the Grace Science Foundation, and is a fellow of the Society of Kauffman Fellows. Before joining 5AM, Dr. Parmar completed clinical clerkships at the Massachusetts General & Brigham and Women’s Hospitals, attended courses at Harvard Business School and consulted for an oncology startup. He also founded a non-profit international development organization, the Cruz Blanca Initiative. He holds an A.B. in Molecular Biology and Medieval Studies from Princeton University, a Ph.D. in Experimental Pathology from Harvard University, and an M.D. from Harvard Medical School. We believe that Dr. Parmar’s experience in the life sciences industry, his experience as a venture capitalist and senior executive, as well as his service on the boards of directors of numerous companies provide him with the qualifications to serve as a director of our company.

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Proposal 2: Ratification of Appointment of Independent Registered Public Accounting Firm

Our Audit Committee of the Board of Directors (the “Audit Committee”) has appointed Deloitte & Touche LLP as our independent registered public accounting firm for the fiscal year ending December 31, 2021. Our Board has directed that this appointment be submitted to our stockholders for ratification at the Annual Meeting. Although ratification of our appointment of Deloitte & Touche LLP is not required, we value the opinions of our stockholders and believe that stockholder ratification of our appointment is a good corporate governance practice.

Deloitte & Touche LLP also served as our independent registered public accounting firm for the fiscal year ended December 31, 2020. Neither the accounting firm nor any of its members has any direct or indirect financial interest in or any connection with us in any capacity other than as our auditors, providing audit and non-audit related services. A representative of Deloitte & Touche LLP is expected to attend the Annual Meeting and to have an opportunity to make a statement and be available to respond to appropriate questions from stockholders.

In the event that the appointment of Deloitte & Touche LLP is not ratified by the stockholders, the Audit Committee will consider this fact when it appoints the independent auditors for the fiscal year ending December 31, 2022. Even if the appointment of Deloitte & Touche LLP is ratified, the Audit Committee retains the discretion to appoint a different independent auditor at any time if it determines that such a change is in the interest of the Company.

Vote Required

This proposal requires the affirmative vote of the holders of a majority in voting power of the votes cast affirmatively or negatively. Abstentions are not considered to be votes cast and, accordingly, will have no effect on the outcome of the vote on this proposal. Because brokers have discretionary authority to vote on the ratification of the appointment of Deloitte & Touche LLP, we do not expect any broker non-votes in connection with this proposal.

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