ALECTOR, INC.

131 OYSTER POINT BOULEVARD, SUITE 600

SOUTH SAN FRANCISCO, CA 94080

NOTICE OF ANNUAL MEETING OF STOCKHOLDERS

To Be Held at 8:00 a.m. Pacific Time on Thursday, June 17, 2021

Dear Stockholders of Alector, Inc.:

We cordially invite you to attend the 2021 annual meeting of stockholders (the “Annual Meeting”) of Alector, Inc., a Delaware corporation, which will be held on Thursday, June 17, 2021 at 8:00 a.m. Pacific Time. The safety of our stockholders is important to us, and given the current guidance by public health officials surrounding COVID-19 and group gatherings, this year’s Annual Meeting will be held virtually, via live webcast at https://web.lumiagm.com/209804434 password: alector2021 (cap sensitive), originating from South San Francisco, CA. The Annual Meeting will be held for the following purposes, as more fully described in the accompanying proxy statement:

1. To elect three Class III directors to serve until the 2024 annual meeting of stockholders and until their successors are duly elected and qualified;

2. To ratify the appointment of Ernst & Young LLP as our independent registered public accounting firm for the fiscal year ending December 31, 2021;

3. To conduct an advisory vote to approve named executive officer compensation;

4. To hold an advisory vote on the frequency of future advisory votes on named executive officer compensation; and

5. To transact such other business that may properly come before the Annual Meeting or any adjournments or postponements thereof.

Our Board of Directors has fixed the close of business on April 20, 2021 as the record date for the Annual Meeting. Only stockholders of record on April 20, 2021 are entitled to notice of and to vote at the Annual Meeting. Further information regarding voting rights and the matters to be voted upon is presented in the accompanying proxy statement.

On or about April 28, 2021, we expect to mail to our stockholders a Notice of Internet Availability of Proxy Materials (the “Notice”) containing instructions on how to access our proxy statement and annual report. The Notice provides instructions on how to vote via the Internet or by telephone and includes instructions on how to receive a paper copy of our proxy materials by mail. The accompanying proxy statement and our annual report can be accessed directly at the following Internet address: http://www.astproxyportal.com/ast/22640. All you have to do is enter the control number located on your Notice or proxy card.

YOUR VOTE IS IMPORTANT. Whether or not you plan to attend the Annual Meeting, we urge you to submit your vote via the Internet, telephone or mail as soon as possible.

We appreciate your continued support of Alector, Inc.

By order of the Board of Directors,

Arnon Rosenthal, Ph.D.

Co-founder, Chief Executive Officer and Director

South San Francisco, California

April 28, 2021

TABLE OF CONTENTS

ALECTOR, INC.

QUESTIONS AND ANSWERS ABOUT THE PROXY MATERIALS AND THE ANNUAL MEETING

PROXY STATEMENT

FOR 2021 ANNUAL MEETING OF STOCKHOLDERS

To Be Held at 8:00 a.m. Pacific Time on Thursday, June 17, 2021

This proxy statement and the enclosed form of proxy are furnished in connection with the solicitation of proxies by our Board of Directors for use at the 2021 annual meeting of stockholders of Alector, Inc., a Delaware corporation, and any postponements, adjournments or continuations thereof (the “Annual Meeting”). The Annual Meeting will be held virtually, via live webcast at https://web.lumiagm.com/209804434 password: alector2021 (cap sensitive), originating from South San Francisco, CA. The Notice of Internet Availability of Proxy Materials (the “Notice”) containing instructions on how to access this proxy statement and our annual report is first being mailed on or about April 28, 2021 to all stockholders entitled to vote at the Annual Meeting.

The information provided in the “question and answer” format below is for your convenience only and is merely a summary of the information contained in this proxy statement. You should read this entire proxy statement carefully. Information contained on, or that can be accessed through, our website is not intended to be incorporated by reference into this proxy statement and references to our website address in this proxy statement are inactive textual references only.

Why are you holding a virtual Annual Meeting?

The safety of our stockholders is important to us and given the current guidance by public health officials surrounding COVID-19 and group gatherings, this year’s Annual Meeting will be a “virtual meeting” of stockholders. We have implemented the virtual format in order to facilitate stockholder attendance at our Annual Meeting. We have designed our virtual format to enhance, rather than constrain, stockholder access, participation and communication. For example, the virtual format allows stockholders to communicate with us in advance of, and during, the Annual Meeting so they can ask questions of our board of directors or management.

How do I attend and participate in the annual meeting online?

We will be hosting the meeting via live webcast only at https://web.lumiagm.com/209804434 password: alector2021 (cap sensitive). You will be able to submit your questions and vote your shares electronically during the Annual Meeting.

The webcast will start at 8:00 a.m. Pacific Time. You are encouraged to access the meeting prior to the start time. The webcast will open 15 minutes before the start of the meeting, and you should allow ample time for the check-in procedures. In order to enter the meeting, you will need the control number. The control number will be included in the Notice or on your proxy card if you are a stockholder of record of shares of common stock (as defined below), or included with your voting instructions received from your broker, bank or other agent if you hold your shares of common stock in a “street name.” Instructions on how to attend and participate online are available at https://web.lumiagm.com/209804434 password: alector2021 (cap sensitive).

How can I get help if I have trouble checking in or listening to the meeting online?

If you encounter any difficulties accessing the virtual meeting during the check-in or meeting time, please call the technical support number that will be posted on the log-in page.

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What matters am I voting on?

You will be voting on:

How does the Board of Directors recommend I vote on these proposals?

Our Board of Directors recommends a vote:

Who is entitled to vote?

Holders of our common stock as of the close of business on April 20, 2021, the record date for the Annual Meeting, may vote at the Annual Meeting. As of the record date, there were 79,760,655 shares of our common stock outstanding. In deciding all matters at the Annual Meeting, each stockholder will be entitled to one vote for each share of our common stock held by them on the record date. We do not have cumulative voting rights for the election of directors.

Registered Stockholders. If shares of our common stock are registered directly in your name with our transfer agent, you are considered the stockholder of record with respect to those shares and the Notice was provided to you directly by us. As the stockholder of record, you have the right to grant your voting proxy directly to the individuals listed on the proxy card or vote on your own behalf at our virtual Annual Meeting. Throughout this proxy statement, we refer to these registered stockholders as “stockholders of record.”

Street Name Stockholders. If shares of our common stock are held on your behalf in a brokerage account or by a bank or other nominee, you are considered to be the beneficial owner of shares that are held in “street name,” and the Notice was forwarded to you by your broker or nominee, who is considered the stockholder of record with respect to those shares. As the beneficial owner, you have the right to direct your broker, bank or other nominee as to how to vote your shares. Beneficial owners are also invited to attend our virtual Annual Meeting. However, since a beneficial owner is not the stockholder of record, you may not vote your shares of our common stock on your own behalf at the Annual Meeting unless you follow your broker’s procedures for obtaining a legal proxy. If you request a printed copy of our proxy materials by mail, your broker, bank or other nominee will provide a voting instruction form for you to use. Throughout this proxy statement, we refer to stockholders who hold their shares through a broker, bank or other nominee as “street name stockholders.”

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How many votes are needed for approval of each proposal?

What is the quorum?

A quorum is the minimum number of shares required to be present at the Annual Meeting for the Annual Meeting to be properly held under our bylaws and Delaware law. The presence (including by proxy) of a majority of all issued and outstanding shares of our common stock entitled to vote at the Annual Meeting will constitute a quorum at the Annual Meeting. Abstentions, withhold votes and broker non-votes are counted as shares present and entitled to vote for purposes of determining a quorum.

How do I vote?

If you are a stockholder of record, there are four ways to vote:

Even if you plan to participate in our virtual Annual Meeting, we recommend that you also vote by proxy so that your vote will be counted if you later decide not to participate in the Annual Meeting.

If you are a street name stockholder, you will receive voting instructions from your broker, bank or other nominee. You must follow the voting instructions provided by your broker, bank or other nominee in order to instruct your broker, bank or other nominee on how to vote your shares. Street name stockholders should

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generally be able to vote by returning an instruction card, or by telephone or on the Internet. However, the availability of telephone and Internet voting will depend on the voting process of your broker, bank or other nominee. As discussed above, if you are a street name stockholder, you may not vote your shares on your own behalf at the Annual Meeting unless you obtain a legal proxy from your broker, bank or other nominee.

Can I change my vote?

Yes. If you are a stockholder of record, you can change your vote or revoke your proxy any time before the Annual Meeting by:

Francisco, California 94080.

If you are a street name stockholder, your broker, bank or other nominee can provide you with instructions on how to change your vote.

You may also change your vote or revoke your proxy by attending our virtual Annual Meeting and voting online during the meeting. Simply attending the meeting will not, by itself, revoke your proxy.

What is the effect of giving a proxy?

Proxies are solicited by and on behalf of our Board of Directors. Arnon Rosenthal and Shehnaaz Suliman have been designated as proxy holders by our Board of Directors. When proxies are properly dated, executed and returned, the shares represented by such proxies will be voted at the Annual Meeting in accordance with the instructions of the stockholder. If no specific instructions are given, however, the shares will be voted in accordance with the recommendations of our Board of Directors as described above. If any matters not described in this proxy statement are properly presented at the Annual Meeting, the proxy holders will use their own judgment to determine how to vote the shares. If the Annual Meeting is adjourned, the proxy holders can vote the shares on the new Annual Meeting date as well, unless you have properly revoked your proxy instructions, as described above.

Why did I receive a Notice of Internet Availability of Proxy Materials instead of a full set of proxy materials?

In accordance with the rules of the Securities and Exchange Commission (“SEC”), we have elected to furnish our proxy materials, including this proxy statement and our annual report, primarily via the Internet. The Notice containing instructions on how to access our proxy materials is first being mailed on or about April 28, 2021 to all stockholders entitled to vote at the Annual Meeting. Stockholders may request to receive all future proxy materials in printed form by mail or electronically by e-mail by following the instructions contained in the Notice. We encourage stockholders to take advantage of the availability of our proxy materials on the Internet to help reduce the environmental impact and cost of our annual meetings of stockholders.

How are proxies solicited for the Annual Meeting?

Our Board of Directors is soliciting proxies for use at the Annual Meeting. All expenses associated with this solicitation will be borne by us. We will reimburse brokers or other nominees for reasonable expenses that they incur in sending our proxy materials to you if a broker, bank or other nominee holds shares of our common stock

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on your behalf. In addition, our directors and employees may also solicit proxies in person, by telephone, or by other means of communication. Our directors and employees will not be paid any additional compensation for soliciting proxies.

How may my brokerage firm or other intermediary vote my shares if I fail to provide timely directions?

Brokerage firms and other intermediaries holding shares of our common stock in street name for their customers are generally required to vote such shares in the manner directed by their customers. In the absence of timely directions, your broker will have discretion to vote your shares on our sole “routine” matter: the proposal to ratify the appointment of Ernst & Young LLP as our independent registered public accounting firm. Your broker will not have discretion to vote on the election of directors, on the approval, on an advisory basis, of the named executive officer compensation, or on the advisory vote on the frequency of future advisory votes on named executive officer compensation, which are “non-routine” matters, absent direction from you.

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

We expect to announce voting results at the Annual Meeting. We will also disclose voting results on a Current Report on Form 8-K that we will file with the SEC within four business days after the Annual Meeting.

I share an address with another stockholder, and we received only one paper copy of the proxy materials. How may I obtain an additional copy of the proxy materials?

We have adopted a procedure called “householding,” which the SEC has approved. Under this procedure, we deliver a single copy of the Notice and, if applicable, our proxy materials to multiple stockholders who share the same address unless we have received contrary instructions from one or more of the stockholders. This procedure reduces our printing costs, mailing costs and fees. Stockholders who participate in householding will continue to be able to access and receive separate proxy cards. Upon written or oral request, we will deliver promptly a separate copy of the Notice and, if applicable, our proxy materials to any stockholder at a shared address to which we delivered a single copy of any of these materials. To receive a separate copy, or, if a stockholder is receiving multiple copies, to request that we only send a single copy of the Notice and, if applicable, our proxy materials, such stockholder may contact us at the following address:

Alector, Inc.

Attention: Investor Relations

131 Oyster Point Boulevard, Suite 600

South San Francisco, California 94080

Tel: (415) 231-5660

Street name stockholders may contact their broker, bank or other nominee to request information about householding.

What is the deadline to propose actions for consideration at next year’s annual meeting of stockholders or to nominate individuals to serve as directors?

Stockholder Proposals

Stockholders may present proper proposals for inclusion in our proxy statement and for consideration at the next annual meeting of stockholders by submitting their proposals in writing to our Secretary in a timely manner. For a stockholder proposal to be considered for inclusion in our proxy statement for our 2022 annual meeting of stockholders, our Secretary must receive the written proposal at our principal executive offices not later than December 29, 2021. In addition, stockholder proposals must comply with the requirements of Rule 14a-8

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regarding the inclusion of stockholder proposals in company-sponsored proxy materials. Stockholder proposals should be addressed to:

Alector, Inc.

Attention: Secretary

131 Oyster Point Boulevard, Suite 600

South San Francisco, California 94080

Tel: (415) 231-5660

Our bylaws also establish an advance notice procedure for stockholders who wish to present a proposal before an annual meeting of stockholders but do not intend for the proposal to be included in our proxy statement. Our bylaws provide that the only business that may be conducted at an annual meeting of stockholders is business that is (i) specified in our proxy materials with respect to such meeting, (ii) otherwise properly brought before such meeting by or at the direction of our Board of Directors, or (iii) properly brought before such meeting by a stockholder of record entitled to vote at the annual meeting who has delivered timely written notice to our Secretary, which notice must contain the information specified in our bylaws. To be timely for our 2022 annual meeting of stockholders, our Secretary must receive the written notice at our principal executive offices:

In the event that we hold our 2022 annual meeting of stockholders more than 30 days before or more than 60 days after the one-year anniversary of the Annual Meeting, notice of a stockholder proposal that is not intended to be included in our proxy statement must be received no earlier than the close of business on the 120th day before our 2021 annual meeting of stockholders and no later than the close of business on the later of the following two dates:

If a stockholder who has notified us of his, her or its intention to present a proposal at an annual meeting does not appear to present his, her or its proposal at such annual meeting, we are not required to present the proposal for a vote at such annual meeting.

Nomination of Director Candidates

You may propose director candidates for consideration by our corporate governance and nominating committee. Any such recommendations should include the nominee’s name and qualifications for membership on our Board of Directors and should be directed to our Secretary at the address set forth above. For additional information regarding stockholder recommendations for director candidates, see “Board of Directors and Corporate Governance—Stockholder Recommendations for Nominations to the Board of Directors.”

In addition, our bylaws permit stockholders to nominate directors for election at an annual meeting of stockholders. To nominate a director, the stockholder must provide the information required by our bylaws. In addition, the stockholder must give timely notice to our Secretary in accordance with our bylaws, which, in general, require that the notice be received by our Secretary within the time periods described above under “Stockholder Proposals” for stockholder proposals that are not intended to be included in a proxy statement.

Availability of Bylaws

A copy of our amended and restated bylaws may be obtained by accessing our filings on the SEC’s website at www.sec.gov. You may also contact our Secretary at our principal executive offices for a copy of the relevant bylaw provisions regarding the requirements for making stockholder proposals and nominating director candidates.

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BOARD OF DIRECTORS AND CORPORATE GOVERNANCE

Our business affairs are managed under the direction of our Board of Directors, which is currently composed of eight members. Five of our directors are independent within the meaning of the listing standards of the NASDAQ Global Select Market (NASDAQ). Our Board of Directors is divided into three staggered classes of directors. At each annual meeting of stockholders, a class of directors will be elected for a three-year term to succeed the same class whose term is then expiring.

The following table sets forth the names and certain other information about each of the nominees for Class III director. The names of and certain other information about the continuing members of our Board of Directors are also set forth below. All information is as of March 1, 2021:

Nominees for Director

Tillman Gerngross, Ph.D. Dr. Gerngross co-founded Alector in 2013 and has served as a member of our Board of Directors and as Chairperson since 2013. Dr. Gerngross is a founder, director, and executive officer of numerous biotechnology companies. He is a founder and currently serving as Chief Executive Officer and as a director of Adimab, LLC. He is also a founder and Chairman of the board of directors of Avitide, Inc., Amagma, Inc., Ankyra Therapeutics, Inc., and Adagio Therapeutics, Inc. Dr. Gerngross previously served on the board of directors of Arsanis, Inc., a publicly traded biopharmaceutical company, from 2010 to 2019, Dr. Gerngross is currently a Venture Partner at SV Life Sciences Advisors, LLC, which he joined in 2006. Dr. Gerngross co-founded GlycoFi, Inc. and served as its Chief Scientific Officer from 2000 to 2006 until it was acquired by Merck & Company, Inc. Dr. Gerngross currently teaches at the School of Engineering at Dartmouth College, where he has taught since 1998. Dr. Gerngross attended the Technical University of Vienna, Austria, where he received a B.S. and M.S. in Chemical Engineering and a Ph.D. in Molecular Biology.

We believe Dr. Gerngross is qualified to serve on our Board of Directors because of the perspective and experience he provides as one of our founders, his expertise and experience in antibody drug discovery and development, his experience as a founder and director of other life sciences companies, his educational background, and his experience working in the venture capital industry.

Richard Scheller, Ph.D. Dr. Scheller has served as a member of our Board of Directors since October 2018 and has served as co-chair of our Strategic Portfolio Advice and Review Committee (SPARC) since December 2019.

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Dr. Scheller has served as the Chairman of Research and Development at BridgeBio Pharma LLC, a publicly traded biotechnology company, since January 2019 and as a member of its board of directors since January 2018. Dr. Scheller previously served as Chief Scientific Officer at 23andMe, a personal genetics company, from April 2015 to April 2019. Previously, Dr. Scheller was the Executive Vice President of Research and Early Development and a member of the Executive Committee at Genentech, Inc. from February 2001 to December 2014. From January 2009 to December 2014, Dr. Scheller was also a member of the Enlarged Executive Committee at Hoffmann-La Roche Ltd. Since February 2015, Dr. Scheller has served as a member of the board of directors for ORIC Pharmaceuticals, Inc. Dr. Scheller served as a member of the board of directors for Xenon Pharmaceuticals Inc. from March 2015 to 2019. Dr. Scheller’s research on elucidating the molecular machinery and regulatory mechanism that underlie the release of neurotransmitters earned him the 2013 Albert Lasker Basic Medical Research Award. He is a member of the National Academy of Sciences and a member of the National Academy of Medicine. Dr. Scheller holds a Ph.D. in Chemistry (1980) from the California Institute of Technology and B.Sc. in Biochemistry (1975) from the University of Wisconsin-Madison. He completed his post-doctorate in Biology at Caltech and his postdoctorate in Molecular Neurobiology at Columbia University.

We believe Dr. Scheller is qualified to serve on our Board of Directors because of his scientific background and his senior management experience in the pharmaceutical industry.

Louis J. Lavigne, Jr. Mr. Lavigne has served as a member of our Board of Directors and as our Lead Independent Director since October 2018. Mr. Lavigne has been Managing Director of Lavrite, LLC, a management consulting firm specializing in the areas of corporate finance, accounting, growth strategy, and management, since 2005 and since 2019 Laman Partners, LLC. Mr. Lavigne served in various executive capacities with Genentech, Inc. for over 20 years, including Chief Financial Officer from 1988 to 2005, Executive Vice President from 1997 to 2005, Senior Vice President from 1994 to 1997, Vice President from 1986 to 1994, and Controller from 1983 to 1986. He has served as a member of the board of directors of Zynga Inc., a social game company, since 2015, including as audit committee chairman since 2015 and as a member of the nominating and governance committee since 2020; and since 2009 as a member of the board of directors and now a member of the nominating and governance committee of Accuray Incorporated, a radiation oncology company, and as the lead director since August, 2020 and since December, 2019 chairman of the audit committee of Rodan + Fields, LLC a private skincare company where he has been a director since June 2015. Within the last five years, Mr. Lavigne also served on the board of directors, the audit committee, and the science and technology committee of Allergan, Inc., a global health care company, from 2005 until its acquisition by Actavis plc in 2015; as a director and chair of the audit committee of NovoCure Limited, an oncology company, from 2013 until October 2018; as a director, chair of the compensation committee, and member of the audit committee of Assertio Therapeutics, Inc., a pharmaceutical company, from July 2013 until his resignation in May 2019; and as a director, chair of the audit committee, and member of the compensation committee of DocuSign Inc., an eSignature transaction management company, July 2013 to May 2020. Mr. Lavigne is the former chairman and board member of the UCSF Benioff Children’s Hospitals and the UCSF Benioff Children’s Hospitals Foundation. Mr. Lavigne holds a B.S. in Business Administration from Babson College and an M.B.A. from Temple University.

We believe Mr. Lavigne is qualified to serve on our Board of Directors because of his extensive experience in business operations and management, strategy, finance, accounting, and public company governance as a chief financial officer of a large, complex publicly-traded company and his extensive board leadership positions with a number of public company boards and audit committees.

Continuing Directors

Arnon Rosenthal, Ph.D. Dr. Rosenthal co-founded Alector in 2013 and has served as a member of our board of directors, as Chief Executive Officer, and as our President since 2013. Dr. Rosenthal co-founded Annexon Biosciences, Inc. and served as its acting Chief Executive Officer from August 2011 to December 2014 and served as a member of the board of directors, including as Chairman from August 2011 February 2017.

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Dr. Rosenthal co-founded Rinat Neuroscience Corporation (acquired by Pfizer Inc. in August 2006), and served as President, Chief Scientific Officer and as a member of the board of directors from August 2001 to August 2006. From January 1985 to August 2001, Dr. Rosenthal served in various roles at Genentech, Inc., where he ultimately served as Staff Scientist and was appointed as a permanent member of Genentech’s Research Review Committee where his team discovered the target for the cancer drug Erivedge. Dr. Rosenthal conducted his post-doctoral fellowship at Genentech, Inc. He holds a Ph.D. in biology from the Hebrew University of Jerusalem.

We believe Dr. Rosenthal is qualified to serve on our Board of Directors because of the perspective and experience he provides as one of our founders and as our Chief Executive Officer, his experience as a founder and director of other life sciences companies, his educational background, as well as his broad experience within the pharmaceutical industry, particularly in the area of neuroscience and drug discovery and development.

Paula Hammond, Ph.D. Dr. Hammond has served as a member of our Board of Directors since March 2020. Dr. Hammond is the David H. Koch Chair Professor of Engineering at the Massachusetts Institute of Technology (MIT), where she has been a faculty member since 1995, and she has served as the Head of the Department of Chemical Engineering at MIT since 2016. She is a member of MIT’s David H. Koch Institute for Integrative Cancer Research and a founding member of the MIT Institute for Soldier Nanotechnology. She also served as the Associate Head of the Chemical Engineering Department at MIT from 2008 to 2011. Dr. Hammond was the recipient of the 2013 AIChE Charles M. A. Stine Award, which is bestowed annually to a leading researcher in recognition of outstanding contributions to the field of materials science and engineering, the 2014 Alpha Chi Sigma Award for Chemical Engineering Research, and the Margaret Rousseau Award for Lifetime Achievement by a Woman Chemical Engineer in 2019. She received the Department of Defense Ovarian Cancer Teal Innovator Award in 2013, which supports a single visionary individual from any field principally outside of ovarian cancer to focus his/her creativity, innovation, and leadership on ovarian cancer research. She was named a Fellow of the American Physical Society, the American Institute of Biological and Medical Engineering, and the American Chemical Society, Division of Polymer Chemistry. Dr. Hammond was elected into the National Academy of Sciences in 2019, the National Academy of Engineering in 2017, the National Academy of Medicine in 2016, and the 2013 Class of the American Academy of Arts and Sciences. Dr. Hammond holds an M.S. in Chemical Engineering from the Georgia Institute of Technology and a Ph.D. and a S.B. in Chemical Engineering from MIT. Professor Hammond has published over 330 papers, and over 20 patent applications. She is the cofounder and member of the Scientific Advisory Board of LayerBio, Inc., a member of the Scientific Advisory Board of Moderna Therapeutics and Bambu Global, and an advisor for Catalio Capital Management.

We believe Dr. Hammond is qualified to serve on our Board of Directors based on her scientific background and experience as an internationally recognized expert in the field of chemical engineering and for her work in the field of cancer research.

Terry McGuire. Mr. McGuire has served as a member of our Board of Directors since 2013. Additionally, Mr. McGuire is a Founding Partner of Polaris Partners, a venture capital firm investing in technology and healthcare companies across all stages of development, where he has worked since 1996. Mr. McGuire has served on the board of directors of Cyclerion, Inc., a publicly traded biotechnology company, since January 2019. Mr. McGuire served on the board of directors of Ironwood Pharmaceuticals, Inc., a publicly traded drug manufacturer, from 1998 to 2019; on the board of directors of Acceleron Pharma, Inc., a publicly traded drug manufacturer, from 2005 to 2017; on the board of directors of Pulmatrix, Inc., a publicly traded biopharmaceutical company, from 2016 to 2019 and on the board of directors of Arsanis, Inc., a publicly traded biopharmaceutical company, from 2011 to 2019. Mr. McGuire is emeritus Chairman of the National Venture Capital Association and Chairman of the Global Ventures Capital Congress and is a member of the board of the Thayer School of Engineering at Dartmouth College. He also sits on the boards of Massachusetts Institute of Technology’s The David H. Koch Institute for Integrative Cancer Research, The Arthur Rock Center for Entrepreneurship at Harvard Business School and The Healthcare Initiative Advisory Board. Mr. McGuire holds an M.B.A. from Harvard Business School, a M.S. in engineering from the Thayer School at Dartmouth College, and a B.S. in physics and economics from Hobart College.

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We believe Mr. McGuire is qualified to serve on our Board of Directors because of his expertise and experience in the biotechnology industry through his role as a Founding Partner of Polaris Partners and his cumulative career in venture capital over a period spanning over 35 years, in which he has been involved in the evaluation, investment and oversight of numerous biotechnology companies, as well as his experience as a director of several biotechnology companies, including other public companies.

David Wehner. Mr. Wehner has served as a member of our Board of Directors since October 2018. He has served as Chief Financial Officer of Facebook, Inc. since June 2014. Mr. Wehner joined Facebook, Inc. in November 2012 as Vice President, Corporate Finance and Business Planning. From August 2010 until November 2012, Mr. Wehner served as Chief Financial Officer at Zynga Inc., a provider of social game services. From February 2001 to July 2010, Mr. Wehner served in various positions at Allen & Company, an investment bank, including as a Managing Director from November 2006 to July 2010 and as a director from December 2005 to November 2006. Mr. Wehner holds an M.S. in applied physics from Stanford University and a B.S. in chemistry from Georgetown University.

We believe Mr. Wehner is qualified to serve on our Board of Directors based on his substantial executive, strategy, finance, and operational experience.

Kristine Yaffe, M.D. Dr. Yaffe has served as a member of our board directors since August 2019. Dr. Yaffe is currently a professor of psychiatry, neurology, and epidemiology at the University of California, San Francisco (UCSF) and has served in that role since 2007. Dr. Yaffe has also served as the Roy and Marie Scola Endowed Chair since 2009 and Vice Chair in Psychiatry at UCSF since 2016. Dr. Yaffe has received numerous awards for her groundbreaking contributions to the field including the American Academy of Neurology Potamkin Prize for Research in Pick’s, Alzheimer’s, and Related Diseases. Dr. Yaffe holds a B.S. in biology-psychology from Yale University and an M.D. from the University of Pennsylvania School of Medicine and has completed residencies in neurology and psychiatry at UCSF. Dr. Yaffe was elected to the National Academy of Medicine in 2019.

We believe Dr. Yaffe is qualified to serve on our Board of Directors based on her experience as an internationally recognized expert in the field of cognitive aging, neurodegeneration, and dementia.

Director Independence

Our common stock is listed on NASDAQ. Under the rules of NASDAQ, independent directors must comprise a majority of a listed company’s board of directors. In addition, the rules of NASDAQ require that, subject to specified exceptions, each member of a listed company’s audit, compensation and corporate governance, and nominating committees be independent. Audit committee members and compensation committee members must also satisfy the independence criteria set forth in Rule 10A-3 and Rule 10C-1, respectively, under the Securities Exchange Act of 1934, as amended (the Exchange Act). Under the rules of NASDAQ, a director will only qualify as an “independent director” if, in the opinion of that company’s board of directors, that person does not have a relationship that would interfere with the exercise of independent judgment in carrying out the responsibilities of a director.

To be considered independent for purposes of Rule 10A-3 and under the rules of NASDAQ, 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: (1) accept, directly or indirectly, any consulting, advisory, or other compensatory fee from the listed company or any of its subsidiaries or (2) be an affiliated person of the listed company or any of its subsidiaries.

To be considered independent for purposes of Rule 10C-1 and under the rules of NASDAQ, the board of directors must affirmatively determine that each member of the compensation committee is independent, including a consideration of all factors specifically relevant to determining whether the director has a relationship to the 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: (1) the source of

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compensation of such director, including any consulting, advisory, or other compensatory fee paid by the company to such director and (2) whether such director is affiliated with the company, a subsidiary of the company or an affiliate of a subsidiary of the company.

Our Board of Directors undertook a review of its composition, the composition of its committees, and the independence of our directors and considered whether any director has a material relationship with us that could compromise his or her ability to exercise independent judgment in carrying out his or her responsibilities. 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 Drs. Hammond and Yaffe and Messrs. Lavigne, McGuire, and Wehner do not have a relationship that would interfere with the exercise of independent judgment in carrying out the responsibilities of a director and that each of these directors is “independent” as that term is defined under the rules of NASDAQ.

In making these determinations, our Board of Directors considered the current and prior relationships that each non-employee director has with our company and all other facts and circumstances our Board of Directors deemed relevant in determining their independence, including the beneficial ownership of our capital stock by each non-employee director, and the transactions involving them described in the section titled “Related Party Transactions.” There are no family relationships among any of our nominees for director, directors, or executive officers.

Lead Independent Director

Our Board of Directors has appointed Louis J. Lavigne, Jr. to serve as our Lead Independent Director. As a general matter, our Board of Directors believes that appointing a Lead Independent Director, when either our Chief Executive Officer serves as Chairman or when our Chairman is not independent, creates an environment that encourages objective oversight of management’s performance and enhances the effectiveness of our Board of Directors as a whole. As Lead Independent Director, Mr. Lavigne will preside over periodic meetings of our independent directors, serve as a liaison between our Chairperson, Chief Executive Officer, and our independent directors, and perform such additional duties as our Board of Directors may otherwise determine and delegate.

Role of the Board in Risk Oversight

Risk is inherent with every business, and we face a number of risks, including strategic, financial, business and operational, legal and compliance, and reputational. We have designed and implemented processes to manage risk in our operations. Management is responsible for the day-to-day management of risks that we face, while our Board of Directors, as a whole and assisted by its committees, has responsibility for the oversight of risk management. In its risk oversight role, our Board of Directors has the responsibility to satisfy itself that the risk management processes designed and implemented by management are appropriate and functioning as designed.

Our Board of Directors is responsible for general oversight of risks and regular review of information regarding our risks. The audit committee is responsible for overseeing the management of risks relating to accounting matters and financial reporting and potential conflicts of interest. The compensation committee is responsible for overseeing the management of risks relating to our executive compensation plans and arrangements. The corporate governance and nominating committee is responsible for overseeing the management of risks associated with the independence of our Board of Directors. Although each committee is responsible for evaluating certain risks and overseeing the management of such risks, our entire Board of Directors is regularly informed through discussions from committee members about such risks.

Our Board of Directors believes that open communication between management and our Board of Directors is essential for effective risk management and oversight. Our Board of Directors meets with our Chief Executive Officer and other members of the senior management team at the meetings of our Board of Directors, where, among other topics, they discuss strategy and risks facing us, as well at such other times as they deemed

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appropriate. Our Board of Directors believes its administration of its risk oversight function has not negatively affected the Board of Directors’ leadership structure.

Executive Sessions of Independent Directors

In order to promote open discussion among independent directors, our Board of Directors has a policy of conducting executive sessions of independent directors on a periodic basis, and typically has such a session after each regularly scheduled board meeting. The Lead Independent Director of our Board of Directors is the presiding director over these executive sessions.

Board Meetings and Committees

During the fiscal year ended December 31, 2020, our Board of Directors held six meetings (including regularly scheduled and special meetings), and each director attended at least 75% of the aggregate of (i) the total number of meetings of our Board of Directors held during the period for which he or she has been a director and (ii) the total number of meetings held by all committees of our Board of Directors on which he or she served during the periods that he or she served. Although we do not have a formal policy regarding attendance by members of our Board of Directors at annual meetings of stockholders, we encourage our directors to attend. All of our directors attended our 2020 annual meeting of stockholders in person or via teleconference.    

Our Board of Directors has established an audit committee, a compensation committee, and a corporate governance and nominating committee, each of which has the composition and the responsibilities described below.

Audit Committee

The members of our audit committee are Messrs. Lavigne, McGuire, and Wehner. Mr. Lavigne is the chairperson of our audit committee and together with Mr. Wehner, are our audit committee financial experts, as that term is defined under the SEC rules implementing Section 407 of SOX, and both possess financial sophistication, as defined under the rules of NASDAQ. Our audit committee oversees our corporate accounting and financial reporting process and assists our Board of Directors in monitoring our financial systems. The Company’s management is responsible for preparing our financial statements, and the independent auditor is responsible for auditing and reviewing those financial statements. The audit committee is responsible for assisting the Board in overseeing the conduct of these activities by management and the independent auditor. Our audit committee also:

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Our audit committee operates under a written charter, which satisfies the applicable rules of the SEC and the listing standards of NASDAQ. A copy of the charter of our audit committee is available on our website at https://investors.alector.com. During the fiscal year ended December 31, 2020, our audit committee held four meetings.

Compensation Committee

The members of our compensation committee are Dr. Hammond and Messrs. Lavigne and Wehner. Mr. Wehner is the chairperson of our compensation committee. Our compensation committee oversees our compensation policies, plans, and benefits programs. The compensation committee also:

Our compensation committee operates under a written charter, which satisfies the applicable rules of the SEC and the listing standards of NASDAQ. A copy of the charter of our compensation committee is available on our website at https://investors.alector.com. During the fiscal year ended December 31, 2020, our compensation committee held six meetings and acted by unanimous written consent eight times.

Corporate Governance and Nominating Committee

The members of our corporate governance and nominating committee are Dr. Yaffe and Mr. McGuire. Mr. McGuire is the chairperson of our corporate governance and nominating committee. Our corporate governance and nominating committee oversees and assists our Board of Directors in reviewing and recommending nominees for election as directors. Specifically, the corporate governance and nominating committee:

Our corporate governance and nominating committee operates under a written charter, which satisfies the applicable rules of the SEC and the listing standards of NASDAQ. A copy of the charter of our corporate governance and nominating committee is available on our website at https://investors.alector.com. During the fiscal year ended December 31, 2020, our corporate governance and nominating committee held four meetings.

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Compensation Committee Interlocks and Inside Participation

None of the members of our compensation committee is or has been an officer or employee of our company. None of our executive officers currently serves, or in the past fiscal year has served, as a member of the board of directors or compensation committee (or other board committee performing equivalent functions or, in the absence of any such committee, the entire board of directors) of any entity that has one or more executive officers serving on our Board of Directors or compensation committee.

Considerations in Evaluating Director Nominees

Our corporate governance and nominating committee uses a variety of methods for identifying and evaluating director nominees. In its evaluation of director candidates, our corporate governance and nominating committee will consider the current size and composition of our Board of Directors and the needs of our Board of Directors and the respective committees of our Board of Directors. Some of the qualifications that our corporate governance and nominating committee considers include, without limitation, issues of character, integrity, judgment, diversity of experience, independence, area of expertise, corporate experience, length of service, potential conflicts of interest, and other commitments. Nominees must also have the ability to offer advice and guidance to management and be leaders in the companies or institutions with which they are affiliated. Director candidates must have sufficient time available in the judgment of our corporate governance and nominating committee to perform all board of director and committee responsibilities. Members of our Board of Directors are expected to prepare for, attend, and participate in all Board of Director and applicable committee meetings. Other than the foregoing, there are no stated minimum criteria for director nominees, although our corporate governance and nominating committee may also consider such other factors as it may deem, from time to time, are in our and our stockholders’ best interests.

Although our Board of Directors does not maintain a specific policy with respect to board diversity, our Board of Directors believes that our Board of Directors should be a diverse body, and our corporate governance and nominating committee may consider such factors as differences in professional background, education, skill, and other individual qualities and attributes that contribute to the total mix of viewpoints and experience represented on our Board of Directors. In making determinations regarding nominations of directors, our corporate governance and nominating committee may take into account the benefits of diverse viewpoints. Our corporate governance and nominating committee also considers these and other factors as it oversees the annual board of director and committee evaluations. After completing its review and evaluation of director candidates, our corporate governance and nominating committee recommends to our full Board of Directors the director nominees for selection.

Stockholder Recommendations for Nominations to the Board of Directors

Our corporate governance and nominating committee will consider director candidates recommended by stockholders holding at least 1% of the fully diluted capitalization of our company continuously for at least 12 months prior to the date of the submission of the recommendation, so long as such recommendations comply with our amended and restated certificate of incorporation and bylaws and applicable laws, rules, and regulations, including those promulgated by the SEC. Our corporate governance and nominating committee will evaluate such recommendations in accordance with its charter, our bylaws, our policies and procedures for director candidates, as well as the regular director nominee criteria described above. Eligible stockholders wishing to recommend a candidate for nomination should contact our Secretary in writing. Such recommendations must include information about the candidate and any relationships between the candidate and our company, a statement of support by the recommending stockholder, evidence of the recommending stockholder’s ownership of our common stock, and a signed letter from the candidate confirming willingness to serve on our Board of Directors. Our corporate governance and nominating committee has discretion to decide which individuals to recommend for nomination as directors.

Under our bylaws, stockholders may also nominate persons for our Board of Directors. Any nomination must comply with the requirements set forth in our bylaws and should be sent in writing to our Secretary at Alector,

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Inc., 131 Oyster Point Boulevard, Suite 600, South San Francisco, California 94080. To be timely for our 2022 annual meeting of stockholders, our Secretary must receive the nomination no earlier than February 12, 2022 and no later than March 14, 2022.

Communications with the Board of Directors

Interested parties wishing to communicate with our Board of Directors or with an individual member or members of our Board of Directors may do so by writing to our Board of Directors or to the particular member or members of our Board of Directors, and mailing the correspondence to our Secretary at Alector, Inc., 131 Oyster Point Boulevard, Suite 600, South San Francisco, California 94080. Our Secretary, in consultation with appropriate members of our Board of Directors as necessary, will review all incoming communications and, if appropriate, such communications will be forwarded to the appropriate member or members of our Board of Directors, or if none is specified, to the Chair of our Board of Directors.

Corporate Governance Guidelines and Code of Business Conduct and Ethics

Our Board of Directors has adopted Corporate Governance Guidelines that address items such as the qualifications and responsibilities of our directors and director candidates and corporate governance policies and standards applicable to us in general. In addition, our Board of Directors has adopted a Code of Business Conduct and Ethics that applies to all of our employees, officers and directors, including our Chief Executive Officer, President and Chief Operating Officer, and other executive and senior financial officers. The full text of our Corporate Governance Guidelines and our Code of Business Conduct and Ethics is posted on the Corporate Governance portion of our website at https://investors.alector.com. We will post amendments to our Code of Business Conduct and Ethics or waivers of our Code of Business Conduct and Ethics for directors and executive officers on the same website.

Director Compensation

Directors who are also our employees receive no additional compensation for their service as directors. Dr. Rosenthal was our only employee director during 2020. See the section titled “Executive Compensation” for additional information about Dr. Rosenthal’s compensation.

The following table presents the total compensation each of our non-employee directors received during the year ended December 31, 2020. Other than as set forth in the table, we did not pay any compensation, make any equity awards or non-equity awards to or pay any other compensation to any of our non-employee directors in 2020.

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Non-Employee Director Compensation Policy

Our Board of Directors has adopted our Outside Director Compensation Policy. Our Outside Director Compensation Policy provides that all non-employee directors are entitled to receive the following cash compensation for their services:

Each non-employee director who serves as the chair of a committee receives only the additional annual fee as the chair of the committee and does not receive the additional annual fee as a member of the committee. All cash payments to non-employee directors are paid quarterly in arrears on a prorated basis.

In addition to the cash compensation structure described above, our Outside Director Compensation Policy provides the following equity incentive compensation program for non-employee directors. Each non-employee director who first joins us (other than a director who becomes a non-employee director as a result of terminating employment with us) automatically will be granted on the first trading date on or after his or her start date as a non-employee director a one-time, initial option award having a grant date fair value of approximately $550,000. Further, on the date of each of our annual stockholder meetings, each non-employee director who, as of such annual meeting date, has served on the board as a director for at least the preceding six months, automatically will be granted an annual option award having a grant date fair value of approximately $350,000.

Each initial option will vest as to 1/4th of the underlying shares on the one-year anniversary of the date the director’s service as a non-employee director started and as to 1/48th of the underlying shares each following month, subject to continued service through each relevant vesting date. Each annual option will vest as to 1/12th of the underlying shares each month after the award’s grant date and will vest in full on the earlier of the 12-month anniversary of the date of grant or on the date of our annual stockholder meetings following the date the annual option is granted, subject to continued service through each relevant vesting date. In the event of a change in control of our company, all equity awards granted to a non-employee director (including those granted pursuant to our Outside Director Compensation Policy) will fully vest and become immediately exercisable, subject to continued service through such date. Each initial option and annual option will have a term of 10 years and will have an exercise price per share equal to 100% of the fair market value of a share of our common stock on the date of grant.

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In any fiscal year, a non-employee director may be paid, issued, or granted cash compensation and equity awards with a total value of no greater than $750,000 (increased to $1,000,000 in the fiscal year of his or her initial service as an outside director) with the value of an equity award based on its grant date fair value for purposes of this limit (annual director limit). Equity awards or cash compensation granted to a non-employee director for his or her service as an employee or consultant (other than a non-employee director) does not count toward the annual director limit.

Our Outside Director Compensation Policy also provides for the reimbursement of our non-employee directors for reasonable, customary, and documented travel expenses to attend meetings of our Board of Directors.

Compensation for our non-employee directors is not limited to the equity awards and payments set forth in our Outside Director Compensation Policy. Our non-employee directors remain eligible to receive equity awards and cash or other compensation outside of the Outside Director Compensation Policy, as may be provided from time to time at the discretion of our Board of Directors.

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PROPOSAL NO. 1 ELECTION OF DIRECTORS

Our Board of Directors is currently comprised of eight members. In accordance with our amended and restated certificate of incorporation, our Board of Directors is divided into three staggered classes of directors. At the Annual Meeting, three Class III directors will be elected for a three-year term to succeed the same class whose term is then expiring.

Each director’s term continues until the election and qualification of his or her successor, or such director’s earlier death, resignation, or removal. Any increase or decrease 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 our directors. This classification of our Board of Directors may have the effect of delaying or preventing changes in control of our company.

Nominees

Our Nominating and Corporate Governance Committee has recommended, and our Board of Directors has approved, Tillman Gerngross, Ph.D., Richard Scheller, Ph.D., and Louis J. Lavigne, Jr. as nominees for election as Class III directors at the Annual Meeting. If elected, Messrs. Gerngross, Scheller, and Lavigne will serve as Class III directors until our 2024 annual meeting of stockholders and until their successors are duly elected and qualified. Each of the nominees is currently a director of our company. For information concerning the nominees, please see the section titled “Board of Directors and Corporate Governance.”

If you are a stockholder of record and you sign your proxy card or vote by telephone or over the Internet but do not give instructions with respect to the voting of directors, your shares will be voted “FOR” the election of Messrs. Gerngross, Scheller, and Lavigne. We expect that each of Messrs. Gerngross, Scheller, and Lavigne will accept such nomination; however, in the event that a director nominee is unable or declines to serve as a director at the time of the Annual Meeting, the proxies will be voted for any nominee designated by our Board of Directors to fill such vacancy. If you are a street name stockholder and you do not give voting instructions to your broker or nominee, your broker will leave your shares unvoted on this matter.

Vote Required

The election of directors requires a plurality vote of the shares of our common stock present (including by proxy) at the Annual Meeting and entitled to vote thereon to be approved. Broker non-votes will have no effect on this proposal.

THE BOARD OF DIRECTORS RECOMMENDS A VOTE “FOR”

EACH OF THE NOMINEES NAMED ABOVE.

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PROPOSAL NO. 2

RATIFICATION OF APPOINTMENT OF

INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

Our Audit Committee has appointed Ernst & Young LLP (“Ernst & Young”), an independent registered public accounting firm, to audit our consolidated financial statements for the fiscal year ending December 31, 2021. During the fiscal year ended December 31, 2020, Ernst & Young served as our independent registered public accounting firm. Ernst & Young LLP has served as our independent registered public accounting firm since 2017.

Notwithstanding the appointment of Ernst & Young and even if our stockholders ratify the appointment, our Audit Committee, in its discretion, may appoint another independent registered public accounting firm at any time during the fiscal year if our Audit Committee believes that such a change would be in the best interests of our company and our stockholders. At the Annual Meeting, our stockholders are being asked to ratify the appointment of Ernst & Young as our independent registered public accounting firm for the fiscal year ending December 31, 2021. Our Audit Committee is submitting the appointment of Ernst & Young to our stockholders because we value our stockholders’ views on our independent registered public accounting firm and as a matter of good corporate governance. Representatives of Ernst & Young will be present at the Annual Meeting, and they will have an opportunity to make a statement and will be available to respond to appropriate questions from our stockholders.

If our stockholders do not ratify the appointment of Ernst & Young, our Board of Directors may reconsider the appointment.

Fees Paid to the Independent Registered Public Accounting Firm

The following table presents fees for professional audit services and other services rendered to our company by Ernst & Young for the fiscal years ended December 31, 2020 and 2019.

Auditor Independence

In the fiscal year ended December 31, 2020, there were no other professional services provided by Ernst & Young, other than those listed above, that would have required our Audit Committee to consider their compatibility with maintaining the independence of Ernst & Young.

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

Our Audit Committee has established a policy governing our use of the services of our independent registered public accounting firm. Under this policy, our Audit Committee is required to pre-approve all audit and permissible non-audit services, other than de minimis non-audit services, performed by our independent registered public accounting firm in order to ensure that the provision of such services does not impair the public accountants’ independence. All fees paid to Ernst & Young for the fiscal years ended December 31, 2020 and 2019 were pre-approved by our Audit Committee.

Vote Required

The ratification of the appointment of Ernst & Young as our independent registered public accounting firm requires the affirmative vote of a majority of the shares of our common stock present (including by proxy) at the Annual Meeting and entitled to vote thereon. Abstentions will have the effect of a vote “AGAINST” the proposal and broker non-votes will have no effect.

THE BOARD OF DIRECTORS RECOMMENDS A VOTE “FOR”

THE RATIFICATION OF THE APPOINTMENT OF ERNST & YOUNG LLP.

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PROPOSAL NO. 3

ADVISORY VOTE ON NAMED EXECUTIVE OFFICER COMPENSATION

This stockholder advisory vote, commonly known as “say-on-pay,” is required pursuant to Section 14A of the Exchange Act and gives our stockholders the opportunity to approve or not approve, on a non-binding advisory basis, the compensation paid to our Chief Executive Officer and the other officers named in the Summary Compensation Table (“named executive officers”) as disclosed in this proxy statement.

The Board recommends a vote “FOR” the following resolution:

“RESOLVED, that the stockholders of Alector, Inc. approve, on an advisory basis, the compensation of the named executive officers, as disclosed in the proxy statement, including the Compensation Discussion and Analysis, the compensation tables and any related narrative discussion.”

We became public in February 2019 and since that time we have made significant changes to our executive compensation program to reflect our transition from a private to public company. This is the first time we have included an advisory “say-on-pay” vote at the annual meeting of the stockholders, as our Board of Directors believes that stockholders will now be able to provide more meaningful feedback regarding the effectiveness of our executive compensation program and its relation to business outcomes of our company. We intend to submit the executive compensation of our named executive officers to an advisory vote at our annual meeting of stockholders consistent with the advisory vote of the stockholders at the Annual Meeting.

The Compensation Discussion and Analysis, beginning on page 27, describes our executive compensation programs and the compensation decisions made by our compensation committee and Board of Directors for the fiscal year ended December 31, 2020 with respect to the named executive officers. As described in detail in the Compensation Discussion and Analysis and highlighted in the section captioned “Executive Summary,” our compensation committee believes that the most effective compensation program is designed to provide a substantial portion of executive compensation in the form of variable, at-risk pay which is earned based on performance. Our compensation committee thoughtfully employs the primary compensation elements of base salary, annual cash incentives, and long-term equity awards, to achieve these objectives.

Our Board of Directors is asking you to support this proposal. Because your vote is advisory, it will not be binding. However, the Board of Directors and the compensation committee will review the voting results in their entirety and take them into consideration when making future decisions regarding named executive officer compensation.

OUR BOARD OF DIRECTORS RECOMMENDS A VOTE “FOR”

APPROVAL OF PROPOSAL NO. 3

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PROPOSAL NO. 4

ADVISORY VOTE ON THE FREQUENCY OF FUTURE ADVISORY VOTES ON

NAMED EXECUTIVE OFFICER COMPENSATION

In accordance with The Dodd-Frank Wall Street Reform and Consumer Protection Act of 2010 and Section 14A of the Exchange Act, we must provide our stockholders with the opportunity to make a non-binding, advisory vote on the frequency of future advisory votes on named executive officer compensation (the “Say-On-Frequency Vote”). The non-binding, advisory Say-On-Frequency Vote must be submitted to our stockholders at least once every six years.

We are asking stockholders to indicate whether they prefer to cast future advisory votes on named executive officer compensation “EVERY YEAR,” “EVERY TWO YEARS” or “EVERY THREE YEARS.” Stockholders may also abstain from voting on this proposal. The frequency that receives the greatest number of votes cast by stockholders will be considered the advisory vote of our stockholders.

Our board of directors values the opinions of our stockholders and will consider the result of the Say-On-Frequency Vote in determining the frequency with which we will hold future advisory votes on named executive officer compensation. However, the Say-On-Pay Frequency Vote is not binding. Our board of directors may determine that it is in the best interests of the company and our stockholders to hold an advisory vote on named executive officer compensation more or less frequently than the frequency that is selected by our stockholders.

After careful consideration, our board of directors recommends that future non-binding advisory votes on the compensation of our named executive officers be held every year.

OUR BOARD OF DIRECTORS RECOMMENDS A VOTE FOR “EVERY YEAR”

FOR THE SAY-ON-FREQUENCY VOTE.

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AUDIT COMMITTEE REPORT

The information contained in the following Audit Committee Report shall not be deemed to be soliciting material or to be filed with the Securities and Exchange Commission, nor shall such information be incorporated by reference into any future filing under the Securities Act of 1933, as amended, or the Securities Exchange Act of 1934, as amended, except to the extent that Alector, Inc. (the “Company”) specifically incorporates it by reference in such filing.

The audit committee serves as the representative of our Board of Directors with respect to its oversight of:

The audit committee reviewed and discussed the audited financial statements for the fiscal year ended December 31, 2020 with management and Ernst & Young LLP, the Company’s independent registered public accounting firm. The audit committee has discussed with Ernst & Young LLP the matters required to be discussed by the applicable requirements of the Public Company Accounting Oversight Board (“PCAOB”) and the SEC.

The audit committee is composed of three non-employee directors. Our Board of Directors has determined that each member of the audit committee is independent and that Messrs. Lavigne and Wehner each qualify as an “audit committee financial expert” under the SEC rules.

The audit committee has received and reviewed the written disclosures and the letter from Ernst & Young LLP required by the applicable requirements of the PCAOB regarding Ernst & Young LLP’s communications with the audit committee concerning independence and has discussed with Ernst & Young LLP its independence. In addition, the audit committee has discussed with Ernst & Young LLP its independence from management and the Company, including matters in the letter from Ernst & Young LLP required by PCAOB Rule 3526, Communication with Audit Committees Concerning Independence, and considered the compatibility of any non-audit services with Ernst & Young LLP’s independence.

Based on the review and discussions referred to above, the audit committee recommended to our Board of Directors that the Company’s audited consolidated financial statements be included in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2020 for filing with the Securities and Exchange Commission. The audit committee also has selected Ernst & Young LLP as the independent registered public accounting firm for fiscal year 2021. Our Board of Directors recommends that stockholders ratify this selection at the Annual Meeting.

Respectfully submitted by the members of the audit committee of the Board of Directors:

Louis J. Lavigne, Jr. (Chairperson)

Terry McGuire

David Wehner

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EXECUTIVE OFFICERS

The following table identifies certain information about our executive officers as of March 1, 2021. Our executive officers are appointed by, and serve at the discretion of, our Board of Directors. There are no family relationships among any of our directors or executive officers.

Arnon Rosenthal. For a biography of Dr. Rosenthal, please see the section titled “Board of Directors and Corporate Governance.”

Shehnaaz Suliman, M.D., President and Chief Operating Officer. Dr. Suliman has served as our President and Chief Operating Officer since December 2019. Dr. Suliman previously served as Senior Vice President, Corporate Development and Strategy of Theravance Biopharma, Inc., a position she held from July 2017 to March 2019. Prior to her position at Theravance, Dr. Suliman worked for Genentech, Inc. as Group Leader and Project Team Leader in the R&D Portfolio Management and Operations Group from September 2010 to May 2015 and then as Vice President and Global Therapeutic Head, Roche Partnering from June 2015 to July 2017. Prior to Genentech, Dr. Suliman held various management roles of increasing responsibility at Gilead Sciences, Inc. between January 2005 and September 2010. Prior to Gilead, Dr. Suliman was an investment banker with Lehman Brothers and Petkevich & Partners, advising public and private companies on buy- and sell-side transactions. She is a member of the board of directors of Ultragenyx Pharmaceutical Inc., a pharmaceutical company, and 10x Genomics, Inc., a life science technology company. Dr. Suliman received her M.D. at the University of Cape Town Medical School, South Africa, and holds an M.B.A., with distinction, and M.Phil. in Development Studies degrees from Oxford University, where she was a Rhodes Scholar.

Robert Paul, M.D., Ph.D., Chief Medical Officer. Dr. Paul has served as our Chief Medical Officer since October 2016. Dr. Paul joined Alector from Genentech, Inc., where he held various roles of increasing responsibility between 2009 and 2016, including as Assistant Group Medical Director and TA Head Neuroscience Early Clinical Development gRED from October 2015 to October 2016, as Senior Medical Director from October 2013 to September 2015, as Medical Director from September 2011 to October 2013, and as Associate Medical Director from January 2009 to September 2011. From May 2002 to December 2008, Dr. Paul served as a Neurologist at the University of Munich. Dr. Paul is a board certified neurologist in Germany. He received a M.D. and a Ph.D. from Ludwig-Maximilians Universität München.

Robert King, Ph.D., Chief Development Officer. Dr. King has served as our Chief Development Officer since January 2017. Dr. King joined Alector from SciClone Pharmaceuticals, Inc. (acquired by a consortium led by GL Capital Partners, LLC), a biotechnology company, where he served as Senior Vice President of Product Development and Supply Chain from June 2011 to January 2017. Prior to SciClone Pharmaceuticals, Dr. King served as VP of Product Development and Manufacturing at Bayhill Therapeutics, Inc., a biotechnology company from 2006 to 2011. Dr. King served as VP Product Development and Manufacturing at Rinat Neuroscience Corp. (acquired by Pfizer), a biotechnology company, from 2003 to 2006. Dr. King served in positions of increasing responsibility at COR Therapeutics, Inc. (acquired by Millennium Pharmaceuticals, Inc. in 2002) from 1993 to 2003. From 1991 to 1993, Dr. King served as a Scientist in the Purification and Pharmaceutical Sciences groups at California Biotechnology/Scios. From 1988 to 1991, Dr. King was a Scientist at Molecular Devices Corporation. Dr. King received a Ph.D. in Chemical Engineering from the University of California, Berkeley, and a B.S. in Chemical Engineering from the University of Washington.

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Calvin Yu, Vice President, Finance. Mr. Yu has led our Finance team since June 2017. Mr. Yu joined Alector from Stemcentrx, Inc. (acquired by AbbVie), a biotechnology company, where he served as Corporate Controller from February 2016 to June 2017. Prior to Stemcentrx, Mr. Yu held several senior level finance roles at publicly traded biotechnology companies, including Senior Director of Finance and SEC Reporting at Adverum Biotechnologies, Inc. from September 2014 to February 2016, and Controller at Five Prime Therapeutics, Inc. from March 2010 to September 2014. Mr. Yu received his B.S. in Accounting from San Francisco State University, College of Business.

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EXECUTIVE COMPENSATION

Compensation Discussion and Analysis

This Compensation Discussion and Analysis (“CD&A”) describes the principles underlying the material components of our executive compensation program for our executive officers, including the named executive officers in the “Summary Compensation Table.” We also provide an overview of the overall objectives of the program and the factors relevant to an analysis of these policies and decisions and how we use our executive compensation program to drive our performance.

Named Executive Officers

Our named executive officers for the year ended December 31, 2020 are:

Executive Summary

Company Background and 2020 Business Highlights

Our mission is to develop therapies that empower the immune system to cure neurodegeneration. We are a clinical stage biopharmaceutical company pioneering immuno-neurology, a novel therapeutic approach for the treatment of neurodegeneration. Immuno-neurology targets immune dysfunction as a root cause of multiple pathologies that are drivers of degenerative brain disorders. We are developing therapies designed to simultaneously counteract these pathologies by restoring healthy immune function to the brain.

Our executive compensation program seeks to incentivize and reward strong corporate performance. Highlights of our 2020 corporate performance and executive compensation program are set forth below.

Clinical and Regulatory

Corporate Financings

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In addition, we progressed multiple early-stage programs, including our AL009 development program, and made significant progress on other internal corporate goals.

Overview of Executive Compensation Program

Our executive compensation program is designed to be competitive and appropriately balance our goals of attracting, engaging and retaining our executive officers and driving company performance. To align our executive officers’ interests with those of our stockholders and to motivate and reward individual initiative and effort, a substantial portion of each executive officer’s total target annual direct compensation opportunity is “at-risk,” meaning the amounts paid to each executive officer will vary based on our Company performance and their contributions to that performance.

Consistent with our philosophy of aligning executive pay with the short- and long-term performance of the Company, and to align the interests of management and stockholders, the Company’s compensation programs are designed to provide the majority of executive compensation in the form of variable, at-risk pay. Our Compensation Committee thoughtfully employs the primary compensation elements of base salary, short-term annual cash incentives, and long-term equity awards, to achieve these objectives.

In 2020, target pay packages were as follows:

The percentages above were calculated using base salary, target annual cash incentive compensation, and the grant date fair value of stock options. Similar to our industry based peers, we rely on stock option grants for our NEOs’ equity-based compensation because they do not provide realizable value to the holder unless shareholders also benefit from a stock price increase.

Key 2020 Compensation Decisions

Aligned with our results and performance in 2020 as outlined above we took several actions related to our pay program.

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Executive Compensation Governance

With guidance from an independent compensation consultant, we maintain sound compensation and governance standards, and we adopt best practices in establishing and administering policies in support of these standards. The Compensation Committee evaluates our executive compensation program regularly to ensure that it supports our short-term and long-term goals to compete for executive talent as well as protect our stockholders’ interests.

Our pay-for-performance philosophy and compensation governance practices provide an appropriate framework to our executives to achieve our strategic goals without encouraging them to take excessive risks in their business decisions. Some of our practices include:

Stockholder Engagement

The Company is committed to engagement with stockholders. We review any feedback we receive from our stockholders about our executive compensation program to ensure that we understand key matters of interest to them, and to enable us to take that feedback into consideration for our compensation decisions.

Compensation Philosophy

The goals of our executive compensation program are to attract, engage, and retain executive offers who share our vision and are deeply connected to our mission. Our overall compensation philosophy is market-based and enables our executive officers to share in Alector’s long-term success. We strive to incentivize these executive officers to achieve our short-term and long-term business objectives in order to increase long-term value and increase stockholder value. Our program combines competitive cash and equity award opportunities in the forms and proportions that we believe will motivate our executive officers to increase stockholder value over the long-term. We routinely review our policies and program design.

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Our executive compensation program delivers excellent rewards in line with individual and company performance using the following specific compensation methods:

“Say-on-Pay” Voting

In prior years, we were an “emerging growth company” as defined in the Jumpstart Our Business Startups Act of 2012, as amended. Therefore, we were not required to hold a non-binding, advisory vote on the compensation of our named executive officers (a “Say-on-Pay” vote). At this annual general meeting (“AGM”), we will hold our first Say-on-Pay vote. Our Board of Directors and Compensation Committee will consider the result of the Say-on-Pay vote, and the related “Say-on-Frequency” vote, as well as feedback received throughout the year, when making compensation decisions for our executive officers in the future because we value the opinions of our shareholders.

Compensation Determination Process

Role of Compensation Committee and Board of Directors

Our Compensation Committee is responsible for overseeing the total compensation of our executive officers. In this capacity, our Compensation Committee designs, implements, reviews, and approves all compensation for our Chief Executive Officer (“CEO”) and our other executive officers. The Compensation Committee formally met seven times during fiscal year 2020 to review and discuss matters related to compensation of our employees and executive officers. Some of these meetings were held with members of management in attendance and some were held in closed session. Most of the meetings also included representatives from our compensation consultant (as described below). Typically, the Compensation Committee reports to the Board of Directors on its discussions and on occasion seeks input from the Board of Directors regarding, the decisions to be made and other actions to be taken with regard to our executive officers’ compensation. Our Compensation Committee’s recommendations regarding executive compensation are based on the Compensation Committee’s assessment of the performance of the Company and each individual executive officer, as well as other factors, such as prevailing industry trends and the competitive market for executive talent. The Compensation Committee makes the final decisions regarding executive compensation.

Role of Management

Our CEO, President and Chief Operating Officer (“COO”), and our VP, People typically make recommendations to our Compensation Committee, attend certain Compensation Committee meetings and are involved in the process for determining our executive officers’ compensation, provided that neither our CEO or COO makes recommendations as to their own compensation or participates in Compensation Committee discussion of their own compensation. Our Compensation Committee considers management’s recommendations but is not required to follow any recommendations and may adjust compensation up or down as it determines in its discretion. Our Compensation Committee reviews the recommendations and other data and makes as to each executive officer’s total compensation, as well as each individual pay component. At certain meetings in 2020, the Compensation Committee met in executive sessions and the Company’s CEO, COO and VP, People were not present when it deliberated and voted on the compensation of the executive officers.

Role of Independent Compensation Consultant

Our Compensation Committee is authorized to retain the services of one or more executive compensation advisors, as it sees fit, in connection with the establishment of our compensation programs and related policies.

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In 2020, our Compensation Committee retained Radford, part of the Rewards Solutions practice at Aon plc, (“Radford”) as independent compensation consultant., to provide it with information, recommendations, and other advice relating to executive compensation on an ongoing basis. Accordingly, Radford serves at the discretion of our Compensation Committee. Our Compensation Committee engaged Radford to assist in developing an appropriate group of peer companies to help us determine the appropriate level of overall compensation for our executive officers, as well as assess each separate element of compensation, with a goal of ensuring that the compensation we offer to our executive officers is competitive and fair.

Use of Peer Group

The Compensation Committee approves a peer group of companies as a reference group to provide a broad perspective on competitive pay levels and practices. The peers are reviewed on an annual basis in light of the fast-moving changes at Alector and our industry. We undertake this review with the assistance and recommendations of Radford, the Compensation Committee’s compensation consultant. Radford provides competitive market analysis of the base salary, annual cash incentive awards, and long-term incentive compensation of our executive officers compared against our compensation peer group and to review other market practices and trends.

Alector undertakes two compensation cycles per year, with cash compensation decisions (bonus payout and merit increase) the focus of the Q1 compensation cycle, and equity decisions the focus of the Q3 compensation cycle. This structure enables a tighter pay-for-performance link and two opportunities for a rewards conversation each year.

2019 Peer Group

In August 2019, the Compensation Committee approved a peer group for use in making Q1 2020 base salary and annual target bonus decisions. The Compensation Committee used the following criteria in determining the appropriate peers:

Based on these criteria and considerations, our peer group for 2019, referred to as our 2019 peer group, as approved by our Compensation Committee, consisted of the following 25 companies:

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2020 Peer Group

In August 2020, the Compensation Committee approved the peer group for use in making Q3 2020 equity decisions (and for future use in making Q1 2021 base salary and annual target bonus decisions). Due to changes in the Company’s profile, the Compensation Committee made updates to the peer selection criteria. The Compensation Committee used the following updated criteria in determining the appropriate peers:

Based on these criteria and considerations, five companies were added to the 2020 peer group, as noted below, and 15 companies were removed from the 2019 peer group as they no longer met the criteria listed above. Our peer group for 2020, as approved by our Compensation Committee, consisted of the following 15 companies:

In setting compensation for our executive officers, including our named executive officers, the Compensation Committee uses competitive compensation data from an annual total compensation study of selected peer companies and relevant survey sources to inform its decisions about overall compensation opportunities and specific compensation elements. However, the Compensation Committee uses our compensation peer group as one data point when setting executive pay packages. The overall compensation philosophy focuses at or near a target percentile, particularly in respect to target cash compensation and equity grants. In addition, our compensation decisions are based on the consideration of many factors, including, but not limited to, individual and company performance, market data, internal equity, experience, and strategic needs. As a result of evaluating compensation based on the criteria described above, total target compensation for our named executive officers may in certain circumstances be above or below the target levels of the peer group.

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Pay Components

The Company’s executive compensation program consists of three primary elements: base salaries, annual cash incentives, and long-term equity awards:

Alector is committed to a strong performance orientation in our compensation program and effective corporate governance practices for a company at our development stage and industry. Some of our best practices in governance that we observe include:

Base Salary

Base salary is the only fixed component of our executive officers’ total cash compensation and provides competitive pay to attract and retain our executives. Annual salary decisions are made in recognition of competitive data as well as the skills and experience that each individual brings to the Company and the performance contributions each makes.

Base salary changes in 2020 varied by executive due either to merit increases or market adjustments. Other factors were considered such as tenure, experience, and the role of the individual.

The 2020 base salaries for our named executive officers were as follows and were effective on March 1, 2020 except as noted below:

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2020 Executive Incentive Compensation Plan

The Executive Incentive Compensation Plan (the “Bonus Plan”) is designed to provide a financial incentive to reward executives for the achievement of a series of program specific, pipeline, and functional corporate goals. Payments under the plan are ultimately based on achievement of these pre-established corporate goals. Actual performance against targets, as measured by these pre-established corporate goals, funds the incentive payouts. The bonus pool can be funded between 0% to a maximum of 150% of target funding levels. The total bonus payout cannot exceed the total amount of funding in the pool. Annual target bonuses are set based on factors such as the executive’s past contributions, tenure, experience, and role and the annual target bonuses provided by companies in our compensation peer group to their similarly situated executives. Bonuses are typically paid in the quarter following the end of the performance period.

For 2020, the Compensation Committee approved an increase to Dr. Rosenthal’s annual target bonus (from 50% in 2019 to 55% in 2020) to make his annual bonus opportunity more competitive with the market. The annual target bonus target for each of our other NEOs (except Dr. Suliman), as a percentage of the NEO’s base salary, remained unchanged from 2019. Dr. Suliman’s annual bonus opportunity was determined through arm’s-length negotiation in connection with her hire.

Bonuses for all employees, including our named executive officers, for the fiscal year ended December 31, 2020 were allocated from a bonus pool funded based on performance against a number of high-impact, cross-functional goals. The project goals related to specific programs, trials, and corporate progress. The cross-functional goals included goals related to business development, positioning for future growth, and development and other functional goals. The combination of the project and cross-functional goals was intended to drive both specific technical achievement and continue to build the foundation for future company growth and advancements.

For 2020, the Company established four key corporate objectives: (i) advance research pipeline, (ii) advance clinical pipeline, (iii) build a sustainable public company, and (iv) cultivate employee experience that drives business results, which are viewed as critical drivers of our long-term success and ability to generate sustained growth in shareholder value. Our corporate goals are intended to drive these key objectives, by establishing specific, measurable criteria that could be used to evaluate the performance of our Executive team and the Company in general. We believe that if these goals are achieved, it will have a direct impact on creating value for our stockholders.

Each goal is measured individually, and the percent of goals achieved determines the 2020 bonus payout, subject to the Compensation Committee’s discretion to alter bonus funding and payouts. 2020 performance bonuses were earned based upon achievement of such performance goals, as follows:

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In January 2021, the Compensation Committee reviewed the progress against the applicable 2020 goals. Based on the Company’s achievement of 80.42% of these goals, the Compensation Committee funded the Company’s bonus pool at 80.42% of target levels. The resulting bonuses to named executive officers were as follows:

Annual bonus target percentages for each of our named executive officers remained flat throughout 2020, which was deemed appropriate according to peer and market data. The bonuses paid to each of our named executive officers in 2020 under our Bonus Plan are set forth in the “Non-Equity Incentive Plan Compensation” column of the Summary Compensation Table below.

Equity Long-Term Incentive Compensation—Refresh Awards

We believe long-term incentive compensation is an effective means for focusing our executive officers, including the named executive officers, on driving strong performance and increased stockholder value over a multi-year period, provides a meaningful reward for long-term value creation, and motivates them to remain employed with us.

This approach aligns the contributions of our executive officers with the long-term interests of our stockholders and allows them to participate in any future appreciation in our common stock.

We determine long-term incentive compensation for our executive officers as part of our biannual compensation review (with cash compensation reviewed in Q1 and equity compensation reviewed in Q3) taking into account competitive market analysis, the recommendations of our CEO (except regarding his own long-term incentive compensation), the outstanding equity holdings of each executive officer, the projected impact of the proposed awards on our earnings, and our Company performance in 2020.

In 2020, the long-term incentive equity compensation awarded to our named executive officers was granted in the form of stock options vesting over a four-year time-based schedule. This approach is consistent with market practice among our peers and industry comparables, and reinforces a strong pay-for-performance culture as each stock option award only has value for the recipient if the value of our common stock appreciates from the grant date. Each stock option award was granted on the following material terms:

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Severance and Change in Control Protections

In November 2018, we adopted a Change in Control and Severance Agreement (the “Severance Agreement”) in which our named executive officers participate. The Severance Agreement provides participants with severance in the event of certain qualifying terminations, including following a change in control of our Company, and certain change in control benefits. We believe that these protections are necessary to provide our valuable executives with incentives to forego other employment opportunities and remain employed with us and to maintain continued focus and dedication to their responsibilities to maximize stockholder value, including if there is a potential transaction that could involve a change in control. In addition, these protections are available only if a named executive officer executes and does not revoke a general release of claims in favor of us. The terms and levels of benefits provided to our named executive officers under the Severance Agreement were determined by our Compensation Committee, with input from our management team, and approved by our Board of Directors following a review of analysis prepared by Radford of relevant market data for other companies with whom we compete for executive talent.

For a summary of the material terms of the benefits provided to our named executive officers under the Severance Agreement and an estimate of the payments and benefits that may be received by our named executive officers under the Severance Agreements, see “Potential Payments on Termination or Change in Control” below.

Other Compensation

Retirement, Welfare, and Health Benefits

We maintain a tax-qualified retirement plan that provides eligible employees with an opportunity to save for retirement on a tax advantaged basis. All participants’ interests in their deferrals are 100% vested when contributed. Pre-tax contributions are allocated to each participant’s individual account and are then invested in selected investment alternatives according to the participants’ directions. The 401(k) plan is intended to qualify under Sections 401(a) and 501(a) of the Internal Revenue Code (the “Code”). As a tax-qualified retirement plan, contributions to the 401(k) plan and earnings on those contributions are not taxable to the employees until distributed from the 401(k) plan. Subject to limits under the Code, we match an amount equal to 50% of the first 6% of the eligible employee’s contributions with a maximum annual employer contribution of $5,000 per employee. Our executive officers are eligible to participate in our 401(k) plan.

Our health and welfare benefits include medical, dental and vision benefits, long-term disability insurance, basic life insurance coverage, health savings accounts, and accidental death and dismemberment insurance. Our named executive officers also are eligible to participate in our Employee Stock Purchase Plan on the same terms as our other eligible employees. We design our employee benefits programs to be affordable and competitive in relation to the market, and compliant with applicable laws and practices. We adjust our employee benefits programs as needed based upon changes in applicable laws and market practices.

Perquisites and Other Personal Benefits

We do not provide perquisites or other personal benefits to our executive officers, including the named executive officers except in situations where we believe it is appropriate to assist an individual in the performance of his or her duties, to make our executive officers more efficient and effective, and for recruitment and retention purposes.

In the future, we may provide perquisites or other personal benefits in limited circumstances. All future practices with respect to perquisites or other personal benefits for executive officers will be approved and subject to periodic review by the Compensation Committee.

Employment Agreements

We have entered into employment letters with each of our named executive officers. Each of these agreements was approved by our Board of Directors or our Compensation Committee.

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In filling each of our executive positions, our Board of Directors and the Compensation Committee recognized the need to develop competitive compensation packages to attract qualified candidates in a dynamic labor market. Our Board of Directors and our Compensation Committee were sensitive to the need to integrate new executive officers into the executive compensation structure that we were seeking to develop, balancing both competitive and internal equity considerations.

For information on the specific terms and conditions of the employment letters of the named executive officers, see the discussion of “Executive Employee Arrangements” below.

Additional Policies and Practices

Hedging and Pledging Prohibitions

As part of our Insider Trading Policy, our employees (including our executive officers and the non-employee members of our Board of Directors) are prohibited from trading in publicly-traded options, such as puts and calls, and other derivative securities with respect to our securities. This includes any hedging or similar transaction designed to decrease the risks associated with holding shares of our common stock.

In addition, our employees (including our executive officers and the non-employee members of our Board of Directors) are prohibited from holding our common stock in a margin account or pledging our securities as collateral for a loan.

Tax and Accounting Considerations

Deductibility of Executive Compensation

Generally, Section 162(m) of the Code (“Section 162(m)”) disallows a U.S. federal income tax deduction for public corporations of remuneration in excess of $1 million paid in any fiscal year to certain specified executive officers. The Company generally expects that all remuneration in excess of $1 million paid to a specified executive will not be deductible by us as a corporate entity unless it qualifies for the transition relief applicable to certain newly public companies. To maintain flexibility to compensate our executive officers in a manner designed to promote our short-term and long-term corporate goals, the Compensation Committee has not adopted a policy that all compensation must be deductible. The Compensation Committee believes that our shareholders’ interests are best served if its discretion and flexibility in awarding compensation is not restricted in order to allow such compensation to be consistent with the goals of our executive compensation program, even though some compensation awards may result in non-deductible compensation expense.

Accounting for Stock-Based Compensation

We follow the Financial Accounting Standard Board’s Accounting Standards Codification Topic 718 (“FASB ASC Topic 718”) for our stock-based compensation awards. FASB ASC Topic 718 requires us to measure the compensation expense for all share-based payment awards made to our employees and members of our Board of Directors, including options to purchase shares of our common stock and other stock awards, based on the grant date “fair value” of these awards. This calculation is performed for accounting purposes and reported in the executive compensation tables required by the federal securities laws, even though the recipient of the awards may realize no value from their awards.

Taxation of Parachute Payments and Deferred Compensation

We do not provide, and have no obligation to provide, any of our named executive officers with a “gross-up” or other reimbursement payment for any tax liability he or she might owe because of the application of Sections 280G, 4999, or 409A of the Code. If any of the payments or benefits provided for under the Severance Agreement or otherwise payable to a named executive officer would constitute “parachute payments” within the

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meaning of Section 280G of the Code and could be subject to the related excise tax, he or she would receive either full payment of such payments and benefits or such lesser amount that would cause no portion of the payments and benefits being subject to the excise tax, whichever results in the greater after-tax benefits to our named executive officer.

Compensation Committee Interlocks and Insider Participation

During 2020, our Compensation Committee consisted of David Wehner, Louis J. Lavigne, Jr., and Paula Hammond, Ph.D. None of the members of our Compensation Committee is or has been an officer or employee of us. None of our executive officers currently serves, or in the past year has served, as a member of the board or compensation committee (or other board committee performing equivalent functions or, in the absence of any such committee, the entire board) of any entity that has one or more executive officers serving on our Board of Directors or Compensation Committee.

Compensation Committee Report

The Compensation Committee has reviewed and discussed with management the CD&A provided above. Based on its review and discussions, the Compensation Committee recommended to the Board of Directors that the CD&A be included in this proxy statement and our Annual Report on Form 10-K for our fiscal year ended December 31, 2020.

Compensation Committee

David Wehner (Chairman)

Louis J. Lavigne, Jr.

Paula Hammond, Ph.D.

Summary Compensation Table for Fiscal Years 2020, 2019, and 2018

The following table provides information regarding the compensation awarded to, or earned by, our named executive officers during 2020, 2019, and 2018.

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Grants of Plan-Based Awards

The following table provides information regarding grants of plan-based awards to each of our named executive officers during the fiscal year ended December 31, 2020.

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Outstanding Equity Awards at Fiscal Year-End

The following table presents certain information concerning equity awards held by our named executive officers, as of December 31, 2020.

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Option Exercises and Stock Awards Vesting During Fiscal 2020

The following table shows certain information concerning option exercises and value realized upon the exercise of stock options by our named executive officers during the fiscal year ended December 31, 2020.

Executive Employment Arrangements

Dr. Arnon Rosenthal

We entered into a confirmatory employment letter with Arnon Rosenthal, our Co-founder and Chief Executive Officer. The confirmatory employment letter has no specific term and provides that Dr. Rosenthal is an at-will employee.

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Dr. Shehnaaz Suliman

We entered into an employment offer letter with Shehnaaz Suliman, our President and Chief Operating Officer. The employment offer letter has no specific term and provides that Dr. Suliman is an at-will employee.

Dr. Robert King

We entered into a confirmatory employment letter with Robert King, our Chief Development Officer. The confirmatory employment letter has no specific term and provides that Dr. King is an at-will employee.

Dr. Robert Paul

We entered into a confirmatory employment letter with Robert Paul, our Chief Medical Officer. The confirmatory employment letter has specific term and provides that Dr. Paul is an at-will employee.

Calvin Yu

We entered into a confirmatory employment letter with Calvin Yu, our Vice President, Finance. The confirmatory employment letter has no specific term and provides that Mr. Yu is an at-will employee.

Potential Payments on Termination or Change in Control

We entered into a change in control and severance agreement with each of our named executive officers, which provides for certain severance and change in control benefits as described below. Each change in control and severance agreement superseded any prior agreement or arrangement the named executive officer may have had with us that provided for severance and/or change in control payments or benefits.

If a named executive officer’s employment is terminated outside the period beginning on the date of a change in control and ending 12 months following that change in control (the “Change in Control Period”) either (1) by the Company or any of its subsidiaries (the “Company Group”) without “cause” (excluding by reason of death or disability) or (2) by the named executive officer for “good reason” (as such terms are defined in the named executive officer’s change in control and severance agreement), the named executive officer will receive the following benefits if he or she timely signs and does not revoke a release of claims in our favor:

If, within the Change in Control Period, the named executive officer’s employment is terminated either (1) by the Company (or any of its subsidiaries) without cause (excluding by reason of death or disability) or (2) by the named executive officer for good reason, the named executive officer will receive the following benefits if the named executive officer timely signs and does not revoke a release of claims in our favor:

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If any of the amounts provided for under these change in control and severance agreements or otherwise payable to our named executive officers would constitute “parachute payments” within the meaning of Section 280G of the Code and could be subject to the related excise tax, the named executive officer would be entitled to receive either full payment of benefits under his change in control or severance agreement or such lesser amount which would result in no portion of the benefits being subject to the excise tax, whichever results in the greater amount of after-tax benefits to the named executive officer. The change in control and severance agreements do not require us to provide any tax gross-up payments.

Under each named executive officer’s change in control and severance agreement, the following definitions are used:

“Cause” means:

Any termination for “Cause” will require the approval of our Board of Directors, and the named executive officer will be given the opportunity to appear in person before the entire Board of Directors in order to explain the named executive officer’s position on the allegations or claims that constitute “Cause.”

“Good Reason” means that the named executive officer resigns from a Company Group member if one of the following events occurs without his consent:

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For “Good Reason” to be established, the named executive officer must provide written notice to our CEO (or our Board of Directors in the case of Dr. Rosenthal) and the applicable Company Group member within 90 days immediately following such alleged events, the applicable Company Group member must fail to materially remedy such event within 30 days after receipt of such notice, and the named executive officer’s resignation must be effective not later than 90 days from the occurrence of the alleged triggering event, and must not be effective until after the expiration of the notice and cure periods described above.

The following table provides information concerning the estimated payments and benefits that would be provided in the circumstances described below, assuming that the triggering event took place on December 31, 2020, the last day of our fiscal year.

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Equity Compensation Plan Information

The following table provides information as of December 31, 2020 with respect to shares of our common stock that may be issued under our existing equity compensation plans.

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Risk Analysis of our Compensation Plans

Our Compensation Committee reviews and discusses with management the risks arising from our executive compensation philosophy and practices applicable to all employees to determine whether they encourage excessive risk-taking and to evaluate compensation policies and practices that could mitigate such risks. In addition, our Compensation Committee engaged Radford in 2019 and 2020 to independently review our executive compensation program. Based on those reviews, the Compensation Committee structures our executive compensation program to encourage our named executive officers to focus on both short-term and long-term success. We do not believe that our executive compensation program creates risks that are reasonably likely to have a material adverse effect on us.

Conclusion

It is the opinion of the Compensation Committee that the compensation policies and elements described above provide the necessary incentives to properly align our executive officers’ performance with the interests of our stockholders while maintaining equitable and competitive executive compensation practices that enable us to attract, engage and retain the highest caliber of executive officers.

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SECURITY OWNERSHIP OF CERTAIN BENEFICIAL OWNERS AND MANAGEMENT

The following table sets forth certain information with respect to the beneficial ownership of our common stock as of March 1, 2021 for:

We have determined beneficial ownership in accordance with the rules of the SEC and the information is not necessarily indicative of beneficial ownership for any other purpose. Unless otherwise indicated below, to our knowledge, the persons and entities named in the table have sole voting and sole investment power with respect to all shares that they beneficially owned, subject to community property laws where applicable.

We have based our calculation of the percentage of beneficial ownership on 79,589,651 shares of our common stock outstanding as of March 1, 2021. We have deemed shares of our common stock subject to stock options that are currently exercisable or exercisable within 60 days of March 1, 2021, to be outstanding and to be beneficially owned by the person holding the stock option for the purpose of computing the percentage ownership of that person. We did not deem these shares outstanding, however, for the purpose of computing the percentage ownership of any other person.

Unless otherwise indicated, the address of each beneficial owner listed in the table below is c/o Alector, Inc., 131 Oyster Point Boulevard, Suite 600, South San Francisco, California 94080.

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RELATED PARTY TRANSACTIONS

In addition to the compensation arrangements, including employment, termination of employment and change in control arrangements, discussed in the sections titled “Board of Directors and Corporate Governance” and “Executive Compensation,” the following is a description of certain relationships and transactions since January 1, 2020 involving our directors, executive officers, beneficial holders of more than 5% of our common stock, or entities affiliated with them.

Collaboration Agreement with Adimab

The Company has a collaboration agreement with Adimab, LLC (Adimab) under which the Company is developing antibodies discovered by Adimab in its AL001 and AL101 product candidates, and the Company is developing antibodies optimized by Adimab in its AL002 and AL003 product candidates (2014 Adimab Agreement). In August 2019, the Company signed a new collaboration agreement with Adimab for research and development of additional antibodies (2019 Adimab Agreement). The Chief Executive Officer of Adimab is a Co-founder and Chairperson of the board of directors of Alector. For the years ended December 31, 2020, 2019, and 2018, Alector incurred expenses of zero, $2.8 million, and $2.3 million for services provided by Adimab, respectively. The Company had no accrued liabilities due to Adimab as of December 31, 2020 and 2019. Under the 2014 Adimab Agreement, the Company will owe up to $3.5 million in milestone payments per program to Adimab for its product candidates. The Company will also owe low- to mid- single-digit royalty payments for commercial sales of such product candidates. Under the 2019 Adimab Agreement, the Company will owe certain milestone payments per program for its product candidates and low single-digit royalty payments for commercial sales of such product candidates.

Consulting Agreement with Dr. Richard Scheller

In December 2019, we entered into a consulting agreement with Dr. Richard Scheller, a member of our Board of Directors and a member of our Scientific Advisory Board. Pursuant to this consulting agreement, Dr. Scheller serves on SPARC and generally provides scientific advice regarding our products or services and research program. Pursuant to this agreement, Dr. Scheller receives an annualized payment of $200,000 and a stock option to purchase 100,000 shares of our common stock, vesting in equal monthly installments over a four-year period for so long as Dr. Scheller serves as a consultant under this agreement.

Participation in Follow On Offering

David Wehner, a member of our Board of Directors, purchased 20,000 shares of common stock at a purchase price per share of $25.00 for an aggregate purchase price of $500,000 in the Company’s recent public offering of common stock pursuant to a final prospectus filed with the SEC on January 30, 2020 pursuant to Rule 424(b)(4).

Related Party Transaction Policy

Our audit committee has the primary responsibility for reviewing and approving or disapproving “related party transactions,” which are transactions between us and related persons in which the aggregate amount involved exceeds or may be expected to exceed $120,000 and in which a related person has or will have a direct or indirect material interest. The charter of our audit committee provides that our audit committee shall review and approve in advance any related party transaction. We have adopted a formal written policy providing that we are not permitted to enter into any transaction that exceeds $120,000 and in which any related person has a direct or indirect material interest without the consent of our audit committee. In approving or rejecting any such transaction, our audit committee is to consider the relevant facts and circumstances available and deemed relevant to our audit committee, including whether the transaction is on terms no less favorable than terms generally available to an unaffiliated third party under the same or similar circumstances and the extent of the related person’s interest in the transaction.

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OTHER MATTERS

Fiscal Year 2020 Annual Report and SEC Filings

Our financial statements for the fiscal year ended December 31, 2020 are included in our Annual Report on Form 10-K, which we will make available to stockholders at the same time as this proxy statement. This proxy statement and our annual report are posted on our website at https://investors.alector.com and are available from the SEC at its website at www.sec.gov. You may also obtain a copy of our annual report without charge by sending a written request to Alector, Inc., Attention: Investor Relations, 131 Oyster Point Boulevard, Suite 600, South San Francisco, California 94080.

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The Board of Directors does not know of any other matters to be presented at the Annual Meeting. If any additional matters are properly presented at the Annual Meeting, the persons named in the enclosed proxy card will have discretion to vote the shares of our common stock they represent in accordance with their own judgment on such matters.

It is important that your shares of our common stock be represented at the Annual Meeting, regardless of the number of shares that you hold. You are, therefore, urged to vote by telephone or by using the Internet as instructed on the enclosed proxy card or execute and return, at your earliest convenience, the enclosed proxy card in the envelope that has also been provided.

THE BOARD OF DIRECTORS

San Francisco, California

April 28, 2021

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1. ELECTION OF DIRECTORS: O Tillman Gerngross, Ph.D. O Richard Scheller, Ph.D. O Louis J. Lavigne, Jr. Signature of Stockholder Date: Signature of Stockholder Date: Note: Please sign exactly as your name or names appear on this Proxy. When shares are held jointly, each holder should sign. When signing as executor, administrator, attorney, trustee or guardian, please give full title as such. If the signer is a corporation, please sign full corporate name by duly authorized officer, giving full title as such. If signer is a partnership, please sign in partnership name by authorized person. To change the address on your account, please check the box at right and indicate your new address in the address space above. Please note that changes to the registered name(s) on the account may not be submitted via this method. INSTRUCTIONS: To withhold authority to vote for any individual nominee(s), mark “FOR ALL EXCEPT” and fill in the circle next to each nominee you wish to withhold, as shown here: JOHN SMITH 1234 MAIN STREET APT. 203 NEW YORK, NY 10038 Please detach along perforated line and mail in the envelope provided IF you are not voting via telephone or the Internet. x COMPANY NUMBER ACCOUNT NUMBER NOTICE OF INTERNET AVAILABILITY OF PROXY MATERIAL: The Notice of Meeting, proxy statement and proxy card are available at http://www.astproxyportal.com/ast/22640 THE BOARD OF DIRECTORS RECOMMENDS A VOTE “FOR” ALL THE NOMINEES LISTED IN PROPOSAL NO. 1, “FOR” PROPOSALS 2 AND 3, AND FOR THE FREQUENCY OF EVERY “ONE YEAR” FOR PROPOSAL 4. PLEASE SIGN, DATE AND RETURN PROMPTLY IN THE ENCLOSED ENVELOPE. PLEASE MARK YOUR VOTE IN BLUE OR BLACK INK AS SHOWN HERE FOR ALL NOMINEES WITHHOLD AUTHORITY FOR ALL NOMINEES FOR ALL EXCEPT (See instructions below) NOMINEES: 20330304000000001000 4 061721 INTERNET—Access “www.voteproxy.com” and follow the on-screen instructions or scan the QR code with your smartphone. Have your proxy card available when you access the web page. TELEPHONE—Call toll-free 1-800-PROXIES (1-800-776-9437) in the United States or 1-718-921-8500 from foreign countries from any touch-tone telephone and follow the instructions. Have your proxy card available when you call. Vote online/phone until 11:59 PM EDT the day before the meeting. MAIL—Sign, date and mail your proxy card in the envelope provided as soon as possible. VIRTUALLY AT THE MEETING—The company will be hosting the meeting live via the Internet this year. To attend the meeting via the Internet please visit https://web.lumiagm.com/209804434 password: alector2021 (cap sensitive) and be sure to have available the control number. GO GREEN—e-Consent makes it easy to go paperless. With e-Consent, you can quickly access your proxy material, statements and other eligible documents online, while reducing costs, clutter and paper waste. Enroll today via www.astfinancial.com to enjoy online access. VOTING INSTRUCTIONS ANNUAL MEETING OF STOCKHOLDERS OF ALECTOR, INC. June 17, 2021 2. Ratification of the appointment of Ernst & Young, LLP as our independent registered public accounting firm for our fiscal year ending December 31, 2021. 3. Advisory vote on executive compensation. 4. Advisory vote on the frequency of advisory votes on executive compensation. TO INCLUDE ANY COMMENTS, USE THE COMMENTS BOX ON THE REVERSE SIDE OF THIS CARD. IMPORTANT NOTICE YOUR VOTE IS IMPORTANT. PLEASE SIGN, DATE AND RETURN YOUR PROXY AS SOON AS POSSIBLE. BY DOING SO, YOU MAY SAVE TEST COMPANY THE EXPENSE OF ADDITIONAL SOLICITATION. THIS PROXY WHEN PROPERLY EXECUTED WILL BE VOTED AS DIRECTED OR, IF NO DIRECTION IS GIVEN, WILL BE VOTED AS THE BOARD RECOMMENDS. MARK “X” HERE IF YOU PLAN TO ATTEND THE MEETING. FOR AGAINST ABSTAIN FOR AGAINST ABSTAIN 3 years 2 years 1 year ABSTAIN

1 1.1 14475 COMMENTS: ALECTOR, INC. Proxy Solicited on Behalf of the Board of Directors for Annual Meeting of Stockholders The undersigned hereby appoint(s) Arnon Rosenthal, Ph.D., and Shehnaaz Suliman, M.D., or any one of them, attorneys with full power of substitution and revocation to each, for and in the name of the undersigned with all the powers the undersigned would possess if personally present, to vote the shares of the undersigned in Alector, Inc. as indicated on the proposals referred to on the reverse side hereof at the annual meeting of its stockholders to be held on June 17, 2021, and at any adjournments thereof, and in their or his discretion upon any other matter which may properly come before said meeting. (Continued and to be signed on the reverse side) ANNUAL MEETING OF STOCKHOLDERS OF ALECTOR, INC. June 17, 2021 131 Oyster Point Blvd, Suite 600 South San Francisco, CA 94080