Sec Form 4 Filing - MCGUIRE TERRANCE @ Alector, Inc. - 2022-06-16

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person MCGUIRE TERRANCE 2. Issuer Name and Ticker or Trading Symbol Alector, Inc. [ ALEC] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director _____ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O POLARIS PARTNERS, ONE MARINA PARK DRIVE, 10TH FLOOR 3. Date of Earliest Transaction (MM/DD/YY) 06/16/2022 (Street) BOSTON, MA02210 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 06/16/2022 A 9,459( 1 ) A $ 0 15,888 D Common Stock 12,353,817 I See footnote( 2 ) Common Stock 13,133 I See footnote( 3 )

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Stock Option (right to buy) $ 8.07 06/16/2022 A 18,918 ( 4 ) 06/16/2032 Common Stock 18,918 $ 0 18,918 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other MCGUIRE TERRANCE C/O POLARIS PARTNERS ONE MARINA PARK DRIVE, 10TH FLOOR BOSTON, MA02210 X Signatures /s/ Calvin Yu, by power of attorney 06/21/2022 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The reported shares are represented by restricted stock units, or RSUs, which vest on the earlier of (i) June 16, 2023 or (ii) the date of the Issuer's next annual meeting of stockholders. ( 2 )Includes 682,069 shares are held by Polaris Venture Partners Founders' Fund VI, L.P. ("PVPFF VI"), 8,968,544 shares are held by Polaris Venture Partners VI (AIV), L.P. ("PVP VI AIV"), 2,204,736 shares are held by Polaris Venture Partners VI (AIV-B), L.P. (f/k/a PVP VI (AIV) Feeder Corp. Holding Partnership, L.P., "PVP VI AIV-B" and 498,468 shares are held by Polaris Venture Partners VI, L.P. ("PVP VI")(collectively, the "Polaris Funds"). As a Managing Member of Polaris Venture Management Co. VI, L.L.C. ("PVM"). The reporting person may be deemed to share the power to vote and dispose of the shares held by the Polaris Funds. The reporting person disclaims beneficial ownership of the securities held by the Polaris Funds, and this report shall not be deemed an admission that he is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of his respective pecuniary interest therein. ( 3 )The shares are held by the McGuire Family Trust (the "Family Trust"). The reporting person is the donor of the Family Trust and may be deemed to have shared power to vote and dispose of the shares held by the Family Trust. ( 4 )The shares subject to the option vest in 12 equal monthly installments beginning on July 16, 2022, or if earlier, the date of the Issuer's next annual meeting of stockholders.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

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