SC 13G/A

NAME OF REPORTING PERSONS

Polaris Venture Partners VI, L.P.

CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

(a) ☐ (b) ☒

SEC USE ONLY

CITIZENSHIP OR PLACE OF ORGANIZATION

Delaware

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Schedule 13G

(Rule 13d-102)

INFORMATION TO BE INCLUDED IN STATEMENTS FILED

PURSUANT TO RULES 13d-1 (b), (c) AND (d) AND AMENDMENTS THERETO FILED

PURSUANT TO 13d-2 (b)

(Amendment No. 4)

Alector, Inc.

(Name of Issuer)

Common Stock, par value $0.0001 per share

(Title of Class of Securities)

014442107

(CUSIP Number)

December 31, 2023

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

☐ Rule 13d-1(b)

☐ Rule 13d-1(c)

☒ Rule 13d-1(d)

*	The remainder of this cover page shall be filled out for a reporting person’s initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter disclosures provided in a prior cover page.

The information required on the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

(Continued on following pages)

CUSIP #014442107


NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	5	SOLE VOTING POWER 498,468 (1)
	6	SHARED VOTING POWER 0
	7	SOLE DISPOSITIVE POWER 498,468 (1)
	8	SHARED DISPOSITIVE POWER 0

(1)

All such shares are held of record by PVP VI (as defined in Item 2(a) of the Original Schedule 13G). PVM VI (as defined in Item 2(a) of the Original Schedule 13G), the general partner of PVP VI, may be deemed to have voting, investment and dispositive power with respect to these securities. David Barrett, Brian Chee, Jonathan A. Flint, Terrance G. McGuire, a member of the Issuer’s board of directors, Amir Nashat, and Bryce Youngren are the managing members of PVM VI and may each be deemed to share voting, investment and dispositive power with respect to these securities.

(2)

Based upon 95,005,947 shares of the Issuer’s Common Stock outstanding, as reported in the Issuer’s prospectus (File No. 333-270126) filed with the United States Securities and Exchange Commission (the “Commission”) pursuant to Rule 424(b)(5) on January 17, 2024 (the “Prospectus”) and assuming the underwriter does not exercise its option to purchase additional shares of Common Stock in full in connection with the offering described in the Prospectus.

CUSIP #014442107


NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	5	SOLE VOTING POWER 599,251 (1)
	6	SHARED VOTING POWER 0
	7	SOLE DISPOSITIVE POWER 599,251 (1)
	8	SHARED DISPOSITIVE POWER 0

(1)

All such shares are held of record by PVPFF VI (as defined in Item 2(a) of the Original Schedule 13G). PVM VI, the general partner of PVPFF VI, may be deemed to have voting, investment and dispositive power with respect to these securities. David Barrett, Brian Chee, Jonathan A. Flint, Terrance G. McGuire, a member of the Issuer’s board of directors, Amir Nashat, and Bryce Youngren are the managing members of PVM VI and may each be deemed to share voting, investment and dispositive power with respect to these securities.

(2)	Based upon 95,005,947 shares of the Issuer’s Common Stock outstanding as of January 17, 2024, as set forth in the Prospectus.

CUSIP #014442107


NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	5	SOLE VOTING POWER 7,831,004 (1)
	6	SHARED VOTING POWER 0
	7	SOLE DISPOSITIVE POWER 7,831,004 (1)
	8	SHARED DISPOSITIVE POWER 0

(1)

All such shares are held of record by PVP VI (AIV) (as defined in Item 2(a) of the Original Schedule 13G). PVM VI, the general partner of PVP VI (AIV), may be deemed to have voting, investment and dispositive power with respect to these securities. David Barrett, Brian Chee, Jonathan A. Flint, Terrance G. McGuire, a member of the Issuer’s board of directors, Amir Nashat, and Bryce Youngren are the managing members of PVM VI and may each be deemed to share voting, investment and dispositive power with respect to these securities.

(2)	Based upon 95,005,947 shares of the Issuer’s Common Stock outstanding as of January 17, 2024, as set forth in the Prospectus.

CUSIP #014442107


NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	5	SOLE VOTING POWER 1,925,094 (1)
	6	SHARED VOTING POWER 0
	7	SOLE DISPOSITIVE POWER 1,925,094 (1)
	8	SHARED DISPOSITIVE POWER 0

(1)

All such shares are held of record by PVP VI (AIV-B) (as defined in Item 2(a) of the Original Schedule 13G). PVM VI, the general partner of PVP VI (AIV-B), may be deemed to have voting, investment and dispositive power with respect to these securities. David Barrett, Brian Chee, Jonathan A. Flint, Terrance G. McGuire, a member of the Issuer’s board of directors, Amir Nashat, and Bryce Youngren are the managing members of PVM VI and may each be deemed to share voting, investment and dispositive power with respect to these securities.

(2)	Based upon 95,005,947 shares of the Issuer’s Common Stock outstanding as of January 17, 2024, as set forth in the Prospectus.

CUSIP #014442107


NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	5	SOLE VOTING POWER 0
	6	SHARED VOTING POWER 10,853,817 (1)
	7	SOLE DISPOSITIVE POWER 0
	8	SHARED DISPOSITIVE POWER 10,853,817 (1)

(1)

498,468 of such shares are held of record by PVP VI, 599,251 of such shares are held of record by PVPFF VI, 7,831,004 of such shares are held of record by PVP VI (AIV) and 1,925,094 of such shares are held of record by PVP VI (AIV-B). PVM VI, the general partner of each of PVP VI, PVPFF VI, PVP VI (AIV) and PVP VI (AIV-B), may be deemed to have voting, investment and dispositive power with respect to these securities. David Barrett, Brian Chee, Jonathan A. Flint, Terrance G. McGuire, a member of the Issuer’s board of directors, Amir Nashat, and Bryce Youngren are the managing members of PVM VI and may each be deemed to share voting, investment and dispositive power with respect to these securities.

(2)	Based upon 95,005,947 shares of the Issuer’s Common Stock outstanding as of January 17, 2024, as set forth in the Prospectus.

CUSIP #014442107


NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	5	SOLE VOTING POWER 0
	6	SHARED VOTING POWER 10,853,817 (1)
	7	SOLE DISPOSITIVE POWER 0
	8	SHARED DISPOSITIVE POWER 10,853,817 (1)

(1)

(2)	Based upon 95,005,947 shares of the Issuer’s Common Stock outstanding as of January 17, 2024, as set forth in the Prospectus.

CUSIP #014442107


NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	5	SOLE VOTING POWER 30,749 (1)
	6	SHARED VOTING POWER 10,853,817 (2)
	7	SOLE DISPOSITIVE POWER 30,749 (1)
	8	SHARED DISPOSITIVE POWER 10,853,817 (2)

(1)	All of such shares are held by Brian Chee directly.

(2)

(3)	Based upon 95,005,947 shares of the Issuer’s Common Stock outstanding as of January 17, 2024, as set forth in the Prospectus.

CUSIP #014442107


NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	5	SOLE VOTING POWER 58,686 (1)
	6	SHARED VOTING POWER 10,853,817 (2)
	7	SOLE DISPOSITIVE POWER 58,686 (1)
	8	SHARED DISPOSITIVE POWER 10,853,817 (2)

(1)	All of such shares are held by Jonathan A. Flint directly.

(2)

(3)	Based upon 95,005,947 shares of the Issuer’s Common Stock outstanding as of January 17, 2024, as set forth in the Prospectus.

CUSIP #014442107


NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	5	SOLE VOTING POWER 121,917 (1)
	6	SHARED VOTING POWER 10,853,817 (2)
	7	SOLE DISPOSITIVE POWER 121,917 (1)
	8	SHARED DISPOSITIVE POWER 10,853,817 (2)

(1)

28,746 of such shares are held of record directly by Terrance G. McGuire and 93,171 of such shares consist of Common Stock subject to stock option awards that have been granted to Terrance G. McGuire in his capacity as a director of the Issuer and that are exercisable as of or within 60 days of the filing of this Amendment No. 4 (as defined in the Introductory Note below). Excludes 3,090 shares of Common Stock subject to option awards that have been granted to Terrance G. McGuire in his capacity as a director of the Issuer and that are exercisable as of now or within 60 days of February 14, 2024.

(2)

(3)

Based upon 95,099,118 shares of the Issuer’s Common Stock, calculated as follows: (i) 93,171 shares of the Issuer’s Common Stock subject to stock option awards or that represent restricted stock units that have been granted to Mr. McGuire in his capacity as director of the Issuer and that are exercisable as of or within 60 days of the filing of this Amendment No. 4 plus (ii) 95,005,947 shares of the Issuer’s Common Stock outstanding as of January 17, 2024, as set forth in the Prospectus.

CUSIP #014442107


NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	5	SOLE VOTING POWER 13,133 (1)
	6	SHARED VOTING POWER 10,853,817 (2)
	7	SOLE DISPOSITIVE POWER 13,133 (1)
	8	SHARED DISPOSITIVE POWER 10,853,817 (2)

(1)	All of such shares are held by Amir Nashat directly.

(2)

(3)	Based upon 95,005,947 shares of the Issuer’s Common Stock outstanding as of January 17, 2024, as set forth in the Prospectus.

CUSIP #014442107


NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	5	SOLE VOTING POWER 34,399 (1)
	6	SHARED VOTING POWER 10,853,817 (2)
	7	SOLE DISPOSITIVE POWER 34,399 (1)
	8	SHARED DISPOSITIVE POWER 10,853,817 (2)

(1)	All of such shares are held by Bryce Youngren directly.

(2)

(3)	Based upon 95,005,947 shares of the Issuer’s Common Stock outstanding as of January 17, 2024, as set forth in the Prospectus.

CUSIP #014442107

SCHEDULE 13G

Introductory Note: This Amendment No. 4 (this “Amendment No. 4”) amends and supplements the Schedule 13G initially filed with the Commission on February 12, 2020, as amended by Amendment No. 1 filed with the Commission on February 12, 2021, Amendment No. 2 filed with the Commission on February 11, 2022 and Amendment No. 3 filed with the Commission on February 7, 2023 (collectively, the “Original Schedule 13G”). Only those items that are hereby reported are amended; all other items reported in the Original Schedule 13G remain unchanged. Information given in response to each item shall be deemed incorporated by reference in all other items, as applicable. Capitalized terms not defined in this Amendment No. 4 have the meanings ascribed to them in the Original Schedule 13G.

ITEM 2(B). ADDRESS OF PRINCIPAL OFFICE

The address for each of the Reporting Persons except for Chee is:

c/o Polaris Partners

One Marina Park Drive, 8^th Floor

Boston, MA 02210

The address for Chee is:

c/o Polaris Partners

1 Letterman Drive

Building C, Suite 3600

San Francisco, CA 94129

ITEM 4. OWNERSHIP

Except as otherwise indicated on the cover pages for the Reporting Persons, the following information with respect to the ownership of the common stock of the Issuer by the Reporting Persons filing this Statement is provided as of December 31, 2023:

(a) Amount beneficially owned:

See Row 9 of cover page for each Reporting Person and the corresponding footnotes.*

(b) Percent of Class:

See Row 11 of cover page for each Reporting Person and the corresponding footnotes.*

(i) Sole power to vote or to direct the vote:

See Row 5 of cover page for each Reporting Person and the corresponding footnotes.*

(ii) Shared power to vote or to direct the vote:

See Row 6 of cover page for each Reporting Person and the corresponding footnotes.*

(iii) Sole power to dispose or to direct the disposition of:

See Row 7 of cover page for each Reporting Person and the corresponding footnotes.*

(iv) Shared power to dispose or to direct the disposition of:

See Row 8 of cover page for each Reporting Person and the corresponding footnotes.*

*	Each of the Reporting Persons disclaims beneficial ownership as to such securities, except to the extent of his, her or its pecuniary interest therein.

CUSIP #014442107

SIGNATURES

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Date: February 9, 2024


POLARIS VENTURE PARTNERS VI, L.P.

By: Polaris Venture Management Co. VI, L.L.C.

By:		*
		Authorized Signatory

POLARIS VENTURE PARTNERS VI (AIV), L.P.

By:		Polaris Venture Management Co. VI, L.L.C.

By:		*
		Authorized Signatory

POLARIS VENTURE PARTNERS VI (AIV-B), L.P.

By:		Polaris Venture Management Co. VI, L.L.C.

By:		*
		Authorized Signatory

POLARIS VENTURE PARTNERS FOUNDERS’ FUND VI, L.P.

By:		Polaris Venture Management Co. VI, L.L.C.

By:		*
		Authorized Signatory

POLARIS VENTURE MANAGEMENT CO. VI, L.L.C.

By:		*
		Authorized Signatory

JONATHAN A. FLINT

By:		*
		Jonathan A. Flint


TERRANCE G. MCGUIRE

By:		*
		Terrance G. McGuire

BRYCE YOUNGREN

By:		*
		Bryce Youngren

DAVID BARRETT

By:		*
		David Barrett

BRIAN CHEE

By:		*
		Brian Chee

AMIR NASHAT

By:		*
		Amir Nashat

*By:		/s/ Lauren Crockett
Name:		Lauren Crockett
		Attorney-in-Fact

[*This Schedule 13G was executed pursuant to a Power of Attorney. Note that copies of the applicable Powers of Attorney are already on file with the appropriate agencies.]