<SEC-DOCUMENT>0001193125-25-280330.txt : 20251113
<SEC-HEADER>0001193125-25-280330.hdr.sgml : 20251113
<ACCEPTANCE-DATETIME>20251113164155
ACCESSION NUMBER:		0001193125-25-280330
CONFORMED SUBMISSION TYPE:	SCHEDULE 13G/A
PUBLIC DOCUMENT COUNT:		1
FILED AS OF DATE:		20251113
DATE AS OF CHANGE:		20251113

SUBJECT COMPANY:	

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			Alector, Inc.
		CENTRAL INDEX KEY:			0001653087
		STANDARD INDUSTRIAL CLASSIFICATION:	BIOLOGICAL PRODUCTS (NO DIAGNOSTIC SUBSTANCES) [2836]
		ORGANIZATION NAME:           	03 Life Sciences
		EIN:				822933343
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		SCHEDULE 13G/A
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	005-90858
		FILM NUMBER:		251479266

	BUSINESS ADDRESS:	
		STREET 1:		131 OYSTER POINT BLVD., SUITE 600
		CITY:			SOUTH SAN FRANCISCO
		STATE:			CA
		ZIP:			94080
		BUSINESS PHONE:		415-231-5660

	MAIL ADDRESS:	
		STREET 1:		131 OYSTER POINT BLVD., SUITE 600
		CITY:			SOUTH SAN FRANCISCO
		STATE:			CA
		ZIP:			94080

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	Alector LLC
		DATE OF NAME CHANGE:	20150915

FILED BY:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			Polaris Venture Partners VI, L.P.
		CENTRAL INDEX KEY:			0001493463
		ORGANIZATION NAME:           	
		EIN:				000000000
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		SCHEDULE 13G/A

	BUSINESS ADDRESS:	
		STREET 1:		ONE MARINA PARK DRIVE, 8TH FLOOR
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02210
		BUSINESS PHONE:		781-290-0770

	MAIL ADDRESS:	
		STREET 1:		ONE MARINA PARK DRIVE, 8TH FLOOR
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02210
</SEC-HEADER>
<DOCUMENT>
<TYPE>SCHEDULE 13G/A
<SEQUENCE>1
<FILENAME>primary_doc.xml
<TEXT>
<XML>
<?xml version="1.0" encoding="UTF-8"?><edgarSubmission xmlns="http://www.sec.gov/edgar/schedule13g" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <headerData>
    <submissionType>SCHEDULE 13G/A</submissionType>
    <filerInfo>
      <filer>
        <filerCredentials>
          <cik>0001493463</cik>
          <ccc>XXXXXXXX</ccc>
        </filerCredentials>
      </filer>
      <liveTestFlag>LIVE</liveTestFlag>



    </filerInfo>
  </headerData>
  <formData>
    <coverPageHeader>
      <amendmentNo>6</amendmentNo>
      <securitiesClassTitle>Common Stock, $0.0001 par value per share</securitiesClassTitle>
      <eventDateRequiresFilingThisStatement>09/30/2025</eventDateRequiresFilingThisStatement>
      <issuerInfo>
        <issuerCik>0001653087</issuerCik>
        <issuerName>Alector, Inc.</issuerName>
        <issuerCusip>014442107</issuerCusip>
        <issuerPrincipalExecutiveOfficeAddress>
          <street1 xmlns="http://www.sec.gov/edgar/common">131 OYSTER POINT BLVD.</street1>
          <street2 xmlns="http://www.sec.gov/edgar/common">SUITE 600</street2>
          <city xmlns="http://www.sec.gov/edgar/common">SOUTH SAN FRANCISCO</city>
          <stateOrCountry xmlns="http://www.sec.gov/edgar/common">CA</stateOrCountry>
          <zipCode xmlns="http://www.sec.gov/edgar/common">94080</zipCode>
        </issuerPrincipalExecutiveOfficeAddress>
      </issuerInfo>
      <designateRulesPursuantThisScheduleFiled>
        <designateRulePursuantThisScheduleFiled>Rule 13d-1(d)</designateRulePursuantThisScheduleFiled>
      </designateRulesPursuantThisScheduleFiled>
    </coverPageHeader>
    <coverPageHeaderReportingPersonDetails>


      <reportingPersonName>Polaris Venture Partners VI, L.P.</reportingPersonName>
      <memberGroup>b</memberGroup>
      <citizenshipOrOrganization>DE</citizenshipOrOrganization>
      <reportingPersonBeneficiallyOwnedNumberOfShares>
        <soleVotingPower>498468</soleVotingPower>
        <sharedVotingPower>0</sharedVotingPower>
        <soleDispositivePower>498468</soleDispositivePower>
        <sharedDispositivePower>0</sharedDispositivePower>
      </reportingPersonBeneficiallyOwnedNumberOfShares>
      <reportingPersonBeneficiallyOwnedAggregateNumberOfShares>498468</reportingPersonBeneficiallyOwnedAggregateNumberOfShares>
      <aggregateAmountExcludesCertainSharesFlag>N</aggregateAmountExcludesCertainSharesFlag>
      <classPercent>0.5</classPercent>
      <typeOfReportingPerson>PN</typeOfReportingPerson>
      <comments>
All shares are held of record by PVP VI (as defined in Item 2(a) of the Original Schedule 13G (as defined below)). 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, 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.

The percentage in Row 11 is based on 109,151,472 shares of the Issuer's common stock ("Common Stock") outstanding as of October 31, 2025, as set forth in the Issuer's quarterly report on Form 10-Q for the quarter ended September 30, 2025, filed with the United States Securities and Exchange Commission (the "Commission") on November 6, 2025 (the "Form 10-Q"). </comments>
    </coverPageHeaderReportingPersonDetails>
    <coverPageHeaderReportingPersonDetails>


      <reportingPersonName>Polaris Venture Partners Founders' Fund VI, L.P.</reportingPersonName>
      <memberGroup>b</memberGroup>
      <citizenshipOrOrganization>DE</citizenshipOrOrganization>
      <reportingPersonBeneficiallyOwnedNumberOfShares>
        <soleVotingPower>378403</soleVotingPower>
        <sharedVotingPower>0</sharedVotingPower>
        <soleDispositivePower>378403</soleDispositivePower>
        <sharedDispositivePower>0</sharedDispositivePower>
      </reportingPersonBeneficiallyOwnedNumberOfShares>
      <reportingPersonBeneficiallyOwnedAggregateNumberOfShares>378403</reportingPersonBeneficiallyOwnedAggregateNumberOfShares>
      <aggregateAmountExcludesCertainSharesFlag>N</aggregateAmountExcludesCertainSharesFlag>
      <classPercent>0.3</classPercent>
      <typeOfReportingPerson>PN</typeOfReportingPerson>
      <comments>
All 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, 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.

The percentage in Row 11 is based on 109,151,472 shares of Common Stock outstanding as of October 31, 2025, as set forth in the Form 10-Q.</comments>
    </coverPageHeaderReportingPersonDetails>
    <coverPageHeaderReportingPersonDetails>


      <reportingPersonName>Polaris Venture Partners VI (AIV), L.P.</reportingPersonName>
      <memberGroup>b</memberGroup>
      <citizenshipOrOrganization>DE</citizenshipOrOrganization>
      <reportingPersonBeneficiallyOwnedNumberOfShares>
        <soleVotingPower>4797563</soleVotingPower>
        <sharedVotingPower>0</sharedVotingPower>
        <soleDispositivePower>4797563</soleDispositivePower>
        <sharedDispositivePower>0</sharedDispositivePower>
      </reportingPersonBeneficiallyOwnedNumberOfShares>
      <reportingPersonBeneficiallyOwnedAggregateNumberOfShares>4797563</reportingPersonBeneficiallyOwnedAggregateNumberOfShares>
      <aggregateAmountExcludesCertainSharesFlag>N</aggregateAmountExcludesCertainSharesFlag>
      <classPercent>4.4</classPercent>
      <typeOfReportingPerson>PN</typeOfReportingPerson>
      <comments>
All 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, 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.

The percentage in Row 11 is based on 109,151,472 shares of Common Stock outstanding as of October 31, 2025, as set forth in the Form 10-Q.</comments>
    </coverPageHeaderReportingPersonDetails>
    <coverPageHeaderReportingPersonDetails>


      <reportingPersonName>Polaris Venture Partners VI (AIV-B), L.P.</reportingPersonName>
      <memberGroup>b</memberGroup>
      <citizenshipOrOrganization>DE</citizenshipOrOrganization>
      <reportingPersonBeneficiallyOwnedNumberOfShares>
        <soleVotingPower>1179383</soleVotingPower>
        <sharedVotingPower>0</sharedVotingPower>
        <soleDispositivePower>1179383</soleDispositivePower>
        <sharedDispositivePower>0</sharedDispositivePower>
      </reportingPersonBeneficiallyOwnedNumberOfShares>
      <reportingPersonBeneficiallyOwnedAggregateNumberOfShares>1179383</reportingPersonBeneficiallyOwnedAggregateNumberOfShares>
      <aggregateAmountExcludesCertainSharesFlag>N</aggregateAmountExcludesCertainSharesFlag>
      <classPercent>1.1</classPercent>
      <typeOfReportingPerson>PN</typeOfReportingPerson>
      <comments>
All 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, 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.

Based on 109,151,472 shares of Common Stock outstanding as of October 31, 2025, as set forth in the Form 10-Q.</comments>
    </coverPageHeaderReportingPersonDetails>
    <coverPageHeaderReportingPersonDetails>


      <reportingPersonName>Polaris Venture Management Co VI, L.L.C.</reportingPersonName>
      <memberGroup>b</memberGroup>
      <citizenshipOrOrganization>DE</citizenshipOrOrganization>
      <reportingPersonBeneficiallyOwnedNumberOfShares>
        <soleVotingPower>0</soleVotingPower>
        <sharedVotingPower>6853817</sharedVotingPower>
        <soleDispositivePower>0</soleDispositivePower>
        <sharedDispositivePower>6853817</sharedDispositivePower>
      </reportingPersonBeneficiallyOwnedNumberOfShares>
      <reportingPersonBeneficiallyOwnedAggregateNumberOfShares>6853817</reportingPersonBeneficiallyOwnedAggregateNumberOfShares>
      <aggregateAmountExcludesCertainSharesFlag>N</aggregateAmountExcludesCertainSharesFlag>
      <classPercent>6.3</classPercent>
      <typeOfReportingPerson>OO</typeOfReportingPerson>
      <comments>
The shares reported in Rows 6 and 8 consist of (i) 498,468 shares held of record by PVP VI, (ii) 378,403 shares held of record by PVPFF VI, (iii) 4,797,563 shares held of record by PVP VI (AIV) and (iv) 1,179,383 shares 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, 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.

The percentage in Row 11 is based on 109,151,472 shares of Common Stock outstanding as of October 31, 2025, as set forth in the Form 10-Q.</comments>
    </coverPageHeaderReportingPersonDetails>
    <coverPageHeaderReportingPersonDetails>


      <reportingPersonName>David Barrett</reportingPersonName>
      <memberGroup>b</memberGroup>
      <citizenshipOrOrganization>X1</citizenshipOrOrganization>
      <reportingPersonBeneficiallyOwnedNumberOfShares>
        <soleVotingPower>26254</soleVotingPower>
        <sharedVotingPower>6853817</sharedVotingPower>
        <soleDispositivePower>26254</soleDispositivePower>
        <sharedDispositivePower>6853817</sharedDispositivePower>
      </reportingPersonBeneficiallyOwnedNumberOfShares>
      <reportingPersonBeneficiallyOwnedAggregateNumberOfShares>6880071</reportingPersonBeneficiallyOwnedAggregateNumberOfShares>
      <aggregateAmountExcludesCertainSharesFlag>N</aggregateAmountExcludesCertainSharesFlag>
      <classPercent>6.3</classPercent>
      <typeOfReportingPerson>IN</typeOfReportingPerson>
      <comments>
The shares reported in Rows 5 and 7 are held directly by David Barrett.

The shares reported in Rows 6 and 8 consist of (i) 498,468 shares held of record by PVP VI, (ii) 378,403 shares held of record by PVPFF VI, (iii) 4,797,563 shares held of record by PVP VI (AIV) and (iv) 1,179,383 shares 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, 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.

The percentage in Row 11 is based on 109,151,472 shares of Common Stock outstanding as of October 31, 2025, as set forth in the Form 10-Q.</comments>
    </coverPageHeaderReportingPersonDetails>
    <coverPageHeaderReportingPersonDetails>


      <reportingPersonName>Brian Chee</reportingPersonName>
      <memberGroup>b</memberGroup>
      <citizenshipOrOrganization>X1</citizenshipOrOrganization>
      <reportingPersonBeneficiallyOwnedNumberOfShares>
        <soleVotingPower>26267</soleVotingPower>
        <sharedVotingPower>6853817</sharedVotingPower>
        <soleDispositivePower>26267</soleDispositivePower>
        <sharedDispositivePower>6853817</sharedDispositivePower>
      </reportingPersonBeneficiallyOwnedNumberOfShares>
      <reportingPersonBeneficiallyOwnedAggregateNumberOfShares>6880084</reportingPersonBeneficiallyOwnedAggregateNumberOfShares>
      <aggregateAmountExcludesCertainSharesFlag>N</aggregateAmountExcludesCertainSharesFlag>
      <classPercent>6.3</classPercent>
      <typeOfReportingPerson>IN</typeOfReportingPerson>
      <comments>
The shares reported in Rows 5 and 7 are held directly by Brian Chee.

The shares reported in Rows 6 and 8 consist of (i) 498,468 shares held of record by PVP VI, (ii) 378,403 shares held of record by PVPFF VI (iii) 4,797,563 shares held of record by PVP VI (AIV) and (iv) 1,179,383 shares 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, 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.

The percentage in Row 11 is based on 109,151,472 shares of Common Stock outstanding as of October 31, 2025, as set forth in the Form 10-Q.</comments>
    </coverPageHeaderReportingPersonDetails>
    <coverPageHeaderReportingPersonDetails>


      <reportingPersonName>Jonathan A. Flint</reportingPersonName>
      <memberGroup>b</memberGroup>
      <citizenshipOrOrganization>X1</citizenshipOrOrganization>
      <reportingPersonBeneficiallyOwnedNumberOfShares>
        <soleVotingPower>39125</soleVotingPower>
        <sharedVotingPower>6853817</sharedVotingPower>
        <soleDispositivePower>39125</soleDispositivePower>
        <sharedDispositivePower>6853817</sharedDispositivePower>
      </reportingPersonBeneficiallyOwnedNumberOfShares>
      <reportingPersonBeneficiallyOwnedAggregateNumberOfShares>6892942</reportingPersonBeneficiallyOwnedAggregateNumberOfShares>
      <aggregateAmountExcludesCertainSharesFlag>N</aggregateAmountExcludesCertainSharesFlag>
      <classPercent>6.3</classPercent>
      <typeOfReportingPerson>IN</typeOfReportingPerson>
      <comments>
The shares reported in Rows 5 and 7 are held directly by Jonathan A. Flint.

The shares reported in Rows 6 and 8 consist of (i) 498,468 shares held of record by PVP VI, (ii) 378,403 shares held of record by PVPFF VI (iii) 4,797,563 shares held of record by PVP VI (AIV) and (iv) 1,179,383 shares 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, 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.

The percentage in Row 11 is based on 109,151,472 shares of Common Stock outstanding as of October 31, 2025, as set forth in the Form 10-Q.</comments>
    </coverPageHeaderReportingPersonDetails>
    <coverPageHeaderReportingPersonDetails>


      <reportingPersonName>Terrance G. McGuire</reportingPersonName>
      <memberGroup>b</memberGroup>
      <citizenshipOrOrganization>X1</citizenshipOrOrganization>
      <reportingPersonBeneficiallyOwnedNumberOfShares>
        <soleVotingPower>241434</soleVotingPower>
        <sharedVotingPower>6853817</sharedVotingPower>
        <soleDispositivePower>241434</soleDispositivePower>
        <sharedDispositivePower>6853817</sharedDispositivePower>
      </reportingPersonBeneficiallyOwnedNumberOfShares>
      <reportingPersonBeneficiallyOwnedAggregateNumberOfShares>7095251</reportingPersonBeneficiallyOwnedAggregateNumberOfShares>
      <aggregateAmountExcludesCertainSharesFlag>N</aggregateAmountExcludesCertainSharesFlag>
      <classPercent>6.5</classPercent>
      <typeOfReportingPerson>IN</typeOfReportingPerson>
      <comments>
The shares reported in Rows 5 and 7 consist of (i) 70,719 shares held directly by Terrance G. McGuire, (ii) 144,465 shares held by McGuire Family Trust, and (iii) 26,250 shares consist of restricted stock units that have been granted to Terrance G. McGuire in his capacity as a former director of the Issuer. Terrance G. McGuire is the donor of the McGuire Family Trust and may be deemed to share voting, investment and dispositive power with respect to the shares held by the McGuire Family Trust.

The shares reported in Rows 6 and 8 consist of (i) 498,468 shares held of record by PVP VI, (ii) 378,403 shares held of record by PVPFF VI (iii) 4,797,563 shares held of record by PVP VI (AIV) and (iv) 1,179,383 shares 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, 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.

The percentage in Row 11 is based on 109,177,722 shares of Common Stock, calculated as follows: (i) 26,250 shares that represent restricted stock units that have been granted to Mr. McGuire in his capacity as a former director of the Issuer plus (ii) 109,151,472 shares of Common Stock outstanding as of October 31, 2025, as set forth in the Form 10-Q.</comments>
    </coverPageHeaderReportingPersonDetails>
    <coverPageHeaderReportingPersonDetails>


      <reportingPersonName>Amir Nashat</reportingPersonName>
      <memberGroup>b</memberGroup>
      <citizenshipOrOrganization>X1</citizenshipOrOrganization>
      <reportingPersonBeneficiallyOwnedNumberOfShares>
        <soleVotingPower>78800</soleVotingPower>
        <sharedVotingPower>6853817</sharedVotingPower>
        <soleDispositivePower>78800</soleDispositivePower>
        <sharedDispositivePower>6853817</sharedDispositivePower>
      </reportingPersonBeneficiallyOwnedNumberOfShares>
      <reportingPersonBeneficiallyOwnedAggregateNumberOfShares>6932617</reportingPersonBeneficiallyOwnedAggregateNumberOfShares>
      <aggregateAmountExcludesCertainSharesFlag>N</aggregateAmountExcludesCertainSharesFlag>
      <classPercent>6.4</classPercent>
      <typeOfReportingPerson>IN</typeOfReportingPerson>
      <comments>
The shares reported in Rows 5 and 7 are held directly by Amir Nashat.

The shares reported in Rows 6 and 8 consist of (i) 498,468 shares held of record by PVP VI, (ii) 378,403 shares held of record by PVPFF VI, (iii) 4,797,563 shares held of record by PVP VI (AIV) and (iv) 1,179,383 shares 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, 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.

The percentage in Row 11 is based on 109,151,472 shares of Common Stock outstanding as of October 31, 2025, as set forth in the Form 10-Q.</comments>
    </coverPageHeaderReportingPersonDetails>
    <coverPageHeaderReportingPersonDetails>


      <reportingPersonName>Bryce Youngren</reportingPersonName>
      <memberGroup>b</memberGroup>
      <citizenshipOrOrganization>X1</citizenshipOrOrganization>
      <reportingPersonBeneficiallyOwnedNumberOfShares>
        <soleVotingPower>91332</soleVotingPower>
        <sharedVotingPower>6853817</sharedVotingPower>
        <soleDispositivePower>91332</soleDispositivePower>
        <sharedDispositivePower>6853817</sharedDispositivePower>
      </reportingPersonBeneficiallyOwnedNumberOfShares>
      <reportingPersonBeneficiallyOwnedAggregateNumberOfShares>6945149</reportingPersonBeneficiallyOwnedAggregateNumberOfShares>
      <aggregateAmountExcludesCertainSharesFlag>N</aggregateAmountExcludesCertainSharesFlag>
      <classPercent>6.4</classPercent>
      <typeOfReportingPerson>IN</typeOfReportingPerson>
      <comments>
The shares reported in Rows 5 and 7 are held directly by Bryce Youngren.

The shares reported in Rows 6 and 8 consist of (i) 498,468 shares held of record by PVP VI, (ii) 378,403 shares held of record by PVPFF VI (iii) 4,797,563 shares held of record by PVP VI (AIV) and (iv) 1,179,383 shares 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, 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.

The percentage in Row 11 is based on 109,151,472 shares of Common Stock outstanding as of October 31, 2025, as set forth in the Form 10-Q.</comments>
    </coverPageHeaderReportingPersonDetails>
    <items>
      <item1>
        <issuerName>Alector, Inc.</issuerName>
        <issuerPrincipalExecutiveOfficeAddress>131 OYSTER POINT BLVD., SUITE 600, SOUTH SAN FRANCISCO, CA, 94080</issuerPrincipalExecutiveOfficeAddress>
      </item1>
      <item2>
        <filingPersonName>This Amendment No. 6 (this "Amendment") 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, Amendment No. 3 filed with the Commission on February 7, 2023, Amendment No. 4 filed with the Commission on February 9, 2024 and Amendment No. 5 filed with the Commission on November 12, 2024 (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 have the meanings ascribed to them in the Original Schedule 13G.

The following information in Item 4 with respect to the ownership of the Issuer's Common Stock by the Reporting Persons filing this Amendment No. 6 is provided as of November 6, 2025. Each of the Reporting Persons disclaims beneficial ownership of the shares of Common Stock reported in this Amendment No. 6, except for the shares, if any, such Reporting Person holds of record and to the extent of such Reporting Person's pecuniary interest therein.</filingPersonName>
      </item2>
      <item3>
        <notApplicableFlag>N</notApplicableFlag>
      </item3>
      <item4>
        <amountBeneficiallyOwned>See Row 9 of cover page for each Reporting Person and the corresponding footnotes.</amountBeneficiallyOwned>
        <classPercent>See Row 11 of cover page for each Reporting Person and the corresponding footnotes.</classPercent>
        <numberOfSharesPersonHas>
          <solePowerOrDirectToVote>See Row 5 of cover page for each Reporting Person and the corresponding footnotes.</solePowerOrDirectToVote>
          <sharedPowerOrDirectToVote>See Row 6 of cover page for each Reporting Person and the corresponding footnotes.</sharedPowerOrDirectToVote>
          <solePowerOrDirectToDispose>See Row 7 of cover page for each Reporting Person and the corresponding footnotes.</solePowerOrDirectToDispose>
          <sharedPowerOrDirectToDispose>See Row 8 of cover page for each Reporting Person and the corresponding footnotes.</sharedPowerOrDirectToDispose>
        </numberOfSharesPersonHas>
      </item4>
      <item5>
        <notApplicableFlag>N</notApplicableFlag>
      </item5>
      <item6>
        <notApplicableFlag>N</notApplicableFlag>
      </item6>
      <item7>
        <notApplicableFlag>N</notApplicableFlag>
      </item7>
      <item8>
        <notApplicableFlag>N</notApplicableFlag>
      </item8>
      <item9>
        <notApplicableFlag>N</notApplicableFlag>
      </item9>
      <item10>
        <notApplicableFlag>N</notApplicableFlag>
      </item10>
    </items>
    <signatureInformation>
      <reportingPersonName>Polaris Venture Partners VI, L.P.</reportingPersonName>
      <signatureDetails>
        <signature>/s/ Lauren Crockett</signature>
        <title>Lauren Crockett/ Authorized Signatory of Polaris Venture Management Co. VI, L.L.C., general partner of Polaris Venture Partners VI, L.P.</title>
        <date>11/13/2025</date>
      </signatureDetails>
    </signatureInformation>
    <signatureInformation>
      <reportingPersonName>Polaris Venture Partners Founders' Fund VI, L.P.</reportingPersonName>
      <signatureDetails>
        <signature>/s/ Lauren Crockett</signature>
        <title>Lauren Crockett/ Authorized Signatory of Polaris Venture Management Co. VI, L.L.C., GP of Polaris Venture Partners Founders' Fund VI, L.P.</title>
        <date>11/13/2025</date>
      </signatureDetails>
    </signatureInformation>
    <signatureInformation>
      <reportingPersonName>Polaris Venture Partners VI (AIV), L.P.</reportingPersonName>
      <signatureDetails>
        <signature>/s/ Lauren Crockett</signature>
        <title>Lauren Crockett/ Authorized Signatory of Polaris Venture Management Co. VI, L.L.C., general partner of Polaris Venture Partners VI (AIV), L.P.</title>
        <date>11/13/2025</date>
      </signatureDetails>
    </signatureInformation>
    <signatureInformation>
      <reportingPersonName>Polaris Venture Partners VI (AIV-B), L.P.</reportingPersonName>
      <signatureDetails>
        <signature>/s/ Lauren Crockett</signature>
        <title>Lauren Crockett/ Authorized Signatory of Polaris Venture Management Co. VI, L.L.C., general partner of Polaris Venture Partners VI (AIV-B), L.P.</title>
        <date>11/13/2025</date>
      </signatureDetails>
    </signatureInformation>
    <signatureInformation>
      <reportingPersonName>Polaris Venture Management Co VI, L.L.C.</reportingPersonName>
      <signatureDetails>
        <signature>/s/ Lauren Crockett</signature>
        <title>Lauren Crockett/ Authorized Signatory*</title>
        <date>11/13/2025</date>
      </signatureDetails>
    </signatureInformation>
    <signatureInformation>
      <reportingPersonName>David Barrett</reportingPersonName>
      <signatureDetails>
        <signature>/s/ Lauren Crockett</signature>
        <title>Lauren Crockett/ Attorney-In-Fact</title>
        <date>11/13/2025</date>
      </signatureDetails>
    </signatureInformation>
    <signatureInformation>
      <reportingPersonName>Brian Chee</reportingPersonName>
      <signatureDetails>
        <signature>/s/ Lauren Crockett</signature>
        <title>Lauren Crockett/ Attorney-In-Fact</title>
        <date>11/13/2025</date>
      </signatureDetails>
    </signatureInformation>
    <signatureInformation>
      <reportingPersonName>Jonathan A. Flint</reportingPersonName>
      <signatureDetails>
        <signature>/s/ Lauren Crockett</signature>
        <title>Lauren Crockett/ Attorney-In-Fact</title>
        <date>11/13/2025</date>
      </signatureDetails>
    </signatureInformation>
    <signatureInformation>
      <reportingPersonName>Terrance G. McGuire</reportingPersonName>
      <signatureDetails>
        <signature>/s/ Lauren Crockett</signature>
        <title>Lauren Crockett/ Attorney-In-Fact</title>
        <date>11/13/2025</date>
      </signatureDetails>
    </signatureInformation>
    <signatureInformation>
      <reportingPersonName>Amir Nashat</reportingPersonName>
      <signatureDetails>
        <signature>/s/ Lauren Crockett</signature>
        <title>Lauren Crockett/ Attorney-In-Fact</title>
        <date>11/13/2025</date>
      </signatureDetails>
    </signatureInformation>
    <signatureInformation>
      <reportingPersonName>Bryce Youngren</reportingPersonName>
      <signatureDetails>
        <signature>/s/ Lauren Crockett</signature>
        <title>Lauren Crockett/ Attorney-In-Fact</title>
        <date>11/13/2025</date>
      </signatureDetails>
    </signatureInformation>
    <signatureComments>This Schedule 13G was executed pursuant to a Power of Attorney. Note that copies of the applicable Power of Attorney are already on file with the appropriate agencies.</signatureComments>
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</edgarSubmission>
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</TEXT>
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</SEC-DOCUMENT>
