Arnon Rosenthal - 02 Sep 2025 Form 4 Insider Report for Alector, Inc. (ALEC)

Role: Chief Executive Officer, Director
Signature: /s/ Grace Wong-Sarad, by power of attorney
Issuer symbol: ALEC
Transactions as of: 02 Sep 2025
Net transactions value: -$128,740
Form type: 4
Filing time: 04 Sep 2025, 16:27:49 UTC
Previous filing: 01 Jul 2025
Next filing: 12 Nov 2025
SEC: View on sec.gov

Reporting Owners (1)

Name	Relationship	Address	Signature	Signature date	CIK
Rosenthal Arnon	Chief Executive Officer, Director	C/O ALECTOR, INC., 131 OYSTER POINT BLVD, SUITE 600, SOUTH SAN FRANCISCO	/s/ Grace Wong-Sarad, by power of attorney	04 Sep 2025	0001757770

Transactions Table

Type	Sym	Class	Transaction	Value $	Shares	Change %	* Price $	Shares After	Date	Ownership	Footnotes
transaction	ALEC	Common Stock	Sale	$128,740	-51,562	-2.1%	$2.50	2,350,220	02 Sep 2025	Direct	F1, F2, F3
holding	ALEC	Common Stock						1,972,875	02 Sep 2025	See footnote	F4
holding	ALEC	Common Stock						652,500	02 Sep 2025	See footnote	F5
holding	ALEC	Common Stock						652,500	02 Sep 2025	See footnote	F6
holding	ALEC	Common Stock						652,500	02 Sep 2025	See footnote	F7

* An asterisk sign (*) next to the price indicates that the price is likely invalid.

Explanation of Responses:

Id	Content
F1	The reported shares were sold to satisfy the reporting person's tax obligations in connection with the vesting of restricted stock units, or RSUs.
F2	The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $2.30 to $2.59. Full information regarding the number of shares sold at each separate price can be furnished to the SEC staff, the issuer, or any security holder of the issuer upon request.
F3	The reported amount excludes 150,000 shares previously reported as performance share units, or PSUs. Because the performance metrics were not attained during the PSU measurement period, these PSUs were forfeited on May 6, 2025.
F4	The reported securities are held directly by The Rosenthal Family Revocable Trust Dated November 4, 1994, as restated on June 9, 1999, for which the Reporting Person serves as trustee.
F5	The reported securities are held directly by the Adi Rosenthal 2007 Trust dated March 27, 2007, for which the Reporting Person serves as trustee.
F6	The reported securities are held directly by the Noam Rosenthal 2007 Trust dated March 27, 2007, for which the Reporting Person serves as trustee.
F7	The reported securities are held directly by the Shani Rosenthal 2007 Trust dated March 27, 2007, for which the Reporting Person serves as trustee.