On March 15, 2024, Terry McGuire informed Alector, Inc. (the ?Company?) of his resignation as a member of the Board of Directors (the ?Board?) and all committees and subcommittees thereof, effective close of business March 20, 2024. Mr. McGuire is retiring from the Board for personal reasons, after many years of dedicated service, and not as a result of any disagreement with the Company on any matter relating to the Company?s operations, policies, or practices. On March 19, 2024 (the ?Appointment Date?), each of Errol De Souza, Ph.D. and Mark Altmeyer was appointed to the Board.

Dr. De Souza will serve as a Class II director, with a term expiring at the Company?s 2026 annual meeting of stockholders, and Mr. Altmeyer will serve as a Class III director, with a term expiring at the Company?s 2024 annual meeting of stockholders. Upon joining the Board, Dr. De Souza is appointed to the Compensation and Audit Committees of the Board. Mr. Altmeyer is appointed to the Audit and Corporate Governance and Nominating Committees of the Board.

Upon the effectiveness of the appointment of Dr. De Souza and Mr. Altmeyer, the size of the Board was increased from eight to ten directors. The size of the Board was subsequently reduced to nine directors, effective immediately following the effectiveness of Mr. McGuire?s resignation.