Alector, Inc.

Item 5. Other Information

(a) None.

(b) None.

(c) During our last fiscal quarter, the following officers and directors adopted or terminated a “Rule 10b5-1 trading arrangement” as defined in Regulation S-K Item 408, as follows:

On May 27, 2025, Paula Hammond, a member of the Company’s Board of Directors, adopted a Rule 10b5-1 trading plan. Dr. Hammond’s plan provides for the sale from time to time of an aggregate of up to 14,000 shares of the Company’s common stock. Sales of the shares of the Company’s common stock set forth in Dr. Hammond's trading plan, if any, will be made at or above specified market prices. The trading plan will expire on May 26, 2026, or earlier if all transactions under the trading plan are completed. Dr. Hammond’s trading plan was entered into during an open insider trading window and is intended to satisfy the affirmative defense in Rule 10b5-1(c) under the Exchange Act and the Company’s policies regarding insider transactions.

On June 20, 2025, Marc Grasso, the Company’s former Chief Financial Officer, terminated a Rule 10b5-1 trading plan that was originally adopted on September 13, 2024 and provided for (i) the exercise of vested stock options to purchase an aggregate of up to 75,501 shares of the Company’s common stock, and (ii) the sale from time to time of an aggregate of up to 84,357 shares of the Company’s common stock. The terminated plan would have expired on September 13, 2025 had it not been terminated.

Other than as disclosed above, during our last fiscal quarter, no other officer or director (as defined in Rule 16a-1(f) under the Exchange Act)adopted orterminated a “Rule 10b5-1 trading arrangement” or a "non-Rule 10b5-1 trading arrangement" (each as defined in Item 408 of Regulation S-K).