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 September 5, 2025, Grace Wong-Sarad, the Company’s Vice President of Accounting and Principal Accounting Officer, adopted a Rule 10b5-1 trading plan. Ms. Wong-Sarad's plan provides for (i) the exercise of vested stock options to purchase an aggregate of up to 84,315 shares of the Company’s common stock, and (ii) the sale from time to time of an aggregate of up to 161,754 shares of the Company’s common stock. Sales of the shares of the Company’s common stock set forth in Ms. Wong-Sarad's trading plan, if any, will be made at or above specified market prices. The trading plan will expire on October 6, 2026 or earlier if all transactions under the trading plan are completed. Ms. Wong-Sarad’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.

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).