ALNYLAM PHARMACEUTICALS, INC.

Adoption of 10b5-1 Trading Plans by Our Officers and Directors

During our fiscal quarter ended September 30, 2026, one of our officers entered into a written plan for the sale of our securities that is intended to satisfy the conditions specified in Rule 10b5-1(c) under the Exchange Act for an affirmative defense against liability for trading in securities on the basis of material nonpublic information. We refer to this written plan as a “Rule 10b5-1 trading plan.” We describe the material terms of the Rule 10b5-1 trading plan below.

Tolga Tanguler, Chief Commercialization Officer

On August 24, 2026, Tolga Tanguler, our Chief Commercialization Officer, entered into a Rule 10b5-1 trading plan that provides that Mr. Tanguler, acting through a broker, may sell up to an aggregate of 22,438 shares of our common stock received upon the settlement of awards granted to Mr. Tanguler as equity incentive compensation, subject to adjustments for stock splits, stock combinations, stock dividends and other similar changes to our common stock. Sales of shares under the plan may only occur from November 23, 2026 to August 6, 2027. The plan is scheduled to terminate on August 6, 2027, subject to earlier termination upon the sale of all shares subject to the plan, upon termination by Mr. Tanguler or the broker, or as otherwise provided in the plan.