X0508 4 2025-05-08 0 0001178670 ALNYLAM PHARMACEUTICALS, INC. ALNY 0001661908 Sigal Charles Elliott 675 WEST KENDALL STREET HENRI A. TERMEER SQUARE CAMBRIDGE MA 02142 1 0 0 0 0 Common Stock 2025-05-08 4 A 0 775 0.0 A 775 D Common Stock 2000 I by Trust Stock Option (right to buy) 258.35 2025-05-08 4 A 0 1558 0.0 A 2026-05-08 2035-05-08 Common Stock 1558 1558 D These shares are represented by restricted stock units (RSUs) granted under the Amended and Restated 2018 Stock Incentive Plan. Each RSU represents a contingent right to receive one share of common stock. The RSUs will vest in full upon the earlier of the first anniversary of the grant date and the date of any earlier retirement or resignation of the Reporting Person, provided such date of retirement or resignation occurs no more than 90 days prior to the first anniversary of the grant date. Shares held by Sigal Family Investments, LLC, of which the reporting person is Managing Member. The stock option vests in full upon the earlier of the first anniversary of the grant date and the date of any earlier retirement or resignation of the Reporting Person, provided such date of retirement or resignation occurs no more than 90 days prior to the first anniversary of the grant date. By: Brett Budzinski, Attorney-in-Fact For: Charles Elliott Sigal 2025-05-12