X0306 4 2020-04-07 0 0001178670 ALNYLAM PHARMACEUTICALS, INC. ALNY 0001291963 Greene Barry E 675 WEST KENDALL STREET HENRI A. TERMEER SQUARE CAMBRIDGE MA 02142 0 1 0 0 President Common Stock 2020-04-07 4 A 0 5417 0.0 A 63899 D Common Stock 2020-04-07 4 F 0 1599 104.75 D 62300 D Common Stock 2020-04-07 4 F 0 64 106.65 D 62236 D Common Stock 3003 I by Managed Account Common Stock 3486 I by Trust On February 28, 2019, the reporting person was granted performance-based restricted stock units (PSU) in connection with the 2018 year-end compensation review. This PSU award vests in three equal installments upon the later of one year from the date of grant and the achievement of each of three specific clinical development, regulatory or commercial events. One third of the shares subject to release under the PSU award vested upon the filing by the Company of its fourth NDA with the FDA, as determined by the compensation committee of the Company effective April 7, 2020. Represents shares automatically sold by the Company on behalf of the reporting person pursuant to a mandatory sell-to-cover provision in the PSU award agreement required to cover minimum statutory tax withholding obligations that became due upon the vesting event. Reflects shares of ALNY common stock acquired by the reporting person under the ALNY 401(k) plan as a result of the ALNY 401(k) matching contribution program. Represents remaining shares held by the "Barry E. Greene Qualified Annuity Interest Trust" (GRAT), of which Barry E. Greene is the sole Trustee By: /s/ Mary Beth DeLena, Attorney-in-Fact For: Barrey E. Greene 2020-04-09