X0306 4 2017-12-19 0 0001178670 ALNYLAM PHARMACEUTICALS, INC. ALNY 0001180432 MARAGANORE JOHN 300 THIRD STREET THIRD FLOOR CAMBRIDGE MA 02142 1 1 0 0 Chief Executive Officer Common Stock 2017-12-19 4 M 0 1587 63 A 151297 D Common Stock 2960 I by Managed Account Performance Based Stock Option 2016 (right to buy) 42.22 2017-12-20 4 A 0 6250 0 A 2017-12-20 2026-12-20 Common Stock 6250 6250 D Stock Option (right to buy) 63 2017-12-19 4 M 0 1587 0 A 2023-12-18 Common Stock 1587 148413 D The reporting person owns 2,960 shares of ALNY common stock under the ALNY 401(k) plan as a result of the ALNY 401(k) matching contribution program. On December 20, 2016, the reporting person was granted a performance based stock option to purchase shares of ALNY common stock. One quarter of the shares subject to the option will vest upon the achievement of each of four specific clinical development, regulatory or commercial events, as approved by our compensation committee. Effective December 20, 2017, the compensation committee of the Company determined the first performance criterion had been met and the option vested as to one-quarter of the shares. The stock option vests as to 25% of the shares on the 1st anniversary of the date of the stock option grant and as to an additional 6.25% of the shares each successive three month period thereafter /s/ Michael P. Mason, Attorney-in-Fact for John M. Maraganore 2017-12-21