Transaction Details

Footnotes

This transaction was made pursuant to a Rule 10b5-1(c) trading plan adopted by the Reporting Person on November 20, 2025. | The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $328.90 to $329.24. The reporting person will provide to the issuer, any security holder of the issuer or the SEC staff, upon request, information regarding the number of shares sold at each price within the range. | The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $330.08 to $331.05. The reporting person will provide to the issuer, any security holder of the issuer or the SEC staff, upon request, information regarding the number of shares sold at each price within the range. | The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $331.09 to $332.02. The reporting person will provide to the issuer, any security holder of the issuer or the SEC staff, upon request, information regarding the number of shares sold at each price within the range. | The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $332.11 to $333.09. The reporting person will provide to the issuer, any security holder of the issuer or the SEC staff, upon request, information regarding the number of shares sold at each price within the range. | Reflects shares of ALNY common stock acquired by the Reporting Person under the issuer 401(k) plan as a result of the issuer 401(k) matching contribution program. | Represents shares held in trust, of which the Reporting Persons spouse is co-trustee. The Reporting Person disclaims beneficial ownership of these shares, and the filing of this report is not an admission that the Reporting Person is the beneficial owner of these securities for purposes of Section 16 or for any other purpose. | 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. | On February 27, 2023, the reporting person was granted 5,724 restricted stock units that vest ratably on each of the first, second and third anniversaries of the Grant Date. On February 27, 2026, the third and final tranche of restricted stock units from the February 27, 2023 grant vested and was released, as reported on this Form 4. | The restricted stock units vest ratably in three installments, with one third vesting on each of the first, second and third anniversaries of the grant date.