ALNY · Alnylam Pharmaceuticals, Inc.

The transactions reported on this Form 4 were made pursuant to a Rule 10b5-1(c) trading plan adopted by the reporting person on November 12, 2025. The options exercised by the reporting person were due to expire on June 3, 2026.

The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $298.33 to $299.33. 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 transactions reported on this Form 4 were made pursuant to a Rule 10b5-1(c) trading plan adopted by the reporting person on November 12, 2025. The options exercised by the reporting person were due to expire on June 3, 2026.

The transactions reported on this Form 4 were made pursuant to a Rule 10b5-1(c) trading plan adopted by the reporting person on November 12, 2025. The options exercised by the reporting person were due to expire on June 3, 2026.

The stock option will vest as to one third of the shares on each of the first, second and third anniversaries of the date of grant.

The transactions reported on this Form 4 were made pursuant to a Rule 10b5-1(c) trading plan adopted by the reporting person on November 12, 2025. The options exercised by the reporting person were due to expire on June 3, 2026.

This stock option was fully vested and exercisable as of June 3, 2017.

The transactions reported on this Form 4 were made pursuant to a Rule 10b5-1(c) trading plan adopted by the reporting person on November 12, 2025. The options exercised by the reporting person were due to expire on June 3, 2026.

The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $299.36 to $300.19. 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 transactions reported on this Form 4 were made pursuant to a Rule 10b5-1(c) trading plan adopted by the reporting person on November 12, 2025. The options exercised by the reporting person were due to expire on June 3, 2026.

The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $297.31 to $297.99. 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 transactions reported on this Form 4 were made pursuant to a Rule 10b5-1(c) trading plan adopted by the reporting person on November 12, 2025. The options exercised by the reporting person were due to expire on June 3, 2026.

The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $300.45 to $301.15. 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 stock option 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.

These shares are represented by restricted stock units (RSUs) granted under the Second 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.

These shares are represented by restricted stock units (RSUs) granted under the Second 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.

The stock option 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.

These shares are represented by restricted stock units (RSUs) granted under the Second 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.

These shares are represented by restricted stock units (RSUs) granted under the Second 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.

The stock option 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.

The stock option 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.

The stock option 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.

These shares are represented by restricted stock units (RSUs) granted under the Second 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.

The stock option 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.

The stock option 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.

These shares are represented by restricted stock units (RSUs) granted under the Second 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.

These shares are represented by restricted stock units (RSUs) granted under the Second 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.

These shares are represented by restricted stock units (RSUs) granted under the Second 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.

The stock option 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.

These shares are represented by restricted stock units (RSUs) granted under the Second 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.

The stock option 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.

The options exercised and held by the reporting person were due to expire on June 3, 2026.

The options exercised and held by the reporting person were due to expire on June 3, 2026.

This transaction was made pursuant to a Rule 10b5-1(c) trading plan adopted by the Reporting Person on December 16, 2025.

The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $320.10 to $320.32. 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.

This transaction was made pursuant to a Rule 10b5-1(c) trading plan adopted by the Reporting Person on December 16, 2025.

The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $330.21 to $330.86. 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.

This transaction was made pursuant to a Rule 10b5-1(c) trading plan adopted by the Reporting Person on December 16, 2025.

The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $333.39 to $334.31. 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.

This transaction was made pursuant to a Rule 10b5-1(c) trading plan adopted by the Reporting Person on December 16, 2025.

The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $329.22 to $330.18. 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.

This transaction was made pursuant to a Rule 10b5-1(c) trading plan adopted by the Reporting Person on December 16, 2025.

The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $331.77 to $332.14. 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.

Represents shares automatically sold by the Company on behalf of the reporting person pursuant to a mandatory sell-to-cover provision in the award agreement required to cover minimum statutory tax withholding obligations that became due upon the vesting and settlement of restricted stock units.

The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $321.26 to $322.20. 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.

Represents shares automatically sold by the Company on behalf of the reporting person pursuant to a mandatory sell-to-cover provision in the award agreement required to cover minimum statutory tax withholding obligations that became due upon the vesting and settlement of restricted stock units.

The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $318.09 to $318.83. 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.

Represents shares automatically sold by the Company on behalf of the reporting person pursuant to a mandatory sell-to-cover provision in the award agreement required to cover minimum statutory tax withholding obligations that became due upon the vesting and settlement of restricted stock units.

Represents shares automatically sold by the Company on behalf of the reporting person pursuant to a mandatory sell-to-cover provision in the award agreement required to cover minimum statutory tax withholding obligations that became due upon the vesting and settlement of restricted stock units.

The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $320.21 to $321.11. 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.

Represents shares automatically sold by the Company on behalf of the reporting person pursuant to a mandatory sell-to-cover provision in the award agreement required to cover minimum statutory tax withholding obligations that became due upon the vesting and settlement of restricted stock units.

The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $317.07 to $318.05. 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.

Represents shares automatically sold by the Company on behalf of the reporting person pursuant to a mandatory sell-to-cover provision in the award agreement required to cover minimum statutory tax withholding obligations that became due upon the vesting and settlement of restricted stock units.

The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $316.04 to $317.03. 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.

Represents shares automatically sold by the Company on behalf of the reporting person pursuant to a mandatory sell-to-cover provision in the award agreement required to cover minimum statutory tax withholding obligations that became due upon the vesting and settlement of restricted stock units.

The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $319.19 to $320.10. 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.

Represents shares automatically sold by the Company on behalf of the reporting person pursuant to a mandatory sell-to-cover provision in the award agreement required to cover minimum statutory tax withholding obligations that became due upon the vesting and settlement of restricted stock units.

The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $322.31 to $323.13. 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.

Represents shares automatically sold by the Company on behalf of the reporting person pursuant to a mandatory sell-to-cover provision in the award agreement required to cover minimum statutory tax withholding obligations that became due upon the vesting and settlement of restricted stock units.

The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $323.39 to $324.01. 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.

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 $324.26 to $325.20. 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.

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 $323.09 to $324.08. 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.

This transaction was made pursuant to a Rule 10b5-1(c) trading plan adopted by the Reporting Person on August 14, 2025.

The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $326.01 to $326.40. 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.

This transaction was made pursuant to a Rule 10b5-1(c) trading plan adopted by the Reporting Person on August 14, 2025.

The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $321.43 to $322.00. 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.

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 $325.67 to $326.40. 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.

This transaction was made pursuant to a Rule 10b5-1(c) trading plan adopted by the Reporting Person on August 14, 2025.

The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $322.81 to $323.65. 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.

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 $322.03 to $322.96. 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.