Sec Form 4 Filing - Vaishnaw Akshay @ ALNYLAM PHARMACEUTICALS, INC. - 2023-08-03

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person Vaishnaw Akshay 2. Issuer Name and Ticker or Trading Symbol ALNYLAM PHARMACEUTICALS, INC. [ ALNY] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner X __ Officer (give title below) _____ Other (specify below) President (Last) (First) (Middle) 675 WEST KENDALL STREET, HENRI A. TERMEER SQUARE 3. Date of Earliest Transaction (MM/DD/YY) 08/03/2023 (Street) CAMBRIDGE, MA02142 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 08/03/2023 A( 1 ) 5,082 A $ 0 22,972 D Common Stock 08/03/2023 A( 2 ) 3,859 A $ 0 26,831 D Common Stock 08/04/2023 S( 3 ) 771 D $ 184.7 ( 4 ) 26,060 D Common Stock 08/04/2023 S( 3 ) 1,869 D $ 185.54 ( 5 ) 24,191 D Common Stock 08/04/2023 S( 3 ) 1,107 D $ 186.39 ( 6 ) 23,084 D Common Stock 08/04/2023 S( 3 ) 101 D $ 187.37 ( 7 ) 22,983 D Common Stock 08/04/2023 S ( 8 ) 17 D $ 188.4 ( 9 ) 22,966 D Common Stock 08/04/2023 S( 3 ) 192 D $ 189.31 22,774 D Common Stock 515 I by Managed Account ( 10 )

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Vaishnaw Akshay 675 WEST KENDALL STREET HENRI A. TERMEER SQUARE CAMBRIDGE, MA02142 President Signatures By: Stephen Hall, Attorney-in-Fact For: Akshay K. Vaishnaw 08/07/2023 Signature of Reporting Person Date

Explanation of Responses:

( 1 )On February 26, 2020, the reporting person was granted performance-based stock units (PSUs) in connection with the issuer 2019 year-end compensation review. The PSUs vest in separate installments based on the achievement of three specified performance measures as determined by the People, Culture and Compensation Committee of the issuer Board of Directors. The shares reported were issued to the reporting person upon vesting of one-third of the PSUs based on achievement of a corresponding performance measure relating to the issuer public reporting of the achievement of the first $2.5 billion in cumulative net product revenues determined in accordance with GAAP based solely upon the sales by the Company, including its affiliates and ex-U.S. distributions, of products discovered/developed by the Company. ( 2 )On February 24, 2021, the reporting person was granted performance-based stock units (PSUs) in connection with the issuer 2020 year-end compensation review. The PSUs vest in separate installments based on the achievement of four specified performance measures as determined by the People, Culture and Compensation Committee of the issuer Board of Directors. The shares reported were issued to the reporting person upon vesting of one-quarter of the PSUs based on achievement of a corresponding performance measure relating to the issuer public reporting of the achievement of the first $2.5 billion in cumulative net product revenues determined in accordance with GAAP based solely upon the sales by the Company, including its affiliates and ex-U.S. distributions, of products discovered/developed by the Company. ( 3 )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 reported in this form. ( 4 )The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $184.01 to $185.01. 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. ( 5 )The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $185.02 to $186.02. 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. ( 6 )The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $186.03 to $187.02. 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. ( 7 )The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $187.04 to $188.04. 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. ( 8 )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 event. ( 9 )The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $188.14 to $189.05. 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. ( 10 )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.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

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