[Form 4] ALNYLAM PHARMACEUTICALS, INC. Insider Trading Activity

Rhea-AI Filing Summary

Jeffrey V. Poulton, EVP and Chief Financial Officer of Alnylam Pharmaceuticals (ALNY), reported equity changes tied to performance-based stock units (PSUs) that vested following corporate milestones. On 10/01/2025 the reporting person received 3,108 shares from a 2/24/2021 PSU tranche and 4,644 shares from a 3/01/2024 PSU tranche after the issuer publicly reported initiation of a Phase 3 clinical study in a prevalent indication, as determined by the People, Culture and Compensation Committee.

The company automatically sold 3,821 shares on 10/02/2025 under a mandatory sell-to-cover provision to satisfy statutory tax withholding, at weighted-average prices ranging roughly from $446.19 to $456.09 across multiple transactions. After these transactions the reporting person beneficially owned 54,052 shares directly and 57 shares indirectly via a managed account; 57 additional shares were acquired under the issuer 401(k) matching program.

Positive

• 7,752 PSU shares vested due to a corporate milestone (initiation of a Phase 3 study)
• Vesting was approved by the issuer's People, Culture and Compensation Committee, showing governance oversight
• 57 shares acquired via the issuer 401(k) matching program

Negative

• 3,821 shares were sold under a mandatory sell-to-cover on 10/02/2025, reducing direct holdings
• Sales executed at weighted-average prices ranging from approximately $446.19 to $456.09

Insights

Compensation Analyst

Vesting of PSUs tied to a Phase 3 initiation led to issuance of 7,752 shares and partial sell-to-cover of 3,821 shares.

The filing confirms that two separate PSU awards (granted 2/24/2021 and 3/1/2024) vested on 10/01/2025 due to a disclosed clinical milestone: initiation of a Phase 3 study. Issuance of 3,108 and 4,644 shares reflects performance-based compensation converting to equity.

The 3,821 shares sold on 10/02/2025 were executed under a mandatory sell-to-cover to satisfy tax withholding; weighted-average sale prices reported fall between $446.19 and $456.09. This is a routine mechanics-driven disposition tied to vesting rather than an independent open-market decision documented here.

Corporate Governance Specialist

Disclosure links a clinical milestone to executive equity vesting and shows post-transaction ownership of 54,052 direct shares.

The report explicitly ties vesting to a corporate milestone approved by the People, Culture and Compensation Committee, indicating governance oversight of performance conditions. Post-transaction beneficial ownership is reported as 54,052 direct and 57 indirect shares, with an additional 57 shares from a 401(k) match.

The filing is material as it documents milestone-driven equity issuance; however, it contains no other corporate actions, loans, or derivative activity requiring further governance scrutiny in this Form 4.

SEC Form 4

FORM 4

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
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

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

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Poulton Jeffrey V.

(Last) (First) (Middle)

675 WEST KENDALL STREET

HENRI A. TERMEER SQUARE

(Street)

CAMBRIDGE MA 02142

(City) (State) (Zip)

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)
	EVP, Chief Financial Officer

3. Date of Earliest Transaction (Month/Day/Year)
10/01/2025

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	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	10/01/2025		A(1)		3,108	A	$0.0	53,229	D
Common Stock	10/01/2025		A(2)		4,644	A	$0.0	57,873	D
Common Stock	10/02/2025		S(3)		150	D	$446.53(4)	57,723	D
Common Stock	10/02/2025		S(3)		73	D	$447.92(5)	57,650	D
Common Stock	10/02/2025		S(3)		234	D	$448.77(6)	57,416	D
Common Stock	10/02/2025		S(3)		324	D	$449.79(7)	57,092	D
Common Stock	10/02/2025		S(3)		704	D	$450.81(8)	56,388	D
Common Stock	10/02/2025		S(3)		432	D	$451.86(9)	55,956	D
Common Stock	10/02/2025		S(3)		869	D	$452.69(10)	55,087	D
Common Stock	10/02/2025		S(3)		428	D	$453.77(11)	54,659	D
Common Stock	10/02/2025		S(3)		317	D	$454.84(12)	54,342	D
Common Stock	10/02/2025		S(3)		95	D	$455.82(13)	54,247	D
Common Stock	10/02/2025		S(3)		191	D	$457.43	54,056	D
Common Stock	10/02/2025		S(3)		4	D	$457.64	54,052	D
Common Stock								57	I	by Managed Account(14)

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 (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	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 (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (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: 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

Explanation of Responses:

1. On February 24, 2021, the reporting person was granted a performance-based stock unit (PSU) under the 2018 Stock Incentive Plan. The shares subject to the PSU vest based on the achievement of four specified performance measures. The shares reported were issued to the reporting person upon vesting of one-quarter of the shares subject to the PSU based on the issuer publicly reporting the initiation of a Phase 3 clinical study of an RNAi therapeutic in development to treat a prevalent disease, as determined by the People, Culture and Compensation (PC&C) Committee of the Issuer Board of Directors on October 1, 2025.

2. On March 1, 2024, the reporting person was granted a PSU under the 2018 Stock Incentive Plan. The shares subject to the PSU vest based on the achievement of three specified performance measures. The shares reported were issued to the reporting person upon vesting of thirty (30) percent of the shares subject to the PSU based on the issuer publicly reporting the initiation of a Phase 3 clinical study in a prevalent indication, as determined by the PC&C Committee on October 1, 2025.

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 tranches of PSUs granted to the reporting person on February 24, 2021 and March 1, 2024.

4. The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $446.19 to $447.19. 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.

5. The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $447.21 to $448.21. 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 $448.25 to $449.24. 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.

7. The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $449.26 to $450.26. 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. The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $450.29 to $451.29. 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.

9. The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $451.31 to $452.31. 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.

10. The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $452.33 to $453.31. 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.

11. The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $453.37 to $454.37. 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.

12. The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $454.38 to $455.34. 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.

13. The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $455.42 to $456.09. 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.

14. 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.

	By: Brett Budzinski, Attorney-in-Fact For: Jeffrey V. Poulton	10/03/2025
	** Signature of Reporting Person	Date
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).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
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FAQ

What triggered the vesting reported on the ALNY Form 4?

Vesting was triggered by the issuer publicly reporting the initiation of a Phase 3 clinical study, as determined by the People, Culture and Compensation Committee on 10/01/2025.

How many shares did ALNY CFO Jeffrey Poulton receive from PSUs?

The reporting person received 3,108 shares from a 2/24/2021 PSU and 4,644 shares from a 3/01/2024 PSU, totaling 7,752 shares issued upon vesting.

Why were shares sold after vesting on the ALNY Form 4?

The company automatically sold 3,821 shares pursuant to a mandatory sell-to-cover provision in the award agreements to satisfy statutory tax withholding obligations.

At what prices were the shares sold?

Sales occurred at weighted-average prices reported within ranges from about $446.19 to $456.09 across multiple transactions on 10/02/2025.

What is Jeffrey Poulton's beneficial ownership after these transactions?

Following the transactions the reporting person beneficially owned 54,052 shares directly and 57 shares indirectly via a managed account.