Alnylam CEO Greenstreet logs PSU vesting and sales to cover taxes

Rhea-AI Filing Summary

Alnylam Pharmaceuticals (ALNY) CEO Yvonne Greenstreet reported PSU-related share activity. On 10/01/2025, she acquired 3,860 and 14,252 shares at $0 upon PSU vesting tied to the initiation of a Phase 3 clinical study, as determined by the PC&C Committee. On 10/02/2025, the Company executed sell-to-cover transactions to satisfy tax withholding, with multiple weighted-average sales ranging from $446.53 to $457.64. Following these transactions, she held 65,409 shares directly and 407 shares indirectly by a managed account.

Insights

Executive Compensation and Governance Analyst

PSU milestones vested after a Phase 3 initiation; related tax sell-to-cover sales; CEO ownership updated.

The CEO of ALNYLAM PHARMACEUTICALS, INC. reported PSU vesting tied to operational milestones. On 10/01/2025, one-quarter of a 2021 PSU and 30% of a 2024 PSU vested upon the issuer publicly reporting initiation of a Phase 3 study in a prevalent indication. That yielded 3,860 and 14,252 shares, respectively, at no cost.

On 10/02/2025, the company executed multiple automatic sales solely to cover minimum tax withholding on those vestings, with weighted average prices across specified ranges, and no discretionary sales indicated. Following these transactions, direct beneficial ownership stood at 65,409 shares, with 407 shares held indirectly via a managed 401(k) account.

This filing links equity vesting to a disclosed Phase 3 initiation milestone as determined by the board’s PC&C Committee on 10/01/2025. Items to watch include any future PSU tranches tied to further performance measures and subsequent sell-to-cover activity around settlement dates.

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

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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^*

Greenstreet Yvonne

(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)

X	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	Chief Executive 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)		3,860	A	$0.0	60,081	D
Common Stock	10/01/2025		A(2)		14,252	A	$0.0	74,333	D
Common Stock	10/02/2025		S(3)		350	D	$446.53(4)	73,983	D
Common Stock	10/02/2025		S(3)		171	D	$447.92(5)	73,812	D
Common Stock	10/02/2025		S(3)		548	D	$448.77(6)	73,264	D
Common Stock	10/02/2025		S(3)		758	D	$449.79(7)	72,506	D
Common Stock	10/02/2025		S(3)		1,642	D	$450.81(8)	70,864	D
Common Stock	10/02/2025		S(3)		1,010	D	$451.86(9)	69,854	D
Common Stock	10/02/2025		S(3)		2,029	D	$452.69(10)	67,825	D
Common Stock	10/02/2025		S(3)		999	D	$453.77(11)	66,826	D
Common Stock	10/02/2025		S(3)		741	D	$454.84(12)	66,085	D
Common Stock	10/02/2025		S(3)		221	D	$455.82(13)	65,864	D
Common Stock	10/02/2025		S(3)		446	D	$457.43	65,418	D
Common Stock	10/02/2025		S(3)		9	D	$457.64	65,409	D
Common Stock								407	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: Yvonne Greenstreet	10/03/2025
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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FAQ

What insider activity did ALNY's CEO report?

She reported PSU vesting on 10/01/2025 and sell-to-cover sales on 10/02/2025 to satisfy tax withholding.

How many ALNY shares were acquired from PSU vesting?

She acquired 3,860 shares and 14,252 shares at $0.0 upon vesting tied to performance milestones.

What were the ALNY share sale prices for tax withholding?

Weighted-average sales occurred in multiple tranches with averages from $446.53 up to $457.64, each supported by disclosed price ranges.

What is the CEO’s ALNY share ownership after these transactions?

She held 65,409 shares directly and 407 shares indirectly via a managed account.

Why were ALNY shares sold on 10/02/2025?

They were mandatory sell-to-cover sales to cover minimum statutory tax withholding arising from PSU vesting.

What performance condition triggered PSU vesting at ALNY?

The issuer publicly reported initiation of a Phase 3 clinical study in a prevalent indication, as determined by the PC&C Committee on 10/01/2025.

Were any derivative securities reported?

No derivative securities were listed in Table II for this report.