[Form 4] Alnylam Pharmaceuticals, Inc. Insider Trading Activity

Rhea-AI Filing Summary

Jeffrey V. Poulton, EVP and Chief Financial Officer of Alnylam Pharmaceuticals (ALNY), received and sold shares following the vesting of performance-based stock units. A PSU tranche vested on 08/15/2025 after the Compensation Committee determined a clinical milestone was achieved, resulting in the issuance of 4,644 shares to Mr. Poulton. Between 08/18/2025 the reporting person had multiple automatic sales of shares to satisfy mandatory tax-withholding obligations at weighted-average prices in the $447.53–$456.00 range. The filing also notes 57 shares held indirectly via a managed account from the company 401(k) match.

Positive

• Performance-based award vested after a clinical milestone determination by the People, Culture and Compensation Committee, indicating achievement of a specified corporate objective
• Clear disclosure of weighted-average sale price ranges for the automatic sell-to-cover transactions and explanation that sales were to satisfy tax-withholding obligations
• 401(k) match noted with 57 shares held indirectly, showing participation in the company plan

Negative

• Shares were sold following vesting (multiple automatic sell-to-cover transactions on 08/18/2025), which reduced the reporting person’s direct share holdings
• Significant sale price range spans approximately $447.53 to $456.00, exposing proceeds to short-term market price variance

Insights

Securities Analyst

TL;DR: Insider received PSU shares after a clinical milestone and executed sell-to-cover transactions to meet tax obligations; impact appears routine.

The transaction reflects issuance of an earned performance-based award tied to a clinical milestone, which is positive as a disclosed achievement triggering vesting. The subsequent sales were executed automatically to cover withholding taxes rather than opportunistic market timing disclosed by the filer. The volumes reported are modest relative to executive holdings disclosed on the form and are presented with weighted-average prices across multiple executions. No derivative transactions or additional unusual dispositions were reported.

Corporate Governance Expert

TL;DR: Governance process followed: committee determination, award settlement, and mandatory sell-to-cover per award terms.

The filing documents standard governance steps: committee determination of a milestone, settlement of a PSU tranche, and mandatory sell-to-cover for tax withholding. Disclosure includes price ranges for the sales and notes the 401(k) match contribution. There are no indications of material departures from routine equity compensation administration or of coordinated group filings that would raise governance concerns.

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)
08/15/2025

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	08/15/2025		A(1)		4,644	A	$0.0	52,395	D
Common Stock	08/18/2025		S(2)		63	D	$447.98(3)	52,332	D
Common Stock	08/18/2025		S(2)		147	D	$449.92(4)	52,185	D
Common Stock	08/18/2025		S(2)		63	D	$450.92(5)	52,122	D
Common Stock	08/18/2025		S(2)		168	D	$451.99(6)	51,954	D
Common Stock	08/18/2025		S(2)		536	D	$452.96(7)	51,418	D
Common Stock	08/18/2025		S(2)		886	D	$454.04(8)	50,532	D
Common Stock	08/18/2025		S(2)		392	D	$454.84(9)	50,140	D
Common Stock	08/18/2025		S(2)		19	D	$455.82(10)	50,121	D
Common Stock								57	I	by Managed Account(11)

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 March 1, 2024, 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 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 achievement of a clinical milestone, as determined by The People, Culture and Compensation Committee of the Issuer Board of Directors on August 15, 2025.

2. 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 a tranche of restricted stock units granted to the reporting person on March 1, 2024.

3. The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $447.53 to $448.45. 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.

4. The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $449.21 to $450.16. 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 $450.42 to $451.39. 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 $451.48 to $452.48. 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 $452.49 to $453.49. 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 $453.50 to $454.45. 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 $454.58 to $455.55. 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 $455.65 to $456.00. 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.

11. 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	08/19/2025
	** 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).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.

FAQ

What happened in the ALNY Form 4 filed for Jeffrey V. Poulton?

The report shows a PSU tranche vested on 08/15/2025 (4,644 shares issued) and multiple automatic sell-to-cover sales on 08/18/2025 to cover tax withholding.

Why were shares sold after the PSU vesting in the ALNY filing?

The filing states the shares were automatically sold pursuant to a mandatory sell-to-cover provision required to cover minimum statutory tax withholding obligations.

How many shares were issued upon vesting and how many were sold?

The filing reports 4,644 shares were issued upon vesting; the filing lists multiple sales on 08/18/2025 totaling 2,274 shares sold (per line-item amounts reported).

What prices were the shares sold at in the Form 4?

Weighted-average sales prices are reported across multiple transactions, with ranges provided from $447.53 up to $456.00 depending on the sale tranche.

Does the filing show any derivative transactions for Mr. Poulton?

No derivative securities transactions are reported in Table II; the filing only documents non-derivative common stock issuance and sales.