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

Rhea-AI Filing Summary

Kevin J. Fitzgerald, CSO & EVP, Head of Research at Alnylam Pharmaceuticals (ALNY), reported insider transactions tied to vested performance-based awards. On 08/15/2025 he was issued 2,851 shares following vesting of 30% of a performance-based stock unit granted 03/01/2024 after a clinical milestone determination. On 08/18/2025 he sold a total of 1,396 shares via multiple transactions under a mandatory sell-to-cover provision to satisfy tax withholding, at weighted sale prices ranging roughly between $447.53 and $456.00 per share. Following these transactions he beneficially owned 23,515 shares directly and an additional 537 shares indirectly through a managed account.

Positive

• Performance milestone achieved: 2,851 shares issued upon vesting of 30% of a PSU after a clinical milestone determination on 08/15/2025
• Significant continued ownership: Reporting person retains 23,515 shares directly and 537 shares indirectly, maintaining alignment with shareholders

Negative

• Insider share sales: 1,396 shares sold on 08/18/2025 across multiple tranches at weighted prices roughly $447.53–$456.00, reducing direct holdings
• Tax-driven liquidity: Sales executed under mandatory sell-to-cover provision, indicating proceeds used for withholding obligations (reduces vested-share retention)

Insights

Corporate Governance Expert

TL;DR: Insider received PSU shares after a clinical milestone and executed sell-to-cover transactions for tax obligations; activity appears administrative rather than a directional signal.

The reporting person was granted a performance-based stock unit that vested in part upon a clinical milestone, triggering issuance of 2,851 shares on 08/15/2025. The subsequent sales on 08/18/2025 (totaling 1,396 shares) were executed under a mandatory sell-to-cover provision, which is a routine mechanism to satisfy tax withholding on vesting events. The filings clearly disclose weighted-average price ranges for the multiple sale tranches and show continued meaningful ownership (23,515 direct shares plus 537 indirect). From a governance perspective, this is a common post-vesting liquidity action and is not, by itself, evidence of change in insider conviction.

Securities Analyst

TL;DR: The vesting reflects achievement of a corporate clinical milestone; sell-to-cover proceeds reduced share count modestly while leaving substantial insider ownership.

The 2,851-share issuance indicates a performance metric was met as of the committee determination on 08/15/2025. Sales on 08/18/2025 aggregated 1,396 shares across multiple price bands (weighted averages reported per tranche between approx. $447.53 and $456.00). Post-transactions direct beneficial ownership remained at 23,515 shares, with 537 shares held indirectly in a managed account, preserving insider alignment with shareholders. The pattern—vesting followed by sell-to-cover—aligns with compensation tax mechanics rather than opportunistic cashing out.

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^*

Fitzgerald Kevin Joseph

(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)
	CSO & EVP, Head of Research

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)		2,851	A	$0.0	24,115	D
Common Stock	08/18/2025		S(2)		39	D	$447.98(3)	24,076	D
Common Stock	08/18/2025		S(2)		90	D	$449.92(4)	23,986	D
Common Stock	08/18/2025		S(2)		39	D	$450.92(5)	23,947	D
Common Stock	08/18/2025		S(2)		103	D	$451.99(6)	23,844	D
Common Stock	08/18/2025		S(2)		329	D	$452.96(7)	23,515	D
Common Stock	08/18/2025		S(2)		543	D	$454.04(8)	22,972	D
Common Stock	08/18/2025		S(2)		241	D	$454.84(9)	22,731	D
Common Stock	08/18/2025		S(2)		12	D	$455.82(10)	22,719	D
Common Stock								537	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: Kevin Fitzgerald	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 insider transactions did Kevin Fitzgerald report for ALNY on Form 4?

He was issued 2,851 shares on 08/15/2025 upon vesting of 30% of a PSU and sold 1,396 shares on 08/18/2025 under a sell-to-cover provision.

Why were shares sold by the reporting person after vesting?

Sales were mandatory sell-to-cover transactions required to satisfy minimum statutory tax withholding obligations that became due upon vesting.

How many shares does Kevin Fitzgerald own after these transactions?

He beneficially owns 23,515 shares directly and 537 shares indirectly through a managed account following the reported transactions.

When was the PSU originally granted that led to the issuance?

The PSU was granted on March 1, 2024, with 30% vesting reported upon achievement of a clinical milestone.

What price range did the reported sales occur at?

Weighted-average sale prices for the tranches range approximately from $447.53 to $456.00, with specific tranche-weighted prices disclosed per sale in the filing.