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

Rhea-AI Filing Summary

Tolga Tanguler, EVP & Chief Commercial Officer of Alnylam Pharmaceuticals (ALNY), reported changes in beneficial ownership related to a performance-based award and subsequent sell-to-cover transactions. On 08/15/2025 Tanguler received 2,851 shares that vested from a performance-based stock unit granted on 03/01/2024 after achievement of a clinical milestone. Following the vesting, a series of automatic sales executed on 08/18/2025 sold varying blocks of shares to satisfy statutory tax withholding, with weighted-average sale prices reported in ranges from $447.53 up to $456.00 per share. After these transactions Tanguler beneficially owned 29,466 shares.

Positive

• Performance-based award vested: 2,851 shares issued upon achievement of a clinical milestone as determined by the compensation committee.
• Transparent disclosures: Form 4 provides weighted-average price ranges for multiple sell-to-cover transactions and explains the tax-withholding mechanism.

Negative

• Reduction in holdings: Multiple sell-to-cover sales on 08/18/2025 reduced beneficial ownership from 30,862 to 29,466 shares.
• Monetary details omitted: The filing does not state total gross proceeds or specific tax withholding amounts associated with the sales.

Insights

Financial Analyst

TL;DR: Executive received vested PSUs and immediately triggered sell-to-cover sales, leaving modest net share ownership change.

The filing shows a performance-based stock unit vested for 2,851 shares on 08/15/2025 due to a clinical milestone, consistent with incentive compensation tied to milestones. The mandatory sell-to-cover sales on 08/18/2025 reduced the reporting persons holdings through multiple transactions at weighted-average prices across $447.53 to $456.00 per share. The filing does not disclose total dollar proceeds or tax amounts withheld. Impact is routine for executive compensation and is not individually material to company capitalization given the reported post-transaction holding of 29,466 shares.

Corporate Governance Expert

TL;DR: Disclosure aligns with Section 16 reporting and shows use of standard sell-to-cover mechanics after PSU vesting.

The statement of changes in beneficial ownership provides the required transparency about grant vesting and automatic sales to cover tax obligations. The explanation clarifies the PSU grant date, performance condition, and committee determination of milestone achievement, which supports governance best practices for performance-based awards. No amendment or unusual trading pattern is disclosed. All transactions appear reported within the timelines and include weighted-average price ranges for the multiple sales.

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^*

Tanguler Tolga

(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 Commercial 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)		2,851	A	$0.0	30,862	D
Common Stock	08/18/2025		S(2)		39	D	$447.98(3)	30,823	D
Common Stock	08/18/2025		S(2)		90	D	$449.92(4)	30,733	D
Common Stock	08/18/2025		S(2)		39	D	$450.92(5)	30,694	D
Common Stock	08/18/2025		S(2)		103	D	$451.99(6)	30,591	D
Common Stock	08/18/2025		S(2)		329	D	$452.96(7)	30,262	D
Common Stock	08/18/2025		S(2)		543	D	$454.04(8)	29,719	D
Common Stock	08/18/2025		S(2)		241	D	$454.84(9)	29,478	D
Common Stock	08/18/2025		S(2)		12	D	$455.82(10)	29,466	D

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.

	By: Brett Budzinski, Attorney-in-Fact For: Tolga Tanguler	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.
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FAQ

What transaction did Tolga Tanguler report on Form 4 for ALNY?

On 08/15/2025 Tanguler reported vesting of 2,851 shares from a performance-based stock unit; subsequent sell-to-cover sales occurred on 08/18/2025.

Why were shares sold after the PSU vested for ALNY executive Tolga Tanguler?

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

How many ALNY shares did Tolga Tanguler own after the reported transactions?

Following the vesting and sales, Tanguler beneficially owned 29,466 shares according to the Form 4.

What price ranges were reported for the ALNY sell-to-cover transactions?

Weighted-average sale price ranges reported span approximately $447.53 to $456.00 per share across multiple transactions on 08/18/2025.

When was the performance-based award originally granted to Tolga Tanguler?

The PSU was granted on 03/01/2024 under the 2018 Stock Incentive Plan as stated in the Form 4 explanation.