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

Rhea-AI Filing Summary

Alnylam Pharmaceuticals (ALNY) executive Tolga Tanguler, EVP and Chief Commercial Officer, reported equity activity on a Form 4. On 10/01/2025, 2,851 common shares were acquired at $0.00 upon vesting of performance-based stock units tied to the initiation of a Phase 3 clinical study, as determined by the Board’s People, Culture and Compensation Committee.

On 10/02/2025, shares were automatically sold by the company under a mandatory sell-to-cover provision to satisfy tax withholding, executed in multiple trades with weighted average prices ranging from $446.19 to $457.64. Following these transactions, the reporting person beneficially owned 27,438 shares directly.

Insights

Biotech Equity Analyst

Executive PSU vesting confirms a Phase 3 initiation milestone; sales were tax sell-to-cover, not discretionary selling.

ALNY’s EVP, Chief Commercial Officer reported vesting of 2,851 PSUs at $0 on 10/01/2025, raising holdings to 28,843 shares before related tax sales. The vesting was triggered by a committee-confirmed performance event: the company had publicly reported initiation of a Phase 3 clinical study in a prevalent indication on that date. Multiple small sales totaling 1,405 shares on 10/02/2025 were executed under a mandatory sell-to-cover provision to satisfy minimum tax withholding, leaving 27,438 shares directly owned.

This Form 4 signals two things: (i) operational progress sufficient to meet a performance condition, and (ii) routine mechanics of equity compensation. The sale prices were reported as weighted averages across disclosed ranges; they reflect withholding mechanics rather than elective liquidation. The filing does not indicate any derivative transactions.

Items to watch: future vesting tied to the remaining performance measures under the 03/01/2024 PSU grant, and any additional confirmations of clinical milestones following the 10/01/2025 Phase 3 initiation. Time horizon: near-to-medium term as subsequent tranches potentially vest upon meeting specified conditions.

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
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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^*

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)
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)		2,851	A	$0.0	28,843	D
Common Stock	10/02/2025		S(2)		55	D	$446.53(3)	28,788	D
Common Stock	10/02/2025		S(2)		27	D	$447.92(4)	28,761	D
Common Stock	10/02/2025		S(2)		86	D	$448.77(5)	28,675	D
Common Stock	10/02/2025		S(2)		119	D	$449.79(6)	28,556	D
Common Stock	10/02/2025		S(2)		260	D	$450.81(7)	28,296	D
Common Stock	10/02/2025		S(2)		159	D	$451.86(8)	28,137	D
Common Stock	10/02/2025		S(2)		319	D	$452.69(9)	27,818	D
Common Stock	10/02/2025		S(2)		157	D	$453.77(10)	27,661	D
Common Stock	10/02/2025		S(2)		117	D	$454.84(11)	27,544	D
Common Stock	10/02/2025		S(2)		35	D	$455.82(12)	27,509	D
Common Stock	10/02/2025		S(2)		70	D	$457.43	27,439	D
Common Stock	10/02/2025		S(2)		1	D	$457.64	27,438	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 issuer publicly reporting the initiation of a Phase 3 clinical study in a prevalent indication, as determined by the People, Culture and Compensation Committee of the Issuer Board of Directors on October 1, 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 PSUs 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 $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.

4. 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.

5. 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.

6. 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.

7. 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.

8. 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.

9. 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.

10. 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.

11. 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.

12. 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.

	By: Brett Budzinski, Attorney-in-Fact For: Tolga Tanguler	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).
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 did ALNY’s EVP report on Form 4?

A vesting of 2,851 performance-based shares on 10/01/2025 and automatic sell-to-cover sales on 10/02/2025 to cover taxes.

Why did the ALNY shares sell on 10/02/2025?

They were sold under a mandatory sell-to-cover provision to satisfy minimum statutory tax withholding from the PSU vesting.

What price range were ALNY shares sold at for tax withholding?

Weighted average sales occurred across multiple transactions from $446.19 to $457.64.

How many ALNY shares does the reporting person own after the transactions?

The reporting person beneficially owned 27,438 shares directly following the reported transactions.

What milestone triggered the PSU vesting for ALNY’s EVP?

Vesting was based on the issuer publicly reporting the initiation of a Phase 3 clinical study in a prevalent indication.

What is the reporting person’s role at ALNY?

Tolga Tanguler is ALNY’s EVP, Chief Commercial Officer.