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

Rhea-AI Filing Summary

Colleen F. Reitan, an Alnylam Pharmaceuticals director, reported multiple transactions on 09/09/2025 under a Rule 10b5-1(c) plan adopted June 10, 2025. She exercised a stock option to buy 18,000 shares at an exercise price of $100.65 and subsequently sold incremental blocks of common stock in multiple transactions at weighted-average prices ranging from $456.93 to $479.90. Following the reported trades, she directly beneficially owns 775 shares and holds options covering 18,000 shares exercisable through 06/01/2028. The filing was signed by her attorney-in-fact on 09/11/2025.

Positive

• Transactions were executed under a Rule 10b5-1(c) plan, providing preauthorization and regulatory defensibility
• Full disclosure of weighted-average sale price ranges and the exercise price enhances transparency

Negative

• Substantial reduction in direct share ownership from 18,775 shares to 775 shares following the reported sales
• Material insider sales (multiple tranches at weighted-average prices between $456.93 and $479.90) represent a significant change in insider exposure

Insights

Corporate Governance Expert

TL;DR: Insider used a documented 10b5-1 plan to exercise options then sell shares; this is a transparent, preplanned disposition.

The use of a Rule 10b5-1(c) trading plan, adopted June 10, 2025, indicates the transactions were preauthorized which reduces concerns about opportunistic trading around nonpublic information. The director exercised an option for 18,000 shares at a $100.65 strike and sold multiple tranches at weighted-average prices between ~$457 and ~$480, leaving 775 shares directly owned and continuing option exposure of 18,000 shares exercisable through 06/01/2028. Documentation and clear price ranges enhance governance transparency.

Securities Analyst

TL;DR: Large insider sales materially reduced direct shareholdings; could be viewed as a notable change in insider exposure.

The reporting person converted and sold significant equity: exercise of 18,000 options followed by staged sales that reduced direct holdings from 18,775 pre-trade to 775 post-trade. Sales executed at high market prices (weighted averages reported) realize substantial cash proceeds relative to the retained stake. For investors, the most relevant facts are the sharp drop in directly held shares and continued long-dated option holdings, both explicitly stated in the filing.

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).

X

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^*

Reitan Colleen F

(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
	Officer (give title below)		Other (specify below)

3. Date of Earliest Transaction (Month/Day/Year)
09/09/2025

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	09/09/2025		M(1)		18,000	A	$100.65	18,775	D
Common Stock	09/09/2025		S(1)		1,645	D	$457.44(2)	17,130	D
Common Stock	09/09/2025		S(1)		1,888	D	$458.86(3)	15,242	D
Common Stock	09/09/2025		S(1)		1,403	D	$459.73(4)	13,839	D
Common Stock	09/09/2025		S(1)		473	D	$460.71(5)	13,366	D
Common Stock	09/09/2025		S(1)		2,290	D	$461.92(6)	11,076	D
Common Stock	09/09/2025		S(1)		1,652	D	$463(7)	9,424	D
Common Stock	09/09/2025		S(1)		799	D	$464.36(8)	8,625	D
Common Stock	09/09/2025		S(1)		222	D	$471.25(9)	8,403	D
Common Stock	09/09/2025		S(1)		823	D	$472.82(10)	7,580	D
Common Stock	09/09/2025		S(1)		838	D	$474.22(11)	6,742	D
Common Stock	09/09/2025		S(1)		951	D	$474.85(12)	5,791	D
Common Stock	09/09/2025		S(1)		972	D	$476.31(13)	4,819	D
Common Stock	09/09/2025		S(1)		1,183	D	$477.47(14)	3,636	D
Common Stock	09/09/2025		S(1)		1,450	D	$478.67(15)	2,186	D
Common Stock	09/09/2025		S(1)		1,386	D	$479.55(16)	800	D
Common Stock	09/09/2025		S(1)		25	D	$480.98	775	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
Stock Option (right to buy)	$100.65	09/09/2025		M(1)			18,000	(17)	06/01/2028	Common Stock	18,000	$0.0	0	D

Explanation of Responses:

1. This transaction was made pursuant to a Rule 10b5-1(c) trading plan adopted by the Reporting Person on June 10, 2025.

2. The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $456.93 to $457.91. 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.

3. The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $458.22 to $459.09. 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.

4. The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $459.29 to $460.22. 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 $460.35 to $461.26. 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.

6. The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $461.42 to $462.41. 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 $462.73 to $463.52. 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 $464.18 to $464.96. 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 $470.77 to $471.75. 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 $472.37 to $473.30. 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 $473.48 to $474.48. 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.

12. The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $474.58 to $475.06. 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 $475.85 to $476.79. 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. The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $477.05 to $477.88. 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.

15. The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $478.33 to $479.30. 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.

16. The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $479.35 to $479.90. 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.

17. This stock option was fully vested and exercisable as of June 1, 2021.

	By: Brett Budzinski, Attorney-in-Fact For: Colleen F. Reitan	09/11/2025
	** 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 Colleen F. Reitan report on Form 4 for ALNY?

She reported exercising a stock option for 18,000 shares at $100.65 and multiple sales of common stock on 09/09/2025 under a 10b5-1 plan.

How many ALNY shares does Colleen Reitan own after the reported transactions?

Following the transactions she directly beneficially owns 775 shares and holds options covering 18,000 shares exercisable through 06/01/2028.

Were the sales preplanned or discretionary?

The filing states the trades were made pursuant to a Rule 10b5-1(c) trading plan adopted on June 10, 2025, indicating preplanned sales.

At what prices were the ALNY shares sold?

Weighted-average sale prices are reported in ranges with overall transaction prices between approximately $456.93 and $479.90.