Insmed CEO William Lewis files Form 4 stock sale

Insmed Chair and CEO William Lewis reported three sales of Insmed common stock on January 6–8, 2026.

Accepted by SEC EDGAR 01/08/2026 - 05:20 PM EST Learn about SEC filing dates

Rhea-AI Filing Summary

Insmed Chair and CEO William Lewis reported three sales of Insmed common stock on January 6–8, 2026. He sold 4,096 shares on January 6 at $173.33, 2,357 shares on January 7 at $175.07, and 3,223 shares on January 8 at $174.17, all reported as open market sales.

According to the filing, these shares were sold to satisfy tax withholding obligations upon the vesting of Restricted Stock Units and to cover related broker fees. After these transactions, Lewis directly held 315,407 shares of Insmed common stock. He also had indirect beneficial ownership of 233,924 shares held by the Katie Procter Dynasty Trust and 50,500 shares held by the William Lewis Family Legacy Trust.

Insider Trade Summary

Net Seller: 9,676 shares

Net Sell 3 txns

Insider Lewis William

Role Chair and CEO

Sold 9,676 shs ($1.68M)

Share of Position Sold 3.0%

Type	Security	Shares	Price	Value
Sale	Common Stock	3,223	$174.17	$561K
Sale	Common Stock	2,357	$175.07	$413K
Sale	Common Stock	4,096	$173.33	$710K
Holding	Common Stock	--	--	--
Holding	Common Stock	--	--	--

Holdings After Transaction: Common Stock — 315,407 shares (Direct); Common Stock — 233,924 shares (Indirect, By the Katie Procter Dynasty Trust); Common Stock — 50,500 shares (Indirect, By the William Lewis Family Legacy Trust)

Holdings Before and After: Common Stock, 325,083 to 315,407 shares (Direct)

Other Insiders: 4 other insiders reported open-market sales of this stock in the 30 days up to this filing.

Footnotes (1)

1. F1. Shares sold to satisfy tax withholding obligations upon the vesting of Restricted Stock Units and to cover related broker fees.

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What insider activity did Insmed (INSM) report for William Lewis?

The filing shows that Chair and CEO William Lewis reported three sales of Insmed common stock on January 6, 7, and 8, 2026, all coded as open market sales.

How many Insmed shares did William Lewis sell and at what prices?

William Lewis sold 4,096 shares at $173.33 on January 6, 2,357 shares at $175.07 on January 7, and 3,223 shares at $174.17 on January 8.

Why did Insmed CEO William Lewis sell these shares?

The filing explains that the shares were sold to satisfy tax withholding obligations upon the vesting of Restricted Stock Units and to cover related broker fees.

How many Insmed shares does William Lewis own after these transactions?

After the reported sales, William Lewis directly owned 315,407 shares of Insmed common stock.

What indirect Insmed shareholdings are associated with William Lewis?

The filing reports 233,924 shares held indirectly through the Katie Procter Dynasty Trust and 50,500 shares held through the William Lewis Family Legacy Trust.

What is William Lewis’s role at Insmed according to this filing?

William Lewis is identified as a Director and as an Officer, serving as Chair and CEO of Insmed.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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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^*

Lewis William

(Last) (First) (Middle)

700 US HIGHWAY 202/206

(Street)

BRIDGEWATER NJ 08807

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
INSMED Inc [ INSM ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	Chair and CEO

3. Date of Earliest Transaction (Month/Day/Year)
01/06/2026

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	01/06/2026		S(1)		4,096	D	$173.33	320,987	D
Common Stock	01/07/2026		S(1)		2,357	D	$175.07	318,630	D
Common Stock	01/08/2026		S(1)		3,223	D	$174.17	315,407	D
Common Stock								233,924	I	By the Katie Procter Dynasty Trust
Common Stock								50,500	I	By the William Lewis Family Legacy Trust

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. Shares sold to satisfy tax withholding obligations upon the vesting of Restricted Stock Units and to cover related broker fees.

Remarks:

	/s/ William Lewis, by Michael A. Smith as Attorney-in-fact	01/08/2026
	** 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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