Insmed (NASDAQ: INSM) CEO tax sale updates direct and trust holdings

Rhea-AI Filing Summary

Insmed Inc. Chair and CEO William Lewis reported a routine share sale linked to tax withholding. On February 3, 2026, he sold 3,009 shares of common stock at $156.34 per share to satisfy tax obligations from vested restricted stock units and related broker fees. After this sale, he directly owned 303,882 shares of Insmed common stock. In addition, he had indirect beneficial ownership of 233,924 shares through the Katie Procter Dynasty Trust and 50,500 shares through the William Lewis Family Legacy Trust.

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

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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^*

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)
02/03/2026

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	02/03/2026		S(1)		3,009	D	$156.34	303,882	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	02/04/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
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FAQ

What insider transaction did INSM CEO William Lewis report?

William Lewis reported selling 3,009 shares of Insmed common stock. The sale occurred on February 3, 2026, at a price of $156.34 per share and was executed to cover tax withholding obligations from vested restricted stock units and related broker fees.

Was the INSM insider sale by William Lewis a discretionary stock sale?

The filing states the 3,009 shares were sold to satisfy tax withholding obligations. This means the sale was tied to the vesting of restricted stock units and related broker fees, rather than being described as a purely discretionary open-market liquidation of holdings.

How many INSM shares does William Lewis own after this Form 4?

After the reported transaction, William Lewis directly owned 303,882 shares of Insmed common stock. He also had indirect beneficial ownership of 233,924 shares through the Katie Procter Dynasty Trust and 50,500 shares through the William Lewis Family Legacy Trust, according to the filing.

At what price were the INSM shares sold in the February 3, 2026 trade?

The 3,009 Insmed common shares were sold at $156.34 per share. The transaction occurred on February 3, 2026, and was reported with transaction code “S,” with a footnote explaining the sale was to cover tax withholding and broker fees tied to RSU vesting.

What indirect INSM holdings are reported for William Lewis?

The filing shows indirect beneficial ownership of Insmed common stock through two trusts. It reports 233,924 shares held by the Katie Procter Dynasty Trust and 50,500 shares held by the William Lewis Family Legacy Trust, in addition to Lewis’s directly held shares.

What does the footnote in the INSM Form 4 explain about the sale?

The footnote explains that the 3,009 shares were sold to satisfy tax withholding obligations upon the vesting of restricted stock units. It also notes the sale helped cover related broker fees, clarifying the sale’s purpose as tax-related rather than purely opportunistic.