[Form 4] INSMED Inc Insider Trading Activity

Rhea-AI Filing Summary

INSMED Inc Chair and CEO William Lewis reported an insider transaction involving company common stock. On June 3, 2026, he sold 7,605 shares of common stock at $102.27 per share. According to the footnote, these shares were sold to satisfy tax withholding obligations upon the vesting of Restricted Stock Units and to cover related broker fees, meaning this was a tax-related sale rather than a discretionary trade. Following the transaction, Lewis held 265,432 shares directly and 233,924 shares indirectly through a trust.

Insider Trade Summary

Net Seller: 7,605 shares ($777,763)

Net Sell 2 txns

Insider Lewis William

Role Chair and CEO

Sold 7,605 shs ($778K)

Type	Security	Shares	Price	Value
Sale	Common Stock	7,605	$102.27	$778K
holding	Common Stock	--	--	--

Holdings After Transaction: Common Stock — 265,432 shares (Direct, null); Common Stock — 233,924 shares (Indirect, By trust)

Footnotes (1)

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Form 4 Insider Transactions: What Each Field Means →

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 NEW JERSEY 08807

(City) (State) (Zip)

UNITED STATES

(Country)

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

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
06/03/2026

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

4. If Amendment, Date of Original Filed (Month/Day/Year)

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	06/03/2026		S(1)		7,605	D	$102.27	265,432	D
Common Stock								233,924	I	By 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	06/05/2026
	** 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.
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.
* Form 4: SEC 1474 (03-26)

FAQ

What insider transaction did INSMED (INSM) report for William Lewis?

INSMED reported that Chair and CEO William Lewis sold 7,605 shares of common stock at $102.27 per share. The sale was tied to tax withholding on vested Restricted Stock Units and related broker fees.

Why did INSMED CEO William Lewis sell 7,605 INSM shares?

The 7,605 shares were sold to satisfy tax withholding obligations upon the vesting of Restricted Stock Units and to cover related broker fees. This indicates a tax-related transaction rather than a discretionary open-market sale for portfolio reasons.

How many INSMED shares does William Lewis hold after this Form 4?

After the reported transactions, William Lewis held 265,432 INSMED common shares directly and 233,924 shares indirectly through a trust. These figures show his ongoing equity stake following the tax-related sale connected to Restricted Stock Unit vesting.

Was the INSMED CEO’s June 3, 2026 transaction an open-market sale?

The Form 4 classifies the 7,605-share transaction as an open-market sale at $102.27 per share. However, the footnote clarifies it was executed to cover tax withholding and broker fees related to Restricted Stock Unit vesting, reducing its signaling value.

Does the INSMED Form 4 show any option exercises or derivative activity?

The Form 4 data show no option exercises or other derivative transactions for William Lewis in this filing. The activity consists of a tax-related sale of 7,605 common shares and a separate holding entry for 233,924 shares held indirectly through a trust.