INSMED (NASDAQ: INSM) CEO exercises options and sells 10,699 shares under 10b5-1 plan

Rhea-AI Filing Summary

INSMED Inc Chair and CEO William Lewis exercised stock options and sold shares in a planned transaction. On 2026-03-19, he exercised options for 10,699 shares of common stock at exercise prices of $30.46 and $17.16 per share, converting them into common shares.

That same day, he sold 10,699 shares of common stock in open-market trades at weighted average prices ranging from about $141.80 to $144.72, under a pre-arranged Rule 10b5-1 trading plan adopted on September 4, 2025. After these transactions, he directly holds 301,185 shares, plus 233,924 shares held indirectly through the Katie Procter Dynasty Trust.

Insights

Equity compensation and insider-trading analyst

Routine option exercise paired with 10b5-1 sales; position remains sizable.

Chair and CEO William Lewis exercised options for 10,699 shares of INSMED Inc common stock at exercise prices of $30.46 and $17.16 per share, then sold an equal number of shares in open-market trades.

The filing notes these sales were executed under a pre-arranged Rule 10b5-1 trading plan adopted on September 4, 2025, which typically indicates a scheduled, portfolio-management process rather than discretionary timing. Following the net-sell activity, he still directly holds 301,185 shares and indirectly 233,924 through the Katie Procter Dynasty Trust.

This pattern is characteristic of an exercise-and-sell sequence where options are converted into shares and then monetized, while a substantial equity stake is retained. From an investment perspective, such 10b5-1 activity is generally interpreted as routine and not thesis-changing absent additional company-specific developments.

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^*

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)
03/19/2026

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	03/19/2026		M(1)		6,259	A	$30.46	307,444	D
Common Stock	03/19/2026		M(1)		4,440	A	$17.16	311,884	D
Common Stock	03/19/2026		S(1)		1,629	D	$142.17(2)	310,255	D
Common Stock	03/19/2026		S(1)		4,537	D	$143.42(3)	305,718	D
Common Stock	03/19/2026		S(1)		4,533	D	$144.11(4)	301,185	D
Common Stock								233,924	I	By the Katie Procter Dynasty 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
Stock Option (right to buy)	$30.46	03/19/2026		M(1)			6,259	(5)	01/04/2028	Common Stock	6,259	$0	50,073	D
Stock Option (right to buy)	$17.16	03/19/2026		M(1)			4,440	(5)	05/17/2027	Common Stock	4,440	$0	35,520	D

Explanation of Responses:

1. This transaction was effected pursuant to a 10b5-1 trading plan adopted by the Reporting Person on September 4, 2025 in accordance with Rule 10b5-1 of the Securities Exchange Act of 1934, as amended.

2. This is the weighted average sales price representing 1,629 shares sold at prices ranging from $141.80 to $142.74 per share. The Reporting Person undertakes to provide to the SEC staff, the issuer, or a security holder of the issuer the number of shares sold at each price within the price range upon request.

3. This is the weighted average sales price representing 4,537 shares sold at prices ranging from $142.80 to $143.77 per share. The Reporting Person undertakes to provide to the SEC staff, the issuer, or a security holder of the issuer the number of shares sold at each price within the price range upon request.

4. This is the weighted average sales price representing 4,533 shares sold at prices ranging from $143.80 to $144.72 per share. The Reporting Person undertakes to provide to the SEC staff, the issuer, or a security holder of the issuer the number of shares sold at each price within the price range upon request.

5. The options became exercisable based on the following vesting schedule: 25% vested on the first anniversary of the grant date and an additional 12.5% vested on each sixth month anniversary date thereafter through the fourth anniversary of the date of grant.

Remarks:

	/s/ William Lewis, by Michael A. Smith as Attorney-in-fact	03/20/2026
	** 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 transactions did INSM (INSMED Inc) report for William Lewis?

INSM reported that Chair and CEO William Lewis exercised stock options for 10,699 shares and sold 10,699 common shares on 2026-03-19. The sales were executed in the open market under a pre-arranged Rule 10b5-1 trading plan adopted on September 4, 2025.

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

William Lewis sold 10,699 INSM common shares in three open-market trades on 2026-03-19. The weighted average sale prices ranged from about $141.80 to $144.72 per share, as detailed in the Form 4 footnotes describing the price ranges for each transaction.

What stock options did William Lewis exercise in this INSM Form 4?

He exercised options covering 10,699 shares of INSM common stock. The options had exercise prices of $30.46 and $17.16 per share and were structured to vest over time, with 25% vesting after one year and additional portions vesting every six months through the fourth anniversary.

Were William Lewis’s INSM share sales under a Rule 10b5-1 plan?

Yes. A footnote states the transactions were effected under a Rule 10b5-1 trading plan adopted on September 4, 2025. Such plans pre-schedule trades, indicating these sales followed a preset program rather than opportunistic timing based on short-term market developments.

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

After the reported transactions, William Lewis directly owns 301,185 INSM common shares. The Form 4 also shows an additional 233,924 shares held indirectly through the Katie Procter Dynasty Trust, reflecting a substantial ongoing equity interest in the company.

What does the Katie Procter Dynasty Trust holding mean for INSM ownership disclosure?

The Form 4 lists 233,924 INSM shares held indirectly "By the Katie Procter Dynasty Trust." This indicates a separate trust entity holds those shares, with Lewis reporting them as indirect beneficial ownership, providing transparency about equity interests connected to him.