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

Yes. The Form 4 states the transactions were effected under a Rule 10b5-1 trading plan. This plan was adopted by William Lewis on September 4, 2025, providing a pre-arranged framework for selling shares over time under predefined instructions.

What is William Lewis’s direct INSM share ownership after these transactions?

After the reported exercises and sales, William Lewis directly owned 301,185 shares of Insmed common stock. This figure reflects his direct holdings as of March 5, 2026, immediately following completion of the disclosed option exercises and open-market sales.

Did William Lewis disclose changes to any prior INSM-related trust holdings?

Yes. A footnote states he no longer has a reportable beneficial interest in securities owned by the William Lewis Family Legacy Trust. Those securities had been included in his prior ownership reports but are no longer considered reportable beneficial holdings.

Insmed (NASDAQ: INSM) CEO reports option exercises and 10,699-share sale

Filing Impact

(Very High)

Filing Sentiment

(Negative)

Form Type

Rhea-AI Filing Summary

INSMED Inc Chair and CEO William Lewis reported multiple transactions in company stock. On 2026-03-05, he exercised stock options for 6,259 and 4,440 shares of common stock through derivative conversions. He then sold a total of 10,699 common shares in open-market transactions at weighted average prices noted in the filing, effected under a Rule 10b5-1 trading plan adopted on September 4, 2025. After these trades, he held 301,185 common shares directly and 233,924 common shares indirectly through the Katie Procter Dynasty Trust as of that date.

Insider Trade Summary

Net Seller: 10,699 shares ($1,562,328)

Net Sell 9 txns

Insider Lewis William

Role Chair and CEO

Sold 10,699 shs ($1.56M)

Type	Security	Shares	Price	Value
Exercise	Stock Option (right to buy)	6,259	$0.00	--
Exercise	Stock Option (right to buy)	4,440	$0.00	--
Exercise	Common Stock	6,259	$30.46	$191K
Exercise	Common Stock	4,440	$17.16	$76K
Sale	Common Stock	2,083	$144.23	$300K
Sale	Common Stock	2,589	$145.27	$376K
Sale	Common Stock	3,899	$146.66	$572K
Sale	Common Stock	2,128	$147.54	$314K
holding	Common Stock	--	--	--

Holdings After Transaction: Stock Option (right to buy) — 56,332 shares (Direct); Common Stock — 307,444 shares (Direct); Common Stock — 233,924 shares (Indirect, By the Katie Procter Dynasty Trust)

Footnotes (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. This is the weighted average sales price representing 2,083 shares sold at prices ranging from $143.84 to $144.70 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. This is the weighted average sales price representing 2,589 shares sold at prices ranging from $144.99 to $145.78 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. This is the weighted average sales price representing 3,899 shares sold at prices ranging from $146.09 to $147.06 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. This is the weighted average sales price representing 2,128 shares sold at prices ranging from $147.15 to $148.04 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. The Reporting Person no longer has a reportable beneficial interest in the securities owned by the William Lewis Family Legacy Trust, which were included in the Reporting Person's prior ownership reports. 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.

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Form 4 Insider Transactions: What Each Field Means →

03/05/2026 - 04:16 PM

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

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)
03/05/2026

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)
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	Code	V	Amount	(A) or (D)	Price		6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
Common Stock	03/05/2026		M⁽¹⁾		6,259	A	$30.46	307,444	D
Common Stock	03/05/2026		M⁽¹⁾		4,440	A	$17.16	311,884	D
Common Stock	03/05/2026		S⁽¹⁾		2,083	D	$144.23⁽²⁾	309,801	D
Common Stock	03/05/2026		S⁽¹⁾		2,589	D	$145.27⁽³⁾	307,212	D
Common Stock	03/05/2026		S⁽¹⁾		3,899	D	$146.66⁽⁴⁾	303,313	D
Common Stock	03/05/2026		S⁽¹⁾		2,128	D	$147.54⁽⁵⁾	301,185⁽⁶⁾	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)
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)	Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	8. Price of Derivative Security (Instr. 5)		10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
Stock Option (right to buy)	$30.46	03/05/2026		M⁽¹⁾			6,259	⁽⁷⁾	01/04/2028	Common Stock	6,259	$0	56,332	D
Stock Option (right to buy)	$17.16	03/05/2026		M⁽¹⁾			4,440	⁽⁷⁾	05/17/2027	Common Stock	4,440	$0	39,960	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 2,083 shares sold at prices ranging from $143.84 to $144.70 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 2,589 shares sold at prices ranging from $144.99 to $145.78 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 3,899 shares sold at prices ranging from $146.09 to $147.06 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. This is the weighted average sales price representing 2,128 shares sold at prices ranging from $147.15 to $148.04 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.

6. The Reporting Person no longer has a reportable beneficial interest in the securities owned by the William Lewis Family Legacy Trust, which were included in the Reporting Person's prior ownership reports.

7. 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	03/05/2026
	** 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.

Source: View Original Filing on SEC EDGAR

FAQ

What insider transactions did INSM CEO William Lewis report on this Form 4?

William Lewis reported exercising two stock option awards into common stock and selling 10,699 common shares. The sales were executed in multiple open-market transactions at weighted average prices disclosed in the filing, all under a pre-arranged Rule 10b5-1 trading plan.

How many INSM shares did William Lewis sell in the reported transactions?

William Lewis sold a total of 10,699 shares of Insmed common stock. These shares were sold in four separate open-market transactions, each with its own weighted average price and price range, as detailed in the Form 4 footnotes for transparency.

What indirect INSM holdings are reported for William Lewis on this Form 4?

The Form 4 reports indirect ownership of 233,924 Insmed common shares held "By the Katie Procter Dynasty Trust." These shares are reported as indirect beneficial ownership, separate from William Lewis’s directly held shares reported in the same filing.