Insmed (INSM) CMO sells 4,424 shares for tax withholding under plan

Filing Impact

(Moderate)

Filing Sentiment

(Negative)

Form Type

Rhea-AI Filing Summary

Insmed Inc.’s Chief Medical Officer, Dr. Martina Flammer, reported two small open-market sales of common stock made to cover taxes on equity compensation. She sold 2,566 shares at $102.27 on June 3 and 1,858 shares at $103.78 on June 5, totaling 4,424 shares. After these transactions, she directly holds 60,486 shares of Insmed common stock. The footnotes state the shares were sold to satisfy tax withholding obligations upon the vesting of Restricted Stock Units and related broker fees, and that the trades were executed under a pre-arranged Rule 10b5-1 trading plan adopted on February 27, 2025.

Insider Trade Summary 10b5-1

Net Seller: 4,424 shares ($455,248)

Net Sell 2 txns

Insider Flammer Martina M.D.

Role Chief Medical Officer

Sold 4,424 shs ($455K)

Type	Security	Shares	Price	Value
Sale	Common Stock	1,858	$103.78	$193K
Sale	Common Stock	2,566	$102.27	$262K

Holdings After Transaction: Common Stock — 60,486 shares (Direct, null)

Footnotes (1)

Shares sold to satisfy tax withholding obligations upon the vesting of Restricted Stock Units and to cover related broker fees. This transaction was effected pursuant to a 10b5-1 trading plan adopted by the Reporting Person on February 27, 2025 in accordance with Rule 10b5-1 of the Securities Exchange Act of 1934, as amended.

Key Figures

Shares sold June 3, 2026: 2,566 shares at $102.27 Shares sold June 5, 2026: 1,858 shares at $103.78 Total shares sold: 4,424 shares +2 more

5 metrics

Shares sold June 3, 2026 2,566 shares at $102.27 Open-market sale of common stock by CMO

Shares sold June 5, 2026 1,858 shares at $103.78 Open-market sale of common stock by CMO

Total shares sold 4,424 shares Net shares sold across two June transactions

Holdings after transactions 60,486 shares Direct Insmed common stock held by CMO after sales

10b5-1 plan adoption date February 27, 2025 Date CMO adopted Rule 10b5-1 trading plan

Key Terms

Restricted Stock Units, Rule 10b5-1 trading plan, open-market sale, tax withholding obligations

4 terms

Restricted Stock Units financial

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

Restricted stock units are a type of company reward where employees are promised shares of stock, but they only fully own these shares after meeting certain conditions, like staying with the company for a set time. They matter because they can become valuable assets and are often used to motivate employees to help the company succeed.

Rule 10b5-1 trading plan regulatory

"This transaction was effected pursuant to a 10b5-1 trading plan adopted by the Reporting Person on February 27, 2025."

A Rule 10b5-1 trading plan is a pre-arranged schedule that allows company insiders to buy or sell stock at specific times, even if they have inside information. It helps prevent accusations of unfair trading by making these transactions look planned and transparent, rather than sneaky or illegal.

open-market sale financial

"transaction_action: open-market sale"

An open-market sale is when a shareholder sells existing shares directly on a public exchange to any willing buyer, rather than through a private deal. Think of it like putting goods on a busy market stall where price is set by supply and demand; for investors it matters because such sales increase available supply, can put short-term downward pressure on the stock price, and signal changes in liquidity or investor confidence.

tax withholding obligations financial

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

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Form 4 Insider Transactions: What Each Field Means →

06/05/2026 - 04:11 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^*

Flammer Martina M.D.

(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)

	Director	10% Owner
X	Officer (give title below)	Other (specify below)
	Chief Medical Officer

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)
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	06/03/2026		S⁽¹⁾		2,566	D	$102.27	62,344	D
Common Stock	06/05/2026		S⁽²⁾		1,858	D	$103.78	60,486	D

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)

Explanation of Responses:

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

2. This transaction was effected pursuant to a 10b5-1 trading plan adopted by the Reporting Person on February 27, 2025 in accordance with Rule 10b5-1 of the Securities Exchange Act of 1934, as amended.

Remarks:

	/s/ Martina Flammer, M.D., 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)

Source: View Original Filing on SEC EDGAR

FAQ

What insider transaction did Insmed (INSM) report for Dr. Martina Flammer?

Insmed reported that Chief Medical Officer Dr. Martina Flammer sold 4,424 shares of common stock in two open-market transactions. These sales were tied to tax withholding on vested Restricted Stock Units, rather than discretionary portfolio changes.

On what dates and at what prices did the Insmed (INSM) CMO sell shares?

Dr. Martina Flammer sold 2,566 Insmed shares on June 3 at $102.27 and 1,858 shares on June 5 at $103.78. Both transactions involved common stock and were conducted as open-market sales.

How many Insmed (INSM) shares does the CMO hold after these Form 4 sales?

After the reported transactions, Dr. Martina Flammer directly holds 60,486 shares of Insmed common stock. This figure reflects her remaining position following the combined sale of 4,424 shares in early June.

Why did the Insmed (INSM) CMO sell shares according to the Form 4 footnotes?

The footnotes explain that the shares were sold to satisfy tax withholding obligations arising from the vesting of Restricted Stock Units and to cover related broker fees. This indicates a tax-related, compensation-driven disposition rather than a discretionary sale.

Were the recent Insmed (INSM) insider sales made under a Rule 10b5-1 plan?

Yes. The filing states the transactions were effected pursuant to a Rule 10b5-1 trading plan adopted on February 27, 2025. Such plans pre-schedule trades, suggesting these sales were part of a pre-arranged program rather than market-timing decisions.