Insmed CFO sells shares to cover tax withholding

Insmed Inc.'s Chief Financial Officer, Sara Bonstein, reported a small share sale under a Form 4 filing.

Accepted by SEC EDGAR 02/04/2026 - 04:19 PM EST Learn about SEC filing dates

Rhea-AI Filing Summary

Insmed Inc.'s Chief Financial Officer, Sara Bonstein, reported a small share sale under a Form 4 filing. On 02/03/2026, she sold 748 shares of Insmed common stock at a price of $156.34 per share. According to the filing, these shares were sold to satisfy tax withholding obligations tied to the vesting of Restricted Stock Units and to cover related broker fees, rather than as a discretionary sale. After this transaction, Bonstein beneficially owned 79,758 shares of Insmed common stock directly.

Insider Trade Summary

Net Seller: 748 shares

Net Sell 1 txn

Insider Bonstein Sara

Role Chief Financial Officer

Sold 748 shs ($117K)

Share of Position Sold 0.93%

Type	Security	Shares	Price	Value
Sale	Common Stock	748	$156.34	$117K

Holdings After Transaction: Common Stock — 79,758 shares (Direct)

Holdings Before and After: Common Stock, 80,506 to 79,758 shares (Direct)

Other Insiders: 4 other insiders reported open-market sales of this stock in the 30 days up to this filing.

Footnotes (1)

1. F1. Shares sold to satisfy tax withholding obligations upon the vesting of Restricted Stock Units and to cover related broker fees.

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What insider transaction did Insmed (INSM) report for CFO Sara Bonstein?

Insmed reported that CFO Sara Bonstein sold 748 shares of common stock. The Form 4 shows the sale occurred on February 3, 2026 at $156.34 per share, primarily to cover tax withholding obligations from vesting Restricted Stock Units.

How many Insmed (INSM) shares did the CFO sell and at what price?

The CFO sold 748 shares of Insmed common stock at $156.34 per share. This transaction was disclosed as a routine sale to satisfy tax withholding obligations and related broker fees connected to the vesting of Restricted Stock Units.

How many Insmed (INSM) shares does the CFO hold after this Form 4 transaction?

After the reported sale, CFO Sara Bonstein beneficially owned 79,758 shares of Insmed common stock directly. This remaining balance reflects her holdings following the 748-share sale to cover tax withholding and associated broker costs.

Why were Insmed (INSM) shares sold by the CFO according to the Form 4 footnote?

The Form 4 footnote explains 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 the transaction was tied to equity compensation rather than a discretionary open-market sale.

What does this Insmed (INSM) Form 4 filing indicate about insider activity?

The filing shows a routine, compensation-related sale by the CFO, involving 748 shares sold to cover taxes and fees on vested Restricted Stock Units. It also confirms she continues to hold 79,758 shares of Insmed common stock directly after the transaction.

What is the purpose of a Form 4 filing for Insmed (INSM) insiders?

Form 4 is used to disclose insider trades in a company’s securities, including those by executives like the CFO. It provides details such as transaction date, number of shares, price, and reasons like tax withholding related to equity awards.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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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^*

Bonstein Sara

(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)

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

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)		748	D	$156.34	79,758	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)
				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/ Sara Bonstein, 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.
* 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.
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