Insmed (INSM) CFO sells 8,272 shares to cover RSU tax obligations

Rhea-AI Filing Summary

INSMED Inc Chief Financial Officer Sara Bonstein reported an open-market sale of 8,272 shares of common stock on May 13, 2026 at an average price of $116.18 per share. According to the filing, the shares were sold to satisfy tax withholding obligations and related broker fees arising from the vesting of Restricted Stock Units. After this transaction, Bonstein directly holds 71,486 shares of INSMED common stock, so the sale represents a relatively small portion of her overall reported holdings and is tied to compensation-related tax requirements rather than a discretionary portfolio change.

Insider Trade Summary

Net Seller: 8,272 shares ($961,041)

Net Sell 1 txn

Insider Bonstein Sara

Role Chief Financial Officer

Sold 8,272 shs ($961K)

Type	Security	Shares	Price	Value
Sale	Common Stock	8,272	$116.18	$961K

Holdings After Transaction: Common Stock — 71,486 shares (Direct, null)

Footnotes (1)

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Key Figures

Shares sold: 8,272 shares Sale price: $116.18 per share Post-transaction holdings: 71,486 shares

3 metrics

Shares sold 8,272 shares Open-market sale on May 13, 2026

Sale price $116.18 per share Average price for the 8,272 shares sold

Post-transaction holdings 71,486 shares Common stock held directly after the sale

Key Terms

Restricted Stock Units, tax withholding obligations, open-market sale, Form 4

4 terms

Restricted Stock Units financial

"upon the vesting of Restricted Stock Units and to cover related"

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.

tax withholding obligations financial

"Shares sold to satisfy tax withholding obligations upon the vesting"

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.

Form 4 regulatory

"INSIDER FILING DATA (Form 4):"

Form 4 is a official document that company insiders, such as executives or major shareholders, file with regulators whenever they buy or sell company shares. It provides transparency about how those with inside knowledge are trading, helping investors see if insiders are confident in the company's prospects or may be selling for personal reasons. This information can influence investor decisions by revealing insiders' perspectives on the company's value.

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^*

Bonstein Sara

(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 Financial Officer

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
05/13/2026

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	05/13/2026		S(1)		8,272	D	$116.18	71,486	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)
				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	05/15/2026
	** 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 CFO Sara Bonstein?

INSMED reported that CFO Sara Bonstein sold 8,272 shares of common stock. The sale occurred on May 13, 2026, as disclosed in a Form 4 insider trading report filed with regulators.

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

CFO Sara Bonstein sold 8,272 INSMED shares at an average price of $116.18 per share. This open-market transaction is documented in the Form 4 filing, including the exact share count and sale price.

Why did INSMED CFO Sara Bonstein sell 8,272 shares of INSM stock?

The shares were sold to satisfy tax withholding obligations from vested Restricted Stock Units and to cover related broker fees. The Form 4 footnote explicitly states this tax-related purpose for the disposition.

How many INSMED (INSM) shares does the CFO hold after this Form 4 sale?

After selling 8,272 shares, CFO Sara Bonstein directly holds 71,486 INSMED common shares. This post-transaction holding amount is reported in the Form 4 as the total shares beneficially owned following the sale.

Does the INSMED CFO’s share sale indicate a major change in ownership?

The sale represents only 8,272 shares, leaving the CFO with 71,486 shares afterward. Because the disposition is for tax withholding on RSU vesting, it reflects routine compensation-related activity rather than a large discretionary reduction.