INSM insider filing shows $26.9M proposed sale; prior $5.19M sold

Rhea-AI Filing Summary

Form 144 filed for Insmed, Inc. (INSM) reporting a proposed sale of common stock. The notice lists a proposed sale of 186,648 shares through Merrill Lynch (Washington, DC) with an aggregate market value of $26,935,498 and total shares outstanding of 211,374,786. The shares to be sold were acquired on 09/02/2025 under a stock plan and the payment/settlement date is the same day. The filing also discloses that the reporting person, Martina Flammer, sold 55,564 shares during the past three months for aggregate gross proceeds of $5,190,291 across four transactions dated 06/03/2025 to 08/04/2025. The form includes the standard representation that the seller is not aware of undisclosed material adverse information.

Positive

• None.

Negative

• Large proposed insider sale: 186,648 shares with an aggregate market value of $26,935,498 may increase available float and could be viewed negatively by some investors
• Recent selling activity: The reporting person sold 55,564 shares in the prior three months for $5,190,291, indicating sustained dispositions

Insights

Securities Analyst

TL;DR: Insider selling is significant in size but appears executed under a stock plan; market impact depends on context.

The filing shows a proposed block sale of 186,648 common shares valued at $26.9 million, plus 55,564 shares sold in the prior three months for $5.19 million. For a company with 211.4 million shares outstanding, the proposed sale represents ~0.09% of outstanding shares, which is notable for an individual insider but not necessarily market-moving on its own. The transfer is documented as stock plan activity, indicating these are plan-originated shares rather than third-party disposition or litigation-driven sales. The size and recent cadence of sales are material to liquidity and dilution considerations and warrant monitoring alongside trading volumes.

Corporate Governance Expert

TL;DR: Routine insider disposition under a stock plan with required certification; no disclosed material nonpublic information.

The filer certified lack of undisclosed material adverse information and referenced a stock plan acquisition dated the same day as the proposed sale. That suggests compliance with Rule 144 procedural requirements and possible pre-established plan mechanics. The repeated disposals by the same person over recent months could reflect scheduled vesting or planned diversification. The form does not state adoption of a Rule 10b5-1 plan or the plan adoption date, so it is unclear whether these sales follow an affirmative pre-clearance schedule; that absence limits conclusions about intent or governance safeguards.

Form 144 Filer Information	UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Form 144 NOTICE OF PROPOSED SALE OF SECURITIES PURSUANT TO RULE 144 UNDER THE SECURITIES ACT OF 1933
FORM 144

144: Filer Information

Filer CIK
Filer CCC
Is this a LIVE or TEST Filing?	LIVE TEST
Submission Contact Information
Name
Phone
E-Mail Address

144: Issuer Information

Name of Issuer

SEC File Number

Address of Issuer

Phone

Name of Person for Whose Account the Securities are To Be Sold

See the definition of "person" in paragraph (a) of Rule 144. Information is to be given not only as to the person for whose account the securities are to be sold but also as to all other persons included in that definition. In addition, information shall be given as to sales by all persons whose sales are required by paragraph (e) of Rule 144 to be aggregated with sales for the account of the person filing this notice.

Relationship to Issuer

144: Securities Information

Title of the Class of Securities To Be Sold	Name and Address of the Broker	Number of Shares or Other Units To Be Sold	Aggregate Market Value	Number of Shares or Other Units Outstanding	Approximate Date of Sale	Name the Securities Exchange
Common	Merrill Lynch 1800 K ST NW Suite 800 Washington DC 20006	186648	26935498.00	211374786	09/02/2025	NASDAQ

Furnish the following information with respect to the acquisition of the securities to be sold and with respect to the payment of all or any part of the purchase price or other consideration therefor:

144: Securities To Be Sold

Title of the Class	Date you Acquired	Nature of Acquisition Transaction	Name of Person from Whom Acquired	Is this a Gift?	Date Donor Acquired	Amount of Securities Acquired	Date of Payment	Nature of Payment *
Common	09/02/2025	Stock Plan Activity	Issuer			186648	09/02/2025	n/a

* If the securities were purchased and full payment therefor was not made in cash at the time of purchase, explain in the table or in a note thereto the nature of the consideration given. If the consideration consisted of any note or other obligation, or if payment was made in installments describe the arrangement and state when the note or other obligation was discharged in full or the last installment paid.

Furnish the following information as to all securities of the issuer sold during the past 3 months by the person for whose account the securities are to be sold.

144: Securities Sold During The Past 3 Months

Name and Address of Seller	Title of Securities Sold	Date of Sale	Amount of Securities Sold	Gross Proceeds
Martina Flammer 700 US Highway 202/206 Bridgewater NJ 08807	Common	08/04/2025	8715	954031.00
Martina Flammer 700 US Highway 202/206 Bridgewater NJ 08807	Common	06/11/2025	19423	1834890.00
Martina Flammer 700 US Highway 202/206 Bridgewater NJ 08807	Common	06/10/2025	25740	2280821.00
Martina Flammer 700 US Highway 202/206 Bridgewater NJ 08807	Common	06/03/2025	1686	120549.00

144: Remarks and Signature

Remarks

Date of Notice

Date of Plan Adoption or Giving of Instruction, If Relying on Rule 10b5-1

ATTENTION:

The person for whose account the securities to which this notice relates are to be sold hereby represents by signing this notice that he does not know any material adverse information in regard to the current and prospective operations of the Issuer of the securities to be sold which has not been publicly disclosed. If such person has adopted a written trading plan or given trading instructions to satisfy Rule 10b5-1 under the Exchange Act, by signing the form and indicating the date that the plan was adopted or the instruction given, that person makes such representation as of the plan adoption or instruction date.

Signature

ATTENTION: Intentional misstatements or omission of facts constitute Federal Criminal Violations (See 18 U.S.C. 1001)

FAQ

What does the Form 144 for INSM disclose?

The form discloses a proposed sale of 186,648 common shares via Merrill Lynch with an aggregate market value of $26,935,498 and prior three-month sales of 55,564 shares totaling $5,190,291.

Who is the seller named in the filing?

The filing identifies Martina Flammer as the person who sold shares in the prior three months and is the subject of the proposed sale notice.

When were the shares to be sold acquired?

The shares listed for proposed sale were acquired on 09/02/2025 and the acquisition is described as Stock Plan Activity.

How many shares does INSM have outstanding per the filing?

The filing reports 211,374,786 shares outstanding.

Does the filing state whether there is undisclosed material information?

The signer represents by signing the notice that they do not know of any material adverse information about the issuer that has not been publicly disclosed.