INSM Form 144: William Lewis proposes 10,699-share sales

INSM reports proposed sales of Common Stock by William Lewis under Rule 144.

Rhea-AI Filing Summary

INSM reports proposed sales of Common Stock by William Lewis under Rule 144. The filing lists multiple proposed sale dates with 10,699 shares on each listed trade date, including 05/04/2026, 04/16/2026, 04/06/2026, 03/19/2026, 03/05/2026, and 02/19/2026.

The Securities Information section shows 216,752,451 with an associated date of 05/13/2026, and the filing references Stock Plan Activity on 05/11/2026. The filing names William Lewis as the selling party and provides addresses for notification.

Insights

Securities Lawyer

Form 144 notifies the SEC of proposed Rule 144 resales by a holder.

Form 144 is an administrative notice that a holder, here William Lewis, intends to sell restricted or control securities under Rule 144. The filing lists repeated entries of 10,699 shares on several dates and identifies stock plan activity on 05/11/2026.

Key dependencies are the continued satisfaction of Rule 144 conditions and any broker-dealer handling the sales. Subsequent Form 4 or trade reports could confirm actual dispositions; timing and cash-flow treatment are not specified in the provided excerpt.

Key Figures

Proposed sale per entry: 10,699 shares Trade dates shown: 02/19/2026; 03/05/2026; 03/19/2026; 04/06/2026; 04/16/2026; 05/04/2026 Securities Information figure: 216,752,451 +2 more

5 metrics

Proposed sale per entry 10,699 shares listed on multiple trade dates in the filing

Trade dates shown 02/19/2026; 03/05/2026; 03/19/2026; 04/06/2026; 04/16/2026; 05/04/2026 dates associated with the 10,699-share entries

Securities Information figure 216,752,451 appears with date 05/13/2026 in Securities Information line

Stock Plan Activity date 05/11/2026 listed under Securities To Be Sold as Stock Plan Activity

Registrant identifier 13283 appears in multiple filing lines

Key Terms

Form 144, Rule 144, Stock Plan Activity

3 terms

Form 144 regulatory

"144: Securities To Be Sold"

Form 144 is a document that investors must file with the government when they plan to sell a large number of shares of a company's stock. It helps ensure transparency so everyone knows how many shares are being sold and when, which can impact the stock's price.

Rule 144 regulatory

"144: Securities Sold During The Past 3 Months"

Rule 144 is a U.S. securities regulation that sets conditions under which restricted or insider-held shares can be legally resold to the public, such as required holding periods, availability of public information, limits on how much can be sold at once, and certain filing requirements. For investors it matters because it determines when previously locked-up shares can enter the market — like a release valve that can increase supply, affect share price, and signal insider intent.

Stock Plan Activity financial

"Stock Plan Activity | Issuer | 05/11/2026"

FAQ

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

What does INSM's Form 144 disclose about William Lewis's transactions?

It discloses proposed resales of Common Stock by William Lewis, each listed as 10,699 shares. The filing lists trade dates from 02/19/2026 through 05/04/2026 and notes stock plan activity on 05/11/2026 in the Securities Information section.

Does the filing state how many INSM shares are outstanding?

The Securities Information shows 216,752,451 with a date of 05/13/2026. That number appears in the filing’s Securities Information line alongside a Nasdaq label and the date 05/13/2026, providing a context anchor in the excerpt.

Is the Form 144 itself a confirmation that the shares were sold?

No. Form 144 notifies intent to sell; it is not proof of completed sales. Actual dispositions require trade reports or Form 4/5 filings; this excerpt lists proposed sale dates and quantities but does not confirm settlement or proceeds.

What is the role of the "Stock Plan Activity" note on 05/11/2026?

The excerpt lists a Stock Plan Activity entry dated 05/11/2026 under Securities To Be Sold. It indicates plan-related securities are referenced in the filing, but the excerpt does not specify exercises, vesting, or cash-flow treatment linked to that activity.

Where can investors find confirmation of completed sales mentioned here?

Confirmation appears in subsequent trade reports or Forms 4/5 if required by reporting rules. This excerpt lists proposed sale dates and quantities; completed transactions and resulting holdings would be shown in later filings or broker reports.

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

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Accepted by SEC EDGAR 05/13/2026 - 05:14 PM EDT Learn about SEC filing dates

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	0001402051
Filer CCC	XXXXXXXX
Is this a LIVE or TEST Filing?	LIVE TEST
Submission Contact Information
Name
Phone
E-Mail Address

144: Issuer Information

Name of Issuer	INSMED INC
SEC File Number	000-30739
Address of Issuer	700 US Highway 202/206 Bridgewater NEW JERSEY 08807
Phone	9089779900
Name of Person for Whose Account the Securities are To Be Sold	William Lewis
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	Officer

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	13283	1543218	216752451	05/13/2026	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	05/11/2026	Stock Plan Activity	Issuer			13283	05/11/2026	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
William Lewis 700 US Highway 202/206 Bridgewater NJ 08807	Common	05/04/2026	10699	1469434
William Lewis 700 US Highway 202/206 Bridgewater NJ 08807	Common	04/16/2026	10699	1540292
William Lewis 700 US Highway 202/206 Bridgewater NJ 08807	Common	04/06/2026	10699	1746319
William Lewis 700 US Highway 202/206 Bridgewater NJ 08807	Common	03/19/2026	10699	1535514
William Lewis 700 US Highway 202/206 Bridgewater NJ 08807	Common	03/05/2026	10699	1562311
William Lewis 700 US Highway 202/206 Bridgewater NJ 08807	Common	02/19/2026	10699	1615250

144: Remarks and Signature

Remarks
Date of Notice	05/13/2026
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	William Lewis
ATTENTION: Intentional misstatements or omission of facts constitute Federal Criminal Violations (See 18 U.S.C. 1001)