DYN insiders file Form 144 to sell 143,749 shares

DYN insiders reported proposed sales of 143,749 shares of Common stock under Form 144.

Rhea-AI Filing Summary

DYN insiders reported proposed sales of 143,749 shares of Common stock under Form 144. The filing lists multiple selling holders with recent transactions: Atlas Venture Fund XI proposed 142,571 shares for $2,859,490.52, Atlas Venture Opportunity Fund II proposed 71,722 shares for $1,438,499.97, Atlas Venture Opportunity Fund I proposed 56,355 shares for $1,130,290.09, and Atlas Venture Associates XI proposed 1,401 shares for $28,099.31.

Key Figures

Proposed shares (header): 143,749 shares Atlas Venture Fund XI sale: 142,571 shares Atlas Venture Opportunity Fund II sale: 71,722 shares +2 more

5 metrics

Proposed shares (header) 143,749 shares Form 144 header line referencing Common and a shares count

Atlas Venture Fund XI sale 142,571 shares listed with <b>$2,859,490.52</b> and date <date>04/20/2026</date>

Atlas Venture Opportunity Fund II sale 71,722 shares listed with <b>$1,438,499.97</b> and date <date>04/20/2026</date>

Atlas Venture Opportunity Fund I sale 56,355 shares listed with <b>$1,130,290.09</b> and date <date>04/20/2026</date>

Atlas Venture Associates XI sale 1,401 shares listed with <b>$28,099.31</b> and date <date>04/20/2026</date>

Key Terms

Form 144, Private Placement, Securities To Be Sold, Issuer

4 terms

Form 144 regulatory

"Filer Information | 144: Filer Information"

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.

Private Placement market

"Common | 07/31/2020 | Private Placement"

A private placement is a sale of securities directly to a selected group of investors, typically institutions or accredited investors, instead of through a public offering. It lets a company raise money faster and with fewer regulatory steps; for existing shareholders it matters because the newly issued shares, often sold at a discount, increase the share count and can dilute their ownership.

Securities To Be Sold regulatory

"144: Securities To Be Sold"

Issuer legal

"Private Placement | Issuer"

FAQ

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

What does the DYN Form 144 filing report?

It reports proposed sales of Common stock by selling holders under Form 144. The filing lists specific selling holders and the number of shares and dollar amounts tied to those proposed sales on or around 04/20/2026, with an overall referenced lot of 143,749 shares.

Who are the selling holders named in the DYN Form 144?

Named sellers include Atlas Venture Fund XI, Atlas Venture Opportunity Fund II, Atlas Venture Opportunity Fund I, and Atlas Venture Associates XI. Each entry lists the holder, a sale date of 04/20/2026, share counts, and corresponding dollar amounts.

How many shares and proceeds are listed for Atlas Venture Fund XI in the filing?

Atlas Venture Fund XI is listed for 142,571 shares with a dollar amount of $2,859,490.52. The entry appears with a transaction date of 04/20/2026 and is reported as Common stock sale activity.

Does the Form 144 show the transaction method or buyer?

No specific buyers or execution methods are provided in the excerpt. The filing identifies the securities as Common stock and gives share counts and gross dollar figures; execution details are not shown in the provided content.

What is the filing date or timing shown for the DYN transactions?

The entries for the listed selling holders show a transaction date of 04/20/2026, and the header contains a date field of 04/21/2026, indicating the Form 144 information around those dates.

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

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Accepted by SEC EDGAR 04/21/2026 - 04:54 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	0001708269
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	Dyne Therapeutics, Inc.
SEC File Number	001-39509
Address of Issuer	1560 Trapelo Road Waltham MASSACHUSETTS 02451
Phone	7817868230
Name of Person for Whose Account the Securities are To Be Sold	Atlas Venture Fund XI, LP
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	Shareholder

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 555 California Street 18th Floor San Francisco CA 94104	143749	2877854.98	165027119	04/21/2026	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	07/31/2020	Private Placement	Issuer			143749	07/31/2020	Cash

* 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
Atlas Venture Fund XI, LP 300 Technology Sq 8th Floor Cambridge MA 02139	Common	04/20/2026	142571	2859490.52
Atlas Venture Opportunity Fund II, L.P. 300 Technology Sq 8th Floor Cambridge MA 02139	Common	04/20/2026	71722	1438499.97
Atlas Venture Opportunity Fund I, L.P. 300 Technology Sq 8th Floor Cambridge MA 02139	Common	04/20/2026	56355	1130290.09
Atlas Venture Associates XI, L.P. 300 Technology Sq 8th Floor Cambridge MA 02139	Common	04/20/2026	1401	28099.31

144: Remarks and Signature

Remarks
Date of Notice	04/21/2026
Date of Plan Adoption or Giving of Instruction, If Relying on Rule 10b5-1	03/19/2026
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	Ommer Chohan
ATTENTION: Intentional misstatements or omission of facts constitute Federal Criminal Violations (See 18 U.S.C. 1001)