Rule 144 notices: DYN affiliate share sales reported

DYN affiliates reported proposed resale of Common Stock under Rule 144 by multiple Atlas Venture entities, with recent sales reported on 04/20/2026.

Rhea-AI Filing Summary

DYN affiliates reported proposed resale of Common Stock under Rule 144 by multiple Atlas Venture entities, with recent sales reported on 04/20/2026. The filing lists per-holder transactions: 142,571 shares ($2,859,490.52), 71,722 shares ($1,438,499.97), 56,355 shares ($1,130,290.09), and 1,401 shares ($28,099.31).

Insights

Securities Counsel

Rule 144 resale notices by affiliate holders of DYN common stock were filed listing specific recent sales.

The filing lists affiliated selling holders and exact share counts and gross proceeds for transactions dated 04/20/2026. These entries function as notice of intended or completed restricted/resale transactions under resale rules.

Cash‑flow treatment is direct to the selling holders per the listed cash amounts; timing and any transfer restrictions beyond Rule 144 language are not provided in the excerpt.

Key Figures

Shares sold by Atlas Venture Fund XI, LP: 142,571 shares Gross proceeds for Atlas Venture Fund XI, LP: $2,859,490.52 Shares sold by Atlas Venture Opportunity Fund II, L.P.: 71,722 shares +5 more

8 metrics

Shares sold by Atlas Venture Fund XI, LP 142,571 shares sale dated 04/20/2026

Gross proceeds for Atlas Venture Fund XI, LP $2,859,490.52 associated with 142,571 shares on 04/20/2026

Shares sold by Atlas Venture Opportunity Fund II, L.P. 71,722 shares sale dated 04/20/2026

Gross proceeds for Atlas Venture Opportunity Fund II, L.P. $1,438,499.97 associated with 71,722 shares on 04/20/2026

Shares sold by Atlas Venture Opportunity Fund I, L.P. 56,355 shares sale dated 04/20/2026

Gross proceeds for Atlas Venture Opportunity Fund I, L.P. $1,130,290.09 associated with 56,355 shares on 04/20/2026

Shares sold by Atlas Venture Associates XI, L.P. 1,401 shares sale dated 04/20/2026

Gross proceeds for Atlas Venture Associates XI, L.P. $28,099.31 associated with 1,401 shares on 04/20/2026

Key Terms

Private Placement, Rule 144, Gross proceeds

3 terms

Private Placement regulatory

"Private Placement | Issuer | 08/07/2020 | Cash"

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.

Rule 144 regulatory

"144: Securities To Be Sold"

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.

Gross proceeds financial

"142571 | 2859490.52"

The total amount of cash a company receives from a financing event or sale before any fees, expenses, taxes or deductions are taken out. Investors watch gross proceeds because it shows the raw scale of new capital being raised—think of it as the paycheck amount before withholdings—which helps assess how much funding is available for operations, growth, debt payoff or how much shareholder dilution might occur once costs are removed.

FAQ

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

What does DYN's Form 144 report say about recent insider sales?

It reports proposed or recent sales by Atlas Venture affiliates totaling specific share counts on 04/20/2026. The filing lists four transactions: 142,571; 71,722; 56,355; and 1,401 shares with corresponding gross proceeds shown in dollars.

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

Atlas Venture entities are listed as selling holders. The excerpt names Atlas Venture Fund XI, LP; Atlas Venture Opportunity Fund II, L.P.; Atlas Venture Opportunity Fund I, L.P.; and Atlas Venture Associates XI, L.P.

How many shares did Atlas Venture Fund XI, LP report selling for DYN?

Atlas Venture Fund XI, LP reported 142,571 shares sold. The filing pairs that share count with gross proceeds of $2,859,490.52 and the transaction date 04/20/2026.

Does the Form 144 state who received the cash proceeds for the DYN sales?

The excerpt links each share count to a dollar amount, indicating cash proceeds to the selling holders. The filing shows per‑holder gross proceeds amounts alongside the share counts for 04/20/2026.

Are these DYN shares registered or part of a public offering?

The filing reflects Rule 144 sales by affiliates, not a registered offering. The excerpt identifies the transactions as private‑placement origin shares and lists them as sales under applicable resale rules.

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

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Accepted by SEC EDGAR 04/21/2026 - 04:53 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	0001759241
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 Opportunity Fund I, 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	56820	1137536.4	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	08/07/2020	Private Placement	Issuer			56820	08/07/2020	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)