DYN investor plans 4,986-share common stock sale

A shareholder associated with DYN, John Cox, filed to sell up to 4,986 shares of common stock through Stifel Nicolaus & Company on or after August 13, 2026 on Nasdaq, with an indicated market value of $131,034.00.

Rhea-AI Filing Summary

A shareholder associated with DYN, John Cox, filed to sell up to 4,986 shares of common stock through Stifel Nicolaus & Company on or after August 13, 2026 on Nasdaq, with an indicated market value of $131,034.00. The issuer reported 186,746,431 shares of common stock outstanding. Cox acquired 11,250 shares on August 12, 2026 via Restricted Stock Units as equity compensation from the issuer. Over the prior three months, he sold 2,683 shares of common stock on June 16, 2026 for $49,191.00.

Key Figures

Shares to be sold: 4,986 shares Planned sale market value: $131,034.00 Shares outstanding: 186,746,431 shares +3 more

6 metrics

Shares to be sold 4,986 shares Planned sale of common stock on or after August 13, 2026

Planned sale market value $131,034.00 Estimated market value of 4,986 shares of common stock

Shares outstanding 186,746,431 shares Common stock outstanding at time of planned sale

RSU shares acquired 11,250 shares Shares acquired August 12, 2026 via Restricted Stock Units as equity compensation

Recent shares sold 2,683 shares Common stock sold on June 16, 2026 during past three months

Proceeds from recent sale $49,191.00 Proceeds from 2,683-share sale on June 16, 2026

Key Terms

Restricted Stock Units, Equity Compensation, Nasdaq

3 terms

Restricted Stock Units financial

"Common Stock | 08/12/2026 | Restricted Stock Units | Issuer"

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.

Equity Compensation financial

"11250 | 08/13/2026 | Equity Compensation"

Equity compensation is pay given to employees, executives or contractors in the form of company ownership—such as stock, stock options or restricted shares—rather than just cash. It matters to investors because it can align workers' incentives with shareholders (like paying someone in slices of the same pie they help grow), but it also increases the number of shares outstanding and company expenses, affecting ownership percentages and earnings per share.

Nasdaq market

"186746431 | 08/13/2026 | Nasdaq"

The Nasdaq is a stock exchange where many companies' shares are bought and sold, functioning much like a marketplace for investments. It matters to investors because it provides a platform to buy and sell ownership stakes in companies, helping them track the value of those companies and make informed decisions. As one of the largest and most technology-focused markets, it also reflects trends and developments in the business world.

FAQ

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

What does the DYN Form 144 filing by John Cox disclose?

The filing states that John Cox plans to sell up to 4,986 shares of DYN common stock on or after August 13, 2026 on Nasdaq, with an estimated market value of $131,034.00 based on the figures reported.

How many DYN shares is John Cox registering for potential sale?

John Cox is registering up to 4,986 shares of DYN common stock for potential sale. These shares are to be sold through Stifel Nicolaus & Company Inc. on or after August 13, 2026, as indicated in the filing.

What prior DYN stock sales did John Cox report in the last three months?

The filing reports that on June 16, 2026, John Cox sold 2,683 shares of DYN common stock for proceeds of $49,191.00. This transaction is listed under securities sold during the past three months.

What equity compensation did John Cox receive from DYN before this Form 144?

John Cox acquired 11,250 DYN common shares on August 12, 2026 through Restricted Stock Units granted as Equity Compensation by the issuer, according to the acquisition details in the filing.

How many DYN shares were outstanding when this planned sale was reported?

The filing lists 186,746,431 shares of DYN common stock as outstanding. This figure provides context for the planned sale of 4,986 shares, which represents a very small portion of the total outstanding shares.

Which broker and market are involved in John Cox’s planned DYN share sale?

The planned sale will be executed through Stifel Nicolaus & Company Inc., located in St. Louis, Missouri. The DYN common stock is listed for trading on the Nasdaq market, as identified in the filing details.

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

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Accepted by SEC EDGAR 08/13/2026 - 05:04 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	0001498428
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	(781) 786-8230
Name of Person for Whose Account the Securities are To Be Sold	Cox John
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 Stock	Stifel Nicolaus & Company Inc 501 N Broadway St. Louis MO 63102	4986	131034.00	186746431	08/13/2026	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 Stock	08/12/2026	Restricted Stock Units	Issuer			11250	08/13/2026	Equity Compensation

* 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
John Cox 1560 Trapelo Rd Waltham MA 02451	Common Stock	06/16/2026	2683	49191.00

144: Remarks and Signature

Remarks
Date of Notice	08/13/2026
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	/s/ James Weimer, as a duly authorized representative of STIFEL, as attorney-in-fact for John Cox
ATTENTION: Intentional misstatements or omission of facts constitute Federal Criminal Violations (See 18 U.S.C. 1001)