Director buys 2,000 Dyne Therapeutics (DYN) shares in open market

Rhea-AI Filing Summary

Dyne Therapeutics director Brian S. Posner purchased additional shares of the company. On March 11, 2026, he made an open-market purchase of 2,000 shares of Dyne Therapeutics common stock at a price of $19.35 per share. Following this transaction, he directly owns 13,500 shares.

Insider Trade Summary

Net Buyer: 2,000 shares ($38,700)

Net Buy 1 txn

Insider Posner Brian S

Role Director

Bought 2,000 shs ($39K)

Type	Security	Shares	Price	Value
Purchase	Common Stock	2,000	$19.35	$39K

Holdings After Transaction: Common Stock — 13,500 shares (Direct)

Footnotes (1)

Form 4 Insider Transactions: What Each Field Means →

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Posner Brian S

(Last) (First) (Middle)

1560 TRAPELO ROAD

(Street)

WALTHAM MA 02451

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
Dyne Therapeutics, Inc. [ DYN ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director		10% Owner
	Officer (give title below)		Other (specify below)

3. Date of Earliest Transaction (Month/Day/Year)
03/11/2026

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock	03/11/2026		P		2,000	A	$19.35	13,500	D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

Explanation of Responses:

	/s/ Ron Caponigro, Attorney-in-Fact	03/13/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.

FAQ

What insider transaction did Dyne Therapeutics (DYN) report?

Dyne Therapeutics reported an open-market share purchase by director Brian S. Posner. He bought 2,000 shares of common stock at $19.35 per share, increasing his direct holdings to 13,500 shares after the transaction.

How many Dyne Therapeutics (DYN) shares did Brian S. Posner buy?

Brian S. Posner bought 2,000 Dyne Therapeutics common shares. The purchase was an open-market transaction at a price of $19.35 per share, and it raised his direct ownership to a total of 13,500 shares.

At what price did the Dyne Therapeutics (DYN) director purchase shares?

The director paid $19.35 per share for Dyne Therapeutics stock. This price applied to 2,000 common shares acquired in an open-market purchase, bringing his directly owned position to 13,500 shares following completion of the transaction.

What is Brian S. Posner’s Dyne Therapeutics (DYN) stake after the Form 4 transaction?

After the reported transaction, Brian S. Posner directly holds 13,500 shares. This reflects an increase driven by his open-market purchase of 2,000 Dyne Therapeutics common shares at a price of $19.35 per share on March 11, 2026.

Was the Dyne Therapeutics (DYN) insider transaction a purchase or a sale?

The reported Dyne Therapeutics insider transaction was a purchase. Director Brian S. Posner executed an open-market buy of 2,000 common shares at $19.35 per share, raising his directly owned holdings to 13,500 shares according to the Form 4 data.