Director adds Dyne Therapeutics (DYN) shares in open-market purchase

Rhea-AI Filing Summary

Dyne Therapeutics, Inc. director Brian S. Posner purchased 3,000 shares of common stock in an open-market transaction. The weighted average purchase price was $15.06 per share, with individual trade prices ranging from $14.96 to $15.12. Following this purchase, he directly owns 11,500 shares.

Insider Trade Summary

Net Buyer: 3,000 shares

Net Buy 1 txn

Insider Posner Brian S

Role Director

Bought 3,000 shs ($45K)

Type	Security	Shares	Price	Value
Purchase	Common Stock	3,000	$15.06	$45K

Holdings After Transaction: Common Stock — 11,500 shares (Direct)

Footnotes (1)

1. F1. The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices within the range of $14.96 to $15.12, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote of this Form 4.

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Form 4 Insider Transactions: What Each Field Means →

Accepted by SEC EDGAR 03/10/2026 - 05:33 PM Learn about SEC filing dates

FAQ

What insider transaction did Dyne Therapeutics (DYN) report on this Form 4?

Dyne Therapeutics reported that director Brian S. Posner bought 3,000 shares of common stock. The open-market purchase occurred on March 6, 2026, at a weighted average price of $15.06 per share, increasing his direct holdings to 11,500 shares.

At what price did Brian S. Posner buy Dyne Therapeutics (DYN) shares?

Brian S. Posner bought 3,000 Dyne Therapeutics shares at a weighted average of $15.06. The filing notes multiple trades with prices between $14.96 and $15.12 per share, reflecting typical market execution across a narrow intraday price range.

How many Dyne Therapeutics (DYN) shares does Brian S. Posner now own?

After the reported transaction, Brian S. Posner directly owns 11,500 Dyne Therapeutics common shares. This total reflects his existing position plus the 3,000 shares acquired in the March 6, 2026 open-market purchase disclosed in the Form 4 filing.

Was the Dyne Therapeutics (DYN) insider trade an open-market purchase?

Yes. The Form 4 describes the transaction as an open-market purchase of common stock. Director Brian S. Posner bought 3,000 shares on March 6, 2026, at a weighted average price of $15.06, based on multiple trades within a narrow price range.

What price range is disclosed for the Dyne Therapeutics (DYN) insider share purchases?

The filing states that the 3,000 purchased shares were bought in multiple trades between $14.96 and $15.12 per share. The weighted average transaction price reported is $15.06, and the insider has offered to provide detailed trade breakdowns upon request.

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)
03/06/2026

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	03/06/2026		P		3,000	A	$15.06(1)	11,500	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:

1. The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices within the range of $14.96 to $15.12, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote of this Form 4.

	/s/ Ron Caponigro, Attorney-in-Fact	03/10/2026
	** 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.