Dyne Therapeutics, Inc. Insider Trading Activity

Insider Trade Summary

Net Buyer: 100,000 shares

Net Buy 9 txns

Insider Cox John

Role CEO & President

Bought 100,000 shs ($911K)

Type	Security	Shares	Price	Value
Gift	Common Stock	10,000	$0.00	$0.00
Gift	Common Stock	10,000	$0.00	$0.00
Gift	Common Stock	10,000	$0.00	$0.00
Gift	Common Stock	10,000	$0.00	$0.00
Purchase	Common Stock	100,000	$9.11	$911K
holding	Common Stock	--	--	--
holding	Common Stock	--	--	--
holding	Common Stock	--	--	--
holding	Common Stock	--	--	--

Holdings After Transaction: Common Stock — 202,179 shares (Direct); Common Stock — 18,000 shares (Indirect, By Trust #1); Common Stock — 18,000 shares (Indirect, By Trust #2); Common Stock — 18,000 shares (Indirect, By Trust #3); Common Stock — 18,000 shares (Indirect, By Trust #4)

Footnotes (5)

1. F1. The Reporting Person's purchase of shares of Common Stock reported herein was matchable under Section 16(b) of the Securities Exchange Act of 1934, as amended (the "Exchange Act"), to the extent of 8,121 shares, with the Reporting Person's sale of 4,061 shares on March 5, 2025 and 4,060 shares on June 5, 2025 automatically sold by the Reporting Person to satisfy tax withholding obligations in connection with the vesting of restricted stock units granted to the Reporting Person on December 4, 2024. The Reporting Person has paid to the Issuer an aggregate amount of $29,017.22, representing the amount of the profit deemed realized in connection with the short-swing transaction under Section 16(b) of the Exchange Act.
2. F2. The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices within the range of $9.02 to $9.15, 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.
3. F3. This transaction represents a gift by the Reporting Person to a trust established for the benefit of a child of the Reporting Person.
4. F4. These shares of Common Stock are held in a trust for the benefit of a child of the Reporting Person.
5. F5. Includes 127,138 unvested RSUs.

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Form 4 Insider Transactions: What Each Field Means →

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Accepted by SEC EDGAR 07/15/2025 - 05:11 PM EDT Learn about SEC filing dates

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).

1. Name and Address of Reporting Person^*

Cox John

(Last) (First) (Middle)

C/O DYNE THERAPEUTICS, INC.

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
X	Officer (give title below)		Other (specify below)
	CEO & President

3. Date of Earliest Transaction (Month/Day/Year)
07/14/2025

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	07/14/2025		P(1)		100,000	A	$9.11(2)	242,179	D
Common Stock	07/15/2025		G		10,000(3)	D	$0	232,179	D
Common Stock								18,000(3)	I	By Trust #1(4)
Common Stock	07/15/2025		G		10,000(3)	D	$0	222,179	D
Common Stock								18,000(3)	I	By Trust #2(4)
Common Stock	07/15/2025		G		10,000(3)	D	$0	212,179	D
Common Stock								18,000(3)	I	By Trust #3(4)
Common Stock	07/15/2025		G		10,000(3)	D	$0	202,179(5)	D
Common Stock								18,000(3)	I	By Trust #4(4)

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 Reporting Person's purchase of shares of Common Stock reported herein was matchable under Section 16(b) of the Securities Exchange Act of 1934, as amended (the "Exchange Act"), to the extent of 8,121 shares, with the Reporting Person's sale of 4,061 shares on March 5, 2025 and 4,060 shares on June 5, 2025 automatically sold by the Reporting Person to satisfy tax withholding obligations in connection with the vesting of restricted stock units granted to the Reporting Person on December 4, 2024. The Reporting Person has paid to the Issuer an aggregate amount of $29,017.22, representing the amount of the profit deemed realized in connection with the short-swing transaction under Section 16(b) of the Exchange Act.

2. The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices within the range of $9.02 to $9.15, 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.

3. This transaction represents a gift by the Reporting Person to a trust established for the benefit of a child of the Reporting Person.

4. These shares of Common Stock are held in a trust for the benefit of a child of the Reporting Person.

5. Includes 127,138 unvested RSUs.

	/s/ Ron Caponigro, Attorney-in-Fact	07/15/2025
	** 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.