[Form 4] Dyne Therapeutics, Inc. Insider Trading Activity

Rhea-AI Filing Summary

Dyne Therapeutics insider sale by Chief Medical Officer Kerr Douglas: On 09/04/2025 and 09/05/2025 Mr. Douglas reported automatic sales of common stock to satisfy tax withholding for vested restricted stock units. A total of 4,425 shares were sold (3,552 shares on 09/04 at a weighted-average price of $13.27 and 873 shares on 09/05 at $13.41). These sales were executed under binding RSU agreements consistent with Rule 10b5-1 affirmative defense and are described as automatic, not discretionary. After the reported transactions the reporting person beneficially owned 88,390 shares, which includes 74,625 unvested RSUs.

Positive

• Disclosure clarity: Form specifies dates, share counts, weighted-average price range and the Rule 10b5-1 affirmative defense.
• Transactions were non-discretionary: Sales executed automatically to satisfy tax withholding for RSU vesting.
• Transparency on unvested compensation: Filing discloses that 74,625 RSUs remain unvested.

Negative

• Insider sold 4,425 shares: While routine, sales modestly reduce insider's vested stake.
• Weighted-average price only provided for one sale: Detailed price-per-lot breakdown requires request to the company or SEC staff.

Insights

Securities Analyst

TL;DR: Routine, non-discretionary withholding sales tied to RSU vesting; not a market-moving event.

The reported transactions are clearly explained as automatic sales to satisfy tax withholding obligations for RSUs vested on two separate grant dates. The use of a binding RSU agreement and reference to Rule 10b5-1 supports that these were pre-planned, non-discretionary disposals. Aggregate shares sold (4,425) and the post-transaction beneficial ownership (88,390 shares, including 74,625 unvested RSUs) suggest the insider retains significant unvested compensation tied to future service or performance. For investors, this filing signals routine compensation mechanics rather than a proactive liquidity event by management.

Corporate Governance Expert

TL;DR: Disclosure aligns with governance best practices; documentation of weighted-average pricing is appropriate.

The Form 4 provides necessary disclosure: transaction dates, share counts, weighted-average price range for the larger sale, and an undertaking to supply a price breakdown on request. The signature by an attorney-in-fact is properly executed. Including the number of unvested RSUs improves transparency about the nature of the insider's holdings. This filing raises no governance red flags and fits standard executive compensation settlement practices.

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).

X

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^*

Kerr Douglas

(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)

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

3. Date of Earliest Transaction (Month/Day/Year)
09/04/2025

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	09/04/2025		S(1)		3,552	D	$13.27(2)	89,263	D
Common Stock	09/05/2025		S(3)		873	D	$13.41	88,390(4)	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. Represents shares 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 September 3, 2024. The automatic sale of the Reporting Person's shares is provided for in a restricted stock unit agreement constituting a "binding contract" consistent with the affirmative defense to liability under Rule 10b5-1 and the sale does not represent a discretionary trade by the Reporting Person.

2. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices within the range of $13.07 to $13.50, 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. Represents shares 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 automatic sale of the Reporting Person's shares is provided for in a restricted stock unit agreement constituting a "binding contract" consistent with the affirmative defense to liability under Rule 10b5-1 and the sale does not represent a discretionary trade by the Reporting Person.

4. Includes 74,625 unvested RSUs.

	/s/ Ron Caponigro, Attorney-in-Fact	09/08/2025
	** 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.

FAQ

What did Dyne Therapeutics (DYN) insider Kerr Douglas report on Form 4?

The filing reports automatic sales of 3,552 shares on 09/04/2025 and 873 shares on 09/05/2025 to satisfy tax withholding on vested RSUs.

Why were the shares sold by the reporting person?

The sales were automatic pursuant to RSU agreements to satisfy tax withholding obligations and are described as non-discretionary under a Rule 10b5-1 arrangement.

What prices were the shares sold at?

The 09/04 sale has a weighted-average price of $13.27 (range $13.07–$13.50); the 09/05 sale price was $13.41.

How many shares does the reporting person own after these transactions?

The reporting person beneficially owned 88,390 shares following the reported transactions, which includes 74,625 unvested RSUs.

Does this Form 4 indicate discretionary insider selling?

No; the filing states the sales were automatic under binding RSU agreements and not discretionary trades.