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

Rhea-AI Filing Summary

Dyne Therapeutics, Inc. (DYN) director Brian S. Posner received a stock option grant on 10/01/2025 for 70,000 shares with an exercise price of $12.50. The option is exercisable for underlying common stock and shows 70,000 shares beneficially owned following the grant, reported as direct ownership. The option vests over three years in equal monthly installments through 10/01/2028, giving the director continuing equity alignment over that period. The Form 4 was signed on 10/02/2025 by an attorney-in-fact on behalf of the reporting person.

Positive

• 70,000 option grant establishes direct equity ownership for the director
• 3-year monthly vesting aligns director incentives with long-term shareholder value
• Transaction was reported promptly on Form 4 (filed 10/02/2025)

Negative

• None.

Insights

Corporate Governance Expert

Director received a standard multi-year option grant; aligns interests with shareholders.

The filing documents a single equity award: a 70,000-share option at an exercise price of $12.50 granted on 10/01/2025. The award vests monthly over three years through 10/01/2028, which phases the director's ownership increase over time rather than immediately.

This structure is commonly used to retain directors and tie compensation to long-term share performance; the Form 4 reports the resulting direct beneficial ownership of 70,000 shares after the grant.

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

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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^*

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)
10/01/2025

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

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
Stock option (right to buy)	$12.5	10/01/2025		A		70,000		(1)	09/30/2035	Common Stock	70,000	$0.00	70,000	D

Explanation of Responses:

1. The option was granted on October 1, 2025. The shares underlying the option are scheduled to vest over three years in equal monthly installments through October 1, 2028.

	/s/ Ron Caponigro, Attorney-in-Fact	10/02/2025
	** 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 transaction did Brian S. Posner report on the Form 4 for DYN?

The Form 4 reports a grant of a stock option for 70,000 shares at an exercise price of $12.50, granted on 10/01/2025.

How does the option vest and when will it be fully vested?

The option vests in equal monthly installments over three years, becoming fully vested on 10/01/2028.

How many shares does the reporting person beneficially own after the grant?

The filing shows the reporting person beneficially owns 70,000 shares following the reported transaction.

What is the exercise price of the option reported on the Form 4?

The conversion/exercise price of the reported option is $12.50 per share.

When was the Form 4 signed and filed?

The Form 4 was signed by an attorney-in-fact on behalf of the reporting person and dated 10/02/2025.