Dyne CMO sells 1,556 shares to cover taxes

Dyne Therapeutics, Inc. reported that Chief Medical Officer Douglas Kerr sold 1,556 shares of common stock on August 13, 2026 at a weighted average price of $26.28 per share.

Rhea-AI Filing Summary

Dyne Therapeutics, Inc. reported that Chief Medical Officer Douglas Kerr sold 1,556 shares of common stock on August 13, 2026 at a weighted average price of $26.28 per share. The shares were automatically sold to satisfy tax withholding obligations arising from the vesting of previously granted restricted stock units under a pre-arranged agreement treated as a Rule 10b5-1 "binding contract", so the transaction did not represent a discretionary trade. Following this sale, Kerr directly held 167,599 shares of common stock, including 140,001 unvested RSUs.

Insider Trade Summary 10b5-1

Net Seller: 1,556 shares

Net Sell 1 txn

Insider Kerr Douglas

Role Chief Medical Officer

Sold 1,556 shs ($41K)

Type	Security	Shares	Price	Value
Sale	Common Stock F1, F2, F3	1,556	$26.28	$41K

Holdings After Transaction: Common Stock — 167,599 shares (Direct)

Footnotes (3)

1. F1. 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 February 12, 2026. 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. F2. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices within the range of $26.17 to $26.39, 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. Includes 140,001 unvested RSUs.

Key Figures

Shares sold: 1,556 shares Weighted average sale price: $26.28 per share Price range of sales: $26.17 to $26.39 +3 more

6 metrics

Shares sold 1,556 shares Common stock automatically sold on August 13, 2026 to satisfy tax withholding

Weighted average sale price $26.28 per share Multiple sale transactions within a price range of $26.17 to $26.39

Price range of sales $26.17 to $26.39 Range of prices for individual trades included in the weighted average

Shares held after transaction 167,599 shares Direct common stock holdings following the August 13, 2026 sale

Unvested RSUs included 140,001 RSUs Unvested restricted stock units included in post-transaction holdings

Net shares sold in filing 1,556 shares Net-sell direction based on transaction summary for this Form 4

Key Terms

restricted stock units, Rule 10b5-1, weighted average price, tax withholding obligations

4 terms

restricted stock units financial

"Includes 140,001 unvested RSUs."

Restricted stock units are a type of company reward where employees are promised shares of stock, but they only fully own these shares after meeting certain conditions, like staying with the company for a set time. They matter because they can become valuable assets and are often used to motivate employees to help the company succeed.

Rule 10b5-1 regulatory

"constituting a "binding contract" consistent with the affirmative defense to liability under Rule 10b5-1"

Rule 10b5-1 is a regulation that allows company insiders to buy or sell their shares at predetermined times, even if they have access to non-public information. It acts like setting a schedule in advance for transactions, helping prevent accusations of unfair trading. This rule provides a way for insiders to plan trades transparently, giving investors confidence that these transactions are not based on hidden information.

weighted average price financial

"The price reported in Column 4 is a weighted average price."

Weighted average price is the average price of a security where each trade or component is counted according to its size, so bigger trades pull the average more than smaller ones. Think of it like calculating the average cost of a grocery haul where items you bought more of have greater influence on the final per-item cost. Investors use it to understand the true average price paid or received, judge execution quality, and compare trading performance against market movement.

tax withholding obligations financial

"sold by the Reporting Person to satisfy tax withholding obligations in connection with the vesting"

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What insider transaction did Dyne Therapeutics (DYN) disclose for Douglas Kerr?

Dyne Therapeutics disclosed that Chief Medical Officer Douglas Kerr sold 1,556 shares of common stock on August 13, 2026. The sale was to cover tax withholding obligations related to vesting restricted stock units.

At what price were Douglas Kerr's Dyne Therapeutics (DYN) shares sold?

The reported sale used a weighted average price of $26.28 per share. The footnote explains shares were sold in multiple trades between $26.17 and $26.39, and detailed breakdowns are available upon request.

How many Dyne Therapeutics (DYN) shares does Douglas Kerr hold after this Form 4 transaction?

After the reported sale, Douglas Kerr directly held 167,599 shares of Dyne Therapeutics common stock. This total includes 140,001 unvested restricted stock units (RSUs), which remain subject to vesting conditions.

Was Douglas Kerr’s Dyne Therapeutics (DYN) share sale a discretionary trade?

The sale was not a discretionary trade. Shares were automatically sold to satisfy tax withholding on RSU vesting under an agreement treated as a Rule 10b5-1 binding contract, indicating it was pre-arranged.

Why did Douglas Kerr sell Dyne Therapeutics (DYN) shares in this Form 4 filing?

The filing states the 1,556 shares were sold automatically to cover tax withholding obligations from the vesting of restricted stock units granted on February 12, 2026, rather than as a discretionary liquidation of holdings.

What does the Rule 10b5-1 reference mean in the Dyne Therapeutics (DYN) Form 4?

The filing notes the RSU agreement is a "binding contract" consistent with Rule 10b5-1’s affirmative defense. This means the sale followed a pre-established plan, reducing the significance of trade timing as an information signal.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Available on EDGAR 08/17/2026 - 04:08 PM Accepted by SEC EDGAR 08/17/2026 - 04:08 PM 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).

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 MASSACHUSETTS 02451

(City) (State) (Zip)

UNITED STATES

(Country)

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

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
08/13/2026

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

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

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

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	08/13/2026		S(1)		1,556	D	$26.28(2)	167,599(3)	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 February 12, 2026. 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 $26.17 to $26.39, 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. Includes 140,001 unvested RSUs.

	/s/ Dan Wilson, Attorney-in-Fact	08/17/2026
	** 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.
* Form 4: SEC 1474 (03-26)