Dyne CCO auto-sells 1,085 shares for tax withholding

Dyne Therapeutics’ Chief Commercial Officer reported automatic tax-withholding share sales tied to RSU vesting under a Rule 10b5-1 plan.

Rhea-AI Filing Summary

Dyne Therapeutics, Inc. (DYN) reported that Chief Commercial Officer Johanna Friedl-Naderer sold a total of 1,085 shares of common stock on September 4 and September 8, 2026. The filing states these were automatic sales to satisfy tax withholding obligations upon vesting of restricted stock units under a Rule 10b5-1 binding contract, and are not discretionary trades. The company also reports that her equity position includes 102,966 unvested RSUs.

Insider Trade Summary 10b5-1

Net Seller: 1,085 shares

Net Sell 2 txns

Insider Friedl-Naderer Johanna

Role Chief Commercial Officer

Sold 1,085 shs ($25K)

Type	Security	Shares	Price	Value
Sale	Common Stock F3, F4, F5	185	$18.88	$3K
Sale	Common Stock F1, F2	900	$24.35	$22K

Holdings After Transaction: Common Stock — 152,897 shares (Direct)

Footnotes (5)

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 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. 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 $24.29 to $24.50, 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. F3. 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. F4. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices within the range of $18.77 to $18.92, 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.
5. F5. Includes 102,966 unvested RSUs.

Key Figures

Shares sold September 4, 2026: 900 shares Weighted average sale price September 4, 2026: $24.35 per share Shares sold September 8, 2026: 185 shares +3 more

6 metrics

Shares sold September 4, 2026 900 shares Automatic sale to satisfy tax withholding on RSU vesting

Weighted average sale price September 4, 2026 $24.35 per share Sold in multiple transactions within a $24.29–$24.50 range

Shares sold September 8, 2026 185 shares Automatic sale to satisfy tax withholding on RSU vesting

Weighted average sale price September 8, 2026 $18.88 per share Sold in multiple transactions within a $18.77–$18.92 range

Total shares sold 1,085 shares Combined across both reported transactions

Unvested RSUs held 102,966 RSUs Unvested restricted stock units included in the reporting person’s holdings

Key Terms

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

4 terms

Rule 10b5-1 regulatory

"agreement 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.

restricted stock units financial

"vesting of restricted stock units granted to the Reporting Person"

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.

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

"shares automatically sold by the Reporting Person to satisfy tax withholding obligations"

FAQ

What insider transactions did Dyne Therapeutics (DYN) report for Johanna Friedl-Naderer?

The Chief Commercial Officer reported two sales totaling 1,085 shares of Dyne Therapeutics common stock on September 4, 2026 and September 8, 2026, both described as automatic sales to cover tax withholding on vesting RSUs.

Were the DYN insider sales by the Chief Commercial Officer discretionary trades?

No. The filing states the shares were automatically sold to satisfy tax withholding obligations in connection with RSU vesting, under a restricted stock unit agreement that is a “binding contract” consistent with the Rule 10b5-1 affirmative defense, and that the sales do not represent discretionary trades.

At what prices were the Dyne Therapeutics (DYN) shares sold by the CCO?

On September 4, 2026, 900 shares were sold at a weighted average price of $24.35, within a range of $24.29 to $24.50. On September 8, 2026, 185 shares were sold at a weighted average price of $18.88, within a range of $18.77 to $18.92.

How many Dyne Therapeutics (DYN) shares were sold in each transaction by the Chief Commercial Officer?

The reporting person sold 900 shares of common stock on September 4, 2026 and 185 shares on September 8, 2026, for a combined total of 1,085 shares reported as sold.

What ongoing equity holdings does the Dyne Therapeutics (DYN) Chief Commercial Officer have after these transactions?

The filing notes that the reporting person’s holdings include 102,966 unvested restricted stock units (RSUs). A specific total share count after the transactions is not provided in the reported data, but these unvested RSUs are part of her continuing equity awards.

Were the reported Dyne Therapeutics (DYN) insider sales made under a Rule 10b5-1 plan?

Yes. The Form 4 indicates the transactions were under an affirmative Rule 10b5-1 trading arrangement, and the footnotes describe each automatic sale as provided for in a restricted stock unit agreement that is a “binding contract” consistent with the Rule 10b5-1 affirmative defense.

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Available on EDGAR 09/08/2026 - 04:16 PM Accepted by SEC EDGAR 09/08/2026 - 04:15 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^*

Friedl-Naderer Johanna

(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 Commercial Officer

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
09/04/2026

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	09/04/2026		S(1)		900	D	$24.35(2)	153,082	D
Common Stock	09/08/2026		S(3)		185	D	$18.88(4)	152,897(5)	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 $24.29 to $24.50, 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. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices within the range of $18.77 to $18.92, 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.

5. Includes 102,966 unvested RSUs.

	/s/ Ron Caponigro, Attorney-in-Fact	09/08/2026
	** 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)