Tax-driven share sale by Dyne (DYN) CFO Lucera Erick disclosed

Rhea-AI Filing Summary

Dyne Therapeutics, Inc. Chief Financial Officer Lucera Erick reported an open-market sale of 5,727 shares of common stock at a weighted average price of $18.64 per share. According to the disclosure, these shares were sold automatically to satisfy tax withholding obligations tied to restricted stock units that vested on March 31, 2025, under a pre-established agreement treated as a binding contract consistent with Rule 10b5-1. Following the transaction, Erick holds 125,373 shares, including 114,575 unvested restricted stock units, indicating this was a routine, tax-driven event rather than a discretionary trade.

Insider Trade Summary 10b5-1

Net Seller: 5,727 shares ($106,751)

Net Sell 1 txn

Insider Lucera Erick

Role Chief Financial Officer

Sold 5,727 shs ($107K)

Type	Security	Shares	Price	Value
Sale	Common Stock	5,727	$18.64	$107K

Holdings After Transaction: Common Stock — 125,373 shares (Direct)

Footnotes (1)

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 March 31, 2025. 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. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices within the range of $18.24 to $18.84, 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. Includes 114,575 unvested RSUs.

Key Figures

Shares sold: 5,727 shares Weighted average sale price: $18.64 per share Post-transaction holdings: 125,373 shares +2 more

5 metrics

Shares sold 5,727 shares Open-market sale on April 1, 2026 to cover tax withholding

Weighted average sale price $18.64 per share Common stock sale related to RSU tax obligations

Post-transaction holdings 125,373 shares Shares held by CFO after the reported sale

Unvested RSUs 114,575 units Restricted stock units included in post-transaction holdings

Sale price range $18.24–$18.84 per share Range of prices for multiple transactions making up the sale

Key Terms

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

3 terms

restricted stock units financial

"Represents shares automatically sold by the Reporting Person to satisfy tax withholding obligations in connection with the vesting of restricted stock units granted"

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 and the sale does not represent a discretionary trade"

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. These shares were sold in multiple transactions"

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.

Form 4 Insider Transactions: What Each Field Means →

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^*

Lucera Erick

(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 Financial Officer

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
04/01/2026

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	04/01/2026		S(1)		5,727	D	$18.64(2)	125,373(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 March 31, 2025. 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 $18.24 to $18.84, 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 114,575 unvested RSUs.

	/s/ Ron Caponigro, Attorney-in-Fact	04/03/2026
	** 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)

FAQ

What insider transaction did Dyne Therapeutics (DYN) report for CFO Lucera Erick?

Dyne Therapeutics reported CFO Lucera Erick sold 5,727 common shares. The shares were automatically sold to cover tax withholding from vesting restricted stock units, making this a routine, non-discretionary transaction rather than a typical open-market sale based on personal investment decisions.

At what price did the Dyne Therapeutics (DYN) CFO’s shares sell in this Form 4?

The reported weighted average sale price was $18.64 per share. Footnotes note the 5,727 shares were sold in multiple trades between $18.24 and $18.84 per share, and detailed price breakdowns are available to investors on request from the company or regulators.

Why were Dyne Therapeutics (DYN) CFO Lucera Erick’s shares sold according to the filing?

The filing states the shares were sold automatically to satisfy tax withholding obligations from vesting restricted stock units. The sale terms were set in a restricted stock unit agreement treated as a binding contract consistent with Rule 10b5-1, limiting discretionary timing.

How many Dyne Therapeutics (DYN) shares does CFO Lucera Erick hold after this transaction?

After the transaction, CFO Lucera Erick is shown holding 125,373 shares of Dyne Therapeutics common stock. This figure includes 114,575 unvested restricted stock units, indicating a substantial remaining equity position despite the relatively small tax-related sale reported.

Was the Dyne Therapeutics (DYN) CFO’s reported sale under a Rule 10b5-1-type arrangement?

Yes. The disclosure explains the automatic tax-withholding sale was provided for in a restricted stock unit agreement treated as a binding contract consistent with the Rule 10b5-1 affirmative defense, indicating the sale’s timing was pre-arranged rather than a discretionary market decision.