Dyne Therapeutics (DYN) CFO logs automatic 1,448-share tax-related sale

Rhea-AI Filing Summary

Dyne Therapeutics, Inc. Chief Financial Officer Erick Lucera reported an automatic sale of 1,448 shares of common stock. The shares were sold in the open market at a weighted average price of $18.36 per share, within a range of $18.20 to $18.41.

According to the disclosure, this sale was automatically executed to cover tax withholding obligations tied to the vesting of restricted stock units granted on February 12, 2026, under a restricted stock unit agreement characterized as a binding contract consistent with the affirmative defense under Rule 10b5-1. Following the transaction, Lucera holds 123,925 shares directly, including 110,513 unvested restricted stock units.

Insights

Equity compensation and insider-transactions analyst

Small, automatic tax-related sale under RSU agreement; routine activity.

The Dyne Therapeutics CFO, Erick Lucera, reported an automatic sale of 1,448 common shares at a weighted average price of $18.36. The filing states the sale covered tax withholding obligations from vesting restricted stock units granted on February 12, 2026.

The footnote explains this was provided for in a restricted stock unit agreement and treated as a binding contract consistent with the Rule 10b5-1 affirmative defense, meaning the trade was pre-arranged rather than discretionary. Such tax-related mechanics generally carry limited informational value about management’s view of the stock.

After the transaction, Lucera directly holds 123,925 shares, which includes 110,513 unvested RSUs. This indicates the sale represents a small portion of his overall equity exposure, with most value still tied to future company performance through unvested awards.

Insider Trade Summary 10b5-1

Net Seller: 1,448 shares ($26,585)

Net Sell 1 txn

Insider Lucera Erick

Role Chief Financial Officer

Sold 1,448 shs ($27K)

Type	Security	Shares	Price	Value
Sale	Common Stock	1,448	$18.36	$27K

Holdings After Transaction: Common Stock — 123,925 shares (Direct, null)

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 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. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices within the range of $18.20 to $18.41, 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 110,513 unvested RSUs.

Key Figures

Shares sold: 1,448 shares Weighted average sale price: $18.36 per share Shares held after transaction: 123,925 shares +1 more

4 metrics

Shares sold 1,448 shares Automatic sale on May 13, 2026 to cover tax withholding

Weighted average sale price $18.36 per share Open-market sale range $18.20–$18.41

Shares held after transaction 123,925 shares Direct holdings following reported sale

Unvested RSUs 110,513 units Unvested restricted stock units included in post-transaction holdings

Key Terms

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

3 terms

restricted stock units financial

"tax withholding obligations in connection with the 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.

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.

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.

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)
05/13/2026

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	05/13/2026		S(1)		1,448	D	$18.36(2)	123,925(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 $18.20 to $18.41, 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 110,513 unvested RSUs.

	/s/ Ron Caponigro, Attorney-in-Fact	05/14/2026
	** 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 did Dyne Therapeutics (DYN) CFO Erick Lucera report in this Form 4 filing?

The CFO reported an automatic sale of 1,448 Dyne Therapeutics common shares. The shares were sold to cover tax withholding on vesting restricted stock units granted on February 12, 2026, under a pre-arranged restricted stock unit agreement.

At what price were the Dyne Therapeutics (DYN) shares sold by the CFO?

The disclosed sale used a weighted average price of $18.36 per share. The shares were sold in multiple transactions within a price range of $18.20 to $18.41, and full trade details are available upon request from the company or regulators.

Was the Dyne Therapeutics (DYN) CFO’s share sale a discretionary trade?

The sale was not discretionary; it was automatic under a restricted stock unit agreement. The filing states it was a binding contract consistent with the Rule 10b5-1 affirmative defense, executed to satisfy tax withholding obligations on RSU vesting.

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

After the transaction, the CFO directly holds 123,925 Dyne Therapeutics shares. This total includes 110,513 unvested restricted stock units, meaning a substantial portion of his equity exposure remains tied to unvested long-term awards in the company.

What do the unvested RSUs in this Dyne Therapeutics (DYN) Form 4 indicate?

The filing notes 110,513 unvested restricted stock units held by the CFO. Unvested RSUs typically vest over time, aligning executive incentives with company performance and encouraging retention, as value is realized only if vesting conditions are met.