Entity linked to Dyne director sells 84K shares

Dyne Therapeutics, Inc. reported that an entity associated with director Dirk Kersten sold common stock under a pre-arranged trading plan.

Rhea-AI Filing Summary

Dyne Therapeutics, Inc. reported that an entity associated with director Dirk Kersten sold common stock under a pre-arranged trading plan. On June 17 and 18, 2026, ForDyne B.V. executed open-market sales totaling 84,355 shares at weighted average prices of about $20 per share. After these sales, ForDyne held 4,112,218 shares of Dyne Therapeutics common stock indirectly attributed to Kersten. The filing notes the transactions were made pursuant to a Rule 10b5-1 trading plan and that Kersten disclaims beneficial ownership beyond his pecuniary interest.

Insider Trade Summary 10b5-1

Net Seller: 84,355 shares

Net Sell 2 txns

Insider Kersten Dirk

Role Director

Sold 84,355 shs ($1.70M)

Type	Security	Shares	Price	Value
Sale	Common Stock	46,901	$20.0715	$941K
Sale	Common Stock	37,454	$20.1398	$754K

Holdings After Transaction: Common Stock — 4,112,218 shares (Indirect, See footnote)

Footnotes (5)

1. F1. This transaction was made pursuant to a Rule 10b5-1 trading plan adopted by ForDyne B.V. ("ForDyne") on November 11, 2025.
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 $20.00 to $20.43, 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(s) set forth in the footnotes of this Form 4.
3. F3. The shares are held directly by ForDyne. ForDyne is jointly owned by Forbion Capital Fund IV Cooperatief U.A. ("FCF IV") and Forbion Growth Opportunities Fund II Cooperatief U.A. ("FGO II"). Forbion IV Management B.V. ("Forbion Management") may be deemed to have voting and dispositive power over 2,685,848 of the shares of common stock held by ForDyne. Investment decisions with respect to the shares held by ForDyne can be made by FCPM III Services B.V., the director of Forbion Management, which may delegate such powers to its investment committee which may delegate such powers to the authorized representatives of Forbion Management. Messrs. Slootweg, van Osch, Mulder, van Houten, Reithinger and Boorsma (the "Partners") are partners of FCPM III Services B.V., which acts as the investment advisor to the directors of ForDyne. The Reporting Person is a partner of Forbion Management and a member of the investment committee of Forbion Management.
4. F4. (Continued from Footnote 2) Forbion Growth II Management B.V. ("FGO II Management"), the director of FGO II, may be deemed to have voting and dispositive power over 1,426,370 of the shares of common stock held by ForDyne. Investment decisions with respect to the shares held by ForDyne can be made by FCPM III Services B.V., the director of FGO II Management, which may delegate such powers to its investment committee which may delegate such powers to the authorized representatives of FGO II Management. The Partners are partners of FCPM III Services B.V., which acts as the investment advisor to the directors of ForDyne. The Reporting Person is a partner of FGO II Management and a member of the investment committee of FGO II Management. The Reporting Person disclaims beneficial ownership of the shares, except to the extent of his pecuniary interest therein.
5. F5. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices within the range of $20.00 to $20.485, 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(s) set forth in the footnotes of this Form 4.

Key Figures

Total shares sold: 84,355 shares June 18 sale size: 46,901 shares June 17 sale size: 37,454 shares +3 more

6 metrics

Total shares sold 84,355 shares Open-market sales on June 17–18, 2026

June 18 sale size 46,901 shares Common Stock sold at $20.0715 weighted average

June 17 sale size 37,454 shares Common Stock sold at $20.1398 weighted average

Price range (first sale) $20.00–$20.43 Multiple transactions aggregated in weighted average price

Price range (second sale) $20.00–$20.485 Multiple transactions aggregated in weighted average price

Shares after June 18 sale 4,112,218 shares Indirectly held by ForDyne B.V. after transactions

Key Terms

Rule 10b5-1 trading plan, weighted average price, open-market sale, disclaims beneficial ownership, +1 more

5 terms

Rule 10b5-1 trading plan regulatory

"This transaction was made pursuant to a Rule 10b5-1 trading plan adopted by ForDyne B.V."

A Rule 10b5-1 trading plan is a pre-arranged schedule that allows company insiders to buy or sell stock at specific times, even if they have inside information. It helps prevent accusations of unfair trading by making these transactions look planned and transparent, rather than sneaky or illegal.

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.

open-market sale financial

"transaction_action: open-market sale"

An open-market sale is when a shareholder sells existing shares directly on a public exchange to any willing buyer, rather than through a private deal. Think of it like putting goods on a busy market stall where price is set by supply and demand; for investors it matters because such sales increase available supply, can put short-term downward pressure on the stock price, and signal changes in liquidity or investor confidence.

disclaims beneficial ownership regulatory

"The Reporting Person disclaims beneficial ownership of the shares, except to the extent of his pecuniary interest therein."

investment committee financial

"which may delegate such powers to its investment committee which may delegate such powers to the authorized representatives"

An investment committee is a small group of experienced people who set the rules and make the key decisions about what investments to buy, hold, or sell for a fund, pension, or portfolio. Think of them as the steering team that balances goals, potential returns and risk—their choices shape how much money investors are likely to gain or lose and provide consistent oversight so decisions aren’t made impulsively.

FAQ

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

What insider transactions were reported for Dyne Therapeutics (DYN)?

An entity linked to a Dyne Therapeutics director sold 84,355 common shares in two open-market transactions. The sales occurred on June 17 and 18, 2026, at weighted average prices around $20 per share under a pre-arranged Rule 10b5-1 trading plan.

Who actually sold Dyne Therapeutics (DYN) shares in this Form 4?

The shares were sold by ForDyne B.V., an entity associated with director Dirk Kersten. The filing explains ForDyne is jointly owned by Forbion-related funds and that Kersten participates through management roles, while disclaiming beneficial ownership beyond his pecuniary interest.

How many Dyne Therapeutics (DYN) shares does the reporting structure hold after the sale?

Following the reported transactions, ForDyne B.V. held 4,112,218 shares of Dyne Therapeutics common stock. These shares are reported as indirectly owned in the Form 4, reflecting the director’s relationship to ForDyne and related management entities described in the footnotes.

Were the Dyne Therapeutics (DYN) insider sales part of a trading plan?

Yes. The Form 4 states the transactions were made under a Rule 10b5-1 trading plan adopted by ForDyne B.V. on November 11, 2025. Such plans pre-schedule trades, indicating these sales were planned in advance rather than discretionary timing decisions.

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

The reported prices are weighted averages around $20 per share. One sale ranged from $20.00 to $20.43, and the other from $20.00 to $20.485. The filing notes detailed price breakdowns are available upon request from the issuer or the SEC staff.

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

Form 4 Insider Transactions: What Each Field Means →

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Accepted by SEC EDGAR 06/22/2026 - 04:15 PM EDT 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^*

Kersten Dirk

(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)

X	Director		10% Owner
	Officer (give title below)		Other (specify below)

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
06/17/2026

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	06/17/2026		S(1)		37,454	D	$20.1398(2)	4,159,119	I	See footnote(3)(4)
Common Stock	06/18/2026		S(1)		46,901	D	$20.0715(5)	4,112,218	I	See footnote(3)(4)

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. This transaction was made pursuant to a Rule 10b5-1 trading plan adopted by ForDyne B.V. ("ForDyne") on November 11, 2025.

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 $20.00 to $20.43, 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(s) set forth in the footnotes of this Form 4.

3. The shares are held directly by ForDyne. ForDyne is jointly owned by Forbion Capital Fund IV Cooperatief U.A. ("FCF IV") and Forbion Growth Opportunities Fund II Cooperatief U.A. ("FGO II"). Forbion IV Management B.V. ("Forbion Management") may be deemed to have voting and dispositive power over 2,685,848 of the shares of common stock held by ForDyne. Investment decisions with respect to the shares held by ForDyne can be made by FCPM III Services B.V., the director of Forbion Management, which may delegate such powers to its investment committee which may delegate such powers to the authorized representatives of Forbion Management. Messrs. Slootweg, van Osch, Mulder, van Houten, Reithinger and Boorsma (the "Partners") are partners of FCPM III Services B.V., which acts as the investment advisor to the directors of ForDyne. The Reporting Person is a partner of Forbion Management and a member of the investment committee of Forbion Management.

4. (Continued from Footnote 2) Forbion Growth II Management B.V. ("FGO II Management"), the director of FGO II, may be deemed to have voting and dispositive power over 1,426,370 of the shares of common stock held by ForDyne. Investment decisions with respect to the shares held by ForDyne can be made by FCPM III Services B.V., the director of FGO II Management, which may delegate such powers to its investment committee which may delegate such powers to the authorized representatives of FGO II Management. The Partners are partners of FCPM III Services B.V., which acts as the investment advisor to the directors of ForDyne. The Reporting Person is a partner of FGO II Management and a member of the investment committee of FGO II Management. The Reporting Person disclaims beneficial ownership of the shares, except to the extent of his pecuniary interest therein.

5. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices within the range of $20.00 to $20.485, 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(s) set forth in the footnotes of this Form 4.

	/s/ Dirk Kersten	06/22/2026
	** 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)