Dyne Therapeutics (DYN) director-affiliated fund sells 263,962 shares under 10b5-1 plan

Filing Impact

(Very High)

Filing Sentiment

(Very Negative)

Form Type

Rhea-AI Filing Summary

Dyne Therapeutics director-affiliated entity reports stock sales. An entity associated with director Dirk Kersten, ForDyne B.V., sold a total of 263,962 shares of Dyne Therapeutics common stock in open-market transactions on June 22–23, 2026 at weighted average prices around $20–$21 per share. The trades were executed under a pre-arranged Rule 10b5-1 trading plan adopted by ForDyne on November 11, 2025. Following these transactions, the entity reported holding 3,848,256 shares indirectly, and Kersten disclaims beneficial ownership except for any pecuniary interest.

Insights

Pre-planned fund-level sales reduce an indirect stake but leave a large position.

The filing shows that ForDyne B.V., an investment vehicle associated with director Dirk Kersten, sold 263,962 shares of Dyne Therapeutics common stock in open-market trades at weighted average prices a little above $20 per share.

These sales were executed under a Rule 10b5-1 trading plan adopted on November 11, 2025, indicating they were pre-scheduled rather than opportunistic. All reported holdings are indirect, and Kersten formally disclaims beneficial ownership beyond any pecuniary interest.

After the transactions, ForDyne still reports 3,848,256 shares, so the sales represent only a portion of the overall position. From a governance and signal perspective, this looks like routine portfolio management by an investment fund rather than a transformative change in insider alignment.

Insider Trade Summary 10b5-1

Net Seller: 263,962 shares ($5,464,611)

Net Sell 3 txns

Insider Kersten Dirk

Role null

Sold 263,962 shs ($5.46M)

Type	Security	Shares	Price	Value
Sale	Common Stock	71,629	$21.0357	$1.51M
Sale	Common Stock	1,657	$21.4742	$36K
Sale	Common Stock	190,676	$20.5703	$3.92M

Holdings After Transaction: Common Stock — 3,849,913 shares (Indirect, See footnote)

Footnotes (1)

This transaction was made pursuant to a Rule 10b5-1 trading plan adopted by ForDyne B.V. ("ForDyne") on November 11, 2025. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices within the range of $20.13 to $20.97, 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. 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 2,421,886 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. (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. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices within the range of $20.45 to $21.44, 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. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices within the range of $21.45 to $21.495, 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

Shares sold: 263,962 shares First sale block: 190,676 shares Second sale block: 71,629 shares +5 more

8 metrics

Shares sold 263,962 shares Total Dyne Therapeutics common stock sold on June 22–23, 2026

First sale block 190,676 shares Open-market sale on June 22, 2026 at $20.5703 per share

Second sale block 71,629 shares Open-market sale on June 23, 2026 at $21.0357 per share

Third sale block 1,657 shares Open-market sale on June 23, 2026 at $21.4742 per share

Holdings after transactions 3,848,256 shares Indirect ForDyne B.V. position after June 23, 2026 trades

Price range (June 22 block) $20.13–$20.97 Weighted-average sale range noted in footnote for one trade group

Price range (June 23 block 1) $20.45–$21.44 Weighted-average sale range noted in footnote for one trade group

Price range (June 23 block 2) $21.45–$21.495 Weighted-average sale range noted in footnote for one trade group

Key Terms

Rule 10b5-1 trading plan, weighted average price, voting and dispositive power, 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.

voting and dispositive power financial

"Forbion Management may be deemed to have voting and dispositive power over 2,421,886 of the shares of common stock held by ForDyne."

beneficial ownership regulatory

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

Beneficial ownership means the person or entity that actually enjoys the benefits of owning shares or other assets — such as receiving dividends, voting rights, or price gains — even if the legal title is held in another name. For investors it matters because knowing who truly controls and profits from a company reveals who can influence decisions, exposes potential conflicts of interest or hidden concentration of power, and affects transparency and risk in the stock.

pecuniary interest financial

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

See more from StockTitan in Google Search and AI answers. Adds StockTitan as a preferred source · opens Google

Add on Google

Form 4 Insider Transactions: What Each Field Means →

Available on EDGAR 06/24/2026 - 04:27 PM Accepted by SEC EDGAR 06/24/2026 - 04:27 PM

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).

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)
06/22/2026

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)
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	Code	V	Amount	(A) or (D)	Price		6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
Common Stock	06/22/2026		S⁽¹⁾		190,676	D	$20.5703⁽²⁾	3,921,542	I	See footnote⁽³⁾⁽⁴⁾
Common Stock	06/23/2026		S⁽¹⁾		71,629	D	$21.0357⁽⁵⁾	3,849,913	I	See footnote⁽³⁾⁽⁴⁾
Common Stock	06/23/2026		S⁽¹⁾		1,657	D	$21.4742⁽⁶⁾	3,848,256	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)
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)	Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	8. Price of Derivative Security (Instr. 5)		10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)

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 $20.13 to $20.97, 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 2,421,886 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 $20.45 to $21.44, 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.

6. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices within the range of $21.45 to $21.495, 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	06/24/2026
	** 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)

Source: View Original Filing on SEC EDGAR

FAQ

What insider transaction did Dyne Therapeutics (DYN) disclose in this Form 4?

Dyne Therapeutics disclosed that ForDyne B.V., an entity associated with director Dirk Kersten, sold 263,962 shares of common stock in open-market transactions. These trades occurred on June 22–23, 2026 at weighted average prices slightly above $20 per share.

Who actually sold Dyne Therapeutics shares in the Kersten Form 4 filing?

The shares were sold by ForDyne B.V., which holds Dyne Therapeutics stock indirectly for funds managed by Forbion entities. Director Dirk Kersten is a partner in those management entities but disclaims beneficial ownership beyond his pecuniary interest in the funds.

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

Yes. The filing states the transactions were made pursuant to a Rule 10b5-1 trading plan adopted by ForDyne B.V. on November 11, 2025. Such plans pre-schedule trades, which typically makes their timing less informative about short-term company prospects.

How many Dyne Therapeutics shares does the reporting entity hold after these sales?

After the reported transactions, ForDyne B.V. holds 3,848,256 shares of Dyne Therapeutics common stock indirectly. This indicates that, despite selling 263,962 shares, the entity continues to maintain a substantial remaining position in the company.

At what prices were the Dyne Therapeutics (DYN) shares sold in this Form 4?

The Form 4 reports weighted average sale prices near $20–$21 per share. Footnotes explain that individual trades occurred in ranges including $20.13–$20.97, $20.45–$21.44, and $21.45–$21.495, with detailed breakdowns available on request.

Does the Dyne Therapeutics Form 4 suggest a change in Dirk Kersten’s control over the shares?

The filing emphasizes that the shares are held by ForDyne B.V. and related funds, and Kersten disclaims beneficial ownership except for his pecuniary interest. Investment and voting decisions are described as made through fund management entities, not directly by Kersten personally.