688K Dyne Therapeutics (DYN) shares sold by ForDyne fund under 10b5-1 plan

Rhea-AI Filing Summary

Dyne Therapeutics, Inc. director-associated entity ForDyne B.V. reported open-market sales of a total of 688,788 shares of Dyne common stock over March 9–10, 2026. The sales were executed at weighted average prices, with disclosed ranges from $17.50 to $20.03 per share. Following these transactions, entities associated with the reporting person continued to hold 4,774,058 Dyne shares indirectly. The filing notes that the March 2026 sales were made under a pre-arranged Rule 10b5-1 trading plan adopted by ForDyne on November 11, 2025, indicating the trades were scheduled in advance rather than timed discretionarily.

Insights

Equity ownership & insider-trading analyst

Pre-planned fund-level sales reduce exposure but leave a large remaining stake.

The transactions show entities associated with Dyne director Dirk Kersten selling 688,788 Dyne shares through ForDyne B.V. in open-market trades. Prices ranged from $17.50 to $20.03 per share, reflecting normal trading levels rather than a single block sale.

The filing specifies these sales were made under a Rule 10b5-1 trading plan adopted on November 11, 2025. Such plans are set up in advance and typically indicate routine portfolio management by the investment funds rather than reactive trading based on near-term information.

After the reported sales, the entities associated with the reporting person still indirectly hold 4,774,058 Dyne shares. This remaining position suggests continued, substantial exposure to Dyne’s equity, and the Form 4 does not show any option exercises or derivative positions being altered in this period.

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
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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 MA 02451

(City) (State) (Zip)

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)

3. Date of Earliest Transaction (Month/Day/Year)
03/09/2026

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

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	03/09/2026		S(1)		177,690	D	$17.7218(2)	5,285,156	I	See footnote(3)(4)
Common Stock	03/10/2026		S(1)		9,482	D	$18.2121(5)	5,275,674	I	See footnote(3)(4)
Common Stock	03/10/2026		S(1)		219,758	D	$19.325(6)	5,055,916	I	See footnote(3)(4)
Common Stock	03/10/2026		S(1)		281,858	D	$19.8001(7)	4,774,058	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 $17.50 to $18.21, 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 3,347,688 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 $17.595 to $18.59, inclusive.

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 $18.61 to $19.605, inclusive.

7. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices within the range of $19.61 to $20.03, inclusive.

	/s/ Dirk Kersten	03/11/2026
	** 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.

FAQ

What insider transactions did Dyne Therapeutics (DYN) report in this Form 4?

The Form 4 shows entities linked to director Dirk Kersten, through ForDyne B.V., sold a total of 688,788 Dyne common shares. These were open-market sales on March 9–10, 2026, executed at various weighted average prices.

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

The reported Dyne shares were sold at weighted average prices within disclosed ranges from $17.50 to $20.03 per share. The filing notes multiple individual trades inside these bands and offers to provide full price breakdowns upon request.

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

Yes. The filing states the March 2026 sales were made under a Rule 10b5-1 trading plan adopted by ForDyne B.V. on November 11, 2025. Such pre-arranged plans usually indicate scheduled, programmatic selling rather than opportunistic timing.

How many Dyne Therapeutics (DYN) shares remain held after these reported sales?

After completing the March 10, 2026 transactions, entities associated with the reporting person continued to indirectly hold 4,774,058 Dyne common shares. This figure reflects the position following the final reported open-market sale in the Form 4.

Who actually holds the Dyne Therapeutics (DYN) shares involved in this Form 4?

The shares are held directly by ForDyne B.V., which is jointly owned by Forbion investment funds and managed via affiliated management entities. The reporting person is a partner in these managers and disclaims beneficial ownership beyond any pecuniary interest.

Does this Dyne Therapeutics (DYN) Form 4 involve options or other derivatives?

No. The reported transactions all involve common stock and are coded as non-derivative open-market sales. The derivative section of the filing shows no option exercises or other derivative transactions during this reporting period.