[Form 4] Dyne Therapeutics, Inc. Insider Trading Activity

Rhea-AI Filing Summary

Dyne Therapeutics, Inc. director-associated entity ForDyne B.V. reported open-market sales of a total of 99,613 shares of common stock over two days. The trades, made on April 15–16, 2026, were executed under a Rule 10b5-1 trading plan adopted by ForDyne on November 11, 2025.

Shares were sold at weighted average prices of $20.2718 for 81,840 shares, $20.0575 for 6,657 shares, and $21.1039 for 11,116 shares, across specified intraday price ranges. Following these sales, entities associated with ForDyne continued to hold 4,544,773 shares of Dyne Therapeutics common stock indirectly. The reporting person disclaims beneficial ownership beyond any pecuniary interest.

Insights

Equity ownership & governance analyst

Pre-planned, modest insider-linked sales with large indirect stake remaining.

The filing shows ForDyne B.V., an entity linked to Dyne Therapeutics director Dirk Kersten, selling 99,613 shares of common stock in three open-market transactions. All trades were executed under a Rule 10b5-1 trading plan, indicating they were pre-scheduled rather than opportunistic.

After these sales, entities associated with ForDyne still hold 4,544,773 Dyne shares indirectly. The reporting person explicitly disclaims beneficial ownership beyond any pecuniary interest, suggesting this is primarily a fund-level portfolio move. With a substantial position remaining and no derivative exercises disclosed, the activity appears routine and administrative rather than thesis-changing.

Insider Trade Summary 10b5-1

Net Seller: 99,613 shares ($2,027,158)

Net Sell 3 txns

Insider Kersten Dirk

Role Director

Sold 99,613 shs ($2.03M)

Type	Security	Shares	Price	Value
Sale	Common Stock	11,116	$21.1039	$235K
Sale	Common Stock	6,657	$20.0575	$134K
Sale	Common Stock	81,840	$20.2718	$1.66M

Holdings After Transaction: Common Stock — 4,551,430 shares (Indirect, See footnote)

Footnotes (1)

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 $20.00 to $20.99, 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 3,118,403 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 $21.00 to $21.345, 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 $20.00 to $20.16, 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.

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^*

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)
04/15/2026

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	04/15/2026		S(1)		81,840	D	$20.2718(2)	4,562,546	I	See footnote(3)(4)
Common Stock	04/16/2026		S(1)		11,116	D	$21.1039(5)	4,551,430	I	See footnote(3)(4)
Common Stock	04/16/2026		S(1)		6,657	D	$20.0575(6)	4,544,773	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 $20.99, 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 3,118,403 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 $21.00 to $21.345, 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 $20.00 to $20.16, 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	04/17/2026
	** 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)