Dyne Therapeutics (DYN) director Brian Posner buys 2,000 shares in open market

Rhea-AI Filing Summary

Dyne Therapeutics director Brian S. Posner bought additional shares of the company. On this Form 4, he reported an open-market purchase of 2,000 shares of Common Stock at a price of $18.21 per share on May 26, 2026. After this transaction, he directly owns 20,000 shares.

Insider Trade Summary

Net Buyer: 2,000 shares ($36,420)

Net Buy 1 txn

Insider Posner Brian S

Role null

Bought 2,000 shs ($36K)

Type	Security	Shares	Price	Value
Purchase	Common Stock	2,000	$18.21	$36K

Holdings After Transaction: Common Stock — 20,000 shares (Direct, null)

Footnotes (1)

Key Figures

Shares purchased: 2,000 shares Purchase price: $18.21 per share Post-transaction holdings: 20,000 shares

3 metrics

Shares purchased 2,000 shares Open-market purchase of Common Stock on May 26, 2026

Purchase price $18.21 per share Price paid for 2,000 Common Stock shares

Post-transaction holdings 20,000 shares Total Common Stock directly owned after the transaction

Key Terms

open-market purchase, Common Stock, Form 4

3 terms

open-market purchase financial

"transaction_action: "open-market purchase" for 2,000 Common Stock shares"

An open-market purchase is when an investor or a company buys shares on a public stock exchange at the going market price, rather than through a private deal. It matters to investors because these purchases change how many shares are available, can push the stock price up or signal confidence from large buyers, and often affect per-share metrics like earnings—think of it like someone buying lots of apples off a grocery shelf, reducing supply and potentially raising the price.

Common Stock financial

"security_title: "Common Stock" in the reported transaction"

Common stock represents ownership shares in a company, giving investors a stake in its success and a say in important decisions through voting rights. It is the most common type of stock traded on markets and can provide income through dividends, as well as potential for value growth. For investors, holding common stock means sharing in the company’s profits and risks.

Form 4 regulatory

"INSIDER FILING DATA (Form 4) describing the insider transaction"

Form 4 is a official document that company insiders, such as executives or major shareholders, file with regulators whenever they buy or sell company shares. It provides transparency about how those with inside knowledge are trading, helping investors see if insiders are confident in the company's prospects or may be selling for personal reasons. This information can influence investor decisions by revealing insiders' perspectives on the company's value.

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).

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^*

Posner Brian S

(Last) (First) (Middle)

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)
05/26/2026

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	05/26/2026		P		2,000	A	$18.21	20,000	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:

	/s/ Ron Caponigro, Attorney-in-Fact	05/28/2026
	** 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 insider transaction did Dyne Therapeutics (DYN) report for Brian S. Posner?

Dyne Therapeutics reported that director Brian S. Posner made an open-market purchase of 2,000 shares of Common Stock. The transaction was recorded on a Form 4 and reflects direct ownership following the trade.

At what price did Brian S. Posner buy Dyne Therapeutics (DYN) shares?

Brian S. Posner purchased Dyne Therapeutics Common Stock at $18.21 per share. This price applies to the 2,000 shares acquired in the open-market transaction reported in the Form 4 filing for May 26, 2026.

How many Dyne Therapeutics (DYN) shares does Brian S. Posner own after this Form 4?

After the reported transaction, Brian S. Posner directly owns 20,000 shares of Dyne Therapeutics Common Stock. This total includes the 2,000 shares he bought in the open-market purchase disclosed in the Form 4.

Was the Dyne Therapeutics (DYN) insider transaction a purchase or a sale?

The Dyne Therapeutics insider transaction by Brian S. Posner was a purchase. The Form 4 identifies it as an open-market acquisition of 2,000 Common Stock shares, coded as a purchase rather than a sale or other type of disposition.

Does the Form 4 for Dyne Therapeutics (DYN) involve derivative securities?

No, the reported Form 4 transaction involves only non-derivative Common Stock. The filing shows a single open-market purchase of 2,000 shares and lists no outstanding or transacted derivative securities in the derivativeSummary section.