Director at Dyne Therapeutics (DYN) adds 2,000 common shares

Rhea-AI Filing Summary

Dyne Therapeutics, Inc. director Brian S. Posner reported an open-market purchase of 2,000 shares of common stock. The shares were bought at a weighted average price of $17.08 per share on this transaction date, with individual trade prices ranging from $17.06 to $17.10. Following this purchase, Posner directly holds 15,500 Dyne Therapeutics shares.

Insider Trade Summary

Net Buyer: 2,000 shares ($34,160)

Net Buy 1 txn

Insider Posner Brian S

Role Director

Bought 2,000 shs ($34K)

Type	Security	Shares	Price	Value
Purchase	Common Stock	2,000	$17.08	$34K

Holdings After Transaction: Common Stock — 15,500 shares (Direct)

Footnotes (1)

1. [object Object]

Key Figures

Shares purchased: 2,000 shares Weighted average price: $17.08 per share Trade price range: $17.06–$17.10 per share +1 more

4 metrics

Shares purchased 2,000 shares Open-market purchase of common stock

Weighted average price $17.08 per share Average price for the 2,000-share purchase

Trade price range $17.06–$17.10 per share Range of prices for individual trades in the purchase

Shares owned after transaction 15,500 shares Director’s direct holdings following the purchase

Key Terms

open-market purchase, weighted average price, Form 4, common stock

4 terms

open-market purchase financial

"reported an open-market purchase of 2,000 shares of common stock"

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.

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.

Form 4 regulatory

"set forth in this footnote of this Form 4."

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.

common stock financial

"Common Stock"

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 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)
03/30/2026

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	03/30/2026		P		2,000	A	$17.08(1)	15,500	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:

1. The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices within the range of $17.06 to $17.10, 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 set forth in this footnote of this Form 4.

	/s/ Ron Caponigro, Attorney-in-Fact	04/01/2026
	** 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 on this Form 4?

Dyne Therapeutics reported that director Brian S. Posner made an open-market purchase of 2,000 shares of common stock. The filing shows this single buy transaction and the resulting updated direct share ownership position.

At what price did the Dyne Therapeutics (DYN) director buy the shares?

The director bought the 2,000 Dyne Therapeutics shares at a weighted average price of $17.08 per share. Individual trades occurred within a narrow range between $17.06 and $17.10, according to the transaction footnote.

How many Dyne Therapeutics (DYN) shares does Brian S. Posner own after the purchase?

After the reported transaction, Brian S. Posner directly owns 15,500 shares of Dyne Therapeutics common stock. This figure reflects his holdings immediately following the 2,000-share open-market purchase disclosed in the Form 4 filing.

Was the Dyne Therapeutics (DYN) Form 4 transaction a buy or a sell?

The Form 4 shows a buy transaction. Director Brian S. Posner executed an open-market purchase of 2,000 Dyne Therapeutics common shares, increasing his direct holdings to 15,500 shares following completion of the trade.

Were Dyne Therapeutics (DYN) shares bought in multiple trades in this Form 4?

Yes. The filing notes the reported $17.08 price is a weighted average. Shares were purchased in multiple trades at prices between $17.06 and $17.10, and detailed trade-by-trade pricing is available on request from the parties listed.