John Cox Sells $131K of Dyne Therapeutics Inc (DYN) — SEC Form 4, Aug 17, 2026

Open-Market Net Sale · SEC Form 4

−$131,032

10b5-1 Plan

Equity position changed by -1.1%

Reporting Owner

John Cox

CEO

TXN 2026-08-13 · FILED 2026-08-17

Equity Position 435K sh 440,151 → 435,165

Equity Change -1.1% shares held after vs before

Filing Lag 2 business days within 2-day SEC deadline

Form 4 · Statement of Changes in Beneficial Ownership

Dyne Therapeutics Inc

DYN CIK 0001818794

Reporting Owner

Name	Relationship
John Cox CIK 0001498428	Director CEO

John Cox at Dyne Therapeutics Inc Full insider history

Bought (12 mo) —

Sold (12 mo) $443,688

More from this insider at Dyne Therapeutics Inc

Non-Derivative Securities Transactions

Title	Date	Type	Shares	Price	Net Total	Post-Txn	Ownership
Common StockF1 F2 F3	2026-08-13	S - Sale 10b5-1	4,986 D	$26.28	-$131,032	363,165	Direct

Non-Derivative Holdings

Footnotes (4)

F1: Represents shares automatically sold by the Reporting Person to satisfy tax withholding obligations in connection with the vesting of restricted stock units granted to the Reporting Person on February 12, 2026. The automatic sale of the Reporting Person's shares is provided for in a restricted stock unit agreement constituting a "binding contract" consistent with the affirmative defense to liability under Rule 10b5-1 and the sale does not represent a discretionary trade by the Reporting Person. Show more
F2: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices within the range of $26.17 to $26.39, 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. Show more
F3: Includes 248,314 unvested RSUs. Show more
F4: These shares are held in a trust for the benefit of a child of the Reporting Person. Show more

Institutional Holders

Largest by reported value

5%+ Holders · 13D/G 4 filers

Latest Schedule 13D/G per filer; stakes the filer reported closed are left out.

Other insiders at Dyne Therapeutics Inc

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