Dyne CEO auto-sells 5,658 shares at $18.88
Dyne Therapeutics’ CEO reported an automatic Rule 10b5-1 tax-withholding sale of 5,658 shares and now holds over 350,000 shares directly plus additional shares in family trusts.
Rhea-AI Filing Summary
Dyne Therapeutics, Inc. (DYN) reported that CEO and President John Cox sold 5,658 shares of common stock on September 8, 2026 at a weighted average price of $18.88 per share. The sale was an automatic transaction to satisfy tax withholding obligations upon vesting of restricted stock units under a pre-arranged Rule 10b5-1 binding contract, and is described as not a discretionary trade. Following this sale, Cox directly holds 357,507 shares of common stock, including 239,233 unvested RSUs, and four trusts for the benefit of his children each hold 18,000 shares indirectly.
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Insider Trade Summary 10b5-1
Net Seller: 5,658 shares
Net Sell
5 txns
Insider
Cox John
Role
CEO & President
Sold
5,658 shs ($107K)
| Type | Security | Shares | Price | Value |
|---|---|---|---|---|
| Sale | Common Stock F1, F2, F3 | 5,658 | $18.88 | $107K |
| holding | Common Stock F4 | -- | -- | -- |
| holding | Common Stock F4 | -- | -- | -- |
| holding | Common Stock F4 | -- | -- | -- |
| holding | Common Stock F4 | -- | -- | -- |
Holdings After Transaction:
Common Stock — 357,507 shares (Direct);
Common Stock — 18,000 shares (Indirect, By Trust #1);
Common Stock — 18,000 shares (Indirect, By Trust #2);
Common Stock — 18,000 shares (Indirect, By Trust #3);
Common Stock — 18,000 shares (Indirect, By Trust #4)
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 December 4, 2024. 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.
- 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 $18.77 to $18.92, 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.
- F3. Includes 239,233 unvested RSUs.
- F4. These shares are held in a trust for the benefit of a child of the Reporting Person.
Key Figures
Shares sold: 5,658 shares
Weighted average sale price: $18.88 per share
Direct holdings after transaction: 357,507 shares
+3 more
6 metrics
Shares sold
5,658 shares
Automatic sale on September 8, 2026 to satisfy tax withholding
Weighted average sale price
$18.88 per share
Shares sold in multiple trades between $18.77 and $18.92
Direct holdings after transaction
357,507 shares
Common stock held directly by John Cox after September 8, 2026 sale
Unvested RSUs included in direct holdings
239,233 RSUs
Unvested restricted stock units included within 357,507 direct shares
Shares per child’s trust
18,000 shares
Indirect holdings in each of four trusts for children of the reporting person
Sale price range
$18.77–$18.92 per share
Range of prices for the multiple transactions comprising the 5,658-share sale
Key Terms
restricted stock units, tax withholding obligations, Rule 10b5-1, weighted average price, +1 more
5 terms
restricted stock units financial
"vesting of restricted stock units granted to the Reporting Person"
Restricted stock units are a type of company reward where employees are promised shares of stock, but they only fully own these shares after meeting certain conditions, like staying with the company for a set time. They matter because they can become valuable assets and are often used to motivate employees to help the company succeed.
tax withholding obligations financial
"shares automatically sold by the Reporting Person to satisfy tax withholding obligations"
Rule 10b5-1 regulatory
"constituting a "binding contract" consistent with the affirmative defense to liability under Rule 10b5-1"
Rule 10b5-1 is a regulation that allows company insiders to buy or sell their shares at predetermined times, even if they have access to non-public information. It acts like setting a schedule in advance for transactions, helping prevent accusations of unfair trading. This rule provides a way for insiders to plan trades transparently, giving investors confidence that these transactions are not based on hidden information.
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.
affirmative defense regulatory
"consistent with the affirmative defense to liability under Rule 10b5-1"
FAQ
What insider transaction did DYN’s CEO report on this Form 4?
CEO John Cox reported an automatic sale of 5,658 shares of Dyne Therapeutics common stock on September 8, 2026 at a weighted average price of $18.88 per share, executed to cover tax withholding obligations tied to vesting restricted stock units.
Was the DYN CEO’s September 8, 2026 sale a discretionary trade?
No. The filing states the shares were automatically sold to satisfy tax withholding obligations under a restricted stock unit agreement that constitutes a “binding contract” consistent with the affirmative defense under Rule 10b5-1, and that the sale does not represent a discretionary trade.
Does the DYN CEO have additional indirect holdings reported in trusts?
Yes. Four separate trusts, each for the benefit of a child of John Cox, each hold 18,000 shares of Dyne Therapeutics common stock. These positions are reported as indirect ownership on the Form 4 dated September 8, 2026.
Are the CEO’s RSUs mentioned in this DYN Form 4 filing?
Yes. The Form 4 states that post-transaction direct holdings of 357,507 shares include 239,233 unvested RSUs, highlighting a substantial portion of the CEO’s stake is in the form of unvested restricted stock units.
AI-generated analysis. How Rhea-AI works. Not financial advice.
