Form 4: Dyne Therapeutics CEO Sells Shares for Tax Obligations

Dyne Therapeutics CEO John Cox sold 2,640 shares of common stock at $13.41 per share to cover tax withholding from RSU vesting, also remitting short-swing profits.

Summary

• John Cox, CEO & President and Director of Dyne Therapeutics, Inc. (DYN), reported a transaction on September 5, 2025.
• The transaction involved the sale of 2,640 shares of Common Stock at a price of $13.41 per share.
• This sale was an automatic transaction to satisfy tax withholding obligations related to the vesting of restricted stock units (RSUs) granted on December 4, 2024.
• The sale was executed pursuant to a Rule 10b5-1(c) plan, indicating it was a pre-arranged, non-discretionary trade.
• The sale was matchable under Section 16(b) of the Securities Exchange Act of 1934 with a prior purchase of 100,000 shares on July 14, 2025.
• Mr. Cox remitted $11,565.07 to Dyne Therapeutics, Inc. to cover the deemed short-swing profit from the Section 16(b) transaction.
• Following the reported transaction, Mr. Cox directly beneficially owns 199,539 shares of Common Stock, which includes 118,057 unvested RSUs.
• Additionally, Mr. Cox indirectly beneficially owns 18,000 shares each in four separate trusts, totaling 72,000 shares, held for the benefit of a child.

Sentiment

Score: 5

Explanation: The filing reports a routine, non-discretionary sale for tax purposes and the resolution of a short-swing profit issue, which are standard compliance matters for insiders. It does not indicate any fundamental change in the company's prospects or management's confidence.

Positives

• The transaction was executed under a Rule 10b5-1 plan, demonstrating a pre-planned and compliant approach to insider trading.
• The Reporting Person promptly remitted the short-swing profit of $11,565.07 to the Issuer, indicating adherence to Section 16(b) of the Exchange Act.

Negatives

• The Reporting Person incurred a short-swing profit of $11,565.07, which had to be remitted to the issuer, indicating a timing mismatch in trading activities that resulted in a technical violation of Section 16(b).

Risks

• Potential for short-swing profit liability under Section 16(b) of the Exchange Act for officers and directors, requiring remittance of profits to the company, as demonstrated by the $11,565.07 payment.

Future Outlook

NA

Management Comments

• The sale represents shares automatically sold by the Reporting Person to satisfy tax withholding obligations in connection with the vesting of restricted stock units.
• 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.
• The Reporting Person has paid to the Issuer an aggregate amount of $11,565.07, representing the amount of the profit deemed realized in connection with the short-swing transaction under Section 16(b) of the Exchange Act.

Industry Context

NA

Corporate Governance

Legal Proceedings

• Resolution of a short-swing profit liability under Section 16(b) of the Securities Exchange Act of 1934, with the Reporting Person remitting $11,565.07 to the Issuer.

Related Party Transactions

• Indirect beneficial ownership of 18,000 shares each in four separate trusts for the benefit of a child of the Reporting Person.

Stakeholder Impact

• Shareholders: Provides transparency regarding insider stock transactions and confirms compliance with regulatory requirements, which can foster trust.
• Regulatory Authorities: Demonstrates adherence to SEC filing requirements and insider trading regulations (Rule 10b5-1 and Section 16(b)).

Key Dates

Recommendation

This Form 4 filing details a routine, non-discretionary sale of shares by the CEO to cover tax obligations related to RSU vesting, executed under a pre-arranged 10b5-1 plan. The prompt resolution of a minor Section 16(b) short-swing profit issue further demonstrates compliance. Such a transaction does not reflect a change in management's outlook or the company's fundamentals, thus it provides no new information to alter an existing investment thesis. Investors should maintain their current position based on broader company performance and market conditions.

Keywords

Dyne Therapeutics, DYN, John Cox, Form 4, Insider Trading, Stock Sale, CEO, Restricted Stock Units, RSU, Tax Withholding, 10b5-1, Section 16(b)