Brian Posner joins Dyne Therapeutics (DYN) board with stock option grant

Rhea-AI Filing Summary

Dyne Therapeutics appointed Brian Posner as a Class III director, with his term running until the 2026 annual stockholders’ meeting and subject to standard continuation conditions. The Board determined he qualifies as an independent director under Nasdaq rules and he is not serving on any Board committees.

Upon election, Posner received a stock option for 70,000 shares at an exercise price of $12.50 per share, vesting in equal monthly installments over three years, with full acceleration upon a change in control. He will also receive $45,000 in annual cash Board fees, additional annual equity grants under the non-employee director program, and reimbursement of reasonable travel and out-of-pocket Board-related expenses.

The company states there are no arrangements, family relationships, or related-party transactions involving Posner that require disclosure, and he will enter into Dyne’s standard indemnification agreement for directors.

8-K Event Classification

Item 5.02 — Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers

1 item

Item 5.02 Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers Governance

Key personnel changes including departures, elections, or appointments of directors and executive officers.

Understanding 8-K Material Events →

false000181879400018187942025-10-012025-10-01

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of report (Date of earliest event reported): October 1, 2025

Dyne Therapeutics, Inc.

(Exact Name of Registrant as Specified in Charter)

Delaware		001-39509		36-4883909
(State or Other Jurisdiction of Incorporation)		(Commission File Number)		(IRS Employer Identification No.)

1560 Trapelo Road Waltham, Massachusetts		02451
(Address of Principal Executive Offices)		(Zip Code)

Registrant’s telephone number, including area code: (781) 786-8230

Not applicable

(Former Name or Former Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class		Trading symbol(s)		Name of each exchange on which registered
Common stock, $0.0001 par value per share		DYN		Nasdaq Global Select Market

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Item 5.02 Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers.

On October 1, 2025, the Board of Directors (the “Board”) of Dyne Therapeutics, Inc. (the “Company”), upon recommendation from the Nominating and Corporate Governance Committee of the Board, elected Brian Posner as a Class III director to serve on the Board until the Company’s 2026 Annual Meeting of Stockholders and until his successor has been duly elected and qualified or until his earlier death, resignation or removal. Mr. Posner has not been appointed to serve on any committees of the Board. The Board has determined that Mr. Posner is an “independent” director under the Nasdaq Stock Market rules.

Mr. Posner shall be entitled to receive compensation under the Company’s non-employee director compensation program. In accordance with this program, upon his election to the Board, Mr. Posner received, under the Company’s 2020 Stock Incentive Plan, an option to purchase 70,000 shares of the Company’s common stock at an exercise price equal to $12.50 per share, the closing price of the Company’s common stock on the date of grant, which option will vest and become exercisable in equal monthly installments over the next three years, subject to his continued service. In the event of a change in control of the Company, the vesting schedule of the option will accelerate in full. In addition, Mr. Posner will receive annual cash compensation of $45,000 as a member of the Board, annual equity grants in accordance with the non-employee director compensation program and reimbursement for reasonable travel and out-of-pocket expenses incurred in connection with attending Board meetings.

There are no arrangements or understandings between Mr. Posner and any other persons pursuant to which he was elected as a director. Mr. Posner does not have any family relationships with any of the Company’s directors or executive officers. There are no transactions and no proposed transactions between Mr. Posner and the Company that would be required to be disclosed pursuant to Item 404(a) of Regulation S-K.

Mr. Posner will enter into the Company’s standard form of indemnification agreement. The form of the indemnification agreement was filed as Exhibit 10.10 to the Company’s Registration Statement on Form S-1 filed with the U.S. Securities and Exchange Commission on August 25, 2020.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, as amended, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

				DYNE THERAPEUTICS, INC.
Date: October 2, 2025				By:		/s/ John G. Cox
				Name:		John G. Cox
				Title:		President and Chief Executive Officer

FAQ

What board change did Dyne Therapeutics (DYN) disclose in this 8-K?

Dyne Therapeutics added Brian Posner as a Class III director to its Board, with his term running until the 2026 annual meeting. He was recommended by the Nominating and Corporate Governance Committee and determined to be an independent director under Nasdaq rules.

What stock option grant did Brian Posner receive from Dyne Therapeutics (DYN)?

Brian Posner received an option to purchase 70,000 shares of Dyne Therapeutics common stock at $12.50 per share. The option vests in equal monthly installments over three years, subject to his continued service, and fully accelerates upon a change in control of the company.

What cash compensation will Dyne Therapeutics (DYN) pay its new director Brian Posner?

Brian Posner will receive $45,000 in annual cash compensation for serving on Dyne Therapeutics’ Board. In addition, he will be eligible for annual equity grants under the non-employee director compensation program and reimbursement of reasonable travel and out-of-pocket expenses for Board meetings.

Is Brian Posner independent from Dyne Therapeutics (DYN) management and related parties?

The Board determined that Brian Posner is an independent director under Nasdaq rules. The company states there are no arrangements, family relationships, or related-party transactions involving him that require disclosure under Item 404(a) of Regulation S-K.

Does Dyne Therapeutics (DYN) disclose any special agreements tied to Brian Posner’s appointment?

Dyne Therapeutics states there are no arrangements or understandings with other persons under which Brian Posner was elected. He will, however, enter into the company’s standard form of indemnification agreement used for directors, as previously filed in its Form S-1 registration statement.