Dyne Therapeutics (DYN) gains 7.3% institutional holder Janus Henderson

Rhea-AI Filing Summary

Janus Henderson Group Ltd. filed an amended beneficial ownership report stating that its affiliated asset managers may be deemed to beneficially own 11,997,738 shares of Dyne Therapeutics Inc. common stock, representing 7.3% of the class as of June 30, 2026. These shares are held in various client accounts referred to as Managed Portfolios, for which the asset managers exercise shared voting and dispositive power over all 11,997,738 shares, with no sole voting or dispositive power. The Managed Portfolios, not Janus Henderson, have the right to receive dividends and sale proceeds, and none of the individual portfolios owns more than five percent of Dyne Therapeutics’ common stock.

Key Figures

Shares beneficially owned: 11,997,738 shares Percent of class: 7.3% Sole voting power: 0 shares +3 more

6 metrics

Shares beneficially owned 11,997,738 shares Common stock of Dyne Therapeutics Inc. deemed beneficially owned by asset managers

Percent of class 7.3% Portion of Dyne Therapeutics common stock represented by the reported holding

Sole voting power 0 shares Shares over which Janus Henderson has sole power to vote or direct the vote

Shared voting power 11,997,738 shares Shares over which affiliated asset managers have shared voting power

Shared dispositive power 11,997,738 shares Shares over which affiliated asset managers have shared power to dispose

Amendment number 7 This filing is identified as Amendment No. 7 to the ownership report

Key Terms

beneficial owner, Managed Portfolios, shared voting power, shared dispositive power, +1 more

5 terms

beneficial owner financial

"may be deemed to be the beneficial owner of 11,997,738 common stock"

A beneficial owner is the person who ultimately owns or controls a financial asset or property, even if their name isn't directly on official documents. Think of it like someone who secretly holds the keys to a safe deposit box—others may appear to have access, but the true owner is the one who benefits from what's inside. Identifying beneficial owners helps ensure transparency and prevent illegal activities like money laundering or fraud.

Managed Portfolios financial

"collectively referred to herein as Managed Portfolios"

shared voting power financial

"Shared Voting Power 11,997,738.00"

Shared voting power occurs when two or more parties jointly have the right to vote or decide how a block of company shares is cast, like co-owners who must agree before moving a piece of furniture. Investors care because who controls voting rights affects board elections, major corporate decisions and takeover outcomes, and shared control can alter regulatory disclosures and the practical influence any holder has over a company’s direction and value.

shared dispositive power financial

"Shared Dispositive Power 11,997,738.00"

Power of Attorney regulatory

"Exhibit 24: Power of Attorney"

A power of attorney is a legal document that allows one person to make decisions and act on behalf of another person, often in financial or legal matters. It’s like giving someone a trusted helper or agent the authority to handle important tasks if you are unable to do so yourself. This matters to investors because it can impact how their assets are managed or transferred if they become unable to oversee their affairs.

FAQ

What percentage of Dyne Therapeutics (DYN) does Janus Henderson report owning?

Janus Henderson Group Ltd. reports that its affiliated asset managers may be deemed to beneficially own 7.3% of Dyne Therapeutics’ common stock. This corresponds to 11,997,738 shares held across client Managed Portfolios as of June 30, 2026.

How many Dyne Therapeutics (DYN) shares are reported as beneficially owned?

The filing reports beneficial ownership of 11,997,738 shares of Dyne Therapeutics common stock. These shares are held in various Managed Portfolios for which Janus Henderson’s asset managers exercise shared voting and dispositive power.

Does Janus Henderson have sole voting power over its Dyne Therapeutics (DYN) shares?

No. The filing states Janus Henderson has 0 shares with sole voting power and 11,997,738 shares with shared voting power. The same share amounts apply to sole and shared dispositive power, indicating all authority is shared through its asset managers.

Who receives dividends and sale proceeds from the Dyne Therapeutics (DYN) shares?

The Managed Portfolios receive all dividends and sale proceeds from the Dyne Therapeutics shares. The asset managers, and Janus Henderson Group Ltd., disclaim ownership of rights to dividends or sale proceeds from securities held in these client accounts.

Do any individual Janus Henderson client accounts hold over 5% of Dyne Therapeutics (DYN)?

No. The filing states that among the Managed Portfolios, none owns more than five percent of Dyne Therapeutics’ common stock. The reported 7.3% stake reflects the aggregate deemed beneficial ownership across multiple client accounts.

What is the nature of Janus Henderson’s beneficial ownership in Dyne Therapeutics (DYN)?

Beneficial ownership arises because affiliated asset managers exercise investment and/or voting discretion over client accounts holding Dyne shares. They may be deemed owners of 11,997,738 shares but disclaim economic ownership of dividends and sale proceeds.

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Available on EDGAR 08/13/2026 - 12:48 PM Accepted by SEC EDGAR 08/13/2026 - 12:47 PM Learn about SEC filing dates

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 7)

DYNE THERAPEUTICS INC

(Name of Issuer)

Common Stock

(Title of Class of Securities)

26818M108

(CUSIP Number)

06/30/2026

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

schemaVersion:

SCHEDULE 13G

CUSIP Number(s): 26818M108

1

Names of Reporting Persons

JANUS HENDERSON GROUP Ltd.

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

JERSEY

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 11,997,738.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 11,997,738.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

11,997,738.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

7.3 %

12

Type of Reporting Person (See Instructions)

HC

SCHEDULE 13G

Item 1.
(a)	Name of issuer: DYNE THERAPEUTICS INC
(b)	Address of issuer's principal executive offices: 1560 TRAPELO ROAD WALTHAM, MA 02451
Item 2.
(a)	Name of person filing: Janus Henderson Group Ltd. In accordance with SEC Release No. 34-39538 (January 12, 1998), this Schedule 13G reflects the securities beneficially owned, or deemed to be beneficially owned, by Janus Henderson Group Ltd. It does not include securities, if any, beneficially owned by Janus Henderson Group Ltd.s ultimate parent Jupiter Topco LLC, the direct or indirect owners of Jupiter Topco LLC, or other persons that may be deemed under control of such owners. Any beneficial ownership by such persons has been disaggregated from that of Janus Henderson Group Ltd. in accordance with the release.
(b)	Address or principal business office or, if none, residence: 201 Bishopsgate EC2M 3AE, United Kingdom
(c)	Citizenship: Y9
(d)	Title of class of securities: Common Stock
(e)	CUSIP No.: 26818M108
Item 3.	If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)	Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)	Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)	Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)	Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)	An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)	An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)	A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)	A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)	A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)	A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:
(k)	Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.	Ownership
(a)	Amount beneficially owned: Janus Henderson Group Ltd. (JHG) is the ultimate parent of a number of SEC-registered investment advisers and foreign equivalents thereof, including but not limited to Janus Henderson Investors US LLC, Janus Henderson Investors UK Limited, Janus Henderson Investors Australia Institutional Funds Management Limited, Janus Henderson Investors Middle East Limited, Janus Henderson Investors (Jersey) Limited, Janus Henderson Investors (Japan) Limited, Janus Henderson Investors (Singapore) Limited, Kapstream Capital Pty Limited, Privacore Capital Advisors LLC, Tabula Investment Management Limited, Victory Park Capital Advisors LLC, and Richard Berstein Advisors LLC (each, an Asset Manager and together, the Asset Managers). The Asset Managers generally exercise investment and/or voting discretion on behalf of their clients which include investment companies, other investment advisers, institutional separate accounts and retail separate accounts (collectively referred to herein as Managed Portfolios). As a result of their exercise of investment and/or voting discretion on behalf of the Managed Portfolios, the Asset Managers may be deemed to be the beneficial owner of 11,997,738 common stock of Dyne Therapeutics, Inc. However, the Asset Managers do not have the right to receive any dividends from, or the proceeds from the sale of, the securities held in the Managed Portfolios and disclaim any ownership associated with such rights.
(b)	Percent of class: 7.3 %
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 0
	(ii) Shared power to vote or to direct the vote: 11997738
	(iii) Sole power to dispose or to direct the disposition of: 0
	(iv) Shared power to dispose or to direct the disposition of: 11997738
Item 5.	Ownership of 5 Percent or Less of a Class.
	Not Applicable
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	If any other person is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, such securities, a statement to that effect should be included in response to this item and, if such interest relates to more than 5 percent of the class, such person should be identified. A listing of the shareholders of an investment company registered under the Investment Company Act of 1940 or the beneficiaries of employee benefit plan, pension fund or endowment fund is not required. The Managed Portfolios have the right to receive all dividends from, and the proceeds from the sale of, the securities held in their respective accounts. Of the Managed Portfolios, none own more than five percent of the common stock of Dyne Therapeutics, Inc.
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	If a parent holding company has filed this schedule, pursuant to Rule 13d-1(b)(ii)(G), so indicate under Item 3(g) and attach an exhibit stating the identity and the Item 3 classification of the relevant subsidiary. If a parent holding company has filed this schedule pursuant to Rule 13d-1(c) or Rule 13d-1(d), attach an exhibit stating the identification of the relevant subsidiary. Please refer to Exhibit 99.
Item 8.	Identification and Classification of Members of the Group.
	If a group has filed this schedule pursuant to §240.13d-1(b)(1)(ii)(J), so indicate under Item 3(j) and attach an exhibit stating the identity and Item 3 classification of each member of the group. If a group has filed this schedule pursuant to §240.13d-1(c) or §240.13d-1(d), attach an exhibit stating the identity of each member of the group. N/A
Item 9.	Notice of Dissolution of Group.
	Notice of dissolution of a group may be furnished as an exhibit stating the date of the dissolution and that all further filings with respect to transactions in the security reported on will be filed, if required, by members of the group, in their individual capacity. See Item 5. N/A

Item 10.

Certifications:

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under § 240.14a-11.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

JANUS HENDERSON GROUP Ltd.

Signature:	Kristin Mariani
Name/Title:	Head of North America Compliance
Date:	08/13/2026

Exhibit Information

Exhibit 24: Power of Attorney Exhibit 99: Item 7