Metsera, Inc. (MTSR) received an amended Schedule 13G showing Janus Henderson Group plc as a passive institutional holder. Janus Henderson and its affiliated asset managers are deemed to beneficially own 3,242,849 shares of Metsera common stock, representing 3.1% of the class as of 12/31/2025.
All voting and investment power over these shares is shared through various asset management subsidiaries that manage client accounts, referred to as Managed Portfolios. The Managed Portfolios, not Janus Henderson, have the right to receive dividends and sale proceeds, and none of them individually owns more than five percent of Metsera’s common stock.
Janus Henderson certifies that the position is held in the ordinary course of business and not for the purpose of changing or influencing control of Metsera, consistent with a passive investment stance.
What ownership stake in Metsera (MTSR) does Janus Henderson report?
Janus Henderson reports beneficial ownership of 3,242,849 Metsera common shares, equal to 3.1% of the class as of December 31, 2025. The shares are held across client accounts managed by its asset management subsidiaries.
Is Janus Henderson’s Metsera (MTSR) stake a passive investment?
Yes. Janus Henderson certifies the Metsera shares were acquired and are held in the ordinary course of business and not to change or influence control. This aligns with a Schedule 13G passive investment filing rather than an activist position.
Who has voting and dispositive power over Metsera (MTSR) shares?
Janus Henderson reports zero sole voting or dispositive power and 3,242,849 shares with shared voting and shared dispositive power. Its affiliated asset managers exercise this authority for client accounts known as Managed Portfolios.
Do Janus Henderson’s clients receive Metsera (MTSR) dividends and sale proceeds?
Yes. The filing states the Managed Portfolios have the right to receive all dividends and proceeds from Metsera shares in their accounts. Janus Henderson and its asset managers disclaim ownership of these economic rights, reflecting their role as investment managers.
Does any single Janus Henderson client own over 5% of Metsera (MTSR)?
No. The document specifies that, among the Managed Portfolios, none individually owns more than five percent of Metsera’s common stock. The disclosed 3.1% stake is the combined beneficial ownership attributed to Janus Henderson’s asset management platform.
Why is this Metsera (MTSR) Schedule 13G/A labeled Amendment No. 1?
It is marked Amendment No. 1 because it updates a prior Schedule 13G reporting Janus Henderson’s Metsera position. Such amendments typically reflect changes in share count, percentage ownership, or other required disclosure details since the original filing.
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
SCHEDULE 13G
UNDER THE SECURITIES EXCHANGE ACT OF 1934
(Amendment No. 1)
METSERA, INC.
(Name of Issuer)
Common Stock
(Title of Class of Securities)
59267L107
(CUSIP Number)
12/31/2025
(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)
SCHEDULE 13G
CUSIP No.
59267L107
1
Names of Reporting Persons
JANUS HENDERSON GROUP PLC
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
3,242,849.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
3,242,849.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
3,242,849.00
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)
3.1 %
12
Type of Reporting Person (See Instructions)
HC
SCHEDULE 13G
Item 1.
(a)
Name of issuer:
METSERA, INC.
(b)
Address of issuer's principal executive offices:
3 WORLD TRADE CENTER, 175 GREENWICH STREET
NEW YORK, NY 10007
Item 2.
(a)
Name of person filing:
Janus Henderson Group plc
(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.:
59267L107
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 plc (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, and Victory Park Capital 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 3,242,849 common stock of Metsera, 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:
3.1 %
(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:
3242849
(iii) Sole power to dispose or to direct the disposition of:
0
(iv) Shared power to dispose or to direct the disposition of:
3242849
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 Metsera, 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.
