# EDGAR Filing Document

**Accession Number:** 0002040807
**File Stem:** 0001274173-26-000066
**Filing Date:** 2026-2
**Character Count:** 12099
**Document Hash:** 2b39c4a50826c4ca61e1032357525b37
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001274173-26-000066.hdr.sgml**: 20260217

**ACCESSION NUMBER**: 0001274173-26-000066

**CONFORMED SUBMISSION TYPE**: SCHEDULE 13G/A

**PUBLIC DOCUMENT COUNT**: 3

**FILED AS OF DATE**: 20260217

**DATE AS OF CHANGE**: 20260217

**SUBJECT COMPANY**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** Metsera, Inc.
- **CENTRAL INDEX KEY:** 0002040807
- **STANDARD INDUSTRIAL CLASSIFICATION:** PHARMACEUTICAL PREPARATIONS [2834]
- **ORGANIZATION NAME:** 03 Life Sciences
- **EIN:** 000000000
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** SCHEDULE 13G/A
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 005-94832
- **FILM NUMBER:** 26638825

**BUSINESS ADDRESS:**
- **STREET 1:** 3 WORLD TRADE CENTER
- **STREET 2:** 175 GREENWICH STREET
- **CITY:** NEW YORK
- **STATE:** NY
- **ZIP:** 10007
- **BUSINESS PHONE:** (212) 784-6595

**MAIL ADDRESS:**
- **STREET 1:** 3 WORLD TRADE CENTER
- **STREET 2:** 175 GREENWICH STREET
- **CITY:** NEW YORK
- **STATE:** NY
- **ZIP:** 10007
**FILED BY**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** JANUS HENDERSON GROUP PLC
- **CENTRAL INDEX KEY:** 0001274173
- **STANDARD INDUSTRIAL CLASSIFICATION:** INVESTMENT ADVICE [6282]
- **ORGANIZATION NAME:** 02 Finance
- **EIN:** 000000000
- **STATE OF INCORPORATION:** Y9
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** SCHEDULE 13G/A

**BUSINESS ADDRESS:**
- **STREET 1:** 201 BISHOPSGATE
- **CITY:** LONDON
- **STATE:** X0
- **ZIP:** EC2M 3AE
- **BUSINESS PHONE:** 442078181818

**MAIL ADDRESS:**
- **STREET 1:** 201 BISHOPSGATE
- **CITY:** LONDON
- **STATE:** X0
- **ZIP:** EC2M 3AE

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** HENDERSON GROUP PLC
- **DATE OF NAME CHANGE:** 20050511

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** HHG PLC
- **DATE OF NAME CHANGE:** 20031223

## Ex-24

```

POWER OF ATTORNEY

The undersigned, Janus Henderson Group plc ("the Company"),
does hereby make, constitute and appoint each of Kristin Mariani
and Caroline Barotti acting severally, as its true and lawful
attorneys in-fact, for the purpose of, from time to time,
executing in its name and on its behalf, whether the Company
individually or as representative of others, any and all
documents, certificates, instruments, statements, other filings
and amendments to the foregoing (collectively, "documents")
determined by such person to be necessary or appropriate to
comply with ownership or control-person reporting requirements
imposed by any United States or non-United States governmental
or regulatory authority, including, without limitation, Forms
13D, 13F, 13G and 13H and any amendments to any of the foregoing
as may be required to be filed with the Securities and Exchange
Commission, and delivering, furnishing or filing any such
documents with the appropriate governmental, regulatory authority
or other person, and giving and granting to each such
attorney-in-fact power and authority to act in the premises as
fully and to all intents and purposes as the Company might or
could do if personally present by one of its authorized
signatories, hereby ratifying and confirming all that said
attorney-in-fact shall lawfully do or cause to be done by
virtue hereof. Any such determination by an attorney-in-fact
named herein shall be conclusively evidenced by such person's
execution, delivery, furnishing or filing of the applicable
document. This power of attorney shall be valid from the date
hereof and shall remain in full force and effect until either
revoked in writing by the Company, or, in respect of any
attorney-in-fact named herein, until such person ceases to
be an employee of the Company or one of its affiliates.
IN WITNESS WHEREOF, the undersigned has caused this power
of attorney to be executed as of this 9th day of
December, 2022. Janus Henderson Group plc
By: /s/ Michelle Rosenberg
Name: Michelle Rosenberg
Title: General Counsel and Company Secretary

```

## Ex-99

```

The Asset Managers on whose behalf JHG is reporting include:
Janus Henderson Investors US LLC (IA)
Janus Henderson Investors UK Limited (FI)
Janus Henderson Investors Australia Institutional Funds Management Limited (FI)
Janus Henderson Investors International Limited (FI)
Janus Henderson Investors Middle East Limited (FI)
Janus Henderson Investors (Jersey) Limited (FI)
Janus Henderson Investors (Japan) Limited (FI)
Janus Henderson Investors (Singapore) Limited (FI)
Kapstream Capital Pty Limited (FI)
Privacore Capital Advisors LLC (FI)
Tabula Investment Management Limited (FI)
Victory Park Capital Advisors LLC (FI)

Please note that not every Asset Manager has investment and/or voting discretion
over the securities reported herein.

```

### UNITED STATES SECURITIES AND EXCHANGE COMMISSION
**Washington, D.C. 20549**

## SCHEDULE 13G

### Under the Securities Exchange Act of 1934

**(Amendment No. 1)**

**Issuer:** METSERA, INC.

**Title of Class of Securities:** Common Stock

**CUSIP Number:** 59267L107

**Date of Event Which Requires Filing of this Statement:** 12/31/2025

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

- [x] Rule 13d-1(b)

- [ ] Rule 13d-1(c)

- [ ] Rule 13d-1(d)

---

| 1. | Names of Reporting Persons<br>JANUS HENDERSON GROUP PLC | Names of Reporting Persons<br>JANUS HENDERSON GROUP PLC |
|:---|:---|:---|:---|
| 2. | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [ ] | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [ ] |
| 3. | SEC Use Only | SEC Use Only |
| 4. | Citizenship or Place of Organization<br>Y9 | Citizenship or Place of Organization<br>Y9 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 5. | Sole Voting Power<br>0 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 6. | Shared Voting Power<br>3242849 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 7. | Sole Dispositive Power<br>0 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 8. | Shared Dispositive Power<br>3242849 |
| 9. | Aggregate Amount Beneficially Owned by Each Reporting Person<br>3242849 | Aggregate Amount Beneficially Owned by Each Reporting Person<br>3242849 |
| 10. | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] |
| 11. | Percent of Class Represented by Amount in Row (9)<br>3.1% | Percent of Class Represented by Amount in Row (9)<br>3.1% |
| 12. | Type of Reporting Person (See Instructions)<br>HC | Type of Reporting Person (See Instructions)<br>HC |

---

**Item 1(a). Name of Issuer:**
METSERA, INC.

**Item 1(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

**Item 2(b). Address of Principal Business Office:**
201 Bishopsgate
EC2M 3AE, United Kingdom

**Item 2(c). Citizenship:**
Y9

**Item 2(d). Title of Class of Securities:**
Common Stock

**Item 2(e). CUSIP Number:**
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) [x] 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 Five Percent or Less of a Class.**

[x] If this statement is being filed to report the fact that as of the date hereof the reporting person has ceased to be the beneficial owner of more than five percent of the class of securities, check the following.

**Item 6. Ownership of More than 5 Percent on Behalf of Another Person.**

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**

Please refer to Exhibit 99.

**Item 8. Identification and Classification of Members of the Group**

N/A

**Item 9. Notice of Dissolution of Group**

—

**Item 10. Certification:**

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 PLC**

**Date:** 02/17/2026

**By:** Kristin Mariani

**Name & Title:** Head of North America Compliance