Amendment: SEC Form SCHEDULE 13D/A filed by Metsera Inc.
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SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549 |
SCHEDULE 13D
Under the Securities Exchange Act of 1934
(Amendment No. 1)
|
Metsera, Inc. (Name of Issuer) |
Common Stock, $0.00001 par value (Title of Class of Securities) |
59267L107 (CUSIP Number) |
Mark McDonnell ARCH Venture Management, LLC, 8755 W. Higgins Road, Suite 1025 Chicago, IL, 60631 (773) 380-6600 (Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications) |
11/13/2025 (Date of Event Which Requires Filing of This Statement) |

SCHEDULE 13D
|
| CUSIP No. | 59267L107 |
| 1 |
Name of reporting person
ARCH Venture Fund XII, L.P. | ||||||||
| 2 | Check the appropriate box if a member of a Group (See Instructions)
(a)
(b)
| ||||||||
| 3 | SEC use only | ||||||||
| 4 |
Source of funds (See Instructions)
WC | ||||||||
| 5 |
Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)
![]() | ||||||||
| 6 | Citizenship or place of organization
DELAWARE
| ||||||||
| Number of Shares Beneficially Owned by Each Reporting Person With: |
| ||||||||
| 11 | Aggregate amount beneficially owned by each reporting person
0.00 | ||||||||
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)
![]() | ||||||||
| 13 | Percent of class represented by amount in Row (11)
0 % | ||||||||
| 14 | Type of Reporting Person (See Instructions)
PN |
SCHEDULE 13D
|
| CUSIP No. | 59267L107 |
| 1 |
Name of reporting person
ARCH Venture Fund XIII, L.P. | ||||||||
| 2 | Check the appropriate box if a member of a Group (See Instructions)
(a)
(b)
| ||||||||
| 3 | SEC use only | ||||||||
| 4 |
Source of funds (See Instructions)
WC | ||||||||
| 5 |
Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)
![]() | ||||||||
| 6 | Citizenship or place of organization
DELAWARE
| ||||||||
| Number of Shares Beneficially Owned by Each Reporting Person With: |
| ||||||||
| 11 | Aggregate amount beneficially owned by each reporting person
0.00 | ||||||||
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)
![]() | ||||||||
| 13 | Percent of class represented by amount in Row (11)
0 % | ||||||||
| 14 | Type of Reporting Person (See Instructions)
PN |
SCHEDULE 13D
|
| CUSIP No. | 59267L107 |
| 1 |
Name of reporting person
ARCH Venture Partners XII, L.P. | ||||||||
| 2 | Check the appropriate box if a member of a Group (See Instructions)
(a)
(b)
| ||||||||
| 3 | SEC use only | ||||||||
| 4 |
Source of funds (See Instructions)
AF | ||||||||
| 5 |
Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)
![]() | ||||||||
| 6 | Citizenship or place of organization
DELAWARE
| ||||||||
| Number of Shares Beneficially Owned by Each Reporting Person With: |
| ||||||||
| 11 | Aggregate amount beneficially owned by each reporting person
0.00 | ||||||||
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)
![]() | ||||||||
| 13 | Percent of class represented by amount in Row (11)
0 % | ||||||||
| 14 | Type of Reporting Person (See Instructions)
PN |
SCHEDULE 13D
|
| CUSIP No. | 59267L107 |
| 1 |
Name of reporting person
ARCH Venture Partners XIII, L.P. | ||||||||
| 2 | Check the appropriate box if a member of a Group (See Instructions)
(a)
(b)
| ||||||||
| 3 | SEC use only | ||||||||
| 4 |
Source of funds (See Instructions)
WC | ||||||||
| 5 |
Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)
![]() | ||||||||
| 6 | Citizenship or place of organization
DELAWARE
| ||||||||
| Number of Shares Beneficially Owned by Each Reporting Person With: |
| ||||||||
| 11 | Aggregate amount beneficially owned by each reporting person
0.00 | ||||||||
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)
![]() | ||||||||
| 13 | Percent of class represented by amount in Row (11)
0 % | ||||||||
| 14 | Type of Reporting Person (See Instructions)
PN |
SCHEDULE 13D
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| CUSIP No. | 59267L107 |
| 1 |
Name of reporting person
ARCH Venture Partners XII, LLC | ||||||||
| 2 | Check the appropriate box if a member of a Group (See Instructions)
(a)
(b)
| ||||||||
| 3 | SEC use only | ||||||||
| 4 |
Source of funds (See Instructions)
AF | ||||||||
| 5 |
Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)
![]() | ||||||||
| 6 | Citizenship or place of organization
DELAWARE
| ||||||||
| Number of Shares Beneficially Owned by Each Reporting Person With: |
| ||||||||
| 11 | Aggregate amount beneficially owned by each reporting person
0.00 | ||||||||
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)
![]() | ||||||||
| 13 | Percent of class represented by amount in Row (11)
0 % | ||||||||
| 14 | Type of Reporting Person (See Instructions)
OO |
SCHEDULE 13D
|
| CUSIP No. | 59267L107 |
| 1 |
Name of reporting person
ARCH Venture Partners XIII, LLC | ||||||||
| 2 | Check the appropriate box if a member of a Group (See Instructions)
(a)
(b)
| ||||||||
| 3 | SEC use only | ||||||||
| 4 |
Source of funds (See Instructions)
AF | ||||||||
| 5 |
Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)
![]() | ||||||||
| 6 | Citizenship or place of organization
DELAWARE
| ||||||||
| Number of Shares Beneficially Owned by Each Reporting Person With: |
| ||||||||
| 11 | Aggregate amount beneficially owned by each reporting person
0.00 | ||||||||
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)
![]() | ||||||||
| 13 | Percent of class represented by amount in Row (11)
0 % | ||||||||
| 14 | Type of Reporting Person (See Instructions)
OO |
SCHEDULE 13D
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| CUSIP No. | 59267L107 |
| 1 |
Name of reporting person
Robert Nelsen | ||||||||
| 2 | Check the appropriate box if a member of a Group (See Instructions)
(a)
(b)
| ||||||||
| 3 | SEC use only | ||||||||
| 4 |
Source of funds (See Instructions)
AF | ||||||||
| 5 |
Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)
![]() | ||||||||
| 6 | Citizenship or place of organization
UNITED STATES
| ||||||||
| Number of Shares Beneficially Owned by Each Reporting Person With: |
| ||||||||
| 11 | Aggregate amount beneficially owned by each reporting person
0.00 | ||||||||
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)
![]() | ||||||||
| 13 | Percent of class represented by amount in Row (11)
0 % | ||||||||
| 14 | Type of Reporting Person (See Instructions)
IN |
SCHEDULE 13D
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| CUSIP No. | 59267L107 |
| 1 |
Name of reporting person
Keith Crandell | ||||||||
| 2 | Check the appropriate box if a member of a Group (See Instructions)
(a)
(b)
| ||||||||
| 3 | SEC use only | ||||||||
| 4 |
Source of funds (See Instructions)
AF | ||||||||
| 5 |
Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)
![]() | ||||||||
| 6 | Citizenship or place of organization
UNITED STATES
| ||||||||
| Number of Shares Beneficially Owned by Each Reporting Person With: |
| ||||||||
| 11 | Aggregate amount beneficially owned by each reporting person
0.00 | ||||||||
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)
![]() | ||||||||
| 13 | Percent of class represented by amount in Row (11)
0 % | ||||||||
| 14 | Type of Reporting Person (See Instructions)
IN |
SCHEDULE 13D
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| CUSIP No. | 59267L107 |
| 1 |
Name of reporting person
Kristina Burow | ||||||||
| 2 | Check the appropriate box if a member of a Group (See Instructions)
(a)
(b)
| ||||||||
| 3 | SEC use only | ||||||||
| 4 |
Source of funds (See Instructions)
AF | ||||||||
| 5 |
Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)
![]() | ||||||||
| 6 | Citizenship or place of organization
UNITED STATES
| ||||||||
| Number of Shares Beneficially Owned by Each Reporting Person With: |
| ||||||||
| 11 | Aggregate amount beneficially owned by each reporting person
0.00 | ||||||||
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)
![]() | ||||||||
| 13 | Percent of class represented by amount in Row (11)
0 % | ||||||||
| 14 | Type of Reporting Person (See Instructions)
IN |
SCHEDULE 13D
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| CUSIP No. | 59267L107 |
| 1 |
Name of reporting person
Steven Gillis | ||||||||
| 2 | Check the appropriate box if a member of a Group (See Instructions)
(a)
(b)
| ||||||||
| 3 | SEC use only | ||||||||
| 4 |
Source of funds (See Instructions)
AF | ||||||||
| 5 |
Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)
![]() | ||||||||
| 6 | Citizenship or place of organization
UNITED STATES
| ||||||||
| Number of Shares Beneficially Owned by Each Reporting Person With: |
| ||||||||
| 11 | Aggregate amount beneficially owned by each reporting person
0.00 | ||||||||
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)
![]() | ||||||||
| 13 | Percent of class represented by amount in Row (11)
0 % | ||||||||
| 14 | Type of Reporting Person (See Instructions)
IN |
SCHEDULE 13D
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| CUSIP No. | 59267L107 |
| 1 |
Name of reporting person
Paul Berns | ||||||||
| 2 | Check the appropriate box if a member of a Group (See Instructions)
(a)
(b)
| ||||||||
| 3 | SEC use only | ||||||||
| 4 |
Source of funds (See Instructions)
AF | ||||||||
| 5 |
Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)
![]() | ||||||||
| 6 | Citizenship or place of organization
UNITED STATES
| ||||||||
| Number of Shares Beneficially Owned by Each Reporting Person With: |
| ||||||||
| 11 | Aggregate amount beneficially owned by each reporting person
0.00 | ||||||||
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)
![]() | ||||||||
| 13 | Percent of class represented by amount in Row (11)
0 % | ||||||||
| 14 | Type of Reporting Person (See Instructions)
IN |
SCHEDULE 13D
|
| Item 1. | Security and Issuer | |
| (a) | Title of Class of Securities:
Common Stock, $0.00001 par value | |
| (b) | Name of Issuer:
Metsera, Inc. | |
| (c) | Address of Issuer's Principal Executive Offices:
3 World Trade Center, 175 Greenwich Street, New York,
NEW YORK
, 10007. | |
Item 1 Comment:
This statement relates to the Common Stock, $0.00001 par value per share (the "Common Stock"), of Metsera, Inc. (the "Issuer") having its principal executive office at 3 World Trade Center, 175 Greenwich Street, New York, NY, 10007 USA. | ||
| Item 5. | Interest in Securities of the Issuer | |
| (a) | Item 5 of this Schedule 13D is amended and supplemented as follows:
Pursuant to the Agreement and Plan of Merger dated September 21, 2025, as amended on November 7, 2025 (the "Merger Agreement"), by and among the Issuer, Pfizer Inc., a Delaware corporation ("Parent"), and Mayfair Merger Sub, Inc., a Delaware corporation and a wholly owned subsidiary of Parent ("Merger Sub"), Merger Sub merged with and into the Issuer, with the Issuer continuing as the surviving corporation and a wholly owned subsidiary of Parent (the "Merger"). At the Effective Time of the Merger (as defined in the Merger Agreement), each issued and outstanding share of common stock, par value $0.00001 per share of the Isser was converted automatically into the right to receive (i) cash in an amount equal to $65.60 per share without interest, net of all applicable withholding taxes, plus (ii) one contractual contingent value right representing the right to receive contingent payments in cash, without interest, upon the achievement of certain specified milestones, in accordance with the terms and conditions of the contingent value rights agreement entered into by Parent and Equiniti Trust Company, LLC, dated November 13, 2025. | |
| (b) | Regarding the number of shares as to which such person has:
(i) sole power to vote or to direct the vote: See line 7 of cover sheets.
(ii) shared power to vote or to direct the vote: See line 8 of cover sheets.
(iii) sole power to dispose or to direct the disposition: See line 9 of cover sheets.
(iv) shared power to dispose or to direct the disposition: See line 10 of cover sheets. | |
| (c) | Except as set forth above, none of the Reporting Persons has effected any transaction in the Common Stock during the last 60 days. | |
| (d) | No other person is known to have the right to receive or the power to direct the receipt of dividends from, or any proceeds from the sale of, shares beneficially owned by any of the Reporting Persons. | |
| (e) | On November 13, 2025, as a result of the transactions described in Item 5(a) hereof, the Reporting Persons ceased to be the beficial owners of 5% or more of the Common Stock. | |
| 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.
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