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SEC Form 4
FORM 4 UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940
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X
Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).
  
Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.
1. Name and Address of Reporting Person*
ARCH Venture Partners XII, LLC

(Last) (First) (Middle)
8755 W. HIGGINS ROAD, SUITE 1025

(Street)
CHICAGO IL 60631

(City) (State) (Zip)
2. Issuer Name and Ticker or Trading Symbol
Metsera, Inc. [ MTSR ]
5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
X Director X 10% Owner
Officer (give title below) Other (specify below)
3. Date of Earliest Transaction (Month/Day/Year)
11/13/2025
4. If Amendment, Date of Original Filed (Month/Day/Year)
6. Individual or Joint/Group Filing (Check Applicable Line)
Form filed by One Reporting Person
X Form filed by More than One Reporting Person
Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4)
Code V Amount (A) or (D) Price
Common Stock 11/13/2025(1)(2) D(1)(2) 18,503,128 D (1)(2) 0 I See Footnote(3)
Common Stock 11/13/2025(1)(2) D(1)(2) 8,313,680 D (1)(2) 0 I See Footnote(4)
Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (Month/Day/Year) 3A. Deemed Execution Date, if any (Month/Day/Year) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 6. Date Exercisable and Expiration Date (Month/Day/Year) 7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4)
Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares
1. Name and Address of Reporting Person*
ARCH Venture Partners XII, LLC

(Last) (First) (Middle)
8755 W. HIGGINS ROAD, SUITE 1025

(Street)
CHICAGO IL 60631

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer
X Director X 10% Owner
Officer (give title below) Other (specify below)
1. Name and Address of Reporting Person*
ARCH Venture Fund XII, L.P.

(Last) (First) (Middle)
8755 W. HIGGINS ROAD, SUITE 1025

(Street)
CHICAGO IL 60631

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer
X Director X 10% Owner
Officer (give title below) Other (specify below)
1. Name and Address of Reporting Person*
ARCH Venture Partners XII, L.P.

(Last) (First) (Middle)
8755 W. HIGGINS ROAD, SUITE 1025

(Street)
CHICAGO IL 60631

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer
X Director X 10% Owner
Officer (give title below) Other (specify below)
1. Name and Address of Reporting Person*
ARCH Venture Fund XIII, L.P.

(Last) (First) (Middle)
8755 W. HIGGINS ROAD, SUITE 1025

(Street)
CHICAGO IL 60631

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer
X Director X 10% Owner
Officer (give title below) Other (specify below)
1. Name and Address of Reporting Person*
ARCH Venture Partners XIII, L.P.

(Last) (First) (Middle)
8755 W. HIGGINS ROAD, SUITE 1025

(Street)
CHICAGO IL 60631

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer
X Director X 10% Owner
Officer (give title below) Other (specify below)
1. Name and Address of Reporting Person*
ARCH Venture Partners XIII, LLC

(Last) (First) (Middle)
8755 W. HIGGINS ROAD, SUITE 1025

(Street)
CHICAGO IL 60631

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer
X Director X 10% Owner
Officer (give title below) Other (specify below)
1. Name and Address of Reporting Person*
CRANDELL KEITH

(Last) (First) (Middle)
C/O ARCH VENTURE PARTNERS IX, LLC
8755 W. HIGGINS ROAD, SUITE 1025

(Street)
CHICAGO IL 60631

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer
X Director X 10% Owner
Officer (give title below) Other (specify below)
1. Name and Address of Reporting Person*
GILLIS STEVEN

(Last) (First) (Middle)
C/O ARCH VENTURE PARTNERS
8755 WEST HIGGINS ROAD, SUITE 1025

(Street)
CHICAGO IL 60631

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer
X Director X 10% Owner
Officer (give title below) Other (specify below)
1. Name and Address of Reporting Person*
NELSEN ROBERT

(Last) (First) (Middle)
8755 W. HIGGINS ROAD, SUITE 1025

(Street)
CHICAGO IL 60631

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer
X Director X 10% Owner
Officer (give title below) Other (specify below)
Explanation of Responses:
1. Pursuant to the Agreement and Plan of Merger dated September 21, 2025, as amended on November 7, 2025 (the "Merger Agreement"), by and among Metsera, Inc. (the "Company"), Pfizer Inc., a Delaware corporation ("Parent"), and Mayfair Merger Sub, Inc., a Delaware corporation and a wholly owned subsidiary of the Parent (the "Merger Sub"), the Merger Sub merged with and into the Company, with the Company continuing as the surviving corporation and a wholly owned subsidiary of the 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 Company (the "Common Stock") was converted automatically into the right to receive (i) cash in an amount equal to $65.60 per share without interest (the "Closing Amount"), net of all applicable withholding taxes, plus
2. (Continued from footnote 1) (ii) one contractual contingent value right representing the right to receive contingent payments (a "CVR") 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 the Parent and Equiniti Trust Company, LLC, dated November 13, 2025 (collectively, the "Merger Consideration").
3. Represents shares held directly by ARCH Venture Fund XII, L.P ("ARCH Venture Fund XII"). ARCH Venture Partners XII, L.P. ("AVP XII LP"), as the sole general partner of ARCH Venture Fund XII, may be deemed to beneficially own the shares held by ARCH Venture Fund XII. ARCH Venture Partners XII, LLC ("AVP XII LLC"), as the sole general partner of AVP XII LP, may be deemed to beneficially own the shares held by ARCH Venture Fund XII. AVP XII LP and AVP XII LLC disclaim beneficial ownership except to the extent of any pecuniary interest therein. As members of the investment committee of AVP XII LLC, each of Kristina M. Burow, Keith Crandell, Steven Gillis and Robert Nelsen (the "AVP XII Committee Members") may also be deemed to share the power to direct the disposition and vote of the ARCH Venture Fund XII shares. Each AVP XII Committee Member disclaims beneficial ownership except to the extent of any pecuniary interest therein.
4. Represents shares held directly by ARCH Venture Fund XIII, L.P. ("ARCH Venture Fund XIII"). ARCH Venture Partners XIII, L.P. ("AVP XIII LP"), as the sole general partner of ARCH Venture Fund XIII, may be deemed to beneficially own the shares held by ARCH Venture Fund XIII. ARCH Venture Partners XIII, LLC ("AVP XIII LLC"), as the sole general partner of AVP XIII LP, may be deemed to beneficially own the shares held by ARCH Venture Fund XIII. AVP XIII LP and AVP XIII LLC disclaim beneficial ownership except to the extent of any pecuniary interest therein. As members of the investment committee of AVP XIII LLC, each of Paul L. Berns, Kristina M. Burow, Keith Crandell and Robert Nelsen (the "AVP XIII Committee Members") may also be deemed to share the power to direct the disposition and vote of the ARCH Venture Fund XIII shares. Each AVP XIII Committee Member disclaims beneficial ownership except to the extent of any pecuniary interest therein.
ARCH Venture Fund XII, L.P. By: ARCH Venture Partners XII, L.P., its General Partner By: ARCH Venture Partners XII, LLC, its General Partner By: /s/ Mark McDonnell, as Attorney-in-Fact 11/14/2025
ARCH Venture Partners XII, L.P. By: ARCH Venture Partners XII, LLC, its General Partner By: /s/ Mark McDonnell, as Attorney-in-Fact 11/14/2025
ARCH Venture Partners XII, LLC By: /s/ Mark McDonnell, as Attorney-in-Fact 11/14/2025
ARCH Venture Fund XIII, L.P. By: ARCH Venture Partners XIII, L.P., its General Partner By: ARCH Venture Partners XIII, LLC, its General Partner By: /s/ Mark McDonnell, as Attorney-in-Fact 11/14/2025
ARCH Venture Partners XIII, L.P. By: ARCH Venture Partners XIII, LLC, its General Partner By: /s/ Mark McDonnell, as Attorney-in-Fact 11/14/2025
ARCH Venture Partners XIII, LLC By: /s/ Mark McDonnell, as Attorney-in-Fact 11/14/2025
/s/ Keith Crandell, By: Mark McDonnell, attorney-in-fact 11/14/2025
/s/ Steven Gillis, By: Mark McDonnell, attorney-in-fact 11/14/2025
/s/ Robert Nelsen, By: Mark McDonnell, attorney-in-fact 11/14/2025
** Signature of Reporting Person Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
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