[Form 4] Metsera, Inc. Insider Trading Activity

Rhea-AI Filing Summary

Metsera, Inc. reported insider changes tied to its merger with Pfizer Inc., where all reported Metsera common shares were converted into cash and contingent value rights. The filing shows that indirect holdings reported through F-Prime Inc. and other related persons and entities went to zero following transactions dated 11/13/2025. Under the merger agreement among Metsera, Pfizer and Mayfair Merger Sub, each share of Metsera common stock was converted into the right to receive $65.60 in cash per share, net of applicable withholding taxes, plus one contractual contingent value right providing for potential additional cash payments if specified milestones are achieved.

Insights

Equity mergers and insider reporting analyst

Form 4 confirms Metsera’s cash-and-CVR Pfizer merger payout and zeroed insider holdings.

This Form 4 for Metsera, Inc. (MTSR) documents that, as of 11/13/2025, all reported Metsera common shares indirectly held through entities like F-Prime Inc. were converted in connection with the closing of its merger with Pfizer Inc.. Table I shows post-transaction beneficial ownership of 0 shares for the reported positions, indicating those interests were fully cashed out or otherwise converted under the merger terms.

The explanation section details that each Metsera common share was automatically converted into the right to receive $65.60 in cash per share, net of applicable withholding taxes, plus one contingent value right. The CVR entitles holders to potential future cash payments if certain milestones defined in the contingent value rights agreement with Equiniti Trust Company, LLC are met. Actual value from the CVR depends on future milestone achievement under that agreement.

Remarks clarify governance context: Abigail P. Johnson and members of the Johnson family may be deemed a controlling group with respect to FMR LLC under the Investment Company Act due to their voting structure, and that F-Prime Inc. is a wholly owned subsidiary of FMR LLC. The statement also notes that the filers do not admit beneficial ownership for Section 16 purposes, highlighting the technical nature of this ownership report rather than introducing new economic exposure.

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^*

FMR LLC

(Last) (First) (Middle)

245 SUMMER STREET

(Street)

BOSTON MA 02210

(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)

	Director	X	10% Owner
	Officer (give title below)	X	Other (specify below)
			See Remark 1

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)

X	Form filed by One Reporting Person
	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		J(1)(2)		3,010	D	(1)(2)	0	I	F-Prime Inc.
Common Stock	11/13/2025		J(1)(2)		2,230,450	D	(1)(2)	0	I	Shares held by persons and entities whose shares are subject to reporting by the undersigned.

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

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"),

2. (Continued from footnote 1) net of all applicable withholding taxes, plus (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").

Remarks:

Remark 1: Abigail P. Johnson is a Director, the Chairman and the Chief Executive Officer of FMR LLC. Members of the Johnson family, including Abigail P. Johnson, are the predominant owners, directly or through trusts, of Series B voting common shares of FMR LLC, representing 49% of the voting power of FMR LLC. The Johnson family group and all other Series B shareholders have entered into a shareholders' voting agreement under which all Series B voting common shares will be voted in accordance with the majority vote of Series B voting common shares. Accordingly, through their ownership of voting common shares and the execution of the shareholders' voting agreement, members of the Johnson family may be deemed, under the Investment Company Act of 1940, to form a controlling group with respect to FMR LLC. The address of Abigail P. Johnson is c/o FMR LLC, 245 Summer Street, Boston, MA 02110. Remark 2: The filing of this statement shall not be deemed to be an admission that, for purposes of Section 16 of the Securities Exchange Act of 1934 or otherwise, the undersigned are the beneficial owners of any securities reported herein. Remark 3: F-Prime Inc. is a wholly-owned subsidiary of FMR LLC.

	/s/ Stephanie J. Brown, Duly authorized under Powers of Attorney, by and on behalf of FMR LLC and its direct and indirect subsidiaries, and Abigail P. Johnson	11/17/2025
	** 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).
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FAQ

What transaction involving Metsera, Inc. (MTSR) is reflected in this Form 4?

The Form 4 reflects the closing of the merger of Metsera, Inc. with Mayfair Merger Sub, Inc., a wholly owned subsidiary of Pfizer Inc., under which Metsera became a wholly owned subsidiary of Pfizer and the reported Metsera shares were converted into merger consideration.

What did Metsera (MTSR) shareholders receive in the Pfizer merger?

At the effective time of the merger, each issued and outstanding share of Metsera common stock was automatically converted into the right to receive $65.60 in cash per share, net of applicable withholding taxes, plus one contingent value right (CVR) for potential additional cash payments if specified milestones are achieved.

How many Metsera shares did the reporting entities hold after the merger transaction?

Following the reported transactions dated 11/13/2025, the Form 4 shows 0 shares of Metsera common stock beneficially owned for the reported positions, indicating that the previously reported holdings were fully converted into the merger consideration.

Who is the key reporting person in this Metsera (MTSR) Form 4 and what is their role?

The remarks identify Abigail P. Johnson as a Director, Chairman and Chief Executive Officer of FMR LLC. Members of the Johnson family, including her, are predominant owners of certain voting shares of FMR LLC and may be deemed to form a controlling group with respect to FMR LLC under the Investment Company Act of 1940.

What is the role of F-Prime Inc. and FMR LLC in relation to Metsera shares?

The Form 4 notes that F-Prime Inc. is a wholly owned subsidiary of FMR LLC, and one line in Table I refers to shares held by persons and entities whose shares are subject to reporting by the undersigned. The filers state that the filing should not be deemed an admission that they are beneficial owners of the securities for Section 16 or other purposes.

What is the contingent value right (CVR) mentioned in the Metsera–Pfizer merger?

The CVR is described as a contractual contingent value right that gives the holder the right to receive contingent cash payments, without interest, if certain milestones are met. Its terms are governed by a contingent value rights agreement between Pfizer and Equiniti Trust Company, LLC dated 11/13/2025.