[Form 4] Metsera, Inc. Insider Trading Activity

Rhea-AI Filing Summary

Metsera, Inc. (MTSR) filed a Form 4 detailing insider transactions tied to its merger with Pfizer. The filing states each share of common stock was converted into the right to receive $65.60 per share plus one contingent value right (CVR).

Chief Scientific Officer Brian Hubbard reported the disposal of 17,000 shares, with 0 shares owned afterward. Outstanding stock options were cancelled for cash equal to any in‑the‑money value plus CVRs, including options covering 319,186 shares at $0.26, 120,000 at $29.25, and 106,395 at $8.18. A grant of 17,000 RSUs on November 12, 2025 was converted to cash at the Closing Amount and CVRs. Unvested cash and CVR amounts vest on the first anniversary of the merger.

Insights

M&A and Equity Compensation Analyst

Form 4 confirms merger consideration: $65.60 per share plus one CVR.

The filing documents how the Pfizer merger consideration flows through equity: common shares convert to $65.60 cash per share plus one CVR. Equity awards (stock options and RSUs) are cancelled or converted into cash based on in‑the‑money value and an equivalent number of CVRs.

Key details include cancellation of options covering 319,186 shares at $0.26, 120,000 at $29.25, and 106,395 at $8.18, and conversion of 17,000 RSUs. The filing states unvested cash and CVRs tied to awards vest on the first anniversary of the merger, contingent on continued service.

For trading history, the officer reported disposal of 17,000 common shares with 0 remaining directly owned after November 13, 2025. Actual financial impact depends on individual award terms and service conditions disclosed here.

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

OMB APPROVAL

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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^*

Hubbard Brian

(Last) (First) (Middle)

C/O METSERA, INC. 3 WORLD TRADE

CENTER 175 GREENWICH STREET

(Street)

NEW YORK NY 10007

(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		10% Owner
X	Officer (give title below)		Other (specify below)
	CHIEF SCIENTIFIC OFFICER

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		D(1)(2)		17,000	D	(1)(2)(8)	0	D

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
Restricted Stock Unit	$0	11/13/2025		A		17,000		(8)	(8)	Common Stock	17,000	(8)	17,000	D
Stock Option (right to buy)(3)(4)	$0.26	11/13/2025		D			319,186	(5)	05/25/2033	Common Stock	319,186	(3)(4)	0	D
Stock Option (right to buy)(3)(4)	$29.25	11/13/2025		D			120,000	(6)	05/19/2035	Common Stock	120,000	(3)(4)	0	D
Stock Option (right to buy)(3)(4)	$8.18	11/13/2025		D			106,395	(7)	11/27/2034	Common Stock	106,395	(3)(4)	0	D

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. Pursuant to the Merger Agreement, each outstanding and unexercised option immediately prior to the Effective Time, whether vested or unvested, was cancelled in exchange for the right to receive (x) an amount in cash equal to the product of (i) the excess, if any, of the Closing Amount minus the exercise price of such option, multiplied by (ii) the number of shares of Common Stock subject to such option immediately prior to the Effective Time, net of all applicable withholding taxes, and (y) one CVR for each share of the Common Stock subject to such stock option immediately prior to the Effective Time. In the case of any unvested stock options, the cash payment and the CVRs are subject to the same vesting schedule terms as were applicable to the stock options,

4. (Continued from footnote 3) except that all such payments will become vested upon the first anniversary of the closing of the Merger, subject to the holder's continued service with the Parent or its subsidiaries through the first anniversary of the Merger.

5. This option provided for vesting in four substantially equal annual installments from May 26, 2023.

6. This option provided for vesting in 48 substantially equal monthly installments from May 20, 2025.

7. This option provided for vesting in 48 substantially equal monthly installments from November 28, 2024.

8. On November 12, 2025, the Reporting Person was granted restricted stock units ("RSUs") under the Company's 2025 Incentive Award Plan in a transaction exempt under Rule 16b-3. Each RSU represents a contingent right to receive one share of Common Stock. The RSUs vest in 36 substantially equal monthly installments from November 12, 2025. Pursuant to the Merger Agreement, all RSUs were cancelled and converted into the right to receive (x) an amount of cash equal to the Closing Amount multiplied by the number of shares of Common Stock subject to such RSU immediately prior to the Effective Time, net of all applicable withholding taxes, and (y) a number of CVRs equal to the under of the shares of Common Stock underlying the RSU. The cash payment and the CVRs are subject to the same vesting schedule terms as were applicable to the RSUs.

	/s/ Matthew Lang, Attorney-in-Fact for Brian Hubbard	11/13/2025
	** 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 did Metsera (MTSR) disclose in this Form 4?

It reports insider transactions tied to the Pfizer merger, including share conversion to $65.60 per share plus one CVR and equity award treatment.

What merger consideration did Metsera shareholders receive?

Each common share converted into the right to receive $65.60 in cash plus one CVR.

What did the CSO report about his common stock holdings?

He reported the disposal of 17,000 shares, with 0 shares owned directly afterward.

How were Metsera stock options treated in the merger?

Each option was cancelled for cash equal to any intrinsic value plus one CVR per underlying share; unvested amounts vest on the first anniversary, subject to service.

Which specific option grants were affected?

Options covering 319,186 shares at $0.26, 120,000 at $29.25, and 106,395 at $8.18 were cancelled with the stated consideration.

What happened to recently granted RSUs?

17,000 RSUs granted on November 12, 2025 were converted to cash at the Closing Amount and an equal number of CVRs, following their original vesting schedule.