[Form 4] Metsera, Inc. Insider Trading Activity

Rhea-AI Filing Summary

Metsera, Inc. (MTSR) reported insider transactions tied to its merger with Pfizer. On 11/13/2025, each share of Metsera common stock was converted into the right to receive $65.60 in cash per share plus one contingent value right (CVR) under the merger terms.

The Chief Medical Officer reported disposition of 17,000 common shares, leaving 0 shares beneficially owned. Outstanding stock options were canceled for cash based on the $65.60 closing amount and CVRs per share covered, including options over 120,000 shares (exercise price $29.25) and options over 829,885 and 21,279 shares (exercise price $0.26). RSUs were also canceled and converted into cash based on the closing amount and an equivalent number of CVRs, with vesting terms preserved under the agreement.

Insights

Equity compensation and M&A specialist

Form 4 reflects merger payout: $65.60 cash per share plus one CVR.

The filing documents completion mechanics of the Pfizer–Metsera deal. Each common share became entitled to $65.60 cash plus one CVR. The reporting officer’s 17,000 shares were disposed, resulting in 0 shares held. This aligns with a cash-out merger structure where equity converts to consideration rather than remaining outstanding.

Employee equity was addressed uniformly: options were canceled for cash equal to intrinsic value using the $65.60 closing amount and one CVR per underlying share; RSUs were canceled for cash at the same per‑share amount and CVRs, with vesting terms preserved and a vesting catch-up by the first anniversary noted. Actual proceeds depend on individual grant terms and continued service where required.

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^*

Marso Steven

(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 MEDICAL 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)(5)	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		(5)	(5)	Common Stock	17,000	(5)	17,000	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)	$0.26	11/13/2025		D			829,885	(7)	05/25/2033	Common Stock	829,885	(3)(4)	0	D
Stock Option (right to buy)(3)(4)	$0.26	11/13/2025		D			21,279	(8)	05/25/2033	Common Stock	21,279	(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. 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.

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

7. This option was fully vested as to 75% of the shares underlying the option and 25% was to be vested on May 26, 2026.

8. This option was fully vested.

	/s/ Matthew Lang, Attorney-in-Fact for Steven Marso	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) shareholders receive in the Pfizer merger?

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

What did the Metsera CMO report on Form 4?

Disposition of 17,000 common shares on 11/13/2025, resulting in 0 shares beneficially owned.

How were Metsera stock options treated at closing?

Options were canceled for cash based on the $65.60 closing amount minus exercise price, plus one CVR per underlying share.

What happened to Metsera RSUs in the transaction?

RSUs were canceled and converted into cash at $65.60 per share and an equivalent number of CVRs, with vesting terms preserved.

Were any option exercise prices disclosed?

Yes. Examples include options over 120,000 shares at $29.25 and options over 829,885 and 21,279 shares at $0.26.

What is a CVR in this context?

A contractual right to potential future cash payments upon achievement of specified milestones, as defined in the agreement dated 11/13/2025.