[Form 4] Metsera, Inc. Insider Trading Activity

Rhea-AI Filing Summary

Metsera (MTSR) filed a Form 4 tied to its merger with Pfizer. The filing states each Metsera common share was converted into $65.60 in cash plus one contingent value right (CVR) at closing. The reporting director recorded merger-related dispositions of common stock and the cancellation of equity awards in exchange for the cash consideration and CVRs.

On 11/13/2025, outstanding stock options were canceled for cash (based on the $65.60 closing amount minus the exercise price) and CVRs; RSUs were canceled for cash at $65.60 per underlying share and CVRs. The table shows 4,031 RSUs, and stock options covering 24,188 and 223,430 shares, all settled, with reported post‑transaction holdings shown as zero in the listed entries.

Insights

Equity compensation & M&A analyst

Merger consideration fixed at $65.60 plus one CVR per share.

The Form 4 reflects closing mechanics from the Pfizer–Metsera deal. Common shares converted into cash and one CVR. Options were canceled for cash equal to the in‑the‑money value (Closing Amount minus exercise price) and one CVR per option share. RSUs converted into cash at the Closing Amount per underlying share and an equal number of CVRs.

Equity awards with vesting conditions follow the merger terms; certain unvested options receive cash and CVRs on the original vesting schedule, with acceleration at the first anniversary of closing contingent on continued service. This is administrative and consistent with standard change‑in‑control treatment.

Key figures cited include $65.60 per share and award counts of 4,031 RSUs, 24,188 options at $29.25, and 223,430 options at $8.18. Actual impact for holders is determined by award terms and the CVR milestones disclosed in the CVR agreement.

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^*

BERNS PAUL L

(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)

X	Director		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)

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)		4,031	D	(1)(2)(5)	0	D
Common Stock	11/13/2025		D(1)(2)		7,523,682	D	(1)(2)	0	I	See footnote(8)
Common Stock	11/13/2025		D(1)(2)		8,313,680	D	(1)(2)	0	I	See footnote(8)
Common Stock	11/13/2025		D(1)(2)		957,559	D	(1)(2)	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		4,031		(5)	(5)	Common Stock	4,031	(5)	4,031	D
Stock Option (right to buy)(3)(4)	$29.25	11/13/2025		D			24,188	(6)	05/19/2035	Common Stock	24,188	(3)(4)	0	D
Stock Option (right to buy)(3)(4)	$8.18	11/13/2025		D			223,430	(7)	11/11/2034	Common Stock	223,430	(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. There is no vesting applicable to the cash payment and the CVRs.

6. This option provided for vesting in 12 substantially equal monthly installments from May 20, 2025.

7. This option provided for vesting in 36 substantially equal monthly installments from November 12, 2024.

8. Represents shares of Common Stock 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, Steven Gillis 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.

	/s/ Matthew Lang, Attorney-in-Fact for Paul L. Berns	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).
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FAQ

What did Metsera (MTSR) disclose in this Form 4?

A director reported merger-related dispositions and cancellations of Metsera equity, reflecting the Pfizer transaction’s cash and CVR consideration.

What was the per‑share consideration for Metsera stockholders?

Each share converted into $65.60 in cash plus one CVR at closing.

How were Metsera stock options treated at closing?

Each unexercised option was canceled for cash equal to the in‑the‑money value and one CVR per underlying share; vesting terms applied as specified.

What happened to Metsera RSUs?

RSUs were canceled and converted into cash at $65.60 per underlying share and an equal number of CVRs, with no vesting on these cash/CVR payments.

Which specific award amounts were listed in the filing?

The filing lists 4,031 RSUs, options over 24,188 shares at $29.25, and options over 223,430 shares at $8.18.

When did the transactions occur?

The report shows transactions on 11/13/2025, aligned with merger effectiveness.