TRex Bio director Marcus converts preferred shares

Rhea-AI Filing Summary

TRex Bio, Inc. director Joel S. Marcus reported that 161,828 shares of Series B Convertible Preferred Stock automatically converted into 41,871 shares of Common Stock on October 13, 2026, at a 3.8649-to-1 basis, without further consideration, immediately before the closing of the issuer’s initial public offering. He directly held 41,871 common shares and zero Series B preferred shares after the conversion.

Insider Trade Summary

161,828 shares exercised/converted

Exercise 2 txns

Insider MARCUS JOEL S

Role Director

Type	Security	Shares	Price	Value
Conversion	Series B Convertible Preferred Stock F1	161,828	$0.00	$0.00
Conversion	Common Stock F1	41,871	--	--

Holdings After Transaction: Series B Convertible Preferred Stock — 0 contracts (Direct); Common Stock — 41,871 shares (Direct)

Footnotes (1)

1. F1. On October 13, 2026, the shares of Series B Convertible Preferred Stock automatically converted into shares of Common Stock on a 3.8649-to-1 basis without payment of further consideration immediately prior to the closing of the Issuer's initial public offering. The shares have no expiration date.

Key Figures

Series B Convertible Preferred Stock converted: 161,828 shares Common Stock acquired in conversion: 41,871 shares Conversion basis: 3.8649-to-1 +1 more

4 metrics

Series B Convertible Preferred Stock converted 161,828 shares October 13, 2026

Common Stock acquired in conversion 41,871 shares October 13, 2026

Conversion basis 3.8649-to-1 Series B Convertible Preferred Stock into Common Stock

Series B preferred shares following transaction 0 shares Direct holdings after the conversion

Key Terms

Series B Convertible Preferred Stock, automatically converted, initial public offering

3 terms

Series B Convertible Preferred Stock financial

"shares of Series B Convertible Preferred Stock automatically converted"

Series B convertible preferred stock is a class of shares sold during a later-stage private financing that combines features of a loan and common stock: it usually pays priority dividends or has a priority claim if the company is sold, and it can be converted into common shares under predefined rules. Investors care because these shares affect ownership stakes and payout order—like having a reserved place in line and a ticket that can turn into regular ownership—so they influence potential returns and dilution for other shareholders.

automatically converted financial

"shares of Series B Convertible Preferred Stock automatically converted"

initial public offering financial

"immediately prior to the closing of the Issuer's initial public offering"

An initial public offering (IPO) is when a private company first sells its shares to the public and becomes a stock-listed company. It matters because it allows the company to raise money from a wide range of investors, helping it grow, while giving early shareholders a way to sell some of their ownership.

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

How many TRXB shares did director Joel S. Marcus receive in the conversion?

Joel S. Marcus received 41,871 shares of Common Stock when 161,828 shares of Series B Convertible Preferred Stock automatically converted on October 13, 2026. The conversion was on a 3.8649-to-1 basis, without further consideration, immediately before the initial public offering closed.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Available on EDGAR 10/13/2026 - 08:14 PM EDT Accepted by SEC EDGAR 10/13/2026 - 06:31 PM EDT Learn about SEC filing dates

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

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

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^*

MARCUS JOEL S

(Last) (First) (Middle)

C/O TREX BIO, INC.

269 EAST GRAND AVENUE, SUITE 300

(Street)

SOUTH SAN FRANCISCO CALIFORNIA 94080

(City) (State) (Zip)

UNITED STATES

(Country)

2. Issuer Name and Ticker or Trading Symbol
TRex Bio, Inc. [ TRXB ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

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

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
10/13/2026

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

4. If Amendment, Date of Original Filed (Month/Day/Year)

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	10/13/2026		C		41,871	A	(1)	41,871	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
Series B Convertible Preferred Stock	(1)	10/13/2026		C			161,828	(1)	(1)	Common Stock	41,871	$0	0	D

Explanation of Responses:

1. On October 13, 2026, the shares of Series B Convertible Preferred Stock automatically converted into shares of Common Stock on a 3.8649-to-1 basis without payment of further consideration immediately prior to the closing of the Issuer's initial public offering. The shares have no expiration date.

	/s/ Brandon Hants, as attorney-in-fact	10/13/2026
	** 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.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.
* Form 4: SEC 1474 (03-26)