TRex Bio director holds 161,828 preferred shares

The preferred shares carry a 3.8649-for-1 conversion basis and are set to convert automatically before the initial public offering closes.

Filing Impact

(Moderate)

Filing Sentiment

(Neutral)How Sentiment works

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Form Type

Rhea-AI Filing Summary

TRex Bio, Inc. director Joel S. Marcus reported direct ownership of 161,828 shares of Series B Convertible Preferred Stock as of October 8, 2026. Each preferred share is convertible into Common Stock on a 3.8649-for-1 basis, and the preferred stock will automatically convert into Common Stock immediately prior to the closing of the company’s initial public offering.

Insider Trade Summary

1 transaction reported

Mixed 1 txn

Insider MARCUS JOEL S

Role Director

Type	Security	Shares	Price	Value
holding	Series B Convertible Preferred Stock ^F1	--	--	--

Holdings After Transaction: Series B Convertible Preferred Stock — 161,828 contracts (Direct)

Footnotes (1)

F1. Each share of Series B Convertible Preferred Stock is convertible into shares of the Issuer's Common Stock on a 3.8649-for-1 basis and has no expiration date. The Series B Convertible Preferred Stock will automatically convert into Common Stock immediatley prior to the closing of the Company's initial public offering.

Key Figures

Direct preferred stock holdings: 161,828 shares Conversion basis: 3.8649-for-1

2 metrics

Direct preferred stock holdings 161,828 shares Joel S. Marcus, director, as of October 8, 2026

Conversion basis 3.8649-for-1 Each Series B Convertible Preferred Stock share is convertible into Common Stock

Key Terms

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

3 terms

Series B Convertible Preferred Stock financial

"Each share of Series B Convertible Preferred Stock is convertible"

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 convert technical

"will automatically convert into Common Stock"

initial public offering financial

"closing of the Company'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 preferred shares does director Joel S. Marcus hold?

Joel S. Marcus, a director of TRex Bio, Inc., reported direct ownership of 161,828 shares of Series B Convertible Preferred Stock as of October 8, 2026.

How do TRXB's Series B Convertible Preferred Stock shares convert?

Each share of Series B Convertible Preferred Stock is convertible into Common Stock on a 3.8649-for-1 basis. The preferred stock will automatically convert into Common Stock immediately prior to the closing of the company’s initial public offering.

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

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Available on EDGAR 10/13/2026 - 08:15 PM EDT Accepted by SEC EDGAR 10/08/2026 - 09:42 PM EDT

SEC Form 3

FORM 3

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES

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:			3235-0104
Estimated average burden
hours per response:			0.5

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. Date of Event Requiring Statement (Month/Day/Year)
10/08/2026

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

3a. Foreign Trading Symbol

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

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

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

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 Beneficially Owned
1. Title of Security (Instr. 4)	2. Amount of Securities Beneficially Owned (Instr. 4)	3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	4. Nature of Indirect Beneficial Ownership (Instr. 5)

Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 4)	2. Date Exercisable and Expiration Date (Month/Day/Year)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
1. Title of Derivative Security (Instr. 4)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	4. Conversion or Exercise Price of Derivative Security	5. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
Series B Convertible Preferred Stock	⁽¹⁾	⁽¹⁾	Common Stock	161,828	⁽¹⁾	D

Explanation of Responses:

1. Each share of Series B Convertible Preferred Stock is convertible into shares of the Issuer's Common Stock on a 3.8649-for-1 basis and has no expiration date. The Series B Convertible Preferred Stock will automatically convert into Common Stock immediatley prior to the closing of the Company's initial public offering.

Remarks:

Exhibit List: Exhibit 24 - Power of Attorney

	/s/ Brandon Hants, Attorney-in-Fact	10/08/2026
	** 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 5 (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 3: SEC 1473 (03-26)

Source: View Original Filing on SEC EDGAR