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SEC FORM 3SEC Form 3
FORM 3UNITED 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		 
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1. Name and Address of Reporting Person*
Erwin Marion Johnston Jr.
(Last)(First)(Middle)
C/O TREX BIO, INC.
269 EAST GRAND AVENUE, SUITE 300
(Street)
SOUTH SAN FRANCISCOCA94080
(City)(State)(Zip)
2. Date of Event Requiring Statement (Month/Day/Year)
10/08/2026		3. Issuer Name and Ticker or Trading Symbol
TRex Bio, Inc. [ TRXB ]
Foreign Trading Symbol
4. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
checkbox checkedDirector10% Owner
checkbox checkedOfficer (give title below)Other (specify below)
Chief Executive Officer
5. If Amendment, Date of Original Filed (Month/Day/Year)
6. Individual or Joint/Group Filing (Check Applicable Line)
checkbox checkedForm 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)
Date ExercisableExpiration DateTitleAmount or Number of Shares
Stock Option (Right to Buy) (1)11/22/2031Common Stock299,4911.09D
Stock Option (Right to Buy) (2)05/24/2035Common Stock126,6811.09D
Stock Option (Right to Buy) (3)04/10/2035Common Stock459,6131.24D
Stock Option (Right to Buy) (4)02/18/2036Common Stock257,2661.28D
Explanation of Responses:
1. The option is fully vested and exercisable as of the date hereof.
2. The option had a vesting start date of May 25, 2022. 25% of the options vested on May, 25, 2023, and vests in equal monthly installments over 36 months, subject to continued service through the applicable vesting dates.
3. The option had a vesting start date of April 1, 2025 and vests in equal monthly installments over 48 months, subject to continued service through the applicable vesting dates.
4. The option had a vesting start date of February 19, 2026 and vests in equal monthly installments over 48 months, subject to continued service through the applicable vesting dates.
Remarks:
Exhibit List: Exhibit 24 - Power of Attorney
/s/ Brandon Hants, Attorney-in-Fact10/08/2026
** Signature of Reporting PersonDate
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.
EX-24

Exhibit 24

 

POWER OF ATTORNEY & ATTESTATION OF ELECTRONIC SIGNATURE

 

KNOW ALL BY THESE PRESENTS that the undersigned hereby constitutes and appoints:

 

Section 16 Filings

 

Johnston Erwin, Brandon Hants, or Laura Berner, each acting as the undersigned’s true and lawful attorney-in-fact, to:

 

1)
execute for and on behalf of the undersigned, in the undersigned’s capacity as officer and/or director of TRex Bio, Inc. (the “Company”), Forms 3, 4, 5 and any Schedules 13D or 13G in accordance with Section 16(a) of the Securities Exchange Act of 1934, as amended, and the rules thereunder;

 

2)
do and perform any and all acts for and on behalf of the undersigned that may be necessary or desirable to complete and execute such Form 3, 4, or 5 or Schedule 13D or 13G, complete and execute any amendment or amendments thereto, and timely file such form with United States Securities and Exchange Commission (the “SEC”) and any stock exchange or similar authority; and

 

3)
take any other action of any type whatsoever in connection with the foregoing Section 16 filing authorities that, in the opinion of each such attorney-in-fact, may be of benefit to, in the best interest of, or legally required by, the undersigned, it being understood that the documents executed by each such attorney-in-fact on behalf of the undersigned pursuant to this Power of Attorney shall be in such form and shall contain such terms and conditions as each such attorney-in-fact may approve in each such attorney-in-fact’s discretion.

 

General Powers

 

The undersigned hereby grants to the above named attorneys-in-fact full power and authority to do and perform all and every act and thing whatsoever requisite, necessary and proper to be done in the exercise of any of the rights and powers herein granted, as fully to all intents and purposes as the undersigned might or could do if personally present, hereby ratifying and confirming all that each such attorney-in-fact shall lawfully do or cause to be done by virtue of this power of attorney and the rights and powers herein granted. The undersigned acknowledges that each foregoing attorney-in-fact, in serving in such capacity at the request of the undersigned, are not assuming, nor is the Company assuming, any of the undersigned's responsibilities to comply with Section 16 of the Securities Exchange Act of 1934, as amended.

 

I understand that the Company will retain this document and furnish it to the SEC or its staff, upon their request.

 

[Signature Page Follows]

 

 

IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be executed as of August 18, 2026.

 

 

 

/s/ M. Johnston Erwin, Jr.

 

 

Name: M. Johnston Erwin, Jr.