Statement of Changes in Beneficial Ownership (Form 4)

FORM 4 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 that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN 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 * SVLSF VI, LLC 2. Issuer Name and Ticker or Trading Symbol TRex Bio, Inc. [TRXB] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director __X__ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 28 STATE STREET, SUITE 980 3. Date of Earliest Transaction (Month/Day/Year) 10/08/2026 (Street) BOSTON, MA 02109 4. If Amendment, Date Original Filed (Month/Day/Year) 6. Individual or Joint/Group Filing (Check Applicable Line) ___ Form filed by One Reporting Person _X_ Form filed by More than One Reporting Person (City) (State) (Zip) 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 10/08/2026 P 89,783 A $14 214,869 I By SV Life Sciences Fund VI, L.P.(1)(5) Common Stock 10/13/2026 C 1,574,074 A $ 0 1,788,943 I By SV Life Sciences Fund VI, L.P.(1) Common Stock 10/13/2026 C 475,411 A $ 0 2,264,354 I By SV Life Sciences Fund VI, L.P.(1) Common Stock 10/08/2026 P 3,074 A $14 7,356 I By SV Life Sciences Fund VI Strategic Partners, L.P.(2)(6) Common Stock 10/13/2026 C 53,892 A $ 0 61,248 I By SV Life Sciences Fund VI Strategic Partners, L.P.(2) Common Stock 10/13/2026 C 16,277 A $ 0 77,525 I By SV Life Sciences Fund VI Strategic Partners, L.P.(2) Common Stock 10/13/2026 C 669,939 A $ 0 669,939 I By SV Trex Coinvestment, L.P.(3)

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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 Underlying Securities (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 of Derivative Security: 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 A Preferred Stock	(4)	10/13/2026		C			1,574,074	(4)	(4)	Common Stock	1,574,074	$ 0	0	I	By SV Life Sciences Fund VI, L.P.(1)
Series B Preferred Stock	(4)	10/13/2026		C			475,411	(4)	(4)	Common Stock	475,411	$ 0	0	I	By SV Life Sciences Fund VI, L.P.(1)
Series A Preferred Stock	(4)	10/13/2026		C			53,892	(4)	(4)	Common Stock	53,892	$ 0	0	I	By SV Life Sciences Fund VI Strategic Partners, L.P.(2)
Series B Preferred Stock	(4)	10/13/2026		C			16,277	(4)	(4)	Common Stock	16,277	$ 0	0	I	By SV Life Sciences Fund VI Strategic Partners, L.P.(2)
Series B Preferred Stock	(4)	10/13/2026		C			669,939	(4)	(4)	Common Stock	669,939	$ 0	0	I	By SV Trex Coinvestment, L.P.(3)

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
SVLSF VI, LLC 28 STATE STREET, SUITE 980 BOSTON, MA 02109		X
SV Life Sciences Fund VI (GP), L.P. 28 STATE STREET, SUITE 980 BOSTON, MA 02109		X
SV Life Sciences Fund VI, L.P. 28 STATE STREET, SUITE 980 BOSTON, MA 02109		X

Signatures

SVLSF VI, LLC By: Brent M. Faduski, Officer /s/ Brent M. Faduski		10/13/2026
**Signature of Reporting Person		Date
SV Life Sciences Fund VI (GP), L.P. By: SVLSF VI, LLC, its General Partner By: Brent M. Faduski, Officer /s/ Brent M. Faduski		10/13/2026
**Signature of Reporting Person		Date
SV Life Sciences Fund VI, L.P. By: SV Life Sciences Fund VI (GP), L.P., its General Partner By: SVLSF VI, LLC, its General Partner By: Brent M. Faduski, Officer /s/ Brent M. Faduski		10/13/2026
**Signature of Reporting Person		Date

Explanation of Responses:

*	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).
(1)	The shares are held directly by SV Life Sciences Fund VI, L.P. ("SV Fund VI"). SV Life Sciences Fund VI (GP), L.P. (the "GP LP") is the general partner of SV Fund VI, and SVLSF VI, LLC ("SVLSF") is the general partner of GP LP. Investment and voting decisions of SV Fund VI are made by the investment committee of SVLSF. Each of GP LP and SVLSF disclaims beneficial ownership except to the extent of its pecuniary interest, and this report is not an admission of beneficial ownership for any other purpose.
(2)	The shares are held directly by SV Life Sciences Fund VI Strategic Partners, L.P. ("SV Strategic Partners VI"). GP LP is the general partner of SV Strategic Partners VI, and SVLSF is the general partner of GP LP. Investment and voting decisions of SV Strategic Partners VI are made by the investment committee of SVLSF. Each of GP LP and SVLSF disclaims beneficial ownership except to the extent of its pecuniary interest, and this report is not an admission of beneficial ownership for any other purpose.
(3)	The shares are held directly by SV Trex Coinvestment, L.P. ("SV Coinvestment"). GP LP is the general partner of SV Coinvestment, and SVLSF is the general partner of GP LP. Investment and voting decisions of SV Coinvestment are made by the investment committee of SVLSF. Each of GP LP and SVLSF disclaims beneficial ownership and this report is not an admission of beneficial ownership for any other purpose.
(4)	On October 13, 2026, 3.8649 shares of preferred stock automatically converted into one share of common stock upon the closing of the issuer's initial public offering, for no additional consideration. The preferred stock has no expiration date.
(5)	Represents shares purchased by SV Fund VI in the issuer's initial public offering.
(6)	Represents shares purchased by SV Strategic Partners VI in the issuer's initial public offering.

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