[Form 4] 89bio, Inc. Insider Trading Activity

Rhea-AI Filing Summary

89bio, Inc. (ETNB) filed a Form 4 disclosing that Chief Medical Officer Harry H. Mansbach satisfied tax withholding on vested RSUs.

• Date: 01-Aug-2025
• Transaction code F: 7,680 common shares automatically withheld for taxes at $9.16 per share.
• Shares now owned: 302,656 (direct ownership).

No open-market purchase or sale occurred and no derivative positions were reported. Code F events are routine administrative transactions and generally do not signal bullish or bearish intent.

Insights

Securities Analyst

TL;DR: Routine tax-withholding; insider maintains sizable stake—no directional signal.

The filing shows Mr. Mansbach used 7,680 shares to cover taxes upon RSU vesting, leaving 302,656 shares in direct ownership. Code F transactions are non-discretionary and do not reflect the insider’s market view. Given the modest share count (≈2.5% of his holdings) and lack of open-market activity, the market impact is minimal. Investors should treat this as administrative rather than a change in sentiment.

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
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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^*

Mansbach Harry H

(Last) (First) (Middle)

C/O 89BIO, INC.

655 MONTGOMERY STREET, SUITE 1500

(Street)

SAN FRANCISCO CA 94111

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
89bio, Inc. [ ETNB ]

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

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

3. Date of Earliest Transaction (Month/Day/Year)
08/01/2025

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	08/01/2025		F		7,680(1)	D	$9.16	302,656	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

Explanation of Responses:

1. These shares were withheld from the vesting of restricted stock units to cover the estimated tax withholding obligation.

	/s/ Ryan A. Murr, as attorney-in-fact for Harry H. Mansbach	08/05/2025
	** 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).
** 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.

FAQ

What insider activity did ETNB report on Form 4 dated 08/05/2025?

7,680 ETNB shares were withheld from CMO Harry Mansbach’s RSU vesting to pay taxes.

Did Harry Mansbach buy or sell ETNB shares in the open market?

No. The transaction was Code F—shares withheld; no open-market trade occurred.

How many ETNB shares does the CMO own after the transaction?

He owns 302,656 common shares directly.

Were any derivative securities involved in the filing?

No derivative positions were reported in Table II.

Why is a Code F transaction generally considered neutral for investors?

Because it reflects mandatory tax withholding, not a discretionary buy or sell decision.