[Form 4] Moleculin Biotech, Inc. Insider Trading Activity

Rhea-AI Filing Summary

Jonathan P. Foster, Chief Financial Officer of Moleculin Biotech (MBRX), reported insider transactions on June 16, 2025:

• Acquired 833 shares of common stock through the conversion of Restricted Stock Units (RSUs)
• Disposed of 203 shares at $0.6852 per share for tax withholding
• Following these transactions, Foster directly owns 11,993 shares of common stock
• Maintains 230,684 RSUs from a June 16, 2021 grant of 3,334 units that vest in four equal annual installments

These transactions represent routine vesting of executive compensation RSUs rather than open market purchases or sales. The tax-related share withholding is a standard practice for handling tax obligations from equity compensation vesting.

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^*

Foster Jonathan P.

(Last) (First) (Middle)

C/O MOLECULIN BIOTECH, INC.

5300 MEMORIAL DR., SUITE 950

(Street)

HOUSTON TX 77007

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
Moleculin Biotech, Inc. [ MBRX ]

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

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

3. Date of Earliest Transaction (Month/Day/Year)
06/16/2025

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	06/16/2025		M		833	A	(1)	12,196	D
Common Stock	06/16/2025		F		203(2)	D	$0.6852	11,993	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
Restricted Stock Units	(1)	06/16/2025		M			833	(3)	(3)	Common Stock	833	$0	230,684	D

Explanation of Responses:

1. Restricted stock units convert into common stock on a one-for-one basis.

2. Shares withheld for payment of taxes upon vesting of restricted stock unit awards.

3. On June 16, 2021, the reporting person was granted 3,334 restricted stock units, vesting in four equal annual installments beginning on the first anniversary of the grant date.

	/s/ Jonathan P. Foster	06/18/2025
	** 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 trading activity occurred at MBRX on June 16, 2025?

On June 16, 2025, MBRX's Chief Financial Officer Jonathan P. Foster acquired 833 shares of common stock through the vesting of restricted stock units (RSUs). He subsequently disposed of 203 shares at $0.6852 per share for tax withholding purposes, resulting in a final beneficial ownership of 11,993 shares held directly.

How many restricted stock units (RSUs) does MBRX's CFO Jonathan Foster own after the June 2025 transaction?

Following the reported transaction, Jonathan Foster owns 230,684 restricted stock units (RSUs) of MBRX. These RSUs convert to common stock on a one-for-one basis.

What is the vesting schedule for MBRX CFO's restricted stock units granted in 2021?

The restricted stock units were granted on June 16, 2021, with a total of 3,334 RSUs vesting in four equal annual installments beginning on the first anniversary of the grant date.

What was the purpose of MBRX CFO's stock disposition in June 2025?

The disposition of 203 shares was specifically for tax withholding purposes upon the vesting of restricted stock unit awards, sold at a price of $0.6852 per share.