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

Rhea-AI Filing Summary

Jonathan P. Foster, Chief Financial Officer of Moleculin Biotech (MBRX), reported multiple securities transactions on June 20-23, 2025:

• Acquired 2,711 shares from RSUs and had 661 shares withheld for taxes on June 20
• Acquired 4,328 shares from RSUs and had 1,054 shares withheld for taxes on June 22
• Purchased 270,270 common shares at $0.37 per share in a public offering on June 23
• Acquired Series E warrants to purchase 810,810 shares at $0.37/share, exercisable upon stockholder approval with 5-year expiration

Following these transactions, Foster directly owns 287,587 common shares and 1,038,320 derivative securities. The RSUs were granted in 2022 (10,846 units) and 2023 (17,313 units), vesting in four annual installments. This significant insider purchase demonstrates management's confidence in the company's prospects.

Positive

• CFO Jonathan Foster made a significant open market purchase of 270,270 shares at $0.37 per share (approximately $100,000), demonstrating strong insider confidence
• CFO acquired substantial Series E warrants to purchase 810,810 additional shares at $0.37, showing long-term commitment to the company's growth

Negative

• None.

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)
06/20/2025

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	06/20/2025		M		2,711	A	(1)	14,704	D
Common Stock	06/20/2025		F		661(2)	D	$0.267	14,043	D
Common Stock	06/22/2025		M		4,328	A	(1)	18,371	D
Common Stock	06/22/2025		F		1,054(2)	D	$0.267	17,317	D
Common Stock	06/23/2025		P		270,270	A	$0.37(5)	287,587	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)	06/20/2025		M			2,711	(3)	(3)	Common Stock	2,711	$0	231,838	D
Restricted Stock Units	(1)	06/22/2025		M			4,328	(4)	(4)	Common Stock	4,328	$0	227,510	D
Series E Warrants	$0.37	06/23/2025		P			810,810	(5)	(5)	Common Stock	810,810	(5)	1,038,320	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 20, 2022, the reporting person was granted 10,846 restricted stock units, vesting in four equal annual installments beginning on the first anniversary of the grant date.

4. On June 22, 2023, the reporting person was granted 17,313 restricted stock units, vesting in four equal annual installments beginning on the first anniversary of the grant date.

5. On June 23, 2025, the reporting person acquired 270,270 shares of common stock and Series E warrants to purchase 810,810 shares of common stock at a purchase price of $0.37 per share and accompanying warrants in a public offering. The Series E warrants will be exercisable beginning on the effective date of stockholder approval of the issuance of the shares upon exercise of the Series E warrants and will expire five years from the date of such approval.

	/s/ Jonathan P. Foster	06/23/2025
	** 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 transactions did MBRX CFO Jonathan Foster report on June 23, 2025?

MBRX CFO Jonathan Foster reported purchasing 270,270 shares of common stock at $0.37 per share and acquired Series E warrants to purchase 810,810 additional shares in a public offering on June 23, 2025. The warrants have an exercise price of $0.37 per share.

How many MBRX restricted stock units (RSUs) vested for Jonathan Foster in June 2025?

Two sets of RSUs vested for Jonathan Foster in June 2025: 2,711 units vested on June 20, 2025, and 4,328 units vested on June 22, 2025, for a total of 7,039 RSUs converting to common stock.

What is the total number of MBRX shares owned by CFO Jonathan Foster after all June 2025 transactions?

After all reported transactions in June 2025, Jonathan Foster directly owned 287,587 shares of MBRX common stock, plus Series E warrants for 810,810 additional shares and 227,510 remaining restricted stock units.

What are the terms of MBRX's Series E warrants issued in June 2025?

The Series E warrants have an exercise price of $0.37 per share and will be exercisable after stockholder approval of the shares issuance. They will expire five years from the date of such stockholder approval.

How many shares were withheld from MBRX CFO Foster's RSU vesting for tax purposes?

A total of 1,715 shares were withheld for tax purposes, consisting of 661 shares withheld on June 20, 2025, and 1,054 shares withheld on June 22, 2025, at a price of $0.267 per share.