Exercise4

Moleculin Biotech, Inc.

Total Value

$107.5K

Filing Date

Oct 16, 2026

1 transactions

Trade Summary

On Oct 15, 2026, Foster Jonathan P., Chief Financial Officer, reported $107.5K of Moleculin Biotech, Inc. (MBRX) across 1 transactions. The filing covers Common Stock and reflects balanced net activity of $0. Reported prices ranged from $0.37. Insider transactions are sourced from SEC Form 4 disclosures and should be reviewed alongside company fundamentals and the insider's broader trading history.

Insider Information

Name: Foster Jonathan P.
Role: Chief Financial Officer
Location: HOUSTON, TX

Filing Details

Filing Date: Oct 16, 2026
Transaction Date: Oct 15, 2026
Accession Number: 0001437749-26-032864
Form Type: 4

Non-Derivative Transactions

Date	Security	Shares	Price	Type	Value
Oct 15, 2026	Common Stock	130,000	—	Exercise	—
Oct 15, 2026	Common Stock	30,485	$0.37	Tax Withholding	$11.3K

Derivative Transactions

Date	Security	Shares	Exercise Price	Type	Value
Oct 15, 2026	MBRX derivative	260,000	$0.37	Grant/Award	$96.2K
Oct 15, 2026	MBRX derivative	260,000	—	Grant/Award	—
Oct 15, 2026	MBRX derivative	130,000	—	Exercise	—

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Footnotes

(F1)Restricted stock units convert into common stock on a one-for-one basis.
(F2)Shares withheld for payment of taxes upon vesting of restricted stock unit awards.
(F3)The stock option/restricted stock unit set forth in this table vests as follows: (i) 50% on grant; and (ii) 50% in 18 equal installments over 18 months.
(F4)Issued in connection with the reporting person's employment with the Company.
(F5)Each restricted stock unit represents a contingent right to receive one shares of Company common stock.

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

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)
10/15/2026

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)
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	Code	V	Amount	(A) or (D)	Price		6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
Common Stock	10/15/2026		M		130,000	A	⁽¹⁾	435,673	D
Common Stock	10/15/2026		F		30,485⁽²⁾	D	$0.3701	405,188	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)
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)	Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	8. Price of Derivative Security (Instr. 5)		10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
Stock Options (right to buy)	$0.3701	10/15/2026		A		260,000		⁽³⁾	10/15/2036	Common Stock	260,000	⁽⁴⁾	1,287,717	D
Restricted Stock Units	⁽⁵⁾	10/15/2026		A		260,000		⁽³⁾	⁽⁵⁾	Common Stock	260,000	⁽⁴⁾	1,547,717	D
Restricted Stock Units	⁽¹⁾	10/15/2026		M			130,000	⁽³⁾	⁽⁵⁾	Common Stock	130,000	$0	1,417,717	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. The stock option/restricted stock unit set forth in this table vests as follows: (i) 50% on grant; and (ii) 50% in 18 equal installments over 18 months.

4. Issued in connection with the reporting person's employment with the Company.

5. Each restricted stock unit represents a contingent right to receive one shares of Company common stock.

	/s/ Jonathan P. Foster	10/16/2026
	** 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.

Form 4 as rendered by the SEC from accession 0001437749-26-032864.

Moleculin Biotech, Inc.

Trade Summary

Company Information

Insider Information

Filing Details

Non-Derivative Transactions

Derivative Transactions

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Footnotes

SEC Form 4

SEC Filing

SEC Form 4