Moleculin Biotech CEO receives 415,000 stock options

Moleculin Biotech's CEO and President received awards that vest 50% on grant and in 18 equal installments over 18 months.

Rhea-AI Filing Summary

Moleculin Biotech, Inc. CEO and President Walter V. Klemp received grants of 415,000 options and 415,000 restricted stock units on October 15, 2026. The options have a $0.3701 exercise price and expire October 15, 2036; 2,341,335 options were reported following the grant. On the same date, 207,500 restricted stock units converted into common shares, and 48,659 shares were withheld for taxes upon vesting at $0.3701 per share. The awards vest 50% on grant and the remaining 50% in 18 equal installments over 18 months.

Insider Trade Summary

207,500 shares exercised/converted

Exercise 5 txns

Insider KLEMP WALTER V

Role CEO and President

Type	Security	Shares	Price	Value
Grant/Award	Options (right to buy) F2, F3	415,000	--	--
Grant/Award	Restricted Stock Units F5, F2, F3, F4	415,000	--	--
Exercise	Restricted Stock Units F1, F3, F5	207,500	$0.00	$0.00
Exercise	Common Stock F1	207,500	--	--
Tax Withholding	Common Stock F2	48,659	$0.3701	$18K

Holdings After Transaction: Options (right to buy) — 2,341,335 contracts (Direct); Restricted Stock Units — 5,304,670 contracts (Direct); Common Stock — 723,181 shares (Direct)

Footnotes (5)

1. F1. Restricted stock units convert into common stock on a one-for-one basis.
2. F2. Shares withheld for payment of taxes upon vesting of restricted stock unit awards.
3. 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.
4. F4. Issued in connection with the reporting person's employment with the Company.
5. F5. Each restricted stock unit represents a contingent right to receive one shares of Company common stock.

Key Figures

Options granted: 415,000 options Option exercise price: $0.3701 per share Options held following grant: 2,341,335 options +4 more

7 metrics

Options granted 415,000 options October 15, 2026

Option exercise price $0.3701 per share Options granted October 15, 2026

Options held following grant 2,341,335 options Following the October 15, 2026 grant

Option expiration date October 15, 2036 Options granted October 15, 2026

Restricted stock units granted 415,000 restricted stock units October 15, 2026

Restricted stock units converted 207,500 restricted stock units Converted into common stock on October 15, 2026

Shares withheld for taxes 48,659 common shares Upon vesting on October 15, 2026

Key Terms

Restricted stock units, one-for-one basis, contingent right, exercise price

4 terms

Restricted stock units financial

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

Restricted stock units are a type of company reward where employees are promised shares of stock, but they only fully own these shares after meeting certain conditions, like staying with the company for a set time. They matter because they can become valuable assets and are often used to motivate employees to help the company succeed.

one-for-one basis financial

"convert into common stock on a one-for-one basis"

contingent right financial

"Each restricted stock unit represents a contingent right"

exercise price financial

"The options have a $0.3701 exercise price"

The exercise price is the fixed amount at which you can buy or sell an asset, like a stock, when using an options contract. It matters because it helps determine whether exercising the option will be profitable or not, depending on the current market price. Think of it as the set price you agree on today to buy or sell later.

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What awards did MBRX CEO and President Walter V. Klemp receive?

On October 15, 2026, Walter V. Klemp received 415,000 options and 415,000 restricted stock units. The options have a $0.3701 exercise price and an October 15, 2036 expiration date.

How many MBRX shares were withheld for taxes from Walter V. Klemp's RSUs?

48,659 common shares were withheld for taxes upon vesting on October 15, 2026, at $0.3701 per share. The restricted stock units convert into common stock on a one-for-one basis.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Available on EDGAR 10/16/2026 - 09:01 PM EDT Accepted by SEC EDGAR 10/16/2026 - 09:00 PM EDT Learn about SEC filing dates

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^*

KLEMP WALTER V

(Last) (First) (Middle)

C/O MOLECULIN BIOTECH, INC.

5300 MEMORIAL DR., SUITE 950

(Street)

HOUSTON TEXAS 77007

(City) (State) (Zip)

UNITED STATES

(Country)

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

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

X	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	CEO and President

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
10/15/2026

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

4. If Amendment, Date of Original Filed (Month/Day/Year)

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	10/15/2026		M		207,500	A	(1)	771,840	D
Common Stock	10/15/2026		F		48,659(2)	D	$0.3701	723,181	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
Options (right to buy)	$0.3701	10/15/2026		A		415,000		(3)	10/15/2036	Common Stock	415,000	(2)	2,341,335	D
Restricted Stock Units	(5)	10/15/2026		A		415,000		(3)	(4)	Common Stock	415,000	(2)	2,756,335	D
Restricted Stock Units	(1)	10/15/2026		M			207,500	(3)	(5)	Common Stock	208,000	$0	2,548,335	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 by Power of Attorney	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: SEC 1474 (03-26)