Moleculin Biotech CFO receives 260,000 stock options

Q: What equity awards did MBRX CFO Jonathan P. Foster receive?

Jonathan P. Foster received 260,000 stock options and 260,000 restricted stock units on October 15, 2026, in connection with his employment with Moleculin Biotech. The options are exercisable at $0.3701 per share and expire October 15, 2036.

Q: What is the vesting schedule for Jonathan P. Foster's MBRX awards?

The stock options and restricted stock units vest 50% on grant, with the remaining 50% vesting in 18 equal installments over 18 months.

Q: How many MBRX stock options did Jonathan P. Foster hold after the award?

The reported post-transaction position was 1,287,717 stock options.

The options and restricted stock units vest 50% on grant and 50% in 18 equal installments over 18 months.

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Form Type

Rhea-AI Filing Summary

Moleculin Biotech, Inc. Chief Financial Officer Jonathan P. Foster received an employment-related grant of 260,000 stock options, exercisable at $0.3701 per share and expiring October 15, 2036, plus 260,000 restricted stock units. On October 15, 2026, 130,000 RSUs converted one-for-one into common stock, and 30,485 shares were withheld for taxes upon vesting at $0.3701 per share. The options and RSUs vest 50% on grant and 50% in 18 equal installments over 18 months.

Insider Trade Summary

130,000 shares exercised/converted

Exercise 5 txns

Insider Foster Jonathan P.

Role Chief Financial Officer

Type	Security	Shares	Price	Value
Grant/Award	Stock Options (right to buy) ^{F4, F3}	260,000	--	--
Grant/Award	Restricted Stock Units ^{F5, F4, F3}	260,000	--	--
Exercise	Restricted Stock Units ^{F1, F3, F5}	130,000	$0.00	$0.00
Exercise	Common Stock ^F1	130,000	--	--
Tax Withholding	Common Stock ^F2	30,485	$0.3701	$11K

Holdings After Transaction: Stock Options (right to buy) — 1,287,717 contracts (Direct); Restricted Stock Units — 1,417,717 contracts (Direct); Common Stock — 405,188 shares (Direct)

Footnotes (5)

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.

Key Figures

Stock options granted: 260,000 options Option exercise price: $0.3701 per share Option expiration date: October 15, 2036 +5 more

8 metrics

Stock options granted 260,000 options Granted October 15, 2026

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

Option expiration date October 15, 2036 Stock options granted October 15, 2026

Restricted stock units granted 260,000 units Granted October 15, 2026

Restricted stock units converted 130,000 units Converted to common stock October 15, 2026

Common shares acquired on conversion 130,000 shares October 15, 2026

Shares withheld for taxes 30,485 shares Upon vesting at $0.3701 per share

Stock options following transaction 1,287,717 options Reported position after October 15, 2026 transaction

Key Terms

Restricted stock units, one-for-one basis, contingent right, vests

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"

vests financial

"vests as follows: (i) 50% on grant"

FAQ

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

What equity awards did MBRX CFO Jonathan P. Foster receive?

Jonathan P. Foster received 260,000 stock options and 260,000 restricted stock units on October 15, 2026, in connection with his employment with Moleculin Biotech. The options are exercisable at $0.3701 per share and expire October 15, 2036.

How many MBRX restricted stock units converted to common stock, and how many shares were withheld?

130,000 restricted stock units converted into 130,000 common shares on October 15, 2026. A further 30,485 shares were withheld for payment of taxes upon vesting, at $0.3701 per share.

What is the vesting schedule for Jonathan P. Foster's MBRX awards?

The stock options and restricted stock units vest 50% on grant, with the remaining 50% vesting in 18 equal installments over 18 months.

How many MBRX stock options did Jonathan P. Foster hold after the award?

The reported post-transaction position was 1,287,717 stock options.

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

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Available on EDGAR 10/16/2026 - 09:00 PM EDT Accepted by SEC EDGAR 10/16/2026 - 09:00 PM EDT

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

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)

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

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)
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: SEC 1474 (03-26)

Source: View Original Filing on SEC EDGAR