Jonathan P. Foster - 15 Oct 2026 Form 4 Insider Report for Moleculin Biotech, Inc. (MBRX)

Reporting relationship: Chief Financial Officer
Issuer ticker: MBRX
Reported as of: 15 Oct 2026
Net transaction value: $0
SEC form: 4
Accepted by SEC: 16 Oct 2026, 21:00:18 UTC
Prior SEC filing: 05 Aug 2026
Next SEC filing: 06 Nov 2026
Source filing: View source filing
Reporting owner signature: /s/ Jonathan P. Foster

Filing notes and source

Key filing fact

Jonathan P. Foster filed Form 4 for Moleculin Biotech, Inc. (MBRX) on 16 Oct 2026.

Key facts

This page summarizes Jonathan P. Foster's Form 4 filing for Moleculin Biotech, Inc. (MBRX).
5 reported transactions and 3 derivative rows are listed below.
Accepted by SEC: 16 Oct 2026, 21:00.

Change

Previous filing in this sequence was filed on 05 Aug 2026.
Current net transaction value: $0.

Research use

This tells you what this filing adds before you inspect full transaction and derivative tables.
You can trace every row back to the original SEC filing document.

Evidence

Filed on Form 4

Ownership activity is grounded in SEC Form 4 disclosures.

View source filing

Reporting Owners (1)

CIK 0001545414 Primary reporting owner

Foster Jonathan P.

Relationship: Chief Financial Officer
Address: C/O MOLECULIN BIOTECH, INC., 5300 MEMORIAL DR., SUITE 950, HOUSTON
Signature: /s/ Jonathan P. Foster
Signature date: 16 Oct 2026

Reported non-derivative transactions

Shares, units, or other non-derivative securities reported in this filing.

MBRX transaction

Common Stock

Options Exercise

Transaction value
Shares: +130,000
Change %: +43%
Price
Shares after: 435,673
Date: 15 Oct 2026
Ownership: Direct
Footnotes: F1

MBRX transaction

Common Stock

Tax liability

Transaction value
Shares: -30,485
Change %: -7%
Price: $0.3701^*
Shares after: 405,188
Date: 15 Oct 2026
Ownership: Direct
Footnotes: F2

Reported derivative securities

Options, warrants, convertible securities, or similar derivative positions disclosed in the filing.

MBRX transaction Derivative

Stock Options (right to buy)

Award

Transaction value
Shares: +260,000
Change %: +25%
Price
Shares after: 1,287,717
Date: 15 Oct 2026
Ownership: Direct
Underlying class: Common Stock
Underlying amount: 260,000
Exercise price: $0.3701
Footnotes: F3, F4

MBRX transaction Derivative

Restricted Stock Units

Award

Transaction value
Shares: +260,000
Change %: +20%
Price
Shares after: 1,547,717
Date: 15 Oct 2026
Ownership: Direct
Underlying class: Common Stock
Underlying amount: 260,000
Exercise price
Footnotes: F3, F4, F5

MBRX transaction Derivative

Restricted Stock Units

Options Exercise

Transaction value
Shares: -130,000
Change %: -8.4%
Price: $0.000000^*
Shares after: 1,417,717
Date: 15 Oct 2026
Ownership: Direct
Underlying class: Common Stock
Underlying amount: 130,000
Exercise price
Footnotes: F1, F3, F5

^* marks a reported price that did not pass the local price check.

Additional SEC filing notes

Filing notes and footnotes

Explanation of responses 5 footnotes

Footnote F1

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

Footnote F2

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

Footnote 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.

Footnote F4

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

Footnote F5

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