Walter Klemp V - 15 Oct 2026 Form 4 Insider Report for Moleculin Biotech, Inc. (MBRX)

Reporting relationship: CEO and President, Director
Issuer ticker: MBRX
Reported as of: 15 Oct 2026
Net transaction value: $0
SEC form: 4
Accepted by SEC: 16 Oct 2026, 21:00:43 UTC
Prior SEC filing: 08 Sep 2026
Source filing: View source filing
Reporting owner signature: /s/ Jonathan P. Foster by Power of Attorney

Filing notes and source

Key filing fact

Walter Klemp V filed Form 4 for Moleculin Biotech, Inc. (MBRX) on 16 Oct 2026.

Key facts

This page summarizes Walter Klemp V'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 08 Sep 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 0000938419 Primary reporting owner

KLEMP WALTER V

Relationship: CEO and President, Director
Address: C/O MOLECULIN BIOTECH, INC., 5300 MEMORIAL DR., SUITE 950, HOUSTON
Signature: /s/ Jonathan P. Foster by Power of Attorney
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: +207,500
Change %: +37%
Price
Shares after: 771,840
Date: 15 Oct 2026
Ownership: Direct
Footnotes: F1

MBRX transaction

Common Stock

Tax liability

Transaction value
Shares: -48,659
Change %: -6.3%
Price: $0.3701^*
Shares after: 723,181
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

Options (right to buy)

Award

Transaction value
Shares: +415,000
Change %: +22%
Price
Shares after: 2,341,335
Date: 15 Oct 2026
Ownership: Direct
Underlying class: Common Stock
Underlying amount: 415,000
Exercise price: $0.3701
Footnotes: F2, F3

MBRX transaction Derivative

Restricted Stock Units

Award

Transaction value
Shares: +415,000
Change %: +18%
Price
Shares after: 2,756,335
Date: 15 Oct 2026
Ownership: Direct
Underlying class: Common Stock
Underlying amount: 415,000
Exercise price
Footnotes: F2, F3, F4, F5

MBRX transaction Derivative

Restricted Stock Units

Options Exercise

Transaction value
Shares: -207,500
Change %: -7.5%
Price: $0.000000^*
Shares after: 2,548,335
Date: 15 Oct 2026
Ownership: Direct
Underlying class: Common Stock
Underlying amount: 208,000
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.