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Moleculin Biotech (MBRX) CSO exercises RSUs with tax withholding, increases common stock stake

Filing Impact
(Neutral)
Filing Sentiment
(Neutral)
Form Type
4

Rhea-AI Filing Summary

Moleculin Biotech, Inc. Chief Science Officer Donald H. Picker reported routine equity compensation activity involving restricted stock units (RSUs). On June 20 and June 22, he exercised RSUs to acquire a total of 115 shares of common stock at a conversion price of $0.00 per share.

Across both dates, 34 common shares were withheld at prices of $2.88 and $3.12 per share to cover tax obligations upon RSU vesting, a non‑market disposition. Following these transactions, he directly holds 774 shares of common stock and 19,596 RSUs that convert into common stock on a one‑for‑one basis.

Positive

  • None.

Negative

  • None.
Insider PICKER DONALD H
Role Chief Science Officer
Type Security Shares Price Value
Exercise Restricted Stock Units 71 $0.00 --
Exercise Common Stock 71 $0.00 --
Tax Withholding Common Stock 21 $3.12 $65.52
Exercise Restricted Stock Units 44 $0.00 --
Exercise Common Stock 44 $0.00 --
Tax Withholding Common Stock 13 $2.88 $37.44
Holdings After Transaction: Restricted Stock Units — 19,596 shares (Direct, null); Common Stock — 774 shares (Direct, null)
Footnotes (1)
  1. Restricted stock units convert into common stock on a one-for-one basis. Shares withheld for payment of taxes upon vesting of restricted stock unit awards. On June 20, 2022, the reporting person was granted 173 restricted stock units, vesting in four equal annual installments beginning on the first anniversary of the grant date. On June 22, 2023, the reporting person was granted 283 restricted stock units, vesting in four equal annual installments beginning on the first anniversary of the grant date.
RSU shares exercised 115 shares Total RSUs converted to common stock on June 20 and June 22
Shares withheld for taxes 34 shares Common shares withheld to cover tax obligations on RSU vesting
Tax withholding price 1 $2.88 per share Tax-withholding disposition of 13 shares on June 20
Tax withholding price 2 $3.12 per share Tax-withholding disposition of 21 shares on June 22
Common shares after transactions 774 shares Direct Moleculin common stock holdings following June 22 transactions
RSUs remaining 19,596 units Restricted stock units outstanding after June 22, one-for-one into common
RSUs exercised June 20 44 units Restricted stock units converted into common stock on June 20
RSUs exercised June 22 71 units Restricted stock units converted into common stock on June 22
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.
tax-withholding disposition financial
"transaction_action: tax-withholding disposition for payment of taxes."
A tax-withholding disposition is an event or transaction—such as selling or transferring securities, exercising options, or receiving compensation—that triggers a requirement to hold back part of the payment and remit it to tax authorities. It matters to investors because it reduces the cash they receive immediately and can change the timing and amount of taxable income, like a cashier taking a portion of your sale proceeds to pay taxes before you get the rest.
derivative security financial
"transaction_code_description: Exercise or conversion of derivative security."
A derivative security is a financial contract whose value comes from the price or performance of something else, such as a stock, bond, commodity, or market index. For investors it acts like an insurance policy or a wager: it can be used to protect against losses, lock in prices, or amplify gains and losses, so it can change a portfolio’s risk and potential return without owning the underlying asset directly.
vesting financial
"vesting in four equal annual installments beginning on the first anniversary of the grant date."
Vesting is the process by which you earn full ownership of something, like company stock or a retirement benefit, over time. It’s like earning the right to keep a gift piece by piece the longer you stay with a company, making sure employees stay committed before they receive all the benefits.
exercise price financial
"Payment of exercise price or tax liability by delivering securities."
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.
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Learn about SEC filing dates
SEC Form 4
FORM 4UNITED 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*
PICKER DONALD H

(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)
Director10% Owner
XOfficer (give title below)Other (specify below)
Chief Science Officer
2a. Foreign Trading Symbol
3. Date of Earliest Transaction (Month/Day/Year)
06/20/2026
6. Individual or Joint/Group Filing (Check Applicable Line)
XForm 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)
CodeVAmount(A) or (D)Price
Common Stock06/20/2026M44A(1)716D
Common Stock06/20/2026F13(2)D$2.88703D
Common Stock06/22/2026M71A(1)774D
Common Stock06/22/2026F21(2)D$3.12753D
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)
CodeV(A)(D)Date ExercisableExpiration DateTitleAmount or Number of Shares
Restricted Stock Units(1)06/20/2026M44 (3) (3)Common Stock44$019,667D
Restricted Stock Units(1)06/22/2026M71 (4) (4)Common Stock50$019,596D
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. On June 20, 2022, the reporting person was granted 173 restricted stock units, vesting in four equal annual installments beginning on the first anniversary of the grant date.
4. On June 22, 2023, the reporting person was granted 283 restricted stock units, vesting in four equal annual installments beginning on the first anniversary of the grant date.
/s/ Jonathan P. Foster by Power of Attorney06/24/2026
** Signature of Reporting PersonDate
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)

FAQ

What insider transactions did Moleculin Biotech (MBRX) report for Donald H. Picker?

Moleculin Biotech reported that Chief Science Officer Donald H. Picker exercised restricted stock units into common stock and had shares withheld to cover taxes. These transactions reflect routine equity compensation events rather than open-market buying or selling of Moleculin Biotech shares.

How many Moleculin Biotech (MBRX) shares did the CSO acquire through RSU exercises?

Donald H. Picker acquired 115 shares of Moleculin Biotech common stock by exercising restricted stock units. The RSUs converted into common stock at a stated price of $0.00 per share, reflecting vesting of previously granted equity awards rather than new cash purchases in the open market.

How many Moleculin Biotech (MBRX) shares were withheld for taxes in this Form 4?

A total of 34 Moleculin Biotech common shares were withheld to pay taxes upon RSU vesting. The tax-withholding dispositions occurred at prices of $2.88 and $3.12 per share, representing non-market mechanisms to satisfy tax obligations on equity compensation.

What are Donald H. Picker’s Moleculin Biotech (MBRX) holdings after these transactions?

After these transactions, Donald H. Picker directly holds 774 shares of Moleculin Biotech common stock and 19,596 restricted stock units. The RSUs convert into common stock on a one-for-one basis, indicating a substantial remaining equity-based compensation position with the company.

Were the Moleculin Biotech (MBRX) insider transactions open-market buys or sells?

The reported transactions were not open-market buys or sells. They involved exercising restricted stock units into common shares and withholding some shares to pay taxes. This pattern is typical of equity compensation vesting rather than discretionary trading in Moleculin Biotech stock.

What do the restricted stock units for Moleculin Biotech (MBRX) convert into?

The restricted stock units convert into Moleculin Biotech common stock on a one-for-one basis. Grants referenced in the footnotes were awarded in 2022 and 2023, vesting in four equal annual installments beginning one year after each grant date as part of ongoing compensation.