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SCHEDULE 13D Filed 2026-08-25 Event 2026-08-19 SEC 0001437749-26-028927 →

Foster Jonathan P. Moleculin Biotech, Inc. MBRX

Stake: 6.30% Shares: 1,288,207 CUSIP: 60855D408 Class: Common Stock, par value $0.001 per share

Item 4 — Purpose of Transaction

On August 3, 2026, the Reporting Person purchased 293,333 shares of Common Stock and Common Warrants to purchase up to 879,999 shares of Common Stock for investment purposes. Additional information regarding this transaction is provided above in Item 3. The Reporting Person reserves the right to acquire, or cause to be acquired, additional securities of the Issuer, to dispose of, or cause to be disposed of, such securities at any time or to formulate other purposes, plans or proposals regarding the Issuer or any of its securities, to the extent deemed advisable in light of general investment and trading policies of the Reporting Person, market conditions or other factors. Except as set forth in this Schedule 13D, the Reporting Person does not have any plan or proposal that would relate to, or result in: (a) the acquisition by any person of additional securities of the Issuer, or the disposition of securities of the Issuer; (b) an extraordinary corporate transaction, such as a merger, reorganization or liquidation, involving the Issuer or any of its subsidiaries; (c) a sale or transfer of a material amount of assets of the Issuer or of any of its subsidiaries; (d) any change in the present board of directors or management of the Issuer, including any plans or proposals to change the number or term of directors or to fill any existing vacancies on the board; (e) any material change in the present capitalization or dividend policy of the Issuer; (f) any other material change in the Issuer's business or corporate structure; (g) changes in the Issuer's charter, bylaws or instruments corresponding thereto or other actions which may impede the acquisition of control of the Issuer by any person; (h) causing a class of securities of the Issuer to be delisted from a national securities exchange or to cease to be authorized to be quoted in an inter-dealer quotation system of a registered national securities association; (i) a class of equity securities of the Issuer becoming eligible for termination of registration pursuant to Section 12(g)(4) of the Securities Exchange Act of 1934; or (j) any action similar to any of those enumerated above. The Reporting Person reserves the right to propose or participate in future transactions which may result in one or more of the above listed actions, including but not limited to, an extraordinary corporate transaction, such as a merger, reorganization or liquidation, sale of a material amount of assets of the Issuer or its subsidiaries, or other transactions which might have the effect of causing the Common Stock to become eligible for termination of registration under Section 12(g) of the Act. The Reporting Person also retains the right to change his investment intent at any time, to acquire additional Common Stock or other securities of the Issuer from time to time, or to sell or otherwise dispose of all or part of the Common Stock beneficially owned by him (or any Common Stock into which such securities are converted) in any manner permitted by law. The Reporting Person may engage from time to time in ordinary course transactions with financial institutions with respect to the securities described herein. The Reporting Person is the Executive Vice President and Chief Financial Officer of the Issuer. In such capacity, Mr. Foster may have influence over the corporate activities of the Issuer, including activities that may relate to the matters described in this Item 4. Without limiting the foregoing, on August 24, 2026 the Issuer filed a definitive proxy statement for its 2026 annual meeting of stockholders, which includes proposals relating to the election of directors, an increase in the number of shares reserved for issuance under the Issuer's 2024 Equity Incentive Plan, an amendment to the Issuer's certificate of incorporation to eliminate certain supermajority voting requirements, and an amendment to the Issuer's certificate of incorporation to effect a reverse stock split. Mr. Foster participated in the preparation of those proposals in his capacity as an executive officer of the Issuer. Additionally, the Reporting Person acquired securities of the Issuer as compensatory equity awards pursuant to the Issuer's equity incentive plans in connection with his service as an employee of the Issuer.

Cross-References

Insider Activity (last 365d)
17 transactions
11 buys · 0 sales · 4 awards/exercises
Issuer Cluster
3 13D/G filings on this issuer
2 other filings besides this one
Filer Track Record
1 filings by this filer
0 other filings in the data moat
Short Interest · settle 2026-08-14
DTC 1.00
316,392 shares short · -79.9% vs prior

Form 4 Insider Transactions · last 365d

DateInsiderRoleTypeSharesPriceValue
2025-11-12 PICKER DONALD H officer Award 200,000 $0.49 $98K
2025-11-12 Foster Jonathan P. officer Award 600,000 $0.49 $294K
2025-11-12 KLEMP WALTER V director, officer Award 830,000 $0.49 $407K
2025-11-12 Yan Joy director Award 150,000 $0.49 $74K
2025-11-12 Cermak Elizabeth director Award 150,000 $0.49 $74K
2025-11-12 CANNON MICHAEL D director Award 150,000 $0.49 $74K
2025-11-12 Climaco John M director Award 150,000 $0.49 $74K
2025-11-12 George Robert E. director Award 150,000 $0.49 $74K
2025-11-12 KLEMP WALTER V director, officer Award 750,000
2025-11-12 Foster Jonathan P. officer Award 400,000
2025-11-12 PICKER DONALD H officer Award 200,000
2025-11-04 PICKER DONALD H officer Option exercise 8,750
2025-11-04 KLEMP WALTER V director, officer Option exercise 28,750
2025-11-04 Foster Jonathan P. officer Option exercise 20,625
2025-11-04 Foster Jonathan P. officer Option exercise 5,023 $0.50 $2K
2025-11-04 KLEMP WALTER V director, officer F 7,001 $0.50 $3K
2025-11-04 PICKER DONALD H officer F 2,131 $0.50 $1K

Other 13D/G Filings on Moleculin Biotech, Inc.

FiledFormFilerStakeShares
2026-08-25 SCHEDULE 13D KLEMP WALTER V 9.90% 2,070,761 view →
2018-01-08 SC SABBY MANAGEMENT, LLC view →

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