MBRX / Moleculin Biotech, Inc. - Arquivamentos da SEC, Relatório Anual, Declaração de Procuração

Independent Market Research Finds Strong Physician Intent to Prescribe Moleculin's Annamycin in Relapsed/Refractory AML Surveyed oncologists reported high likelihood to prescribe (6 of 7), citing deep remissions, transplant-bridging potential, biomar

EXHIBIT 99.1 Independent Market Research Finds Strong Physician Intent to Prescribe Moleculin's Annamycin in Relapsed/Refractory AML Surveyed oncologists reported high likelihood to prescribe (6 of 7), citing deep remissions, transplant-bridging potential, biomarker-agnostic use and reduced cardiotoxicity as key drivers Parallel survey of payers shows strong support for Annamycin filling a signifi

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): June 5, 2026 MOLECULIN BIOTECH, I

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): June 5, 2026 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organization

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): May 29, 2026 MOLECULIN BIOTECH, I

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): May 29, 2026 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organization

Moleculin Presents ASCO 2026 Data Demonstrating No Detectable Cardiotoxicity with Annamycin Despite Exposure Levels Far Exceeding Conventional Anthracycline Limits Independent Cleveland Clinic Cardiac Review Supports Potential Best-in-Class Safety Pr

Exhibit 99.1 Moleculin Presents ASCO 2026 Data Demonstrating No Detectable Cardiotoxicity with Annamycin Despite Exposure Levels Far Exceeding Conventional Anthracycline Limits Independent Cleveland Clinic Cardiac Review Supports Potential Best-in-Class Safety Profile as MIRACLE Phase 2b/3 Trial Advances HOUSTON, May 29, 2026 /PRNewswire/ - Moleculin Biotech, Inc., (Nasdaq: MBRX) (“Moleculin” or t

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): May 26, 2026 MOLECULIN BIOTECH, I

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): May 26, 2026 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organization

EXHIBIT 99.1

Exhibit 99.1

Moleculin Highlights Abstract Accepted for Poster Presentation at the 2026 ASCO Annual Meeting Highlighting Cardiac Safety Data for Annamycin

Exhibit 99.1 Moleculin Highlights Abstract Accepted for Poster Presentation at the 2026 ASCO Annual Meeting Highlighting Cardiac Safety Data for Annamycin HOUSTON, May 21, 2026 /PRNewswire/ - Moleculin Biotech, Inc., (Nasdaq: MBRX) (“Moleculin” or the “Company”), today announced that an abstract featuring pooled cardiac safety data for its lead drug candidate Annamycin (also known as “L-Annamycin”

EXHIBIT 99.2

Exhibit 99.2

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): May 22, 2026 MOLECULIN BIOTECH, I

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): May 22, 2026 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organization

Moleculin Reports First Quarter 2026 Financial Results and Provides Clinical Update on Pivotal MIRACLE Trial Early blinded results show 40% composite complete remission rate across difficult-to-treat AML patient population in MIRACLE Trial First inte

Exhibit 99.1 Moleculin Reports First Quarter 2026 Financial Results and Provides Clinical Update on Pivotal MIRACLE Trial Early blinded results show 40% composite complete remission rate across difficult-to-treat AML patient population in MIRACLE Trial First interim unblinding expected in June 2026 following 45 subject enrollment milestone achieved in MIRACLE trial Enrollment in MIRACLE trial cont

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): May 15, 2026 MOLECULIN BIOTECH, I

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): May 15, 2026 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organization

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2026 ☐ TRANSITION REPORT PURSUANT TO

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2026 or ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number: 001-37758 MO

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): May 13, 2026 MOLECULIN BIOTECH, I

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): May 13, 2026 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organization

Moleculin Announces Imminent MIRACLE Trial Unblinding as Blinded Data Continue to Significantly Outperform Historical Benchmarks Preliminary blinded CR rate for the first 45 subjects in the trial approximates 30% and represents ~67% improvement vs. s

Exhibit 99.1 Moleculin Announces Imminent MIRACLE Trial Unblinding as Blinded Data Continue to Significantly Outperform Historical Benchmarks Preliminary blinded CR rate for the first 45 subjects in the trial approximates 30% and represents ~67% improvement vs. standard of care First 45-subject data unblinding expected before June 30, 2026 Program targets high-unmet-need AML population, including

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): May 12, 2026 MOLECULIN BIOTECH, I

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): May 12, 2026 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organization

Independent Cleveland Clinic Review Finds No Clinically Significant Cardiotoxicity with Moleculin's Annamycin in R/R AML Patients Dosed Beyond Conventional Anthracycline Limits Pooled analysis of 90 subjects across 5 trials shows stable mean ejection

Exhibit 99.1 Independent Cleveland Clinic Review Finds No Clinically Significant Cardiotoxicity with Moleculin's Annamycin in R/R AML Patients Dosed Beyond Conventional Anthracycline Limits Pooled analysis of 90 subjects across 5 trials shows stable mean ejection fraction and no clinically significant left ventricular dysfunction Data demonstrates Annamycin addresses the principal barrier to anthr

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): May 8, 2026 MOLECULIN BIOTECH, IN

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): May 8, 2026 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organization)

Moleculin Biotech Secures Strategic Additional Patent, Strengthening Global Positioning of Annamycin Solid Intellectual Property Protection Across Four Continents Ahead of Pending Phase 3 Data Release

Exhibit 99.1 Moleculin Biotech Secures Strategic Additional Patent, Strengthening Global Positioning of Annamycin Solid Intellectual Property Protection Across Four Continents Ahead of Pending Phase 3 Data Release HOUSTON, May 8, 2026 /PRNewswire/ - Moleculin Biotech, Inc., (Nasdaq: MBRX) (“Moleculin” or the “Company”), today announced a significant advancement in its intellectual property portfol

EXHIBIT 99.2

Exhibit 99.2

Moleculin’s Annamycin Extends Survival by More Than 60% in Metastatic Pancreatic Cancer Preclinical Models - Data Presented at AACR 2026 Non-cardiotoxic anthracycline demonstrates activity where traditional chemotherapies have historically failed, su

Exhibit 99.1 Moleculin’s Annamycin Extends Survival by More Than 60% in Metastatic Pancreatic Cancer Preclinical Models - Data Presented at AACR 2026 Non-cardiotoxic anthracycline demonstrates activity where traditional chemotherapies have historically failed, supporting potential expansion of Annamycin into a major unmet-need indication Significant tumor volume reduction across multiple PDAC mode

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): April 23, 2026 MOLECULIN BIOTECH,

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): April 23, 2026 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organizati

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): April 15, 2026 MOLECULIN BIOTECH,

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): April 15, 2026 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organizati

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 10-K/A (Amendment No. 1) ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 December 31, 2025 ☐ TRANSITION REPORT PURSUANT TO SECTION 13

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 10-K/A (Amendment No. 1) ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 December 31, 2025 or ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF For the transition period from to Commission File Number: 001-37758 Moleculin Biotech,

MOLECULIN BIOTECH, INC. Up to 6,367,956 Shares of Common Stock

Filed Pursuant to Rule 424(b)(3) Registration No. 333-294686 PROSPECTUS MOLECULIN BIOTECH, INC. Up to 6,367,956 Shares of Common Stock This prospectus relates to the resale, from time to time, by the selling stockholders (the “Selling Stockholders”) identified in this prospectus under the caption “Selling Stockholders,” of up to 6,367,956 shares of our common stock upon the exercise of certain war

Moleculin Biotech, Inc. 5300 Memorial Drive, Suite 950 Houston, TX 77007 April 10, 2026

Moleculin Biotech, Inc. 5300 Memorial Drive, Suite 950 Houston, TX 77007 April 10, 2026 VIA EDGAR U.S. Securities and Exchange Commission Division of Corporate Finance Washington, DC 20549 Attention: Doris Stacey Gama Re: Moleculin Biotech, Inc. Registration Statement on Form S-3 Filed March 27, 2026 File No. 333-294686 Ladies and Gentlemen: Pursuant to Rule 461 of the Securities Act of 1933, as a

LETTER

April 2, 2026 Walter V. Klemp Chief Executive Officer Moleculin Biotech, Inc. 5300 Memorial Drive Suite 950 Houston, TX 77007 Re: Moleculin Biotech, Inc. Registration Statement on Form S-3 Filed March 27, 2026 File No. 333-294686 Dear Walter V. Klemp: This is to advise you that we have not reviewed and will not review your registration statement. Please refer to Rules 460 and 461 regarding request

Security Type

Calculation of Filing Fee Tables S-3 Moleculin Biotech, Inc. Table 1: Newly Registered and Carry Forward Securities ☐Not Applicable Security Type Security Class Title Fee Calculation or Carry Forward Rule Amount Registered Proposed Maximum Offering Price Per Unit Maximum Aggregate Offering Price Fee Rate Amount of Registration Fee Carry Forward Form Type Carry Forward File Number Carry Forward Ini

As filed with the Securities and Exchange Commission on March 27, 2026

Table of Contents As filed with the Securities and Exchange Commission on March 27, 2026 Registration No.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): March 23, 2026 MOLECULIN BIOTECH,

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): March 23, 2026 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organizati

Moleculin Hits 45 Subject Enrollment Milestone, Triggering Final Countdown to Mid-2026 MIRACLE Trial Data Readout

Exhibit 99.1 Moleculin Hits 45 Subject Enrollment Milestone, Triggering Final Countdown to Mid-2026 MIRACLE Trial Data Readout - First Interim Unblinding of Pivotal AML Trial Now Imminent — Potentially the Most Important Data Moment in Company History - Early Blinded Results Show 40% Remission Rate Across Difficult-to-Treat Patient Population - Enrollment Accelerating Toward 90 Subject Threshold a

EXHIBIT 99.1

Exhibit 99.1

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): March 19, 2026 MOLECULIN BIOTECH,

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): March 19, 2026 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organizati

Moleculin Reports Full Year 2025 Financial Results and Confirms Highly Anticipated 45-Patient Interim Data Unblinding in Pivotal MIRACLE Trial On Track for Mid-2026

Exhibit 99.1 Moleculin Reports Full Year 2025 Financial Results and Confirms Highly Anticipated 45-Patient Interim Data Unblinding in Pivotal MIRACLE Trial On Track for Mid-2026 - Miracle Trial Preliminary Blinded CRc Rate of 40% in First 30 Patients Suggests Encouraging Early Results in Relapsed/Refractory AML HOUSTON, March 19, 2026 /PRNewswire/ - Moleculin Biotech, Inc., (Nasdaq: MBRX) (“Molecu

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): March 19, 2026 MOLECULIN BIOTECH,

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): March 19, 2026 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organizati

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 10-K ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2025 ☐ TRANSITION REPORT PURSUANT TO SECTI

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 10-K ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2025 or ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number: 001-37758 Molecul

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. )

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. )

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): February 19, 2026 MOLECULIN BIOTE

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): February 19, 2026 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organiz

MOLECULIN BIOTECH, INC.

Exhibit 10.1 MOLECULIN BIOTECH, INC. February 19, 2026 Holder of Common Stock Purchase Warrants Re: Inducement Offer to Exercise Common Stock Purchase Warrants Dear Holder: Moleculin Biotech, Inc. (the “Company”) is pleased to offer to you (“Holder”, “you” or similar terminology) the opportunity to receive new warrants to purchase shares of the Company’s common stock, par value $0.001 per share (t

SERIES H COMMON STOCK PURCHASE WARRANT MOLECULIN BIOTECH, INC.

Exhibit 4.1 NEITHER THIS SECURITY NOR THE SECURITIES FOR WHICH THIS SECURITY IS EXERCISABLE HAVE BEEN REGISTERED WITH THE SECURITIES AND EXCHANGE COMMISSION OR THE SECURITIES COMMISSION OF ANY STATE IN RELIANCE UPON AN EXEMPTION FROM REGISTRATION UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE “SECURITIES ACT”), AND, ACCORDINGLY, MAY NOT BE OFFERED OR SOLD EXCEPT PURSUANT TO AN EFFECTIVE REGISTR

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): February 18, 2026 MOLECULIN BIOTE

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): February 18, 2026 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organiz

Moleculin MIRACLE Trial Delivers 40% Preliminary Blinded CRc Rate (n=30) Preliminary blinded CR rate 67% improvement over historical cytarabine response Roughly 35% of the subjects treated to date represent ventoclax regimen failures First 45 treated

Exhibit 99.1 Moleculin MIRACLE Trial Delivers 40% Preliminary Blinded CRc Rate (n=30) Preliminary blinded CR rate 67% improvement over historical cytarabine response Roughly 35% of the subjects treated to date represent ventoclax regimen failures First 45 treated subjects on track for Q1 2026 milestone with unblinding thereafter – treated 35 subjects to date with another 11 identified Continued ab

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): February 18, 2026 MOLECULIN BIOTE

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): February 18, 2026 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organiz

EXHIBIT 99.1

Exhibit 99.1

Moleculin Announces Notice of Allowance for Japanese Patent Covering Annamycin

Exhibit 99.1 Moleculin Announces Notice of Allowance for Japanese Patent Covering Annamycin HOUSTON, February 17, 2026 /PRNewswire/ - Moleculin Biotech, Inc., (Nasdaq: MBRX) (“Moleculin” or the “Company”), today announced that the Japan Patent Office (JPO) has issued a notice of allowance for Patent Application No. 2021-577862 titled, “METHOD OF RECONSTITUTING LIPOSOMAL ANNAMYCIN.” A patent from t

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): February 17, 2026 MOLECULIN BIOTE

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): February 17, 2026 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organiz

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): February 5, 2026 MOLECULIN BIOTEC

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): February 5, 2026 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organiza

EXHIBIT 99.1

Exhibit 99.1

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): January 20, 2026 MOLECULIN BIOTEC

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): January 20, 2026 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organiza

Moleculin Reports Independent Assessment Confirms No Cardiotoxicity of Annamycin in 90 Subjects – Annamycin consistently demonstrates no evidence of cardiotoxicity across five clinical trials – This next-generation anthracycline demonstrates safety a

Exhibit 99.1 Moleculin Reports Independent Assessment Confirms No Cardiotoxicity of Annamycin in 90 Subjects – Annamycin consistently demonstrates no evidence of cardiotoxicity across five clinical trials – This next-generation anthracycline demonstrates safety and promising early activity in treating multiple oncology indications HOUSTON, January 13, 2026 — Moleculin Biotech, Inc., (Nasdaq: MBRX)

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): January 13, 2026 MOLECULIN BIOTEC

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): January 13, 2026 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organiza

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): January 12, 2026 MOLECULIN BIOTEC

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): January 12, 2026 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organiza

Moleculin Accelerates Outlook Into 2026 With First Pivotal Trial Unblinding on Track, Global Trial Expansion, and Multiple Externally/IIT Funded Clinical Programs – First MIRACLE trial unblinding expected Q1 2026; Global trial now spans nine countrie

Exhibit 99.1 Moleculin Accelerates Outlook Into 2026 With First Pivotal Trial Unblinding on Track, Global Trial Expansion, and Multiple Externally/IIT Funded Clinical Programs – First MIRACLE trial unblinding expected Q1 2026; Global trial now spans nine countries – Investigator-Initiated (IIT) funded pancreatic and brain cancer trials HOUSTON, January 12, 2026 /PRNewswire/ - Moleculin Biotech, In

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): January 7, 2026 MOLECULIN BIOTECH

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): January 7, 2026 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organizat

LETTER

January 2, 2026 Walter V. Klemp Chief Executive Officer Moleculin Biotech, Inc. 5300 Memorial Drive, Suite 950 Houston, TX 77007 Re: Moleculin Biotech, Inc. Registration Statement on Form S-3 Filed December 23, 2025 File No. 333-292420 Dear Walter V. Klemp: This is to advise you that we have not reviewed and will not review your registration statement. Please refer to Rules 460 and 461 regarding r

Moleculin Biotech, Inc. 5300 Memorial Drive, Suite 950 Houston, TX 77007

Moleculin Biotech, Inc. 5300 Memorial Drive, Suite 950 Houston, TX 77007 January 2, 2026 VIA EDGAR U.S. Securities and Exchange Commission Division of Corporate Finance Washington, DC 20549 Attention: Jessica Dickerson Re: Moleculin Biotech, Inc. Registration Statement on Form S-1 Registration No. 333-292420 Ladies and Gentlemen: Pursuant to Rule 461 of the Securities Act of 1933, as amended, Mole

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. )

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.

Security Type

Calculation of Filing Fee Tables S-3 Moleculin Biotech, Inc. Table 1: Newly Registered and Carry Forward Securities ☐Not Applicable Security Type Security Class Title Fee Calculation or Carry Forward Rule Amount Registered Proposed Maximum Offering Price Per Unit Maximum Aggregate Offering Price Fee Rate Amount of Registration Fee Carry Forward Form Type Carry Forward File Number Carry Forward Ini

Moleculin Biotech, Inc. Up to $8,200,000 Common Stock

Filed Pursuant to Rule 424(b)(5) Registration No. 333-280064 Prospectus Supplement No. 1 (to Prospectus dated July 1, 2024) Moleculin Biotech, Inc. Up to $8,200,000 Common Stock We have previously entered into an At The Market Offering Agreement (“ATM Agreement”) with Roth Capital Partners, LLC (“Roth”) relating to shares of our common stock offered by this prospectus supplement and the prospectus

As filed with the Securities and Exchange Commission on December 23, 2025

Table of Contents As filed with the Securities and Exchange Commission on December 23, 2025 Registration No.

AMENDED AND RESTATED SERIES G COMMON STOCK PURCHASE WARRANT MOLECULIN BIOTECH, INC.

Exhibit 4.3 NEITHER THIS SECURITY NOR THE SECURITIES FOR WHICH THIS SECURITY IS EXERCISABLE HAVE BEEN REGISTERED WITH THE SECURITIES AND EXCHANGE COMMISSION OR THE SECURITIES COMMISSION OF ANY STATE IN RELIANCE UPON AN EXEMPTION FROM REGISTRATION UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE “SECURITIES ACT”), AND, ACCORDINGLY, MAY NOT BE OFFERED OR SOLD EXCEPT PURSUANT TO AN EFFECTIVE REGISTR

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): December 21, 2025 MOLECULIN BIOTE

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): December 21, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organiz

AMENDED AND RESTATED SERIES F COMMON STOCK PURCHASE WARRANT MOLECULIN BIOTECH, INC.

Exhibit 4.2 NEITHER THIS SECURITY NOR THE SECURITIES FOR WHICH THIS SECURITY IS EXERCISABLE HAVE BEEN REGISTERED WITH THE SECURITIES AND EXCHANGE COMMISSION OR THE SECURITIES COMMISSION OF ANY STATE IN RELIANCE UPON AN EXEMPTION FROM REGISTRATION UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE “SECURITIES ACT”), AND, ACCORDINGLY, MAY NOT BE OFFERED OR SOLD EXCEPT PURSUANT TO AN EFFECTIVE REGISTR

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. )

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.

MOLECULIN BIOTECH, INC.

Exhibit 10.1 MOLECULIN BIOTECH, INC. December 21, 2025 Holder of Common Stock Purchase Warrants Re: Offer to Amend Common Stock Purchase Warrants Dear Holder: Moleculin Biotech, Inc. (the “Company”) is pleased to offer to you the opportunity to amend the Series E warrants (the “Series E Warrants”) to purchase shares of the Company’s common stock, par value $0.001 per share (the “Common Stock”) and

AMENDED AND RESTATED SERIES E COMMON STOCK PURCHASE WARRANT MOLECULIN BIOTECH, INC.

Exhibit 4.1 AMENDED AND RESTATED SERIES E COMMON STOCK PURCHASE WARRANT MOLECULIN BIOTECH, INC. Warrant Shares: [] New Issue Date: December , 2025 Original Issue Date: June 23, 2025 THIS AMENDED AND RESTATED SERIES E COMMON STOCK PURCHASE WARRANT (the “Warrant”) certifies that, for value received, [] or its assigns (the “Holder”) is entitled, upon the terms and subject to the limitations on exerci

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. )

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.

Moleculin Announces Positive Results from Phase 1 Clinical Trial Evaluating WP1066 for the Treatment of Pediatric Recurrent Malignant Brain Tumors Emory University physician-sponsored clinical trial conducted at the Aflac Cancer and Blood Disorders C

Exhibit 99.1 Moleculin Announces Positive Results from Phase 1 Clinical Trial Evaluating WP1066 for the Treatment of Pediatric Recurrent Malignant Brain Tumors Emory University physician-sponsored clinical trial conducted at the Aflac Cancer and Blood Disorders Center at Children’s Healthcare of Atlanta Results demonstrated WP1066 induces anti-tumor immune responses and were recently published in

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): December 17, 2025 MOLECULIN BIOTE

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): December 17, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organiz

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): December 15, 2025 MOLECULIN BIOTE

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): December 15, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organiz

MOLECULIN BIOTECH, INC.

Exhibit 10.1 MOLECULIN BIOTECH, INC. December 9, 2025 Holder of Common Stock Purchase Warrants Re: Inducement Offer to Exercise Common Stock Purchase Warrants Dear Holder: Moleculin Biotech, Inc. (the “Company”) is pleased to offer to you (“Holder”, “you” or similar terminology) the opportunity to receive new warrants to purchase shares of the Company’s common stock, par value $0.001 per share (th

SERIES G COMMON STOCK PURCHASE WARRANT MOLECULIN BIOTECH, INC.

Exhibit 4.1 NEITHER THIS SECURITY NOR THE SECURITIES FOR WHICH THIS SECURITY IS EXERCISABLE HAVE BEEN REGISTERED WITH THE SECURITIES AND EXCHANGE COMMISSION OR THE SECURITIES COMMISSION OF ANY STATE IN RELIANCE UPON AN EXEMPTION FROM REGISTRATION UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE “SECURITIES ACT”), AND, ACCORDINGLY, MAY NOT BE OFFERED OR SOLD EXCEPT PURSUANT TO AN EFFECTIVE REGISTR

MOLECULIN BIOTECH, INC.

Exhibit 10.2 MOLECULIN BIOTECH, INC. December 9, 2025 Holder of Common Stock Purchase Warrants Re: Inducement Offer to Exercise Common Stock Purchase Warrants Dear Holder: Moleculin Biotech, Inc. (the “Company”) is pleased to offer to you (“Holder”, “you” or similar terminology) the opportunity to receive new warrants to purchase shares of the Company’s common stock, par value $0.001 per share (th

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): December 9, 2025 MOLECULIN BIOTEC

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): December 9, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organiza

Moleculin Announces Completion of Treatment for the 45 Patients in Pivotal “MIRACLE” Phase 3 AML Trial on Pace for Q1 2026 Continues to drive enrollment with increase to 78% now consented Blinded response activity tracking within expected range Conse

Exhibit 99.1 Moleculin Announces Completion of Treatment for the 45 Patients in Pivotal “MIRACLE” Phase 3 AML Trial on Pace for Q1 2026 Continues to drive enrollment with increase to 78% now consented Blinded response activity tracking within expected range Consented subjects now across seven countries supporting the expansion of the MIRACLE trial HOUSTON, December 9, 2025 — Moleculin Biotech, Inc

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): December 9, 2025 MOLECULIN BIOTEC

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): December 9, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organiza

Moleculin Announces New Annamycin Collaboration in Brain Tumors Investigator-Initiated Preclinical studies at CIC biomaGUNE aimed at combatting Glioblastoma Multiforme Research will evaluate effects of intra-arterial delivery of Annamycin

Exhibit 99.1 Moleculin Announces New Annamycin Collaboration in Brain Tumors Investigator-Initiated Preclinical studies at CIC biomaGUNE aimed at combatting Glioblastoma Multiforme Research will evaluate effects of intra-arterial delivery of Annamycin HOUSTON, December 8, 2025 — Moleculin Biotech, Inc., (Nasdaq: MBRX) (“Moleculin” or the “Company”), a late-stage pharmaceutical company with a broad

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): December 8, 2025 MOLECULIN BIOTEC

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): December 8, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organiza

CERTIFICATE OF AMENDMENT TO THE AMENDED AND RESTATED CERTIFICATE OF INCORPORATION OF MOLECULIN BIOTECH, INC.

Exhibit 3.1 CERTIFICATE OF AMENDMENT TO THE AMENDED AND RESTATED CERTIFICATE OF INCORPORATION OF MOLECULIN BIOTECH, INC. Moleculin Biotech, Inc., a corporation organized and existing under the laws of the State of Delaware (the “Corporation”) for the purpose of amending its Amended and Restated Certificate of Incorporation in accordance with the General Corporation Law of the State of Delaware, do

Announces Reverse Stock Split

Exhibit 99.1 Announces Reverse Stock Split HOUSTON, November 26, 2025 — Moleculin Biotech, Inc., (Nasdaq: MBRX) (“Moleculin” or the “Company”), today announced that it filed an amendment to its amended and restated certificate of incorporation with the Secretary of State of the State of Delaware to effect a 1-for-25 reverse stock split of its common stock. The reverse stock split will take effect at 1

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): November 26, 2025 MOLECULIN BIOTE

-12-31 UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): November 26, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): November 24, 2025 MOLECULIN BIOTE

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): November 24, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organiz

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): November 20, 2025 MOLECULIN BIOTE

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): November 20, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organiz

November 13, 2025

Exhibit 18.1 November 13, 2025 Board of Directors Moleculin Biotech, Inc. 5300 Memorial Drive, Suite 950 Houston, TX 77007 Dear Directors: We are providing this letter solely for inclusion as an exhibit to Moleculin Biotech, Inc. and subsidiaries (the “Company") Form 10-Q filing pursuant to Item 601 of Regulation S-K. As stated in Note 2 to the unaudited condensed consolidated financial statements

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): November 13, 2025 MOLECULIN BIOTE

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): November 13, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organiz

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2025 ☐ TRANSITION REPORT PURSUANT

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2025 or ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number: 001-3775

Moleculin Reports 60% of First 45 Subjects in Pivotal “MIRACLE” Phase 3 AML Trial Consented Completion of treatment for the first 45 patients on pace for Q1 2026 with initial unblinded data thereafter; blinded response activity tracking within expect

Exhibit 99.1 CONFIDENTIAL DRAFT NOT FOR IMMEDIATE RELEASE Moleculin Reports 60% of First 45 Subjects in Pivotal “MIRACLE” Phase 3 AML Trial Consented Completion of treatment for the first 45 patients on pace for Q1 2026 with initial unblinded data thereafter; blinded response activity tracking within expected range HOUSTON, November 13, 2025 — Moleculin Biotech, Inc., (Nasdaq: MBRX) (“Moleculin” o

Moleculin Announces Grant Funded Research Evaluating Annamycin for the Treatment of Pancreatic Cancer at UNC-Chapel Hill Preclinical research to be conducted at the University of North Carolina at Chapel Hill (UNC) Annamycin will be used in conjuncti

Exhibit 99.1 Moleculin Announces Grant Funded Research Evaluating Annamycin for the Treatment of Pancreatic Cancer at UNC-Chapel Hill Preclinical research to be conducted at the University of North Carolina at Chapel Hill (UNC) Annamycin will be used in conjunction with novel agents and modalities Preclinical studies indicate Annamycin targets key factors in pancreatic cancer HOUSTON, November 12,

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): November 12, 2025 MOLECULIN BIOTE

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): November 12, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organiz

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): October 30, 2025 MOLECULIN BIOTEC

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): October 30, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of (Commission File No.) (I.

EXHIBIT 99.1

Exhibit 99.1

Moleculin Expands Global IP Portfolio with New Australian Patent for Annamycin

Exhibit 99.1 Moleculin Expands Global IP Portfolio with New Australian Patent for Annamycin HOUSTON, October 29, 2025 — Moleculin Biotech, Inc., (Nasdaq: MBRX) (“Moleculin” or the “Company”), a late-stage pharmaceutical company with a broad portfolio of drug candidates targeting hard-to-treat cancers and viral infections, today announced that the Australian Patent Office (IP Australia) has granted

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): October 29, 2025 MOLECULIN BIOTEC

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): October 29, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organiza

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): October 23, 2025 MOLECULIN BIOTEC

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): October 23, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organiza

Moleculin Announces New Investigator-Initiated Study of Annamycin for Treating Pancreatic Cancer Atlantic Health, a leading provider of health care based in New Jersey, to conduct the investigator-initiated Phase 1B/2 study Preclinical studies indica

Exhibit 99.1 Moleculin Announces New Investigator-Initiated Study of Annamycin for Treating Pancreatic Cancer Atlantic Health, a leading provider of health care based in New Jersey, to conduct the investigator-initiated Phase 1B/2 study Preclinical studies indicate Annamycin targets key factors in pancreatic cancer HOUSTON, October 23, 2025 — Moleculin Biotech, Inc., (Nasdaq: MBRX) (“Moleculin” or

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): October 16, 2025 MOLECULIN BIOTEC

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): October 16, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organiza

MOLECULIN BIOTECH, INC. Up to 64,864,864 Shares of Common Stock

Table of Contents Filed Pursuant to Rule 424(b)(3) Registration No. 333-290418 MOLECULIN BIOTECH, INC. Up to 64,864,864 Shares of Common Stock This prospectus relates to the resale, from time to time, by the selling stockholders (the “Selling Stockholders”) identified in this prospectus under the caption “Selling Stockholders,” of up to 64,864,864 shares of our common stock upon the exercise of ce

EFFECT

X0101 EFFECT 33 LIVE 2025-09-30 16:30:00 S-3 0001659617 Moleculin Biotech, Inc. 333-290418

Moleculin Biotech, Inc. 5300 Memorial Drive, Suite 950 Houston, TX 77007 September 29, 2025

Moleculin Biotech, Inc. 5300 Memorial Drive, Suite 950 Houston, TX 77007 September 29, 2025 VIA EDGAR U.S. Securities and Exchange Commission Division of Corporate Finance Washington, DC 20549 Attention: Jessica Dickerson Re: Moleculin Biotech, Inc. Registration Statement on Form S-3 Registration No. 333-290418 Ladies and Gentlemen: Pursuant to Rule 461 of the Securities Act of 1933, as amended, M

Moleculin Announces Notice of Allowance for Canadian Patent Covering Annamycin

Exhibit 99.1 Moleculin Announces Notice of Allowance for Canadian Patent Covering Annamycin HOUSTON, September 25, 2025 — Moleculin Biotech, Inc., (Nasdaq: MBRX) (“Moleculin” or the “Company”), a late-stage pharmaceutical company with a broad portfolio of drug candidates targeting hard-to-treat cancers and viral infections, today announced that the Canadian Intellectual Property Office (CIPO) has

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): September 25, 2025 MOLECULIN BIOT

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): September 25, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organi

LETTER

September 24, 2025 Walter Klemp Chief Executive Officer Moleculin Biotech, Inc. 5300 Memorial Drive, Suite 950 Houston, TX 77007 Re: Moleculin Biotech, Inc. Registration Statement on Form S-3 Filed September 19, 2025 File No. 333-290418 Dear Walter Klemp: This is to advise you that we have not reviewed and will not review your registration statement. Please refer to Rules 460 and 461 regarding req

Security Type

Calculation of Filing Fee Tables S-3 Moleculin Biotech, Inc. Table 1: Newly Registered and Carry Forward Securities ☐Not Applicable Security Type Security Class Title Fee Calculation or Carry Forward Rule Amount Registered Proposed Maximum Offering Price Per Unit Maximum Aggregate Offering Price Fee Rate Amount of Registration Fee Carry Forward Form Type Carry Forward File Number Carry Forward Ini

As filed with the Securities and Exchange Commission on September 19, 2025

Table of Contents As filed with the Securities and Exchange Commission on September 19, 2025 Registration No.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. )

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.

Table 1: Newly Registered Securities

Calculation of Filing Fee Tables S-8 Moleculin Biotech, Inc. Table 1: Newly Registered Securities Security Type Security Class Title Fee Calculation Rule Amount Registered Proposed Maximum Offering Price Per Unit Maximum Aggregate Offering Price Fee Rate Amount of Registration Fee 1 Equity Common Stock, $0.001 par value Other 6,000,000 $ 0.37 $ 2,220,000.00 0.0001531 $ 339.88 Total Offering Amount

Moleculin Biotech, Inc. 2024 Stock Plan Incentive Stock Option Agreement

Exhibit 99.2 THIS DOCUMENT CONSTITUTES PART OF THE SECTION 10(a) PROSPECTUS COVERING SECURITIES THAT HAVE BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933. Moleculin Biotech, Inc. 2024 Stock Plan Incentive Stock Option Agreement The employee identified below has been selected to be a Participant in the Moleculin Biotech, Inc. 2024 Stock Plan(the “2024 Plan”) and has been granted an Incentive Stock

As filed with the Securities and Exchange Commission on September 10, 2025

As filed with the Securities and Exchange Commission on September 10, 2025 Registration No.

MOLECULIN BIOTECH, INC. 2024 STOCK PLAN (Amended and Restated)

Exhibit 99.1 MOLECULIN BIOTECH, INC. 2024 STOCK PLAN (Amended and Restated) Section 1. Establishment and Purpose. 1.1 The Board of Directors of Moleculin Biotech, Inc. (the “Company”) established the Moleculin Biotech, Inc. 2024 Stock Plan (the “Plan”), effective as of October 24, 2024. The Plan was amended effective as of August 18, 2025, subject to approval by the Company’s stockholders at the C

Moleculin Accelerates Recruitment in Phase 3 Acute Myeloid Leukemia “MIRACLE” Clinical Trial European expansion in September across Georgia, Italy, Lithuania, Poland, Romania, Spain, and US 13 subjects recruited (treated, enrolled, or screened) Forec

Exhibit 99.1 Moleculin Accelerates Recruitment in Phase 3 Acute Myeloid Leukemia “MIRACLE” Clinical Trial European expansion in September across Georgia, Italy, Lithuania, Poland, Romania, Spain, and US 13 subjects recruited (treated, enrolled, or screened) Forecasts total recruitment of 20 or more subjects by end of September On track to recruit to 45 patients in Q4 25 for initial data unblinding

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): September 9, 2025 MOLECULIN BIOTE

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): September 9, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organiz

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): September 8, 2025 MOLECULIN BIOTE

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): September 8, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organiz

Moleculin Doses First EU Patient in Phase 3 Pivotal MIRACLE Trial for Treatment of Acute Myeloid Leukemia Spain site opens with two R/R AML subjects enrolled; One treated On track to recruit 45 subjects in 4Q25 for initial data unblinding

Exhibit 99.1 Moleculin Doses First EU Patient in Phase 3 Pivotal MIRACLE Trial for Treatment of Acute Myeloid Leukemia Spain site opens with two R/R AML subjects enrolled; One treated On track to recruit 45 subjects in 4Q25 for initial data unblinding HOUSTON, September 8, 2025 — Moleculin Biotech, Inc., (Nasdaq: MBRX) (“Moleculin” or the “Company”), a late-stage pharmaceutical company with a broa

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): September 8, 2025 MOLECULIN BIOTE

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): September 8, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organiz

EXHIBIT 99.1

Exhibit 99.1

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. )

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): August 28, 2025 MOLECULIN BIOTECH

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): August 28, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organizat

SERIES F COMMON STOCK PURCHASE WARRANT MOLECULIN BIOTECH, INC.

Exhibit 4.1 NEITHER THIS SECURITY NOR THE SECURITIES FOR WHICH THIS SECURITY IS EXERCISABLE HAVE BEEN REGISTERED WITH THE SECURITIES AND EXCHANGE COMMISSION OR THE SECURITIES COMMISSION OF ANY STATE IN RELIANCE UPON AN EXEMPTION FROM REGISTRATION UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE “SECURITIES ACT”), AND, ACCORDINGLY, MAY NOT BE OFFERED OR SOLD EXCEPT PURSUANT TO AN EFFECTIVE REGISTR

Moleculin Announces Exercise of Warrants for $6.0 Million Gross Proceeds

Exhibit 99.1 Moleculin Announces Exercise of Warrants for $6.0 Million Gross Proceeds HOUSTON, August 28, 2025 /PRNewswire/ - Moleculin Biotech, Inc., (Nasdaq: MBRX) (“Moleculin” or the “Company”), a late-stage pharmaceutical company with a broad portfolio of drug candidates targeting hard-to-treat tumors and viruses, today announced it has entered into agreements with certain holders of its exist

MOLECULIN BIOTECH, INC.

Exhibit 10.1 MOLECULIN BIOTECH, INC. August 27, 2025 Holder of Common Stock Purchase Warrants Re: Inducement Offer to Exercise Common Stock Purchase Warrants Dear Holder: Moleculin Biotech, Inc. (the “Company”) is pleased to offer to you (“Holder”, “you” or similar terminology) the opportunity to receive new warrants to purchase shares of the Company’s common stock, par value $0.001 per share (the

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): August 21, 2025 MOLECULIN BIOTECH

-12-31 UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): August 21, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Or

Moleculin Issues New Positive AML Overall Survival Data: Median Overall Survival (OS) of 15 months for subjects with complete remission (n=8) Median OS of 2nd Line efficacy evaluable population of 12 months (n=9) Median OS of Intent to Treat populati

Exhibit 99.1 Moleculin Issues New Positive AML Overall Survival Data: Median Overall Survival (OS) of 15 months for subjects with complete remission (n=8) Median OS of 2nd Line efficacy evaluable population of 12 months (n=9) Median OS of Intent to Treat population (1L-7L) of 9 months (n=22) OS demonstrated by Annamycin in the MB-106 trial is significantly above industry expectations for relapsed

State of Delaware Secretary of State Division of Corporations Delivered 02:10 PM 08/21/2025 FILED 02:10 PM 08/21/2025 SR 20253747621 - FileNumber 5793265

Exhibit 3.1 State of Delaware Secretary of State Division of Corporations Delivered 02:10 PM 08/21/2025 FILED 02:10 PM 08/21/2025 SR 20253747621 - FileNumber 5793265 CERTIFICATE OF AMENDMENT TO THE AMENDED AND RESTATED CERTIFICATE OF INCORPORATION OF MOLECULIN BIOTECH, INC. Moleculin Biotech, Inc., a corporation organized and existing under the laws of the State of Delaware (the "Corporation") for

EXHIBIT 99.1

Exhibit 99.1

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): August 18, 2025 MOLECULIN BIOTECH

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): August 18, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organizat

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): August 18, 2025 MOLECULIN BIOTECH

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): August 18, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organizat

Moleculin Reports Second Quarter 2025 Financial Results and Highlights - Continues recruitment and opens US and EU sites for the Phase 2B/3 MIRACLE trial - 20+ additional clinical sites in Europe and the US expected to begin recruitment by the end of

Exhibit 99.1 Moleculin Reports Second Quarter 2025 Financial Results and Highlights - Continues recruitment and opens US and EU sites for the Phase 2B/3 MIRACLE trial - 20+ additional clinical sites in Europe and the US expected to begin recruitment by the end of Q3 - Anticipated data readout of MIRACLE Part A targeted before end of 2025 HOUSTON, August 13, 2025 - Moleculin Biotech, Inc., (Nasdaq:

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): August 13, 2025 MOLECULIN BIOTECH

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): August 13, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organizat

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2025 ☐ TRANSITION REPORT PURSUANT TO S

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2025 or ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number: 001-37758 MOL

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): August 6, 2025 MOLECULIN BIOTECH,

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): August 6, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organizati

Liposomal Annamycin (L-ANN) Efficacy against primary and Metastatic Liver Cancers poster

Exhibit 99.2

Moleculin Biotech, Inc. Unveils Promising Preclinical Data of Annamycin in Liver Cancer Treatment Presented data highlights the potential of Annamycin for treating broad range of human cancers, including high-need oncology indications Annamycin curre

Exhibit 99.1 Moleculin Biotech, Inc. Unveils Promising Preclinical Data of Annamycin in Liver Cancer Treatment Presented data highlights the potential of Annamycin for treating broad range of human cancers, including high-need oncology indications Annamycin currently in late-stage clinical development in combination with cytarabine for the treatment of AML; Anticipated preliminary data readout in

Investor Presentation dated July 2025

Exhibit 99.1

Regulation FD Disclosure, Financial Statements and Exhibits

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): August 1, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organizati

Moleculin Receives Notice of Intent to Grant New European Patent for Annamycin – New patent enhances market position in Europe

Exhibit 99.1 Moleculin Receives Notice of Intent to Grant New European Patent for Annamycin – New patent enhances market position in Europe HOUSTON, July 30, 2025 /PRNewswire/ - Moleculin Biotech, Inc., (Nasdaq: MBRX) (“Moleculin” or the “Company”), a late-stage pharmaceutical company with a broad portfolio of drug candidates targeting hard-to-treat tumors and viruses, today announced it has recei

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): July 30, 2025 MOLECULIN BIOTECH,

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): July 30, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organizatio

Moleculin Engages Industry Veteran Adriano Treve to Explore Accelerated Strategic Partnerships 40+ year career at Roche founded on dedication to bringing new innovative medicines to patients and making them accessible

Exhibit 99.1 Moleculin Engages Industry Veteran Adriano Treve to Explore Accelerated Strategic Partnerships 40+ year career at Roche founded on dedication to bringing new innovative medicines to patients and making them accessible HOUSTON, July 17, 2025 — Moleculin Biotech, Inc., (Nasdaq: MBRX) (“Moleculin” or the “Company”), a late-stage pharmaceutical company with a broad portfolio of drug candi

Regulation FD Disclosure, Financial Statements and Exhibits

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): July 17, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organizatio

Entry into a Material Definitive Agreement, Financial Statements and Exhibits

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): July 11, 2025 MOLECULIN BIOTECH, INC. (Exact name of registrant as specified in its charter) Delaware 001-37758 47-4671997 (State or other jurisdiction of incorporation) (Commission F

Moleculin Biotech, Inc. Up to $6,500,000 Common Stock

Table of Contents Filed Pursuant to Rule 424(b)(5) Registration No. 333-280064 Prospectus Supplement (to Prospectus dated July 1, 2024) Moleculin Biotech, Inc. Up to $6,500,000 Common Stock On July 11, 2025, we entered into a certain At The Market Offering Agreement (“ATM Agreement”) with Roth Capital Partners, LLC as sales agent (“Roth”) relating to the sale of shares of our common stock, par val

At The Market Offering Agreement, dated July 11, 2025, by and between Moleculin Biotech, Inc. and Roth Capital Partners, LLC.

Exhibit 1.1 AT THE MARKET OFFERING AGREEMENT July 11, 2025 Roth Capital Partners, LLC 888 San Clemente Drive, Suite 400 Newport Beach, CA 92660 Ladies and Gentlemen: Moleculin Biotech, Inc., a corporation organized under the laws of Delaware (the “Company”), confirms its agreement (this “Agreement”) with Roth Capital Partners, LLC (the “Manager”) as follows: 1. Definitions. The terms that follow,

Moleculin Expands Phase 3 MIRACLE Clinical Trial into the Country of Georgia, Enrollment Update and Future Plans Secured approval from the Regulation Agency for Medical and Pharmaceutical Activities (RAMPA) in Georgia for Phase 2B/3 MIRACLE trial Rec

Exhibit 99.1 Moleculin Expands Phase 3 MIRACLE Clinical Trial into the Country of Georgia, Enrollment Update and Future Plans Secured approval from the Regulation Agency for Medical and Pharmaceutical Activities (RAMPA) in Georgia for Phase 2B/3 MIRACLE trial Recent EU approval from the European Medicines Agency (EMA) boosts trial profile Enrollment in Part A of MIRACLE reaches seven subjects trea

Regulation FD Disclosure, Financial Statements and Exhibits

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): July 9, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organization

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. )

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ) Filed by the Registrant ☒ Filed by a Party other than the Registrant ☐ Check the appropriate box: ☐ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) ☒ Defin

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. )

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ) Filed by the Registrant ☒ Filed by a Party other than the Registrant ☐ Check the appropriate box: ☐ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) ☐ Defin

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. )

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ) Filed by the Registrant ☒ Filed by a Party other than the Registrant ☐ Check the appropriate box: ☒ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) ☐ Defin

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): June 27, 2025 MOLECULIN BIOTECH,

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): June 27, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organizatio

Form of Securities Purchase Agreement

Exhibit 10.1 SECURITIES PURCHASE AGREEMENT This Securities Purchase Agreement (this “Agreement”) is dated as of June 20, 2025, between Moleculin Biotech, Inc., a Delaware corporation (the “Company”), and each purchaser identified on the signature pages hereto (each, including its successors and assigns, a “Purchaser” and collectively the “Purchasers”). WHEREAS, subject to the terms and conditions

Form of Series E Warrant

Exhibit 4.1 SERIES E COMMON STOCK PURCHASE WARRANT MOLECULIN BIOTECH, INC. Warrant Shares: [] Issue Date: June 23, 2025 THIS SERIES E COMMON STOCK PURCHASE WARRANT (the “Warrant”) certifies that, for value received, [] or its assigns (the “Holder”) is entitled, upon the terms and subject to the limitations on exercise and the conditions hereinafter set forth, at any time on or after the Stockholde

Moleculin Announces $5.9 Million Public Offering

Exhibit 99.1 Moleculin Announces $5.9 Million Public Offering HOUSTON, June 20, 2025 (GLOBE NEWSWIRE) - Moleculin Biotech, Inc., (Nasdaq: MBRX) (“Moleculin” or the “Company”), a late-stage pharmaceutical company with a broad portfolio of drug candidates targeting hard-to-treat tumors and viruses, today announced the pricing of a public offering consisting of 16,080,000 shares of common stock (or p

Placement Agency Agreement between Moleculin Biotech, Inc. and Roth Capital Partners, LLC

Exhibit 1.1 PLACEMENT AGENCY AGREEMENT June 20, 2025 Roth Capital Partners, LLC 888 San Clemente Drive, Suite 400 Newport Beach, CA 92660 Ladies and Gentlemen: Introduction. Subject to the terms and conditions herein (this “Agreement”), Moleculin Biotech, Inc., a Delaware corporation (the “Company”), hereby agrees to sell up to an aggregate of $5,950,000.00 of registered securities of the Company,

Regulation FD Disclosure, Entry into a Material Definitive Agreement, Financial Statements and Exhibits

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): June 20, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organizatio

Moleculin Biotech, Inc. 9,972,026 Shares of Common Stock and 29,916,078 Accompanying Series E Warrants to Purchase up to 29,916,078 Shares of Common Stock 6,107,974 Pre-Funded Warrants to Purchase up to 6,107,974 Shares of Common Stock and 18,323,922

Table of Contents Filed Pursuant to Rule 424(b)(4) Registration No. 333-287727 Moleculin Biotech, Inc. 9,972,026 Shares of Common Stock and 29,916,078 Accompanying Series E Warrants to Purchase up to 29,916,078 Shares of Common Stock 6,107,974 Pre-Funded Warrants to Purchase up to 6,107,974 Shares of Common Stock and 18,323,922 Accompanying Series E Warrants to Purchase up to 18,323,922 Shares of

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): June 18, 2025 MOLECULIN BIOTECH,

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): June 18, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organizatio

Moleculin Receives Positive FDA Feedback on Pediatric Study Plan for Annamycin in Children with R/R AML Annamycin aims to eliminate cardiotoxicity associated with anthracyclines used to treat about 60% of all children with cancer FDA recommends inclu

Exhibit 99.1 Moleculin Receives Positive FDA Feedback on Pediatric Study Plan for Annamycin in Children with R/R AML Annamycin aims to eliminate cardiotoxicity associated with anthracyclines used to treat about 60% of all children with cancer FDA recommends inclusion of patients as young as 6 months – younger than Moleculin had proposed – to be allowed in the pediatric clinical study Enrollment an

Moleculin Biotech, Inc. 5300 Memorial Drive, Suite 950 Houston, TX 77007

Moleculin Biotech, Inc. 5300 Memorial Drive, Suite 950 Houston, TX 77007 June 17, 2025 VIA EDGAR U.S. Securities and Exchange Commission Division of Corporate Finance Washington, DC 20549 Attention: Daniel Crawford Re: Moleculin Biotech, Inc. Registration Statement on Form S-1 Registration No. 333-287727 Ladies and Gentlemen: Pursuant to Rule 461 of the Securities Act of 1933, as amended, Moleculi

Roth Capital Partners, LLC 888 San Clemente Drive Newport Beach, CA 92660

Roth Capital Partners, LLC 888 San Clemente Drive Newport Beach, CA 92660 June 17, 2025 VIA EDGAR U.

As filed with the U.S. Securities and Exchange Commission on June 16, 2025.

Table of Contents As filed with the U.S. Securities and Exchange Commission on June 16, 2025. Registration No. 333-287727 UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 AMENDMENT NO. 3 TO FORM S-1 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 Moleculin Biotech, Inc. (Exact name of registrant as specified in its charter) Delaware 2834 47-4671997 (State or other ju

June 16, 2025

June 16, 2025 VIA EDGAR United States Securities and Exchange Commission Division of Corporation Finance Office of Industrial Applications and Services 100 F Street, NE Washington, DC 20549 Attention: Daniel Crawford Re: Moleculin Biotech, Inc.

LETTER

June 13, 2025 Walter V. Klemp President, Chief Executive Officer and Chairman Moleculin Biotech, Inc. 5300 Memorial Drive, Suite 950 Houston, TX 77007 Re: Moleculin Biotech, Inc. Amendment No. 2 to Registration Statement on Form S-1 Filed June 11, 2025 File No. 333-287727 Dear Walter V. Klemp: We have reviewed your amended registration statement and have the following comments. Please respond to t

Form of Series E Warrant

Exhibit 4.12 SERIES E COMMON STOCK PURCHASE WARRANT MOLECULIN BIOTECH, INC. Warrant Shares: [] Issue Date: [], 2025 THIS SERIES E COMMON STOCK PURCHASE WARRANT (the “Warrant”) certifies that, for value received, [] or its assigns (the “Holder”) is entitled, upon the terms and subject to the limitations on exercise and the conditions hereinafter set forth, at any time on or after the Stockholder Ap

June 11, 2025

June 11, 2025 VIA EDGAR United States Securities and Exchange Commission Division of Corporation Finance Office of Industrial Applications and Services 100 F Street, NE Washington, DC 20549 Attention: Daniel Crawford Re: Moleculin Biotech, Inc.

As filed with the U.S. Securities and Exchange Commission on June 11, 2025.

Table of Contents As filed with the U.S. Securities and Exchange Commission on June 11, 2025. Registration No. 333-287727 UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 AMENDMENT NO. 2 TO FORM S-1 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 Moleculin Biotech, Inc. (Exact name of registrant as specified in its charter) Delaware 2834 47-4671997 (State or other ju

Form of Securities Purchase Agreement

Exhibit 10.35 SECURITIES PURCHASE AGREEMENT This Securities Purchase Agreement (this “Agreement”) is dated as of [], 2025, between Moleculin Biotech, Inc., a Delaware corporation (the “Company”), and each purchaser identified on the signature pages hereto (each, including its successors and assigns, a “Purchaser” and collectively the “Purchasers”). WHEREAS, subject to the terms and conditions set

LETTER

June 10, 2025 Walter V. Klemp President, Chief Executive Officer and Chairman Moleculin Biotech, Inc. 5300 Memorial Drive, Suite 950 Houston, TX 77007 Re: Moleculin Biotech, Inc. Amendment No. 1 to Registration Statement on Form S-1 Filed June 6, 2025 File No. 333-287727 Dear Walter V. Klemp: We have reviewed your amended registration statement and have the following comments. Please respond to th

Form of Securities Purchase Agreement

Exhibit 10.35 SECURITIES PURCHASE AGREEMENT This Securities Purchase Agreement (this “Agreement”) is dated as of [], 2025, between Moleculin Biotech, Inc., a Delaware corporation (the “Company”), and each purchaser identified on the signature pages hereto (each, including its successors and assigns, a “Purchaser” and collectively the “Purchasers”). WHEREAS, subject to the terms and conditions set

As filed with the U.S. Securities and Exchange Commission on June 6, 2025.

Table of Contents As filed with the U.S. Securities and Exchange Commission on June 6, 2025. Registration No. 333-287727 UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 AMENDMENT NO. 1 TO FORM S-1 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 Moleculin Biotech, Inc. (Exact name of registrant as specified in its charter) Delaware 2834 47-4671997 (State or other jur

Filing Fee Table

Exhibit 107 Calculation of Filing Fee Table Form S-1 (Form Type) Moleculin Biotech, Inc.

Form of Series E Warrant

Exhibit 4.12 SERIES E COMMON STOCK PURCHASE WARRANT MOLECULIN BIOTECH, INC. Warrant Shares: [] Issue Date: [], 2025 THIS SERIES E COMMON STOCK PURCHASE WARRANT (the “Warrant”) certifies that, for value received, [] or its assigns (the “Holder”) is entitled, upon the terms and subject to the limitations on exercise and the conditions hereinafter set forth, at any time on or after the Stockholder Ap

Virtual KOL Event Presentation dated June 5, 2025

Exhibit 99.1

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): June 5, 2025 MOLECULIN BIOTECH, I

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): June 5, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organization

Moleculin Reports Positive Topline Efficacy Results from U.S. Phase 1B/2 Clinical Trial Evaluating Annamycin for the Treatment of Soft Tissue Sarcoma Lung Metastases (MB-107) Annamycin delivering better performance 7th line than would be expected eve

Exhibit 99.1 Moleculin Reports Positive Topline Efficacy Results from U.S. Phase 1B/2 Clinical Trial Evaluating Annamycin for the Treatment of Soft Tissue Sarcoma Lung Metastases (MB-107) Annamycin delivering better performance 7th line than would be expected even in 2nd line for monotherapy Responders (Stable Disease or Partial Response) after 2 cycles of Annamycin showed improvement in OS and Pr

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): June 4, 2025 MOLECULIN BIOTECH, I

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): June 4, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organization

Moleculin Biotech, Inc. 5300 Memorial Drive, Suite 950 Houston, TX 77007 June 3, 2025

Moleculin Biotech, Inc. 5300 Memorial Drive, Suite 950 Houston, TX 77007 June 3, 2025 VIA EDGAR U.S. Securities and Exchange Commission Division of Corporate Finance Washington, DC 20549 Attention: Daniel Crawford Re: Moleculin Biotech, Inc. Registration Statement on Form S-1 Registration No. 333-287727 Ladies and Gentlemen: Pursuant to Rule 461 of the Securities Act of 1933, as amended, Moleculin

Roth Capital Partners, LLC 888 San Clemente Drive Newport Beach, CA 92660

Roth Capital Partners, LLC 888 San Clemente Drive Newport Beach, CA 92660 June 3, 2025 VIA EDGAR U.

Form of Securities Purchase Agreement

Exhibit 10.35 SECURITIES PURCHASE AGREEMENT This Securities Purchase Agreement (this “Agreement”) is dated as of [], 2025, between Moleculin Biotech, Inc., a Delaware corporation (the “Company”), and each purchaser identified on the signature pages hereto (each, including its successors and assigns, a “Purchaser” and collectively the “Purchasers”). WHEREAS, subject to the terms and conditions set

Filing Fee Table

Exhibit 107 Calculation of Filing Fee Table Form S-1 (Form Type) Moleculin Biotech, Inc.

As filed with the U.S. Securities and Exchange Commission on June 2, 2025.

Table of Contents As filed with the U.S. Securities and Exchange Commission on June 2, 2025. Registration No. 333- UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM S-1 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 Moleculin Biotech, Inc. (Exact name of registrant as specified in its charter) Delaware 2834 47-4671997 (State or other jurisdiction of (Primary Sta

Form of Series E Warrant

Exhibit 4.12 SERIES E COMMON STOCK PURCHASE WARRANT MOLECULIN BIOTECH, INC. Warrant Shares: [] Issue Date: [], 2025 THIS SERIES E COMMON STOCK PURCHASE WARRANT (the “Warrant”) certifies that, for value received, [] or its assigns (the “Holder”) is entitled, upon the terms and subject to the limitations on exercise and the conditions hereinafter set forth, at any time on or after the [Stockholder A

Placement Agency Agreement (incorporated by reference to exhibit 1.1 of the Form S-1 filed June 02, 2025)

Exhibit 1.1 PLACEMENT AGENCY AGREEMENT [], 2025 Roth Capital Partners, LLC 888 San Clemente Drive, Suite 400 Newport Beach, CA 92660 Ladies and Gentlemen: Introduction. Subject to the terms and conditions herein (this “Agreement”), Moleculin Biotech, Inc., a Delaware corporation (the “Company”), hereby agrees to sell up to an aggregate of $[] of registered securities of the Company, including, but

Form of Pre-Funded Warrant (incorporated by reference to exhibit 4.13 of the Form S-1 filed June 02, 2025)

Exhibit 4.13 PREFUNDED COMMON STOCK PURCHASE WARRANT MOLECULIN BIOTECH, INC. Warrant Shares: [] Initial Exercise Date: [], 2025 THIS PRE-FUNDED COMMON STOCK PURCHASE WARRANT (the “Warrant”) certifies that, for value received, [] or its assigns (the “Holder”) is entitled, upon the terms and subject to the limitations on exercise and the conditions hereinafter set forth, at any time on or after the

Notice of Delisting or Failure to Satisfy a Continued Listing Rule or Standard; Transfer of Listing

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): May 23, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organization

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM S-1 REGISTRATION STATEMENT THE SECURITIES ACT OF 1933 Moleculin Biotech, Inc. (Exact name of registrant as specified in its charter)

Table of Contents As confidentially submitted to the U.S. Securities and Exchange Commission on May 23, 2025. This draft registration statement has not been filed publicly with the U.S. Securities and Exchange Commission and all information contained herein remains strictly confidential. Registration No. 333- UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM S-1 REGISTRA

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. )

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): May 14, 2025 MOLECULIN BIOTECH, I

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): May 14, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organization

Moleculin Reports First Quarter 2025 Financial Results and Provides Corporate Update Enrollment and dosing underway in Phase 3 clinical trial (the “MIRACLE” trial) evaluating Annamycin (naxtarubicin) for the treatment of R/R AML Regulatory and site s

Exhibit 99.1 Moleculin Reports First Quarter 2025 Financial Results and Provides Corporate Update Enrollment and dosing underway in Phase 3 clinical trial (the “MIRACLE” trial) evaluating Annamycin (naxtarubicin) for the treatment of R/R AML Regulatory and site selection progress to date supports interim data readout expected in the second half of 2025 Recently received European Medicines Agency (

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2025 ☐ TRANSITION REPORT PURSUANT TO

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2025 or ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number: 001-37758 MO

Regulation FD Disclosure, Financial Statements and Exhibits

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): May 12, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organization

Moleculin Receives European Medicines Agency Approval to Expand Phase 3 MIRACLE Clinical Trial Adds nine additional countries to the Company’s ongoing pivotal Phase 3 trial; Authorization granted in all EU countries requested Enrollment and dosing un

Exhibit 99.1 Moleculin Receives European Medicines Agency Approval to Expand Phase 3 MIRACLE Clinical Trial Adds nine additional countries to the Company’s ongoing pivotal Phase 3 trial; Authorization granted in all EU countries requested Enrollment and dosing underway in Phase 3 clinical trial (the “MIRACLE” trial) evaluating Annamycin for the treatment of R/R AML; Interim data readout expected i

Submission of Matters to a Vote of Security Holders

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): May 9, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organization)

Moleculin to Report First Quarter 2025 Financial Results on May 13, 2025 and Host Conference Call and Webcast

Exhibit 99.1 Moleculin to Report First Quarter 2025 Financial Results on May 13, 2025 and Host Conference Call and Webcast HOUSTON, May 7, 2025 - Moleculin Biotech, Inc., (Nasdaq: MBRX) (“Moleculin” or the “Company”), a late-stage pharmaceutical company with a broad portfolio of drug candidates targeting hard-to-treat cancers and viruses, today announced that it will report its financial results f

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): May 7, 2025 MOLECULIN BIOTECH, IN

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): May 7, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organization)

Moleculin Announces World Health Organization Approval of “naxtarubicin” as International Non-Proprietary Name for Annamycin Annamycin has the potential to be safer and more effective than current prescribed anthracyclines to treat serious, hard-to-t

Exhibit 99.1 Moleculin Announces World Health Organization Approval of “naxtarubicin” as International Non-Proprietary Name for Annamycin Annamycin has the potential to be safer and more effective than current prescribed anthracyclines to treat serious, hard-to-treat cancers Ongoing pivotal, adaptive Phase 3 clinical trial (the “MIRACLE” trial) evaluating Annamycin for the treatment of acute myelo

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): May 6, 2025 MOLECULIN BIOTECH, IN

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): May 6, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organization)

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): May 5, 2025 MOLECULIN BIOTECH, IN

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): May 5, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organization)

Moleculin Bolsters Annamycin Intellectual Property Portfolio with Granting of Two New U.S. Patents Company continues to expand global IP coverage and claims to major markets, now extending to June 2040

Exhibit 99.1 Moleculin Bolsters Annamycin Intellectual Property Portfolio with Granting of Two New U.S. Patents Company continues to expand global IP coverage and claims to major markets, now extending to June 2040 HOUSTON, May 5, 2025 — Moleculin Biotech, Inc., (Nasdaq: MBRX) (“Moleculin” or the “Company”), a late-stage pharmaceutical company with a broad portfolio of drug candidates targeting ha

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 10-K/A (Amendment No. 2) ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 December 31, 2024 ☐ TRANSITION REPORT PURSUANT TO SECTION 13

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 10-K/A (Amendment No. 2) ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 December 31, 2024 or ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF For the transition period from to Commission File Number: 001-37758 Moleculin Biotech,

Poster dated April 2025

Exhibit 99.2

Moleculin Announces New Pre-Clinical Data for Annamycin Demonstrating Market Expansion Potential Including Treatment for Pancreatic Cancer Data presented at the American Association for Cancer Research (AACR) Annual Meeting 2025 Annamycin is potentia

Exhibit 99.1 Moleculin Announces New Pre-Clinical Data for Annamycin Demonstrating Market Expansion Potential Including Treatment for Pancreatic Cancer Data presented at the American Association for Cancer Research (AACR) Annual Meeting 2025 Annamycin is potentially a highly versatile drug capable of working synergistically with numerous mechanistically different FDA approved anticancer first line

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): April 29, 2025 MOLECULIN BIOTECH,

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): April 29, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organizati

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): April 25, 2025 MOLECULIN BIOTECH,

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): April 25, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organizati

InvestorPresentation dated April 2025

Exhibit 99.1

Regulation FD Disclosure, Financial Statements and Exhibits

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): April 21, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organizati

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 10-K/A (Amendment No. 1) ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2024 ☐ TRANSITION REPO

-12-31FY2024 Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.

Regulation FD Disclosure, Financial Statements and Exhibits

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): April 17, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organizati

Moleculin Announces Acceptance of Abstract to be Presented at the American Association for Cancer Research (AACR) Annual Meeting 2025

Exhibit 99.1 Moleculin Announces Acceptance of Abstract to be Presented at the American Association for Cancer Research (AACR) Annual Meeting 2025 HOUSTON, April 17, 2025 — Moleculin Biotech, Inc., (Nasdaq: MBRX) (“Moleculin” or the “Company”), a late-stage pharmaceutical company with a broad portfolio of drug candidates targeting hard-to-treat cancers and viruses, today announced that an abstract

Other Events

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): April 9, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organizatio

LETTER

April 4, 2025 Walter Klemp Chief Executive Officer Moleculin Biotech, Inc. 5300 Memorial Drive, Suite 950 Houston, TX 77007 Re: Moleculin Biotech, Inc. Registration Statement on Form S-1 Filed March 31, 2025 File No. 333-286276 Dear Walter Klemp: This is to advise you that we have not reviewed and will not review your registration statement. Please refer to Rules 460 and 461 regarding requests for

Moleculin Biotech, Inc. 5300 Memorial Drive, Suite 950 Houston, TX 77007 April 4, 2025

Moleculin Biotech, Inc. 5300 Memorial Drive, Suite 950 Houston, TX 77007 April 4, 2025 VIA EDGAR U.S. Securities and Exchange Commission Division of Corporate Finance Washington, DC 20549 Attention: Alan Campbell Re: Moleculin Biotech, Inc. Registration Statement on Form S-1 Registration No. 333-286276 Ladies and Gentlemen: Pursuant to Rule 461 of the Securities Act of 1933, as amended, Moleculin

Moleculin Doses First Patient in Pivotal, Adaptive Phase 3 MIRACLE Trial – Initial data readout on track for second half of 2025

Exhibit 99.1 Moleculin Doses First Patient in Pivotal, Adaptive Phase 3 MIRACLE Trial – Initial data readout on track for second half of 2025 HOUSTON, April 1, 2025 — Moleculin Biotech, Inc., (Nasdaq: MBRX) (“Moleculin” or the “Company”), a late-stage pharmaceutical company with a broad portfolio of drug candidates targeting hard-to-treat cancers and viruses, today announced the first patient has

Regulation FD Disclosure, Financial Statements and Exhibits

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): April 1, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organizatio

As filed with the Securities and Exchange Commission on March 31, 2025.

Table of Contents As filed with the Securities and Exchange Commission on March 31, 2025.

Filing Fee Table

Exhibit 107 Calculation of Filing Fee Tables FORM S-1 (Form Type) Moleculin Biotech, Inc.

Regulation FD Disclosure, Financial Statements and Exhibits

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): March 24, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organizati

Investor Presentation dated March 2025

Exhibit 99.1

Moleculin Reports Full Year 2024 Financial Results and Provides Corporate Update –Continued progress in pivotal, adaptive Phase 3 clinical trial (the “MIRACLE” trial) toward first subject treated, on track to take place in the first quarter of 2025 –

Exhibit 99.1 Moleculin Reports Full Year 2024 Financial Results and Provides Corporate Update –Continued progress in pivotal, adaptive Phase 3 clinical trial (the “MIRACLE” trial) toward first subject treated, on track to take place in the first quarter of 2025 –Multiple subjects currently being screened in first MIRACLE site activated – Initial data readout of the Phase 3 MIRACLE trial expected i

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): March 24, 2025 MOLECULIN BIOTECH,

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): March 24, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organizati

Moleculin Biotech, Inc. Insider Trading Policy

Exhibit 19 Moleculin Biotech, Inc. INSIDER TRADING POLICY (adopted October 2, 2019) Purpose This Insider Trading Policy (the “Policy”) provides guidelines with respect to transactions in Moleculin Biotech, Inc. (the “Company”) securities and the handling of confidential information about the Company and the companies with which the Company does business. The Company’s board of directors has adopte

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 10-K ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2024 ☐ TRANSITION REPORT PURSUANT TO SECTI

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 10-K ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2024 or ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF For the transition period from to Commission File Number: 001-37758 Moleculin Bi

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. )

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): March 6, 2025 MOLECULIN BIOTECH,

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): March 6, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organizatio

Moleculin Announces Additional Annamycin Patent Allowances to Enhance Global Exclusivity New patents will extend coverage to major markets outside the U.S., expanding upon existing U.S. claims Affirms expectations for an initial data readout of the p

Exhibit 99.1 Moleculin Announces Additional Annamycin Patent Allowances to Enhance Global Exclusivity New patents will extend coverage to major markets outside the U.S., expanding upon existing U.S. claims Affirms expectations for an initial data readout of the phase 3 MIRACLE trial for the second half of 2025 HOUSTON, March 6, 2025 /PRNewswire/ - Moleculin Biotech, Inc., (Nasdaq: MBRX) (Moleculin

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. )

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.

Form of Securities Purchase Agreement (incorporated by reference to Exhibit 10.1 of the Form 8-K filed February 26, 2025)

Exhibit 10.1 SECURITIES PURCHASE AGREEMENT This Securities Purchase Agreement (this “Agreement”) is dated as of February 25, 2025, between Moleculin Biotech, Inc., a Delaware corporation (the “Company”), and each purchaser identified on the signature pages hereto (each, including its successors and assigns, a “Purchaser” and collectively the “Purchasers”). WHEREAS, subject to the terms and conditi

Moleculin Announces Pricing of $3.5 Million Registered Direct Offering and Concurrent Private Placement Priced At The Market Under Nasdaq Rules

Exhibit 99.1 Moleculin Announces Pricing of $3.5 Million Registered Direct Offering and Concurrent Private Placement Priced At The Market Under Nasdaq Rules HOUSTON, February 25, 2025 /PRNewswire/ - Moleculin Biotech, Inc., (Nasdaq: MBRX) (“Moleculin” or the “Company”), a late-stage pharmaceutical company with a broad portfolio of drug candidates targeting hard-to-treat tumors and viruses, today a

Placement Agency Agreement between Moleculin Biotech, Inc. and Roth Capital Partners, LLC (incorporated by reference to Exhibit 10.2 of the Form 8-K filed February 26, 2025)

Exhibit 10.2 PLACEMENT AGENCY AGREEMENT February 25, 2025 Roth Capital Partners, LLC 888 San Clemente Drive, Suite 400 Newport Beach, CA 92660 Ladies and Gentlemen: Introduction. Subject to the terms and conditions herein (this “Agreement”), Moleculin Biotech, Inc., a Delaware corporation (the “Company”), hereby agrees to sell up to an aggregate of $3,500,002 of registered and unregistered securit

Entry into a Material Definitive Agreement

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): February 25, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organiz

Form of Pre-Funded Warrant issued in February 2025 offering (incorporated by reference to Exhibit 4.1 of the Form 8-K filed February 26, 2025)

Exhibit 4.1 PREFUNDED COMMON STOCK PURCHASE WARRANT MOLECULIN BIOTECH, INC. Warrant Shares: [] Initial Exercise Date: February 26, 2025 THIS PRE-FUNDED COMMON STOCK PURCHASE WARRANT (the “Warrant”) certifies that, for value received, [] or its assigns (the “Holder”) is entitled, upon the terms and subject to the limitations on exercise and the conditions hereinafter set forth, at any time on or af

Form of Common Warrant issued in February 2025 offering (incorporated by reference to Exhibit 4.2 of the Form 8-K filed February 26, 2025)

Exhibit 4.2 NEITHER THIS SECURITY NOR THE SECURITIES FOR WHICH THIS SECURITY IS EXERCISABLE HAVE BEEN REGISTERED WITH THE SECURITIES AND EXCHANGE COMMISSION OR THE SECURITIES COMMISSION OF ANY STATE IN RELIANCE UPON AN EXEMPTION FROM REGISTRATION UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE “SECURITIES ACT”), AND, ACCORDINGLY, MAY NOT BE OFFERED OR SOLD EXCEPT PURSUANT TO AN EFFECTIVE REGISTR

1,150,000 Shares of Common Stock Pre-Funded Warrants to Purchase up to 2,121,029 Shares of Common Stock

Filed Pursuant to Rule 424(b)(5) Registration No. 333-280064 Prospectus Supplement (to Prospectus dated July 1, 2024) 1,150,000 Shares of Common Stock Pre-Funded Warrants to Purchase up to 2,121,029 Shares of Common Stock We are offering 1,150,000 shares of our common stock (the “Shares”) to institutional investors pursuant to this prospectus supplement and the accompanying prospectus, and a secur

Moleculin Biotech, Inc. 5300 Memorial Drive, Suite 950 Houston, TX 77007

Moleculin Biotech, Inc. 5300 Memorial Drive, Suite 950 Houston, TX 77007 February 24, 2025 VIA EDGAR U.S. Securities and Exchange Commission Division of Corporate Finance Washington, DC 20549 Re: Moleculin Biotech, Inc. Registration Statement on Form S-1 Registration No. 333-283820 (“Registration Statement”) Ladies and Gentlemen: Please be advised that the Company hereby requests withdrawal of the

Entry into a Material Definitive Agreement, Financial Statements and Exhibits

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): February 13, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organiz

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): February 13, 2025 MOLECULIN BIOTE

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): February 13, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organiz

Form of Inducement Warrant (incorporated by reference to Exhibit 4.1 of the Form 8-K filed February 13, 2025)

Exhibit 4.1 NEITHER THIS SECURITY NOR THE SECURITIES FOR WHICH THIS SECURITY IS EXERCISABLE HAVE BEEN REGISTERED WITH THE SECURITIES AND EXCHANGE COMMISSION OR THE SECURITIES COMMISSION OF ANY STATE IN RELIANCE UPON AN EXEMPTION FROM REGISTRATION UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE “SECURITIES ACT”), AND, ACCORDINGLY, MAY NOT BE OFFERED OR SOLD EXCEPT PURSUANT TO AN EFFECTIVE REGISTR

Form of Inducement Letter (incorporated by reference to Exhibit 10.1 of the Form 8-K filed February 13, 2025)

Exhibit 10.1 MOLECULIN BIOTECH, INC. February 13, 2025 Holder of Common Stock Purchase Warrants Re: Inducement Offer to Exercise Common Stock Purchase Warrants Dear Holder: Moleculin Biotech, Inc. (the “Company”) is pleased to offer to you (“Holder”, “you” or similar terminology) (i) the opportunity to receive new warrants to purchase shares of the Company’s common stock, par value $0.001 per shar

Moleculin Receives Positive FDA Guidance for Acceleration of its Registration-Enabling MIRACLE Trial for R/R Acute Myeloid Leukemia (AML) Company remains on track for first subject treated in pivotal, adaptive Phase 3 clinical trial (the “MIRACLE” tr

Exhibit 99.1 Moleculin Receives Positive FDA Guidance for Acceleration of its Registration-Enabling MIRACLE Trial for R/R Acute Myeloid Leukemia (AML) Company remains on track for first subject treated in pivotal, adaptive Phase 3 clinical trial (the “MIRACLE” trial) in the first quarter of 2025 HOUSTON, February 13, 2025 /PRNewswire/ - Moleculin Biotech, Inc., (Nasdaq: MBRX) (“Moleculin” or the “

Filing Fee Table

Exhibit 107 Calculation of Filing Fee Tables FORM S-1 (Form Type) Moleculin Biotech, Inc.

As filed with the Securities and Exchange Commission on February 11, 2025.

As filed with the Securities and Exchange Commission on February 11, 2025. Registration No. 333-283820 UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 AMENDMENT NO. 3 TO FORM S-1 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 Moleculin Biotech, Inc. (Exact name of registrant as specified in its charter) Delaware 2834 47-4671997 (State or other jurisdiction of (Prim

Moleculin Receives First Country Approval in Europe to Begin Recruiting for the MIRACLE Phase 3 R/R Acute Myeloid Leukemia (AML) Pivotal Trial First of many site approvals, including sites in the US, Europe and the Middle East, expected throughout Q1

Exhibit 99.1 Moleculin Receives First Country Approval in Europe to Begin Recruiting for the MIRACLE Phase 3 R/R Acute Myeloid Leukemia (AML) Pivotal Trial First of many site approvals, including sites in the US, Europe and the Middle East, expected throughout Q1-Q3 2025 Company remains on track for first subject treated in pivotal, adaptive Phase 3 clinical trial (the “MIRACLE” trial) in the firs

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): February 11, 2025 MOLECULIN BIOTE

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): February 11, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organiz

Form of Securities Purchase Agreement

Exhibit 10.34 SECURITIES PURCHASE AGREEMENT This Securities Purchase Agreement (this “Agreement”) is dated as of [], 2025, between Moleculin Biotech, Inc., a Delaware corporation (the “Company”), and each purchaser identified on the signature pages hereto (each, including its successors and assigns, a “Purchaser” and collectively the “Purchasers”). WHEREAS, subject to the terms and conditions set

Form of Series D Warrant

Exhibit 4.14 SERIES D COMMON STOCK PURCHASE WARRANT MOLECULIN BIOTECH, INC. Warrant Shares: [] Issue Date: [], 2025 THIS SERIES D COMMON STOCK PURCHASE WARRANT (the “Warrant”) certifies that, for value received, [] or its assigns (the “Holder”) is entitled, upon the terms and subject to the limitations on exercise and the conditions hereinafter set forth, at any time on or after the Stockholder Ap

Form of Series C Warrant

Exhibit 4.13 SERIES C COMMON STOCK PURCHASE WARRANT MOLECULIN BIOTECH, INC. Warrant Shares: [] Issue Date: [], 2025 THIS SERIES C COMMON STOCK PURCHASE WARRANT (the “Warrant”) certifies that, for value received, [] or its assigns (the “Holder”) is entitled, upon the terms and subject to the limitations on exercise and the conditions hereinafter set forth, at any time on or after the Stockholder Ap

As filed with the Securities and Exchange Commission on February 10, 2025.

As filed with the Securities and Exchange Commission on February 10, 2025. Registration No. 333-283820 UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 AMENDMENT NO. 2 TO FORM S-1 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 Moleculin Biotech, Inc. (Exact name of registrant as specified in its charter) Delaware 2834 47-4671997 (State or other jurisdiction of (Prim

Form of Securities Purchase Agreement

Exhibit 10.34 SECURITIES PURCHASE AGREEMENT This Securities Purchase Agreement (this “Agreement”) is dated as of [], 2025, between Moleculin Biotech, Inc., a Delaware corporation (the “Company”), and each purchaser identified on the signature pages hereto (each, including its successors and assigns, a “Purchaser” and collectively the “Purchasers”). WHEREAS, subject to the terms and conditions set

Filing Fee Table

Exhibit 107 Calculation of Filing Fee Tables FORM S-1 (Form Type) Moleculin Biotech, Inc.

Form of Waiver agreement dated February 9, 2025

Exhibit 10.35 WAIVER THIS WAIVER (this “Waiver”) is entered into by and among Moleculin Biotech, Inc., a Delaware corporation (the “Company”), and the purchaser signatory hereto (the “Purchaser”). Reference is hereby made to that certain Securities Purchase Agreement, dated as of August 15, 2024, by and between the Company and the Purchaser (the “Purchase Agreement”). Capitalized terms used herein

Form of PreFunded Warrant

Exhibit 4.15 PREFUNDED COMMON STOCK PURCHASE WARRANT MOLECULIN BIOTECH, INC. Warrant Shares: [] Initial Exercise Date: [], 2025 THIS PRE-FUNDED COMMON STOCK PURCHASE WARRANT (the “Warrant”) certifies that, for value received, [] or its assigns (the “Holder”) is entitled, upon the terms and subject to the limitations on exercise and the conditions hereinafter set forth, at any time on or after the

Entry into a Material Definitive Agreement

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): February 9, 2025 MOLECULIN BIOTECH, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37758 47-4671997 (State or Other Jurisdiction of Incorporation or Organiza

Placement Agency Agreement

Exhibit 1.1 PLACEMENT AGENCY AGREEMENT [], 2025 Roth Capital Partners, LLC 888 San Clemente Drive, Suite 400 Newport Beach, CA 92660 Ladies and Gentlemen: Introduction. Subject to the terms and conditions herein (this “Agreement”), Moleculin Biotech, Inc., a Delaware corporation (the “Company”), hereby agrees to sell up to an aggregate of $[] of registered securities of the Company, including, but