MBRX Reports First EU Patients Treated in Pivotal Annamycin+Ara-C Study

Rhea-AI Filing Summary

Moleculin Biotech announced the start of EU enrollment in its pivotal Phase 2B/3 trial of Annamycin combined with cytarabine (AnnAraC) for adults with relapsed or refractory acute myeloid leukemia (R/R AML). The company reported that the first two subjects in the European Union have been enrolled and one subject has been treated, marking initiation of EU participation in a multi-center, randomized, double-blind, placebo-controlled, adaptive-design study.

The press release is attached as an exhibit to the company's report and is being furnished rather than filed. The disclosure focuses on clinical development progress—specifically geographic expansion of patient enrollment in a late-stage trial evaluating Annamycin plus Ara-C for R/R AML.

Positive

• Initiation of EU enrollment in the pivotal Phase 2B/3 study expands geographic reach for patient recruitment
• First treated subject in the EU demonstrates site activation and initial dosing capability
• Study design is randomized, double-blind, placebo-controlled and adaptive, appropriate for assessing Annamycin plus Ara-C in R/R AML

Negative

• None.

Insights

Clinical Trials Analyst

TL;DR: EU enrollment and first treated subject indicate trial operational progress and regulatory/operational readiness in Europe.

This update shows the pivotal Phase 2B/3 study has moved beyond U.S.-only activity to include European sites, which can accelerate patient accrual and broaden regulatory relevance. The trial's randomized, double-blind, placebo-controlled, adaptive design is appropriate for assessing safety and efficacy in R/R AML, and initial EU treatment suggests site activation and supply chain processes functionally in place. The announcement is procedural and does not provide outcome data or enrollment pace beyond the first two EU subjects.

Equity Research Analyst

TL;DR: Early EU enrollment is a modest positive operational milestone but lacks financial or efficacy details.

The company reports operational progress by enrolling two EU subjects and treating one in its pivotal trial of AnnAraC. This is a constructive clinical development milestone because successful multinational enrollment can shorten timelines and support regulatory filings across jurisdictions. However, no efficacy, safety, enrollment rate, or timeline guidance was disclosed, so investor impact is limited until further data or broader enrollment metrics are provided.

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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 Organization)	(Commission File No.)	(I.R.S. Employer Identification No.)

5300 Memorial Drive, Suite 950, Houston, TX 77007

(Address of principal executive offices and zip code)

(713) 300-5160

(Registrant’s telephone number, including area code)

(Former name or former address, if changed from last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

☐	Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)
☐	Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)
☐	Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))
☐	Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-14(c))

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).          Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Securities registered pursuant to Section 12(b) of the Act:

Title of each class	Trading Symbol (s)	Name of each exchange on which registered
Common Stock, par value $.001 per share	MBRX	The NASDAQ Stock Market LLC

Item 7.01 Regulation FD Disclosure

On September 8, 2025, Moleculin Biotech, Inc. (the “Company”), issued a press release which announced that it has enrolled the first two subjects, and treated one, in the European Union (EU) in its pivotal Phase 2B/3, multi-center, randomized, double-blind, placebo-controlled, adaptive design study of Annamycin in combination with cytarabine (also known as “Ara-C” and for which the combination of Annamycin and Ara-C is referred to as “AnnAraC”) for the treatment of adult patients with acute myeloid leukemia (AML) who are refractory to or relapsed (R/R) after induction therapy (R/R AML).

A copy of the press release is attached to this report as Exhibit 99.1 and is incorporated by reference herein.

The information contained in Item 7.01 of this Current Report on Form 8-K, including Exhibit 99.1, is being furnished and shall not be “filed” for the purpose of the Securities Exchange Act of 1934, as amended (“Exchange Act”), nor shall it be incorporated by reference in any filing under the Exchange Act or the Securities Act of 1933, as amended (“Securities Act”), unless specifically identified therein as being incorporated by reference.

Item 9.01 Financial Statements and Exhibits.

(d) Exhibits.

Exhibit No. Description

99.1 Press Releasedated September 8, 2025

104 Cover page Interactive Data File (formatted as Inline XBRL document)

SIGNATURE

Pursuant to the requirements of the Securities and Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

	MOLECULIN BIOTECH, INC.
	Date:	September 8, 2025
	By:	/s/ Jonathan P. Foster
		Jonathan P. Foster

FAQ

What did Moleculin Biotech (MBRX) announce about its AnnAraC trial?

The company announced that it has enrolled the first two subjects in the European Union and treated one subject in its pivotal Phase 2B/3 randomized, double-blind, placebo-controlled, adaptive study of Annamycin combined with cytarabine for R/R AML.

Does the filing include clinical results or safety data for AnnAraC?

No. The disclosure reports enrollment and that one subject was treated in the EU but does not provide efficacy or safety results.

Is the press release attached to the 8-K filed or furnished?

The press release is attached as an exhibit and the company states the information is being furnished, not filed, under the Exchange Act.

What is the design of the pivotal trial mentioned by MBRX?

The trial is described as Phase 2B/3, multi-center, randomized, double-blind, placebo-controlled, with an adaptive design, evaluating Annamycin plus Ara-C (AnnAraC) in adults with relapsed or refractory AML.