Moleculin to present Annamycin data at AACR 2026

Rhea-AI Filing Summary

Moleculin Biotech, Inc. (MBRX) reported that new preclinical and translational data on its lead drug candidate Annamycin (naxtarubicin) will be presented at three scientific venues in September 2026, including the AACR Conference on Pancreatic Cancer: New Frontiers in Biology and Therapeutic Development.

The presentations examine how Annamycin’s lipophilic structure drives tissue-specific concentration, its activity as a topoisomerase II–targeting anthracycline, and preclinical antitumor effects in pancreatic cancer that may involve CD8+ T cell cytotoxicity. These data are intended to inform development of Annamycin alongside the ongoing MIRACLE pivotal Phase 2/3 trial in relapsed or refractory acute myeloid leukemia.

8-K Event Classification

2 items: 7.01, 9.01

2 items

Item 7.01 Regulation FD Disclosure Disclosure

Material non-public information disclosed under Regulation Fair Disclosure, often investor presentations or guidance.

Item 9.01 Financial Statements and Exhibits Exhibits

Financial statements, pro forma financial information, or exhibit attachments filed with this report.

Key Figures

AACR Conference dates: September 25–28, 2026 Polish Congress dates: September 9–12, 2026 AACR abstract publication time: September 25, 2026 at 1:00 p.m. ET +3 more

6 metrics

AACR Conference dates September 25–28, 2026 AACR Conference on Pancreatic Cancer in San Diego where Annamycin data will be presented

Polish Congress dates September 9–12, 2026 XIII Congress of the Polish Medical Diaspora featuring a presentation on Annamycin organotropism

AACR abstract publication time September 25, 2026 at 1:00 p.m. ET Time when AACR pancreatic cancer conference abstracts will be published in Cancer Research supplement

Interim AML dataset size 45 patients Interim results for Annamycin in R/R AML based on a small sample size (n=45)

MIRACLE trial phase Phase 2/3 Pivotal adaptive randomized double-blind placebo-controlled trial of AnnAraC in R/R AML

Company stage Phase 3 clinical stage Moleculin described as a Phase 3 clinical stage pharmaceutical company

Key Terms

organotropism, topoisomerase II, anthracycline, relapsed or refractory acute myeloid leukemia, +2 more

6 terms

organotropism medical

"Annamycin’s lipophilic structure drives it to concentrate in specific tissues"

Organotropism is the tendency of a disease process—most often cancer cells—to preferentially spread to and grow in particular organs or tissues rather than others. It describes biological patterns and mechanisms that make some organs more vulnerable to metastasis, similar to how certain plants thrive in specific soils. Investors encounter the term when assessing therapies, diagnostics, or biomarkers that target or predict where disease will recur, because organ-specific behavior affects clinical trial design, regulatory pathways, and market need.

topoisomerase II medical

"a potent topoisomerase II targeting agent"

An enzyme that helps manage the twisting and untangling of DNA by cutting and rejoining the double helix so cells can replicate and read their genes; think of it as a molecular pair of scissors and a hands-on mechanic that prevents DNA from getting into knots during cell division. It matters to investors because many cancer drugs and toxicology concerns target or affect topoisomerase II, so its role influences drug pipelines, clinical trial outcomes, patent value, and regulatory safety assessments.

anthracycline medical

"the enzyme target through which anthracyclines produce DNA damage"

An anthracycline is a type of powerful medicine used to treat cancer, working by killing or stopping the growth of cancer cells. Because these drugs can have significant side effects and influence healthcare costs, they are closely watched by investors, especially in the pharmaceutical and healthcare sectors. Their development and use can impact the financial performance of companies involved in cancer treatment.

relapsed or refractory acute myeloid leukemia medical

"for the treatment of relapsed or refractory acute myeloid leukemia"

A form of acute myeloid leukemia (AML) that either returns after an initial period of remission (relapsed) or fails to respond to standard treatments (refractory). It matters to investors because these cases represent a clear unmet medical need and drive demand for new drugs, clinical trials, and regulatory attention—similar to crops that either regrow after being cleared or resist the usual weed control, prompting investment in better solutions.

p-STAT3 medical

"capable of inhibiting p-STAT3 and other oncogenic transcription factors"

p-STAT3 is the activated form of a cellular signaling protein called STAT3, produced when the protein is chemically modified (phosphorylated) and can turn genes on or off. For investors, p-STAT3 is important because its presence or reduction in lab tests or clinical samples can indicate whether a drug is hitting its intended target, predict how aggressive a disease like cancer may be, and help gauge a therapy’s development and commercial potential—think of it as a molecular ‘on’ switch that shows whether a treatment is working.

antimetabolites medical

"a portfolio of antimetabolites, including WP1122"

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What did Moleculin Biotech (MBRX) announce in this Form 8-K?

Moleculin Biotech announced that new data on its lead candidate Annamycin (naxtarubicin) will be presented at three scientific venues in September 2026, including the AACR Conference on Pancreatic Cancer, focusing on tissue distribution, mechanism of action, and antitumor activity.

Which major conference will feature new Annamycin data from MBRX?

New Annamycin data will be presented at the AACR Conference on Pancreatic Cancer: New Frontiers in Biology and Therapeutic Development, held September 25–28, 2026 at the Hilton San Diego Bayfront in San Diego, California.

What scientific questions about Annamycin are being addressed in the September 2026 presentations?

The three presentations address where Annamycin concentrates in the body, how it kills cancer cells via topoisomerase II targeting, and whether its antitumor activity is partly mediated by CD8+ T cell cytotoxicity, informing development in hard-to-treat cancers.

What is Moleculin Biotech’s lead clinical program involving Annamycin?

Moleculin’s lead clinical program is the MIRACLE trial (MB-108), a pivotal, adaptive, multi-center, randomized, double-blind, placebo-controlled Phase 2/3 study evaluating AnnAraC (Annamycin plus cytarabine) in patients with relapsed or refractory acute myeloid leukemia (AML).

In which indications is Annamycin currently being developed by MBRX?

Annamycin is being developed for relapsed or refractory acute myeloid leukemia (AML) and for soft tissue sarcoma (STS) lung metastases. It is described as a highly efficacious and well-tolerated anthracycline designed to avoid multidrug resistance and lack common cardiotoxicity.

What other pipeline programs besides Annamycin does Moleculin Biotech (MBRX) mention?

Moleculin highlights WP1066, an Immune/Transcription Modulator targeting p-STAT3 and other oncogenic transcription factors, and a portfolio of antimetabolites including WP1122 for potential treatment of pathogenic viruses and certain cancer indications.

What forward-looking risks does Moleculin Biotech note regarding its development plans?

Moleculin notes that interim efficacy trends for Annamycin in R/R AML are based on a small sample size (n=45) and may not be predictive, and it states it will require significant additional financing, with no current commitments, to conduct its planned clinical trials.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Available on EDGAR 09/14/2026 - 04:00 PM Accepted by SEC EDGAR 09/14/2026 - 04:00 PM Learn about SEC filing dates

false 0001659617 0001659617 2026-09-14 2026-09-14

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 14, 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)	(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 14, 2026, Moleculin Biotech, Inc. (the “Company”), issued a press release which announced that new data on its lead drug candidate, Annamycin (naxtarubicin), will be presented at three scientific venues in September 2026, including the American Association for Cancer Research (AACR) Conference on Pancreatic Cancer: New Frontiers in Biology and Therapeutic Development.

The three presentations address distinct questions about Annamycin: where it concentrates in the body, how it kills cancer cells, and whether it can also enlist the immune system to do so. Together they inform the Company’s development of Annamycin in hard-to-treat cancers.

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 Release dated September 14, 2026
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 14, 2026
	By:	/s/ Jonathan P. Foster
		Jonathan P. Foster

Exhibit 99.1

Moleculin to Showcase New Annamycin Data at AACR Conference on

Pancreatic Cancer and Two European Scientific Meetings

Presentations examine where Annamycin concentrates in the body, how it

targets topoisomerase II, and its antitumor activity in pancreatic cancer

HOUSTON, September 14, 2026 /PRNewswire/ -- Moleculin Biotech, Inc. (Nasdaq: MBRX) (“Moleculin” or the “Company”) today announced that new data on its lead drug candidate, Annamycin (naxtarubicin), will be presented at three scientific venues in September 2026, including the American Association for Cancer Research (AACR) Conference on Pancreatic Cancer: New Frontiers in Biology and Therapeutic Development.

The three presentations address distinct questions about Annamycin: where it concentrates in the body, how it kills cancer cells, and whether it can also enlist the immune system to do so. Together they inform the Company’s development of Annamycin in hard-to-treat cancers.

Title: “Antitumor activity of ANNAMYCIN, a highly effective lipophilic DNA-binding drug: Impact of its organotropism”

Author/Presenter: Waldemar Priebe, PhD, UT MD Anderson Cancer Center

Congress: XIII Congress of the Polish Medical Diaspora

Dates: September 9–12, 2026

Location: Wroclaw, Poland

Annamycin’s lipophilic structure drives it to concentrate in specific tissues rather than distribute uniformly. Dr. Priebe’s presentation examines how that distribution relates to the antitumor activity observed across preclinical models, and what it may mean for treating tumors in those tissues.

Title: “Organotropism-guided exploration of anticancer properties of Annamycin (naxtarubicin), a potent topoisomerase II targeting agent”

Author/Presenter: Waldemar Priebe, PhD, UT MD Anderson Cancer Center

Event: Invited Lecture at the Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences

Date: September 14, 2026

Location: Wroclaw, Poland

This invited lecture extends the same line of inquiry to mechanism, examining how Annamycin’s tissue distribution interacts with its inhibition of topoisomerase II, the enzyme target through which anthracyclines produce DNA damage in dividing cells.

Title: “Turning cold pancreatic tumors hot: Antitumor activity of Annamycin is partially mediated by CD8+ T cell cytotoxicity”

Author/Presenter: Angela T. Alistar, MD, Morristown Medical Center, Atlantic Health System / Carol G. Simon Cancer Center

Congress: AACR Conference on Pancreatic Cancer: New Frontiers in Biology and Therapeutic Development

Dates: September 25–28, 2026

Location: Hilton San Diego Bayfront, San Diego, California

The abstract for this presentation remains under embargo until publication. Moleculin expects to report on the findings when the abstract is published, as described below.

Abstracts selected for presentation at the AACR Conference on Pancreatic Cancer will be published as a supplement to the September 15, 2026 issue of Cancer Research on September 25, 2026, at 1:00 p.m. ET.

“Annamycin’s ability to concentrate in specific tissues is one of the properties that most distinguishes it from currently prescribed anthracyclines, and it is the through-line across these presentations,” said Walter Klemp, Chairman, President and Chief Executive Officer of Moleculin. “Having this work presented by leading investigators, and accepted at an AACR conference, reflects the breadth of scientific interest in Annamycin beyond our lead indication in AML.”

These presentations run alongside Moleculin’s lead clinical program, the ongoing MIRACLE trial evaluating AnnAraC in patients with relapsed or refractory acute myeloid leukemia (AML). MIRACLE remains the Company’s primary development focus and the basis of its near-term milestones.

About Moleculin Biotech, Inc.

Moleculin Biotech, Inc. is a Phase 3 clinical stage pharmaceutical company advancing a pipeline of therapeutic candidates addressing hard-to-treat tumors and viruses. The Company’s lead program, Annamycin (also known as naxtarubicin), is a highly efficacious and well tolerated anthracycline designed to avoid multidrug resistance mechanisms and to lack the cardiotoxicity common with currently prescribed anthracyclines. Annamycin is currently in development for the treatment of relapsed or refractory acute myeloid leukemia (AML) and soft tissue sarcoma (STS) lung metastases.

The Company has begun the MIRACLE (Moleculin R/R AML AnnAraC Clinical Evaluation) Trial (MB-108), a pivotal, adaptive design, multi-center, randomized, double-blind, placebo-controlled Phase 2/3 trial evaluating Annamycin in combination with cytarabine, together referred to as AnnAraC (the combination of Annamycin and cytarabine, also referred to as “Ara-C”) for the treatment of relapsed or refractory acute myeloid leukemia. Following a successful Phase 1B/2 study (MB-106), with input from the FDA, the Company believes it has substantially de-risked the development pathway towards a potential approval for Annamycin for the treatment of AML. This study remains subject to appropriate future filings with potential additional feedback from the FDA and their foreign equivalents.

Additionally, the Company is developing WP1066, an Immune/Transcription Modulator capable of inhibiting p-STAT3 and other oncogenic transcription factors while also stimulating a natural immune response, targeting brain tumors, pancreatic and other cancers. Moleculin also has in its pipeline a portfolio of antimetabolites, including WP1122 for the potential treatment of pathogenic viruses, as well as certain cancer indications.

For more information about the Company, please visit www.moleculin.com and connect on X, LinkedIn and Facebook.

Forward-Looking Statements

Some of the statements in this release are forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, Section 21E of the Securities Exchange Act of 1934 and the Private Securities Litigation Reform Act of 1995, which involve risks and uncertainties. Forward-looking statements in this press release include, without limitation, the potential efficacy and safety of Annamycin and AnnAraC in R/R AML and the expectation that interim efficacy trends observed in a limited patient population will be confirmed in the full study population (the interim results presented are based on a small sample size (n=45), have not achieved statistical significance, and may not be predictive of results from the completed trial). Moleculin will require significant additional financing, for which the Company has no commitments, in order to conduct its clinical trials as described in this press release, and the milestones described in this press release assume the Company’s ability to secure such financing on a timely basis. Although Moleculin believes that the expectations reflected in such forward-looking statements are reasonable as of the date made, expectations may prove to have been materially different from the results expressed or implied by such forward-looking statements. The Company relies on the reports of its expert with regard to the absence of cardiotoxicity. The dataset referenced in this press release is subject to the review of the data from future subjects in its current and future clinical trials and long-term follow-up with subjects in its current trials. Moleculin has attempted to identify forward-looking statements by terminology including ‘believes,’ ‘estimates,’ ‘anticipates,’ ‘expects,’ ‘plans,’ ‘projects,’ ‘intends,’ ‘potential,’ ‘may,’ ‘could,’ ‘might,’ ‘will,’ ‘should,’ ‘approximately’ or other words that convey uncertainty of future events or outcomes to identify these forward-looking statements. These statements are only predictions and involve known and unknown risks, uncertainties, and other factors, including those discussed under Item 1A. “Risk Factors” in our most recently filed Form 10-K filed with the Securities and Exchange Commission (SEC) and updated from time to time in our Form 10-Q filings and in our other public filings with the SEC. Any forward-looking statements contained in this release speak only as of its date. We undertake no obligation to update any forward-looking statements contained in this release to reflect events or circumstances occurring after its date or to reflect the occurrence of unanticipated events.

Investor Contact:
JTC Team, LLC

Jenene Thomas

(908) 824-0775

MBRX@jtcir.com

Filing Exhibits & Attachments

5 documents

Press Releases

• EX-99.1 EXHIBIT 99.1 16.9 KB

Other Documents

• EX-101 XBRL TAXONOMY EXTENSION SCHEMA 3.5 KB
• EX-101 XBRL TAXONOMY EXTENSION DEFINITION LINKBASE 11.5 KB
• EX-101 XBRL TAXONOMY EXTENSION LABEL LINKBASE 15.5 KB
• EX-101 XBRL TAXONOMY EXTENSION PRESENTATION LINKBASE 11.7 KB